Optimal Stream Replication for Video Simulcasting Jiangchuan Liu, Member, IEEE, Bo Li, Senior Member, IEEE, and Ya-Qin Zhang, Fellow, IEEE IEEE TRANSACTIONS ON MULTIMEDIA, FEBRUARY 2006

Outline Introduction What is video simulcasting? How to improve user satisfaction –Optimization for Fixed Number of Streams (OptFN) –Joint Optimization for Stream Number and Bandwidths (OptNB) Experimental results

Introduction With broadband networks –Real-time video distribution is a important application Ex: multicasting Consideration: –How to handle user heterogeneity? An equal allocation often leads to a waste of bandwidth

Video simulcasting Enables a sender to generate replicated streams of different rates Problems: –Stream redundancy –Bandwidth mismatches (affects the user satisfaction) Goal: –Strike a balance between bandwidth and user satisfaction Use a optimal and efficient solution –to choose an appropriate number of streams –to allocate bandwidth to reduce bandwidth mismatches for all the receivers

System model In overlay multicast networks A server –Has higher output bandwidth –uses simulcasting technique to distribute a set of video programs The receiver –has heterogeneous bandwidth

System definitions(1/2) Session (s): a video program (including the replications) and the receivers Session bandwidth (N s ): bandwidth allocated to the session The status of the system (C, P, M s,t ) Bandwidth mismatch –Use relative measure (RM) Assume a receive bandwidth t, and the bandwidth of its stream is r C: the maximum outbound bandwidth of the server P: the total number of sessions M s,t : the ratio of the receives having bandwidth t in session s

System definitions(2/2) : bandwidth allocation for session s r s,i : the rate of stream i =(r s,1, r s,2, …, r s,ls ), r s,1 < r s,2 <, …, < r s,ls l s : the total number of the replicated streams Best-matching bandwidth How to determine on the server’s side? –intra-session allocation

Intra-session allocation Input: –session bandwidth N s –receivers’ bandwidth distribution M s,t Output: –Minimum expected relative mismatch (ERM) T S : the maximum receiver bandwidth in session s

Optimization for Fixed Number of Streams (OptFN)(1/2) Assume –The number of streams is fixed to a given K –A total number k(≤ K) streams are generated With a total bandwidth n Bandwidth of stream k is m Ex: if k = 1, and 0 < m = n ≤ N s ;

Optimization for Fixed Number of Streams (OptFN)(2/2) When stream k is added –Depend on the bandwidth of stream k and k-1 If bandwidth of stream k = m, and that of stream k-1 = j; –Minimum ERM is to checking all possible j(=1,2,…m-1) The solution to problem OptFN is

Joint Optimization for Stream Number and Bandwidths (OptNB)(1/2) Both the number of streams (l s ) and their bandwidth (r s,i ) are to be optimized Given an upper bound of l s Minimum ERM is to try l s from 1 to –With session bandwidth n –Bandwidth of stream l s is m

Joint Optimization for Stream Number and Bandwidths (OptNB)(2/2) For some constraint, m<n≤N s, 1<m ≤min{n,T s } The solution to problem OptNB

Evaluation results Simulation subjects include: –A fixed number of streams (ExpFN) S. McCanne, V. Jacobson, and M. Vetterli, “Receiver-driven layered multicast,” in Proc. ACM SIGCOMM’ 96, Aug J. Liu, B. Li, and Y.-Q. Zhang, “A hybrid adaptation protocol for TCPfriendly layered multicast and its optimal rate allocation, ”in Proc. IEEE INFOCOM’02, Jun –Optimization for Fixed Number of Streams (OptFN) –Joint Optimization for Stream Number and Bandwidths (OptNB) Assume both the minimum and the maximum receiver bandwidths are known –Assume the session has 500 receivers –Their bandwidth are distributed in w clusters Follow a Gaussian distribution

Effect of session bandwidth(1/2) In w = 3

Effect of session bandwidth(2/2) In w = 6

Impact of the number of streams If K is small, the receivers’ choice is limited and the adaptation is not flexible

Perceived video quality (1/2) Use the standard MPEG-4 video encoder with TM-5 rate control The test sequence is “Foreman (CIF)” In w = 3

Perceived video quality (2/2) In w = 6

Video 1 Video simulcasting client Server Proxy Video 1 client BW: 0.5MB BW: 1.5MB BW: 3MB BW: 1MB BW: 1.5MB BW: 2MB Video 1 Can ’ t receive video 1 Video 1 Stream redundancy Bandwidth mismatches