GERAN UR13 ZGB-03!02!003 Dynamic Configuration of SDCCH Feature Guide (V4)_V1.0

ZGB-03-02-003 Dynamic

Configuration of SDCCH

Feature Guide

ZGB-03-02-003 Dynamic Configuration of SDCCH

ZTE Confidential Proprietary 1


Version Date Author Reviewer Notes

V1.00 2014/01/22 Shu Yan Gu Yuhui First edition

© 2014 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

3.1 Algorithms for Dynamic SDCCH Configuration .................................................... 7

3.1.1 Descriptions of the Parameters Involved in the Algorithms ................................... 7

3.1.2 Dynamic SDCCH Configuration Standards and Idle TCH Selection Policies ........ 7

3.1.3 SDCCH Decrease and SDCCH Selection Principles ............................................ 8

4 Parameters ......................................................................................................... 9

5 Related Counters and Alarms ........................................................................ 10

5.1 Related Counters ............................................................................................... 10

5.2 Related Alarms .................................................................................................. 12

6 Engineering Guide .......................................................................................... 12

6.1 Application Scenario .......................................................................................... 12

6.2 Feature Activation Procedure ............................................................................. 12

6.3 Feature Validation Procedure............................................................................. 14

6.4 Feature Deactivation Procedure ......................................................................... 14

6.5 Impact on the Network ....................................................................................... 14

7 Abbreviation .................................................................................................... 14

8 Reference Document ....................................................................................... 15



FIGURES

Figure 6-1 GSM Logical Configuration ...............................................................................13

Figure 6-2 GSM Cell Configuration ....................................................................................13

TABLES

Table 2-1 License Control List ............................................................................................ 5

Table 4-1 Parameter List .................................................................................................... 9

Table 5-1 Counter List .......................................................................................................10



1 Feature Attribute

BSC version: [ZXG10 iBSC V6.50.20]

BTS version: [Independent of the BTS hardware platform]

Attribute: [Basic]

Involved NEs:

NE Name Related or Not Special Requirement

MS √ None

BTS √ None

BSC √ None

iTC - None

MSC - None

MGW - None

SGSN - None

GGSN - None

HLR - None

“√”: involved

“-”: not involved

2 Overview

2.1 Feature Introduction

Dynamic SDCCH configuration means the dynamic conversion of TCH to SDCCH if

there are insufficient SDCCH resources but relatively sufficient TCH channel resources

available in the current serving cell. This feature is used to mitigate the shortage of

SDCCH resources and improve the channel utilization rate.



2.2 License Control

Table 2-1 License Control List

Feature ID Feature Name License

Control Item

Configured

NE Unit

ZGB-03-02-003 Dynamic Configuration

of SDCCH None None None

2.3 Correlation With Other Features

1. Required Features

None

2. Mutually Exclusive Features

None

3. Affected Features

Generally, a BCCH carrier is configured with some static SDCCHs for service application,

and the system also provides flexible SDCCH configuration, which means that static

SDCCHs are configured on ordinary carriers other than the BCCH carrier. Dynamic

SDCCH configuration means the conversion of TCH to SDCCH.

This feature correlates with other features as follows:

ZGB-03-02-001 Support of SDCCH/4 and SDCCH/8

ZGB-03-02-002 Flexible SDCCH Configuration



3 Technical Description

Dynamic SDCCH configuration is a policy adopted by the network to allocate channel

resources. If there are no sufficient SDCCH resources available in the current serving

cell, this feature can make full use of the idle TCH resources by converting one idle TCH

to eight SDCCHs to relieve SDCCH congestion.

With dynamic SDCCH configuration enabled, the network periodically checks the

number of idle SDCCHs in the cell based on the SDCCH scanning period set by the

module parameters. If the number of idle SDCCHs is less than the dynamic SDCCH

conversion threshold set by the network, and both the total number of idle TCHs in the

cell and the number of idle TCHs in the first sub-cell are more than four, or the total

number of idle TCHs is more than the number of carriers in the cell, the network selects

randomly one idle TCH and converts it to eight SDCCHs. Similarly, upon the completion

of a dynamic SDCCH conversion, the network continues the conversion of TCH to

SDCCH if the SDCCHs are occupied immediately and the network detects that the

conversion conditions are satisfied when checking periodically the number of idle

SDCCHs in the cell. There is a restriction that one carrier is allowed to be configured with

up to three SDCCHs during a dynamic SDCCH conversion. Therefore, dynamic SDCCH

conversion is related to the planned static SDCCHs. If more than three static SDCCHs

have been planned for a carrier, dynamic SDCCH conversion is impossible on this carrier,

and the network selects another carrier in the cell on the same frequency band with the

BCCH carrier and then attempts a dynamic SDCCH conversion. Version V6.20.200e of

the BSC solves this problem that there is no maximum number of converted SDCCHs on

one carrier.

