gsm document

GSM Basic Radio parameters

ZTE University

Objectives

At the end of this course, you will be able to:

Understand the meaning of various radio parameters

Grasp the setting of radio parameters

State the effect to radio network performance of various

kind of radio parameters

Content

Network identification parameters

System control parameters

Cell selection parameters

Network function parameters

Roles of identification parameters

Enable the MS to correctly identify the ID of the current

network

Enable the network to be real time informed of the correct

geographical location of the MS

Enable the MS to report correctly the adjacent cell

information during the conversation process

MCC LAC

Cell Global Identity

MNC

3 Digits 2-3 Digits Max 16 Bits

CI

Max 16 bits

LAI

CELL GLOBAL IDENTITY (CGI)

Cell Global Identity (CGI)

It is used for identifying individual cells within an LA

ROLES OF CGI

The CGI information is sent along the system broadcasting

information in every cell.

When the MS receives the system information, it will

extract the CGI information from it and determines whether

to camp on the cell according to the MCC and MNC

specified by the CGI.

It judges whether the current location area is changed,

then determines whether to take the location updating

process.

SETTING OF CGI

MCC（Mobile Country Code）:

consists of 3 decimal digits, and the value range is the decimal

000 ～ 999.

MNC（Mobile Network Code）:


00 ～ 999.

LAC（Location Area Code）:

The range is 1-65535.

CI（Cell Identity）:


NCC BCC

3 Bits 3 Bits

BSIC

NCC Network/ National Color Code Value Range: 0~7

BCC Base Station Color Code Value Range: 0~7

BASE STATION IDENTITY CODE (BSIC)

Base Station Identity Code (BSIC)

It enables MSs to distinguish between

neighboring base stations

NCC and BCC ROLES

NCC:

In the connection mode (during conversation), the MS

must measure the signals in the adjacent cells and

report the result to the network. As each measurement

report sent by the MS can only contain the contents of

six cells, so it is necessary to control the MS so as to

only report the information of cells factually related to

the cell concerned. The high 3 bits (i.e. NCC) in the

BSIC serve this purpose.

BCC:

The BCC is used to identify different BS using the same

BCCH in the same GSMPLMN.

C B A

F E D

BSIC CONFIGURATION PRINCIPLE

In general, it is required that Cells A, B, C, D, E and

F use different BSIC when they have same BCCH

frequency. When the BSIC resources are not

enough, the cells close to each other may take the

priority to use different BSIC.

ROLES OF BSIC

Inform the MS the TSC used by the common signaling

channel of the cell.

As the BSIC takes part in the decoding process of the

random access channel (RACH), it can be used to prevent

the BS from mis-decoding the RACH, sent by the MS to

an adjacent cell, as the access channel of this cell.

When the MS is in the connection mode (during

conversation), it must measure the BCCH level of adjacent

cells broadcasting by BCCH and report the results to the

BS. In the uplink measurement report, MS must show

BSIC of this carrier it has measured to every frequency

point.

BA LIST (BCCH ADJACENT LIST)

Adjacent cell BCCH table

At most 32 adjacent cell

Carried by BCCH when MS is idle, by SACCH

when MS is dedicated

The MS will first search carriers from this table

and if none is found it will turns to find any of 30

carriers with highest levels.

Content





RANDOM ACCESS

Random access is the process that messages

being transmitted on RACH when a MS turns

from “idle” to “dedicate” mode. The main

parameters includes:

MAXRETRANS

Tx_Integer

AC

MAX RETRANS

When starting the immediate assignment process

(e.g, when MS needs location updating,

originating calls or responding to paging calls), the

MS will transmit the "channel request" message

over the RACH to the network. As the RACH is an

ALOHA channel, in order to enhance the MS

access success rate, the network allows the MS to

transmit multiple channel request messages

before receiving the immediate assignment

message. The numbers of maximum

retransmission (MAX RETRANS) are determined

by the network.

MAX RETRANS

The MAX RETRANS is often set in the following ways:

For areas (suburbs or rural areas) where the cell radius is more

than 3km and the traffic is smaller, the MAX RETRANS can be

set 11 (i.e. the MAX RETRANS is 7).

For areas (not bustling city blocks) where the cell radius is less

than 3km and the traffic is moderate, the MAX RETRANS can be

set 10（i.e. the MAX RETRANS is 4).

For micro-cellular, it’s recommend that the MAX RETRANS be


For microcellular areas with very high traffic and cells with

apparent congestion, it’s recommend that the MAX RETRANS

be set 00（i.e. the MAX RETRANS is 1).

Transmission Distribution Timeslots

(Tx_integer)

The Tx_integer parameter is the interval in timeslots at which

the MS continuously sends multiple channel request messages.

The parameter S is an intermediate variable in the access

algorithm, and is to be determined by the Tx_integer parameter

and the combination mode of the CCCH and SDCCH

Format of Tx_Integer

MS starts the first channel request message : {0, 1, ...,

MAX (Tx_integer, 8)-1}

The number of timeslots between any two adjacent

channel request messages {S, S+1, ..., S+Tx_integer-1}

The Tx_integer is a decimal number, which can be 3~12,

14, 16, 20, 25, 32 and 50 (default). The values of the

parameter S are shown as below:

Tx_integer

CCH Combination Mode

CCCH Not Shared with SDCCH CCCH Shared with SDCCH

3, 8, 14, 50 55 41

4, 9, 16, 76 52

5, 10, 20, 109 58

6, 11, 25, 163 86

7, 12, 32, 217 115

ACCESS CONTROL AC

The access levels are distributed as follows:

C 0～C9: ordinary subscribers;

C11: used for PLMN management;

C12: used by the security department;

C13: public utilities （e.g. water, gas）;

C14: emergency service;

C15: PLMN staff.

SETTING OF AC

In the BS installation and commissioning process or in the

process of maintaining or testing some cells, the operator

can set C0～C9 as 0 to forcedly forbid the access of

ordinary subscribers so as to reduce the unnecessary

effects on the installation or maintenance work.

In some cells with very high traffic, the congestion will

occur in busy hours. For example, the RACH conflict

happens frequently, the AGCH is overloaded and the Abis

interface flow is overloaded. The network operator can set

proper access control parameters（C0～C15）to control

the traffic of some cells.

CCCH_CONF

CodingMeanings

CCCH message

blocks in one

BCCH

0 CCCH use one basic physical channel, not shared with SDCCH 9

1 CCCH use one basic physical channel, shares with SDCCH 3

10 CCCH use two basic physical channels, not shared with SDCCH 18

100 CCCH use three basic physical channels, not shared with SDCCH 27

110 CCCH use 4 basic physical channels, not shared with SDCCH 36

Others Reserved

CCCH_CONF

The CCCH can be one or more physical channels. The

CCCH and SDCCH can share the same physical channel.

The combination mode of the common control channel in a

cell is determined by the CCCH_CONF

CCCH_CONF

The CCCH_CONF is determined by the telecom

operation department according to the traffic

model of a cell.

If a cell has 1 TRX, we recommend that the CCCH

uses one basic physical channel and shares it with the

SDCCH

If a cell has 2 ~ 8 TRX, we recommend that the CCCH

uses one basic physical channel but does not share it

with the SDCCH.

AGBLK

Since the CCCH consists of the access grant

channel (AGCH) and paging channel (PCH), it is

necessary to set how many blocks of the CCCH

information blocks are reserved and dedicated to

the AGCH, the access grant reserve blocks

(AGBLK).

AGBLK is represented in decimal numerals, and

its value range is:

CCCH is not combined with SDCCH: 0～7.

CCCH is combined with SDCCH: 0～2.

AGBLK

SETTING AND IMPACT OF AGBLK

The AGBLK setting principle is: given that the AGCH is

not overloaded, try to reduce the parameter as much as

possible to shorten the time when the MS responds to

the paging and improve the quality of service of the

system.

The recommended value of AGBLK is usually 1 (when

the CCCH is combined with the SDCCH), 2 or 3 (when

the CCCH is not combined with the SDCCH).

BS-PA-MFRMS

According to the GSM specifications, every mobile

subscriber belongs to a paging group. the MS calculates

the paging group to which it belongs by its own IMSI.

In an actual network, the MS only "receives“ the contents

in the paging subchannel to which it belongs but ignores

the contents in other paging subchannels. (i.e. DRX

source).

The BS-PA-MFRMS refers to how many multi-frames are

used as a cycle of a paging subchannel. This parameter in

fact determines how many paging sub-channels are to be

divided from the paging channels of a cell.

BS-PA-MFRMS

Multiframes of the same

paging group that cycle

on the paging channel

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

BS-PA-MFRMS (2)

BS-PA-MFRMS is represented in decimal

numerals and its value range is 2～9, its unit is

multiframe （51 frames）, its default value is 2

PERIODIC UPDATING TIMER (T3212)

The frequency of periodic location update is

controlled via the network and the period length is

determined by the parameter T3212.

The T3212 is a decimal number, within the range

of 0~255, in the unit of six minutes (1/10 hours).

If the T3212 is set to 0, it means that the cell

needs no periodical location update.

NCCPERM

In the connection mode (during the conversation), the MS will report the measured signals of the adjacent cells to the BS, but each report may contain at most 6 adjacent cells.

Therefore, let the MS only report the information of the cells that may become the hand-over target cells.

The above functions can be fulfilled by limiting the MS to merely measure the cells whose NCC have been specified. The NCCPERM lists the NCCs of cells to be measured by the MS.

NCCPERM will affect handover

RADIO LINK TIMEOUT (RLT)

GSM specification stipulates that the MS must have a timer

(S), which is assigned with an initial value at the start of

the conversation, that is, the “downlink radio link timeout”

value.

Every time the MS fails to decode a correct SACCH

message when it should receive the SACCH, the S is

decreased by 1. On the contrary, every time the MS

receives a correct SACCH message, the S is increased by

2, but the S should not exceed the downlink radio link

timeout value. When the S reaches 0, the MS will report

the downlink radio link failure.

The radio link timeout is a decimal number, within the

range of 4 ~ 64, at the step of 4, defaulted to 16.

MBCR (1)

The parameter "multiband indication (MBCR)" is

used to notify the MS that it should report the

multiband adjacent cell contents.

The value is 0-3

MBCR (2)

0: Based on the signal strength of adjacent cells, the MS reports the

measurement results of 6 adjacent cells whose signals are the strongest,

whose NCC are known and allowed no matter in which band the adjacent

cells lie. The default value is “0”

1: The MS should report the measurement result of one adjacent cell in

each band (not including the band used by the current service area) in the

adjacent table, whose signal is the strongest and whose NCC is already

known and allowed.

MBCR (3)

2: The MS should report the measurement results of two adjacent cells

in each band (not including the band used by the current service area)

in the adjacent table, whose signals are the strongest and whose NCC

are already known and allowed.

3: The MS should report the measurement results of three adjacent cells




Application of MBCR

Content





CELL SELECTION C1

When the MS is turned on, it will try to contact a

public GSM PLMN, so the MS will select a proper

cell and extract from the cell the control channel

parameters and prerequisite system messages.

This selection process is called cell selection.

The quality of radio channels is an important factor

in cell selection. The GSM Specifications defines

the path loss rule C1. For the so-called proper cell,

C1>0 must be ensured.

C1 = RXLEV - RXLEV_ACCESS_MIN

- Max(MS_TXPWR_MAX_CCH - P ,0)

CELL SELECTION C1

where:

RXLEV_ACCESS_MIN is the minimum received level the

MS is allowed to access the network

MS_TXPWR_MAX_CCH is the maximum power level of

the control channel (when MS sending on RACH);

RXLEV is average received level;

P is the maximum TX power of MS;

MAX（X, Y）＝X; if X Y.

MAX（X, Y）＝Y; if Y X.

RxLevAccessMin

The RXLEV_ACCESS_MIN is a decimal number,

within the range of -110dBm ~ -47dBm

Default value is 0 (-110dBm).

RXLEV_ACCESS_MIN Meaning

-47 dBm > -48 dBm (level 63)

-46 dBm -49 ~ -48 dBm (level 62)

... ...

-108 dBm -109 ~ -108 dBm (level 2)

-109 dBm -110 ~ -109 dBm (level 1)

-110 dBm <-110 dBm (level 0)

Setting and Influence

For a cell with traffic overload, you can appropriately

increase the RXLEV_ACCESS_MIN

RXLEV_ACCESS_MIN value cannot be set to too high a

value. Otherwise, “blind areas” will be caused on the

borders of cells.

It is suggested that the RXLEV_ACCESS_MIN value

should not exceed -90 dBm.

CELL RESELECTION C2

Cell Reselection (C2) is a process when MS change its

service cell in idle mode.

When the MS selects a cell it will begin to measure the

signal levels of the BCCH TRX of its adjacent cells (at

most 6)

When given conditions are met, the MS will move from the

current cell into another one. This process is called cell

reselection.

When C2 Parameter Indicator (PI) indicates YES，the MS

will get parameters (CRO, TO and PT) , from BCCH, to be

used to calculate C2(channel quality criterion), which serves

as cell reselection norm. The equation is as follows:

Where T is a timer. When a cell is recorded by MS as one

of the six strongest cells, timer starts counting, otherwise, T

is reset to zero.

C2＝C1＋CRO－H（PT－T）×TO, when PT≠ 31

C2＝C1－CRO , when PT= 31

CELL RESELECTION C2

PARAMETER INDICATOR (PI)

PI is used to notify the MS whether to use C2 as the cell

reselect parameter and whether the parameters calculating

C2 exist.

PI consists of 1 bit. “1”means the MS should extract

parameters from the system message broadcasting in the

cell to calculate the C2 value, and use the C2 value as the

standard for cell reselect; “0” means the MS should use

parameter C1 as the standard for cell reselect (equivalent

to C2＝C1）.

CRO, PT AND TO

The cell reselection initiated by the radio channel quality regards C2

as the standard. C2 is a parameter based on C1 plus some artificial

offset parameters.

The artificial influence is to encourage the MS to take the priority in

accessing to some cells or prevent it from accessing to others. These

methods are often used to balance the traffic in the network.

In addition to C1, there are three other factors influencing C2, namely:

CELL_RESELECT_OFFSET (CRO), TEMPORARY_OFFSET (TO)

and PENALTY_TIME (PT).

Format of CRO, PT and TO

The CRO is a decimal number, in dB, within the range

of 0 ~ 63, meaning 0 ~ 126 dB, at the step of 2 dB.

The TO is a decimal number, in dB, within the range of

0 ~ 7, meaning 0 ~ 70 dB, at the step of 10 dB, where

70 means infinite.

The PT is a decimal number, in seconds, within the

range of 0 ~ 31, meaning 20 ~ 620 seconds for 0 ~ 30,

and at the step of 20 seconds. The value of 31 is

reserved to change the direction of effect that the CRO

works on the C2 parameter.

C2 TYPICAL APPLICATIONS

For cells where the traffic is very heavy or the

channel quality is very low. the PT may be set 31,

making TO invalid, so C2=C1-CRO.

For cells where the traffic is moderate, the

recommended value for CRO is zero and PT=31,

thus causing C2=C1, i. e. no artificial impact will

be imposed.


For cells with light traffic, it’s recommended that CRO

be ranged from 0 to 20dB. The greater the CRO, the

more possible the cells will be reselected ,and vice

versa. It’s also suggested that TO is equal or a little

higher than CRO. PT, whose main role is to avoid

frequent cell reselection by MS, is generally

recommended to be set at 20 seconds or 40 seconds.

CELL SELECTION HYSTERESIS (1)

When a MS reselects a cell, if the old cell and the target

cell are in different locations, then the MS must initiate a

location updating process after cell reselection.

Due to the fading features of the radio channel, the C2

values of two adjacent cells measured along their borders

will fluctuate greatly.

MS will frequently conduct the cell reselection, which will

not only increase the network signaling flow and lead to

low efficiency use of radio resources, but reduces the

access success rate of the system, as the MS cannot

respond to paging calls in the location updating process.


To minimize the influence of this issue, the GSM

specifications put forward a parameter called

ReselHysteresis,

The cell selection hysteresis is represented in

decimal numerals, its unit is dB, its range is 0～14,

its step length is 2dB, and its default value is 4.

CELL RESELECTION PRINCIPLE

If the MS calculates that the C2 value of an adjacent cell (Same location area) surpasses the C2 value of the serving cell and maintains for 5s or longer, the MS will start cell reselection .

If the MS detects a cell that is not in the same location area with the current cell, the calculated C2 value surpasses the sum of the C2 value of the current cell and the ReselHysteresis parameter and if it remains for 5s or longer, the MS will start the cell reselection .

The cell reselection caused by C2 should be originated at least at the interval of 15s.

In the system message broadcasting in each cell, there is a bit

information indicating whether to allow the MS to access to it, which

is called cell bar access (CBA). The parameter CBA is to indicate

whether the cell bar access is set in a cell.

The CBA bit is a parameter for the network operator to set. Usually

all the cells are allowed to be accessed by MS , so the bit is set

NO. However, in special cases, the telecom operator may want to

assign a certain cells for handover service only, then the bit can be

set YES.

CELL BAR ACCESS (CBA)

Area A

MS A

BTS B

BTS C


CELL BAR QUALIFY (CBQ)

In areas where the cells overlay with each

other and differ in capacity, traffic and

functions, the telecom operator often hopes

that the MS can have priority in selecting

some cells, that is, the setting of cell priority.

This function is set by way of the parameter

"Cell Bar Qualify" (CBQ).

C1 and C2 States with CBA and CBQ Configurations

CBQ CBACell Selection

Priority

Cell Reselection

State

No No Normal Normal

No Yes Barred Barred

Yes No Low Normal

Yes Yes Low Normal

CELL BAR QUALIFY (CBQ) 2

B A

EXAMPLE OF CBQ SETTING

For some reasons, the traffic of Cells A and B is apparently higher

than that of other adjacent cells. To balance the traffic in the whole

area, you can set the priority of Cells A and B as low, and set the

priority of the rest cells as normal so that the traffic in the shade

area will be absorbed by adjacent cells. It must be noted that the

result of this setting is that the actual coverage of Cell A and Cell B

is narrowed. However, this is different from reducing the transmitting

power of Cell A and Cell B, the latter may cause blind areas of the

network coverage and the reduction of communication quality.

Content





LIMITn

According to GSM Specification 05.08, the BTS must

measure the interference levels of the upward links of all

the free channels for the purpose of providing basis for

managing and allocating radio resources.

Moreover, the BTS should analyze its measured results,

divide the interference levels into 5 grades and report them

to the BSC. The division of the 5 interference grades (i.e.

the so-called interference bands) is set by the operator

through the man-machine interface. The parameter

"Interference band border(LIMITn)” determines the borders

of the 5 interference bands.

Value Range Specified dBm Level

0 <-110 dBm

1 -110 dBm ~ -109 dBm

2 -109 dBm ~ -108 dBm

…

61 -50 dBm ~ -49 dBm

62 -49 dBm ~ -48 dBm

Default: LIMIT1：4 LIMIT2：8 LIMIT3：15 LIMIT4：25

LIMITn

The division of the interference bands should be favorable in

describing the interference in the system. Generally the default values

are recommended. In the ordinary situations, the free channel

interference level is smaller, so the LIMIT1～4 value should be

smaller. When apparently large interference appears in the system,

you can properly increase the LIMIT1~4 values in order to know the

exact interference.

INTAVE

Due to the randomness of the radio channel

interference, the BTS must average the measured

uplink interference levels within the specified

period, and this average cycle is determined by

the INTAVE parameter.

This parameter is a decimal number, in SACCH

multi-frames, within the range of 1 ~ 31.

New Cause Indication (NECI)

The NECI is a decimal number, within the range of

0 ~ 1, with the meaning described as below:

When the NECI is 0, it means that the cell does not

support the access of half-rate services.

When the NECI is 1, it means that the cell supports the

access of half-rate services.

RE-ESTABLISHMENT ENABLE (RE)

For the drop calls caused by the radio link fault, the MS can start the call reestablishment process to resume the conversation, but the network is entitled to determine whether the call reestablishment is allowed or not. “0”=Yes, “1”=No.

In some special circumstances, the drop call may occur when the MS goes through a blind area during the conversation. If the call reestablishment is allowed, the mean drop call rate will be reduced. However, the call reestablishment process will occupy a longer period of time, most of the subscribers have hung up before the reestablishment process is over, as a result, the call reestablishment failed to achieve its purpose and wasted many radio resources. We recommend that the call reestablishment be not allowed in the network except for some individual cells.

GSM Coverage problem & Solution

ZTE university

Objectives

To know different kinds of coverage problem, their

causes and solutions.

Contents

Overview of Coverage Problem

Main Causes of Coverage Problem & Solutions

Procedures of Handling Coverage Problem

Typical Cases

Overview of coverage problem

Weak coverage

Over coverage

No-serving cell coverage

Too small coverage range will cause high

call drop rate and a large number of

customer complaints.

Too large coverage will result in frequent

handovers, and mutual interference as

well, if it’s rather serious, and network

indicators will also be affected.

When cell reselection parameters and

handover scenarios are similar, or there

are 2 or more cells with similar signal

strength ,Pingpong handover is easy to be

caused during calls.

