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BSS B10-B11 Telecom Evolution - Page 1All Rights Reserved Alcatel-Lucent 2010

All Rights Reserved Alcatel-Lucent 2010

GERAN

BSS B10-B11 Telecom Evolution

STUDENT GUIDE

TMO18090 D0 SG DEN Issue 2.0

All rights reserved Alcatel-Lucent 2010Passing on and copying of this document, use and communication of its

contents not permitted without written authorization from Alcatel-Lucent


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BSS B10-B11 Telecom EvolutionGERAN

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Switch to notes view!

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3

Terms of Use and Legal Notices

Switch to notes view!1. Safety WarningBoth lethal and dangerous voltages may be present within the products used herein. The user is strongly advised not to

wear conductive jewelry while working on the products. Always observe all safety precautions and do not work on the

equipment alone.

The equipment used during this course may be electrostatic sensitive. Please observe correct anti-static precautions.

2. Trade Marks

Alcatel-Lucent and MainStreet are trademarks of Alcatel-Lucent.

All other trademarks, service marks and logos (Marks) are the property of their respective holders, including Alcatel-

Lucent. Users are not permitted to use these Marks without the prior consent of Alcatel-Lucent or such third party owning

the Mark. The absence of a Mark identifier is not a representation that a particular product or service name is not a Mark.

Alcatel-Lucent assumes no responsibility for the accuracy of the information presented herein, which may be subject tochange without notice.

3. Copyright

This document contains information that is proprietary to Alcatel-Lucent and may be used for training purposes only. Noother use or transmission of all or any part of this document is permitted without Alcatel-Lucents written permission, andmust include all copyright and other proprietary notices. No other use or transmission of all or any part of its contents may

be used, copied, disclosed or conveyed to any party in any manner whatsoever without prior written permission from

Alcatel-Lucent.

Use or transmission of all or any part of this document in violation of any applicable legislation is hereby expressly

prohibited.

User obtains no rights in the information or in any product, process, technology or trademark which it includes ordescribes, and is expressly prohibited from modifying the information or creating derivative works without the express

written consent of Alcatel-Lucent.

All rights reserved Alcatel-Lucent 2010

4. Disclaimer

In no event will Alcatel-Lucent be liable for any direct, indirect, special, incidental or consequential damages, including

lost profits, lost business or lost data, resulting from the use of or reliance upon the information, whether or not Alcatel-

Lucent has been advised of the possibility of such damages.

Mention of non-Alcatel-Lucent products or services is for information purposes only and constitutes neither an

endorsement, nor a recommendation.

This course is intended to train the student about the overall look, feel, and use of Alcatel-Lucent products. Theinformation contained herein is representational only. In the interest of file size, simplicity, and compatibility and, in some

cases, due to contractual limitations, certain compromises have been made and therefore some features are not entirely

accurate.

Please refer to technical practices supplied by Alcatel-Lucent for current information concerning Alcatel-Lucent equipment

and its operation, or contact your nearest Alcatel-Lucent representative for more information.

The Alcatel-Lucent products described or used herein are presented for demonstration and training purposes only. Alcatel-

Lucent disclaims any warranties in connection with the products as used and described in the courses or the relateddocumentation, whether express, implied, or statutory. Alcatel-Lucent specifically disclaims all implied warranties,

including warranties of merchantability, non-infringement and fitness for a particular purpose, or arising from a course of

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Alcatel-Lucent is not responsible for any failures caused by: server errors, misdirected or redirected transmissions, failed

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5. Governing Law

The products, documentation and information contained herein, as well as these Terms of Use and Legal Notices are

governed by the laws of France, excluding its conflict of law rules. If any provision of these Terms of Use and Legal

Notices, or the application thereof to any person or circumstances, is held invalid for any reason, unenforceable including,

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Terms of Use and Legal Notices shall remain in full force and effect.


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5

Course Outline

About This CourseCourse outline

Technical support

Course objectives

1. Topic/Section is Positioned HereXxx

Xxx

Xxx

2. Topic/Section is Positioned Here






1. BSS B10-B11 Telecom Evolutions

1. Support of Paging Coordination 3JK11693AAAAWBZZA

2. Repeated ACCH 3JK11694AAAAWBZZA

3. NACC for Inter BSS and Inter RAT 3JK11695AAAAWBZZA

4. Tandem Free Operation with AMR-NB 3JK11696AAAAWBZZA

5. Support of A5.3 Ciphering 3JK11697AAAAWBZZA

6. Synchronized Radio Network 3JK11698AAAAWBZZA

7. TRX Dynamic Power Saving 3JK11699AAAAWBZZA

8. Antenna Hopping 3JKxxx

9. Abbreviations 3JKxxx


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6

Course Outline [cont.]




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7

Course Objectives


Welcome to BSS B10-B11 Telecom Evolution

Upon completion of this course, you should be able to:

By the end of the course, participants will be able to describe the new telecom B11

features and their telecom impacts.


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8

Course Objectives [cont.]




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9

About this Student Guide

Switch to notes view!Conventions used in this guide

Where you can get further information

If you want further information you can refer to the following:

Technical Practices for the specific product

Technical support page on the Alcatel website: http://www.alcatel-lucent.com

Note

Provides you with additional information about the topic being discussed.

Although this information is not required knowledge, you might find it useful

or interesting.

Technical Reference(1) 24.348.98 Points you to the exact section of Alcatel-Lucent Technical

Practices where you can find more information on the topic being discussed.

WarningAlerts you to instances where non-compliance could result in equipment

damage or personal injury.


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10

About this Student Guide [cont.]




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11

Self-assessment of Objectives

At the end of each section you will be asked to fill this questionnaire

Please, return this sheet to the trainer at the end of the training


Instructional objectivesYes (orglobally

yes)

No (orglobally

no)Comments

1 To be able to XXX

2

Contract number :

Course title :

Client (Company, Center) :

Language : Dates from : to :

Number of trainees : Location :

Surname, First name :

Did you meet the following objectives ?

Tick the corresponding box

Please, return this sheet to the trainer at the end of the training


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12

Self-assessment of Objectives [cont.]


