zgo-05!02!008 multi-layer cell structure feature guide zxg10-ibsc (v12.2.0)20130402

ZGO-05-02-008 Multi-layer

Cell Structure

Feature Guide

ZGO-05-02-008 Multi-layer Cell Structure

ZTE Confidential Proprietary 1


Version Date Author Reviewer Notes

V1.0 2012/03/25 Zhao Zhen

GU Commercial

System Supporting

Dept.

Not open to the third party

© 2013 ZTE Corporation. All rights reserved.

ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be disclosed or used

without the prior written permission of ZTE.

Due to update and improvement of ZTE products and technologies, information in this document is subjected to

change without notice.


2 ZTE Confidential Proprietary

TABLE OF CONTENTS

1 Feature Attribute ............................................................................................... 4

2 Overview ............................................................................................................ 4

2.1 Feature Introduction ............................................................................................. 4

2.2 License Control .................................................................................................... 5

2.3 Correlation with Other Features ........................................................................... 5

3 Technical Description ....................................................................................... 6

4 Parameters and Configurations ....................................................................... 9

4.1 Parameter List ..................................................................................................... 9

4.2 Parameter Configuration ...................................................................................... 9

5 Related Counters and Alarms .......................................................................... 9

5.1 Related Counters ................................................................................................. 9

5.2 Related Alarms .................................................................................................. 11

6 Engineering Guide .......................................................................................... 11

6.1 Application Scenario .......................................................................................... 11

6.2 Configuration Description ................................................................................... 11

6.3 Feature Validation .............................................................................................. 11

6.3.1 Multi-layer Cell Structure .................................................................................... 11

6.4 Feature Turn off ................................................................................................. 13

6.5 Network Impact .................................................................................................. 13

7 Abbreviation .................................................................................................... 13

8 Reference Document ....................................................................................... 13



FIGURES

Figure 2-1 Hierarchical cell structure diagram ..................................................................... 5

TABLES

Table 3-1 Typical cell parameters list .................................................................................. 7

Table 3-2 Timer of Micro-Micro function description ............................................................ 8

Table 5-1 Counters list .......................................................................................................... 9



1 Feature Attribute

BSC Version: [ZXG10-iBSC GSM (V6.30.102)]

BTS Version: [Not related with BTS hardware platform]

Property: [Basic]

Related Network Element:

NE Name Related or Not Special Requirements

MS -

BTS √

BSC √

MSC -

MGW -

SGSN -

GGSN -

HLR -

Dependent Function: [ZGB-02-02-001 Basic Handover;ZGO-02-02-001 Handover

between Macro- and Micro-cells,ZGO-02-02-006 Handover Based on Uplink Level

Fast Fading,ZGO-02-02-007 Traffic Based Handover]

Exclusive Function: [None]

Note: [None]

2 Overview

2.1 Feature Introduction

In network planning, cells are divided into 4 layers: umbrella cell, macro cell, micro cell

and pico cell, as shown in Figure 1. Cells in different layers can use the same or different

frequency bands. Hierarchical cell structure is used to solve the problem of heavy traffic



load in hot spots, provide better network performance and service quality and improve

frequency reuse, especially low-level (micro cell and pico cell) frequency reuse.

Figure 2-1 Hierarchical cell structure diagram

2.2 License Control

None license control for this feature in UR12 Release.

2.3 Correlation with Other Features

Correlation with ZGB-02-02-001 Basic Handover:

Correlation with Basic Handover: The handover algorithms in the basic handover are

related to the layers’ concept of hierarchical cell structure. In addition, the parameter

"standard PBGT handover applicable layer (PbgtHoLayer)" should be set for PBGT

handover.

Correlation with ZGO-02-02-001 Handover between Macro- and Micro-cells:



Correlation with Handover between Macro- and Micro-cells: Handover between

Macro- and Micro-cells is related to the layers’ concept of hierarchical cell structure

and the parameter “Neighbor Cell Layer (NCellLayer)” should be set for Handover

between Macro- and Micro-cells.

Correlation with ZGO-02-02-006 Handover Based on Uplink Level Fast Fading:

Correlation with Handover Based on Uplink Level Fast Fading: Related cells set via

OMCR are selected as target cell by Handover Based on Uplink Level Fast Fading. If

related cells are not set, target cell is selected following the rule of upper layer to

same layer to lower layer.

Correlation with ZGO-02-02-006 Handover Based on Uplink Level Fast Fading:

Correlation with Traffic Based Handover: Target cell is selected according to the

hierarchical cell structure of same layer to upper layer to lower layer by Traffic Based

Handover.

