tailieunhanh - Báo cáo hóa học: " H.264 Layered Coded Video over Wireless Networks: Channel Coding and Modulation Constraints"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Layered Coded Video over Wireless Networks: Channel Coding and Modulation Constraints | Hindawi Publishing Corporation EURASIP Journal on Applied Signal Processing Volume 2006 Article ID 85870 Pages 1-8 DOI ASP 2006 85870 Layered Coded Video over Wireless Networks Channel Coding and Modulation Constraints M. M. Ghandi B. Barmada E. V. Jones and M. Ghanbari Department of Electronic Systems Engineering University of Essex Wivenhoe Park Colchester CO4 3SQ UK Received 13 July 2005 Revised 16 December 2005 Accepted 18 February 2006 This paper considers the prioritised transmission of layered coded video over wireless channels. For appropriate protection ofvideo data methods such as prioritised forward error correction coding FEC or hierarchical quadrature amplitude modulation HQAM can be employed but each imposes system constraints. FEC provides good protection but at the price of a high overhead and complexity. HQAM is less complex and does not introduce any overhead but permits only fixed data ratios between the priority layers. Such constraints are analysed and practical solutions are proposed for layered transmission of data-partitioned and SNR-scalable coded video where combinations of HQAM and FEC are used to exploit the advantages of both coding methods. Simulation results show that the flexibility of SNR scalability and absence of picture drift imply that SNR scalability as modelled is superior to data partitioning in such applications. Copyright 2006 Hindawi Publishing Corporation. All rights reserved. 1. INTRODUCTION Within a given bandwidth the capacity of a communication channel is determined by its signal-to-noise ratio SNR 1 which can vary widely. Ideally a service such as video over wireless networks should adaptively change its information rate according to the available channel capacity. For example low SNRs can only support a low source rate and require a high protection of contents and conversely for high SNRs a high source rate can be transmitted with less protection 2 . However this ideal adaptation is not feasible