Title: 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
1An End-to-End Adaptation Protocol for Layered
Video Multicast Using Optimal Rate
AllocationJiangchuan Liu, Member, IEEE, Bo Li,
Senior Member, IEEE, and Ya-Qin Zhang, Fellow,
IEEEIEEE TRANSACTIONS ON MULTIMEDIA, VOL. 6, NO.
1, FEBRUARY 2004
2Content
- Paper Overivew
- Objective
- Key Issues
- Motivation of Paper
- Related Works
- TCP-Friendliness
- Layered Video Multicast
- Rate Adaptation Allocation
- Sender-side functionality
- Receiver-side functionality
- Simulation Result
3Paper Overview
4Objectives
- Problem
- Multicasting ?, coarse-grained layer subscription
levels? heterogeneous? ??? ???? ???? rate ??
???(mismatches) - To solve this problem
- Sender-side support to dynamic and fine-grained
layer rate allocation - Rate allocation/layer ? ?? ?? ??(??)? ???? ??.
- Application-aware Fairness index
- Works 1 ??? rate allocation? ??, multicast
session? ?? ?? ???? expected fairness index?
maximization ??? ??? ??? optimization problem?
formulate ??. - Works 2 ???? scalable solution HALM(Hybirid
Adaptation Layered Multicast)? ???? - HALM Profit
- It can be seamlessly integrated into an
end-to-end adaption protocol. - This protocol takes advantage of the emerging
fine-grained layered coding(2004??) and is fully
compatiable with the best-effort internet infra-.
5Key Issues
- Two key issues.
- Dynamic allocation layer rate allocation can be
an effective. - Practical complement receiver-driven
adaptation. - Question
- What are the proper criteria for optimal
allocation? - How to derive an efficient algorithm for the
optimal allocation? - How to design an integrated adaptation protocol
using the optimal allocation?
6Motivation of this paper(3/3)
- Real-time video transmission has to adapt to
dynamic network conditions - For Adaptation
- In traditional Unicast usually done by the
sender, which collects the receivers status via
a feedback alg. and adjusts its transmission
rate - In Multicast single rate? ??? ??? ??? ???
users(required BW? ? ??? ??)? ????? ? ??. - ? ??? multicast? fair distribution? ?? multi-rate
multicast ??? ???. - Fair distribution? ? receiver? ??? ?? ???
required BW? ?? ???? ????, ??? capacity? ???
rate? ???? ???. - ?? ?? ??? multicast session ? member? ????
fairness ? ??? ??? ??? fair distribution ???
intra-session fairness ? ???.
7Motivation of this paper(2/3)
- A commonly used multi-rate multicast approach is
cumulative layered transmission - raw video ? layered encoding transmission
(base, Enhancement layer). - As an example, layers can be mapped to different
IP multicast groups - disadavantage
- ????? layered encoder? ???? layer? ??? ??? ??,
receiver?? ??? ???? ?? required BW? ?? control? ?
?? layer?? control ??? ???. - ?? ?? ?? remarkable fairness degradation? ????.
8Motivation of this paper(3/3)
- To mitigate this problem,
- one possible solution is the use of fine-grained
sender adaptation as a complement, i,e.,
dynamically allocating the layer rates. - First, the source coder should have the ability
to control the layer rate. - Second, the sender should know the global state
of the receivers.
9Related Works H.264/AVC Extension
- FGS functionality has been removed from the SVC
specification that is still under development
(SVC amendment will be finalized by the
next(Geneva) JVT meeting beginning of July 07)
10Related WorksTCP-Friendliness
- TCP?real-time video delivery protocol? ???? ???.
- Why? Because these applications usually require a
smoothed transmission rate and stringent
restrictions on end-to-end delay. - ???? internet traffic? TCP?? video streaming
protocols? ????? ??? TCP flows? ?? ??? ??? ?? ??
??? video traffic? ???? ?? ? ?? rate control
algorithm? ????.
11Related WorksDesign of TCP-Friendliness
- Note that, short-term adaptation results in
bandwidth oscillations, which is not desirable
for video transmission. - Thus our objective is to provide an adaptive
protocol that will not starve background TCP
traffic and, meanwhile, try to achieve a
long-term fair share as close as possible.
12Related WorksLayered Video Multicast
- Receiver-driven Layered Multicast (RLM) is a pure
end-to-end adaptation protocol - It sends each video layer over a separate
multicast group. - A receiver periodically joins a higher layers
group to explore the available bandwidth. - Congestion detected join-experiment
- Shared learning mechanism suppress to join
experiment by other receivers
13Rate Adaptation Allocation
14Hybrid Adaptation Protocol For Layered
Multicast(HALM) Sender Functionality(1/2)
Layered Video
Layered Encoder
denote the rate vector of the cumulative layers,
Layer l
bl
cl
Enhancement Layer
discrete set offers all possible video rates that
a receiver in the session could receive
Layer 3
b3
Layer 2
b2
c2
the maximum rate delivered to a receiver with an
expected bandwidth thus will be
Layer 1
b1
c1
Base layer
The layer rates are given by
Receiver 1
Receiver 2
Let denote the cumulative layer rate up to
layer , that is,
Receiver 3
SR
Receiver 4
Expected BW
The sender will adaptively allocate the layer
rates based on the distribution of the
receivers expected bandwidths.
15Hybrid 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.
16Hybrid 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 receivers
17Hybrid 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.
18Hybrid 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
SR
Receiver 4
persistent congestion
- Response Report(RR) ltSSRC, expected
bandwidthgt - RR serves as a request for RTT
estimation
RR
19Sender-based Dynamic Rate Allocation(1/3)
- 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.
20Sender-based Dynamic Rate Allocation(2/3)
- 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.
21Sender-based Dynamic Rate Allocation(3/3)
- 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
RM
RM
R3
QP value x,y.z . a finite set of
admissible quantizers
R3
R2
R2
R1
R1
22Optimal Allocation Algorithms(1/3)
- Assume ,the expected fairness index can be
calculated as follows
Receiver
Layer l-1
Sender
Layer l
Layer l-1
Subscription level of receivers
23Optimal Allocation Algorithms(2/3)
- Let the maximum
expected fairness index when cl is set to the mth
operational point, Rm - Recurrence relation
Rl
R2
R1
24Optimal Allocation Algorithms(3/3)
- according to the definition of and the
recurrencerelation, the following inequation
holds for all
nonnegative and nondecreasing gt 0
25Parameter 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 receivers high frequency(BW??) cause
implosion at the sender - Many receivers 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.
26Parameter Measurements and Local Coordination
- Estimation of Round-Trip Time(2/2)
- Timing diagram for closed-loop and open-loop RTT
estimations
where t0 and t are the current local time and
the local time that the request was initiated,
respectively.
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.
27Simulation Result(1/2)
- Simulation Topology Distribution of cumulative
layer rate without joining and leaving.
28Simulation Result(2/2)