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Streaming of Scalable Video over UMTS Kamal Deep Singh April 2006

Streaming of Scalable Video over UMTS - IMT Atlantiquedepartements.imt-atlantique.fr/data/sc/seminaires/seminaire_deep... · Streaming of Scalable Video over UMTS ... Buffer management

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Streaming of Scalable Video

over UMTS

Kamal Deep Singh

April 2006

AGENDA

� Overview

� State of the Art

� Open Issues

� Possible Approaches

AGENDA

� Overview

� Video streaming over UMTS

� UMTS Enhancement: HSDPA

� Scalable Video Codec

� State of the Art

� Open Issues

� Possible Approaches

Streaming of Scalable Video over

UMTS

UMTS

Core

Network

UMTS

Core

Network

Feedback

Node B

RNC

Video server in

Internet

Video

Client

UMTS

network

Streaming of Scalable Video over

UMTS: UMTS Enhancement

Streaming of Scalable Video over

UMTS …

� Focus on the last link (UMTS): Bottleneck� Scarce & Variable Bandwidth

� Wireless Losses

� Internet is initially assumed to be ideal

� Use of Recent Video Codecs

Streaming of Scalable Video over

UMTS …

� Scalable Video Codec (MPEG-4 SVC)

� Flexible Bit-Rate adaptation with graceful change in Quality

Video Data

Increasing Bit-Rate

Decreasing Quality

AGENDA

� Overview

� State of the Art

� QoS in wired networks: Diffserv

� Streaming of MPEG-2 & H.264

� Open Issues

� Possible Approaches

State of the Art: QoS in the Wired network

� IETF has defined an architecture for differential service (DIFFSERV)

� Diffserv Per-Hop-Behaviors:

� Best Effort: Current Internet

� Expedited Forwarding: Topmost priority

� Assured Forwarding: Classification & Discard probabilities

� Packets are marked: Green, Yellow, Red

� Green packets are given most priority and Red packets are given the least priority

State of the Art: Video Codecs

� MPEG-2 & H.264� Constant Bit-Rate

� Some packets are more important than the others

� I, P and B frames: � I frames are the most important and B frames are the least important

� Simple Diffserv-aware marking

� I � Green; P � Yellow; B �Red

� Drop Red packets on Congestion & Protect Green packets

AGENDA

� Overview

� State of the Art

� Open Issues

� QoS in UMTS

� Congestion Control

� Scalable Video Codec

� Possible Approaches

Open Issues : In General

� UMTS Network� Is different from Wired Network

� Variable Bandwidth

� Scarce Bandwidth� Users should use congestion control

� Wireless Losses

� How to do Congestion control for Video?� When many users share the same resources

� How to provide QoS in UMTS?

Open Issues : In General …

� Scalable Video Codec (MPEG-4 SVC)

� How to do QoS/Diffserv mapping (coloring)?

� No straight-forward mapping like : I � Green; P � Yellow; B �Red

Open Issues : General Picture

UMTS

Network

UMTS

Network

Feedback

Node B

RNC

How to color packets for almost ideally scalable

Video?

How to provide end to end congestion control for video

streaming over networks like UMTS?

How to Provide QoS in

UMTS network?

Video server

AGENDA

� Overview

� State of the Art

� Open Issues

� Possible Approaches

In Context of Different Layers

� IP LAYER:

� To provide QoS in UMTS network

� TRANSPORT LAYER:

� Congestion control over UMTS network

� APPLICATION LAYER:

� QoS/Diffserv coloring of scalable video

IP LAYER

� Quality of Service (QoS) : Basics� Priority to important traffic

� Differentiation of service

� Limiting traffic through Service Level Agreements (SLAs)

� Hard bit-rate constraints � User A will not transmit more than 100kbps of green packets

� Soft constraints through Pricing� Green packets will cost c cents per kilobytes

� Guarantees of bit-rate, delay, losses

IP LAYER …(Impact of MAC layer)

� QoS in UMTS: Impact of Packet Scheduling strategies

User 1

User 2

Node B

Channel Quality feedback

MAX C/I Scheduler gives the channel to best user

IP LAYER …(Impact of MAC layer)

� QoS in UMTS: Impact of Packet Scheduling strategies…

Increased fairness among users

Increased Cell Capacity

Fair throughput scheduling

Proportional Fair scheduling

Max C/I scheduling

IP LAYER …

� QoS in UMTS: Problems and Solutions

� How to implement 4 QoS classes of UMTS?

� How to use the available schedulers?