Instructional objectivesYes (orGlobally

yes)

No (orglobally

no)Comments

Thank you for your answers to this questionnaire

Other comments


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Section 1 Module 1 Page 1


3JK11693AAAAWBZZA Issue 1.0

Do not delete this graphic elements in here:

11All Rights Reserved Alcatel-Lucent 2010Module 1

Support of Paging Coordination3JK11693AAAAWBZZA Issue 1.0

Section 1BSS B10-B11 Telecom Evolutions

GERANBSS B10-B11 Telecom EvolutionTMO18090 D0 SG DEN Issue 2.0


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GERAN BSS B10-B11 Telecom EvolutionBSS B10-B11 Telecom Evolutions Support of Paging Coordination

1 1 2

Blank Page


First editionEljaafari, Mohamed2009-03-3001

RemarksAuthorDateEdition

Document History


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1 1 3

Module Objectives

Upon completion of this module, you should be able to:

Describe the purpose of the "Support of Paging Coordination in the BSS"feature and its Telecom and O&M impacts


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1 1 4

Module Objectives [cont.]



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1 1 5

Table of Contents

Switch to notes view!Page

1 What Is the Purpose of this Feature? 71.1 Paging Coordination Principle in B10 8

1.2 Paging Coordination Principle in B11 112 How Does It Work? 12

2.1 Overall Description 133 What Are the Telecom Impacts? 17

3.1 CS Paging Requests Processing 184 What Are the O&M Impacts? 20

4.1 Feature Activation 214.2 Performance Management 22


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1 1 6

Table of Contents [cont.]




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1 1 7

1 What Is the Purpose of this Feature?


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1 1 8


1.1 Paging Coordination Principle in B10

Do you remember the CS paging coordination in B10?Select the correct statements.

In NMO-II or NMO-III, the MS cannot receive CS paging while in PacketTransfer Mode

The Gs interface is a pre-requisite to fully support the DTM feature

If the network operates in NMO-I, there is no Gs interface between the MSCand the SGSN

In case of NMO-I, the paging coordination is done by the core network(between the MSC and the SGSN)

Paging coordination is an Alcatel-Lucent specific feature


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1 1 9


1.1 Paging Coordination Principle in B10 [cont.]

Without paging coordination, CS Paging messages are always broadcastthrough the CCCH/PCH channel, even if the MS is in PTM mode.

MFS SGSNPDCHs

CSpaging

CSpaging

PCH

PACCH

CSpaging

Serving cell

BSC MSC

WithoutGs interface


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1.1 Paging Coordination Principle in B10 [cont.]

With paging coordination in the SGSN, CS paging messages for GPRS-attached MS are conveyed from the MSC to the SGSN through the Gs

interface. It corresponds to the Network Mode of Operation I (NMO-I).

Serving cell

MFS SGSN

BSC MSC

Gs

TCHDedicated

mode

PACCH

CSpaging

CSpaging

CSpaging

CSpaging

Paging coordinationin the SGSN usingthe Gs interface


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1 1 11


1.2 Paging Coordination Principle in B11

The support of paging coordination improves CS paging performance, asit allows to send CS paging messages through the PACCH.

In B11, this procedure can be fully performed in the BSS.

Serving cell

MFS

BSC MSC

WithoutGs interface

SGSN

PCH

GSL

Dedicatedmode

PACCH

CSpaging

CSpaging

CSpaging

CSpaging

CSpaging

CSpaging

Paging coordinationin the BSSTCH

There are two ways to support paging coordination:

Prior to B11, paging coordination is performed in the SGSN. In such a case, CS paging messages for GPRS-

attached MS are conveyed from the MSC to the SGSN through the Gs interface, which allows the SGSN to

perform the paging coordination. This corresponds to the Network Mode of Operation I.

In B11, paging coordination is performed in the BSS. If no Gs interface is available then CS paging

coordination has to be fully performed in the BSS.


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1 1 12

2 How Does It Work?


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1 1 13

2 How Does It Work?

2.1 Overall Description

With CS paging coordination in the BSS, the BSC has to forward to theMFS CS Paging requests received from the MSC.

Knowing that the BSC is aware of neither the MS location nor the MSmode (PTM or not), and the fact that we have to be very careful withthe GSL load, can you guess which kind of information shall be sent tothe MFS?

Select the correct answer.

Indication about the Paging Area

The cell the MS camps on

List of all cells managed by the BSC

MS Location AreaMS IMSI

PTM/non-PTM mode

Nothing


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1 1 14

2 How Does It Work?

2.1 Overall Description [cont.]

The BSC forwards to the MFS CS Paging requests received from the MSC in orderto allow the MFS to send the paging requests on the PACCH channel.

The BSC also broadcasts all CS paging requests to the MS through the PCHchannel.

Serving cell

MFS

BSC MSC

GSL

SGSN

WithoutGs interface

PCH CSpaging

CSpaging

CSpaging

CSpaging

Paging coordination in the BSS

MS in PIMMFS discards the Paging Request

IMSI

CS paging coordination in the BSS is performed in 3 steps:

1. CS paging requests are received from the MSC.

2. The BSC forwards CS paging requests to the MFS via the GSL (using BSCGP) after filtering. In any case the

BSC also broadcasts all CS paging requests to the MS through the PCH channel (for all cells corresponding to

the Paging Area and managed by the BSC).

3. On receipt of the CS paging requests sent by the BSC and when applicable (i.e. for MS in PTM mode), the

MFS sends these CS paging requests to the MS through the PACCH channel (for the cell the MS camps on).

Management of the IMSI by the MFS

When CS paging coordination is performed in the BSS, no Paging Area is provided within CS Paging Requests

forwarded by the BSC but only the IMSI. Therefore the MFS has to build and maintain a set of IMSI vs MS

Context relationships for all MS in PTM mode.


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1 1 15

2 How Does It Work?

2.1 Overall Description [cont.]

The BSC forwards to the MFS CS Paging requests received from the MSC in orderto allow the MFS to send the paging requests on the PACCH channel.

The BSC also broadcasts all CS paging requests to the MS through the PCHchannel.

Serving cell

MFS

BSC MSC

WithoutGs interface

SGSN

PCHGSL

Dedicatedmode

PACCH

CSpaging

CSpaging

CSpaging

CSpaging

CSpaging

CSpaging

MS in PTM modewill be paged faster on the PACCH

than on the PCH

TCH Paging coordinationin the BSS

CS paging coordination in the BSS is performed in 3 steps:

1. CS paging requests are received from the MSC.

2. The BSC forwards CS paging requests to the MFS via the GSL (using BSCGP) after filtering. In any case the

BSC also broadcasts all CS paging requests to the MS through the PCH channel (for all cells corresponding to

the Paging Area and managed by the BSC).

3. On receipt of the CS paging requests sent by the BSC and when applicable (i.e. for MS in PTM mode), the

MFS sends these CS paging requests to the MS through the PACCH channel (for the cell the MS camps on).

