tailieunhanh - Báo cáo hóa học: " Improved Max-Log-MAP Turbo Decoding by Maximization of Mutual Information Transfer"

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: Improved Max-Log-MAP Turbo Decoding by Maximization of Mutual Information Transfer | EURASIP Journal on Applied Signal Processing 2005 6 820-827 2005 Hindawi Publishing Corporation Improved Max-Log-MAP Turbo Decoding by Maximization of Mutual Information Transfer Holger Claussen Signals Systems Group University of Edinburgh Edinburgh EH9 3JL UK Email claussen@ Hamid Reza Karimi Bell Laboratories Lucent Technologies Swindon SN5 7DJ UK Email hkarimi@ Bernard Mulgrew Signals Systems Group University of Edinburgh Edinburgh EH9 3JL UK Email Received 1 October 2003 Revised 7 May 2004 The demand for low-cost and low-power decoder chips has resulted in renewed interest in low-complexity decoding algorithms. In this paper a novel theoretical framework for improving the performance of turbo decoding schemes that use the max-logMAP algorithm is proposed. This framework is based on the concept of maximizing the transfer of mutual information between the component decoders. The improvements in performance can be achieved by using optimized iteration-dependent correction weights to scale the a priori information at the input of each component decoder. A method for the offline computation of the correction weights is derived. It is shown that a performance which approaches that of a turbo decoder using the optimum MAP algorithm can be achieved while maintaining the advantages of low complexity and insensitivity to input scaling inherent in the max-log-MAP algorithm. The resulting improvements in convergence of the turbo decoding process and the expedited transfer of mutual information between the component decoders are illustrated via extrinsic information transfer EXIT charts. Keywords and phrases turbo decoding max-log-MAP correction weights EXIT charts mutual information. 1. INTRODUCTION Since the discovery of turbo codes 1 there has been renewed interest in the field of coding theory with the aim of approaching the Shannon limit. Furthermore with the proliferation of wireless mobile devices