collection of gsm rnp technical problems and replies(no.15)-20050308-a-1.0

Collection of GSM RNP technical problems and replies(No. 15) Internal Open

2005-03-08 Confidential Information of Huawei. No Spreading without Permission

Page1, Total26

Document number Product name

Applicable for Product version

Drafted by Wireless Network planning Dept.

Document version V1.0

Collection of GSM RNP technical problems and replies(No. 15)

(For internal use only)

Prepared by: Date:

Reviewed by: Date:

Reviewed by: Date:

Approved by: Date:

Huawei Technologies Co., Ltd.

All rights reserved



Page2, Total26

Contents

Problem 291 3002C Traffic Statistics UL & DL Out of Balance...........................4

Problem 292 Effect of cell broadcast service on the network indexes ...................5

Problem 293 Problem during inter-BSC handovers ...............................................6

Problem 294 How is the GT800 frequency number defined in the system? ..........7

Problem 295 In which type of bit map are frequencies in EGSM/RGSM band

numbered?...............................................................................................................8

Problem 296 Is there a quantification calculation model for the effect of transmit

power on coverage? ..............................................................................................11

Problem 297 Component indexes of CDU at BTS312 .........................................12

Problem 298 Are there any special requirements for the separation angle between

cells at the same base station?...............................................................................13

Problem 299 Questions about the “Inter-layer Handover Threshold” and

“Inter-layer Handover Hysteresis”........................................................................14

Problem 300 The interval of HOs in dualband network.......................................16

Problem 301 The influence of half-rate on dualband cooperation and traffic

balance ..................................................................................................................18

Problem 302 Why does dualband handover demand A interface support PHASE 2

or above?...............................................................................................................19

Problem 303 Does packet paging need to be sent to all the cells in one LAC of

BSC? .....................................................................................................................20

Problem 304 A question about paging..................................................................20

Problem 305 How to obtain the CRH for cell reselection across the LAC? ........21

Problem 306 About BCCH TRX aiding ...............................................................21

Problem 307 How to make out the No.7 link capacity on interface A? ...............22

Problem 308 General propagation models adopted for 1800M network by Huawei

..............................................................................................................................23



Page3, Total26

Problem 309 Why is there no description about the influence of downtilts on

coverage in the propagation models?....................................................................24

Problem 310 The vertical half-power angle for the small base station antenna ...25



Page4, Total26

Problem 291 3002C Traffic Statistics UL & DL Out of Balance

Problem 3002C Traffic Statistics UL & DL Out of Balance

Descriptio

n

The traffic statistics shows that the UL and DL are out of balance at many 3002C small

base stations. The DL is usually higher than the UL. What causes that?

Reply The UL and DL balanced metrics at the BSC:

Balance rank = DL power level – UL power level – 6dB (sensitivity compensation). See

the table below:

Uplink and downlink balance level Downlink receiving level – uplink receiving level – 6 (dB)

1 -15 2 -14 ~ -10 3 -9 ~ -6 4 -5 ~ -3 5 -2 ~ 0 6 0 7 1 ~ 2 8 3 ~ 5 9 6 ~ 9

10 10 ~ 14 11 ƒ15

From the statistical aspect, the theoretical nominal Difference value of UL and DL

signal levels is 6 dB, and the traffic statistics should be distributed symmetrically around

Scale 6. As the statistical spans if different scales are different, the range for UL and DL

signal levels to be same is very small, only ! 0.5 dB.

The originally designed UL/DL balance measurement function was made

according to the conditions and the specifications in the protocols of that time (BTS

sensitivity is –104 dBm, MS sensitivity is –102 dBm). With the advancement of

technology, the sensitivity of Huawei BTS has reached –110 dBm, and the

sensitivity of most MSs has reached –104 dBm. From the algorithm of the traffic



Page5, Total26

statistics above, when the UL and the DL are balanced, the Difference value between

the UL and DL levels has reached 10 dB, not 6 dB in the formula. According to the

present traffic statistical method, suppose it is BTS312 and the combiner loss is 4.5 dB,

the central value when UL and DL are balanced should be around Rank 8. 3002C is not

equipped with a combiner, and the DL power is 1.5 dB larger than that of BTS312.