Contents




Typical Cases

Main causes of weak coverage

Weak coverage

too small BTS power

too low antenna height

too small down-tilt

hardware problem

Obstruction of buildings

Main causes of over coverage

too high antenna height

inappropriate down-tilt

poor antenna performance

Causes of no-serving cell coverage unreasonable planning

of antenna parameters

inappropriate type of antenna

too large or too small

carrier transmission power

shrunk coverage caused

by equipment problem

influence of changes

in radio environment

unreasonable setting

of handover parameters

unreasonable setting of

cell reselection parameters

no-serving cell coverage

Contents




Typical Cases


Check setting of problem BTS’ radio parameters

Check if strong interference source exists

Check hardware

Check antenna system

Analyze the local geographical environment to

see if site location and type of site are appropriate

Contents




Typical Cases

Poor coverage at cold storage warehouse

【Problem description 】

Subscribers complained about the poor coverage around a cold storage warehouse of animal foodstuff; it was difficult to detect signal even when they were not far from the warehouse.

【Problem analysis】

According to subscriber’s complaint, we confirmed there was problem with coverage around the warehouse. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality data distribution were normal. Hardware operated normally, as shown in OMCR warning report.

Hardware engineers went to the site and checked the system of the BTS, tested power amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.

Through DT on site, network engineers found that the signal strength of the antenna main lobe was weak, while that of the side lobes was stronger, so they tentatively confirmed the problem was due to antenna fault.


【Problem handling】

After the antenna was replaced with a new one, the coverage improved

greatly, so did the speech quality.

Poor coverage of a BTS

【Problem description 】 Subscribers complained about weak signal strength around a Food

Bureau (near a BTS).

【Problem analysis 】 According to subscriber’s complaint, we confirmed there was

problem with the BTS' coverage. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality distribution were normal. Hardware operated normally, as shown in OMCR warning report.

Hardware engineers went to the site and checked the system of the BTS, tested amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.

Through DT on site, network optimization engineers found that the BTS’ coverage was in normal condition. While the Food Bureau, where subscribers complained about the signal, was 4km away from the BTS, and only indoor signal was weak (covered by Cell2).

Coverage shrinking after BTS starts operation


After Cell3 of a BTS started to operate, its coverage range was

found shrunk. On highway 3km away from the BTS, where the BTS

tower was visible, MS could not detect Cell3’s signal. MS could

receive signal when it’s around the BTS, and the signal level was

about -60dB.

【Problem analysis 】

We checked in radio resource management centre and found

Cell3’s static power class was set 2, which meant its static power

was reduced by 4dB, so we reset it to be 0. The next day, MS on

highway 3km away from the BTS could receive Cell3’s signal, and

its level was -60—70; and the signal level around the BTS was

strong, which was about -40dB.

we concluded that the cell’s coverage shrinking was caused by

wrong setting of static power control at OMCR.

High handover failure rate due to skip-zone

coverage 【Problem description 】

Configuration of a mountain site was S11, and the local network was single band GSM900. From indicator statistics of the past week, we found handover success rate of Cell2 under the BTS kept very low, which was around 80%, while TCH allocation failure rate was completely normal.

【Problem analysis 】 First, we could exclude the possibility of hardware problem and

interference, because there were no TCH assignment failures, which explained that MS could successfully occupy TCHs assigned to it by BSC; from DT analysis, we could see when signal level was above -90dbm, no call drops happened to MS, and speech quality was good, which could prove that no serious interference existed. Through further analysis, we found the target cell for handover was a bit far from Cell2; and probably adjacent cell relations were not set right during assignment planning, which resulted in isolated-island effect.

we could make area A and area B become adjacent cells to Cell2; while Cell2 coverage at A and B was already very weak, so Cell2 should not be adjacent cell to A and B .

After adjustment, handover success rate of Cell2 increased greatly, from 80% to 96%.


coverage

Cell2

Cell1

Questions for thinking

Which parameters can be adjusted to improve

coverage?

GSM/GPRS/EDGE Basic Principles

ZTE University

Objective


Learn GSM development history

Learn and master network structure of GSM system and

functions & principles of different portions

Learn and be familiar with GSM wireless channel and

protocol

Learn and be familiar with main service call process for

GSM

Content

Chap.1: GSM Overview

Chap.2: GSM Network Structure

Chap.3: Interfaces and Protocols

Chap.4: GSM Radio Channel

Chap.5: Basic Service and Signaling Process

Chap.6: Voice Processing and Key Radio

Technology

Chap.7: GPRS and EDGE

GSM Overview

This chapter mainly introduces some basic

information for GSM, including GSM development

history, supported service type, specification, and

system features.

GSM Basic Concepts

Services Supported by GSM System

GSM Specification

GSM Overview

This section introduces network structure of GSM

system and basic functions of various NEs.

GSM Area Division Concepts

GSM composition

Mobile Switching System (MSS)

Base Station Subsystem (BSS)

Operation & Maintenance Subsystem (OMS)

Mobile Station (MS)

GSM System Number


Relationship between Areas in GSM

GSM System Composition

IBM

IBM

BSS MSS

MS

MS

PSTN

Other

PLMN

Um

Interfac

e

A

Interf

ace

GSM composition


The MSS consists of such entities as the mobile

switching center (MSC), home location register

(HLR), visitor location register (VLR), equipment

identity register (EIR), authentication center (AUC)

and short message center (SMC).


BSS serves as a bridge between the NSS and MS.

It performs wireless channel management and

wireless transceiving. The BSS includes the Base

Station Controller (BSC) and Base Transceiver

Station (BTS).


The OMS consists of two parts: Operation &

Maintenance Center – System (OMC-S) and OMC-

Radio (OMC-R). The OMC-S serves the NSS, while

the OMC-R serves the BSS.

Mobile Station (MS)

The MS consists of mobile terminals and Subscriber

Identity Module (SIM) card.

GSM System Number

GSM system number contains:

Mobile Subscriber ISDN Number (MSISDN)

International Mobile Subscriber Identity (IMSI)

Mobile Subscriber Roaming Number (MSRN)

Handover Number

Temporary Mobile Subscriber Identification (TMSI)

Location Area Identification (LAI)

GERAN interfaces

This chapter introduces GERAN interfaces, User

plane/control plane protocol stack at PS and CS.

Interfaces

PS-Domain Protocol Stack

CS-Domain Protocol Stack

GSM interfaces

Interfaces

User plane protocol stack at PS domain


Control plane protocol stack at PS

domain


User plane protocol stack at CS domain


Control plane protocol stack at CS

domain


GSM Working Frequency Band

This section introduces GSM radio frame, channel

concept, division & function for different channels,

mapping combination mechanism between

channels.


Structure of GSM Radio Frame

Physical Channel and Logical Channel

System Messages


Currently, the GSM communication system works at

900MHz, extended 900MHz and 1800MHz.

1900MHz band is adopted in some countries.

1 hyper frame = 2048 super frames =2715648 TDMA frame

1 hyper frame = 1326 TDMA frame (6.12s)

(=51 (26 frames) multi-frames or 26 (51 frames) multi-frames

1 (26 frames) multi-frame = 26 TDMA frame (120ms) 1 (51 frames) multi-frame = 51 TDMA frame (3036/13 ms)

TDMA Frame

Hierarchical frame structure in GSM system


There are five layers for structure of GSM radio frame, that

is, timeslot, TDMA frame, multiframe, super frame, and

hyper frame.

GSM uses TDMA and FDMA technologies for physical

channel, as shown in the figure below.

Time

Frequency

Frequency

Time


System Messages

System message falls into 12 types: type1, 2, 2bis,

2ter, 3, 4, 5, 5bis, 5ter, 6, 7, 8.

Basic Service and Signaling Process

This section introduces GSM terminal start,

position register / update, service call and

handover service implementation and signaling

interaction process.

Mobile subscriber state

Location Update

Typical Call and Handover Process

Basic Signaling Process


The mobile subscriber has three states as follows:

MS starts, network does "Attach" marks on it

MS shutdowns, separated from network

MS Busy

Location Update at Same MSC Office

BSC

（2）

（1）

（3）（4）

MSC/VLR

LAI

1

LAI

2

M

S

M

S

Location update between different MSCs

（5）

（2）

（3）（1）

（4）

HLR

MSC/VLR1

MSC/VLR2

M

S

M

S

Location Update

Call process


Handover process


Location Update Process of MS

RLC

RLSD

DT1：CIPH MODE CMD

RF CH REL ACK

RF CH REL

REL IND UA

DISC DEACT SACCH

DR：CH REL CH REL

DT1：Clear COM

DT1：Clear CMD

DT1：CIPH MODE COM DI：CIPH MODE COM

CIPH MODE COM

CIPH MODE CMD ENCRY CMD

CC

CR：LOC UPD REQ EST IND

UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC

DTAP：LOC UPD ACCEPT


IMSI Detach Process

RF CH REL ACK

RF CH REL

REL IND UA

DISC DEACT SACCH

DR：CH REL CH REL

CREF

CR：IMSI DETACH EST IND

UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC


Mobile-Originated Call and Called

Party On-hook Process

RF CH REL ACK

RF CH REL

RLC

RLSD

CH REL

DISC

UA RF CH REL

RF CH REL ACK

REL IND

DEACT SACCH

DR：CH REL

EST IND

ASS COM DT1：ASS COM

DT1:ASS REQ

DT1：CIPH MODE CMD

CH ACT ACK

CH ACT

PHY CONT CONF

UA

SABM

PHY CONT REQ

DR：ASS CMD ASS CMD

DT1：Clear COM

DT1：Clear CMD


CIPH MODE COM


CC

CR：CM SERV REQ EST IND

UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC

DTAP:SETUP

DTAP:CALL PROC

DI：ASS COM

DTAP：Alerting

DTAP：Connect

DTAP：Connect ACK

数据流

DTAP：Disconnect

DTAP：Release

DTAP：Release COM

DTAP:CM SERV ACCP


Mobile-Terminated Call and Calling


UDT：PAG PAG CMD PAG REQ

RF CH REL ACK

RF CH REL

RLC

RLSD

CH REL

DISC

UA RF CH REL

RF CH REL ACK

REL IND

DEACT SACCH

DR：CH REL

EST IND


DT1:ASS REQ

DT1：CIPH MODE CMD

CH ACT ACK

CH ACT

PHY CONT CONF

UA

SABM

PHY CONT REQ


DT1：Clear COM

DT1：Clear CMD


CIPH MODE COM


CC

CR：PAG RES EST IND

UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

DTAP:SETUP

DTAP:CALL CONF

DI：ASS COM

DTAP：Alerting

DTAP：Connect

DTAP：Connect ACK

数据流

DTAP：Disconnect

DTAP：Release

DTAP：Release COM

BSC MSC BTS MS


Inter-cell Handover Process

DT1：HO PERF

HO CMD

CH ACT

MEAS REP

RF CH REL ACK

RF CH REL

DI：HO COM

EST IND

HO DET

CH ACT ACK

MS BTS1 BTS2 BSC MSC

MEAS RES

DR：HO CMD

HO ACCESS

PHY INFO

SABM

UA

HO COM


key radio enhanced technologies

This section describes basic voice processing for

GSM, and several key radio enhanced

technologies.

Voice Processing

Frequency multiplexing

Adaptive equalizing

Diversity Receiving

Discontinuous Transmission (DTX)

Power Control

Timing Advance

Frequency Hopping Technology

Voice Processing

Voice Processing in the GSM System


Frequency multiplexing is the core concept of the cellular

mobile radio system. In a frequency multiplexing system,

users at different geographical locations (different cells)

can use channels of the same frequency at the same time

(see the figure above).

Adaptive equalizing

Equalizer can do equalizing at frequency domain

and time domain. GSM uses time domain

equalizing, enabling the better performance in

whole system.

Diversity Receiving

Diversity reception technology is commonly used in GSM.

Diversity consists of different forms: Space diversity,

frequency diversity, time diversity and polarity diversity.


The DTX mode accomplishes two objectives: Lower the total

interference level in the air and save the transmitter power.

Speech Frame Transmission in DTX Mode

Power Control

Power control means to control the actual transmitting power (keep it

as low as possible) of MS or BS in radio propagation, so as to reduce

the power consumption of MS/BS and the interference of the entire

GSM network.

Power Control Process

Timing Advance

In the GSM, the MS requires three intervals between timeslots when

receiving or transmitting signals. See the figure below.

Uplink and Downlink Offset of TCH


Frequency hopping (FH) refers to hopping of the carrier frequency

within a wide frequency band according to a certain sequence.

Basic Structure of FH

section describes evolution of GSM

technologies

This section describes evolution of GSM

technologies: basic concept, network structure,

radio channel, and basic application of GPRS and

EDGE.

Definition and Feature

Inheritance and Evolution

GPRS Radio Channel

Radio Link and Media Access Control Flow

Terminal and Application


The General Packet Radio Service (GPRS) is the

packet data service introduced in GSM Phase2+.

The GPRS has the following features:

Seamless connection with IP network

High rate

Always online and flow charging

Mature technology


Enhanced Data Rate for GSM Evolution (EDGE) is a kind

of technology for transition of GSM to 3G.

The EDGE has the following features:

EDGE neither changes GSM or GPRS network structure nor

introduces new network element, but only upgrades the BSS.

EDGE does not change the GSM channel structure, multiframe

structure and coding structure.

EDGE supports two data transmission modes: packet service (non-

real time service) and circuit switching service (real time service).

EDGE adopts octal 8PSK modulation technology, supports 303%

of GMSK payload, and provides higher bit rate and spectral

efficiency.

Compared with GPRS, EDGE adopts new coding mode.

GPRS Radio Channel

This section introduces GPRS physical channel,

GPRS logic channel, mapping of logical channel

combination in the physical channel, and GPRS

channel coding.


This section introduces paging flow, TBF setup

flow, GPRS suspend/resume flow, and TBF

release flow.


The GPRS MSs fall into three categories: Type A,

B, and C.

GSM Handover Problems & Solutions

ZTE university

Objectives

To master different types of handover and their

signaling flows;

To master handover statistical signaling point and MR

tasks;

To know common handover problems and the handling

procedures.

Contents

Overview of handover

Flow of handover signaling

Handover statistics

Handover problem analysis

Aims of handovers

Why there are handovers?

To keep calls going on during movement;

To improve network service quality;

To decrease call drop rate;

To decrease congestion rate.

Handover classification

Inter-MSC

Inter-BSC

Intra-BSC

Intra-cell

Handover

classification

Contents



Handover statistics


Intra-cell handover

Air A

TCBTS

BSC

New Channel

Old Channel

Signaling flow of intra-cell handover

MS BTS BSC MSC

1、Measurement Report(SACCH)

2、Measurement Report

3、Channel Activation

4、Channel Activation Ack

5、Assigment Command （FACCH)

6、SABM(FACCH)

8、UA(FACCH)

7、Establish Indication

9、Assigment Complete(FACCH)

10、Receiver Ready(FACCH)11、HO Performed

12、RF Channel Release

13、RF Channel Release Ack

Air A

TCBTS

BTS

BSC

Old Cell / BTS New Cell / BTS

Inter-cell handover within one BSC

Signaling flow of inter-cell handover within one BSC

MS Old BTS BSC MSC

1、Measurement Report(SACCH)2、Measurement Report

5、HO Command

7、HO Access(FACCH)

12、UA(FACCH)

13、HO Complete(FACCH)

14、Receiver Ready(FACCH)

16、HO Performed17、RF Channel Release


New BTS



6、HO Command(FACCH)

8、HO Detect

9、Physical info(FACCH)

10、SABM(FACCH)


15、HO Complete

Air A

BTS

Old Cell / BTS

New Cell / BTS

BTS

BSC TC

BSC TC

VLRMSC

Inter-BSC handover

Signaling flow of inter-BSC handover

MS Old BTS Old BSC MSC

14、HO ommand

6、HO Command

13、UA(FACCH)

New BTS



10、HO Detect


12、SABM(FACCH)

New BSC

1、HO_REQ

2、HO_REQ

5、HO_REQ_ACK

7、HO Command8、HO Command



17、HO Command

Air A

BTS

Old Cell / BTS

New Cell / BTS

BTS

BSC TC

BSC TC

VLRMSC

VLRMSC

Inter-MSC handover

Basic signaling flow of Inter-MSC handover

MS/BSS-A

MSC-A MSC-B

MAP-Prep-Handover req. MAP-Allocate-Handover-Number req.

A-HO-REQUEST

A-HO-REQUIRED

BSS-B/MS

VLR-B

A-HO-REQUEST-ACK

MAP-Send-Handover-Report req.

MAP-Prep-Handover resp.

IAM

MAP-Send-Handover-Report resp.

ACM A-HO-COMMAND

A-HO-DETECT

A-HO-COMPLETE

MAP-Process-Access-Sig req.

MAP-Send-End-Signal req. A-CLR-CMD/COM

ANSWER

RELEASE End of call

MAP-Send-End-Signal resp.

MS/BSS-B

MSC-A MSC-B

MAP-Prep-Sub-Handover req. A-HO-REQUIRED

BSS-A/MS

VLR-B

A-HO-COMMAND MAP-Prep-Sub-Handover resp.

A-HO-REQUEST-ACK

A-HO-DETECT

A-HO-COMPLETE MAP-Send-End-Signal resp. A-CLR-CMD/COM

A-HO-REQUEST

Release

Signaling flow of inter-MSC back-handover

MSC-B

A-HO-REQUIRED

VLR-B

A-HO-COMMAND

MAP-Prep-Sub-Handover req.

A-HO-DETECT

A-HO-COMPLETE

MSC-A

MS/BSS

MSC-B’ VLR-B’

MAP-Prepare-Handover req.

MAP-Prepare-Handover resp.

MAP-Allocate-Handover-Number req.


IAM

MAP-Send-Handover-Rep. resp. (1)

MAP-Prep-Sub-Ho resp.

MAP-Process-Access-Signalling req.

MAP-Send-End-Signal req.

ACM

Answer

Release



Release

(end of call)

A-CLR-CMD/COM

Signaling flow of inter-MSC handover to a third MSC

Basic flow of handover signaling

Inter-cell handover

within BSC

There is no “HO-Request” message for intra-BSC handover; all

information is analyzed within BSC; Once a target cell in the

BSC fulfilling handover conditions is found, send “Channel

activation” message directly;

Inter-BSC handover

within MSC

BSC reports CGI and handover cause of original cell and target

cell to MSC through “HO-Request”;

After MSC finds target cell LAC, it sends “HO-Request” to the

BSC which the target cell belongs to;

Target BSC activates channel in target cell, and executes the

following flow.


Inter-MSC handover

MSC inquires “REMOTLAC sheet” (including LAC and

route address of adjacent MSC);

MSC sends （Prepare-HO） message to the target

MSC-B according to the route address;

According to the （Prepare-HO） message, target

MSC-B requests for Handover number from VLR-B,

then sends “HO-Request” message to BSC-B;

After the target BSC-B receives “HO-Request ACK”, it

sends （Prepare-HO ACK）message to the original

MSC, and executes the following flow.”

MSC participates

or not

CGI is carried

or not

Inter-

BSC

handover

Intra-

BSC

handover

MSC transmits “HO-REQ” message,

and CGI of original cell and target cell

is carried in the message;

As for inter-BSC handover, MSC

participates in it since “HO-Request”;

As for intra-BSC handover, “HO-

Performed” message is sent to MSC

only after the handover is

completed; MSC doesn’t participate

before that;

For intra-BSC handover, CGI isn’t

carried in any message, it’s handled

within BSC.

Main differences between intra-BSC handover

and inter-BSC handover

MS BTS BSC MSC

BCCH

frequency

point, BSIC

and level

values of

the six

adjacent

cells (with

strongest

level) and

serving cell;

UL MR

Process of MR

Confirmation of

adjacent cell CGI

Execution of

handover decision

Selection of

target cell

Channel activation

External cell?

HO

req

uest

Intra-MSC

handover

Target MSC Target BSC

BA2 sheet

List of cells

under one LAC

HO

req

uest

HO

req

uest

No

Yes

Flow of handover algorithm

Common timers at BSC

T3107

Suitable for: intra-cell handover

Start-up: BSC sends “assignment command”

Stop counting: when “assignment completed” or

“assignment failure” is received;

A1

BSCBTS:TRXMS

ASSIGNMENT COMMAND

CHANNEL ACTIVATE

A2

CHANNEL ACTIVATE ACK

SET T3107

T3107

Timeout


T3103

Suitable for: inter-cell handover

Start-up: BSC sends “handover command”

Stop counting: when “handover completed” or “handover failure” is

received;

A1

BSCOld BTS:MS

HANDOVER COMMAND

CHANNEL ACT

A2

CHANNEL ACT ACK

New BTS

HANDOVER COMMANDSET T3103

T3103

Timeout

Contents



Handover statistics


MR cycle

MR is sent to BTS in SACCH UL direction;

When MS is in SDCCH, MR cycle is 470ms/time;

When MS is in TCH, MR cycle is 480ms/time.

