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, IEEE IEEE 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 l Layer 3 Layer 1 Layer 2 … Layered Video Base layer Enhancement Layer … b1b1 b2b2 b3b3 blbl The layer rates are given by Let denote the cumulative layer rate up to layer, that is, c1c1 c2c2 clcl denote the rate vector of the cumulative layers, 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 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. SR Sender Report(SR) :

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 expected bandwidth.  Main operation of receiver’s

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 congestion  To avoid persistent congestion, if the loss rate p exceeds a threshold, a receiver has the flexibility to leave the highest layer being subscribed. Receiver 1 Receiver 2 Receiver 3 Receiver 4 SR persistent congestion RR - Response Report(RR) = - RR serves as a request for RTT estimation

Sender-based Dynamic Rate Allocation  Optimization Criteria for Heterogeneous Receivers  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 expected bandwidth as follows: This definition can be used to access the satisfaction of a receiver when there is a performance loss incurred by a mismatch between the discrete set of the possible receiving rates and the expected bandwidth.

 Nonlinearity can be characterized by a utility function we 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 QP value = { x,y.z ….} : a finite set of admissible quantizers R1 R2 R3 RMRM … R1 R2 R3 RMRM … …

Optimal Allocation Algorithms(1/3)  Assume, the expected fairness index can be calculated as follows: Layer l Layer l-1 Subscription level of receiver’s Sender Receiver

Optimal Allocation Algorithms(2/3)  Let : the maximum expected fairness index when c l is set to the mth operational point, R m  Recurrence relation R1 R2 RlRl

Optimal Allocation Algorithms(3/3)  according to the definition of and the recurrence relation, the following inequation holds for all nonnegative and nondecreasing >= 0

Parameter Measurements and Local Coordination  Estimation of Round-Trip Time(1/2)  Obtaining an accurate and stable measurement 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 conclusions.  Using two mechanism Closed-loop RTT Open-loop RTT the sender does not give a response to each 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 Coordination  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 t 0 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 cumulative layer rate without joining and leaving.

Simulation Result(2/2)