Therefore, for 3002C the central value when UL and DL are balanced is around Rank 9.

The UL and DL balanced performance measurement used to be an item of traffic

statistics. There are some defects in it and with the development of technology, it now

cannot indicate the actual performance of the base station. This item of traffic statistics

can serve as a reference in problem analysis. When it indicates that the base station

deviates far from the UL and DL balance range, you need to check the software or

hardware related to the UL and DL balance.

Problem 292 Effect of cell broadcast service on the network

indexes

Problem Effect of cell broadcast service on the network indexes

Descriptio

n

The original configuration of the cell is SDCCH/8. To have to service of the cell

broadcast, we will change the configuration to SDCCH+CBCH. How will it affect the

network indexes and how can we mitigate the problems?

Reply This will reduce the number of SDCCH sub-channels from eight to seven and increase

the probability of congestion on SDCCH. Besides, the radio connection rate may drop

accordingly.

Configure more SDCCH to the congestion related cell to solve the problem.



Page6, Total26

Problem 293 Problem during inter-BSC handovers

Problem Problem during inter-BSC handovers

Descriptio

n

This problem occurs in the optimization:

There is a big disparity between the "Attempted incoming BSC handovers" in "BSC

performance measurement" and "Attempted incoming inter BSC inter cell handovers"

in "Inter-cell Handover Measurement Function ".

See the following specific figures:

Dec 9: "Attempted incoming BSC handoversNumber of into- BSC handover attempts"

in "BSC overall performance measurement": 1062; "Attempted incoming inter BSC inter

cell handovers" in "Inter-cell Handover Measurement Function ": 220

Dec 10: "Attempted incoming BSC handoversNumber of into- BSC handover attempts"

in "BSC overall performance measurement": 711; "Attempted incoming inter BSC inter

cell handovers" in "Inter-cell Handover Measurement Function ": 244

We found many errors in the data of inter-BSC handovers, which exist even after

modification. What causes this problem?

Reply 1. Attempted incoming BSC handovers

Description: During the procedure of inter BSC handover, source BSC initiates a

handover by sending a HANDOVER REQUIRED message to MSC. After receiving this

message, MSC sends a HANDOVER REQUEST message to target BSC. The target

BSC receives this message, and starts the preparation of new channel.

Measuring point: During the procedure of inter BSC handover, the target BSC receives

HANDOVER REQUEST from MSC.

2. Attempted incoming inter BSC inter cell handovers

Description: During the procedure of inter BSC handover, on reception of HANDOVER

REQUEST from MSC, the target BSC will pack this message into IntoBSC Handover

Request to be transferred to the BM of the target cell. This item measures the times of

the current cell receiving IntoBSC Handover Request.



Page7, Total26

Measuring point: During the procedure of inter BSC handover, the target cell (current

cell) receives IntoBSC Handover Request.

From the description of the two statistical items, the statistics at the cell level concerns

the process of the packing for the target cell. If there is an error in the handover data at

the MSC, which sends the handover requests to a wrong target BSC, "BSC

performance measurement" counts the request. However, the target BSC cannot pack

the wrongly sent message to the module of its cell and the cell does not count it in its

statistics. Thus, the disparity arises. Above all, the problem is caused by the errors in

the MSC handover data.

Problem 294 How is the GT800 frequency number defined in

the system?

Problem How is the GT800 frequency number defined in the system?

Descriptio

n

1. The frequency band for GT800 is 851–866MHz (DL). Question: Are there the

definitions of the frequency ID in the system data as in GSM900, namely, DL

frequency = 851.2+(n–1)*0.2, frequency number n=1, 2, 3, 4…75?

2. How is the frequency number of EGSM and RGSM defined?

Reply 1. GT800 frequency coding

Frequency ID Frequency Band (MHz) Formula

350–425 UL: 806–821

DL: 851–866 Fl(n)=0.2*(n–350)+806 Fu(n)=fl(n)+45

The frequencies within this range are numbered in the bitmap format.