12TCH 12TCH 1SACCH 1 idle

480ms 26 multi-

frames of 4

TCHs

Indicator definition of handover success rate

KPI name Handover success rate

Indicator

definition

（ busy hour number of handover success times /busy hour total

number of handover request times）*100%

V6.20 (C900060098+C900060102+C900060120+C900060094

+C900060096)*100/(C900060097+C900060213+C9000

60214+C900060215+C900060099+C900060100+C900

060101+C900060216+C900060119+C900060093+C900

060095)

Signaling statistical point of handover success

C900060098 C900060102

C900060120

A

BTSBSC

HO_ COM

BSC-controlled inter-cell incoming handover success

A

BSCMSC BTS

HO_COM

HO_COM

MSC-controlled incoming handover success

A

BSC BTS

ASS_COM

ASS_CMD

Intra-cell handover success

C900060096

A

MSCBSC

CLEAR_CMD

No. of MSC-controlled outgoing handover success times


C900060094

MS

HO_CMD

BTS(Src)

CHL_ACT

BSC

HO_CMD

MEAS_RESMEAS_RES

SABM

UA

HO_COM

MSC

HO_COM

EST_IND

HO_PERFORM

HO_ACCESS

BTS(Target)

CHL_ACT_ACK

HO DETECT

Phy Info

A

BSC-controlled inter-cell outgoing handover success

Signaling statistical point of handover request

C900060097

A

BTSBSC

CHL_ACTIV_ACK

BSC-controlled inter-cell incoming handover execution

C900060213

C900060214

A

BTS( Target) BSC

CHANNEL ACT

CHANNEL ACT ACK

Forced release attempt

，Resource Available

Execution of forced release

A

BTS( Target) BSC

CHANNEL ACT

CHANNEL ACT ACK

Cell queuing


Execution of cell queuing

C900060215

A

BTS( Target) BSC

CHANNEL ACT

CHANNEL ACT ACK

Force handover attempt


Execution of force handover


C900060099 C900060100

C900060101

A

BSC

HO_REQ

MSC BTS

HO_REQ_ACK

CHL_ACTIV_ACK

CHL_ACTIV

MSC BSC-controlled incoming handover execution

A

BSC

HO_REQ

MSC BTS

HO_REQ_ACKCHL_ACTIV_ACK

CHL_ACTIV

Forced release attempt,

resource available


A

BSC

HO_REQ

MSC BTS


CHL_ACTIV

Cell queuing, resource available

Execution of queuing

A

BSCBTS

ASSIGN_ CMD

CHL_ ACTIV_ACK

Execution of intra-cell handover

C900060119


C900060216 C900060095

C900060093

BTS

A

MSC

HO_CMD

BSC

HO_CMD

No. of MSC-controlled outgoing handover execution times

A

BTS( Target) BSC

CHANNEL ACT

CHANNEL ACT ACK


，Resource available


MS

HO_CMD

BTS(Src)

CHL_ACT

A

BSC

HO_CMD

MEAS_RESMEAS_RES

SABM

UA

HO_COM

MSC

HO_COM

EST_IND

HO_PERFORM

HO_ACCESS

BTS(Target)

CHL_ACT_ACK

HO DETECT

Phy Info

No. of BSC-controlled inter-cell outgoing handover execution times

Handover-related measurement tasks

Handover

causes

measurement

Measure the frequency of MS handovers caused by various kinds of

reasons, so as to examine radio environment of a cell;

Common

handover

measurement

Measure the process of MS handover to inspect handover success or

failure and abnormal situations causing failures, so as to improve the

cell’s radio configuration and observe traffic dispersion, etc.;

Measurement

of adjacent

cell handover

Measure the number of times of incoming/outgoing handover

attempt/success/failure from/to certain cells, and number of times of

handover caused by different reasons, so as to get the handover

situations of the serving cell and its adjacent cells and to optimize their

radio configurations correspondingly;

Sub cell

statistical

measurement

Focus on traffic load of the second subcell.

Contents



Handover statistics


Analysis handover problems

Analysis of handover problems

Location method of handover problems

Common handover problems


Possible influences

Handover nonoccurrence

• Result in call drop;

Handover failure • Affect call quality and result in call

drop;

Frequent handover • Affect call quality, and increase

system load;

Handover hysteresis • Affect call quality and result in

call drop;

Discovery of handover problems

Meters at A interface

Traffic statistics analysis

Customer complaints

DT/CQT tests

TOPN analysis

Abnormal number of handover times

Call drop

Poor speech quality

Bad coverage

Handover problem Slow handover

Handover to best cell inhibited

No handover

Handover failure

Frequent handover

Flow of handover problem checking Too high TCH

handover failure rate

of a cell

Complete

Any antenna

problems?

Solve

antenna

problems

Eliminate

equipment

faults

Check &

eliminate

interference

Is radio

parameter setting

reasonable?

Interference

exists?

Any equipment

faults?

No

Yes

Adjust

parameters

Yes

Yes

Coverage

problem exists?

Improve

coverage

Yes

Location methods of handover problems

Analyze traffic statistics Conduct handover statistics measurement, identify

problem range: If just some cells fail to make handovers to the cell, check

handover data, check if co-channel and co-BSIC exist;

If the cell fails to take handovers from all other cells, check its data.

Check warnings: single board malfunction, transmission and clock malfunctions, etc.;

Check if radio parameters are set reasonably If co-channel or co-BSIC exist among adjacent cells;

If handover parameters are set reasonably;

If data configuration of external cells is correct.


Interference checking

DT analysis

Signaling analysis: Um interface、Abis interface 、 A interface;

Hardware checking: like DCU, transceiver, clock generator, RF

connection lines between boards;

Antenna system checking


Coverage & interference

Antenna system

BTS software & hardware

transmission

BSC software & hardware

A interface malfunction

Busy target cell

Connection & adaptation to equipment from different suppliers


Coverage:

Poor coverage: due to influence from forest, complex

landforms, houses, indoor coverage, etc.;

Isolated site: no adjacent cells around;

Skip-zone coverage: no adjacent cells available due to

isolated-island effect;

Interference:

It makes MS unable to access in UL, or DL signal

receiving problem will be resulted.

Handover nonoccurance due to isolated-

island effect

Adjacent cell N3

adjacent cell N2

adjacent cell N1

Non-adjacent

cell

Non-adjacent

cell

Non-adjacent

cell

Serving cell

Handover can’t happen due to lack of adjacent cells.

Skip-zone

coverage leads to

isolated island.

Antenna system problems

Too large VSWR

Reversed installation of antenna

Non-standard antenna installation

Unreasonable azimuth, down-tilt

Below-standard antenna insulation

Twisted cables, loosened connectors and wrong

connections;

BTS software/hardware

Problems about :

Single board

Clock generator malfunction

Internal communication cable malfunction

BTS software malfunction

Transmission and BSC problems

Transmission fault

Unstable transmission

Too high transmission error rate

BSC hardware/software malfunctions

Clock generator malfunction: unconformity among clocks in

different BTSs due to clock generator malfunction;

Problem about single board

Wrong data configuration

Unreasonable setting of handover threshold

CGI, BCCH and BSIC values in “external cell data sheet” do not

match up to those in the corresponding BSC;

Wrong BSC signaling point in “list of cell under a LAC” in MSC; co-

channel& co-BSIC adjacent cells exist.



Abnormal handover due to lack of link resource, abnormal calls;

Busy target cell


handover between equipment from different suppliers

Difference in signaling at interface A and interface E between ZTE

and other suppliers’ equipment, causing non-recognition or non-

support problem, including speech version, handover code and

addressing mode (CGI or LAI) etc., which will result in handover

failure.

Typical case 1- frequency interference

Problem description:

The data in performance report shows that Cell 1 under

a BTS suffers from low handover success rate.

Problem analysis

Examine the problem cell, discover that 2 cells under a

BTS co-channel and co-BSIC, and close to each other,

which results in low handover success rate in the cell.

Problem handling

After adjustment of frequency point, handover success

rate obviously increases, and number of handover times

reduces.


Changes of HO indicators before & after Frequency point adjustment

0

30

60

90

120

150

180

9-4 9-5 9-6 9-7 9-8 9-9 9-10 9-11

Number of HO Req./number of HO success

0%

20%

40%

60%

80%

100%

120%

HO success rate

切换请求总次数切换成功总次数切换成功率(%)No. of HOReq. HO success

rate

No. of HOsuccess

Typical case 2- clock malfunction

Problem description For a newly-commissioned BTS, handover nonoccurrence appears

during DT: the MS occupies a channel in cell A; during DT from cell A to cell B, cell B can’t be observed in the adjacent cell list, and it doesn’t start normal handovers.

Problem analysis It’s a common network problem that handover nonoccurrence

appears in many cells;

It’s a newly-commissioned BTS; handover parameters are as default in the system;

Check adjacent cells relation, no problem found;

Observe from test MS, find out that adjacent cell frequency appears in the adjacent cell, but BSIC can’t be decoded. Since adjacent cell is searched through BA2 table during a call, and

BA2 relies on BCCH and BSIC to confirm an adjacent cell, when the adjacent cell’s BSIC is unobtainable, BSC is unable to locate it, thus handover won’t be started.


Problem analysis

Process of MS decodeing on DL channel

decode FCCH decode SCH（SCH comprises MS frame

synchronous information and BSIC.

MS can show adjacent cell frequency point, but not BSIC. It’s

suspected that adjacent cell’s SCH information can’t be decoded

by MS due to clock or transmission fault.

Check clock and transmission

BTS adopts network clock

BSC traces superior clock

MSC traces superior GPS clock through long-distance satellite link

The long-distance satellite link is found unstable, which leads to

high error rate on the meter, and warning of clock deterioration

appears on MSC.


Problem handling

Decide that it’s handover problem

caused by poor clock quality.

Bring new GPS clock device and

adopt the local one, thoroughly

solve clock malfunction.

Problem of handover

nonoccurrence is solved.

Experience conclusion

If no high accuracy clock

available, clock in BTS can be

used; calibration of each BTS

must be made by using

frequency meter and LMT to

ensure that frequency deviation

meets precision requirement.

Typical case 3-HO parameter setting problem

Problem description

During DT at a BTS, we find slow handover problem is

common (>10S), which affects speech quality and even

causes call drops.

Problem: level of cell 2 is higher than that of cell 3 by

20dB, total handover time is 15s.


Problem analysis and handling

Slow handover seriously affects network quality. Make adjustment of handover parameters accordingly:

Change adjacent cell handover threshold to improve timeliness of handover trigger;

Adjust the whole network’s handover window to be 2, so as to accelerate handover speed;

Adjust the whole network’s handover preprocess to 2, so as to accelerate handover speed.

Parameter Before

adjustment

After adjustment

Level threshold

(HOMARGINRXLEV)

30 28

Quality threshold

(HOMARGINRXQUAL)

30 26

Result

Test after adjustment shows that handover time is reduced to 5s; the slow

handover problem is solved and speech quality is improve.


Please simply illustrate effects on handover due to

changing T3103、T3107.

Suggestions on parameter settings of handovers on

highway.

GSM Network Interference &

Solutions

ZTE university

Training goals

To know the classification of interference;

To master the analytical methods of interference

problem;

To master the flow of handling interference problem;

To know the analytical tool of interference problem;

To be able to handle common interference problems.

Contents

GSM Frequency Allocation

Phenomena & Classification of Interference

Flow of Handling Interference Problem

Analytical Methods of Interference Problem

Typical Cases


Frequenc

y band

UL

frequency

DL

frequency

Duplex

interval

Band

width

Carrier

frequenc

y interval

EGSM+G

SM900

880MHz

~915MHz

925MHz~9

60MHz 45MHz 35MHz 200kHz

DCS1800 1710MHz~1

785MHz

1805MHz~


Contents





Typical Cases

Phenomena of Interference

Call drop

Unable to

establish calls Metallic noise

On-and-off

speech

Poor

speech

quality

Phenomena

Classification of Interference

Internal interference

Internal interference refers to unreasonable frequency planning

and equipment hardware faults, which could lead to decrease in

network service quality.

External interference

External interference refers to unknown signal source out of the

network, whose existence could seriously disturb the network’s

signals and lead to decrease in service quality.

UL interference

DL interference

Internal Interference _Causes

Unreasonable frequency planning

Equipment faults

Skip-zone coverage

Internal

interference

Internal Interference

_due to unreasonable frequency planning

Unreasonable frequency planning :

Frequency and adjacent cell relation may be set

unreasonable in network planning because of planning

tools or human mistakes .

Interference will be reflected in too large DL_RxQuality,

MS unable to access into network, poor speech quality,

and call drop.



Check and confirm problem: Use planning tool to check if co-channel exists; co-

channel is easy to be detected if it does exist.

As for cells in boundary areas, we can block co-

channel cells in the network; meanwhile, make tracing

test with DT devices at areas with emergence of large

DL_RxQuality. If co-channel interference does exist, the

DL_RxQuality value shall become smaller after the

blocking of co-channel cells, thus we can adjust the

cell’s frequencies to eliminate the interference.

Internal Interference _due to skip-zone

coverage

Interference caused by skip-zone coverage

If the actual cell coverage greatly exceeds requirement,

interference will be increased.

Incorrect setting of engineering and network

parameters may lead to skip-zone coverage.


coverage

Unreasonable setting of engineering parameters:

Wrong antenna type, down-tilt and azimuth may result

in over large cell coverage, which exceeds actual

coverage need;

Unreasonable setting of network parameters:

Network parameters include: minimum access level,

BTS transmission power, MS max transmission power,

handover thresholds, etc..Improper setting of these

parameters will result in skip-zone coverage problem

and interference as well.

Internal Interference _ due to equipment

fault

Interference caused by equipment fault:

Radio fault of BTS is mainly caused by defective UL

unit parts.

External Interference

Definition: External interference refers to other interferences caused by

external factors, but not due to equipment fault or unreasonable

frequency planning.

Common external interferences:

due to wide-band repeater;

due to CDMA system (trailing signal);

due to signal jammer;

Characteristic:

It’s hard to detect this kind of interference without

specific devices.

Contents





Typical Cases


Confirm

interference

range

Check

frequency,

change

frequency

points

Complete

Poor speech

quality due

to

interference

Check and

change

TRX

Check

external

interference

Check

VSWR/antenna/divider/dupl

exer

One cell

Interference

exists

One

TRX

Interference

exists

Interference

exists

Any new sites? If thorough change

of frequency parameters taken

recently?

Several

cells

Contents





Typical Cases

Analytical Methods of Interference

Problem

Analytical

Methods of

Interference

Problem

Statistical

analysis of

network

performance

indicators

Analysis of

parameter

checking

Investigation

of hardware

fault

Drive Test

and Dialing

Test

External

interference

test

Analytical Methods of Interference Problem - Statistical analysis of network performance

indicators

Statistical analysis of network performance indicators

Statistics of interference band : When TCHs are in idle status, UL noise/interference is constantly being measured BTS, and the measurement result will be analyzed, and interference level will be sent to BSC in 6 levels. 。

Statistics of handover due to UL/DL interference : We can judge whether interference exists through statistics of handover caused by UL/DL interference.

Collection of UL/DL RQ samples during speeches : RxQual is an indicator to reflect speech quality, which is based on error rate and falls into 8 grades (0～7).


indicators

Corresponding relation between RxQual and Ber


- Analysis of parameter checking

Check

parameters

related to

transmitting

power

Check antenna

engineering

parameters

Check frequency

planning

parameters

Check

parameters

related to skip-

zone coverage

Parameter

checking


- Checking hardware fault

Checking hardware fault

OMCR warning analysis

Checking latent equipment fault


- Checking latent equipment fault

Block the two

input ways of

TRX, observe

UL

interference

band; if it’s 0,

it’s proved

that TRX

hasn’t

brought UL

interference.

Input the two

stimulations

of TRX

without

connecting

them to

power

amplifier,

observe UL

interference

band; if it’s

0, it means

external

interference

doesn’t exist.

If serious UL

interference exists

even though there

is no stimulation

imposed on

power amplifier,

disconnect rack

top feeder cables,

if the interference

disappears, we

can infer that the

problem is caused

by external

factors.

Disconnect the

rack top feeder

cables, and

observe UL

interference

band; if the

interference

isn’t fading at

all, then we can

conclude that

the problem is

with the divider

unit.


- Drive Test and Call Quality Test

Drive Test and Call Quality Test

Drive test can effectively detect the location

and degree of interference, which is

convenient for analyzing the cause of

interference.

In CQT, we can actually feel the speech

quality at areas being interfered, and we can

see call quality class on the test phone.



DT parameters:

C/I: co-channel carrier-to-interference ratio

RxQual 0 1 2 3 4 5 6 7

C/I[dB] 23 19 17 15 13 11 8 4

0

5

10

15

20

25

0 1 2 3 4 5 6 7

C/I[dB]


- Drive Test and Call Quality Test DT parameters:

SQI：SPEECH QUALITY INDEX is the comprehensive description of BER, FER and HANDOVER EVENT by TEMS.


- Test of external interference Confirm external interference with

SITEMASTER : Test of UL interference;

Connect the input port of frequency-sweep generator to the output port of divider to increase the degree of sensitivity, as shown in the figure.


- Test of external interference

Confirm external interference with SITEMASTER :

persistent strong level exists within the bandwidth of 20MHz, we can conclude that serious UL interference exists.



Confirm external interference with YBT250:

Make UL interference analysis of GSM 900M UL frequency band with frequency scanning meter-NetTek Analyzer(TEK company). The model we usually use is YBT250.

Connection method of YBT250:

One is to use its own test antenna ;

One is to obtain interference information through connection to

the output port of divider.



Connection method using YBT250 to test UL

interference:

Antenna

CDU

YBT 250

Feeder



Wave graph of UL interference tested by YBT250: This output is the average value of the test results of

one minute, which shows the frequency and strength of interference. Persistent observation is needed to confirm if the interference continues.


- Test of external interference Time scatter graph of UL interference tested by YBT250:

TEK frequency scanning meter features in three dimensional recording of time, frequency and signal.The vertical bold red lines in the graph represent the time duration, signal level strength and frequency .

vertical

axis=time

Colour

spectrum

=strengt

h

horizontal

axis=frequency

Contents





Typical Cases

Typical case 1: Problem description

Since March 2005, an operator has received a lot of

complaints about poor speech quality; sometimes calls

even couldn’t be setup; the caller could hear the

counterpart, but could not be heard.

Typical case 1: Problem analysis

At the

beginning we

thought it was

caused by

poor signal.

After on-site

test, we found

it wasn’t

coverage

problem.

When the level

tested by MS was

-85dbm, UL call

problem

occurred, which

was displayed as

on-and-off

speech, silence,

metallic noise

and current noise,

so we concluded

that the problem

was caused by

interference.

Performanc

e statistics

at OMCR

showed that

the rank of

idle channel

interference

band was

high.

Confirmed the

problem was

caused by

interference

Typical case 1: Problem handling process—

STEP1 Test UL interference with YBT250 connected to CDU. CDMA wave

form was strong when wave filter wasn’t used, the peak value reached

about -35dbm (average about -60dbm), which was close to GSM UL

wave band and could cause UL interference to GSM network.


STEP1 In the three dimensional graph of interference tested by YBT250, the

CDMA wave form was strong and the wave form of GSM background

noise on the right was high in a long period of time.


STEP2

Use CDMA wave filter to eliminate CDMA

interference.

Antenna Common

CDU

YBT 250

Feeder

CDMA wave

filter


STEP2 When CDMA wave filter was adopted, CDMA wave

form was obviously weakened, but it was still strong at

some certain point; the background noise in GSM

frequency band was also reduced.


STEP2

Because of CDMA wave filter, the UL interference in GSM

frequency band reduced greatly.


STEP3

With the aim to eliminate CDMA interference, adopt IRCDU

+CDMA wave filter.

Antenna CDMA wave

filter

YBT 250

IR CDU


STEP3 Adoption of IRCDU＋CDMA wave filter can effectively

filter CDMA waves to below -104dbm. This kind of filtering

effect can help completely avoid CDMA network interfering

GSM UL network.


STEP3 Adoption of IRCDU＋CDMA wave filter can eliminate

CDMA wave form to a great extent; during the test period,

CDMA interference was almost eliminated.

Typical case 1: Summary

The interference source was from CDMA system.

Through comparisons of tests above, we can see after

IRCDU+CDMA wave filter was used, call quality

obviously improved.


How is interference resulted from wrong setting of transmitting power-related parameters?

What is the flow of checking external interference?

SDCCH Assignment Analysis

& Solutions

Zte university

Contents

Overview

Analysis of signaling and counters related to

immediate assignment

Radio parameters

Instructions on checking of SDCCH assignment

failure

Typical cases on SDCCH assignment

Definition of SDCCH

SDCCH: the Standalone Dedicated Control Channel is used to transmit information like channel assignment, which falls into the following two types: SDCCH/8: the standalone dedicated control channel;

SDCCH/4: the SDCCH that is combined with CCCH.

In brief, the following processes shall be taken into consideration in the process of occupying SDCCH: Location update, periodical location update;

IMSI attach/detach

Call setup

SMS

Signaling flow of immediate assignment

Counters related to SDCCH assignment &

corresponding signaling messages V3

C900060242

Number of

SDCCH

assignment

success

Function:

After BSC sends out the immediate assignment message (IMM_ASS), this counter counts the number of successful MS accesses to the corresponding SDCCH.

Sampling:

when BSC receives the correct EST_IND or the message of assignment complete.

C900060243

Number of

SDCCH

assignment

failure

Function:

After BSC sends out the immediate assignment message (IMM_ASS), this counter counts the number of failed MS accesses to the allocated SDCCH.

Sampling:

when BSC receives the wrong EST_IND, or when T3101 expires.

SDCCH assignment success rate

KPI SDCCH assignment success rate

Definition Number of successful SDCCH assignments*100/(Number of successful

SDCCH assignments + Number of failed SDCCH assignments)

Counter

formula

V2 C11644*100%/( C11644+ C11645)

V3 V6.2 C900060242*100%/(C900060242+C900060243)

Difference: Random access success rate

Definition: Number of successful random accesses / Number of random access requests*100%

Number of random access requests Definition: MS applies for a channel in the idle mode.

Trigger point: it counts the message of CHANNEL REQUIRED received by BSC from MS. (A1)

Number of successful random accesses Definition: BSC successfully assigns a dedicated

channel for MS.

Trigger point: it counts the message of IMMEDLATE ASSIGNMENT sent from BSC to MS. (A2)

Contents

Overview



Radio parameters


failure


Analysis of Channel Request cause

Establishment Cause


Establishment Cause (continued)


Summary on Establishment Cause

Emergency call

Call re-establishment

Paging response（MTC）

Mobile originating call（MOC）

Location update （LOC）

Other access causes

One-step access

LMU service

MBMS service

Channel Required

Channel Required

Request Reference

RA（Random access reference）: it continues to use the Cause and

Random Reference in the Channel Request.