Management of the IMSI by the MFS

When CS paging coordination is performed in the BSS, no Paging Area is provided within CS Paging Requests

forwarded by the BSC but only the IMSI. Therefore the MFS has to build and maintain a set of IMSI vs MS

Context relationships for all MS in PTM mode.


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3 What Are the Telecom Impacts?


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3.1 CS Paging Requests Processing [cont.]

The MFS has to maintain a set of "IMSI vs MS Context" relationships: For an MS which leaves the PTM mode, the corresponding "IMSI vs MS

Context" relationship has to be removed from the set. For an MS which enters the PTM mode, its IMSI has to be retrieved.

In your opinion, how must the IMSI be retrieved?Select the correct answers.

For a DL TBF, pick the IMSI from a DL LLC PDU

The IMSI is retrieved only during GPRS Attach

For a UL TBF, perform an RA Capacity Update procedure

For a UL TBF, perform the two-phase access procedure


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1 1 20

4 What Are the O&M Impacts?


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1 1 21


4.1 Feature Activation

New Parameter

The "Support of Paging Coordination in the BSS" feature is optional. It

shall be activated at BSS level, via the OMC-R:BSS_PAGING_COORDINATION

BSS_PAGING_COORDINATION:

Enables CS Paging Coordination to be managed in the BSS for MS in Packet Transfer Mode.

The default value is "Disabled".

Recommended rules:

If BSS_PAGING_COORDINATION (BSC)/(MFS) is set to "Enabled", it is highly recommended to set

EN_RA_CAP_UPDATE to "Enabled" for all cells of the corresponding BSS.

If DTM is Enabled for at least one cell within a given BSS, it is highly recommended to activate CS Paging

Coordination for this BSS, either through the Gs Interface (network_operation_mode = "NMO I") or by setting

BSS_PAGING_COORDINATION (BSC)/(MFS) to "Enabled" (network_operation_mode "NMO I").

Note

The activation of DTM is NOT a prerequisite to activate the "Support of paging coordination in the BSS"

feature. This feature can be used to simply improve CS paging performance for MS in PTM mode without

having mandatorily DTM in mind.

As Network_Operation_Mode is defined on a per BSS basis, the two ways to perform Paging Coordination

cannot be handled simultaneously for a given BSS. On the other hand, nothing prevents to use both at

Network level.


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1 1 23

Module Summary

If no Gs interface is available then CS paging coordination has to befully performed in the BSS.

With paging coordination in the BSS, the BSC sends all receivedpaging requests from the MSC both to the PCH and to the MFS.

Paging coordination is mandatory to fully support the DTM feature.

This new feature can be useful independently from the DTM.

The two ways to perform paging coordination cannot be handledsimultaneously for a given BSS.

The feature activation is configured from the OMC-R via theBSS_PAGING_COORDINATION parameter.


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1 1 24

Self-assessment on the Objectives

Please be reminded to fill in the formSelf-Assessment on the Objectives

for this module The form can be found in the first part

of this course documentation


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1 1 25

End of ModuleSupport of Paging Coordination


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GERAN BSS B10-B11 Telecom EvolutionBSS B10-B11 Telecom Evolutions Repeated ACCH

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1.1 FACCH and SACCH

Do you remember FACCH and SACCH?Select the corresponding signaling channel.

The FACCH SACCH is associated with a TCH, and is required to support the high-speed signaling needed duringcall establishment and HO management.

The occurrence of the FACCH SACCH is not fixed in the multiframe, as it is for the FACCH SACCH..Insted, the FACCH SACCH occurs on a TDMA frame that is reserved for a TCH.

An FR TCH uses one TS per TDMA frame, for each frame of the multiframe, except for the frames 12 and 25. The TDMA

frame 12 is used to carry the FACCH SACCH and the TDMA frame 25 is an idle frame.

The FACCH SACCH multiframe/block is composed of four FACCH SACCH frames/bursts; thus theFACCH SACCH period is equal to 480ms.

The FACCH SACCH is used mainly for the transmission of the radio measurement data.FACCH SACCH is also used for SMS transfer during a call.

The multiplexing of TCH and FACCH SACCH is possible by means of the frame stealing. This means that a speechframe carried over a TCH can be replaced by an FACCH SACCH frame.

The BTS sends cell-specific information (periodically SYS_INFO 5, 5bis, 5ter, 6) to the MS using FACCH SACCH.


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1.2 Voice and Signaling Coverage without AMR in B10

When AMR speech codecs were introduced, the same Associated ControlChannels (ACCHs) as those used for traditional TCH/FR and TCH/EFR

were re-used. The consequence is that, in poor radio conditions, themore protected AMR speech codecs have now better performance (interms of error rate) than the associated control channels. This resultsin an imbalance between voice and signaling.

Voice andsignaling coverage

without AMR

ZZ

Z

Call Drop

BTS


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1 2 10


1.3 Improved Voice Coverage with AMR in B10

When AMR speech codecs were introduced, the same Associated ControlChannels (ACCHs) as those used for traditional TCH/FR and TCH/EFR

were re-used. The consequence is that, in poor radio conditions, themore protected AMR speech codecs have now better performance (interms of error rate) than the associated control channels. This resultsin an imbalance between voice and signaling.

BTS

Call Drop

Improved voice coveragewith AMR

ZZ

Z

Signaling channelsdesigned at the

beginning of GSMless robust than

AMR codecRisk of call drop

while voice qualityis still OK

at cell border

AMR codecs are more resistant than the signaling channel (SACCH).

AMR calls can be stopped because of RLT expiry due to persistent bad SACCH quality (while AMR codec still

performing well), in particular in FR usage.

In B10, a shorter-term solution to fix this issue was the Differentiated Radio Link Timeout for AMR callsfeature. It is desirable to use higher RLT values for AMR calls than for Legacy Codecs.

A long-term solution is to strengthen SACCH. This is introduced in B11 with the new Repeated DL FACCHand Repeated UL & DL SACCH feature.


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1.4 Improved Coverage in B11

In B11, the Repeated DL FACCH and Repeated UL & DL SACCHfeatures improve the robustness of signaling.

Repeated UL & DL SACCH (RSACCH): Extended Coverage & reduction of calldrops.

Repeated DL FACCH (RDFACCH): Improves handover reliability of AMR calls.

BTS

Improved coverage with RSACCH and RDFACCH


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2 How Does It Work?

2.3 Repeated DL SACCH [cont.]

Have you understood the RDSACCH mechanism?Select the correct statements.