2. EGSM frequency coding


974–1023 UL: 880–890



Page8, Total26

DL:925–935 Fl(n)=0.2*(n–1024)+890; Fu(n)=fl(n)+45

0≤n ≤124 UL: 890–915

DL: 935–960 Fl(n) = 0.2*n + 890; Fu(n)=fl(n)+45

3. RGSM frequency coding


974-1023 UL: 880–890

DL: 925–935 Fl(n)=0.2*(n–1024)+890； Fu(n)=fl(n)+45

0≤n ≤124 UL: 890–915

DL: 935–960 Fl(n) = 0.2*n + 890 ； Fu(n)=fl(n)+45

954-973 UL: 876–880

DL: 921–925 Fl(n)=0.2*(n–1024)+890 Fu(n)=fl(n)+45

The rules for coding RGSM and those for coding EGSM are the same.

Problem 295 In which type of bit map are frequencies in

EGSM/RGSM band numbered?

Problem In which type of bitmap are frequencies in EGSM/RGSM band numbered?

Descriptio

n

In which type of bitmap are frequencies in EGSM/RGSM band numbered?

Reply Following are the six types of cell channel description, which are determined by the

second byte in Cell Channel description Format ID (bit8、bit7、bit4、bit3、bit2). See

bellow:

Bit

8 Bit

7 Bit

4 Bit



Page9, Total26

3 Bit

2 Format notation

0 0 X X X bit map 0

1 0 1 1 1 variable bit map

1 0 0 X X 1024 range

1 0 1 0 0 512 range

1 0 1 0 1 256 range

1 0 1 1 0 128 range

The absolute numbers of the frequencies of the cells related to different types of the

channel description format are different. The matching rules of each coding scheme

are as follows:

Coding scheme Matching rules

Bit map 0 Applied to P-GSM900. The actual number of frequencies

of the cells to be configured can reach 64. The frequencies can be chosen randomly

so long as they satisfy 1≤arfcn(i)≤124.

Variable bit map The actual number of frequencies of the cells that can be

configured can reach 64 and they must satisfy the following requirements: With the

1024 frequencies forming a ring, the frequencies to be configured all concentrate

within the 112 neighboring frequencies, including frequency 112 if possible.

1024 range The actual number of frequencies of the cells that can be configured:

n≤16, with frequency 0 not included. The frequencies can be chosen randomly;

The actual number of frequencies of the cells that can be configured: n≤17, with

frequency 0 included. The frequencies can be chosen randomly.

512 range The actual number of frequencies of the cells that can be

configured: n≤18 and the frequencies must satisfy the following requirements: With

the 1024 frequencies forming a ring, the frequencies to be configured all

concentrate within half of the ring, not including those falling on the half ring.



Page10, Total26


configured: n≤22 and they must satisfy the following requirements: With the 1024

frequencies forming a ring, the frequencies to be configured all concentrate within a

quarter of the ring, not including those falling on the quarter ring.


configured n≤29 and they must satisfy the following requirements: With the 1024

frequencies forming a ring, the frequencies to be configure all concentrate within

the eighth of the ring, not including those falling on the eighth ring.

The frequency coding format in EGSM/RGSM band is not fixed, the selection of

which depends on the number of frequencies and the maximum frequency gap. The

maximum frequency gap = the highest frequency – the lowest frequency.

The priority level of the bit maps in the program:

(a) Bit map 0

(b) Variable bit map

(c) 1024 range

(d) 512 range

(e) 256 range

(f) 128 range

The judgment of another bit map starts only when the present bit map does not

satisfy the requirements.

Therefore , the system stipulates that the set of all the frequencies in the cell must

satisfy one of the following requirements in configuring EGSM/RGSM frequencies:

Requirement 1: the lowest frequency>0, and the highest frequency≤124 (With this

satisfied, the system adopts "bit map 0".)

Requirement 2: the maximum frequency gap≤111 (With this satisfied but

Requirement 1 not satisfied,, the system adopts "variable bit map".)



Page11, Total26

Requirement 3: the number of frequencies≤16, or the number of frequencies =17 with

lowest frequency as 0 (With this satisfied but Requirement 1, 2 not satisfied, the

system adopts "1024 range".)

Requirement 4: the number of frequencies≤18, and the maximum frequency gap<512

(With this satisfied but Requirement 1, 2, 3 not satisfied, the system adopts "512

range".)


(With this satisfied but Requirement 1, 2, 3, 4 not satisfied, the system adopts "256

range”.)