Byte 3 and 4 (T1, T2, T3): receive the frame number(42432) of the

burst pulse.

Channel Required

Access Delay

The estimated TA

Physical Context

including Rxlev_UL

Immediate Assignment Page Mode = same as before

Packet Response Type and Dedicated mode or TBF

Downlink assignment to mobile in Ready state: no meaning

TBF or dedicated mode: this message assigns a dedicated mode resource

PR Type: immediate assignment procedure for RR connection establishment

Channel Description

Type = SDCCH/8[0]

Timeslot Number: 1

Training Sequence Code: 0h

ARFCN: 104

Request Reference

Random Access:

Establish Cause: E0h = Originating call and TCH/F is needed, or originating call and the network does not set NECI bit to 1

Random Reference: 12h

N32: 13h; N51: 1Fh; N26: 0Dh

Timing Advance: 1 = 0,6 km

Mobile allocation

Establish Indication


T represents the sub-channel number.


Information on layer3:

CM SERVICE REQUEST

LOCATION UPDATING REQUEST

IMSI DETACH

PAGING RESPONSE

CM RE-ESTABLISHMENT REQUEST

NOTIFICATION RESPONSE

IMMEDIATE SETUP

RR INITIALISATION REQUEST


CM SERVICE REQUEST

Originate call

Emergency call (Access statistics show that emergency

call is not included in MOC )

SMS

Supplementary service

Group call establishment

Voice broadcast call

Access counters

Basic measurement

Counter Number Counter name

C900060001 Number of MTC access requests

C900060002 Number of MTC access successes

C900060131 Number of CM SERVICE REQ of MOC

C900060136 Number of MOC access requests

C900060137 Number of accesses due to paging response

C900060236 Number of MOC access successes

Access counters

Radio access measurement (I)

Counter Number Counter name

C901110001 Number of invalid access requests

C901110003 Number of successful process for MOC access

C901110006 Number of successful process for MTC access

C901110008 Number of call re-establishment access requests

C901110009 Number of successful process for call re-

establishment access

C901110010 Number of call re-establishment access success

C901110011 Number of emergency call access requests

C901110012 Number of successful process for emergency call

access

C901110013 Number of emergency call access success

C901110014 Number of LOC access requests

C901110015 Number of successful process for LOC access

C901110016 Number of LOC access success

C901110017 Number of access requests due to other causes

C901110018 Number of successful process for other causes’

access

C901110019 Number of access success of other causes

Access counters

Radio access measurement (II)

C901110020 Number of LMU Establishment access requests

C901110021 Number of successful process for LMU Establishment access

C901110022 Number of LMU Establishment access success

C901110023 Number of accesses due to location update

C901110024 Number of accesses due to CM SERVICE REQ

C901110026 Number of Emergency Call (CM SERVICE REQ) accesses

C901110027 Number of SMS (CM SERVICE REQ ) accesses

C901110028 Number of supplementary service (CM SERVICE REQ) accesses

C901110029 Number of accesses for LCS (CM SERVICE REQ ) accesses

C901110031 Number of accesses due to call re-establishment

C901110032 Number of accesses due to IMSI de-activation

C901110033 Number of accesses due to other causes

Contents

Overview



Radio parameters


failure


TxInteger

Before response to the previous “channel request”

is received, MS waits for a period of time at

random and sends the request again after

expiration. TxInteger is to decide the random

waiting time.

The interval (number of timeslots) from MS originating

the immediate assignment to the transmission of the

first “channel request” message is a random number

among { 0,1,…,Max（T,8）-1 }.

The interval (number of timeslots) between two

consecutive “channel request” is a random number

among {S,S+1,…,S+T-1}.

TxInteger

T(Number of

timeslots

Of TxInteger)

S

(CCCH is NOT

combined with

SDCCH)

S

(CCCH is

combined with

SDCCH)

3, 8, 14,50 55 41

4, 9, 16 76 52

5,10,20 109 58

6,11,25 163 86

7,12,32 217 115

TxInteger Number of

timeslots (T)

0 3

1 4

2 5

3 6

4 7

5 8

6 9

7 10

8 11

9 12

10 14

11 16

12 20

13 25

14 32

15 50

MaxRetrans

Because RACH is a ALOHA channel, in order to

improve MS access success rate, the network

allows MS to send several Channel Request

messages before it receives the Immediate Assign

message. The max number of Channel Requests

sent by MS is decided by MaxRetrans. MaxRetrans Max number of retransmission

0 1

1 2

2 4

3 7

TaAllowed

It represents the max TA allowed for access to the

cell.

It is used to filter out fake accesses.

RachAccessMin

New parameter for iBSC 6.20.100e

Used to filter out fake access, but not

recommended because it will affect the paging

performance.

Contents

Overview



Radio parameters

Instructions on checking of SDCCH

assignment failure


Explanation on common causes of SDCCH

assignment failure

MS frequently originates location update due to

poor downlink quality;

Improper setting of Tx-Integer;

High SD assignment failure rate due to LAPD

delay

Co-channel/co-BSIC interference

Uplink interference

Overshooting

Improper setting of Tx-Integer

The default of Tx-Integer is 14, which is also the

max value.

Usually, the one-way signaling transmission delay

at Abis interface is 60ms~100ms; there should be

a delay of about 240ms from MS originates

Channel Request till it receives Immediate Assign.

When the transmission link delay is long, while

TxInteger is set with a small value, it will result in

MS sending too many access requests. However,

MS only responds to the first Immediate Assign it

receives.


Flow chart of repeated assignment failure

Channel Request

Channel Required

M S

Channel Active

Channel Active Ack

Imm Assign(OK) Imm Assign Cmd

B T S

Channel Request(Re-Send）

TxInteger

Lapd

Delay

Channel Required

Channel Active

Channel Active Ack

Imm Assign Cmd Imm Assign(Fail)

MS change

to SDCCH

B S C

LAPD delay

Possible causes of LAPD delay Application of LAPD 1:4 multiplexing will lead to the situation that

several BCCH TRXs are multiplexed on one LAPD, which will cause heavy flow on the LAPD and hence delay.

Heavy flow on LAPD leads to delay. For example, improper LAC division will lead to large amount of paging and hence LAPD flow control.

Transmission equipment fault leads to loss of messages on LAPD or long LAPD delay. These phenomena are often accompanied with SDCCH assignment failure.

The transmission equipment’s own delay, such as the delay caused by satellite transmission at Abis interface.

Impact of PS service: PS service is more sensitive to network delay. Any LAPD delay will leads to re-transmission of PS service message, which increases the flow on LAPD and causes longer LAPD delay, then a malicious circle will be resulted.

Co-channel & co-BSIC

Two cells have same BCCH and same BSIC

The Channel Request sent by MS is received by two

cells and they assign SDCCH at the same time, but MS

can only accept one SDCCH, therefore, one of the two

cells will inevitably experience SDCCH assignment

failure.

For RACH coding, first add in 6bit color code, which is

obtained through taking mod2 of 6bit BSIC and 6bit

parity checking code. Therefore, co-BCCH and co-BSIC

may cause the BTS to incorrectly decode MS access

bursts to other sites, which will lead to SDCCH

assignment failure

Co-channel & co-BSIC

Two cells have same BSIC and the TCH Arfcn of one cell

is same as the BCCH Arfcn in the other cell.

The handover access request occurring on the TCH timeslot is

received as Channel Request by the other cell, which thereafter

performs assignment. This certainly leads to SDCCH assignment

failure.

It’s stipulated in protocols that the MS-started handover access

information and the random access request share the same format,

which is AB frame; the difference is that the handover access

information content (RA) in one handover started by MS is the

same, and the FN is in consecution.

Signaling related to this problem displays that the RA is the same,

TA is in consistence and FN in consecution. It’s confirmed that all

the large amount and consecutive Channel Requests are fake

accesses caused by handovers between co-channel cells.

Overshooting

If the coverage of cell is too large, the DL Rxqual at the cell margin will be poor. In this case, BTS can receive Channel Request sent by MS, but MS can not receive Immediate Assign sent by BTS, for BTS is more sensitive than MS,

If the coverage of cell is too large, the cell may share channel and BSIC with the cell which is far away.

Solution to overshooting: Adjust the engineering parameters of antenna to limit the cell

coverage.

TA_allowed can effectively decrease SDCCH assignment failures caused by overshooting. The side effect it brings is that the distant MS is not able to access network. Therefore, the threshold of TA_allowed shall be set a bit higher than the cell’s actual coverage. Besides, we should take into account the transmission distance of repeater when calculating the cell coverage range.

Uplink Interference --- Fake Access

BTS receiving sensitivity is -112dbm~-125dbm. If the random access signal

strength received by BTS is lower than BTS sensitivity, it usually is confirmed to

be interference. The interference can be decoded as random access, which is

called as fake access, and will definitely lead to SDCCH assignment failure.

Another feature of fake access is that TA is larger than that needed for the actual

coverage range.

Solution: TA_allowed

Note:

① RachAccessMin is not recommended to use

② As for TA-allowed, the corresponding name used by Nortel is RNDACCTIMADVTHRESHOLD,

whose description is as follows: adjust the parameter according to the cell’s actual coverage range.

Fake RACH request can be filtered out through setting proper threshold, therefore unnecessary

SDCCH assignment can be avoided. Test results prove that if TA-allowed is set 35Km for cells with

small coverage radius, fake RACH (the system demodulate the noise into RACH pulse by mistake)

accounts for almost 30% of all RACH requests. After rndAccTimAdvThreshold is changed to 2, fake

RACH is totally filtered out.

Frequent location update started by MS

If MS needs to make location update, while the

radio environment is poor, it will retransmit

Channel Request with the cause of location

update again and again, but it can never receive

Immediate Assign message.

The frequent location update will cause

fluctuations in SDCCH assignment indicators.

Frequent location update started by MS

Number of SDCCH

assignment

successes

Number of SDCCH

assignment failures

SDCCH assignment

success rate

Number of

MOC access

requests

Number of

MOC access

successes

Number of

MTC access

requests

Number of

MTC access

successes

Number of

SDCCH

occupation

attempts (for

assignment)

(MOC+MT

C)

assignment

success rate

(MOC+MT

C)

proportion

Reference

indicators

Troubleshooting instructions

Check TxInteger of the problem cell, along with LAPD delay observed from signaling.

Check whether the LAPD link of BCCH TRX in the problem cell is multiplexed with that of other cells.

Check whether any of the adjacent cells have same Arfcn and BSIC with the problem cell.

Check whether the value of counter “number of access attempts due to other causes” is big. If so, and the counter “number of access successes due to other causes” is zero, it is possible that “handover access” on other TCH TRXs are decoded as “channel request” by the problem cell.

Error Report with Channel Number 0x88 is available in the mplog file.

Troubleshooting instructions

Check SDCCH allocation KPIs and transmission

alarms.

If SDCCH &TCH assignment indicators are all bad,

the problem shall be related to radio environment.

Analyze signaling and check if Channel Request

with large TA, if so, fake access exist and

TA_allowed restriction can be used.

Contents

Overview



Radio parameters


failure


LAPD delay—Case 1: Large amount of

paging

Problem description: It’s found through performance

analysis that ZTE BSC3 has low SD assignment success

rate, which is only about 60% on late busy hours.

Problem analysis:

It’s observed that all the cells are experiencing high SD assignment

failure rate, so impact from radio parameters is excluded.

Indicators of other BSCs are normal; the SD assignment success

rate is low in only BSC3 and the Siemens BSC, both of which are

under MSC7.

The paging success rate in MSC7 is also very low; as the traffic

volume increases, the amount of paging increases as well.

LAPD delay—Case 1: Large amount of

paging

Adjustment measure:

Add one LAC under MSC7. After the adjustment, the SD assignment

success rate of BSC3 returns to normal, reaching above 95％.

50%

60%

70%

80%

90%

100%

0

20000

40000

60000

80000

100000

3月10日 3月11日 3月12日 3月13日 3月14日 3月15日

BSC3 SDCCH指配成功率对比

SDCCH指配成功次数 SDCCH指配失败次数 SD指配成功率

LAPD delay—Case 2: Satellite transmission

Problem description: 4BTSs are under BSC01, but

belong to different peripheral modules. The SD

assignment failure rate of the 4BTSs reaches as

high as 50%.

The time stamp shows that it takes an average of

0.58s to successfully activate a channel.

LAPD delay—Case 2: Satellite transmission

How to confirm that two Channel Requests are

started by the same call attempt?

They should have the same Establish Cause;

The same Access Delay;

The frame number interval corresponds to the setting of

TxInteger:

Calculation formula: FN＝T1*26*51+((T3-T2)mod 26)*51+T3

LAPD delay—Case 3: Transmission equipment fault

Problem description: Massive SDCCH assignment

failures occur in 3 cells of a site, accompanied

with lots of SDCCH allocation failures.

Problem analysis: SDCCH allocation failure

usually means transmission equipment fault.

After checking mpLog printing, there are lots of LAPD

Errors.

Also There are a lot of transmission alarms.


A cell’s ordinary SDCCH assignment failure rate remains at around 20% and hits 30% in busy hour. However, other KPIs(such as TCH assignment failure rate, handover success rate) are all good.

Problem analysis: After analyzing the cell’s signaling, we find there usually are Channel Request messages appearing in couples in the cell (with the same TA and cause). The Imm Assignment corresponding to the first Channel Request was successful, but the one corresponding to the second Channel Request failed.


Problem analysis:

Tx-Integer=12, which means “channel request”

retransmission interval is 109~128

FN of the first Channel Request is 964; that of the second

Channel Request is 1086; there is a difference of 124 frames.

It’s confirmed that the two Channel Requests are sent by the

same MS.

Solution: change Tx-Integer to be 14. After the

adjustment, the SDCCH assignment failure rate drops

to below 10%.

Access of interference signal—Case 1: TA

exceeding the actual coverage range

Problem description: the SDCCH assignment

success rate in a cell is very poor.

Time Alias

11644(Number of

SDCCH Assignment

Success)

11645(Number of

SDCCH Assignment

Failure)

2007-4-26 19:15 Cell A 191 15

2007-4-26 19:30 Cell A 190 24

2007-4-26 19:45 Cell A 177 33

2007-4-26 20:00 Cell A 192 26

Access of noisy signal—Case 1: TA exceeding the

actual range

Problem analysis: analyze ABIS signaling; the TA of

failed random access Immediate Assign failure is as

follows; the neighboring sites are near each other ,

with a distance less than 1 Km.

Serial No. TA Cause

Corresponding time stamp for sending Immediate Assign

1 35 MOC 06-08-55.375

2 36 MTC 06-08-55.562

3 35 MOC 06-08-55.984

4 34 MTC 06-08-56.578

5 32 MOC 06-09-11.640

6 30 MTC 06-09-24.546

7 27 MTC 06-09-38.031

8 27 MTC 06-09-38.578

9 27 MTC 06-09-39.109

10 0 MOC 06-09-57.171

11 24 MOC 06-09-57.828

12 10 MOC 06-11-15.406

13 2 MOC 06-12-12.781

14 0 MOC 06-12-52.671

15 0 MOC 06-12-53.218

16 1 LAC update 06-15-13.140

Access of noisy signal—Case 2: the Rxlev

lower than BTS sensitivity

Problem description: A cell’s SDCCH assignment

failure rate keeps high, but the TCH assignment

rate is acceptable.

SDCCH

assign

successful

number

SDCCH

assign

failure

number

SDCCH

assign

failure rate

TCH

Assignment

Success

Number

TCH assign

failure

number

TCH assign

failure rate

14479 4490 23.63 4678 122 2.54

Access of noisy signal—Case 2: the Rxlev

lower than BTS sensitivity

Problem analysis: The Physical Context carried by

Channel Required message reports the Rxlev of random

accesses, in which we find lots of Channel Request

messages whose Rxlev is -135dbm(0x87).

Co-BCCH & co-BSIC— Overshooting

Problem description: the SDCCH assignment failure rate

in many cells exceeds 25%.

Process procedure:

After all the hardware is changed, the problem still exists.

Through signaling trace we find that the co- BCCH/co-BSIC

signals received when TA=20 lead to SDCCH assignment failure.

Based on the above finding, re-plan the BSIC of more than 10

cells in the network. After the re-planning, coverage of the cells

returns to normal.

Solution:

Temporary solution: the CMM of cells with high reset failure rate

enables the clock to reset, which lead to synchronous malposition

of SDCCH timeslot.

Ultimate solution: to avoid co-channel/co-BSIC.

Co-Channel & co-BSIC—Handover

Problem description: a cell experiences a sudden

increase of SDCCH assignment failure rate in

busy hour; the TCH assignment indicators are

good.

Cell ID Pmdatatime SDCCH assign

failure rate

TCH assign

faliure rate

Cell A 19:00-20:00 15.85 0.68

Cell A 21:00-22:00 12.78 0.71

Cell A 20:00-21:00 11.27 1.36

Co-Channel & co-BSIC—Handover

Problem analysis: Through signaling trace, we find that there is a

large number of continuous random accesses; these Channel

Requests have the same RA, TA, and consecutive frame numbers.

Solution: After checking frequency planning, we find there are co-

channel & co-BSIC cells which are located 14km away from the BTS.

After re-planning of frequency, the problem disappears.

Weak coverage


The SDCCH assignment failure rate in a cell reaches

58% in busy hour, and TCH assignment failure rate

56%; handover success rate in only 20%.

Network performance statistics of fore-and-aft days

display that the TCH assignment failure rate, call drop

rate and handover failure rate have remained high.

UserLabel Handover

success rate(%)

SDCCH assign

failure rate

TCH assign

failure rate

Cell A 20 58.67 56.19

Weak coverage

Problem analysis: DT result shows that the problem cell not only experiences weak

coverage, but also overshooting and co-channel interference.

Signaling trace shows a large number of abnormal accesses of

consecutive Channel Requests with TA =63.

Consecutive LOC update request

Problem description: some sites at LAC boundaries and suburb

experience sudden increase of SDCCH assignment failure rate, which

moves in no certain pattern; while other indicators of the cell are quite

normal.

Problem analysis:

The basic measurement data shows that LOC access attempts and

failures count for a large proportion of the SDCCH assignment failures.

Consecutive LAC update access request

Problem analysis:

Signaling analysis shows that MS continuously starts Channel

Requests with cause of LAC update, which all end in failure.

GSM Radio network planning principle

ZTE University

Objectives


Describe the contents of information collection

State capacity planning

State coverage planning

Describe steps to notices of site survey

Master frequency planning and anti-interference

technology

Contents

Network planning information collection

Capacity Planning

Coverage Planning

Site layout & Survey

Coverage Emulation

Frequency Planning

Overview

Mobile service forecast

Subscriber forecast, distribution

Network equipment &

operation profile

MSC,BSC,BTS

Traffic statistic, quality

City planning

City type, map

Population

Economic development plan

Road and transport condition

Information Collection

Radio propagation survey

Geographic environment

Plantation

Network traffic distribution

Industrial, commercial, residential

area

Coverage and quality analysis

Coverage and quality (DT)

Statistic of A, Abis and OMCR

Interference analysis

Frequency allocation

Frequency scanning test

Analysis and survey

Frequency Other Traffic Model Capacity Coverage

Limited

frequency

Available

bandwidth

Frequency

resources

Coverage

KPI

Traffic

distributing

Coverage

size

Redundancy

and other

requirements

traffic

distributing

Traffic and

system

capacity

Data traffic

model

Voice traffic

model

Site

configuration

Propagation

environment

Electronic

map exists ?

Requirement analysis

Summary

Network planning information collecting

template

Inadequate

info

1. What is necessary information?

2. What is supplementary info?

？

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Basic concepts

Traffic volume

Traffic model

Erland

Call loss rate

Erlang B table

Erlang B table 2% 5%

1 0.020 0.0532 0.223 0.3813 0.602 0.8994 1.092 1.5255 1.657 2.2186 2.276 2.9607 2.935 3.7388 3.627 4.5439 4.345 5.37010 5.084 6.21611 5.842 7.07612 6.615 7.95013 7.402 8.83514 8.200 9.73015 9.010 10.63316 9.828 11.54417 10.656 12.46118 11.491 13.33519 12.333 14.31520 13.182 15.24921 14.036 16.18922 14.896 17.13223 15.761 18.08024 16.631 19.03025 17.505 19.985

Capacity Planning Procedures

Confirm subscriber

number

Site numbers and

configuration

Traffic distribution

ratio

Site distribution and

their latitude and

longitude

Reach target of

capacity planning

1 2 3 4 5

Network scale Capacity information

collection Site layout Traffic distribution

analysis

Site type and

number

Capacity Planning

Information collection

Network type: GSM900, DCS1800, dual-band network or WLL network？

System capacity requirement. No of subscriber and the traffic?

Traffic model of the voice service?

Equipment type: V2/V3? Model? Indoor or outdoor? DPCT applied in V3 or not?

Data service required? EDGE TRX? Data service penetration rate? Traffic model of data service?

Frequency resource range ? Is there frequency that are prohibited? Maximum site configuration ?

Forecast and investigation traffic density and define traffic distribution ratio.

Traffic density distribution

Traffic distribution analysis is to categorize the planning

area into areas of different service levels based on

forecast and survey of traffic density distribution

● how many phases and what is the ratio of

subscribers in each phase

● what is the planning area range and the

traffic distributing ratio in DU/MU/SU/RU.

