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The broadcast and multicast services (BCMCS) protocol is designed for real-time applications such as MPEG-4 video streaming, which requires successive frames to arrive within a specific time interval. We analyze the execution time of Reed-Solomon (RS) decoding, which is the medium access control (MAC)-layer forward error-correction (FEC) scheme used in CDMA2000 1xEV-DO BCMCS, under various air channel conditions. The results show that the timing constraints of MPEG-4 cannot always be met by RS decoding when the packet loss rate (PLR) is high, due to the limited processing power of current hardware. We therefore propose three error control schemes: First, we have our static scheme, which bypasses RS decoding at the mobile node to satisfy the MPEG-4 timing constraint when the PLR exceeds a given level. Second, we have the dynamic scheme, which corrects as many errors as possible within the timing constraint, instead of giving up altogether when the PLR is high; this improves quality. Third, we have the video-aware dynamic scheme, which fixes errors in a similar way to the dynamic scheme but in a priority-driven manner, yielding a further increment in video quality at mobile terminals. Extensive simulation results show the effectiveness of our schemes compared with the original FEC scheme.
Date of Publication: Jan. 2009