(With this satisfied but Requirement 1, 2, 3, 4, 5 not satisfied, the system adopts "128

range”.)

Problem 296 Is there a quantification calculation model for the

effect of transmit power on coverage?

Problem Is there a quantification calculation model for the effect of transmit power on

coverage?

Descriptio

n

Is there a quantification calculation model for the effect of transmit power on

coverage?

Reply According to the radio propagation model Okumura_Hata frequently used in

GSM900, the following approximate analytic equation can indicate the value of urban

path loss:

Lp = 69.55 + 26.16 lg f–13.82 lg hb+ (44.9–6.55 lg hb ) lg d –Ahm

In the equation,

Lp : the path loss from the base station to the mobile station, unit: dB

f : the carrier frequency, unit: MHz



Page12, Total26

hb: the antenna height at the base station, unit: m

hm: the antenna height at the mobile station, unit: m

d: the distance between the base station and the mobile station, unit: km

Modification for small and medium sized cities, Ahm = (1.1lg f –0.7)hm – (1.56lg f

– 0.8)

Modification for large cities, Ahm = 3.2 (lg( 11.75 hm) )2 – 4.97

The propagation model modification for suburbs:

Lps = Lp(urban)–2[lg (f /28)]2- 5.4

The propagation model modification for rural open fields:

Lpo = Lp(urban)–4.78(lg f)2 + 18.33 lg f–40.98

Hence,

ΔLp={69.55 + 26.16 lg f–13.82 lg hb+ (44.9–6.55 lg hb ) lg d1–Ahm }

–{69.55 + 26.16 lg f–13.82 lg hb+ (44.9–6.55 lg hb ) lg d2 –Ahm }

= (44.9–6.55 lg hb ) lg (d1/d2)

From the calculation, when the common hb is sampled in the range 20 m–70 m, the

coverage distance d will be reduced to 81%–82%, the path loss Lp will be reduced by

about 3dB. Other sampling cases of hb can be inferred in the same way.

Therefore, we can conclude by the calculation of the Okumura_Hata propagation

model that:

In case GSM900 radio network with the antenna height of the base station in the

range 20 m–70 m and other conditions unchanged, if the transmit power of the base

station is reduced by 3dB and the coverage distance will shrink to 81%–82% of the

original.

Problem 297 Component indexes of CDU at BTS312

Problem Component indexes of CDU at BTS312



Page13, Total26

Descriptio

n

The client wants to know about the component indexes CDU at BTS312: (bandpass

filter loss, LNA gain, divider loss)

Reply The indexes of the Huawei BTS312:

Total gain of the CDU receive channels: 16dB (the maximum value when the power

attenuation factor is 0dB)

(The indexes of components:

Receive filter loss: –1.2dB;

LNA gain: 16+1.2+10 = +27.2dB;

Divider loss: –10dB)

Reference: typical value of the CDU transmit channel: 4.5dB.

Remarks: It is difficult to test the LNA inside the CDU module. The total gain of the

CDU receive channels is the total gain of the input/output port of the module, which is

related to the power attenuation factor.

The common power attenuation factor (PAD) sampling range: 0 dB–15 dB, default

value 0 dB, can be set at will. The total gain: 16–PAD.

Problem 298 Are there any special requirements for the

separation angle between cells at the same base station?

Problem Are there any special requirements for the separation angle between cells at the

same base station?

Descriptio

n

Are there any special requirements for the separation angle between cells within the

same BTS in GSM? For neighboring cells at the same base station, for example, the

antenna horizontal lobe is 65® and there is no problem if they are 40® apart. Will

there be spurious emission or cross-modulation interference?

Reply The guide stipulates that the separation angle between cells should be over 60®



Page14, Total26

because if it is too small, too much area of the two cells will overlap and this will lead

to frequent cell reselection, and the signal will fluctuate greatly. Such case exists that

in the same base station, two cells cover the areas of the same direction. The tilt

angle of Cell 1 is very low to cover the near villages; Cell 2 covers the scenic area on

the slope in the distance. You can adjust the angle according to the actual need,

which has nothing to do with spurious emission or cross-modulation.