● Provide existing sites and their

configuration and performance statistics

report data

扇面 1

41%

扇面 2

26%

扇面 3

15%

扇面 4

11%

扇面 5

7%

Service level by radio propagation environment

Area Topographic features

Dense

urban

Average height of surrounding buildings is more than 30 metres (over 10 storey)

and average distance between buildings is 10-20 metres. Usually the buildings

are crowded around the site with the height of 10-20 stories and the ambient

roads are not considerably wide.

urban

Average height of surrounding buildings is about 15-30 metres (5-9 storey) and

average distance between buildings is 10-20 metres. The buildings are evenly

distributed around the site. Mostly are below 9 stories and some are over 9

stories and the ambient roads are not considerably wide.

suburb



distributed around the site. Mostly are 3-4 stories and some are over 4 stories.

Roads around are wide.

rural Average height of surrounding buildings is below 10 metres. They are dispersed

and mainly are 1-2 storey high. There are spacious space between.

Service level by service distribution area

Area Distribution Features

Dense

urban

Traffic is heavy with high data service

rate, mainly for data service

development

Mean

urban

Traffic is relatively heavy and date

rate should be comparatively high.

Data service is required

Suburb Traffic is low and only low-speed

data service

Rural Traffic is quite low. Site is for

coverage purpose and data service

quality are not ensured.

Both radio propagation

environment and service

distribution factors should all

be taken into consideration.

Number of BTS sites-1

No. of BTS for capacity limited area

Maximum site type by frequency reuse pattern

Traffic per site by traffic model, Erlang-B table

Total number of BTS: Total traffic / single site

traffic


No. of BTS for coverage limited area

Total area / single site coverage (according to service

level)

Cell traffic = Cell coverage * traffic density

TCH number (Erlang-B table)

SDCCH number

TRX number

Start

Frequency resources

Capacity of each cell

Capacity per site

Site configuration & number

Frequency reuse pattern

Maximum Site type

Channel planning & data service

Erlang B table

Traffic model

Site configuration

Traffic & distribution

Network Scale Coverage Planning

Site type and number

No of SDCCH

Suppose SDCCH average process time is 3s，Location updating

process is 9s,BHCA=2

The traffic of SDCCH per subscriber is:

(3×2 + 9) / 3600 = 0.0042 Erlang

4SDCCH call loss=2% can support 1.092Erlang，

(1.092 / 0.0042 = 260sub) ×0.025 Erlang = 6.5Erlang

look up in Erlang-B，call loss=2%， 6.5Erlang need 12TCH(2TRX)

8SDCCH call loss=2% can support 3.627Erlang


Look up in Erlang-B，call loss=2%，21.6Erlang need 30

TCH(4TRX)

SDCCH configuration

TRX Channel SDCCH type SDCCH TCH TCH traffic

(GOS=2%)

1 8 SDCCH/8 1 6 2.28

2 16 SDCCH/8 8 14 8.2

3 24 2*SDCCH/8 16 21 14.9

4 32 2*SDCCH/8 16 29 21

5 40 2*SDCCH/8 16 37 28.3

6 48 2*SDCCH/8 16 45 35.6

7 56 3*SDCCH/8 24 52 43.1

8 64 3*SDCCH/8 24 60 49.6

9 72 3*SDCCH/8 24 68 57.2

10 80 4*SDCCH/8 32 75 64.9

LA planning

LA border

Paging capacity in LA

Paging capacity calculation

Influence by Short message

LA border

Avoid dense city with high traffic area

Avoid area with high mobility of subscribers

Cross the road slantwise

Consider traffic expansion

Paging capacity

IMSI/TMSI

Second paging（local paging、global paging）

Paging group：

(BS-AG-BLK-RES)

(BS_PA_MFRAMS)

Paging blocks/ per second =（9-AGB）/0.2354

Paging number / per paging block : B = 2 or 4


Paging numbers per second（P）

P =（9-AGB）/0.2354 * B

Suppose：

Average time of call：60s，ie:1/60Erl

Traffic of LA（T）

75％of MS response first paging，25％ of MS response

second paging

Paging congestion when 50% of maximum paging.

T*30%/(1/60)*1.25 = P*50% = 59.47*3600*50%

Influence by short message

3/per sub/per day

30% retransmit

Convergence factor:0.12

Subscriber in LA:100000

SM number in busy hour

100000×3×0.12×(1+30%)=46800

Consider holiday case: 8 times

Coverage

Planning

Capacity

Planning

Network

Scale

Summary

Capacity planning is

just an initial plan,

Add or reduce sites

based on radio

coverage planning

and analysis.


a repeated, gradual

process helping to

decide site number

and type.

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Coverage Planning flow

Set parameters Estimated

coverage radius of

each site

Allowable max path

loss

Information of site

distribution ,

latitude & longitude

of sites

Target of coverage

1 2 3 4 5

Network scale Network

parameter

Site layout &

coverage emulation Link budget Coverage radius

estimate

1

Network parameter

Confirm network parameters

Network category: GSM900,DCS1800, dual-band or WLL network?

Equipment type: V2 or V3? Model? Indoor or outdoor? Apply DPCT in V3? DPCT ratio?

Carrier Transmission power is 40W，60W，80W? Are data service required? EDGE carrier frequency？

Antenna model: antenna gains, horizontal and vertical beam width, antenna downtilt, polarization mode and electrical downtilt etc.

Antenna parameter: antenna available height, directional angle and downtilt.

Apply tower top amplifier?

Feeder type: 7/8 feeder or 15/8 feeder?

Maximum site configuration is? Are there special requirements toward configuration of combining and distribution unit?

What is KPI? What is level and area coverage rate? Which new technology will be adopted in V3 site, DDT? IRC? or FWDR?

2

Link Budget

Link budget

Definition:

Link budget is the calculation of loss and gains on one

communication link.

Target:

Maximum power of the site, avoid invalid downlink

coverage, reduce interference and system noise.

Allowable maximum indoor & outdoor path loss of uplink

and downlink Uplink Downlink

PA

Feeder loss Transmission

loss

Antenna gain Penetration loss

Site sensitivity

Fading margin

Body loss MS power

Link budget

Template

Losses

Margin reservation

Gains

Network Type & Equipment

Link Budget

Transmission power and reception

sensitivity of MS/BTS

CDU type

Fast fading margin

Slow fading margin

Interference margin

Site antenna gain

MS antenna gain

TMA gain

Path loss

Body loss

Vegetation

loss

Building penetration

loss

Feeder and

connector loss

Combiner and

splitter loss

Link budget

Link budget-Equipments

MS transmission power is showed as follows：

Power

class

GSM 900

Nominal

Maximum output

power

DCS 1800

Nominal

Maximum output

power

PCS 1900

Nominal

Maximum output

power

1 1 W (30 dBm) 1 W (30 dBm)

2 8 W (39 dBm) 0.25 W (24 dBm) 0.25 W (24 dBm)

3 5 W (37 dBm) 4 W (36 dBm) 2 W (33 dBm)

4 2 W (33 dBm)

5 0.8 W (29 dBm)

Link budget-Equipments Series Modulation Transmission power Reception

sensibility

Biggest site

BTS

V3

B8018 GMSK 60 W 47.78 dBm

-112 dBm S18/18/18 8PSK 31 W 45 dBm

B8112 GMSK 60 W 47.78 dBm

-112 dBm S12/12/12 8PSK 31 W 45 dBm

M8202 GMSK 30 W 44.78 dBm

-110 dBm S2/2/2 or O6 8PSK 20 W 43 dBm

BTS

V2

GMSK 40W 46 dBm -110 dBm S12/12/12

GMSK 80W 49 dBm -110 dBm S6/6/6

8PSK 30W 44.78 dBm -110 dBm S12/12/12

(EDGE) GMSK 60W 47.7 dBm -110 dBm S12/12/12

OB06 GMSK 40W 46 dBm -110 dBm S6/6/6

BS30 GMSK 40W 46 dBm -110 dBm S2/2/2

BS21 GMSK 40W 46 dBm -110 dBm S2/2/2

GMSK 80W 49 dBm -112 dBm S1/1/1

Link budget-Loss

Path loss

Body loss

Vehicle loss

Plantation loss

Building penetration loss

Feeder and connector

loss

Combining and

distributing unit loss

Link budget-Loss

Path loss

Radio wave loss caused by the transmission distance.

Body loss

Voice service, body loss 3 dB

Data service, 0dB.

Vehicle loss

Usually it is 8~10dB.

Link budget-Loss

Plantation loss

Inside the forest, the loss of 900MHz is 0.2dB/m; the

loss of 1800MHz is 0.3dB/m

Through forest or diffraction, the loss is 20dB/dec

Forest around the antenna and the antenna is lower

than the forest, around 10dB


Averagely it’s 10 – 20 dB，relying on building material

and thickness.

Link budget-Loss

Feeder cable loss

Type loss（dB/100m）

900M 1800/1900M

1/2 soft jumper 7.22 11.3

7/8 feeder 3.89 6.15

15/8 feeder 2.34 3.84

Link budget-Loss

Combiner & Splitter loss

Unit (900M) Insertion loss

CDUG 4.4dB

CEUG 3.5dB

CENG 5.3dB

CENG/2 5.3dB

ECDU 0.9-1.0dB

Unit(1800M) Insertion loss

CDUD 4.6dB

CEUD 3.6dB

CEND 5.5dB

CEND/2 5.5dB

ECDU 0.9-1.0dB

Link budget-Gain

BTS Antenna gain

Area Antenna gain

（dBi）

urban 15.5

suburb 15.5~17

rural 17~18

Express way or

long & narrow

valley

18~21

Hills and

highland

17~18

MS antenna gain

usually is 0

remark：special attention

should be paid to antenna gain

in MS in GSM WLL network

Antenna may be indoor,

outside door or on the roof.

So antenna gain and height

should be checked, which

will affect coverage greatly.

TMA gain

Link budget-Margin

Fast fading & deterioration storage

walking：2.0--5.0dB

fast moving：0dB

In GSM system, fast fading for voice and data service is

supposed to be 3dB.

Interference margin

The interference margin is generally supposed to be

3dB.

Link budget-Margin

Slow fading (shadow fading) margin

shadow fading is based on

standard deviation

margin coverage probability.

slow fading standard deviation is related to propagation

condition. In cities, it’s about 8~10 dB, while in suburbs

or rural areas，6～8dB.

Marginal coverage

probability(%)

70 75 80 85 90 95 98

Slow fading margin/dB 0.53σ 0.68σ 0.85σ 1.04σ 1.29σ 1.65σ 2.06σ

Link budget

Parameter Symbol

MS transmitting power A

Body loss B

Building loss C

MS reception sensibility D

MS antenna gain E

TMA gain F

Diversity gain G

Feeder loss H

Combiner/divider unit

loss

I

Fast fading margin J

Slow fading margin K

Noise margin L

Path loss indoor M=A-B-C-D+E+F+G-H-I-J-

K-L

Path loss outdoor N=M+C

Path loss difference

between uplink and

downlink is 3-5dB

3

Coverage

radius estimate

Estimate coverage radius

Maximum allowable path loss

Propagation model

Okumura-Hata model

Cost231-Hata model

Universal model

Cost231-Walfish-Ikegami model

Estimate

coverage

radius Max allowable loss Propagation model selection

4

Site layout &

coverage emulation

Site

distribution

Electronic map

Planning area size

Planning site number

Link budget

radius estimate

Distribution map

Distribution info

Latitude & longitude

Site layout & emulation

**** Input Output

Coverage &

emulation

**** Input Output

Electronic map

Planning map


Antenna height/direction angle

Antenna selection

Propagation model

Link budget

Existing network data

Site distribution map

Site coverage effect map

Height info map

Existing network coverage map

Coverage probability statistics table

4

Site layout &

coverage emulation

5

Network scale

Coverage

planning

Capacity

planning

Network

scale

Summary

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Site layout & survey procedure

coverage planning

+ capacity planning

=>

network scale

Distribute site on Mapinfo

or PLANET/EET E-map,

decide site theoretic

location, latitude &

longitude and other para of

sites

Based on theoretic location of

sites, make sites survey.

Confirm site location, site type &

location, antenna type, height,

direction angle, downtilt, CDU,

TTA and feeder etc.

Site survey

Optical measurement

Construction environment and natural

environment

Frequency spectrum measurement

Electromagnetism environment

Site investigate

Installation condition of antenna and equipment

Power and transmission supply

Preparation

Try to collect materials relating to the project

include：

Engineering files, background information,

existing network situation, map and

configuration list

Get tools ready

Digital cameral, GPS satellite receiver,

compass, ruler and PC.

Site layout & survey

When select site location, take the following aspects into

consideration

Previous Network condition

Population distribution and habits

City layout and distribution

Main streets and traffic volume

Natural environment such as Hills, lakes, rivers and coastline

Growing trend

Select high traffic area and

dense population area

population


Customer mobility trend

Principles of site selection

Surrounding environment

Signaling transmission

quality

Careful select high hills, radar,

radio station, gas station, forest

and power plant

Main principles to select sites

Site should be at the best place of regular mesh with deviation less than a quarter of the site radius.

Select existing facilities for cost saving and period reduction purpose on the premise that it doesn’t affect site distribution.

City edge or High-altitude hills(100 m or 300 m higher than city construction) in suburbs are not supposed to be sites, as first to control coverage scope, second to make construction and maintenance easier.

Newly-constructed sites should better be at place where transportation is convenient, commercial power supply available, safe environment and take less farmland.

Avoid construct sites near high power radio transmitter, radar station or other interference sources.

Better far from forest to avoid fast fading of received signaling.

Pay attention to the effect of signaling reflection and dispersion when in hills, steep slopes, dense lake area, mountainous region and high metallic buildings.

When in cities, utilize the height of the building to realize division of network hiberarchy

There are less sites in the initial stage of network construction, so good coverage of key areas should be guaranteed.

CDU

Feeder design

Antenna

Height, direction

Frequency range,

gain

Polarization

3dB beam width

Down tilt

To increase

receiving sensitivity of

BTS

TMA Feeder

Antenna and feeder

City site

Suburb

site

Antenna selection

Site in city

Select directional antenna with horizontal 3dB bandwidth of 60～65°

Select medium gain antenna of about 15dBi

Best to select antenna with electrical tiltdown of 3～6°

Recommend dual-polarized antenna

Site in suburb

Select direction antenna with horizontal 3dB bandwidth of 65°or

90°

Generally select medium or high gain antenna 15~18dBi

Preset downtilt or not based on actual condition

Select dual polarized or vertical polarized antenna

City site

Suburb

site

Antenna selection

Site in rural area

Select directional antenna of 90°、120°or omni antenna

High gain of directional antenna （16～18dBi）

Generally don’t select downtilt antenna. For high sites, zero filling

antenna is the best choice.

Vertical polarized antenna is recommended

Road site

Select narrow-beam, high gain directional antenna. 8-shape

antenna, omni antenna or deformation omni antenna based on

actual condition

Generally don’t select downtilt antenna because road site has

higher requirements to coverage distance.

Vertical polarized antenna is recommended.

Principle for antenna height

Antenna of different cell of the same site can be different

due to installation conveniences or cell planning

requirements.

For flat urban area, height of antenna is around 25m.

For suburbs, antenna height can be elevated to 40m.

Antenna can not be too high

Reduce coverage level near the antenna especially for omni

antenna

Easy cause problems affecting network quality like over coverage,

co-channel interference or adjacent-channel interference.

Principle for Antenna direction

Try to keep the direction of three-sector site same in urban area.

Antenna main lobe should direct at dense traffic area

Main lobe deviate from co-frequency cell to control interference effectively.

Overlapping depth of urban adjacent sectors should not exceed 10%.

Overlapping area for suburb and country adjacent cells shouldn’t be too deep and the antenna angle between two adjacent sector of the same site should not less than 90 degree

Antenna main lobe of dense city area should avoid pointing straight to the street in case over coverage because of wave guide effect.

Principles of antenna tiltdown

Antenna tiltdown is the basic method to enhance

frequency reuse ability.

Control coverage and reduce interference

Electrical or mechanical tiltdown.

Mechanical tiltdown angle < 15°

Space diversity distance

Distance between two receiving antenna is 12～18λwhen

antenna is diversified by space.

Generally distance between diversity antenna is 0.11 times

of the antenna height.

To achieve the same effect, distance of vertical diversity

must be 5 to 6 times of horizontal diversity.

To reduce the interaction of the two antennas, horizontal

distance of diversity antenna should be over 3 m

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Coverage

emulation

**** Input Output

Coverage emulation

Electronic map

Planning area

Latitude & longitude of sites

Antenna height & direction angel

Antenna model

Link budget


Sites distribution map


Height information map

Existing network

coverage map

Coverage rate statistics

table

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

GSM working frequency band

GSM900

Uplink 890 915 MHz

Downlink 935 960 MHz

duplex separation is 45MHz，carrier frequency separation is 200KHz

EGSM

Uplink 880 890 MHz


duplex separation is 45MHz， carrier frequency separation is 200KHz

DCS1800

Uplink 1710 1785 MHz



P-GSM900

Fl (n) = 890 + 0.2n MHz

Fu (n) = Fl(n) + 45 MHz 1 n 124

n stands for ARFCN

E-GSM900

Fl (n) = 890 + 0.2(n-1024) 975 n 1023

Fu (n) = Fl(n) + 45 MHz 0 n 124

DCS1800

Fl (n) = 1710.2 + 0.2(n-512) MHz

Fu (n) = Fl(n) + 95 MHz 512 n 885

ARFCN

Basic Concept

Frequency Reuse Cluster

Frequency Reuse Factor

Frequency Reuse Distance

C/I and C/A

Frequency reuse distance

The following equation is used to estimate frequency reuse

distance:

D = 3 N * R

D —— frequency reuse distance

R —— cell radius

N - frequency reuse factor.

Definition of C/I and C/A

Co-channel Interference C/I：

C/I refers to the interference of another cell using the

same frequency to the current cell. The ratio of carrier

to interference is called C/I.

GSM specification regulates that C/I >9dB. In

implementing, it requires C/I>12dB.

Adjacent channel interference C/A

C/A refers to interference of adjacent channel to the

current channel. The ratio is called C/A. The GSM

specification regulates that C/A>-9dB.

Calculation of C/I

Where, Pown_cell is the signal strength of current

cell; Pi_BCCH is BCCH signal strength of interfering

cell i measured by MS.


Ordinary (group) frequency reuse: ―43‖, ―33‖ and

more close ―26‖ and ―13‖.

MRP: different layers adopt different frequency reuse

patterns.

Concentric: the Underlay and Overlay adopt different

frequency reuse patterns respectively.

―4×3‖multiplex

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

A3

B1

B3B2

A1

A2

A3

B1

A1

A2A3

D2B1

D1

D3

A1

A2

A1

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

dB

dBI

C

18

)2.7(2)8(

2log10

)(

44

4

18dB>12dB

―3×3‖multiplex

A3

C2B1

C1

C3

B3B2

A1

A2

A3

C2B1

C1

C3

B3B2

A1

A2A3

C2B1

C1

C3

B3B2

A1

A2

A3 C1

A1

A2

A3

C2B1

C1

C3

B3B2

A1

A2

A3 C1

A1

A2

A3

B1

B3B2

A1

A2

dB

dBI

C

3.13

)57.5(2)7(2

2log10

)(

44

4

13.3dB>12dB

Multiple reuse pattern（MRP）

BCCH can use 43 or higher reuse coefficient to

ensure the BCCH quality, while the TCH will use

relatively dense reuse mode.

The division of BCCH and TCH layer frequency

bands reduces the planning workload and

facilitate the layered planning.

Reserve some frequency for the micro cell.

Simplify the configuration of BA tables

The relative independence of the BCCH and TCH

layers facilitates the maintenance and expansion

of each layer.

TCH2

FRF=6

BCCH FRF=12

TCH1 FRF=9

For Microcell

FRF: Frequency reuse factor

Bandwidth=6 MHz

MRP

BCCH

“4×3”

TCH1

“3×3”

TCH2

“2×3”

TCH3

“1×3”

MRP

Application of MRP

China mobile: MRP

Frequency bandwidth: 7.2MHz

AFN:（60～95），

Divide 36 carrier frequencies into 4 group as per

12/9/8/7

Channel

type

Logic channel

TCH1 service

channel

TCH2 service

channel

TC3 service

channel

Channel

number

60 61 62 63 64 65

66 67 68 69 70 71

72 73 74 75 76 77

78 79 80

81 82 83 84 85

86 87 88

89 90 91 92

93 94 95

60

64

68

62

66

7063

67

7161

65

69

72

75

78

73

76

7972

75

787477

80

89

91

93

9092

94 9092

9489

91

93

8183

85

8284

8682

84

8183

85

86

1) BCCH 4 3 2) TCH1 3 3

4) TCH3 2 3 3) TCH2 2 3

Application of MRP

2 2

2

2

2

2

2 2 2

2

2 2

2

2

2

Concentric

Concentric

The coverage of Underlay is the same as that of ordinary cell, while the Overlay use small transmitting power and thus has smaller coverage.

The frequency reuse factor of overlay differs from that of underlay.

The BCCH and SDCCH are used by Underlay, in which the call will be set up.

The absorbing of traffic by overlay is limited by traffic lay-out and coverage. It will increase the capacity by 10-30%

A brand new switching algorithm should be added.

2 2

2

2 2

2 2

2

2

2 2

2

2

2

2

2

2

2 2

2

2

2

2

2

Intelligent Concentric IUO

IUO

IUO has the same network structure as ordinary

concentric, consisting of Overlay and Underlay.

Underlay and Overlay of IUO both use the same

transmitting power.

