Smooth Workload Adaptive Broadcast Yang Guo, Lixin Gao Don Towsley, Subhabrata Sen IEEE TRANSACTIONS ON MULTIMEDIA, APRIL 2004

Outline Introduction Workload adaptive broadcast architecture Flexible Periodic Broadcast Smooth Transition Property Performance Evaluation Conclusion

Introduction Develop bandwidth-efficient techniques for –Delivering popular video –To a large, asynchronous client population –With time-varying demand characteristics In the past, PB (Periodic Broadcast) scheme was used

Drawbacks of PB scheme Workload insensitivity –Not adapt to changing workload demands Delayed playback –Clients experience a playback delay

What desirable in this scheme ? Parsimonious transmission –Transmits a segment only if required Workload adaption –Dynamically adjusts the number of channels Instantaneous playback –Enables instantaneous or near-instantaneous playback

Related Work Compare to “Data broadcasting and seamless channel transition for highly- demanded video” –Advantage: smooth channel transition property –Disadvantage: It require the client to listen to all channels simultaneously Without using parsimonious transmission, so become inefficient when a video turn to unpopular

Workload adaptive broadcast architecture 1 2 request ClientServer 2 1 unicast multicast 1.Modified PB scheduler 2. Workload adaptor

Modified PB Scheduler BBBBBBBB B BBB (multicast) Instantaneous playback (unicast) AA Client 1Client 2 Parsimonious PB (multicast) Near-Instaneous playback (multicast)

Workload Adaptor Determine optimal channel number depend on the arrival rate and video length

Workload Adaptor – : the arrival rate after the n-th update period – : the number of arrivals during n-th period – : the weight – : the period length W, the average arrival rate converges to the current arrival rated more quickly

Flexible Periodic Broadcast Fn : Channel n is responsible for delivering Fn consecutive segments to clients

Server Transmission schedule Suppose FPB use K channels to transmit a video clip of length L Start rule : n-th channel start transmission after (n-1)-th channel complete the transmission of segments Repeat Rule : Each channel repeat its transmission schedule once every segments

Server Transmission Schedule Transmission schedule within a period: –For channel n, n=2,3,…,K-1, the transmission schedule comprises K-n+1 batches of segments –The first batch consists of segments Ex. K=6, n=3, -> [3+1,6] -> (4,5,6) –The second batch, the same as the leading segments in the first batch -> (4,5) –Batch i,,consist of segments contained in the previous i-2 batches, from batch 1 to batch i-2 -> (4,5,6) (4,5,6,4,5)

Server Transmission Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 5-channel cluster 6-channel cluster

Client Reception Schedule

,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 5-channel cluster 4-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 5-channel cluster 4-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 4-channel cluster 3-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 4-channel cluster 3-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 3-channel cluster 2-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB 3-channel cluster 2-channel cluster TP Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB T,P Wanted segments

Client Reception Schedule ,2,3,5,8, Channel 3 Channel 1 Channel 4 Channel 5 Channel 6 Channel 2 Six-channel cluster and its sub-cluster in FPB T,P Wanted segments

Smooth Transition Property The clients already starting their service not experience any disruption during the transition The newly arrived clients make use of the FPB scheme with K’ channels The total number of channels used during the transition period is no larger than max{ K, K’ }

Smooth Transition Property

Performance Evaluation Comparison of PB scheme (requiring clients listen to two channels)

Performance Evaluation Efficiency of Parsimonious FPB

Performance Evaluation Performance of the smooth workload adaptive scheme single video case

Performance Evaluation Performance of the smooth workload adaptive scheme single video case

Performance Evaluation Performance of the smooth workload adaptive scheme multiple video case

Conclusion Present –a workload adaptive broadcast architecture and –smooth workload broadcast based on FPB –To provide VoD service to a large, asynchronous client population with time- varying workload