Constrained Consonant Broadcasting-Constrained Consonant Broadcasting-A Generalized Periodic Broadcasting Scheme A Generalized Periodic Broadcasting Scheme

for Large Scale Video Streamingfor Large Scale Video Streaming

W. C. Liu and Jack Y. B. Lee

Department of Information Engineering

The Chinese University of Hong Kong

ICME 2003

Outline

• Poly-harmonic Broadcasting

• Constrained-Consonant Broadcasting

• Performance Evaluation

Objective

• CCB can be considered as a generalization of the Poly-harmonic Broadcasting scheme incorporating two important constraints, namely client access bandwidth and client buffer requirements.

Notations

Notations

L

B

S1 S1 S1 S1

S2

S3

SN

Harmonic Broadcasting (HB)

• Divide a video into N equally-sized segments

• Each segment Si, for 1 ≤ i ≤ N, is broadcast repeatedly on its own channel with a bandwidth (b/i)

• HB does not always deliver all data on time

Harmonic Broadcasting

– The i th segment of the movie Si is equally divided into i sub-segment(s) {Si, 1, Si, 2 --- Si, i}

– Let the i sub-segment(s) of Si be put on a logical channel Ci, the bandwidth of Ci is b/i.

Harmonic Broadcasting

The total bandwidth(B) allocated for the movie is as follows:

Where HN is called the harmonic number of N

B = b + b/2 + b/3 + b/4 = 2.083b

HN = 1 + 1/2 + 1/3 + 1/4 = 2.083

An illustration of the first three streams for a video under harmonic

broadcasting

Play Rate : b

Receive Rate :b/2

Poly-harmonic Broadcasting

• Two major changes:1) The client STB starts downloading data

from the moment a customer requests a specific video instead of waiting until the customer begins watching the beginning of the first segment.

2) Fixed wait policy.

Poly-harmonic Broadcasting

• Divide the video into N equal segments of duration U=(L/N)

• Segment Si at a transmission rate – Bi = b / (m + i - 1)

• No client can start consuming the S1 of the video before having downloaded data from all N streams during a time interval of duration T = mU, m is an integer 1.≧

• Segment Si will not be consumed until (m+i –1)U time units have elapsed.

Poly-harmonic Broadcasting(m=2)

Poly-harmonic Broadcasting

• The Bandwidth

– If N = k * m

Since T = mU; U= L/N;

T = L/k ; k 愈大 則 waiting time 愈小

Poly-harmonic Broadcasting (PHB)

• Unlike the original HB, the Poly-harmonic Broadcasting scheme guarantees continuous video playback and at the same time can achieve near-optimal performance.

• Provides the same maximum waiting time as harmonic broadcasting protocol while consuming significantly less bandwidth.

Poly-harmonic Broadcasting

• Poly-harmonic Broadcasting requires a client to be able to receive all broadcasting channels simultaneously and has a buffer large enough to store up to 37% of the whole video. difficult to implement!

Constrained-Consonant Broadcasting (CCB)

• Divide the video into N equal segments of duration U=(L/N)

• Target latency T=mL/N=mU

• Classify broadcasting channels into two types, namely Type-I and Type-II channels.

Type-I Channels

• Channels are allocated with progressively less bandwidth as given by

for the ith channel, where n1 is the total number of Type-I channels.

• For Type-I channels, the client is required to start receiving video segments upon entering the system and begin video playback in T seconds.

For m =2,

B0=b/2, B1=b/3, B2=b/4…

Type-I Channels• Solve for n1, such that the following constraints are

satisfied:

• if we remove both the client access bandwidth and client buffer constraintsn1=N, CCBPHB

• This PHB can be considered as a special case of CCB without client access bandwidth and client buffer constraints.

(a)

(b)

Type-II Channels

• Type-II channels are divided into groups of consecutive channels.

• Once a client completes receiving a video segment, the corresponding channel will be released ---begin receiving a new group of Type-II channels.

Type-II Channels

• Let n2,j be the number of channels in group j, of which is created after channel j is released, where j=0,1,…, etc.

• Then the bandwidth allocation for channels in group j is given by

Bj

Bi

Type-II Channels

• Solve for n2, such that the following constraints are satisfied:

(c)

(d)

and

where

Performance Evaluation

Performance Evaluation

Performance Evaluation