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ZGO-04-02-003 Discontinuous

Transmission Downlink

Feature Guide


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ZGO-04-02-003 Discontinuous Transmission Downlink

ZTE Confidential Proprietary 2010 ZTE CORPORATION. All rights reserved. I


Version Date Author Approved By Remarks

V1.00 2010-10-30 Not open to the Third Party

2010 ZTE Corporation. All rights reserved.

ZTE CONFIDENTIAL:This document contains proprietary information of ZTE and is not to bedisclosed or used without the prior written permission of ZTE.

Due to update and improvement of ZTE products and technologies, information in this document issubjected to change without notice.


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ZTE Confidential Proprietary 2010 ZTE CORPORATION. All rights reserved. II

TABLE OF CONTENTS

1 Feature Attribution ......................................................................................... 12 Overview ......................................................................................................... 12.1 Feature Introduction .......................................................................................... 12.2 Correlation with Other Features ........................................................................ 23 Technical Description .................................................................................... 24 Parameters and Configurations..................................................................... 34.1 Parameter List .................................................................................................. 34.2 Parameter Configurations ................................................................................. 35 Related Counters and Alarms ........................................................................ 55.1 Related Counters .............................................................................................. 55.2 Related Alarms ................................................................................................. 56 Engineering Guide .......................................................................................... 66.1 Application Scenarios ....................................................................................... 66.2 Configuration Description.................................................................................. 66.3 Network Impact ................................................................................................. 67 Abbreviation .................................................................................................... 68 Reference Document ...................................................................................... 7


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ZTE Confidential Proprietary 2010 ZTE CORPORATION. All rights reserved. III

FIGURES

Figure 4-1 Configuring Downlink DTX Feature 1 .................................................................. 4Figure 4-2 Configuring Downlink DTX Feature 2 .................................................................. 5

TABLES

Table 4-1 Parameter List ................................................................................................... 3


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ZTE Confidential Proprietary 2010 ZTE CORPORATION. All rights reserved. 1

1 Feature Attribution

iBSC Version: [iBSC V6.20]

BTS Version: [No requirements of BTS software and hardware platform]

Property: [Optional]

Related Network Elements and Requirements:

NE Name Related or Not Special Requirements

MS

BTS

BSC

MSC -

MGW -

SGSN -

GGSN -

HLR -

Dependent Function: [None]

Exclusive Function: [None]

Note: [None]

2 Overview

2.1 Feature Introduction

In the process of a normal speech conversation, average speech activity is typically

around 40% of the duration. When the subscribers are in the conversation status but

transfer no speech message, MS or BTS will not send any sampled speech frame, but


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send only a few comfort noisesframe. The purpose of the function is to reduce downlink

interference in the radio network and to decrease BTS power consumption.

2.2 Correlation with Other Features

Discontinuous transmission (DTX) is applied only to speech frame, and supports FR and

HR modes. Downlink DTX works with uplink DTX (ZGO-04-02-004 Discontinuous

Transmission_Uplink) and frequency hopping (ZGO-04-03-004 Baseband Frequency

Hopping, ZGO-04-03-001 Synthesized Frequency Hopping) to minimize system

interference.

3 Technical Description

Network needs to make Voice Activity Detection (VAD) on speech frame from CN to

estimate the background noise condition of speech frame and send comfort noise

characteristic value to cell phone part. The special frame to send comfort noise is called

Silence Descriptor (SID). SID frame always follows a speech frame to label the

completion of speech frame. In addition, to update comfort noise characteristic value for

receiving end during long-time speech intermission, transmitter sends SID frame at fixed

intervals. This mechanism enables testing more precisely on wireless link level and

quality during receiving end applying DTX with the parameter DtxDwlink.

VAD technology is a part of speech coder of transmitter, it is used to detect the input at a

moment is voice or noise. It distinguishes between voice and noise on the principle: noise

energy is always lower than voice energy. VAD compares the measured filter signal

energy and the threshold defined to judge voice or background noise is contained in each

output frame.

The noise codec process is basically identical to the speech codec, they experiences

same channel coding, interleaving, encryption, and modulation, then to be sent to

wireless interface.


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Subset in one measurement period (104 multi-frames, 480ms) has to be sent out with

contents for cell phone testing downlink level and quality or updating comfort noise

characteristic value (when sending SID frame).

4 Parameters and Configurations

4.1 Parameter List

Table 4-1 Parameter List

Full name Downlink discontinuous transmission allowed

Abbreviation DtxDwlink

Description

DTX mode is an optional downlink feature of GSM System.

The Discontinuous Transmission (DTX) mode means that the system

does not transmit signals during the speech intermission of the

subscriber conversation. This parameter participates in determining

to use DTX mode in downlink direction.

Actually, using DTX in downlink direction (in CHANNEL ACTIVATION

message and MODE MODIFY message sent to BTS) is determined

together by this parameter and the DTX indication in downlink

direction in ASSIGNMENT REQUEST message and HANDOVER

REQUEST message of MSC.

Yes: enable;

No: disable

Value Range Yes/No

Unit None

Default No

Management

ObjectCell

4.2 Parameter Configurations

Operating steps:


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1 In navigation tree, right-click OMC GERAN Subnetwork BSC Managed NE

Config Set IDBSC Global Resource IDBTS ConfigurationBTS IDCreate

Cell, as shown in Figure 4-1:

Figure 4-1 Configuring Downlink DTX Feature 1

2 Click Cell, set Downlink Discontinuous Transmission AllowedtoYes in Optional

Paramsin Create Celltab, as shown in Figure 4-2:


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Figure 4-2 Configuring Downlink DTX Feature 2

Note: When A over IP, downlink DTX function will be invalid. Downlink DTX function will

be enabled at CN side, not BSC side.

5 Related Counters and Alarms

5.1 Related Counters

None

5.2 Related Alarms

None


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6 Engineering Guide

6.1 Application Scenarios

Activation of DTX feature is recommended in all scenarios.

6.2 Configuration Description

This feature does not involve iBSC and BTS hardware configuration adjustment.

6.3 Network Impact

This feature reduces downlink interference in network, improves network performance

and decreases BTS transmission power consumption.

It will decrease the voice quality slightly after activation.

This feature does not affect capacity of iBSC and BTS.

7 Abbreviation

Abbreviations Full Characteristics

BFI Bad Frame indicator

BSC Base Station Controller

BTS Base Transceiver Station

DTX Discontinuous Transmission

EDGE Enhanced Data rates for Global Evolution

GSM Global System for Mobile communications

GERAN Gsm/Edge Radio Access Network

MR Measure Report


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MS Mobile Station

MSC Mobile Switching Centre

OMC Operation & Maintenance Center

QoS Quality of Service

SID Silence Description Frame

VAD Voice activation Detection

8 Reference Document

[None]

zgo-04!02!003 discontinuous transmission downlink fg 20101030

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