Problem 299 Questions about the “Inter-layer Handover

Threshold” and “Inter-layer Handover Hysteresis”

Overview Questions about the “Inter-layer Handover Threshold” and “Inter-layer Handover

Hysteresis”

Details Do the inter-layer handover threshold and hysteresis adopted in 16 Bit sorting belong to

serving cell or the neighboring cell? Is it possible that the change of the inter-layer

handover threshold and hysteresis of 1800M cell in dualband networking can enable

1800M cell to load traffic?

Answer 1. The inter-layer handover threshold and hysteresis adopted in 16bit sequence for

the serving cell and the neighboring cells are those defined respectively in BSC data

configuration for both cells. The two parameters are described in the internal cell data

table for BSC internal cells and in the external cell data table for external cells.

2. In dualband networking, it is possible to adjust the CRO cell parameters and give

priority for the higher layer in 1800M cells. And it is also possible to lower the

inter-layer HO threshold and hysteresis of the 1800M cell or to increase the

inter-layer HO threshold and hysteresis of the 900M cell. This is because the

adjustment of inter-layer HO threshold and hysteresis might have great influence on

16 bit sorting (Bit 14). After the setup above, the receiving level of 1800M cell

complies with the demand of inter-layer HO threshold and hysteresis and is sorted in



Page15, Total26

priority. The inter-layer HO threshold must not be below the Edge HO threshold.

Otherwise, Ping-Pong handover might occur. In theory, the 16 Bit sorting of 900M

cells can be lowered by setting its HO threshold. and hysteresis higher and the edge

HO to 900M cell is therefore unlikely to occur on the mobile. MS can be kept in

1800M cell. However, the MS might be hindered from handover to the neighboring

cell of 900M cell through edge HO and the session might be of poor quality or even

drop if the inter-layer threshold and hysteresis of the 900M cell is increased too

much.

Suppose the inter-layer HO threshold and hysteresis of the 900M cell is 25/3 and the

layer is 3, the inter-layer HO threshold of the 1800M cell is 20/3 with the layer 2, the

sorting of the neighboring cells is as follows:

No. The Serving

cell The neighboring cell The

Receiving level

Of the serving

cell The Receiving

Level Of

The Neighboring

cell The serving Cell Bit14 The neighboring cell

bit14 HOs triggered 1 900 1800 >-88 >-87 0 0 Inter-layer HO 2 900 1800 >-88 <-87 0 1 None 3 900 1800 <-88 >-87 1 0 Inter-layer HO 4 900 1800 <-88 <-87 1 1 Edge HO (rare) 5 1800 900 >-93 >-82 0 0 None 6 1800 900 >-93 <-82 0 1 None



Page16, Total26

7 1800 900 <-93 >-82 1 0 Edge HO (great possibility) 8 1800 900 <-93 <-82 1 1 Edge HO(rare)

Note:

(1) The HOs in the table above include edge HO or inter-layer HO, exclude the

emergency HOs which might occur. The sorting for emergency HOs is done

according to the receiving level of the neighboring cells.

(2) PBGT handover does not occur because 1800 cells and 900 cells have the

different layer, but emergency HOs, edge HOs and load HOs might occur between

1800M cell and 900M cell.

(3) Edge HOs are prior to inter-layer HOs. The prerequisite for inter-layer handover is

that the serving cell does not reach the edge handover threshold.

Problem 300 The interval of HOs in dualband network

Overview Questions about the interval of HOs in dualband network

Details Q 1: How long is the interval for the initial handover under the following situation?

How to calculate it? What is the function of the parameters such as “Min interval

for TCH HOs”, “Filter length for TCH level”, and “Edge HO watch time”?

1. The parameter “Min interval for TCH HOs” in the [Handover control data

table]: 6 seconds.

A timer must be started when a new TCH channel is assigned. Handover is

possible only when the timer is expired and the parameter “Min interval for TCH

HOs” is the time limit of the timer.

2. In the [Filter Data Table], the parameter “Filter length for TCH level” is 6. This

parameter indicates the number of MRs to be used to do TCH signal strength

averaging calculation.



Page17, Total26

3. “Edge HO watch time” is 4/3 second.

4. “Sent Frequency of preprocessed MR”: 1 time per second, 15:1 configuration.

Q 2:

How to shorten the time of the initial handover?