When the MS cannot decode correctly (before combining) a DL SACCH, it requests for repetitionby setting the SRR bit.

On BTS/LAPDm side, any DL SACCH block can be repeated.

RDSACCH involves only 2 layers: the LAPDm in the BTS on the one hand and the physical layer inthe MS on the other hand.

When the RDSACCH feature is activated, any DL SACCH frame is sent twice.

If the last DL SACCH frame can not be decoded, the MS tries to soft combine it with the previousframe.

RSACCH is mandatory for Rel-6 MSs, furthermore it cannot be applied to legacy MSs, contrary toRDFACCH.


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2 How Does It Work?

2.5 Dynamic Activation of RSACCH [cont.]

The RDSACCH is also triggered when the UL RLT counter is inferior orequal to the value of RADIOLINK_REP_DL_SACCH. This avoids blocking

scenarios and enables to react in case of rapid UL field drops (i.e. incase the SRRis not received anymore due to bad UL quality).

BadUL SACCHRel-6 MS

BTS

RADIOLINK_RECOVERY_THRES

RLS Counter

10

09

RADIOLINK_REP_DL_SACCH

RADIOLINK_TIMEOUT_BS

RDSACCHactivation

RADIOLINK_REP_DL_SACCH is set by default to 10 (i.e. equal to RADIOLINK_RECOVERY_THRES (=

N_BSTXPWR_M) - 3) to give time to the BSS to set the power output of the BTS and of the MS to itsmaximum value (recovery mechanism).


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Exercise

Have you understood the RUSACCH, RDFACCH and RDSACCH mechanisms?Match each item on the left with the corresponding features.

AMR Codec-based dynamic activation

Dynamically activated using SRR or RLT procedures

Mandatory for Rel-6 MS

Each frame is sent twice

A frame may be sent twice

It can be applied to legacy (pre-Rel-6) MS

New SACCH Repetition Order (SRO) field

RDFACCH

RUSACCH

RDSACCH


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3.1 RUSACCH and RLS [cont.]

The introduction of RUSACCH has an impact on the receiving principleof SACCH blocks and on the Radio Link Supervision (RLS).

Outcome ofthe first decoding

BTS

Rel-6MS

+Outcome of

the second decoding

=Soft combining

RADIOLINK_RECOVERY_THRES

RLS Counter

171615

14

13121110

09

RADIOLINK_REP_DL_SACCH

RADIOLINK_TIMEOUT_BS

BadUL SACCH

SACCH Block Receiving Procedure and Radio Link Supervision

In B11, with the possibility of a repeated UL SACCH, the following principle shall be used:

When an SACCH block is received, there's a first decoding attempt without combining:

If the decoding is performed, then the RLT counter is incremented by 2.

If the decoding is not performed, then a second decoding is attempted by combining with the previous

SACCH block:

If the second decoding is successful, then the RLT counter is incremented by 2.

If the second decoding failed, then the RLT counter is decremented by 1.


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4.1 RDFACCH Enabling

New Parameters

The RDFACCH feature is optional. It can be enabled at cell level.

EN_REP_DL_FACCH REP_DL_FACCH_LEGACY_SUPPORT

REP_DL_FACCH_THRES_AMR_FR

REP_DL_FACCH_THRES_AMR_HR

REP_DL_FACCH_THRES_AMR_WB

EN_REP_DL_FACCH

Definition: Enables repeated downlink FACCH for AMR calls.

Instance: cell, changeable.

Range/default value: Three levels: 0: Repeated DL FACCH not enabled (default), 1: Repeated DL FACCH enabled for LAPDm

command frames,2: Repeated DL FACCH enabled for LAPDm command frames, and also for LAPDm response frames (valid only forthe MS having indicated the support of the feature by Repeated ACCH Capability bit=1).

REP_DL_FACCH_LEGACY_SUPPORT

Definition: Legacy support for Repeated Downlink FACCH for AMR calls.

Remarks: This parameter is relevant only if Repeated Downlink FACCH is enabled (EN_REP_DL_FACCH parameter). This parameter

concerns only the LAPDm command frames.

Instance: cell , changeable.

Range/default value: 0: Repeated DL FACCH enabled only for the AMR MSs having indicated the support of the feature by

Repeated ACCH Capability bit=1 (default), 1: Repeated DL FACCH enabled for all AMR MSs.

REP_DL_FACCH_THRES_AMR_FR

Definition: Repeated DL FACCH activation threshold for AMR FR. Dynamic activation is done as long as CMR is inferior or equal to the

threshold value.

Instance: cell, changeable

Range/default: 0=off, 1=4.75kbps, 2=5.15kbps, 3=5.9kbps (default), 4=6.7kbps, 5=7.4kbps, 6=7.95kbps, 7=10.2kbps, 8=12.2kbps

REP_DL_FACCH_THRES_AMR_HR

Definition: Repeated DL FACCH activation threshold for AMR HR. Dynamic activation is done as long as CMR is inferior or equal to the

threshold value.


Range/default: 0=off, 1=4.75kbps, 2=5.15kbps, 3=5.9kbps (default), 4=6.7kbps, 5=7.4kbps

REP_DL_FACCH_THRES_AMR_WB

Definition: Repeated DL FACCH activation threshold for AMR WB. Dynamic activation is done as long as CMR is inferior or equal to thethreshold value.


Range/default: 0=off, 1=6.60kbps (default), 2=8.85kbps, 3=12.65kbps


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Module Summary

The Repeated DL FACCH (RDFACCH) and Repeated UL & DL SACCH(RSACCH) features improve the robustness of signaling.

The RDFACCH mechanism means that each DL FACCH frame is senttwice.

The RUSACCH mechanism means that an MS shall send upon BSS ordera UL SACCH frame twice.

The RDSACCH mechanism means that the BSS may send a DL SACCHframe twice.

The dynamic activation ofRDFACCH is AMR Codec based.


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Module Summary [cont.]

RSACCH is also dynamically activated using a specific algorithm (SRR orRLT).

The RSACCH and RDACCH are not linked.

RDFACCH and RSACCH can be activated only for calls using AMR-NB orAMR-WB.

Both features can be enabled at cell level.

Both features have been introduced in Rel-6 specifications and aremandatory for Rel-6 MSs.


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End of ModuleRepeated ACCH


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Module Objectives


Describe the purpose of the "Inter-BSS/RAT NACC" feature and its Telecomand O&M impacts


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1.1 NACC in B10

Do you remember NACC?Select the correct statements.

