qos strategies for ims & volte

23.05.2012

Roland Schott – Project Manager & Architect, Fixed Mobile Engineering Germany

QoS Strategies for IMS & VoLTE

public Roland Schott 1

23.05.2012public Roland Schott 2

Overview.

Introduction

QoS Basic Functions

Fixed Network Approach

Mobile Backhauling

IMS All IP / VoLTE

QoS Functions for EPS

Audio Codices

Conclusions


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



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

23.05.2012

DiffServ is a scalable differentiation mechanism in the IP World.


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

23.05.2012

QoS Functions can be used for Mobile Backhauling.


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.


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

23.05.2012

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


23.05.2012

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


23.05.2012

Dynamic PCC Rule.


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

23.05.2012

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


23.05.2012

EPS Bearers for PDN Connections.


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


23.05.2012

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


23.05.2012

Overview Voice Codices.


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


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.

qos strategies for ims & volte

Documents

mobile networks available

appropriate qos

qos guaranty

fixed networks available

e2e qos mechanisms

ip volte qos functions

mobile internet

mobile users