Presentation on theme: "1 Layered Video for Incentives in P2P Live Streaming Zhengye Liu Yanming Shen Shivendra Panwar Keith W. Ross Yao Wang Polytechnic University, Brooklyn,"— Presentation transcript:
1 Layered Video for Incentives in P2P Live Streaming Zhengye Liu Yanming Shen Shivendra Panwar Keith W. Ross Yao Wang Polytechnic University, Brooklyn, NY, USA
File Distribution: BitTorrent obtain list of peers trading chunks tracker peer
BitTorrent: Incentive Question: What is the incentive to provide higher upload rate? Answer: To get file faster Implementation: Tit-for-tat mechanism. Search for trading partners that upload to you at higher rates
BitTorrent: Trading Alice measures rate she receives bits from each neighbor. Alice sends chunks to four best neighbors. Every 10 seconds, she recalculates rates & possibly modifies set of four peers. Every 30 seconds, she optimistically unchokes random peer.
BitTorrent: Trading (1) Alice optimistically unchokes Bob (2) Alice becomes one of Bobs top-four providers; Bob reciprocates (3) Bob becomes one of Alices top-four providers With higher upload rate, can find better trading partners & get file faster!
obtain list of peers trade chunks tracker peer Basic idea P2P live streaming Source of video
Incentives for Live Streaming Why upload at all? –Currently no tit-for-tat mechanism in existing deployments Is tit-for-tat a sufficient incentive? –No! Why provide more upload bandwidth if youre receiving the video at the full rate? Our main idea: –If you upload more, you get better quality.
Layered Video Single layer Video –All peers receive the same video quality Layered video –A video is encoded into several layers –More layers introduce better video quality –Nested dependence between layers Higher upload contribution results in better received video quality
Layered Video w/ Tit-for-Tat Generate multiple layers, each divided into layer chunks (LCs) Exchange LCs Measure download rates from neighbors Reciprocate to neighbors based on their contributions
Supplier & Receiver Side Schedulers Supplier: How to allocate uplink bandwidth to neighbors? –BitTorrent roughly gives each unchoked neighbor an equal share. Receiver: How to maximize the received video quality –Multiple LCs are to be requested
Supplier Side Scheduler Goal: Supply neighbors in proportion to their contributions Measure the download rates, d k from neighbor k Maintain separate FIFO rqst queue for each neighbor Serve neighbor k next with probability:
Receiver Side State Request LCs at beginnings of rounds Can request in a window up to B chunks into future
Receiver Side Scheduler (1) Goal: Maximize the received video quality Which LC should be requested first? Assign heuristic importance to each LC, taking into account: –Layer index –Playback deadline –Rareness Request LCs from the highest importance to the lowest importance
Receiver Side Scheduler (2) Where to send the request for the LC? Estimate the current delay from each neighbor: where m k is # of outstanding requests, r is video rate, Δis chunk length Send request to neighbor that will send it first –As long as it can come before deadline
Performance Study: Schemes Single layer video without incentives (Single-Layer) Layered video without incentives (Layered) MDC with incentives (MDC-Incent) Layered video with incentives (Layered- Incent)
System Setup Peers –Ethernet peer: 1000 kbps; cable peer: 300 kbps; free-rider: 0 kbps –Fix ratio of Ethernet peers to cable peers: 3:7; change percentage of free-riders Video –Foreman video sequence (CIF, 30 frames/sec) –SVC video codec –20 layers, with each layer having a rate of 50 kbps Overlay –Each peer has 14 to 18 neighbors –Randomly replace worst neighbor every 30 seconds
Performance Metrics Useful rate received (R) –The bits that are useful for video decoding Discontinuity ratio (α) –The percentage of time that a video is undecodable and unplayable Average PSNR (Q) –Received video quality
Differentiated Service Peers with high upload contributions receive better video quality; Peers with low contributions receive relatively low but still acceptable video quality; Free-riders receive unacceptable video quality.
Free-Riding Received video quality does not degrade with free-riding
Conclusion A decentralized incentive mechanism for video streaming Performance studies show that the scheme can –Provide differentiated video quality commensurate with a peers contribution –Largely prevents free-riders