An End-to-End Adaptation Protocol for Layered Video Multicast Using Optimal Rate Allocation

Jiangchuan Liu, Member, IEEE, Bo Li, Senior Member, IEEE, and Ya-Qin Zhang, Fellow, IEEEIEEE TRANSACTIONS ON MULTIMEDIA, VOL. 6, NO. 1, FEBRUARY 2004

Paper Overview

Abstraction cotent

Paper Overview

Hybrid Adaptation Protocol For Layered Multicast(HALM) Sender Functionality(1/2)

Layered Encoder

Layer lLayer 3

Layer 1

Layer 2

…

Layered Video

Base layer

Enhancement Layer

, i =1, 2, 3, ... , .ib l

…

b1

b2

b3

bl

The layer rates are given by

Let denote the cumulative layer rate up to layer , that is,

jc

, 1, 2,...,l

j ii

c b j l

c1

c2

cl

denote the rate vector of the cumulative layers,

1 2( , ,..., )l lc c c

l

discrete set offers all possible video rates that a receiver in the session could receive

the maximum rate delivered to a receiver with an expected bandwidth thus will be

r

( , ) max{ : , )l lr c c r c

Expected BW :

Receiver 1

Receiver 2

Receiver 3

Receiver 4

The sender will adaptively allocate the layer rates based on the distribution of the receivers’ expected bandwidths.

SRT s

SR

Sender Report(SR) : < SSRC, Stime, ,Response Reqeust >l

Hybrid Adaptation Protocol For Layered Multicast(HALM) Sender Funtionality(2/2) We assume a rate vector is different from the

one in the previous control period (in case they are the same, the sender can offset the current vector by a small value).

Hence, the change of the rate vector can serve as an implicit synchronization signal to trigger the receivers’ joining/leaving actions.

Hybrid Adaptation Protocol For Layered Multicast(HALM) Receiver Functionality(1/3) To be friendly to TCP, a receiver directly uses a

TCP throughput function to calculate its ex-pected bandwidth.

Main operation of receiver’s

: packet size

: round-trip time

: retransmit timeout value

: steady state loss event rate

s

RTT

RTO

p

Hybrid Adaptation Protocol For Layered Multicast(HALM) Receiver Functionality(2/3) Advantages

First, it is TCP-friendly because the rate is equivalent to or less than the long-term

throughput of a TCP connection running over the same path.

Second, it is scalable because the receivers’ joining/leaving actions are

synchronized cf) RLM : shared learning

Finally, it is very robust because the implicit signal will be detected even if

some SR packets are lost.

Hybrid Adaptation Protocol For Layered Multicast(HALM) Receiver Functionality(2/3) Configuration of Loss event parameter

In highly dynamic network environment network load change during the interval persistent con-

gestion To avoid persistent congestion, if the loss rate p ex-

ceeds a threshold, a receiver has the flexibility to leave

the highest layer being subscribed.

Receiver 1

Receiver 2

Receiver 3

Receiver 4SRT s

SR

persistent congestionRR

- Response Report(RR) = <SSRC, expected bandwidth>- RR serves as a request for RTT estimation

RRT s

Sender-based Dynamic Rate Allocation Optimization Criteria for Heterogeneous Re-

ceivers Total Throughput ??? Fairness Index ???

with a cumulative subscription policy the subscription level of a receiver relies on its

expected bandwidth and the set of cumulative layer rates.

Fairness Index for a receiver with ex-pected bandwidth as follows:

This definition can be used to access the satisfaction of a re-ceiverwhen there is a performance loss incurred by a mismatchbetween the discrete set of the possible receiving rates and theexpected bandwidth.

Nonlinearity can be characterized by a utility functionwe define an Application-aware Fairness Index

For a multicast session, our objective is to maximize the expected fairness index , for all the receivers in the session by choosing an optimal layer rate vector.

where L is the maximum number of layers that the sender can manage.

The complexity of this optimization problem can be further reduced by considering some characteristics of a practical layered coder. Assume there are M operational points the set of

operational rates is given by 1 2 1={ , ,...., : }M i iR R R R R

QP value = { x,y.z ….} : a finite set of admissible quantizers

R1

R2

R3

RM

…

R1

R2

R3

RM

…

…

Optimal Allocation Algorithms(1/3) Assume ,

the expected fairness index can be calculated as follows:

Layer l

Layer l-1

Layer l-1

Subscription level of receiver’s

Sender

Receiver

Optimal Allocation Algorithms(2/3) Let

: the maximum expected fairness index when cl is set to the mth operational point, Rm

Recurrence relation

R1

R2

Rl

Optimal Allocation Algorithms(3/3) according to the definition of and the re-

currencerelation, the following inequation holds for all

nonnegative and nondecreasing >= 0

Parameter Measurements and Local Co-ordination Estimation of Round-Trip Time(1/2)

Obtaining an accurate and stable measure-ment of the round-trip time is of primary importance for HALM

To find the “true RTT”, we must use a feedback loop Feedback mechanism

Many receiver’s & high frequency(BW??) : cause implosion at the sender

Many receiver’s & low frequency(BW??) : inaccurate conclu-sions.

Using two mechanism

Closed-loop RTT

Open-loop RTTthe sender does not give a re-sponse toeach request but uses a batch process.

The open-loop estimation method tracks the one-way trip time from the sender to the receiver and transforms it to an estimate of RTT.

Parameter Measurements and Local Co-ordination Estimation of Round-Trip Time(2/2)

Timing diagram for closed-loop and open-loop RTT estimations

Note that an RTT estimate can be expressed as is the one-way trip time from the sender to the receiver and is the time from the receiver to the sender.

where t0 and t’ are the current local time and the local time that the request was initiated, respectively.

Simulation Result(1/2) Simulation Topology & Distribution of cumula-

tive layer rate without joining and leaving.

Simulation Result(2/2)