With NACC, the network can send SI1, SI3 and SI13 of target cell after PS cell reselection

The NACC is mandatory for Release 4 MSs supporting the GERAN feature Package 1

It has been introduced in ALU BSS B10 release

In B10, the NACC could occur only for a source and target cells mapped on the same GPU

In B10, the NACC could occur for a source and target cells mapped on 2 GPUs belongingto the same MFS

In B10, the NACC could occur for a source and target cells mapped on 2 GPUs belongingto different MFSs

SI1 and SI3 are provided by the BSC to the MFS, SI13 is built by the serving MFS


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1.2 Principle of NACC in B10

The NACC feature has beenintroduced in B9. Thisfeature allows to decreasethe GPRS service outageduring intra-BSS PS cellreselection, by providing theMS with a set of SystemInformation (SI) messages,required to access the newcell, before the MS leavesthe old cell.

BSS1 BSS1Cell A Cell B

BTSA

BTSB

SGSN

Throughput(Kbit/s)

Averagethroughput

t0

Reduced serviceoutage

Time(s)t1 t2 t3

Intra-BSS

The feature reduced the service outage time for an MS in packet transfer mode from a couple of seconds

down to 300-700 ms by giving the network a possibility to assist the MS before and during the cell change.The assistance is given as sending of neighbouring cell system information.


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2 How Does It Work?

2.1 Inter-BSS/RAT NACC Principles in B11

What Is RIM?

The RAN Information Management (RIM) procedures provide a generic

mechanism for the exchange of arbitrary information between two RANnodes, located either in a GERAN or in a UTRAN access network.

SGSN(s)

RAN-INFORMATION-

ACK

RAN-INFORMATION/Multiple Report

(ACK)

SI ChangeSI Request

RAN-INFORMATION-

REQUEST/MultipleReport

RAN-INFORMATION/

InitialMultiple Report

The SGSNssimply perform a relay

of the messages

Target BSSCurrent BSS

or RNC

The RAN Information Management (RIM) procedures allow to send information between BSCs/RNCs via one

or more SGSNs. The SGSNs simply perform a relay of the messages (possibly inter-SGSN). Any relationbetween messages is transparent for the SGSN.

Two main procedures are defined:

RAN Information Request procedure: initiated by a Controlling BSS/RNC when it requires information (inNACC case: SI) from another Serving BSS/RNC, or when it requires stop of event driven reports from another

Serving BSS/RNC.

RAN Information Send procedure: initiated by a Serving BSS when it has information to be sent toanother Controlling BSS/RNC. The procedure may be event-triggered (e.g. SI change) or scheduled (e.g. by

a request procedure). Sending BSS may request acknowledgement of the information.

Routing and addressing of the messages are done through:

cell identifiers for the BSS.

A BSS is addressed by the Routing Area Identity (RAI) + Cell Identity (CI) of one of its cells.

RNC identifiers for RNC.

An RNC is addressed by the Routing Area Identity + RNC-Id.


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2 How Does It Work?

2.1 Inter-BSS/RAT NACC Principles in B11 [cont.]

What Is RIM?

The RAN Information Management (RIM) procedures provide a generic

mechanism for the exchange of arbitrary information between two RANnodes, located either in a GERAN or in a UTRAN access network.

SGSN(s)

RAN-INFORMATION-

ACK

The SGSNssimply perform

a relay of the messages

RAN-INFORMATION/Multiple Report

(ACK)

SI ChangeSI Request

Target BSSCurrent BSS

or RNC

The RAN Information Management (RIM) procedures allow to send information between BSCs/RNCs via one

or more SGSNs. The SGSNs simply perform a relay of the messages (possibly inter-SGSN). Any relationbetween messages is transparent for the SGSN.

Two main procedures are defined:

RAN Information Request procedure: initiated by a Controlling BSS/RNC when it requires information (inNACC case: SI) from another Serving BSS/RNC, or when it requires stop of event driven reports from another

Serving BSS/RNC.

RAN Information Send procedure: initiated by a Serving BSS when it has information to be sent toanother Controlling BSS/RNC. The procedure may be event-triggered (e.g. SI change) or scheduled (e.g. by

a request procedure). Sending BSS may request acknowledgement of the information.

Routing and addressing of the messages are done through:

cell identifiers for the BSS.

A BSS is addressed by the Routing Area Identity (RAI) + Cell Identity (CI) of one of its cells.

RNC identifiers for RNC.

An RNC is addressed by the Routing Area Identity + RNC-Id.


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2 How Does It Work?

2.2 Inter-BSS/RAT Principles

Have you understood the RIM procedure?Select the correct statements.

The RAN Information Management is an Alcatel-Lucent specific feature

The RIM procedure allows to send information between BSCs/RNCs via one or more SGSNs

This information may not be transparent for the SGSN

The RAN Information Send procedure is an event-triggered mechanism. It is used only when theset of NACC-related SI is changed

This procedure may be event triggered or scheduled

A BSS is addressed by the RAI + Cell Identity (CI) of one of its cells

An RNC is addressed by the RAI + RNC-Id+Cell Identity (CI) of one of its cells


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2 How Does It Work?

2.4 Cell Reselection:3G-to-2G Cell Reselection

Inter-RAT NACC Procedure

In order to provide the MS with SI of external adjacent cells, the

current BSS/RNC shall obtain them from another target BSS, via theSGSN. The RAN Information Management (RIM) procedure allows to sendinformation between BSCs/RNCs via one or more SGSNs. The RIM allowsa UTRAN to get SI of a target 2G cell.

SGSN 1 SGSN 2

Serving cell Target cell

UTRAN BSS 2

3G-to-2GPS Cell Reselection

RIM-NACCprocedure

In the inter-BSS case, the exchanges with the MS are the same as in Release 4 NACC.

In order to provide the MS with SI of external adjacent cells, the Controlling BSS shall obtain them from

another Serving BSS, via the SGSN.

The RAN Information Management (RIM) procedure allows to send information between BSCs/RNCs via one

or more SGSNs. The SGSNs simply perform a relay of the messages (possibly inter-SGSN). Any relation

between messages is transparent for the SGSN, i.e. a request/response exchange between RIM applications,

is routed and relayed as two independent messages by the SGSN.

The support of RIM by the BSS and the SGSN is negotiated thanks to the Bitmap Mechanism of BSSGPInterface feature.

Routing and addressing of the messages is done through cell identifiers for the BSS and through RNCidentifiers for RNC.

SIs are requested for a given 2G cell. The sets of SIs to be sent to the MS are SI1, SI3 (both provided by the

BSC to the MFS) and SI13 (built by the serving MFS).

