| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 93 === In recent years, high-speed wirelesses LANs are widely deployed in airports, stations, hotels and street corners. Support multimedia applications over wireless LANs will becomes an important popular in the future. Service differentiation and throughput enhancement are major concerns in multimedia wireless LANs. In this thesis, we extend IEEE 802.11e Distributed Coordinated Function (DCF) to further provide service differentiation and improve throughput for live video and audio over error-prone wireless LAN. We propose an adaptive two-stage backoff counter to reduce the overheads in blocking backoff counter. Furthermore, we explore the proactive frame drop policy to eliminate unnecessary retransmissions of video and audio frames under bad channel conditions. To investigate the performance of the proposed schemes, we develop an analytic model for two-stage backoff counter based on two-dimensional markov chain. Simultaneously, we run intensive computer simulation using ns-2. The results demonstrate the superior of proposed schemes in terms of system throughput and service differentiation.
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