IUO adopts a handover algorithm based on C/I

It’s very suitable for absorbing traffic inside building.

Comparison

Concentric

Overlay smaller

transmitting power

Handover based on

power or TA

Overlay coverage is

fixed but not reasonable

Absorb limited traffic

Handover algorithm is

easy

IUO

U/O same transmitting

power

Handover algorithm

based on C/I

Overlay coverage is

fixed and reasonable

Absorb more traffic


complicated

TCH frequency plan

The frequency in same site can not be reused

In same cell, the frequency distance between BCCH and

TCH is at least 400khz

Frequency can not be reused in its directly adjacent sites if

it is not 1*3 pattern

Opposite cells should not be co-channel and avoid

adjacent channel.

High hill in the middle shall not be considered as

neighboring sites while broad water in the middle shall be

considered as neighboring sites.

Avoid to set same BSIC to BCCH with same frequency

Neighboring cell configuration

Centered on the cell, at most two-circle cells

can be neighbor cells

Neighboring cells shall not be more than 32.

Modify unreasonable neighboring cells

according to drive test.

Handover cells shall not be co-channel.

Avoid one way neighboring relationships

Avoid two neighboring cells with the same

BCCH and the same BSIC.

Attention

Reserve frequencies for

Test in propagation,

Replacement frequency in the interference test,

Micro cell frequency in hot spot area.

Generally BCCH should use higher continuous frequencies.

Allocate frequency based on different areas.

Allocate frequency for sites in different areas such as urban,

suburb and rural.

Focus should be put on cities to avoid interference.

Make planning in urban areas before suburbs and rural areas.

Divide urban area into small areas if there are many sites.

Check manually after frequency assignment via automatic frequency

planning.

Anti-interference technique

Dynamic power control (DPC)

Discontinuous transmit (DTX)

Diversity receiving

FH technique


DTX encodes the voice at 13kbit/s during the

voice active period, it encodes the comfort

noise at 500bit/s during the quiet period.

DTX

DTX contributes very little to the interference

during the quiet period, its power can be

regarded as 0 (inactive state).

Suppose the DTX active factor is , then the

gain

log10log10log10)(/ IC

ICdBIC


From the figure we

can see that, in the

dynamic power

control situation,

when the interfering

MS is only at the

cell borders, the

BTS can work with

the maximum

transmitting power.

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A3

A1

A2

DPC

Obviously, the interfering MS location is a

probability. This case is especially apparent in

the frequency hopping situation.

Suppose the DPC factor is p:

pdBICIC

pIC log10log10log10)(/

（FH）

Frequency hopping is to avoid external

interference. In other words, it is to prevent or

greatly reduce co-channel interference and

frequency selective fading effect by

converting frequencies to an extent that

interference cannot catch up with.

Baseband and synthesized FH

Parameters

HSN（hopping sequence number）

MAIO（mobile assignment index offset）

Function

The advantage of the frequency hopping is the so-called

effect of Frequency Diversity and Interference Diversity.

The former actually expands the network coverage scope,

and the latter improves the network capacity.

Frequency diversity gain

For static or slow moving MS. about 6.5dB gain can

be provided.

For fast moving MS, the difference of two connected

bursts of a channel in time and place is enough to

make them uncorrelated to Rayleigh change, that is,

they are almost not subject to the influence of the

same fading, at this time, the slow hopping can

provide very little frequency diversity gain.

Gain=1.5-6.5dB

Interference diversity gain

In consideration of the above figure, suppose the MS talks by

using fk at the time t, in this case, the probability of the

interfered cell fk is

m

n

I

C

pI

CdBIC log10log10log10)(/ 增益

nmCCp mn

mn //1

1

Hopping set MA：},...,,,{ 321 nffff

,

TRX number：m (mn)

Interfering cell

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A3

A1

A2

C/I= 9.43 dB

1*3＋FH＋DPC＋DTX

Most densely reuse pattern

BCCH (4*3)

Combined with anti-

interference technology

Generally，only use 50%

of the whole available

frequency


Compared to ―4×3‖ multiplex, the ―1×3‖ multiplex brings about the

interference degradation:

CIR 4×3- CIR 1×3 =18 - 9.43 8.57 dB

―1×3‖hopping, 50% frequency load brings about the interference

diversity gain:

10log10(2/1) = 3dB

Suppose the frequency hopping length is 12 frequency points, then

the frequency diversity gain is about 2dB

Suppose the DTX active factor is 0.5, then the gain is:

-10log10(0.5) = 3dB

Suppose the DPC factor is 0.9, then the gain is: -10log10(0.9)

=0.5dB

The total gain is: 3+2+3+0.5=8.5dB

GSM Network Planning

Info

collection

Capacity

planning

Coverage

planning

Site layout

& survey Frequency

planning

Radio

network

Summary

Case Analysis on GSM Network

Optimization

ZTE University

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

Severe call drops caused by the illegal user

Description:

2 cells of the GSM network in XX had severe call drop

problem, about dozens of times per hour in the day time.

Cause Analysis & Procedure:

According to the 24-hour performance statistics, most

of the call drops were in the daytime. While very few of

them were in the night. So the engineer suspected that

the problem was related with the user behavior.


After tracing the Abis interface signaling, we found:

(1) The handsets with the call drop problem all used the same IMEI number.

(2) The dialed numbers were all the emergency number: 112;

(3) The call drop occurred about 10s after the call was connected. After the call drop, the user continued to dial 112 again and again.

Based on the above factors, we made the judgment: the call drop was caused by the user himself. For example, the workers in a factrory were testing the batteries of handsets, and they took out the battery while the call was still going on. So if we disable the emergency call function of the cell, the user will try to use another operator's network. After the operation, we found that the amount of call drops in the cell was greatly reduced. After we enabled the emergency call function later, the call drop problem didn't occur any more, becasue the user selected another operator's network.


Summary:

By analyzing the Abis signaling file, we can make

judgement about the call drop problem and find out the

regularity of the problem. The network performance

index and user experience may be harmed when the

network resource is occupied by some illeagle user.

We can find out the illeagle user by signal tracing or

analyzing the CDR from the switching side.

Call drops caused by handover failure of the

handset

Description:

After the equipment been swapped to the GSM

network, one subscriber complained that under the

mobile environment, his call was automatically hanged

up within one minute after connection. The subscriber's

handset is HS-D907 and it worked normally under the

MOT equipment network before the swap. Another

subscriber complained that when he made a call by HS-

D907 on the highway, the call was frequently hanged up

about dozens of seonds after connection. In addition,

the subscriber said the handset never had the above

problem in other places.


handset

Cause Analysis & Procedure: The engineer traced the Abis interface MM signaling from the

switching side.

When the XX handset is the calling party, it enters the Conversation state after receiving "connect Ack". Several seconds later, the BSSAP entity sends a "cbclearcmdEvent" message to the handset, and the handset automatically hangs up.

When the XX handset is the called party, it enters the Conversation state after receiving "connect Ack". Several seconds later, the BSSAP entity also sends a "cbclearcmdEvent" message to the handset, and the handset automatically hangs up.

According to the signaling tracing analysis, the core network makes the judgement that the connection is actively released by the wireless side. The releasing reason is 1, and the meaning of this value is:

1=Radio interface failure(1)


handset

The engineer traced the Abis interface signaling

from the OMCR side.

After tracing the signaling in the 900/1800 area of Cell 3

and conducting call trace by MA10 software, we found

that the handset released the channels after the

handover failure, and the handovers were all

simultaneous handovers

During the conversation, every time when the handover

command was initiated, the handset pointed to "full rate

or half rate version 3", then the handover was failed.


handset

After comparing the version with the BSC voice version, the core network engineer found that the preferred full rate voice version for the wireless side was version 2, while the switching side only supported voice version 1 and 3, voice version 2 was not selected.

Steps: In "Configure the relation between BSC and trunk

group", the engineer added the TFRV2 to the property of all trunk groups of the 79 and 80 BSC from the switching side. After that, the automatic hang up never happened again during the dialing test.


handset

Under the AMR mode, the HS-D907 handset misunderstands the

encrypted fields in the handover command, so the handover will be

failed. Once the encrypted fields contain non-encription information,

the handset will report invalid mandatory filed, then the handover is

failed, and the call drop occurs.

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

Slow handover caused by improper handover

parameters

Description: During the drive test, the engineer found that the handover

from the Negotiation Building (covered by the 1800 network) to the Hongyan Primary School (covered by the 900 network) was too slow.

The testing vehicle moved from the north to the south, and the MS occupied the Cell5 (CI：10355，BCCH：700) of the Negotiation Building for conversation. When the vehicle moved on, the MS gradually entered the coverage of G1 cell of Hongyan Primary School (CI：11551, BCCH：115), and the level of the serving cell gradually turned to be -86db and became lower and lower. From the table, we can see that the level of the G1 cell was -50db, but the serving cell was not switched to the G1 cell of the school. So the level turned to be worse, and the quality also became worse.


parameters

Tmicro timer

The 900 network and the 1800 network were set to be

on the same layer, and the Tmicro timer was set to be

8S. So when the handset occupied the cell 5 of the

Negotiation Building under the 1800 network, it could

not be switched to the 900 network at the same layer

within 8S after it sent the PBGT handover request. And

after 8S, since the frame error rate became higher, the

device couldn't decode the corresponding neighbor cell.

In order to solve the problem of slow PBGT handover

from the 1800 network to the 900 network, we need to

reduce the value of the Tmicro timer.


parameters Pre-processing Parameter

Description: The survey report contains the large amount (message amount) of Abis interface information. Preprocess of the survey report can be transferred to BTS to reduce the burden of Abis interface link. After preprocess, BTS averages the survey data of MS by its own, and reports to BSC in a lower frequency. Average reporting period can be two, three or four SACCH multi-frames (480 ms). That is, the frequency decreases from the original twice/s to once/2 s, so the message amount of Abis interface decreases. However, the decrease of message amount still depends on whether the message length before preprocess is same as that after preprocess. This parameter determines whether to execute pre-processing or not, and it also determines the period of pre-processing.

Reducing the period of pre-processing will greatly impact the handover. It will speed up the handover, as well as increase the times of handover.

When the pre-processing period is 3, the average window is 4, and the P/N value is 2/3, the handover decision will take 9S. When the pre-processing is turned off , the average window is 6, and the P/N value is 3/4, the handover decision will take 4.5S.


parameters

The related parameters may be

adjusted as follows:

Parameters O r i g i n a l

Value Adjustment value

Tmicro 8s 5s

Pre-processing window 3 0


parameters

Summary:

After the adjustment of related parameters, the problem

of slow handover from the Negotiation Building to the

Hongyan Primary School was solved.

Accoring to the site conditions, we can adjust the pre-

processing parameter, the decision window and the

Tmicro timer to ensure the prompt handover and

prevent the call drop.

Inter-MSC Trunk Congestion Leading to Low

Handover Success Rate

Description:

One network uses dual bands, 900M is our equipment

and 1800 M is Nokia. Recently one IBSC was

commissioned, kept under the new MSC. Performance

statistics shows that handover success rate of this IBSC

is low, specifically, its outgoing handovers are basically

normal, and its incoming handover success rate is low.

Based on the handover statistics of the cells in this

IBSC with low handover success rate, most failures

happen during handovers from Nokia 1800M to 900M of

our company.



Cause Analysis & Procedure: Based on the observation and performance statistics of our

MSC, the handover failures causes are mainly mchMapCauseErr_M.

From the failure observation of the core network, we found that when the failure occurs, the MSC-B has already sent MAP－Prep－HO Rsp containing the handover number to the MSC-A. The MSC-A should send IAM to the MSC-B according to the handover number, then MSC-B send the ACM to the MSC-A to indixate that the inter-office trunk is ready. And then the MSC-A will send HO Cmd to the BSC to inform the BSC to initiate the handover.

At this time, if MSC-A, due to some reasons, such as trunk congestion, can not send the IAM message, the MAP interface timer will time out and release MAP. MSC-A will not send HO Cmd message, and the handover fails.



Based on the field test, the inter-MSC trunk between our MSC and Nokia MSC are congested, and the traffic volume of each line is more than 0.9 Erl. Thus, it can be concluded that the low inter-MSC

handover success rate is caused by the trunk congestion from Nokia MSC to our MSC, leading to acquisition failure of inter-MSC trunk and then handover failure.

We perform the capacity expansion of the inter-MSC trunk, and the traffic volume of every line is reduced and IBSC6 handover success rate becomes normal.

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

SDCCH congestion caused by group sending

SMS

Description:

As shown from the performance report, one site has

heavy congestion on the SDCCH channel. But the TCH

traffic volume of the site is not high and the site is not at

the bordering sections of several location areas. We

think the SDCCH congestion may be caused by the

huge amount of SMS.

SDCCH congestion caused by group sending

SMS

Cause Analysis & Procedure: At first, we tried the signaling tracing. And the result

showed that most of the CM service requests are SMS.

Then we conducted CALL TRACE. After we conducted CALL TRACE for two continuous requests, we found both of them were initiated by the IMSI:460028703084110, and the interval between the two requests was very short. So we thought the IMSI was group-sending the SMS.

According to the signaling trace, the cell has initiated 4536 requests (including the calling/called request, the SMS request and data service request) in total during the traced period. The amount of SMS requests was 3454 (including 3125 SMS requests initiated by that IMSI), and the amount of location update request was 247.

So we were sure that the SDCCH congestion was caused by the group sending of SMS from the IMSI number.

Serious SD congestion caused by core

network module problem

Description

About one third of the cells on 2 iBSC of the XX site had

serious SDCCH congestion. The cell-level statistics

shows that nearly one third of the cells have serious

congestion for all the time. The rate of successful

paging was decreased from 80% to 50%.



Troubleshooting process According to our analysis, the data configuration of the cell

was normal, the alarming of the BSC was normal, and the CPU usage was normal. Compared with the core network, the data of the cell was OK. And the load on the A interface was not increased.

After checking the basic CS measurement of the cell, we found the amount of calling /called attempts was small, and most of the attempts were about location update.

After analyzing the signaling of the cell, we found that a lot of location updates were failed. The handset didin't receive responses after sending the identity response. After the T3120 timer timed out,the channel was released. During this period, the SD channel was occupied for about 20s.

In mormal location update, the handset will receive the response from the network in about 100ms after it sends the identity response:



In mormal location update, the handset will receive the response from the network in about 100ms after it sends the identity response:

Since the failed location update occupied the SD channel for long time, serious congestion occurred on the SD channel. Due to the 3210 Timer on the handset timed out, the failed location update occupied the channel for 20s.

After the handset sent the location update request, there were ID request and ID response between the core network and the handset. It means the SCCP layer is OK, but the core network didn't respond to the handset.



Conclusion

After troubleshooting, the core network found two

modules were in problems. After the supporting A5/1

encryption algorithms of all the cells were disabled by

the wireless side, the SD congestion was temporarily

settled. And the congestion problem did not happen

after the algorithms was enabled again.

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

Handling the shrinking of BTS coverage

Description: According to the statement from the network

optimization engineer of China Unicom in ZhouKou, the coverage of ZTE's BTSs in some counties shrinked after certain period of operation, thus some originally covered areas became coverage holes or areas with weak coverage. This situation has great impact especially for the sub-urban areas, since the sub-urban areas had more omni-directional BTSs, and the distances between the BTSs in sub-urban areas are wider. The shrinked coverage can easily lead to coverage holes. Therefore, the operator may frequently receive complaint from the subscriber that the signal in some area becomes weak.

Handling the shrinking of BTS coverage


According to the subscriber's complaint, we conducted

drive test for the BTS with serious problem of shrinked

coverage. According to our analysis on the drive test

data, the coverage of some BTSs indeed shrinked,

especially for those BTSs that had been commissioned

for long time.

Problem 1: The coverage of the BTS in

FuCaoLou shrinked badly

Description From the table of project parameters, we found that the

BTSs in FuCaoLou Town of Taikang County were 40W omni-directional stations with the height of 50m. This kind of BTS generally can cover a distance of 4 km. According to the above figure, we can see that the coverage of the BTS (frequency point 124) in FuCaoLou is too small. The receiving level of the handset decrerases to －85dBm when the handset is 1 km away from the BTS.

Cause analysis We found that the BTS in FuCaoLou had been

commissioned for more than 2 years. However, the dust filter of the cabinet had never been cleaned during the period. Since lots of dusts were accumulated on the dust filter, the ventilation and cooling function of the fan on the cabinet was greatly affected, thus the working of the carrier, power amplifier and combiner were affected.

Problem 2: The BTS in Wulikou has different

coverage in different direction

Description 从From the Rxlev chart, we can see that the BTS in

Wulikou has different coverage in different direction. The coverage to the east is very samll, about 1 km, while the coverage to the north-easte reaches 5 km.

Cause analysis There are 2 platforms on the tower of the BTS. This site

is shared by the BTSs of CDMA network and GSM network. The CDMA network was commissioned earlier, it uses the upper platform, then the omni-directrional antennas of the GSM network were placed on the lower platform. So some omni-directrional antennas were obstructed by the iron tower, and the coverage in that direction is smaller.

Coverage became weaker due to repeater

frequency is inconsistent

Description: A subscriber from Shao Yang city complained that due to the

unstable signals at ShenJiaCun, he couldn't make a call untill he climed to the top of his building.

Cause Analysis & Procedure: According to our test at the site, the strength of the signal

from the repeater is -90dbm and the signal disappears randomly. After several times of dialing test, we confirmed the reported problem.

From the BTS side, we found the equipment was working normally. After querying, we found that the data of the repeater were not updated after the BTS was changed from omni-directional to directional. Then the repeater didn't work, and the signal strength became weak.

After we changed the frequency of the repeater to be the frequency of the signal source, the problem was solved.

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

"The subscriber is not in the service area"

caused by large CRO value

Description:

Some subscribers complained that the signal was very

weak near the BTS. For most of the handsets, the

signal strength was only 2 grids when the handset was

500 m away from the BTS. The maintenance engineer

said, the signal strength displayed on the handset was

normal, but when the subscriber was called, the calling

party got the response "the subscriber is not in the

service area".



Cause Analysis & Procedure: According to our analysis, the above problem of subscriber not in the

service area was caused by "no response to paging". The possible causes are as follows:

1 The system was congested or over-loaded

If the MSC, the Abis interface signaling link, the BSC, the TRX or the wireless interface is overloaded, "no response to paging" may occur.

2 The cell was interferred by radio signal

If the cell is interferred by strong radio signal for a long time, "no response to paging" may occur.

3 The communication equiment is failed or working unsteadily

If the LAPD link, the uplink or downlink signal from the BTS is poor, "no response to paging" may occur.

If the handset has some problem itself, "no response to paging" may occur, and there will also be problems when the handset is the calling party.



4 The BSC has data configuration error

It mainly refers to that the "Cell Module Information Table" is in error. The content of the table should be in consistency with all the modules of the BSC.

5 The handset was executing other processes, so it didn't respond to the paging

It's a coincidence that a new call is inintiated when the location update, SMS, call releasing process is not completed. This kind of "no response to paging" cannot be avoided in the GSM system. In this case, the calling party only needs to redial the number later.

6 The subscriber is indeed not in the service area or the handset is power-off

In this case, "The subscriber is not in the service area" is the correct response from the GSM.


caused by large CRO value For the complaint of the signal was very weak near the BTS, the

engineer suspected that the RF system and antenna feeder system had problems. But no problem was found when the engineer checked the hardwares of the BTS, the RF connection cable and the antenna feeder system. And the signal was not improved when the engineer adjusted the pitch angles of the antenna. Then the engineer tested the handset and found that the serving cell used by the handset belonged to the neighbor BTS in area B. The signal strength of the serving cell was only -85dBm, but the CRO was set to be 40. So it is very easy for the subscriber to select this BTS. Then the level of the serving cell was too low, it was easy to cause "The subscriber is not in the service area" . After the CRO setting was changed from the background, the problem was solved.

Generally, the CRO value should not be too large, especially for the sub-urban areas. Because the signal received by the MS is depending on the actually received level. If the two cells around the MS have similar C2 value and the actually received levels are quite different, it is very easy to cause cell reselection, thus lead to the problem of unstable signal when the MS is in idle state.


caused by cross-location-area cell reselection

Description:

The subscribers in one office building complained that

they often received the response " the subscriber is

powered off" or "the subscriber isnot in the service area"

when the signal on the handset of the called party was

very good.



The office buiding is a high-rise building. Most of

the complaint are from the subscribers on the 10th

floor to 13th floor. According to the observation at

11th floor, the level received by the test handset is

-70dbm to -90dbm. However, the handset

detected multiple frequencies, including 900M and

1800M. And the signal strengths of different

frequencies were quite similar. There were many

900M frequence points taht belonged to different

location area. The handset frequently reselected

the cell in idle state.



Cell reselection is needed in the following conditions:+

(1) Great loss of radio path occurs on the current registered

cell (C1<=0);

(2) The downlink of current registered cell failed;

(3) The current registered cell is blocked;

(4) According to C2, another cell in the same location area is

better than the current registered cell; Or according to CRH,

a cell in another location area in the selected netrwork is

better than the current regitered cell.

(5) The handset has not accessed the current regidtered cell

successfully after the random access times reached the

maximum number broadcasted on the BCCH.



When the handset is in idle state, it frequently reselects the cell. If the cell reselection is crossing different location areas, a location update will be initiated. After times of dialing tests, we found that "the subscriber is not in the service area" may occur if the handset frequently conducts the location update.