3 Technical Description

Generally hierarchical cell structure consists of two or more cell layers. The lowest layer

among multi-layer cell structure is the smallest cell type. Pico cell provides service for

indoor coverage. Micro cell with antenna deployed lower than the building roof or indoor

is used to absorb the traffic in particular region or high-density region. Both pico cell and

micro cell may be overlapped above by macro cell. Macro cell with antenna mounted on

the roof of medium-height building is used to meet the requirement from outdoor users in

urban or rural area, provide continuous coverage and is the main support layer for

network capacity. Finally, the top layer umbrella cell may have satellite beam overlap in

the above-mentioned cell layers or some of their mixed cell layers with antenna set

higher to provide wide area coverage and serve fast-moving or the blind spot area of

low-layer.

The example of some typical cell parameters of these cell layers are shown in Table 1.



Table 3-1 Typical cell parameters list

Cell Type Cell Radius Place of

Installation

Speed of

MS

Target User

Umbrella Cell 100~500km Satellite >500km/h Users in planes

Macro Cell

<35km Top of

buildings/towers <500km/h

User in

fast-moving

vehicles

Micro Cell

<1km Lampposts/Wall

of buildings <100km/h

Walkers or users

in slow-moving

vehicles

Pico Cell <50m Inside buildings <10km/h Indoor users

Different layers can provide different services, so the traffic of fast-moving terminals will

be absorbed by the upper layer and the traffic of slow-moving terminals will be absorbed

by the lower layer. Micro cell or pico cell can provide more spectrum reuse, greater

capacity and allows the use of mobile user device with lower power, as well as lighter

weight. They also provide coverage for the area where the macro cell cannot be

achieved as a result of natural or artificial obstacles. Macro cell is used to cover larger

area with less investment costs, as well as the area where it's difficult for micro cell or

pico cell to cover. When the traffic load is heavy for micro cell or pico cell, macro cell can

provide channel for the overflow traffic.

Handover between different layers is determined by the preset handover thresholds and

handover algorithm and different handover algorithms use different strategies to select

the layer of the target cell.

Layer selection strategy for different handover algorithm is described as follows:

The layer preference is different due to the handover caused by different reasons. The

target cell will be chosen from prior layer first. If there is the target cell that meets the

condition in the priority layer, then it's not needed to find target cell in other layers. If not,

the target cell will be chosen from second prior layer. If finally the target cell that meets

the condition is not founded, then the handover will not be committed.

The concept of layer in this feature is related to handover algorithms.



For Uplink/downlink quality handover, Uplink/downlink level handover, MS-BS

ultra-long-haul handover and Directed Retry, the parameter “Timer of Micro-Micro

handover delay”, shown in Table 2, needs to be set. If the timer is running, select a cell in

the sequence of upper layer–same layer–lower layer; if it is out of time, select a cell in the

sequence of same layer-upper layer-lower layer.

For Handover Based on Uplink Level Fast Fading, when selecting target cells, first select

related cell which is configured on OMCR; if there is no related cell, then select in the

sequence of upper layer - same layer - lower layer.

For Handover between Macro-cells and Micro-cells, it's generally applied to handover

from macro cell to micro cell for slow-moving user in the multi-layer network composed of

macro cells and micro cells, so only the lower layer cells are feasible target cells and the

parameter “Neighbor Cell Layer (NCellLayer)” should be set.

For PBGT handover, there is switch to support inter-layer handover in post-platform

(parameter "standard PBGT handover appropriate layer PbgtHoLayer") and PBGT

handover is only allowed to handover to certain layers via switch setting.

For Traffic Based Handover, when the hierarchy (same layer, upper layer, lower layer),

the band and signal level of a call meet the set requirements of adjacent cell, try to

handover the call to adjacent cell. Hierarchical relation should be set by the parameter

"Traffic handover layer control value TrafficHoLayrCtl" .

Table 3-2 Timer of Micro-Micro function description

No.

