| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 102 === Multicast is an effective mechanism to save network bandwidth while transmitting real-time video streams in wireless networks. However, it lacks of a mechanism of error control. Packet errors happen easily because wireless channels are error-prone; this may bring a critical deterioration of the video quality. Besides, the end-to-end retransmission can not meet the strict delay constraint of a real-time video stream. In this thesis, we propose a multicast retransmission mechanism to improve the quality of real-time video streams over WiMAX network. In this mechanism, we design a MAC-layer ARQ scheme to retransmit the erroneous or lost ARQ blocks from BS, and consider three conditions, which are the bandwidth cost at retransmitting in multicast connection, the packet transmission delay and the acceptable delay constraint of MSs.
We perform NS-3 simulation to demonstrate our proposed mechanism. The simulation results show that the mechanism can effectively reconstruct the quality of a real-time video stream at MSs. Furthermore, the cost of bandwidth using at retransmitting can be significantly reduced.
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