Cross-Layer Design for Video Transmission over Wireless Rician Slow-Fading Channels Using an Adaptive Multiresolution Mo
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Research Article Cross-Layer Design for Video Transmission over Wireless Rician Slow-Fading Channels Using an Adaptive Multiresolution Modulation and Coding Scheme Yong Pei1 and James W. Modestino2 1 Computer 2 Electrical
Science and Engineering Department, Wright State University, Dayton, OH 45435, USA and Computer Engineering Department, University of Miami, Coral Gables, FL 33124, USA
Received 22 August 2006; Accepted 13 April 2007 Recommended by Alex Kot We describe a multilayered video transport scheme for wireless channels capable of adapting to channel conditions in order to maximize end-to-end quality of service (QoS). This scheme combines a scalable H.263+ video source coder with unequal error protection (UEP) across layers. The UEP is achieved by employing different channel codes together with a multiresolution modulation approach to transport the different priority layers. Adaptivity to channel conditions is provided through a joint source-channel coding (JSCC) approach which attempts to jointly optimize the source and channel coding rates together with the modulation parameters to obtain the maximum achievable end-to-end QoS for the prevailing channel conditions. In this work, we model the wireless links as slow-fading Rician channel where the channel conditions can be described in terms of the channel signal-to-noise 2 ratio (SNR) and the ratio of specular-to-diffuse energy ζ . The multiresolution modulation/coding scheme consists of binary rate-compatible punctured convolutional (RCPC) codes used together with nonuniform phase-shift keyed (PSK) signaling constellations. Results indicate that this adaptive JSCC scheme employing scalable video encoding together with a multiresolution modulation/coding approach leads to significant improvements in delivered video quality for specified channel conditions. In particular, the approach results in considerably improved graceful degradation properties for decreasing channel SNR. Copyright © 2007 Y. Pei and J. W. Modestino. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
The wireless channel varies over time and space and has short-term (or small-scale) memory due to multipath. These variations are caused either due to motion of the wireless device, or due to changes in the surrounding physical environment, and lead to detector errors. In addition to small-scale channel variations, there is also spatio-temporal variations on a much greater time scale [1]. Large-scale channel variation means that the average channel state condition depends on user locations and interference levels. As a result, it is wellrecognized now that cross-layer design is critically needed to insure continuity, robustness, and good end-to-end performance in multimedia wireless networks in the face of these random variations [2–8]. Most of the current explicit cross-layer design approaches have been limited
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