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The provision of video communications over wireless links is a challenging task due to the poor performance of video compression algorithms in time-varying error-prone environments. The paper presents a performance enhancement method for real-time video communications by employing link adaptation in enhanced general packet radio service (E-GPRS) cellular networks. A novel link adaptation algorithm, which is based on physical layer measurable quantities, including block error rate (BLER), received signal strength (RSS) and the gradient of RSS, is proposed and analysed. The effects of a link adaptation scheme at video frame level on improving video quality with variable source rate by varying the channel-coding scheme for a fixed channel allocation is studied. The algorithm is tested for MPEG-4 coded video transmissions over simulated channel conditions based on the GSM mobile radio multipath propagation models (see 3GPP TS 05.05, 1999). The performance obtained using the proposed method is compared to a non-adaptive case and to the ideal adaptive case, where the choice of channel coding scheme is made based on the carrier-to-interference ratio (CIR) of the transmission channel.
Date of Conference: 8-10 May 2002