In B11, the inter-BSS NACC can occur between 2 MFSs or also between 2 GPUs belonging to the same MFS

but supporting different BSSs. In this last case, no inter-GPU signaling is used. The usual procedure via the

SGSN is also used between 2 GPUs in the same MFS.


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3.1 Inter-BSS/RAT NACC Principles

Have you understood the Inter-BSS/RAT NACC procedure?Click on each button in the right order to display the steps of this scenario.

MSCurrent MFS/

RNCTarget

MFS

1 2

3

4

5

6

7

8

Data block

Packet Cell Change Continue

Packet Cell Change Notification

Packet Neighbour Cell Data

Packet Neighbour Cell Data

RAN- Information

RAN- Information Request

Polling

PAGING_COORDINATION_REQ:

A new message is introduced in the BSCGP to forward CS paging to the MFS. The same new message is used

for both Paging commandandMultiple Paging commandscenarios.


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4.1 Configuration Management

New Parameters

The Inter-BSS/Inter-RAT NACC feature is optional. It can be activated at

BSS level. EN_RIM_NACC

T_RIR

T_RI

T_MULTIPLE_REPORT

N_RIM_RETRIES

EN_RIM_NACC:

This parameter enables inter-BSS and inter-RAT NACC.

It can take the following values:

0: RIM NACC feature disabled

1: Inter_BSS_NACC only enabled

2: Inter_RAT_NACC only enabled

3: Inter_BSS_NACC and Inter_RAT NACC enabled

T_RIR:

The timer supervising the reception of RAN Information.

Changeable: 1 255 sec/ 10

T_RI

The timer supervising the reception of RAN information ACK.

Changeable: 1 255 sec/10

T_MULTIPLE_REPORT:

The timer supervising the reception of the following RAN information with multiple report MFS.

Changeable: 15 360 mn/60

N_RIM_RETRIES:

The number of times a RAN procedure is sent before giving up (in case of no answer).

Changeable: 1 255 /2


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4.2 Performance Management

New Counters NB_SERVING_INTER_BSS_NACC

NB_SERVING_INTER_RAT_NACC NB_CONTROLLING_INTER_BSS_NAC

TIME_SPENT_RIM_NACC_PROCEDURE

TIME_SOURCE_RIM_NACC_CELL_RESEL

MAX_SOURCE_RIM_NACC_CELL_RESEL_TIME

MIN_SOURCE_RIM_NACC_CELL_RESEL_TIME

NB_SERVING_INTER_BSS_NACC:

The number of received RAN-Information-Request from a controlling BSS. Within the granularity period, the MFS counts the number ofRAN-INFORMATION-REQUEST received from a BSS (both single and multiple reports).

Measured object: Target Cell

NB_SERVING_INTER_RAT_NACC:

The number of received RAN-Information-Request from a controlling RNC. Within the granularity period, the MFS counts the number of

RAN-INFORMATION-REQUEST received from a RNC (both single and multiple reports).


NB_CONTROLLING_INTER_BSS_NACC:

The number of successful RAN-Information-Request sent to another BSS. Within the granularity period, the MFS counts the number ofRAN-INFORMATION-REQUEST sent to another BSS (both single and multiple reports).


TIME_SPENT_RIM_NACC_PROCEDURE:

The cumulated time needed to require the SI of the target cell via the RIM procedure. This will allow to estimate the time during

which a RAN-Information-Request PDU is sent and a RAN-Information PDU is received.


TIME_SOURCE_RIM_NACC_CELL_RESEL:

The cumulated time of the successful Network Assisted cell reselection duration in NC0 mode in case of Inter-BSS serving cell. Within

the granularity period, the MFS cumulates the duration of each successful outgoing RIM_NACC cell reselections triggered by the BSS in

the source cell.

MAX_SOURCE_RIM_NACC_CELL_RESEL_TIME:

The maximum Network-Assisted cell reselection duration in NC0 mode = maximum value of counter

TIME_SOURCE_RIM_NACC_CELL_RESEL.

MIN_SOURCE_RIM_NACC_CELL_RESEL_TIME:

The minimum Network-Assisted cell reselection duration in NC0 mode = minimum value of counter

TIME_SOURCE_RIM_NACC_CELL_RESEL.


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Module Summary

In B11, the benefits of NACC are extended to the inter-BSS and 3G-to-2G Cell Reselection cases.

The GPRS service outage during inter-BSS or inter-RAT PS cellreselection is improved.

RAN Information Management (RIM) is generic mechanism for theexchange of information between two RAN nodes (GERAN or UTRAN).

For 2G-to-2G Inter-BSS Cell Reselections, the RIM allows a BSS to getSystem Information of 2G cells located in another BSS.

For 3G-to-2G Cell Reselections, the RIM allows a UTRAN to get SI of atarger 2G cell.

The Inter-BSS/Inter-RAT NACC feature is optional. It can be activatedat BSS level.


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Self-assessment on the Objectives

Please be reminded to fill in the formSelf-Assessment on the Objectives

for this module The form can be found in the first part

of this course documentation


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End of ModuleNACC for Inter BSS and Inter RAT


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Do not delete this graphic elements in here:

14All Rights Reserved Alcatel-Lucent 2010Module 4

Tandem Free Operation with AMR-NB3JK11696AAAAWBZZA Issue 1.0

Section 1BSS B10-B11 Telecom Evolutions

GERANBSS B10-B11 Telecom EvolutionTMO18090 D0 SG DEN Issue 2.0


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GERAN BSS B10-B11 Telecom EvolutionBSS B10-B11 Telecom Evolutions Tandem Free Operation with AMR-NB

1 4 2

Blank Page




Document History


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1 4 3

Module Objectives


Describe the purpose of the "Tandem Free Operation (TFO) for AMR-NB"feature and its Telecom and O&M impacts


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1 4 4

Module Objectives [cont.]



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Table of Contents

Switch to notes view!Page

1 What Is the Purpose of this Feature? 71.1 TFO Implementation Prior to B11 8

1.2 Prior to B11 91.3 Principle in B11 10

2 How Does It Work? 112.1 Do You Remember AMR-NB? 122.2 TFO Negotiation and Decision Algorithm 142.3 AMR Codec Adaptation with TFO 16

2.3.1 UL Downgrading 172.3.2 DL Downgrading 182.3.3 UL Upgrading 192.3.4 DL Upgrading 20

2.4 TFO AMR-NB vs TFO Rel.99 213 What Are the Telecom Impacts? 22

3.1 TFO Interoperability with TrFO 23

3.1.1 2G-2G Interoperability 243.1.2 2G-3G Interoperability 283.2 TFO Interoperability with UMTS 29

4 What Are the O&M Impacts? 304.1 Configuration Management 314.2 Performance Management 32


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1.1 TFO Implementation Prior to B11

Do you remember the TFO implementation before B11?Select the correct statements.

