Post on 13-Jul-2015
23.05.2012
Roland Schott – Project Manager & Architect, Fixed Mobile Engineering Germany
QoS Strategies for IMS & VoLTE
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Overview.
Introduction
QoS Basic Functions
Fixed Network Approach
Mobile Backhauling
IMS All IP / VoLTE
QoS Functions for EPS
Audio Codices
Conclusions
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Mobile Networks Fixed Networks
Service offering in Europe in 15 countries with 0,6 –82 Mio. inhabitants.
Case Study Germany: QoS functions in mobile networks available.
Service offering in Europe in 11 countries with 0,6 –82 Mio. inhabitants.
Case Study Germany: QoS functions in fixed networks available.
Overview of current Deutsche Telekom Group Networks.
23.05.2012
A VoLTE Solution requires Ubiquity, Flexibility & Quality.
Ubiquity1
Flexibility2
Quality3
Independence of services from access network Integration of legacy networks (e.g. GSM, PSTN) Seamless 2G/3G/4G/WiFi mobility Full int. roaming support in mobile networks
Enables service evolution Fixed-mobile convergence “Docking station” for new applications Various charging options Scalability
Telco-grade Quality-of-Service Security Reliability Fulfilment of regulatory requirements Replacement of legacy CS hardware
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Drivers for IP Data Volume are Broadband-Internet, mobile Internet and Migration to All IP.
QoS Mechanisms can handle increasing Data Traffic appropriate and enable Service Differentiation.
Ref.: Bundesnetzagentur Jahresbericht 2010
Mobile Data Volume Germany
Textbox Headline Mobile data volume in Germany has
increased exponentially.
Broadband data volume has increased linearly.
Always-On services and mobile users are migrating to IP today.
Machine to Machine Communication (automotive, metering) will become an additional driver for IP communication.
M2M (automotive, metering), IMS (Voice services) and IPTV services require appropriate QoS and QoE.
QoS mechanisms are a possibility to operate increasing network bandwidth.
Data Traffic requires appropriate treatment
Textbox HeadlineTraffic Volume Broadband Germany
23.05.2012
QoS Mechanisms on different Levels ensuring QoS in fixed Networks.
QoS means Hop-by-Hop and ensures alone no E2E Quality.
DiffServ QoS traffic classes are always traffic aggregates. No QoS Guaranty for Single-Users.
Required Criteria: Best Effort Traffic without guaranty should be available and droppable.
(E2E QoS Mechanisms like IntServ do not scale in Carrier-Networks).
Traffic Differentiation on Transport Level
Call Admission Control on Control Level RACS / Call Admission Mechanisms
For fixed Networks call admission control mechanisms are available.
RACS (busy tone) implements same look & feel like in PSTN/mobile networks for ensuring voice quality.
Additionally rate adaptive codices help for ensuring voice quality.
Implemented with DiffServ
User AUser B
100Mb/s100Mb/s
100Mb/s
100Mb/s
10Mb/s
10Mb/s10Mb/s
LAN
LAN
LAN
IP-Platform
PSTNSubscriber A
IMS
2
1
3
T-Home
public Roland Schott 6RACS = Ressource Admission Control
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DiffServ is a scalable differentiation mechanism in the IP World.
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Differentiated Service Mechanism & Class of Service
Voice
Gold
Silver
Best Effort
Particular Quality ParameterService Classes
Voice
Gold
Silver
Best Effort
ClassificationClassification
(Re)-Marking(Re)-Marking
Queuing/SchedulingQueuing/
Scheduling
ShapingShaping
PolicingPolicing
Recognition of communication packets authorized for different service qualities
Setting the code point for the traffic class determinedby the classification process
Queue scheduling determines how each queue is served to fulfill priority & bandwidth guarantees.
The (drop) policy determines how to drop packets from the queues when the interface gets congested.
Limits the traffic rate on the outgoing interface.
Example: Possible SLA Values
---------
0.5%40 ms100 ms
3%40 ms60 ms
2%20 ms30 ms
LossJitterDelay
---------
0.5%40 ms100 ms
3%40 ms60 ms
2%20 ms30 ms
LossJitterDelay
AccessBandwidth
Packet Loss
JitterDelay
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QoS Functions can be used for Mobile Backhauling.