According to the dialing test, some 900M frequence points are from a BTS that is in different location area. So there are two location areas for the 900M nertwork. Added by the location area of the 1800M network, the office building receives signals from 3 different location areas. So the cross-location-area cell reselection frequently occurs on the handset. The number of complaints were significatntly reduced after we requested the operator to adjust the downtilt angle of the 900M BTS antenna, since the office building cannot receive the signals from that

BTS.。

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

Interference caused by Excessive Strong

Back Signals of the Directional Antenna

Description:

During the drive test performed in one GSM network

optimization process, it was found that the area which

was more than one kilometer away from the site (S122)

and should be covered by cell 3 received stronger

signals from cell 1. Cell 1 signals brought severe

interference to other sites.




1． The engineers first walked 100 meters away from the site, circled the BTS tower to test the signals with the MS. and the signals of all directions were found normal.

2． The engineers walked one kilometer away from the site and performed the test. It was found that the areas which should be covered by cell 3, was covered by cell 1, and the signals from cell 1 were about 5 dB stronger than that of cell 3.

3． The engineers first suspected that the jumper connection of the antenna system was wrong, and cross connection might exist. They checked the jumper and no problem was found.

4． The engineers checked the jumpers of the antenna and found no problem. This problem will not affect the transmission of the TRX and the VSWR, which can not located by SITEMASTER.

5． Therefore the engineers suspected that the directivity of the directional antenna of one cell is poor, and the back signals are not shielded. Because the site is space diversity, change the TRX/Main antenna with the diversity receiving antenna.



Then it showed that the directivity of the antenna was poor,

the back signals of the antenna were not shielded, which

led to the great transmission strength of the opposite

coverage direction of the cell.

Because this cell was one TRX cell, and the power did not

deteriorated through using the combiner. Therefore the

areas which should be covered by cell 1 received better

signals from cell 1.

The antennas of cell 1 had 3 degree depression angle and

the test near the site did not show. The areas which should

be covered by cell 2 were not severely affected, because

the TRX of cell 2 is blocked from that of cell 3 by the tower.

Bad KPI of the Cell Caused by External

Interference

Description:

In one project, cells such as KBL029 had very poor

voice quality, high call drop rate and high handover

failure rate. KPIs were as follows:


KBL used PGSM as BCCH (105-124), and TCH used

EGSM 1*3 frequency hopping (975-995). Based on

TRX measurement, idle interference band of these cells

were distributed on TCH TRX instead of BCCH TRX,

assignment failed and most were on TCH TRX.


Interference

It was decided that the cells with strong interference were the cells marked in red in the following figure:


Interference Therefore the interference existed in the red areas, and the

interference is only on the TCH TRX that used the EGSM. The engineers were required to performe a scanning test


Interference

The result shown that the EGSM frequency used

by ET was strongly interfered externally and the

interference power level was about -8 dB.

The scanning result was submitted to ET, and the

government confirmed that it was caused by the

military troops of one country and therefore the

problem could not be solved.

Contents

Call Drop

Handover

Congestion

Coverage

Paging

Interference

Allocation Failure

Long delay in receiving the "recharging is

successful" message

Description

One subscriber complained that he had to wait for a

long time to receive the "recharging is successful".


successful" message Signaling of the core network: the core network releases the CC

connection after sending the short message, then it sends the short mesage, and after sending the short mesage, it releases the RR connection.


successful" message Even if the handset has hanged up, the core network will continue to send

the message. After receiving the clear request 12s later, it will release the connection. If the sending of short message is failed, the core network will resend the "recharging is successful" when the handset is in Idle state.


successful" message

Cause for the failure of sending the message

for the first time

From the signaling of the Abis interface, we found that

after receiving the "release complete" message for 10s,

the handset sent a "release indication" message to

clear the connection. So the sending of "recharging is

successful" was failed.

The handset cleared the connection 10s after receiving

the "release complete", because the T3240 timer of the

handset was timed out then.


successful" message

Judging form the process, we can see the handset

will receive the "recharging is successful" if it

receives the CP-DATA message within 10s.

The engineer recorded the signaling of the

recharging process again. According to the air

interface signaling, it takes10s in total for the BTS

to send the "recharging is successful" to the

handset in 11 steps.


successful" message

T3240 was started when the handset released the connection. And it was stopped when the handset received the CP-DATA messagem T3240. In the signaling, the interval between receiving " release complete" and "release indication" was 10s, that means the timer was not stopped.

There are two possible reasons. One is that the BTS had not send the CP-DATA

message to the handset in time.

The other one is that the handset may have some problem itself, that it didn't stop the T3240 timer after it received the CP-DATA message.


successful" message

Conclusion Based on the above analysis, if the handset actively hangs

up after the recharging, it cannot receive the CP-DATA message within the time specified by the T3240 timer, and it will release the connection, so it will not receive "the recharging is successful" message. According to the subscriber behavior, most subscribers hang up the handset after they hear "the recharging is successful". So the first time of sending the message is failed.

So there are two solutions for this problem: One is to shorten the message of recharging success, so as

to let the total time of message sending + link creation be less than the value of T3240.

The other one is to change the time for sending the message. The core network will send "the recharging is successful" to the handset when the handset is in idle state after the recharging.

Antenna System

ZTE University

Objective

By the end of this course, you will be able:

To Understand the concept of dipole

To state GSM antenna specifications

To comprehend the principle of antenna selection

Content

Antenna overview

Antenna specifications

Principle of antenna selection

Blah

blah

blah bl ah

Radio Waves

A form of electromagnetic radiation typically

generated as disturbances sent out by

oscillating charges on a transmitting antenna

Definition

An Antenna is any

device used to

collect or radiate

Electromagnetic

Waves

Linear antennas are

used:

Monopole (Slab)

Dipole Elements

Mobile Phones

Base Tranceiver

Station Antenna

• Single Monopole

• Patch Antenna

• Array of dipoles

Antenna for mobile communication

Antenna basic structure

Antenna are generally

composed of stacked of dipole

bundling their radiated power

to form a desired antenna

pattern in vertical plains

around the antenna

Depending on the gain desired

that wants to be achieved

several of those diploes can

be arranged on top of one

another

DIPOLES

Wavelength

1/2 Wavelength

1/4 Wavelength

1/4 Wavelength

1/2 Wavelength

Dipole

1800MHz ：166mm

900MHz ：333mm

Generation of radio waves

1个 dipole Received Power：1mW

Multiple dipole matrix Received Power：4 mW

GAIN= 10log(4mW/1mW) = 6dBd

Half wave dipole

Gain=10log(8mW/1mW) = 9dBi

“Omnidirectional array”

Received power：1mW

(Overlook

Antenna

“Sector antenna”


Isotropic antenna

Dipole

Ideal radiating dot source

(lossless radiator)

0dBd = 2.15dBi

2.15dB

dBd and dBi

dBd and dBi

Content

Antenna overview



Antenna electrical properties

Operating Frequency Band

Input impedance

VSWR

Polarization

Gain

Radiation Pattern

Horizontal/Vertical beamwidth

Downtilt

Front/back ratio

Sidelobe suppression and null filling

Power capability

3rd order Intermodulation

Insulation

Type Frequency Range

GSM 900 890 - 960 MHz

GSM 1800 1710 - 1880 MHz

890 - 960 MHz

1710 - 1880 MHzGSM Dual Band

GSM antenna frequency range

BANDWIDTH = 960 - 890 = 70MHz

Optimum 1/2 wavelength

for dipole at 925MHz

at

960

MHz

Antenna

Dipole

at

890

MHz


Standard Value: 50

Cable

50 ohms

Antenna

50 ohms

Impedance

9.5 W 80

ohms 50 ohms

Forward: 10W

Backward: 0.5W

Return Loss： 10log(10/0.5) = 13dB

VSWR (Voltage Standing Wave Ratio)

Voltage standing wave ratio (VSWR)

VSWR1.5

= (VSWR-1)/(VSWR+1)

RetureLoss = -20lg

Calculation of VSWR

120°

(eg) Peak

Peak - 10dB

Peak - 10dB

10dB Beamwidth

60° (eg) Peak

Peak - 3dB

Peak - 3dB

3dB Beamwidth

Bandwidth

Directional Antenna：65°/90°/105°/120°

Omni：360°

Omni-directional Directional

3dBm horizontal beamwidth


3dBm vertical beamwidth


Antenna structure types

Vertical Horizontal

+ 45degree slant - 45degree slant

Polarization

Space diversity

V/H (Vertical/Horizontal) Slant (+/- 45°)

Polarization diversity

Linear Polarization,vertical X Polarization, 45

Types of antenna

Antenna down tilt

Mechanical down tilt

Fixed electronic down tilt

Adjustable electronic down tilt

Mechanical down tile

It is achieved by physically

tilting the antenna out of the

perpendicular by using down

tilt kit

PROS: Cost efficient and

flexible

CON: Has no effect on the

side-lobe characteristics of the

antenna

Input Signal

Electrical down tilt

Electrical downtilt can be fixed or adjustable

Fixed is tuned by the manufacturer

Adjustable allows adjustment in a certain level on the rear of the

antenna

Non down tilt Electronic downtilt Mechanical

downtilt

Down tilt

Antenna tilt development

F/B = 10 log(FP/BP) typically ： 25dB

Back power Front power

FRONT-TO-BACK Ratio

Ratio of maximum mainlobe to maximum

sidelobe

Upper sidelobe suppression and null fill

913 MHz 936 MHz 959 MHz 982 MHz

IMD@243dBm

f1, f2, 2f1-f2, 2f2-f1

Intermodulation

It occurs when two signals of a different frequency mix in a

non-linear device

It can be a problem at any site that has two or more

transmitters

It can be caused by a transmitter of the same system or by a

transmitter in another site that is co-sited or has a site in the

neighborhood

1000mW ( 1W) 1mW

10log(1000mW/1mW) = 30dB

Isolation

Antenna mechanical properties

Size

Weight

Radome material

Appearance and color

Working temperature

Storage temperature

Windload

Connector types

Package Size

Lightning Protection

Dimension

LWH

Length：connected with vertical bandwidth and gain

Width：connected with horizontal bandwidth

Height：connected with techniques adopted

Weight

A factor that can affect transport and

deployment

PVC, Fiberglass

Anti-temperature, water-proof ， anti-

aging，weather resistant

Radome materials

Good-looking

Environment-protecting

Color

Temperature range

Operation and storage

Typical range：-40°C — +70°C

Connector type

7/16”DIN，N，SMA

Female/male

Mast diameter 45-

90mm

Mast

Direct Ground

Lightning protection

Antenna types

By frequency band: GSM900, GSM1800,

GSM900/1800

By polarization: Vertical, Horizontal, ±45º linear

polarization, circle polarization

By pattern: Omni-directional, directional

By down-tilt: Non, mechanical, electronic

adjustment, remote control

By function: Transmission, receiver,

transceiver

7/8” Main feeder

Feeder cable

1/2” （JUMPER CABLE）

Jumper cable

7/16”DIN-F（DIN CONNECTOR）

7/16”DIN-M（DIN & N CONNECTOR）

Connector

Rf port 2

Grounding

Lightning arrestor

Accessories

Trimming Tool or Hand Tool Kit

Clamp

Earthing Kit

Wall Glands

Hoisting Stocking

Universal Ground Bar

Antenna

7/16 Din Connector

7/8“ Cable

Grounding

1/2“ Jumper

Cabinet

EMP

Grounding clip

Grounding bar

1/2 Clamp

Tower Top

Amplifier

7/8“ Cable

Machine house

1/2 Jumper

Antenna system

Content

Antenna overview



Radio propagation in cities

Environment features:

Densely deployed BTS，small coverage area

Decrease over coverage and interference, increase

frequency reuse factor

Antenna selection in cities

Polarization Dual-polarization (Installation space)

Direction Directional antenna (Frequency reuse factor)

3dB bandwidth 60~65°(Control coverage)

Gain 15-16dBi

Tilt down angle Fixed electrical tilt down

Radio propagation in suburb/rural area


Loosely deployed BTS

light traffic

large coverage

Antenna selection in suburb/rural area

Polarization Both dual-polarized and vertical

Direction directional

3dB bandwidth 90°105°

Gain 16-18dBi directional

or 9－11dBi omni

Tilt down angle Mechanical tilt down; 50m high; null fill

Radio propagation in road/highway environment


Low traffic

Fast moving

subscribers

Focus on coverage.

Strip coverage

Two sectors

Omni-cell when pass

towns or tourist site

Antenna selection for highway


Direction Narrow beamwidth directional

3dB

bandwidth 30°

Gain 18dBi－22dBi

Tilt down

angle No tilt down

Radio propagation in mountainous environment


Block by mountains

Big propagation loss

Difficult to cover

Antenna selection in mountainous area


Direction Omni or directional

3dB bandwidth Big 3db verticle bandwidth

Gain Omni (9-11dBi）

Directional (15-18dBi）

Tilt down angle Null fill & electrical tilt down


ZTE University

Objective






protocol


GSM

Content







Technology


GSM Overview




system features.

GSM Basic Concepts


GSM Specification

GSM Overview




GSM composition




Mobile Station (MS)

GSM System Number


IBM

IBM

BSS MSS

MS

MS

PSTN

Other

PLMN

Um

Interfac

e

A

Interf

ace

GSM composition






Station (BTS).

Mobile Station (MS)



GSM System Number





Handover Number



GERAN interfaces



Interfaces



GSM interfaces

Interfaces


domain






channels.




System Messages





TDMA Frame





hyper frame.



Time

Frequency

Frequency

Time


System Messages


2ter, 3, 4, 5, 5bis, 5ter, 6, 7, 8.







Location Update







MS Busy


BSC

（2）

（1）

（3）（4）

MSC/VLR

LAI

1

LAI

2

M

S

M

S


（5）

（2）

（3）（1）

（4）

HLR

MSC/VLR1

MSC/VLR2

M

S

M

S

Location Update

Call process


Handover process



RLC

RLSD

DT1：CIPH MODE CMD

RF CH REL ACK

RF CH REL

REL IND UA

DISC DEACT SACCH

DR：CH REL CH REL

DT1：Clear COM

DT1：Clear CMD


CIPH MODE COM


CC


UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC



IMSI Detach Process

RF CH REL ACK

RF CH REL

REL IND UA

DISC DEACT SACCH

DR：CH REL CH REL

CREF


UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC




RF CH REL ACK

RF CH REL

RLC

RLSD

CH REL

DISC

UA RF CH REL

RF CH REL ACK

REL IND

DEACT SACCH

DR：CH REL

EST IND


DT1:ASS REQ

DT1：CIPH MODE CMD

CH ACT ACK

CH ACT

PHY CONT CONF

UA

SABM

PHY CONT REQ


DT1：Clear COM

DT1：Clear CMD


CIPH MODE COM


CC


UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

MS BTS BSC MSC

DTAP:SETUP

DTAP:CALL PROC

DI：ASS COM

DTAP：Alerting

DTAP：Connect

DTAP：Connect ACK

数据流

DTAP：Disconnect

DTAP：Release

DTAP：Release COM

DTAP:CM SERV ACCP





RF CH REL ACK

RF CH REL

RLC

RLSD

CH REL

DISC

UA RF CH REL

RF CH REL ACK

REL IND

DEACT SACCH

DR：CH REL

EST IND


DT1:ASS REQ

DT1：CIPH MODE CMD

CH ACT ACK

CH ACT

PHY CONT CONF

UA

SABM

PHY CONT REQ


DT1：Clear COM

DT1：Clear CMD


CIPH MODE COM


CC


UA

SABM

IMM ASS IMM ASS CMD

CH ACT ACK

CH ACT

CH RQD CH REQ

DTAP:SETUP

DTAP:CALL CONF

DI：ASS COM

DTAP：Alerting

DTAP：Connect

DTAP：Connect ACK

数据流

DTAP：Disconnect

DTAP：Release

DTAP：Release COM

BSC MSC BTS MS



DT1：HO PERF

HO CMD

CH ACT

MEAS REP

RF CH REL ACK

RF CH REL

DI：HO COM

EST IND

HO DET

CH ACT ACK


MEAS RES

DR：HO CMD

HO ACCESS

PHY INFO

SABM

UA

HO COM





technologies.

Voice Processing


Adaptive equalizing

Diversity Receiving


Power Control

Timing Advance


Voice Processing


Adaptive equalizing




whole system.

Diversity Receiving




Power Control




GSM network.


Timing Advance





technologies




EDGE.



GPRS Radio Channel








High rate


Mature technology













efficiency.


GPRS Radio Channel




channel coding.




release flow.



B, and C.

GSM Network optimization overview

Objectives


State network optimization flow and the Content

Master common network optimization problems analysis

and solution

Understand Dual-Band Network and its peculiar

problems and solutions

Contents

Overview of radio network optimization

Introduction of network performance evaluation

Flow of Radio Network Optimization

Routine network optimization tasks

Common network optimization problems

Dual-Band network optimization

Object Purpose

The upcoming network

Network in operation

Improve system performance

Maximize service quality under existing

system configuration

Maximize benefit of existing network

Suggestion of network future

maintenance and planning

Network

Optimization

Data

Collection

Data

Analysi

s

Confirm

Reason

Make

Solution

Solution

Implement

Network Optimization Concept

Cause of Network

Optimization

End-user changes

New calling model

Subscriber distribution change

Environment change

New Building,Road,Vegetation

Network structure changes

Coverage , Capacity

Application of

New Technology

New Equipment

New Standard

Why Optimization

Network Optimization Position

Position in mobile communication

Specific working flow of mobile

networks

Throughout network planning,

implementation and daily

maintenance

Closed-loop management of network

quality

Necessary and effective approach of

Improving network operation quality

Relation with Maintenance

Maintenance is the foundation of

network optimization

Network optimization is the

further development based on

maintenance

Maintenance focus on equipment,

Network optimization focus on

network,

Maintenance work is the network

value-keeping process

Optimization is the network

value-added process

Network optimization category

Commission and maintenance optimization

ZTE equipments were not

used in network optimization,

but network operator wants

us (as the third party) to do

network quality evaluation,

optimization adjustment,

complementary planning,

etc.

Independence Optimization

Network

optimization

category

Engineering network

optimization

Maintenance network

optimization

Content


Introduction of network performance

evaluation





Network

Evaluation

Object

Network in

operation

Means Check and analyze: •Collection customers’ complain, •frequency allocation •radio parameter, •BTS equipment •MSC data •System performance data

Objectives Output reasonable and objective evaluation •network planning quality, • network running condition, • network operation question, the hidden danger, • network investment utilization factor

Concept

Drop call rate

TCH/SDCCH congestion rate

TCH allocation success rate

Handover success rate

Radio coverage

Traffic

Channel available rate

Optimization

Voice quality

KPI

Network performance KPI

Performance

evaluation

Analyze network KPI and output optimization suggestion

Resource

utilization

evaluation

By traffic statistic, export Traffic, calculate the utilization of network

resources. Reflect the capacity of network

Network

layout

evaluation

Network size, types of coverage, the feature / topographic

distribution, network architecture, site / Traffic density, indoor coverage

strategy

Network

test

evaluation

Through DT and CQT test, simulate users calling process. Reflect

the user’s feeling of communication

Voice

quality

evaluation

Evaluate voice quality by MOS

Network evaluation content

Contents







1 2 3 4 5

Detailed Flow

Data

analysis

Require

analysis Data

collection

Preparation Equipment

check

8 6

Adjust

plan

Summary

acceptance

7

Result

verify


Network status: coverage, voice quality，radio KPI,

topographic and geographic feature, population

distribution, traffic hot spot

The most important problem of existing network

Expected performance KPI and dead line

Working interface with operator

Analysis Framework

2 1 3 4 5

Data

analysis

preparation Data

collection

Require

analysis

Equipment

check

8 6

Adjust

plan

Summary

acceptance

7

Result

verifies

Goals Detail

requirement

Expectations indicators Estimate time Special requests

Further detail

operator

requirement

Prepare data &

equipment

History P&O report Digital map Site information Network Index DT and related test equipment

…………

Preparation

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection

Require

analysis

preparation

8 6

Adjust

plan

Summary

acceptance

7

Result

verifies

Avoid the

Hardware

problems to affect

overall network

performance

Checking object

BTS hardware fault Antenna and feeding cable Clock problem Unstable power supply system Working environment condition

BSC/OMCR fault

Equipment check

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection

Require

analysis

Preparation

8 6

Adjust

plan

Summary

acceptance

7

Result

verify

Current service condition

System performance data

Field test data

Subscriber complaints

Signaling trace

The data directly related to call processing of

mobile system in MSC

Data collection

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection

Require

analysis

Preparation

8 6

Adjust

plan

Summary

acceptance

7

Result

verify

Traffic

statistics Drive test

Longer period

data

Comprehensive

analysis of

relative KPI

Reflect

downlink

signal

situation

Signaling data

Analysis coordination

between system entity

Provide essential clue

for network failure

Subscriber complaints

The non-

professional data

Need confirmation

again

Data analysis

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection Require

analysis preparation

8 6

Adjust

plan

Summary

acceptance

7

Result

verify

Make plan

Risk control Avoid frequent

adjustment Partial experiment plan Quickly rollback plan Implementation step Backup

Reasonable time Agreement from operator

Check plan

Audit by the

expert and

operator

Confirm feasible

solution

Implementation

Detailed record

optimization

process and

results

Adjust optimization plan

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection

Require


8 6

Adjust

plan

Summary

acceptance

7

Result

verify

Performance

Comparison

Comparison of

test

Compare DT result. Compare CQT result.