In B10, the AMR-NB and TFO are not supported together by the Alcatel-Lucent BSS

Alcatel-Lucent provides TFO since B7 for legacy Codecs and since B10 for AMR-WB

Calls established with AMR-NB will either stay in AMR with tandeming or use TFO

TFO implementation in B7 is aligned with 3GPP Rel.99 version of TFO. The MS shouldbe R99

TFO is a prerequisite for AMR-WB. AMR-WB does not make sense without TFO


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1.2 Prior to B11

Before B11, the AMR-NB and TFO features were not supportedtogether by the Alcatel-Lucent BSS. Only TFO for legacy codecs (EFR,

FR & HR) is supported since release B7 and since B10 for AMR-WB.Therefore, in case of AMR-NB, TFO cannot be used, hence a degradedvoice quality (3 transcoding stages). The issue is tandeming in NGN:G711oIP requires high bandwidth.

MS 1 MS 2

BSS 1 BSS 2

TC1

TC2

MSCserver

MSCserver

AMR-NB AMR-NB G711 G711G711 over IP

IP

AMR-NB AMR-NB

NoTFO

NoTFO

G711oIPrequires

highbandwidth

DegradedSpeech Quality

due to 3 transcodingstages

MG MG

TFO Implemented in B7

TFO implementation in B7 is aligned with 3GPP Rel.99 version of TFO.

There is no impact on the MS.

TFO is possible with FR, EFR, HR.

TFO is NOT possible with AMR-NB.

Force_TFO_vs_AMR option: Depending on the preference given by the operator, calls established with

AMR-NB will:

either stay in AMR, with tandeming.

or go to TFO, with FR, EFR or HR.

A simple algorithm is used with TFO for codec negotiation:

If both sides support EFR, use EFR, else If both sides support FR, use FR, else

Use HR.


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1.3 Principle in B11

In release B11, the TFO feature can be used together with AMR-NB.TFO provides a better voice quality by avoiding unnecessary

successive coding and decoding operations in the case of mobile-to-mobile calls. Furthermore, with the introduction of the NGN, TFO forall GSM codecs gets an important application that is related to thebandwidth saving aspects at the CN level.

MS 1 MS 2

BSS 1 BSS 2

TC1

TC2

MSCserver

MSCserver

IP

AMR-NB AMR-NB AMR-NB AMR-NBAMR-NB AMR-NB AMR-NB

TFO TFOTrFOAMR over IP

Transcoding FunctionsBypassed

High transmissionsavings in NGN

BetterSpeech Quality

MG MG

Transcoder Free Operation (TrFO) is a Core Network protocol, applicable to the NGN architecture.

TrFO allows to transport speech in the Core Network using GERAN/UTRAN codecs over IP, rather than

G.711. Advantages:

Gain in transmission bandwidth.

Gain in speech quality if the same codec is used over the complete path.

Contrarily to TFO, TrFO is out-of-band, i.e. negotiation is not done in the User Plane (embedded in speech

frames), but in the Control Plane, on a specific interface.

The AMR +TFO feature improves the speech quality of mobile-to-mobile calls and TFO-TrFO interaction in

the NGN core network.

AMR-WB without TFO does not make sense.


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2 How Does It Work?


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2 How Does It Work?

2.1 Do You Remember AMR-NB?

Do you remember the Codec Mode Adaptation Mechanism?Select the correct statements.

The BTS adapts the codec to the radio link condition among a subset of codecs

The TC adapts the codec to the radio link condition among a subset of codecs

With AMR-NB, maximum 4 codec modes are used for a given call

The same codec subset is used for both the Uplink and the Downlink

The codecs used in UL and used in DL can be different: the adaptation isindependent in each direction


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2 How Does It Work?

2.1 Do You Remember AMR-NB? [cont.]

Do you know the AMR-related vocabulary?Match each term from the list on the left to its correct definition from the list onthe right.

Active Codec Set (ACS)

Supported Codec Set (SCS)

Maximum Active CodecSet (MACS)

Initial Codec Mode (ICM)The list of codec modes usable for the ongoingcall

The list of all codec modes supported by theBSS for a given AMR codec

The maximum number of codec modessupported for the ongoing call

The codec mode to use in DL and UL at TCHactivation

Common Active Codec Set

(CACS)Common Supported Codec

Set (CSCS)Intersection of SCS on both sides

ACS used for TFO, based on ACS on both sides

Rule for implicit ICM:

If ACS contains 1 mode, then this shall be the Initial Codec Mode.

If ACS contains 2 or 3 modes, then the Initial Codec Mode shall be the most robust mode of the set (with

the lowest bit rate).

If ACS contains 4 modes, then the Initial Codec Mode shall be the second most robust mode of the set

(with the second lowest bit rate).


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2 How Does It Work?

2.2 TFO Negotiation and Decision Algorithm

The establishment of a TFOcall begins with a negotiation

phase. Each TFO partnerexchanges by means of TFOmessages (TFO_REQ,TFO_ACK) the local usedcodec type, the Active Codecmodes Set (ACS) and theSupported Codec modes Set(SCS). Each partner runs inthe TC a decision algorithm todecide if TFO can be

established and on whatcodec type and set of codecmodes.

LACS == DACS

FR HR Matching?

CalculateOACS and IACS

FR HR Optimization

OACS

IACS == OACS?

IACSsub-set of

OACS?

Change ACS toOACS (if supported)

TFO Establishmenton OACS

Codec ModeOptimization

Both radio legsuse or offer AMR-NB

ImmediateTFO Establishment


Codec MismatchResolution


Yes

No

Yes

No

No

Yes

Yes

NoYes

No

The decision algorithm is standardized by 3GPP:

LACS == DACS: Establishes immediate TFO if the local and distant ACS are identical. Example: Enableimmediate TFO establishment within one operator's homogeneous network. The operator's choice is always

acceptable and needs no optimization.

FR HR Matching: The goal is to enable immediate TFO between 3G channels and 2G FR and 2G HRchannels.