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Mobile Backhaul Traffic requires QoS Concept with Service Differentiation
eNodeB
eNodeB
eNodeB
eNodeB
RiFu MPLS
1Gb
1Gb
AGS NT
NT
1Gb 10 Gb
10 Gb
10 Gb
Fixed and mobile traffic are transported over the same MPLS aggregation network.
Aggregation Network supports QoS functionality.
With LTE increasing mobile backhaul traffic is expected.
Differentiating QoS Concept tackles bandwidth situation.
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VoLTE & QoS: LTEe requires a QoS based Voice Solution.
VoLTE & EPC architectural Overview
LTE offers bandwidth for data services of about 100 Mbps downstream.
LTE offer pure IP based data access & requires a voice solution.
The preferred voice solution is a converged one. VoLTE is the IMS based voice solution for LTE.
VoLTE promises lower call setup times compared to CSFB.
LTE offers inherent QoS mechanisms which can be combined with PCC/PCRF functionality for the EPC.
QoS based business models seem feasible in minimum required to distinguish voice from data service.
Characteristics
EPS Solution
Legacy CSMobile Core
IP/ATM/TDMBackbone
other networks
MGW
UTRAN/
GERAN
SMSC SCP HLR
MSC-SSIP/ISCMg/Mj
Rx
Gx
S11
S1-US1-MME
LTE Access S/P- GW
PCRF
CSCF
Cx
Sh
SIP/ISC
MMTEL AS HSS
SGs
MAP CAP
MME
RTP/UDP/IP A, Iu
SIP AS
SIP/ISC
EUTRAN
Possible Architecture - Symbolic Picture
externalIP networks
SGi
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VoLTE has various Levels of Bearer.
End-to-End Service
EPS Bearer External Bearer
E-RAB S5/S8 Bearer
Radio Bearer S1 Bearer
UE eNB S-GW P-GW PeerEntity
Radio S1 S5/8 SGi
E-UTRAN EPC Internet
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Network initiated QoS Control for IP Flows.
QoS enabling via Policy and Charging Control (PCC)
Network-initiated QoS:
dedicated bearer procedure to the terminal e.g. uplink packet filtering
dedicated bearer procedure to the RAN e.g. QoS Info
access agnostic
AF = Application Function
PCRF = Policy and Charging Rules Function
SPR = Subscription Profile Repository
PCEF = Policy and Charging Enforcement Function
BBE = Bearer Binding Function
Characteristics
Application
AccessInterface
AF(P-CSCF)
PCRF
OFCS
OCS
BBE
PCEF
PDN GW
SPR
Rx
Sp
Gx
Gy
Gz
SGiPDN
1. Application Signalling e.g. IMS SIP
2. Session Information e.g. type of service, bit rate
3. Subscription Info
4. Policy Decision
5. PCC Rule
5. Credit management
7. Bearer Binding
Access Network
Core Network
7. Activate & modify bearer
8. Uplink IP flow bearer mapping
8. Service dataflow detection
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Dynamic PCC Rule.
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Referencing PCC rule between PCRF and PCEF
Rule Definition Rule Identifier
List of packet filters for detection of service data flowDetermines order in which service data flows are applied in PCEF
Service Data Flow detection in PCEF Service Data Flow (SDF) Template
Precedence
Indicates gate open/closedPacket Forwarding BehaviourMax. UL/DL bitrates auth. for SDFGuaranteed UL/DL bitrates authorised for SDFARP for the SDF
Policy Control i.e. gating and QoScontrol
Gate StatusQoS Class Identifier (QCI)UL and DL max. bit ratesUL and DL Guaranteed Bit Rates (GBR)Allocation & Retention Priority (ARP) (Pre-emption & CAC)
Charging Key to be applied for SDFRequired Charging Method for PCC RuleIndicates whether SDF data volume, duration etc. shall be measured
Charging Control Charging KeyCharging Method
Measurement Method
Type of Element PCC Rule Element Comment
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Standardised QCI Parameters.
