Signalling for seamless
interaction between networks
and devices
ITU-T SG16, Q18/16
Names
Motivation
 Modern telephony networks rely on a set of voice-quality
enhancement (VQE) features 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 draft ITU-T G.MDCSPNE is to develop the generic
framework for the dynamic coordination of VQEs present on
bearer paths for the purpose of improving overall end-to-end
voice quality
Scope and Applicability of G.MDCSPNE
MSC-O
MGW-O
SC-T
Server
MSC-T
Server
MGW-T
SPNE-T
BSC-O
Circuit-Switched
network
IP packet network
Land
User
Mobile
Phone
G.MDCSPNE
Q.115.x
Media Path
Signalling Path
Challenges in Mobility Communications




Dynamic VQE insertion/removal due to dynamic call configuration
and modification
Permutation of points of VQE feature deployment
Variety of topologies : inter-MSC, intra-MSC
Example of Use Cases:
– Mobile-land calls
– Mobile-mobile calls
– Mobile calls with handover
– Mobile calls with call transfer
– Landline calls transferred to mobile
- Acoustic Echo
Control
Acoustic
Echo
- Automatic
Level Control
- Acoustic
Echo Control
- Automatic
Level Control
- Feedback
Automatic Level
Control
- Network Echo
Canceller
Hybrid
Echo
Dynamic Coordination Mechanism

Dynamic coordination of VQE is achieved through:
– An encapsulation format (capability list) to facilitate
identification of VQE capabilities from different
equipment/devices in a dynamic manner
– Rules for exchange of capability lists among nodes in a
call-path, for VQE coordination in static and dynamic call
configurations
– VQE engagement rules executed by individual
equipment/devices based on common view of capabilities
available along a given bearer path
Capability List Format
7 6 5 4 3 2 1 0
V
F
N
Descriptions
Common Part
SPID
Length
Reserved
ID
Reserved
Len
Entry 1
Attribute
Reserved
ID
Reserved
Len
Entry 2
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):
Len (4 bits):
Attribute:
Reserved:
VQE entry identifier
Entry size in bytes, including the entry ID byte and the entryen
L byte and the attribute bytes
Entry attribute information with zero, one or multiple bytes (To be defined)
Reserved field with a value of 0x00
Capability List Exchange
Forward
Capability
List
Received
Forward
Capability
List
Update
SPNE
Speech Processing
Functions/Devices
Reverse
Capability
List
Update
 Each entry(cell) corresponds to a
specific Speech Processing Function
 Speech Processing Function includes,
but is not limited to:

Network Echo Cancellation (EC),

Acoustic Echo Control (AEC),

Automatic Level Control (ALC),

Noise Reduction (NR),

Signal Flow
Reverse
Capability
List
Received

Feedback Automatic Level
Control (FBALC)
 Capability List received is updated
with new information and sent to next
SPNE, if necessary
 Each SPNE enables or disables its
function based on Capability view, in
accordance with pre-determined
coordination rules
VQE Engagement Rules





AEC :
ALC :
EC :
FBALC :
NR :
as close as possible to the source of acoustic echo
as close as possible to the signal source
as close as possible to the local loop
as close as possible to the destination
as close as possible to the signal source
Engagement example in mobile-land call (for bearer traffic from left to right)
SPNE-1
SPNE-2
SPNE-3
Acoustic
echo
Signal Processing
Functions
Preferred Location for Signal Processing Functions
AEC
High Preference
Medium Preference
Low Preference
ALC
High Preference
Medium Preference
Low Preference
NR
High Preference
Medium Preference
Low Preference
Coordination Examples
VoIP Mobile-Mobile Call With Handover

