spaper15 - IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, NO. 6,...

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Unformatted text preview: IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, NO. 6, DECEMBER 2005 1123 A Comparison of Heterogeneous Video Multicast Schemes: Layered Encoding or Stream Replication Taehyun Kim and Mostafa H. Ammar , Fellow, IEEE Abstract— The heterogeneity of the Internet’s transmission resources and end system capability makes it difficult to agree on acceptable traffic characteristics among the multiple receivers of a multicast video stream. Three basic approaches have been proposed to deal with this problem: 1) multicasting the replicated video streams at different rates; 2) multicasting the video encoded in cumulative layers; and 3) multicasting the video encoded in noncumulative layers. Even though there is a common belief that the layering approach is better than the replicated stream approach, there have been no studies that compare these schemes. This paper is devoted to such a systematic comparison. Our starting point is an observation (substantiated by results in the literature) that a bandwidth overhead is incurred by encoding a video stream in layers. We argue that a fair comparison of these schemes needs to take into account this overhead, as well as the specifics of the encoding used in each scheme, protocol complexity, and the topological placement of the video source and the receivers relative to each other. Our results show that the believed superiority of layered multicast transmission relative to replicated stream multicasting is not as clear cut as is widely believed and that there are indeed scenarios where replicated stream multicasting is the preferred approach. Index Terms— Multimedia communication, video multicasting, scalable video streaming. I. INTRODUCTION A SYSTEM for multicasting video over the Internet has to deal with the question of heterogeneity of the receivers capability and/or requirements. Typically, receivers and the paths leading to them will have different reception capacity. We are, therefore, faced with the problem of trying to accommodate this difference among the receivers: low capacity receivers are heavily loaded and suffer from network congestion, but high capacity receivers are lightly loaded and under-utilized. This problem has been addressed by many researchers (e.g., [2]–[4], [13], [18], and [19]). Note that the problem of multicasting video in a heterogeneous environment is important regardless of whether native network layer multicast or application layer multicast [5] are used. There are three basic approaches. • The replicated stream approach [4], [13] In this approach, the video source multicasts several streams with identical content but at different data rates. Manuscript received December 3, 2001; revised July 28, 2004. This work was supported by the AFOSR MURI Grant F49620-00-1-0327, the National Science Foundation Grant ANI-9973115, and by a research grant from Sprint....
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spaper15 - IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, NO. 6,...

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