A Common ACS (CACS) is acceptable for immediate TFO establishment without consideration of the OACS if

all of the following conditions are fulfilled:

one radio leg uses FR_AMR or UMTS_AMR_2, the other uses HR_AMR [for AMR TFO].

the CACS is contiguous.

the CACS fulfills the acceptability rule.

FR HR Optimization: Takes place after immediate TFO establishment in the case of FR HRMatching. The FR_AMR-side adopts the ACS of the HR_AMR-side, if this ACS is supported and the

optimization mode allows an ACS change.

Codec Mismatch Resolution: A TFO connection with the currently used AMR codec types will not bepossible, but the remaining codec types have to be investigated.

Codec Type Optimization and Codec Mismatch resolution:

These procedures already exist up to B10 for the GSM EFR, FR and HR codec types. The principle

remains the same but with the specificities linked to AMR-NB. The codec mismatch resolution and

codec type optimization remain delegated to the BSC.

These procedures are optional and driven with the TFO_OPT and TFO_MATCH options. These options

control the overall TFO behavior. They are independent from the codec types or codec modes

involved in the TFO call.

It is not foreseen to support the AMR configuration with optimization allowed, so an ACS change cannotoccur.


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2 How Does It Work?

2.2 TFO Negotiation and Decision Algorithm [cont.]

The FR-HR matching allows to establish TFO immediately in case one side usesFR_AMR and the other HR_AMR. Here is an example of FR-HR matching: One sideuses FR_AMR with a Maximum of Active Codec mode Set of 4 (MACS), the other

side HR_AMR uses a MACS of 3 codec modes. It is possible to establish ImmediateTFO on IACS and on FR-HR matching. But no further optimization is done.Select the codec modes used within CSCS, OACS and IACS.

Codecmode SCS ACS ACS SCSIACS OACS CSCS

12.20

7.95

6.70

5.15

10.20

7.40

5.90

4.75

The decision algorithm is standardized by 3GPP:

LACS == DACS: Establishes immediate TFO if the local and distant ACS are identical. Example: Enableimmediate TFO establishment within one operator's homogeneous network. The operator's choice is always

acceptable and needs no optimization.

FR HR Matching: The goal is to enable immediate TFO between 3G channels and 2G FR and 2G HRchannels.

A Common ACS (CACS) is acceptable for immediate TFO establishment without consideration of the OACS if

all of the following conditions are fulfilled:

one radio leg uses FR_AMR or UMTS_AMR_2, the other uses HR_AMR [for AMR TFO].

the CACS is contiguous.

the CACS fulfills the acceptability rule.

FR HR Optimization: Takes place after immediate TFO establishment in the case of FR HRMatching. The FR_AMR-side adopts the ACS of the HR_AMR-side, if this ACS is supported and the

optimization mode allows an ACS change.

Codec Mismatch Resolution: A TFO connection with the currently used AMR codec types will not bepossible, but the remaining codec types have to be investigated.

Codec Type Optimization and Codec Mismatch resolution:

These procedures already exist up to B10 for the GSM EFR, FR and HR codec types. The principle

remains the same but with the specificities linked to AMR-NB. The codec mismatch resolution and

codec type optimization remain delegated to the BSC.

These procedures are optional and driven with the TFO_OPT and TFO_MATCH options. These options

control the overall TFO behavior. They are independent from the codec types or codec modes

involved in the TFO call.

It is not foreseen to support the AMR configuration with optimization allowed, so an ACS change cannotoccur.


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2 How Does It Work?

2.3 AMR Codec Adaptation with TFO

The Codec mode adaptation is performed independently on eachdirection. But for one direction, the same codec mode is used

from one MS to the other MS.

Codec mode adaptation is always performed for the side havingthe worst radio conditions.

The codec mode used in one direction may be different from the one used in the other direction. But

for one direction, the same codec mode is used from one MS to the other MS.

The same codec mode is used for each leg.

Example:

From MS1 in UL to MS2 in DL, AMR-NB 12.2 kbit/s


The codec mode adaptation is performed independently on each direction. But in one direction, thecodec mode adaptation is triggered by both radio interfaces.

Codec mode adaptation is always done for the side having the worst radio conditions.

The principle for codec mode adaptation in ongoing TFO is that the BTS controlling the MS always takesthe final decision to upgrade or downgrade its local uplink direction. This BTS sends the Codec ModeCommand downlink.

The Codec Mode Request for the local uplink direction is taken directly into account and the effectivedelay is not higher than in normal connections.

The Codec Mode Request from the remote side in the remote downlink direction is also taken intoaccount, but it becomes active with a reaction time increased by the round trip delay between bothBTSs.

Upgrading is possible only if both radio links in one direction (first uplink then downlink) are goodenough.

Downgrading is necessary if one (or both) radio link(s) is(are) not good enough.


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2.3.1 UL Downgrading

MS1 BTS1 TRAU1 TRAU2 BTS2 MS2

The BTS detectsa bad uplink quality

CMC: new codec(lower rate)

The MS1 usesimmediately

the new codec

CMI: new codec CMI:new codec CMI:

new codec CMI:new codec CMI:

new codec

TFO establishment with original codec

TFO establishment with new codec




Example:



The codec mode adaptation is performed independently on each direction. But in one direction, thecodec mode adaptation is triggered by both radio interfaces.

Codec mode adaptation is always done for the side having the worst radio conditions.

The principle for codec mode adaptation in ongoing TFO is that the BTS controlling the MS always takesthe final decision to upgrade or downgrade its local uplink direction. This BTS sends the Codec ModeCommand downlink.

The Codec Mode Request for the local uplink direction is taken directly into account and the effectivedelay is not higher than in normal connections.

The Codec Mode Request from the remote side in the remote downlink direction is also taken intoaccount, but it becomes active with a reaction time increased by the round trip delay between bothBTSs.

Upgrading is possible only if both radio links in one direction (first uplink then downlink) are goodenough.

Downgrading is necessary if one (or both) radio link(s) is(are) not good enough.


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2.3.2 DL Downgrading

MS1 BTS1 TRAU1 TRAU2 BTS2 MS2

TFO establishment with original codec

The MSdetects a bad

downlink quality

CMR:

new codec(lower rate)

The BTSdecides to adaptdownlink codec

CMR: new codec

CMC: new codec

The MS2 usesimmediately

the new codecCMI:

new codec

TFO establishment with new codec

CMR:new codec CMR:

new codec

CMI:new codecCMI:

new codecCMI:new codecCMI:new codec




Example:



The codec mode adaptation is performed independently on each direction. But in one direction, theco

tmo18090d0sgdeni2.0 complete b10 b11

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