Fountain Coding-based Fountain Coding-based Video Transmission System Video Transmission System

over Heterogeneous Wireless Networksover Heterogeneous Wireless Networks

Presented by

Hyunchul Joo

POSTECH

chul1978@postech.ac.kr

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ContentsContents

Introduction

Proposed Video Transmission System

Experiment Results

Demo

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Many wireless networks with different featuresWLAN networks

Cover small area but support high transmission rate

UMTS networks Cover wide area but support low transmission rate

IntroductionIntroduction

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IntroductionIntroduction

Vertical handoffSwitching technology between different networks to support seamless

service

MN can only access the single network at a time

Needs sophisticated architecture and mutual agreement among network

service providers

Some transition time is inevitable

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IntroductionIntroduction

Path diversityMN establishes multiple paths over multiple wireless networks

AdvantagesParallel transmission

Increase the total bandwidth Disperse the network load

Eliminate the vertical handoff delay Without the cost of cooperation on the network infrastructures

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IntroductionIntroduction

We assume that UDP (User Datagram Protocol) has to be used for

delay sensitive video streaming

The distortion caused by packet loss is more severe than source

encoding rate decreaseThe network path with high packet loss rate is useless until we deploy FEC

(Forward Error Correction) coding such as the fountain code

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Proposed SystemProposed System

Fountain CodeRateless & Erasure code

Generate endless encoded symbols from finite source symbols If a sufficient number of encoded symbols are available, all source symbols

can be recovered although some encoded symbols are lost

Type Online code LT code Raptor code Etc..

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The original data have to be divided into source blocksThe basic unit of fountain coding

Source block size = GOPOne source block impair can affect one more GOPs if the source block is not

synchronized with one GOP

Each source block is divided into source symbols and then applied

to the fountain encoding

Proposed SystemProposed System

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Based on the feedback of receiver, the transmission rate of each

path and the fountain code rate are dynamically determined to

maximize video encoding rate subject to delay and source block

loss constraints

Simple weighted round-robin scheduling is enough to distribute

packets among possible paths because all packets has the same

priority

Proposed SystemProposed System

BW, delay, PLR

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Experiment set-up802.11b and 802.11g networks are used as access technology for each

path

The JM reference software of H.264/AVC and original JM rate control

mechanism are used

CIF format HARBOUR video sequence is adopted as the test sequence The GOP structure is IPPPPPPPPPPPPPP and the number

of frames in a GOP is set to 15

Experiment ResultsExperiment Results

Sender Swi t ch Recei ver

802.11b

802.11g

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Experiment ResultsExperiment Results

The number of successfully received packetsThe number of received packets through proposed system are always

higher than K’

Performance of the proposed system is superior to other cases that

utilize the single path

GOP number

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Experiment ResultsExperiment Results

PSNR comparisonIn RS code systems

When the single reliable path is used, decoding is always successful with

low PSNR value When two paths is used, decoding is sometimes incomplete

Proposed system can provide the smooth video with high quality

because source symbols are always decoded with high PSNR value

GOP number

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Test-bed overall structureJava is used to implement the proposed system

DemoDemo

...

WLAN

HSDPA

HSDPA Modem Manager

WLAN AdapterHSDPA Adapter

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DemoDemo