If the shortage of SDCCH resources in the network is mitigated after a period of time, and

the SDCCH resources are relatively idle for some time, or in other words, the number of

SDCCHs is more than the sum of 8 and the dynamic SDCCH conversion threshold, the

network re-converts the eight SDCCHs back to one TCH and then the dynamic SDCCH

configuration flow is ended. The above-mentioned period of time can be set through the

SDCCH-to-TCH conversion delay in the background. This operation is helpful to prevent

frequent conversions between SDCCH and TCH, which may otherwise cause undesired

consumption of network resources. It should be noted that the SDCCH-to-TCH

conversion occurs only on the cells that generate dynamic SDCCH conversions. In



addition, only the TCHs that have been originally converted to SDCCHs can be

converted back to TCHs.

3.1 Algorithms for Dynamic SDCCH Configuration

3.1.1 Descriptions of the Parameters Involved in the Algorithms

bCanSdcchDyn: It indicates whether dynamic SDCCH configuration is allowed and is

obtained from BSC parameters.

CanSdcchDyn: It indicates whether dynamic SDCCH configuration is allowed and is

obtained from cell parameters.

byMinSdcch: TCH-to-SDCCH conversion threshed, obtained from module parameters

MIN_TCH: minimum number of TCHs in a cell (4)

MIN_SDCCH: minimum number of SDCCHs in a cell (8)

byTimeToTch: SDCCH-to-TCH conversion delay, obtained from module parameters

scanSDCCH: scanning period

Of channel combination types, TCH/F is the most widely used for implementation

feasibility and convenience.

3.1.2 Dynamic SDCCH Configuration Standards and Idle TCH Selection

Policies

The control process collects statistics on channel occupation in each cell based on the

scanSDCCH period. These statistics mainly involve the number of idle TCHs and the

number of idle SDCCHs.

In accordance with the dynamic SDCCH standards, dynamic TCH-to-SDCCH

configuration is started in a cell when the cell meets the following conditions:

1. Dynamic SDCCH configuration is allowed, that is, the values of bCanSdcchDyn (for

the module) and ScanSdcchDyn (for the cell) are both TRUE.



2. The number of idle SDCCHs in the cell is smaller than the byMinSdcch threshold.

3. The difference between the total number of idle TCH/Fs and the total number of idle

reserved TCH/Fs in the cell, and the total number of idle TCH/Fs in the first sub-cell

are both larger than MIN_TCH or the total number of TRXs in the cell.

The policies of selecting an idle TCH/F during the configuration are as follows:

1. The network selects a TCH on the same frequency band as the BCCH carrier. For

example, if the BCCH carrier is in P-GSM, it is not allowed to select an E-GSM or

R-GSM extended frequency point or 1800M TCH.

2. The network selects a static TCH/F first, and then a dynamic TCH/F.

3. The network selects a TCH with the worst interference.

4. The network selects a TCH from the first sub-cell.

The converted TCH timeslot is included in the conversion queue.

3.1.3 SDCCH Decrease and SDCCH Selection Principles

If it is detected that a cell meets certain conditions, an SDCCH-to-TCH conversion starts

and the SDCCH is selected from the timeslots configured as SDCCHs derived from

TCH/Fs.

The principles to decrease the number of SDCCHs are as follows (the initial value of S is

equal to byTimeToTch):

1. If the number of idle SDCCHs in a cell is equal to the sum of MIN_SDCCH and

byMinSdcch, no action is required.

2. If the number of idle SDCCHs in a cell is smaller than the sum of MIN_SDCCH and

byMinSdcch, S+ = 12 is selected (not more than byTimeToTch).

3. If the number of idle SDCCHs in a cell is larger than the sum of MIN_SDCCH and

byMinSdcch, S- = 3 is selected.

If S is smaller than or equal to 0, an SDCCH-to-TCH conversion is triggered one time.



4 Parameters

Table 4-1 Parameter List

Manage

d

Object

Logic

Name Parameter Description Value Range Unit

Defaul

t

Value

Reco

mmen

ded

Value

BSC,CE

LL

Dynami

c

Configur

ation

SDCCH

This parameter indicates

whether dynamic SDCCH/TCH

conversion is enabled in the

BSC. The network can

dynamically perform

conversions between SDCCH

and TCH when this function is

enabled. Another prerequisite

of successful dynamic

DCCH/TCH conversion in a cell

is that this function is also

enabled in the cell.

0:No

1:Yes None 0 1

BSC Scan

SDCCH

This parameter indicates the

period of scanning idle

SDCCHs when the dynamic

SDCCH/TCH conversion

function is enabled in a cell.

After the dynamic SDCCH/TCH

conversion function is enabled

in a network, the network scans

SDCCHs at the period

specified by this parameter to

find the number of idle

SDCCHs for determining

whether to convert SDCCH

back to TCH.

10~1000 100ms 100

BSC

TCH->S

DCCH

Limit

This parameter specifies the

threshold that triggers a

TCH-to-SDCCH conversion in

a cell where SDCCH dynamic

configuration is enabled. When

2~64 None 4



Manage

d

Object

Logic

Name Parameter Description Value Range Unit

Defaul

t

Value

Reco

mmen

ded

Value

the number of idle SDCCHs is

lower than this threshold, a

TCH to- SDCCH conversion is

performed.

