Analysis of Using Broadcast and Proxy for Streaming Layered Encoded Videos Wilson, Wing-Fai Poon and Kwok-Tung Lo

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  • Slide 1
  • Analysis of Using Broadcast and Proxy for Streaming Layered Encoded Videos Wilson, Wing-Fai Poon and Kwok-Tung Lo
  • Slide 2
  • Contents Introduction System Architecture Analytical Model of the system Results Conclusions
  • Slide 3
  • Introduction (1) Video-on-Demand system has not been commercial success Two directions to provide a cost-effective VoD services: r Multicast/broadcast techniques to share the system resources r Proxy servers to minimize the network transmission cost Multicast/broadcast r Near VoD: Skyscraper, Fast Data, Poly-harmonic r True (zero-delay) VoD: Patching, Stream Tapping
  • Slide 4
  • Introduction (2) Proxy r If the proxy is congested or the requested video is not stored in it, the customer will be served by the central server r Proxy pre-caches a portion/whole of a video to serve the local customers r There is a trade-off between the limited backbone bandwidth and the cost of the local storage
  • Slide 5
  • Heterogeneous Environment Improve the system performance under the homogeneous environment Heterogeneous environment r Use the layered video streams r Flexibly provide different quality of videos by transmitting different number of layers according to the available bandwidth between the server and customers
  • Slide 6
  • Objective Build a large-scale VoD system in heterogeneous network environment Explore hierarchical network architecture to provide VoD services Evaluate the system performance if the network has multicast/broadcast capability Videos are layered encoded r store in the proxy server r broadcast to the customers
  • Slide 7
  • System Architecture Central Repository Wide Area Network Proxy Server Local Area 56 kbps Clients Video data Local Area 1.5Mbps Clients 3 Mbps Clients low quality videos high quality videos Local Area
  • Slide 8
  • r j is the probability of customers requesting the j th quality of the videos The lower quality layers must be first stored before caching the enhancement layer r q mj as the fraction of customers requesting the j th layer of video m Proxy Server b mj as the proxy map to describe the subsets of video layers in proxy set to 1 if layer j of video m is in proxy; otherwise, set to 0
  • Slide 9
  • Proxy Server Maximize: Subject to where
  • Slide 10
  • System Model Requests go up to the central server can be found Average bandwidth requirement for a video request is equal to where
  • Slide 11
  • System Model Model as M/M/N/N queuing system If B is the available bandwidth between the server and the proxy, the number of channels is The service rate of the system is where T is the mean service time P I : percentage of new requests blocked from the central server where
  • Slide 12
  • System Model Proxy server can support some of these customers with lower quality of video streams P II : proportion of new requests completely blocked from the system
  • Slide 13
  • Multicast/Broadcast The proxy is not be able to serve the video requests Layers of the videos can be broadcast over the backbone channels r For example, a customer may receive the base layer of a video from the broadcast channel and the enhancement layers from the dedicated channels r The customer thus at least receives the basic quality of the video even if the network is very congested
  • Slide 14
  • Multicast/Broadcast Layer 4 Layer 3 Layer 1 Layer 2 client1client2 Proxy server Central server Network Broadcasting channels
  • Slide 15
  • Multicast/Broadcast D x as the number of channels required for the broadcasting protocol x g m as the highest layer of video m using the broadcasting scheme r j th layer of video m, where, is either broadcast to the customers or stored in the proxy Bandwidth requirement for broadcasting g m can be calculated such that
  • Slide 16
  • System Model The arrival rate for the dedicated channels can be reduced because some video layers are being broadcast The average streaming rate of the dedicated channels is equal to M/M/N * /N * queue can be applied to calculate the blocking probability of the system
  • Slide 17
  • System Model where
  • Slide 18
  • Simulation Simulation Model r client requests are modeled as the Poisson arrival process r video popularity is followed by Zipfs distribution Three scenarios of requesting quality pattern r Scenario A (S-A): r 5 = 1, r 1 = r 3 = r 4 = r 2 = 0 r Scenario B (S-B): r 2 = r 5 = 0.5, r 1 = r 3 = r 4 = 0 r Scenario C (S-C): r 1 = r 2 = r 3 = r 4 = r 5 = 0.2
  • Slide 19
  • Results (1) Number of videos: 200 Video Length: 90 min Proxy Size: 10 videos Bandwidth: 100Mbps
  • Slide 20
  • Results (2) Number of videos: 200 Video Length: 90 min Arrival Rate: 0.3/s Bandwidth: 100Mbps
  • Slide 21
  • Results (3) Number of videos: 200 Video Length: 90 min Proxy Size: 10 videos Bandwidth: 100Mbps Broadcast: 10 channels
  • Slide 22
  • Results (4) Number of videos: 200 Video Length: 90 min Arrival Rate: 0.5 or 1.0/s Proxy Size: 5 or 10 videos
  • Slide 23
  • Results (5) Number of videos: 200 Video Length: 90 min Proxy Size: 5 videos Broadcast: 10 channels
  • Slide 24
  • Result (6) Number of videos: 200 Video Length: 90 min Arrival Rate: 0.5 or 1.0/s Proxy Size: 5 or 10 videos Broadcast: 10 channels
  • Slide 25
  • Conclusion One of the challenges to provide VoD service is how the video streams can be delivered in the heterogeneous environment Scalability r hierarchical architecture r efficient broadcasting protocols Heterogeneous r Layered encoded videos Bandwidth reserved for broadcasting? Caching policy if proxies can communicate with each other?