an end-to-end adaptation protocol for layered video multicast using optimal rate allocation...
Post on 04-Jan-2016
218 Views
Preview:
TRANSCRIPT
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)
top related