harmonic broadcasting for video-on- demand service enhanced harmonic data broadcasting and receiving...

Harmonic Broadcasting for Video-on-Demand Service

Enhanced Harmonic Data Broadcasting And Receiving Scheme

For Popular Video Service

Li-Shen Juhn and Li-Ming Tseng, Department of Computer Science and Information Engineering

National Central University

Introduction

• In conventional broadcasting scheme, each movie is transmitted sequentially on a video channel.– Suppose there is a popular movie which length

is 120 minutes. If we can allocate 4 video channels to broadcast this movie periodically, the viewers waiting time can be reduce to less than 30 minutes.

Introduction

• Harmonic broadcasting is a scheme, which can reduce the access time to 4 minutes as we allocate 4 video channels for a 120-minute movie

Harmonic Broadcasting Scheme

• Parameters:– Movie length --- D (e.g., 120 minutes)

– Consumption rate of the movie --- b (e.g., 10Mbps)

– Size of the movie --- S = D*b

– The movie is equally divide into N segments, and Si is the ith segment of the movie.

– Viewer waiting time --- d• d = D / N

D

Bandwidth = bS1 S2 S3 S4

d


• Parameters– The ith segment of the movie Si is equally divid

ed 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.


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

Where HN is called the harmonic number of N

d

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

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


S1

S2, 1

S3, 1

S4, 1

d1

S2, 1

d2

S3, 2

S4, 2

S2, 2

t0

d3

S3, 1

S4, 3

S3, 3S3, 2

S4, 4S4, 1 S4, 2 S4, 3

d4

Waiting Time vs. Bandwidth Allocation

• If we allocate HN = 4 video channels to broadcast a popular movie, we have N = 30. Suppose the length of the movie is 120 minutes. The waiting time will be 120/30 = 4 minutes.

Storage Requirements at Client End

• Suppose the time that we begin to load the S1 from C1 is t0. During t0 + (i - 1)*d to t0 + i * d , the sub-segments(s) that come from Ci+1, …, CN, need to be buffered.

Increased data size

Output data size

buffer size required at t0 + i * d

Storage Requirements at Client End

Introduction of Enhanced Harmonic Data Broadcasting Scheme

• In the previous harmonic broadcasting scheme, however, in some cases, the bandwidth utilization can not achieve 100%– Suppose there are 2 free video channels, the

harmonic scheme can only use about 92% of the bandwidth. ( HN = 2 N = 3 1 + ½ + 1/3 = 1.83, 1.83/2 = 0.92 )

Introduction of Enhanced Harmonic Data Broadcasting Scheme

• For a given bandwidth, the enhanced scheme can improve the bandwidth utilization and reduce further the maximum delay, the average delay of the viewers’ waiting time.

Enhanced Harmonic Broadcasting Scheme

• Parameters– Movie Length --- D (e.g., 120 minutes)– Consumption rate of the movie is b (e.g., 10Mb

ps)– The size of the movie is S = D * b– Suppose the bandwidth that we can allocate for

the movie is B = * b, 1 (e.g., B = 15 Mbp, = 1.5)


• Steps– Step1

• Select an integer f (starting index: enhanced factor) and to find the maximum possible integer e (end index) to let

– Step2• Equally divide the movie into N segments, where

N = e – f + 1


• Step3 – The ith segment Si is equally divide into f +i-1

sub-segment(s) {Si, 1, …Si, f+i-1}. Put the f +i-1 sub-segment(s) of Si on a logical channel Ci. The bandwidth of Ci is b / (f+i-1)

• For a given bandwidth, if we select f = 1, the scheme works exactly the same as the original harmonic broadcasting scheme


The actual bandwidth we allocate for the movie is

d: the consumption time of a data segment

d0

Analysis And Comparison

• Viewer’s waiting time and bandwidth utilization– Before we can start to consume the required movie, we

need to download f – 1 sub-segment(s) of S1. min = (f – 1) * d max = f * d ave = (min + max) / 2

• Uncertainty delay = max - min = d

– For a given bandwidth B, we only allocate B’ to broadcast the movie. The bandwidth utilization is,

Analysis And Comparison – The Effect of the Enhanced Factor : f

• For a given bandwidth, we find that both maximum delay and the delay uncertainty will reduce as we increase the enhanced factor f.

f = 1 (original harmonic broadcasting scheme)

f = 2


• However, increase f can not always reduce the average delay

Original harmonic scheme

= 1.5, f = 1

= 2.0, f = 3

Conclusion

• Harmonic and enhanced harmonic scheme has been proved to be optimal with respect to the bandwidth requirement and the viewers’ waiting time

harmonic broadcasting for video-on- demand service enhanced harmonic data broadcasting and receiving...

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