Dynamic Coordination of Signal Processing Functions Using ITU-T Rec. G.799.2

InternationalTelecommunicationUnion

Dynamic Coordination of Signal Processing Functions Using

ITU-T Rec. G.799.2

Dominic HoEricsson Canada Inc.

Mont-Royal, Quebec, Canada

ITU-T Workshop on “Interactions of Vocieband Signal processing Functions and their End-to-End Coordination”

(Germantown, Maryland, USA. 21 April 2010)


Motivation Modern telephony networks uses voice-quality

enhancement (VQE) features, denoted as Signal Processing Functions (SPFs), for optimum quality of experience

For maximum effectiveness of VQE features it is necessary:

- To deploy all applicable VQE features- To avoid multiple (tandem) application of the same feature - To exercise the feature at the optimal location along the call path

The intent of ITU-T Rec. G.799.2 is to develop the mechanism framework for the dynamic coordination of VQEs present on bearer paths for the purpose of improving overall end-to-end voice quality

2


SPE and SPFGeneric Call Connection:

3

SPE-1 SPE-2 SPE-3

SPE (Signal Processing Equipment)

NetworkMobile

AECG.160

ALCG.169

NRG.160

ECG.168

ALEG.169

SPF (Signal Processing Function):

• AEC

• ALC

• EC

• ALE

• NR

SPE-0


Scope and Applicability of G.799.2

Mobile Phone

IP packet network

SPNE-TMGW-O MGW-T

BSC-O

MSC-O MSC-TServer

Media Path

Signalling Path

Land User

SC-TServer

Circuit-Switched network

Q.115.xG.799.2

G.799.2 covers the coordination of SPFs in network equipment and in terminal devices

4


Challenges in Mobility Communications

Acoustic Echo

Hybrid Echo

- AEC- ALC- ALE

- ALC- EC- ALE

- ALC- EC- AEC

Dynamic SPF insertion/removal due to dynamic call configuration and modification

Permutation of points of SPF deployment Variety of topologies : inter-MSC, intra-MSC Examples of Call Connection Cases:

– Mobile-land calls– Mobile-mobile calls– Mobile calls with handover– Mobile calls with call transfer– Landline calls transferred to mobile

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Dynamic Coordination Mechanism

Dynamic coordination of SPF is achieved through:– An encapsulation format (capability list) to facilitate

identification of SPF capabilities from different equipment/devices in a dynamic manner

– Rules for exchange of capability lists among nodes in a call-path, for SPF coordination in static and dynamic call configurations

– SPF engagement rules executed by individual equipment/devices based on common view of capabilities available along a given bearer path

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Capability List Format7 6 5 4 3 2 1 0 Descriptions

V F N

Common Part SPID

Length

Reserved ID Entry 1

Reserved Len

Attribute

Reserved ID Entry 2

Reserved Len

Attribute

Common part: V (3 bits): Version number

F (1 bit): Forward / Reverse flag N (4 bits): Number of entries SPID (16 bits): SPNE/device Identifier Length (8 bits): Capability-list size in bytes (common + entries)

Entry part: ID (4 bits): SPF entry identifier Len (4 bits): Entry size in bytes, including the entry ID byte and the entry Len byte and the attribute bytes Attribute: Entry attribute information with zero, one or multiple bytes (To be defined)

Reserved: Reserved field with a value of 0x00

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SPF ID

AEC 0 0 0 1

ALC 0 0 1 0

EC 0 0 1 1

ALE 0 1 0 0

NR 0 1 0 1


Capability List Exchange

Signal Processing

Equipment(SPE)

ForwardCapability

ListUpdate

ReverseCapability

ListUpdate

Signal Flow

Each entry(cell) corresponds to a specific Signal Processing Function

Signal Processing Function includes, but is not limited to:

• Network Echo Cancellation (EC),

• Acoustic Echo Control (AEC),

• Automatic Level Control (ALC),

• Noise Reduction (NR),

• Automatic Listener Enhancement

(ALE)

Capability List received is updated with new information and sent to next SPE, if necessary

Each SPE enables or disables its function based on Capability view, in accordance with pre-determined coordination rules