Handover Reason Before Tmicro

Timeout

After

TmicroTimeout

1 Signal Quality

(Uplink/Downlink)

Handover

Upper Layer-Same

Layer-Lower Layer

Same

Layer-Upper

Layer- Lower

Layer

2 Signal Level

(Uplink/Downlink)

Handover

Upper Layer-Same

Layer-Lower Layer

Same

Layer-Upper

Layer- Lower

Layer

3 MS-BS Upper Layer-Same Same



Ultra-Distance

Handover

Layer-Lower Layer Layer-Upper

Layer- Lower

Layer

4 PBGT Handover Same layer and

lower layer not

chosen

Same layer and

lower layer not

chosen

5 Handover between

Macro- and

Micro-cells

Handover not

happened

Handover not

happened

4 Parameters and Configurations

4.1 Parameter List

There is no parameter list for this feature

4.2 Parameter Configuration

In order to meet the service requirement, the related function should be opened

according to the parameter configuration description. It should be noted that the bigger

PBGT start threshold is set in handover control, the more easily handover to initiate

5 Related Counters and Alarms

5.1 Related Counters

Table 5-1 Counters list

Counter ID Name



C900060103 Number of incoming handover from undefined layer(GSM900) to

current layer(GSM1800)

C900060104 Number of incoming handover success from undefined

layer(GSM900) to current layer(GSM1800)

C900060105 Number of incoming handover from undefined layer(GSM1800) to

current layer(GSM900)

C900060106 Number of incoming handover success from undefined

layer(GSM1800) to current layer(GSM900)

C900060107 Number of incoming handover from the same layer GSM900 to

GSM1800

C900060108 Number of incoming handover success from the same layer GSM900

to GSM1800

C900060109 Number of incoming handover from GSM900 to GSM1800 from the

upper layer

C900060110 Number of incoming handover success from GSM900 to GSM1800 from

the upper layer


lower layer


the lower layer

C900060113 Number of incoming handover from GSM1800 to GSM900 from the same

layer


the same layer


upper layer


the upper layer




lower layer


the lower layer

5.2 Related Alarms

This feature has no related alarms.

6 Engineering Guide

6.1 Application Scenario

The feature is used in the handover scenario, especially in the traffic-dense areas

6.2 Configuration Description

In order to meet the service requirement, the related function should be opened

according to the parameter configuration description. It should be noted that the bigger

PBGT start threshold is set in handover control, the more easily handover to initiate.

6.3 Feature Validation

6.3.1 Multi-layer Cell Structure

Test Item Multi-layer Cell Structure

Precondition 1. check CN is healthy;

2. check BSC is healthy;

3. check SDR is healthy;

4. check default cell configuration and parameters in



BSC;

5. Cell A,B,C,D,E are ready;

6. Cell C is different frequency band with Cell A.

Test Steps 1. Configure Cell B,C,D,E as adjacent cell of Cell A as

below relation:

a) Cell B as upper layer cell

b) Cell C as same layer cell

c) Cell D as lower layer cell

d) Cell E as undefined layer cell

2. Open BSSAP and RSLCS signaling trace;

3. Set ”The threshold for starting PBGT handover” in

Handover Control as 60 and set ”MIN threshold of

signal level for handover on PBGT” in adjacent GSM

Cell Configuration for all four adjacent cells as 0.

4. Set ”Handover to same layer other band neighbour cell

for PBGT permitted” as 1, ”Handover to upper layer

neighbour cell for PBGT permitted”, ”Handover to

under layer neighbor cell for PBGT

permitted”, ”Handover to neighbour cell with no Layer

Relation for PBGT permitted” As 0

5. MS makes a CS call in cell A, hold on until handover;

6. Set ”Handover to upper layer neighbour cell for PBGT

permitted” as 1 and other three switch as 0


8. Set ”Handover to under layer neighbour cell for PBGT

permitted” as 1 and other three switch as 0


10. Set ” Handover to neighbour cell with no Layer

Relation for PBGT permitted” as 1 and other three

switch as 0

11. MS makes a CS call in cell A;

Anticipative Result 1. MS handover to cell C in step 5

2. MS handover to cell B in step 7

3. MS handover to cell D in step 9

4. MS handover to cell E in step 11

Test Result 1. Handover between multi-layer cells performed

successfully.

Parameters Setting Default parameters



6.4 Feature Turn off

This feature cannot be turn off.

6.5 Network Impact

This feature can make handover in regular, enhance the user perception, improve

the traffic quality, reduce the rate of drop calls, balance the traffic and solve the traffic

congestion for parts of the cells.

7 Abbreviation Abbreviations Full Characteristics

3GPP 3rd

Generation Partnership Project

BCCH Broadcast Control Channel

BSC Base Station Controller

BTS Base Transceiver Station

CS Circuit Switch

HO Handover

PBGT Power Budget

FR Full Rate

CN Core Network

8 Reference Document

ZXG10 iBSC (V6.30.10) Base Station Controller Performance Counter Reference

ZXG10 iBSC (V6.30.10) Base Station Controller Radio Parameter Reference

zgo-05!02!008 multi-layer cell structure feature guide zxg10-ibsc (v12.2.0)20130402

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