| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 92 === The quality of MPEG video multicasting may be greatly degraded due to packet losses caused by wireless error in 802.11 Wireless LAN. Forward Error Correction (FEC) is frequently used as an error control scheme; it provides redundant packets for receivers to recover from independent packet losses, but it may result in congestion collapse and degrade bandwidth utilization due to sending more redundant packets. In this thesis, a congestion-aware error control scheme is proposed. Through the improved algorithm to differentiate the causes of packet losses, the proposed scheme can be accurately aware of network condition and then determine number of redundant packets accordingly for both constant and variable rate transmission. Therefore, the proposed scheme is able to address the above problem artfully and consider overall transmission quality of network-layer. Furthermore, when network is non-congested, perceived quality of application-layer is also considered through supporting unequal scope protection for different type of MPEG video frames. A theoretical analysis of the proposed scheme is presented, and the experiment results show that when network is 1) congested, the proposed scheme would avoid worsening congested network and contrarily gets a balance of loss and recovery 2) non-congested, the proposed scheme supprts protection based on network-layer and application-layer to optimal overall video quality.
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