Call flow:
– Mobile-mobile call between MS-1 and MS-2 via media gateways MG-1 and MG-2
– MS-2 experiences a handover
– Mobile-mobile call between MS-1 and MS-2 via media gateways MG-1 and MG-3
MG2
FBALC
Enc
FBALC
Dec
AEC
AEC
Dec
FBALC
Enc
AEC
Dec
AEC
Enc
IP
MS1
ALC
MG1
Enc: Low bit rate encoder
Dec: Low bit rate decoder
FBALC: Feedback Automatic Level Control
ALC: Automatic Level Control
AEC: Acoustic Echo Control
MG3
MS2
VQE Coordination : Before Handover
For Traffic flow from MS1 to MS2

MG-1
–


realizes that it is the first and last SPNE supporting AEC on MS-1MS-2 traffic
– realizes that it is the first SPNE supporting ALC but there is a FBALC downstream on MS1MS-2 traffic
MG-2
– realizes that there is an ALC upstream but it is the last one with FBALC on MS-1MS-2 traffic
Coordination Outcome
– According to the preference rule, MG-2 continues FBALC support on MS-1MS-2 traffic, and
MG-1 disables ALC on MS-1MS-2 traffic
MG2
FBALC
Enc
FBALC
Dec
AEC
AEC
Dec
FBALC
Enc
AEC
Dec
AEC
Enc
IP
MS1
ALC
MG1
Enc: Low bit rate encoder
Dec: Low bit rate decoder
FBALC: Feedback Automatic Level Control
ALC: Automatic Level Control
AEC: Acoustic Echo Control
MG3
MS2
VQE Coordination : After Handover
For Traffic flow from MS1 to MS2



MG-1
– realizes that it is the first and last one with ALC, and it is the first but not the last with AEC on
MS-1MS-2 traffic,
MG-3
– realizes that there is an AEC upstream closer to the source on MS-1MS-2 traffic
Coordination Outcome
– MG-1 continues AEC support on MS-1MS-2 traffic.
– MG-1 dynamically re-enables ALC support on MS-1MS-2 traffic.
– MG-3 disables its AEC.
MG2
FBALC
Enc
FBALC
Dec
AEC
AEC
Dec
FBALC
Enc
AEC
Dec
AEC
Enc
IP
MS1
ALC
MG1
Enc: Low bit rate encoder
Dec: Low bit rate decoder
FBALC: Feedback Automatic Level Control
ALC: Automatic Level Control
AEC: Acoustic Echo Control
MG3
MS2
Generic Network Configuration
MSC-O
MGW-O
SC-T
Server
MSC-T
Server
MGW-T
SPNE-T
BSC-O
Circuit-Switched
network
IP packet network
Land
User
Mobile
Phone
G.MDCSPNE
Q.115.x
Media Path
Signalling Path
Coordination
Voice enhancement
processing functions
Acoustic Echo Control
(AEC)
Noise reduction (NR-O)
for media from the
mobile user
Echo Cancellation (EC)
for Sin from the land
user
Noise reduction (NR-T)
for media from the
land user
MS-O
MGW-O
MGW-T
SPNE-T
Tandeming
(results)
Yes
Yes
No
No
Yes
Yes
Yes
No
No
Yes
Enabled
Disabled
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Disabled
Yes
Enabled
Disabled
Disabled
Disabled
No
No
No
Yes
Yes
Yes
No
No
Disabled
Enabled
No
No
No
Disabled
Enabled
No
No
Yes
Yes
Yes
Yes
No
Yes
Disabled
Enabled
Yes
No
Disabled
Disabled
Enabled
No
(Dynamic coordination) G.MDCSPNE
Q.115.x（Call set-up)
Q
G
Dynamic Coordination of SPNE (G.MDCSPNE)
– current status & future plans

Q18/16 has almost reached consensus on coordination
mechanism and proceeded to discuss detailed designs,

Study on the protocols to exchange Capability Lists are
necessary,

SG16 is asking SG11 and other SDOs for the guidance on the
available protocols, especially for wireless links,

SG11 and other SDOs are invited to liaise with SG16 on these
aspects,

The separation of frame work part and implementationdependent parts have been agreed,

The target date for AAP consent on core part is expected to
be at the SG16 meeting to be held in October 2009.