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: Research Article Separate Turbo Code and Single Turbo Code Adaptive OFDM Transmissions | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2009 Article ID 609386 7 pages doi 2009 609386 Research Article Separate Turbo Code and Single Turbo Code Adaptive OFDM Transmissions Lei Ye1 and Alister Burr2 1Department of Communication Engineering University of Chongqing Chongqing 400044 China 2Department of Electronics University of York Heslington YorkYO10 5DD UK Correspondence should be addressed to Lei Ye yelei0815@ Received 30 June 2008 Revised 22 December 2008 Accepted 18 January 2009 Recommended by Yan Zhang This paper discusses the application of adaptive modulation and adaptive rate turbo coding to orthogonal frequency-division multiplexing OFDM to increase throughput on the time and frequency selective channel. The adaptive turbo code scheme is based on a subband adaptive method and compares two adaptive systems a conventional approach where a separate turbo code is used for each subband and a single turbo code adaptive system which uses a single turbo code over all subbands. Five modulation schemes BPSK QPSK 8AMPM 16QAM and 64QAM are employed and turbo code rates considered are 1 2 and 1 3. The performances of both systems with high 10 2 and low 104 BER targets are compared. Simulation results for throughput and BER show that the single turbo code adaptive system provides a significant improvement. Copyright 2009 L. Ye and A. Burr. 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. 1. Introduction When transmitted in time dispersive channels the bit error rate BER achieved on different orthogonal frequencydivision multiplexing OFDM subcarriers depends on the frequency domain channel transfer function. The bit errors are normally concentrated in a few severely faded subcarriers in conventional nonadaptive OFDM systems. In the rest of