Q 3:

When the “Sent Frequency of preprocessed MR” is one time per second and

configured as 15:1, is it possible to change the parameter “Filter length for TCH

level” to 3 which means 3 MRs are to be sent within 3 seconds?

Answers Answer to Q1:

The time limit is the minimum interval of the initial TCH handover. That is,

handover is not to occur even when the PN criterion is satisfied. When the

session goes beyond the limit, the time limit is invalid.

“Filter length for TCH level” functions during the average of the MR. If the

parameter is 6, make average of the MRs from NO.1 to No.6 to get a filter

measurement report.

“Edge HO watch time is 4/3” indicates that three of four MRs within four

seconds must satisfy the handover demand if one survey report comes at a

second in a succession of filter MRs.

The first initial handover can be triggered only when the three terms above

are satisfied. The last two terms must be satisfied for sessions that last long.

This is the PN criterion.

Answer to Q2:

“Min interval for TCH HOs” can be shortened to 2 or 4 second, or the PN can

be set as 2/3, or the filter length is set as 4.

Answer to Q3:

Yes. The value of parameters are defined in Network Planning Data

Configuration Criteria.

Besides, when the “Sent Frequency of preprocessed MR” is one time per second



Page18, Total26

and configured as 15:1, increase handover speed by following the answers to Q2

and shorten the “filter length for TCH level” because one MR is reported by BTS

every time.

Problem 301 The influence of half-rate on dualband

cooperation and traffic balance

Overview The influence of half-rate mode on dualband cooperation and traffic balance

Details The GSM 900M in Place A belongs to N manufacturer network while 1800M

belongs to Huawei Network. If half-rate is adopted for 900M network, is there any

impact on the dualband cooperation and traffic balance? How to remake the

handover strategy?

Answers 1. Generally speaking, the half-rate mode adopted for 900M does not have much

influence upon the dualband handover. When inter BSC handover in one MSC

occurs, MSC is to determine whether the full-rate or half-rate channel is assigned

according to the support capacity of MS. If the outgoing handover at 1800M

request for full rate, but only idle half-rate rather than idle full-rate channel is

avialble for target cell at 900M, and MS does not support half-rate, the outgoing

handover fails.

2. The traffic capacity increase tremendously after the half-rate mode is adopted

in 900M network. The former traffic balance strategy might be adjusted

accordingly. Meanwhile, the parameters for HO threshold and dualband

cooperation must be adjusted according to the new strategy of traffic balance.

If the traffic balance strategy demands the 900M network load the traffic as many

as possible, set the cell selection and reselection parameters and make MS stay

at 900M network when it is idle. Make the 900M to 1800M HO parameters difficult

for handover and the 1800M to 900M HO parameters easier for handover.



Page19, Total26

If the traffic balance strategy demands that both the 900M and 1800M networks

load the traffic with 1800M system sharing more traffic, the cell selection and

reselection parameters for both networks are set freely. Meanwhile, make the

900M to 1800M HO parameters easy for handover and the 1800M to 900M

parameters difficult for handover.

Problem 302 Why does dualband handover demand A

interface support PHASE 2 or above?

Overview Why does dualband handover demand A interface support PHASE 2 and above?

Details Why does dualband handover demand A interface support PHASE 2 and above?

Answer Dualband handover demands that A interface support PHASE 2 and above because

it must support the message of “Mobile Station Classmark 3”.

The message types for A Interface PHASE1/PHASE2/PHASE2+:

ELEMENT PHASE1 PHASE2 PHASE2+

Classmark information type 2 Support Code modification of CLASSMARK 2Support Classmark information type 3 Not support new Support Classmark information type 1 Support support Support

Some messages about MS ability such as the power grade, encryption algorithm, MS

short message, multi-band capability are reported by MS CLASSMARK. MS usually

only reports classmark information type 1 or classmark information type 2 to the

network and BSC sends the information through EST IND to MSC. Classmark

information type 1 or classmark information type 2 does not specify whether MS has

multi-band capacity. The multi-band capacity of MS is sent to the network by

classmark information type 3.



Page20, Total26

Problem 303 Does packet paging need to be sent to all the

cells in one LAC of BSC?