10-2100 ms21 GBR
10-3150 ms42
10-350 ms33
10-6300 ms54
10-6100 ms15 Non - GBR
QCI Resource Type Priority Packet Delay Budget
Packet ErrorLoss Rate
10-6300 ms66
10-3100 ms77
10-6300 ms88
10-6300 ms99
Conversational Voice
Conversational Video (live stream)
Real-Time Gaming
Non-Conversational Video (buffered stream)
IMS signalling
Services
Video (buffered stream) TCP e.g. progressive video,
email, www etc.Voice, Video (live
streaming) interactive gaming
Video (buffered stream) TCP e.g. progressive video,
email, www etc.Video (buffered stream)
TCP e.g. progressive video, email, www etc.
public Roland Schott 13Ref.: 3 GPP
23.05.2012
Service Data Flow Detection & Mapping to downlink Traffic.
Service Data Flow Detection
Association between PCC Rule and bearer is referred to as bearer binding.
Bearer binding is done in Bearer Binding Function (BBF) located in PCEF.
BBF triggers resource reservation in access network and ensures providing of QoSfor authorised QoS of PCC Rule.
A single EPS bearer may be used to carry traffic described by multiple PCC Rules.
BBF maps QCI of PCC Rule (IP Flow related and access agnostic) to EPS bearer QCI of GTP.
Characteristics
Bearer
Bearer
BearerPr
eced
ence Service
Data Flow templates(downlink)
Downlink IP packets from the PDN
for this UE and IP address
No match
No match
no match & discard
match
match
match
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EPS Bearers for PDN Connections.
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EPS Bearers are transport over GTP Tunnels across S1 and S5/8
Application 1
Application 2
UL TFT
UL TFTMME D
L TFTDL TFTGTP Tunnel
GTP Tunnel
eNodeB Serving GW
PDN GW
PDN
IP Flows
Terminal UE PDN connection #1
PDN connection #n
APN,IP address etc.
APN,IP address etc.
EPS Bearer #1Bearer ID,QoS parameters etc.
EPS Bearer #nBearer ID,QoS parameters etc.
TFT
TFT
Filter #1Precedence
Filter #nPrecedence
TFT = Traffic Flow TemplateGTP = GPRS Tunnelling Protocol
Ref.: 3 GPP
23.05.2012
Delay in Packet-Networks influences the Voice Quality.Delay causes echo, MOS do not have to be decreased by Delay necessarily.
Reference: ITU-T
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Comparison of Audio Codices.Audio Codec can increase Voice Quality.
G.711 G.722 AMR WB/G722.2
ILBC
Technology
Audio BW [Hz]
Bit rates [kbit/s]
Frame Length
[ms]
MOS
log PCM
300-3400
48, 56, 64
0,125
Sub-bandADPCM
50-7000
48, 56, 64
0.125 (2 samples)
ACELP
50-7000
6.6, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05, 23.85
20
FB-LPC
300-3400
13.33 (30 ms frames), 15.2 (20 ms frames)
20, 30
Skype (Silk)
4.14bis 4.5
8000, 12000,16000, 24000*
proprietary(IETF)
6 - 40
bis 4.5 4,0 - 4.5
20, 40, 60, 80, 100
4,49
*8000 Hz = Narrow Band12000 Hz = Medium Band16000 Hz = Wide Band24000 Hz = Superwide Band
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Overview Voice Codices.
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Bit Rate
Freq
uenc
y Ba
nd
Enhanced Speech Codec from Skype
Audio CodecCELTfrom Xiph.org
hybr
id
Royalty-free super wideband codices in IETF discussion (OPUS):
SILK
Skype‘s loss-resilient, adaptive-rate codec with sampling rates between 8 kHz and > 24 kHz
CELT
Xiph‘s low-delay, adaptive rate codec, with sampling rates between 32 kHz and 96 kHz, stereo (at 160 kbit/s)
Reference: IETF
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Conclusions.
QoS based function are available for VoLTE & IMS.
DiffServ is the appropriate QoS approach for IP transport.
PCRF is required to handle QoS quality on the mobile access link.
Introduction of innovative audio codices in the IP world offers new opportunities regarding voice quality.
Convergent QoS solution offers synergy effects.