At the same test

period and route

Compare and

analyze the data

before and after

adjustment

Verify result

Analysis Framework

3 1 2 4 5

Data

analysis

Equipment

check

Data

collection

Require


8 6

Adjust

plan

Summary

acceptance

7

Result

verify

Optimization

report

Project

acceptance

Accept on

standard

Operator involved Signed by

operator

Project

summary

Knowledge

transfer Job evaluation

Document

backup

The work done

The achievement

obtained

Summary and acceptance

Contents




Routine network optimization



RF

Optimization

Three kind of routine work

Performance statistics

CCCH

Radio resource

assignment

Channel mode Dedicated channel

assignment

Handover

Channel release

Channel establish

Several important counters

Abis interface

A interface

BSC

cell

Neighbor cell list

Several key network element

Some specific event can

trigger corresponding counter

to do add 1 for counting,

through the observation of

counters in a specific period of

time, We can know the

network running status

Network monitor

Statistics report table

Concept

Network performance statistics report come from the

calculation of counters.

Quality KPI Statistical report reflect faults and solution

Drop call

Handover

Can’t call (block,

interference...)

Network access (large

coverage, indoor

coverage...)

Voice quality

Hard fault：Failed board or partial failure of

equipment. Generally hard faults can generate

obvious warning information on OMC-R

Soft fault：System still running, but part of system is unstable or not in the best status

Network monitor

Other monitor methods

DT and

CQT

Subscrib

er feeling

and

customer

complaints

Environment

New

building

External

interference

Network monitor

Network identification parameters System control parameters

Cell selection and re-selection parameters Network function parameters

Radio

parameter

Identify MS and network

The parameters related to

system configuration. Which

will Influence the service load

and signaling flow of the

system (capacity)

The parameters related to cell

selection and cell re-selection,

which will affect coverage

The parameters that provide various system functions

BSS parameter adjustment


Selection and reselection

parameters


Network function

parameters

Network

identification

parameters Radio

parameter

CGI：

BSIC： BSIC＝NCC&BCC


Selection and

reselection

parameters

System

control

parameters


Network identification

parameters

Radio

parameter

IMSI attach detach

Common control channel configuration (CCCH CONF)

Access allowed reserved blocks (BS AG BLKS RES)

Paging channel multiplexing frames (BS PA MFRMS)

Periodic location update timer (T3212）

Radio Link Timeout

Permitted network color code （NCC PERMITTED）

Maximum retransmission times (MAX RETRANS)

Transmission distributed timeslots （TX INTEGER）

Cell access barring（CBA）

Wait time（T3122）

Multi-band indication （MULTIBNAD ）


Selection and reselection

parameters

System control

parameters

Network function

parameters


parameters

Radio

parameter

Additional re-selection

parameter indication (ACS)

Reselection parameter indication (PI)

Cell barring qualifying （CBQ）

Cell reselection offset （CRO）

Temporary offset （TO）

Penalty time （PT）

Cell reselection hysteresis (CRH)

Maximum power level of the control

channel （MS TXPWR MAX CCH）

Allowed access minimum receiving

（RXLEV ACCESS MIN）

Selection and

reselection

parameters

System control

parameters

Network function

parameters


parameters

Radio

parameter

Power control indication (PWRC）

discontinuous transmission

（DTX）

New establishment cause

indication (NECI）

Call reestablishment allowance

（RE）


Some BSC timers

T3111： Timer

between channel release

and RF deactivation.

T3101： Waitting

timer used in immediate

assignment process.

T3103：Intra-BSC

handover timer to hold TCH

both in original and target

cells

T3109：used limit

SACCH release time in

case of a radio link

timeout.

T3107：used to restrict

the TCH assignment time


Check balance

of UP/DOWN link

Feeder cable check

Check interference

of UP/DOWN link

Antenna check

Azimuth

Tiltdown angle

Height

Isolation

Cross connection

VSWR high

Connector loose

Signal leakage

RF

Optimization

RF Optimization

Check balance

of UP/DOWN link

Feeder cable check

Check interference

of UP/DOWN link

Antenna check RF

Optimization

Uplink Interference

Check the ratio of un-decoded

RACH and uplink signal quality

handover to determine internal or

external uplink interference.

Repeated change frequency

Check idle channel interference

band

Frequency scanner

Downlink

Interference

Cell coverage test

Adjacent channel scan

Co-channel interference

detection

RF Optimization

Check balance

of UP/DOWN link

Feeder check

Check interference

of UP/DOWN link

Antenna check

RF

Optimization

Preparation information ：

Link budget used in radio

design

BTS functions : DPC,DTX

Cell main parameter

BTS debugging report

Field data

collection

Abis signaling trace by

OMCR

Signaling analysis by MA10,

retain measurement report

message

RF Optimization

Contents







Call drop

handover

coverage

interference

congestion

Common Network Optimization Problem

1

Common phenomenon

Overshooting

Blind spot Sector cell

Overlaps

Coverage

2

Investigation

Power

Control

Measure

Rx_LEV

Measure

Drop

Call

Measure

Neighbo

r Cell

Measure

Undefin

ed

neighbor

cell

(lonely

island)

Locate

reason

Cell

perform

ance

measure

Cell

handover

out

measure

Coverage

3

Problem solution

Add new

site

Adjust

antenna

and feeder

Coverage

solution

Increase power

of TRX,MHA

Adjust network

parameter

Coverage

1

Common phenomenon

High call

drop rate

Bad voice

quality Ping-pong

handover

Handover

failure

Interference

2

Investigation

Handover failure but reestablish Also fail

Interference

3

Solution

Increase

the

distance

of co-

channel

or

adjacent

channel

cell

Reduce

BTS

power

Avoid

external

interference

frequency

Adjust

antenna

height

azimuth

down

tilt

Adjust

frequency

plan

Solution Narrow

beamwidth

antenna

Use

frequency

hopping,

DTX,

DPC

Interference

1

Common phenomenon

Difficult to originate

a call

Incoming

handover

failure

Low calling

success rate

Congestion

Congestion

2

Investigation －SDCCH congestion

Unreasona

ble access

parameter

Unreaso

nable

LAC

Small

T3212

SDCCH

frequency

interferen

ce

SDCCH

number

Wrong

LAC

setting

Too

many

SM

2

Investigation －

TCH congestion

•Check equipment hardware

•Check TCH Congestion rate

Locate

reason

Congestion

3

Solution －

TCH congestion

Adjust

antenna

height,

direction,

down tilt

Change

BTS

power

Open

half rate

function

Open

traffic-

based

handover

,

direction

al retry

function

solution

Expand

TRX or

add new

site

Adjust cell

access,

reselection

and

handover

parameter

3

Solution － SDCCH congestion

Check cell

CRH of

LAC

boundary

Rational

division of

LAC

Increase

SDCCH

Check

LAC

setting solution

Adjust cell

access

parameter

increase

T3212

Check

frequency

interference

Congestion

1

Common phenomenon

HO failure

or HO slow Unreasonable

Proportion of out/in HO

Frequent

handove

r

Handover

Neighbor cell

setting check

Define neighbor

cell for lonely

island

2 Investigation and

solution

Very high HO

failure rate

Neighbor cell high

load

Neighbor cell TRX

fault

Neighbor cell

transmission fault

Same frequency

and same BSIC for

nearby cells

Lonely island

Interference No enough

overlap area

between source

cell and target cell

Work out

hardware problem

Work out neighbor

cell problem

Improve radio

environment

Improve coverage

1 2 3 4 5

coverage Hardware Bad radio

environment Neighbor cell Congestion and transmission fault

Handover

2

Investigation and

solution

Two transmitting

antennas of same

cell cover scope is

different.

HO aarameters

unreasonable or

mismatch

Repeater only

enlarged part of

frequency of a cell.

Check MSC

REMOTELAC

table

A interface

signaling load

congestion, lead

HO signaling lost

Check antenna

condition,

Check and adjust

HO parameters

Adjust or replace

Repeater

Complete LAC

info in MSC

Expansion

6 7 8 9 10

Signaling link Heavy load

Antenna

problem LAC Not defined in MSC

Repeater problem

Parameter setting problem

Handover

1

Three type

MS can not decode

SACCH result in RLT

timeout and dropped

calls.

Radio link timeout

HO timer timeout，MS is unable to

access the target

channel, and can

not return to the

original channel as

well.

Handover call drop

Equipment failure

cause the call

dropped, Such as

LAPD link break

and so on

LAPD call drop

Call drop

3 Investigation and

solution

Blind spot

Poor indoor

coverage

overshooting

co-channel

interference

Adjacent channel

interference

Unreasonable

parameters.

Neighbor cell not

complete

Same BCCH/ BSIC

Traffic Congestion

Clock asynchronous

Feeder mistake

connection

Azimuth and

downtilt inconsistent

Antenna, feeder

damage, leak water

The transmission

break, Interrupt,

high BER

Adjust radio para.

Adjust engineer

para.

Solve hardware

problem

Adjust engineering para.

or frequency plan

Open DTX、FH、DPC

Solve equipment

problems

Adjust para.

Balanced traffic

Calibration Clock

Analysis traffic

statistics

Examination

alarm

On-stie check

Observation

transmission and

board alarm

Transmission path

checks

1 2 3 4 5

Transmission Coverage Antenna and feeder

Handover Interference

Call drop

3

Investigation and

solution

such as

inconsistent

software

version

RLT ,Min-Acc-

Min, Minimum

level of RACH,

RACH busy

threshold.

Upgrade software check and

adjust radio

parameters

6 7

Unreasonable radio para.

Other reasons

Call drop

Contents







GSM900 macro GSM1800 macro

900 micro 1800 micro

P-cell P-cell

GSM900/1800 umbrella-like cell macro

A lot of cells are

available for choice.

Concept

Ideal dual-band network

MS roaming in two band network

MS can seamless handover between two band network

Traffic balance in the dual-band network

Avoid frequent re-election and normal location update

Avoid frequent unnecessary handover between dual-band

network

Dual-band network unique problem

Traffic is not balance

Ideal dual-band network

Frequent location

update

Frequent HO and

reselection

Traffic management

principle

Selection principle Traffic balance principle

Layer principle

Automatic traffic

balance technology

based on dynamic

priority to prevent

traffic congestion.

900 networks and 1,800 networks in different layer

MS idle: Select the 1800 cell first

MS busy: Remain in the layer

where the call is originated,

and avoid unnecessary

handover between layers.

1800 layer

900 layer

The basic principle

Balance the traffic in

dual-band network

Traffic Balance

While covered by dual-

band cells ,try to reduce

the frequent handover

and location update,

reduce network signaling

flow

The efficient use of

resources

Traffic control principle

Objective

Adjust cell engineering parameters Adjust cell radio parameters

BTS transmit power

Antenna height, azimuth and

downtilt

Antenna type

Through modifying the signal level of dual band cells in the same position,

change priority and direction of cell selection, reselection and handover.

Balance traffic of dual band cells.

Cell selection ：C1，CBA，CBQ

Cell re-selection ：C2

Dual-band handover ：

• PBGT handover control

• Handover priority

The main optimization method

900M cell：CBQ = 1，CBA = 0，C1=15

1800M cell：CBQ = 0，CBA = 0，C1=10

Power on the MS to make cell selection

Application of Cell Selection

MS select 1800 network first, set the 1800 cell to a

normal priority cell CBQ = 0，CBA = 0

Set the 900 cell to a low priority cell CBQ = 1，CBA = 0

900M cell：C1=15，C2=5

1800M cell：C1=10，C2=20

Cell re-selection in the idle mode

Application of Cell Selection

MS Reselects the 1800 network, set a large

offset for the 1800 cell and a small offset for

the 900 cell.

1800 cell

900 cell

PBGT

handover

Bar Inter-layer PBGT Handover

Multi-path fading

can cause a

large number of

PBGT handover

80% handover is

PBGT, it must be

barred.

Different layer use different

handover priority

Other policies

Automatic traffic balance

policy based on dynamic

priority

Traffic-based handover

Directed retry between

different bands

Fast fading handoff

algorithm

Set handover protection

time

Other optimization policies

GSM Radio network planning principle

ZTE University

Objectives


Describe the contents of information collection

State capacity planning

State coverage planning

Describe steps to notices of site survey

Master frequency planning and anti-interference

technology

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Overview

Mobile service forecast

Subscriber forecast, distribution

Network equipment &

operation profile

MSC,BSC,BTS

Traffic statistic, quality

City planning

City type, map

Population

Economic development plan

Road and transport condition

Information Collection

Radio propagation survey

Geographic environment

Plantation

Network traffic distribution

Industrial, commercial, residential

area

Coverage and quality analysis

Coverage and quality (DT)

Statistic of A, Abis and OMCR

Interference analysis

Frequency allocation

Frequency scanning test

Analysis and survey

Frequency Other Traffic Model Capacity Coverage

Limited

frequency

Available

bandwidth

Frequency

resources

Coverage

KPI

Traffic

distributing

Coverage

size

Redundancy

and other

requirements

traffic

distributing

Traffic and

system

capacity

Data traffic

model

Voice traffic

model

Site

configuration

Propagation

environment

Electronic

map exists ?


Summary

Network planning information collecting

template

Inadequate

info

1. What is necessary information?

2. What is supplementary info?

？

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Basic concepts

Traffic volume

Traffic model

Erland

Call loss rate

Erlang B table

Erlang B table 2% 5%

1 0.020 0.0532 0.223 0.3813 0.602 0.8994 1.092 1.5255 1.657 2.2186 2.276 2.9607 2.935 3.7388 3.627 4.5439 4.345 5.37010 5.084 6.21611 5.842 7.07612 6.615 7.95013 7.402 8.83514 8.200 9.73015 9.010 10.63316 9.828 11.54417 10.656 12.46118 11.491 13.33519 12.333 14.31520 13.182 15.24921 14.036 16.18922 14.896 17.13223 15.761 18.08024 16.631 19.03025 17.505 19.985

Capacity Planning Procedures

Confirm subscriber

number

Site numbers and

configuration


ratio

Site distribution and

their latitude and

longitude

Reach target of

capacity planning

1 2 3 4 5

Network scale Capacity information

collection Site layout Traffic distribution

analysis

Site type and

number

Capacity Planning

Information collection

Network type: GSM900, DCS1800, dual-band network or WLL network？

System capacity requirement. No of subscriber and the traffic?

Traffic model of the voice service?

Equipment type: V3/SDR? Model? Indoor or outdoor? DPCT applied in V3 or not?

Data service required? EDGE TRX? Data service penetration rate? Traffic model of data service?

Frequency resource range ? Is there frequency that are prohibited? Maximum site configuration ?

Forecast and investigation traffic density and define traffic distribution ratio.

Traffic density distribution

Traffic distribution analysis is to categorize the planning

area into areas of different service levels based on

forecast and survey of traffic density distribution

● how many phases and what is the ratio of

subscribers in each phase

● what is the planning area range and the

traffic distributing ratio in DU/MU/SU/RU.

● Provide existing sites and their

configuration and performance statistics

report data

扇面 1

41%

扇面 2

26%

扇面 3

15%

扇面 4

11%

扇面 5

7%

Service level by radio propagation environment

Area Topographic features

Dense

urban

Average height of surrounding buildings is more than 30 metres (over 10 storey)

and average distance between buildings is 10-20 metres. Usually the buildings

are crowded around the site with the height of 10-20 stories and the ambient

roads are not considerably wide.

urban



distributed around the site. Mostly are below 9 stories and some are over 9

stories and the ambient roads are not considerably wide.

suburb



distributed around the site. Mostly are 3-4 stories and some are over 4 stories.

Roads around are wide.

rural Average height of surrounding buildings is below 10 metres. They are dispersed

and mainly are 1-2 storey high. There are spacious space between.

Service level by service distribution area

Area Distribution Features

Dense

urban

Traffic is heavy with high data service

rate, mainly for data service

development

Mean

urban

Traffic is relatively heavy and date

rate should be comparatively high.

Data service is required

Suburb Traffic is low and only low-speed

data service

Rural Traffic is quite low. Site is for

coverage purpose and data service

quality are not ensured.

Both radio propagation

environment and service

distribution factors should all

be taken into consideration.


No. of BTS for capacity limited area

Maximum site type by frequency reuse pattern

Traffic per site by traffic model, Erlang-B table

Total number of BTS: Total traffic / single site

traffic


No. of BTS for coverage limited area

Total area / single site coverage (according to service

level)

Cell traffic = Cell coverage * traffic density

TCH number (Erlang-B table)

SDCCH number

TRX number

Start

Frequency resources

Capacity of each cell

Capacity per site

Site configuration & number


Maximum Site type

Channel planning & data service

Erlang B table

Traffic model

Site configuration

Traffic & distribution

Network Scale Coverage Planning

Site type and number

No of SDCCH

Suppose SDCCH average process time is 3s，Location updating

process is 9s,BHCA=2

The traffic of SDCCH per subscriber is:

(3×2 + 9) / 3600 = 0.0042 Erlang

4SDCCH call loss=2% can support 1.092Erlang，


look up in Erlang-B，call loss=2%， 6.5Erlang need 12TCH(2TRX)

8SDCCH call loss=2% can support 3.627Erlang


Look up in Erlang-B，call loss=2%，21.6Erlang need 30

TCH(4TRX)

SDCCH configuration

TRX Channel SDCCH type SDCCH TCH TCH traffic

(GOS=2%)

1 8 SDCCH/8 1 6 2.28

2 16 SDCCH/8 8 14 8.2

3 24 2*SDCCH/8 16 21 14.9

4 32 2*SDCCH/8 16 29 21

5 40 2*SDCCH/8 16 37 28.3

6 48 2*SDCCH/8 16 45 35.6

7 56 3*SDCCH/8 24 52 43.1

8 64 3*SDCCH/8 24 60 49.6

9 72 3*SDCCH/8 24 68 57.2

10 80 4*SDCCH/8 32 75 64.9

LA planning

LA border

Paging capacity in LA


Influence by Short message

LA border

Avoid dense city with high traffic area

Avoid area with high mobility of subscribers

Cross the road slantwise

Consider traffic expansion

Paging capacity

IMSI/TMSI

Second paging（local paging、global paging）

Paging group：

(BS-AG-BLK-RES)

(BS_PA_MFRAMS)

Paging blocks/ per second =（9-AGB）/0.2354

Paging number / per paging block : B = 2 or 4


Paging numbers per second（P）

P =（9-AGB）/0.2354 * B

Suppose：

Average time of call：60s，ie:1/60Erl

Traffic of LA（T）

75％of MS response first paging，25％ of MS response

second paging

Paging congestion when 50% of maximum paging.

T*30%/(1/60)*1.25 = P*50% = 59.47*3600*50%

Influence by short message

3/per sub/per day

30% retransmit

Convergence factor:0.12

Subscriber in LA:100000

SM number in busy hour

100000×3×0.12×(1+30%)=46800

Consider holiday case: 8 times

Coverage

Planning

Capacity

Planning

Network

Scale

Summary


just an initial plan,

Add or reduce sites

based on radio

coverage planning

and analysis.


a repeated, gradual

process helping to

decide site number

and type.

Contents


Capacity Planning

Coverage Planning


Coverage Emulation

Frequency Planning

Coverage Planning flow

Set parameters Estimated

coverage radius of

each site

Allowable max path

loss

Information of site

distribution ,


of sites

Target of coverage

1 2 3 4 5

Network scale Network

parameter

Site layout &

coverage emulation Link budget Coverage radius

estimate

1

Network parameter

Confirm network parameters

Network category: GSM900,DCS1800, dual-band or WLL network?

Equipment type: V3/SDR? Model? Indoor or outdoor?

Carrier Transmission power is 40W，60W，80W? Are data service required? EDGE carrier frequency？

Antenna model: antenna gains, horizontal and vertical beam width, antenna downtilt, polarization mode and electrical downtilt etc.

Antenna parameter: antenna available height, directional angle and downtilt.

Apply tower top amplifier?

Feeder type: 7/8 feeder or 15/8 feeder?

Maximum site configuration is? Are there special requirements toward configuration of combining and distribution unit?

What is KPI? What is level and area coverage rate?

2

Link Budget

Link budget

Definition:

Link budget is the calculation of loss and gains on one

communication link.

Target:

Maximum power of the site, avoid invalid downlink

coverage, reduce interference and system noise.

Allowable maximum indoor & outdoor path loss of uplink

and downlink Uplink Downlink

PA

Feeder loss Transmission

loss

Antenna gain Penetration loss

Site sensitivity

Fading margin

Body loss MS power

Link budget

Losses

Margin reservation

Gains

Network Type & Equipment

Link Budget

Transmission power and reception

sensitivity of MS/BTS

Fast fading margin

Slow fading margin

Interference margin

Site antenna gain

MS antenna gain

TMA gain

Path loss

Body loss

Vegetation

loss

Building penetration

loss

Feeder and

connector loss

Combiner and

splitter loss

Link budget

Link budget-Equipments

MS transmission power is showed as follows：

Power

class

GSM 900

Nominal

Maximum output

power

DCS 1800 Nominal Maximum

output power

1 1 W (30 dBm)

2 8 W (39 dBm) 0.25 W (24 dBm)

3 5 W (37 dBm) 4 W (36 dBm)

4 2 W (33 dBm)

5 0.8 W (29 dBm)

Link budget-Equipments Series Modulation Transmission power Reception

sensibility

Biggest site

BTS

V3

B8018 GMSK 60 W 47.78 dBm

-112 dBm S18/18/18 8PSK 31 W 45 dBm

B8112 GMSK 60 W 47.78 dBm

-112 dBm S12/12/12 8PSK 31 W 45 dBm

M8202 GMSK 30 W 44.78 dBm

-110 dBm S2/2/2 or O6 8PSK 20 W 43 dBm

Link budget-Loss

Path loss

Body loss

Vehicle loss

Plantation loss


Feeder and connector

loss

Combining and

distributing unit loss