Overview Does packet paging need to be sent to all the cells in one LAC of BSC?

details When MS under BSC is called as packet service, SGSN sends PAGING

REQUEST to paging MS, and then PCU handles and sends the PACKET

PAGING to BSC. Then BSC send PACKET PAGING REQUEST to

corresponding cells according to the cell ID.

Question: Does packet paging need to be sent to all the cells in one LAC of BSC?

Answer Packet paging is done according to route area. Each paging is sent downward to

all the cells in the same route. Route area is the subclass of LAC. At present, the

route area is the same as LAC. In the future there can be more than one route

cells under one LAC with the development of data transactions.

There is traffic statistics of the paging times to BSC on the side of PCU.

Problem 304 A question about paging

Overview A question about paging

Details One document file specified that there must be no more than 340 TRXs under one

LAC. Another document file specified that over loading might occur if the total paging

of one LAC exceeds 50000/hour. What is the criterion for the data?

Answer The data requirement such as “there must be no more than 340 TRXs under one

LAC” and “the total paging of one LAC exceeds 50000/hour” is based on certain

terms (traffic model), the BSC processing capability and the software version of that

time. These specifications are no longer practical at the moment.

There is limit to the capacity of Um interfaces and Abis interfaces under one LAC. But

the limit is subject to the subscriber’s traffic mode, the number of subscribers, CCCH



Page21, Total26

configuration, and the network parameters configuration. Reliable data can be

obtained through the calculation of actual data in the network.

Problem 305 How to obtain the CRH for cell reselection across

the LAC?

Overview How to obtain the CRH for cell reselection across the LAC?

Details How to obtain the CRH for cell reselection across the LAC?

Answer The CRH used for cell reselection across the LAC is the data broadcast by the

current serving cell.

The description in GSM protocol is as follows:

The calculated value of C2 for a non-serving suitable cell exceeds the value of C2

for the serving cell for a period of 5 seconds, except in the case of the new cell

being in a different location area in which case the C2 value for the new cell shall

exceed the C2 value of the serving cell by at least

CELL_RESELECT_HYSTERESIS dB as defined by the BCCH data from the

current serving cell, for a period of 5 seconds. This indicates that it is a better cell.

Problem 306 About BCCH TRX aiding

Overview About BCCH TRX aiding

Details BSC fulfills TRX aiding, which is not specified in the guide. The on-site questions is

as follows:

1. Does BSC send the configuration(such as BCCH, BSIC) of the original cell to the

new BCCH TRX (originally TCH) cell when TRX aiding occurs? Does the new

BCCH frequency and BSIC change?

2. Is the function of the cell after TRX aiding consistent with the original one? Is it



Page22, Total26

capable of handover?

3. Describe briefly the principle of TRX aiding and the changes of the cell after the

aiding.

Answer 1. BCCH TRX aiding means that another TCH TRX provides BCCH TRX function

when one BCCH TRX is faulty. That TCH TRX maintains the original BCCH and

BSIC data. The frequency hopping MA of RF hopping remains unchanged. As for

baseband hopping, MA remove the original frequency of the TCH.

2. The function of the cell after the aiding does not change. The faulty BCCH TRX

no longer supports handover, power control and channel allocation.

3. The system will check whether the original BCCH TRX is normal or not in the next

“resource check”. If the TRX is normal, its data and functions will be resumed.

Problem 307 How to make out the No.7 link capacity on

interface A?

Overview How to make out the No.7 link capacity on interface A?

Details The capacity of interface A is dependent on the number of No.7 links configured.

According to IMSI or TMSI paging, each paging at interface A is about 50∼60 bytes. It

is counted as 60 bytes. Paging traffic is only a part of the A interface message. If 5%

of each No.7 link’s capacity is involved in paging, it can support 24,000 pieces of

paging each hour. How is it calculated?

Answer Paging on Interface A=Interface A link rate×3600/8×Interface A

Paging ratio/paging length; as the rate of each No.7 link at the interface A is 64Kbit/s,

each hour 64000*3600/8*5%/60=24,000 pieces of paging are sent.



Page23, Total26

Problem 308 General propagation models adopted for 1800M

network by Huawei

Overview General propagation models for 1800M network by Huawei.