� Variable Bandwidth

� Problems:� Difficult to implement Hard bit-rate constraints

� Difficult to give guarantees for bit-rates

� Solutions� Soft constraints like Pricing are possible

� Dynamic SLAs

Work in Progress

IP LAYER …

� QoS through Buffer Management

� RED (Random Early Detection)

� Proactive Dropping: Doesn’t wait for buffer to become full

� Controls Delay: Stabilizes the queue length to a target value

IP LAYER …

� QoS through Buffer Management …

� RIO (RED In and Out) for Diffserv

� Differential dropping (Green, Yellow & Red)

IP LAYER …

� QoS through Buffer Management …

� Problems:

� Strategies like RED will not be efficient

� Per user queues (unlike wired network)

� Variable Link Bandwidth creates problem in setting RED parameters

� No use in stabilizing “queue length (q)” because Bandwidth is variable

IP LAYER …

� QoS through Buffer Management …

� Solutions: Per user queues make things easier

� Each Queue will hold only Few flows (1 flow..)

� ECN (Explicit congestion Notification) can be used.

� To notify end users to reduce their rate

� Users will not be able to cheat because of per user queues

� Adapting RED to variable bandwidth using control theory

� A new buffer management scheme adapted to UMTS

Work in Progress

Work in Progress

TRANSPORT LAYER

� Congestion Control� Confusion between Congestion and wireless losses

� WLED (Wireless loss estimation in Diffserv networks)

� Green packets will not be dropped during congestion

� Wireless losses and green losses will be correlated

� ECN can be used to differentiate losses

� Congestion control for Video

� TCP

� TFRC

� KELLY Control

Done

TRANSPORT LAYER …

� TCP� Many things to learn from TCP

� Current stability of internet is due to TCP

� Good approach for tackling congestion

� Not suitable for Video transmission � “Some” retransmissions are a waste

� Video can tolerate errors

� Oscillation in throughput is undesirable for Video transmission

TRANSPORT LAYER …

� TFRC (TCP Friendly Rate control)

� TCP Friendly as it tries to imitate TCP in a smooth way

� Rate is based on an equation:

� Receiver sends feedback at least once per RTT

� Feedback can contain loss event rate or the Rate itself

TRANSPORT LAYER …

� TFRC …� TFRC with UMTS/HSDPA

� High Jitter � causes NO-ACK timeouts

� TFRC decreases its throughput

� RTT estimation not optimal

� Do a simulation study of TFRC using EURANE platform (UMTS-HSDPA)

� Some TCP strategies that solve jitter issues can be tested with TFRC

� NO-ACK timer can be increased

� RTT estimation can be modified

� Reduce Jitter through buffer management

Work in Progress

TRANSPORT LAYER …

� Kelly Control� The idea is to model end-users as an optimization, game theoretic problem

� Assume each user i derives utility Ui(xi) from the network by obtaining throughput xi

� User’s Game

� Assume that each user is willing to pay price wi for using the network and that it receives throughput proportional to wi: xi = wi / λi

(λi is charge per unit flow for user i)

� Max [Ui(wi / λi) - wi]

� Network’s Game

� Max ∑wilogxi subject to ∑ Rij xi ≤ Cj , i, j

TRANSPORT LAYER …

� Kelly Control …� Network is not a centralized entity, so a solution in a distributed fashion

� This can be achieved by the end user equations:

dxi(t) / dt = k(wi – xi(t) ∑ Rijpj(t) )� Where k > 0 is a constant and pj is the price charged by the router j for using its resources

pj(t) = pj(∑ Rkjxk(t))� In real network we can replace price with packet loss feedback

APPLICATION LAYER

How to color the packets and how to represent the

Video?

� Packet Coloring Problem

APPLICATION LAYER …

� Scalable Video Representation [Chou01]

� Divided Video into data units connected by an Acyclic graph

� Rate-Distortion Optimized streaming

APPLICATION LAYER …

� A new transport protocol can be designed

� Selectively retransmits the data depending on its importance

� Receiver has a Play out buffer of 1 to 8 seconds

� Important packets can be retransmitted

APPLICATION LAYER …

� Packet coloring approaches

� Cost-Quality Optimization

� Consider “green” channel as costly but more reliable

� Consider “red” channel as cheap but lossy

� Optimize streaming between these channels

� Other approaches

� Let red packets bear the rate fluctuations and Protect green packets from congestion

Summary of Work in Progress

� HSDPA pricing

� Buffer management in UMTS

� Congestion Control for Video

� Packet Coloring

� Some Simulation studies� Study of TFRC over HSDPA

� H.264 & SVC streaming over HSDPA using simulations

� HSDPA channel model using Markov chains