ForwardCapability

ListReceived

ReverseCapability

ListReceived

8


Example of Information Exchange

SPE1 SPE2

…

A1

B1

A1

B1

C2

A1

B1

An-1

Bn

Cn

Dn-1

An-1

Bn

Cn

Dn-1

An-1

Bn

Cn

Dn-1

An-1

Bn

Cn

Dn-1

SPEnSPEn-1

A1

B1

C2

Dn-1

A1

B1

C2

A1

B1

C2

Dn-1

A1

B1

C2

Dn-1

Bn

Cn

An-1

Bn

Cn

Dn-1

Bn

Cn

Forward Capability List

Reverse Capability List

Forward and reverse capability lists for bear traffic from left to Right

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VQE Engagement Rules AEC : as close as possible to the source of acoustic echo ALC : as close as possible to the signal source EC : as close as possible to the local loop ALE : as close as possible to the destination NR : as close as possible to the signal source

Engagement example in mobile-land call (for bearer traffic from left to right)

Signal Processing Functions

Preferred Location for Signal Processing Functions

AEC High Preference Medium Preference Low Preference

NR High Preference Medium Preference Low Preference

ALE Low Preference Medium Preference High Preference

Acoustic echo

SPNE-1 SPNE-2 SPNE-3

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Coordination Examples

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VoIP Mobile-Mobile Call With Handover Call flow:

- Mobile-mobile call between MS1 and MS2 via media gateways MG1 and MG2- MS2 experiences a handover- Mobile-mobile call between MS1 and MS2 via media gateways MG1 and MG3

Enc: Low bit rate encoderDec: Low bit rate decoderALE: Automatic Listener EnhancementALC: Automatic Level ControlAEC: Acoustic Echo Control

IPEnc ALE

Dec AEC ALE

ALE AEC Dec

ALE Enc

MG2

AEC Dec

MG3

MS2MS1

EncAEC

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MG1

Encoded speech from MS1

Encoded speech to MS1


SPF Coordination : Before Handover


Enc ALE

ALE Enc

MG2

AEC Dec

MG3

MS2EncAEC

MG-1 - realizes that it is the first and last SPNE supporting AEC on MS-1MS-2 traffic- realizes that it is the first SPNE supporting ALC but there is a FBALC downstream

on MS-1MS-2 traffic MG-2

- realizes that there is an ALC upstream but it is the last one with FBALC on MS-1MS-2 traffic

Coordination Outcome- According to the preference rule, MG-2 continues FBALC support on MS-1MS-2

traffic, and MG-1 disables ALC on MS-1MS-2 traffic

Dec AEC ALE

IP

For Traffic flow from MS1 to MS2

ALE AEC Dec

13

MS1

MG1


SPF Coordination : After Handover


Enc ALE

Dec AEC ALE

ALE AEC Dec

ALE Enc

MG2

AEC Dec

MG3

MS2

MG1 - realizes that it is the first and last one with ALC, and it is the first but not the last

with AEC on MS1 MS2 traffic, MG3

- realizes that there is an AEC upstream closer to the source on MS1 MS2 traffic Coordination Outcome

- MG1 continues AEC support on MS1 MS2 traffic.- MG1 dynamically re-enables ALC support on MS1 MS2 traffic.- MG3 disables its AEC.

IP

For Traffic flow from MS1 to MS2

EncAEC

14

MS1

MG1


Generic Network Configuration

Mobile Phone

IP packet network

SPNE-TMGW-O MGW-T

BSC-O

MSC-O MSC-TServer

Media Path

Signalling Path

Land User

SC-TServer

Circuit-Switched network

Q.115.xG.799.2

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Yes

Yes

No

Yes

Enabled

Enabled

Yes

Disabled

Disabled

Yes

Yes

Disabled

No

No

No

Noise reduction (NR-T) for media from the land user

Yes

No

No

Yes

Enabled

Enabled

Yes

Disabled

Disabled

No

No

No

No

No

No

Echo Cancellation (EC) for Sin from the land

user

Yes

Yes

No

Yes

Disabled

Disabled

Yes

Yes

Disabled

Yes

Yes

Disabled

Yes

Yes

Enabled

Noise reduction (NR-O) for media from the mobile user

Yes

Yes

No

No

No

No

No

No

No

Yes

Yes

Disabled

Yes

Yes

Enabled

Acoustic Echo Control (AEC)

Tandem(results)SPNE-TMGW-TMGW-OMS-O

Voice enhancementprocessing functions

Q115

G799.2

Q.115.x （ Call set-up)

(Dynamic coordination) G.799.2

Coordination

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Current Status & Future Plans

G.799.2 has been approved as an ITU-T Recommendation end of last year(12/09)

G.799.2 contains the framework and mechanism for dynamic coordination of SPF

Development of protocols to implement G.799.2 will be in separate ITU-T Recommendations

SG16 is requesting SG11 and other SDOs for the guidance on the available protocols, especially for wireless links

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Documents

Dynamic Coordination of Signal Processing Functions Using ITU-T Rec. G.799.2