Content-Aware Selective Retransmission Scheme in Heavy Loaded Wireless Networks

Abstract

although multimedia applications have very stringent bandwidth, delay and loss requirements. In mobile environment the limited bandwidth and the higher error rate arise as an obstacle of its popularity. In many cases retransmission-based error recovery can be an attractive solution to improve the quality of the video stream, because it requires minimal network bandwidth and processing cost. In this paper we propose a content-aware selective retransmission scheme which allows the retransmission of all packets when the risk of congestion is low, but as it rises the retransmission is disabled step-by-step, but not all at once, in order of packet importance. In this work the heterogenity of H.264 streams were utilized for the determination of packet importance. The advantage of this transmitter controlled procedure is that all the needed information is available at the source due to DCCP transport protocol and its congestion control algorithm. The effectiveness of the proposed method was examined in Ns2 network simulator. IntroductionReal-time multimedia applications are gaining prominence on the Internet. These applications are not only used in reliable wired networks but also in wireless environment where the obstacles of the expansion are the higher bit error ratio of the radio link and the limited bandwidth of the mobile links. The loss of packets in a video frames leads not only to reduce the quality of video but also results in the propagation of distortion to successive frames, because interframe-video compression algorithms such as MPEG exploit temporal correlation between frames to achieve higher compression. To minimize the end-to-end packet loss ratio the packet loss should be either prevented or subsequently handled.

SeRViSO

“…I frames are always recovered, and if the loss rate is less than 40 and 20%, P and B frames are respectively recovered too. A retransmission scheme for wireless networks, based on congestion risk and frame importance is detailed in [4]. In order to avoid overloading the network, less important frames are not retransmitted.…”