Details What kind of propagation models is adopted for 1800M network by Huawei

Answer 1. COST231-HaTa model expression is adopted in theoretic calculation:

CmHmadHbHbFUrbanL +−−+−+= )(log)log55.69.44(log82.13log9.333.46)(

L(Urban) is the medium value loss (dB) in flat city area

F is frequency, range:1500MHz-2000MHz

Hb is the height of base station antenna (30-200m)

Hm is the height of mobile station antenna (1-10m)

d is propagation distance (1-20km)

a(Hm) is the revision factor of mobile station antenna

Cm = 0dB in medium-size cities or small cities, suburbs.

Cm = 3dB in big cities

2. The model provided in ASSET software by AIRCOM is adopted in systematic

emulation:

Ploss=K1+K2lgd+K3(Hms)+K4lg(Hms)+K5lg(Heff)+K6lg(Heff)lg(d)+K7+Kclutter

In the above expression:

Pathloss: Path loss(dB)

K1: The constant related to frequency

K2: The constant related to distance

K3, K4: The revision coefficient of mobile station antenna height

K5, K6: The revision coefficient of base station antenna height

K7: The revision coefficient of diffraction

Kclutter: The revision coefficient of clutter attenuation

d: Distance between the base station and mobile station (km)

Hms, Heff: Available height of the mobile station antenna and base



Page24, Total26

station antenna (m)

K value parameters for typical cities are as follows:

900M 1800M

City Name Cangzhou Renqiu Chongqing Xian Shenzhen

Jinan

K1 130 132 159 164 164.2 156

K2 38 38 44.9 28.5 45 44.8

K3 1 1 -2.88 -2.88 -2.88 -2.88

K4 0 0 0 0 0 0

K5 -13.55 -13.55 -13.82 -13.82 -13.82 -13.82

K6 -6.3 -6.3 -6.55 -6.55 -6.55 -6.55

K7 1 1 -0.7 0.8 0.21 -0.7

Problem 309 Why is there no description about the influence of

downtilts on coverage in the propagation models?

Overview Why is there no description about the influence of downtilts on coverage in the

propagation models?

Details When we calculate the coverage distance of BTS, we need to know the coverage

receiving level request in preplanning; the maximum path loss is worked out

according to EIRP; and the coverage radius of the base station is worked out

according to the propagation model.

But the real coverage is worked out according to the relative height of the base

station antenna, the vertical half-power angle and the downtilt. Both Hata model and

Cost-231 model seem to neglect the influence of the antenna downtilt on path loss

though the influence is actually remarkable. Is there contradiction?



Page25, Total26

Answer The coverage distance is related with the antenna downtilt. In Hata model and

Cost-231 model we calculate the coverage distance by assuming that there is no

antenna downtilt or the downtilt is very small (The antenna height, azimuth angle,

gains, power and ground object is to be considered). But the ASSET network

planning tools involves prediction of the coverage distance with the fixed downtilt. If

the downtilt is very large, the coverage distance cannot be figured out because the

usual propagation model does not involve the downtilt. The following equation can be

applied in this case: a=arctg(H/D)+b/2.

In this equation:

a is the downtilt;

b is the vertical half-power angle;

H is the antenna height;

D is the coverage distance.

Restriction to the equation: the downtilt must be larger than half

of the vertical half-power angle; D must be shorter than the distance surveyed when

there is no downtilt.

Problem 310 The vertical half-power angle for the small base

station antenna

Overview The vertical half-power angle for small base station antenna

Details The index for small antenna used in BTS3001C is as follows:

Frequency: 890--960MHZ, Gains: 8dBi, Half-power Angle: 65, Preset Downtilt: 0,

How about the vertical half-power angle?

Answer We can use a approximation equation (taken from Huawei GSM Wireless Network

Planning and Optimization) to calculate:

Ga=10log (32400/(α*β))



Page26, Total26

In the equation, Ga is antenna gain (dBi); α is horizontal half-power angle (degree);β

is the vertical half-power angle (degree).

Introduce Ga and α into the equation and β is worked out as 79 degree, and the

actual β given by the manufacturer is about 75 degree.

collection of gsm rnp technical problems and replies(no.15)-20050308-a-1.0

Documents

total26contents problem

dualband network

dualband handover

network indexes

huawei technologies

interlayer handover

product version

wireless network planning