BSC

SDCCH

->TCH

Delay

This parameter is used to

enable dynamic SDCCH

configuration function in the

cell. After TCH is dynamically

converted to SDCCH channel

and SDCCH channel is idle, to

prevent from frequent channel

conversion, a time limit will be

added for the conversion from

SDCCH channel to TCH

channel. During this limit,

SDCCH channel cannot be

converted to TCH channel.

0~24 None 0

BSC

Minimu

m Tch

reserve

d for

dynamic

SDCCH

If dynamic SD conversion is

enabled, the conversion

TCH->SDCCH requires

checking the number of idle

TCHs in the cell and No. 1

sub-cell. If the number is

greater than MinTch, the

switchover is allowed.

1~64 None 0

5 Related Counters and Alarms

5.1 Related Counters

Table 5-1 Counter List

Counter ID Name



C901250001 Number of SDCCH seizure attempts for

assignment(Times)

C901250002 Number of SDCCH seizure success for

assignment(Times)

C901250003 Number of SDCCH seizure failure for

assignment(Times)

C901250004 Number of SDCCH seizure attempts for

handover(Times)

C901250005 Number of SDCCH seizure success for

Handover(Times)

C901250006 Number of SDCCH seizure failure for handover(Times)

C901250007 Number of SDCCH allocation attempts for

assignment(Times)

C901250008 Number of SDCCH allocation success for

assignment(Times)

C901250009 Number of SDCCH allocation failure for

assignment(Times)

C901250010 Number of SDCCH allocation attempts for

handover(Times)

C901250011 Number of SDCCH allocation success for

handover(Times)

C901250012 Number of SDCCH allocation failure for

handover(Times)

C901250013 Number of SDCCH assignment attempts(Times)

C901250014 Number of SDCCH assignment success(Times)

C901250015 Number of SDCCH assignment failure(Times)

C901250016 Number of SDCCH handover attempts(Times)

C901250017 Number of SDCCH handover success(Times)

C901250018 Number of SDCCH handover failures with the handover

failure message returned from MS(Times)

C901250019 Number of SDCCH handover failure without the

handover failure message returned from MS(Times)



5.2 Related Alarms

This feature has no related alarm.

6 Engineering Guide

6.1 Application Scenario

A short message group sends a large number of location update messages and

therefore occupies SDCCH resources.

The multi-paging mode configured on the network side consumes large amount of

SDCCH resources.

A dynamic SDCCH conversion should be activated for the cells at the edge of the

location area because there are many location updates.

A dynamic SDCCH conversion is needed if SDCCHs are congested while TCHs are idle.

6.2 Feature Activation Procedure

1. In the configuration resource tree, select Modify Area > Managed Element and

double click GSM Logical Configuration, see the following figure.



Figure 6-1 GSM Logical Configuration

2. In the configuration resource tree, select Modify Area > Managed Element > GSM

Logical Configuration > Cell Information Configuration, double click GSM Cell

Configuration, and configure Dynamic configuration SDCCH, see the following

figure.

Figure 6-2 GSM Cell Configuration



6.3 Feature Validation Procedure

Test Item Dynamic SDCCH

Prerequisite 1. The CN is in good condition.

2. The BSC is operating properly.

3. The SDR is operating properly.

4. The default cell configuration and parameter

configurations are correct in the BSC.

5. The MSs are ready for the test.

6. The radio environment is good.

Steps 1. On the GSM Cell Configuration tab, set

CanSdcchDyn to YES.

2. On the GSM Logical Configuration tab, set Dynamic

config SDCCH to Yes, Scan SDCCH to 10, and

TCH->SDCCH limit to 2.

3. Block all SDCCHs in the cell.

4. The MS makes a call in the cell and holds on.

5. Check the configuration of Cell Channel Management

in dynamic data management.

Expected Result 1. The call can be established in the cell.

2. In cell channel management, the number of converted

SDCCHs can be calculated correctly.

6.4 Feature Deactivation Procedure

This feature is enabled with the switches at the cell level and the BSC level, and disabled

at the cell level or the BSC level.

6.5 Impact on the Network

When this feature is enabled, network congestion on SDCCHs can be greatly relieved.

7 Abbreviation Abbreviation Full Name



3GPP 3rd Generation Partnership Project

SDCCH Stand-Alone Dedicated Control Channel

GSM Global System for Mobile communications

BSC Base Station Controller

BTS Base Transceiver Station

MS Mobile Station

MSC Mobile Switching Centre

8 Reference Document

ZXUR 9000 GSM (V6.50.20) Base Station Controller Performance Counter Reference

ZXUR 9000 GSM (V6.50.20) Base Station Controller Radio Parameter Reference

Documents

GERAN UR13 ZGB-03!02!003 Dynamic Configuration of SDCCH Feature Guide (V4)_V1.0