tailieunhanh - Báo cáo hóa học: " Research Article Robust Blind Frequency and Transition Time Estimation for Frequency Hopping Systems"

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 Robust Blind Frequency and Transition Time Estimation for Frequency Hopping Systems | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2010 Article ID 172703 13 pages doi 2010 172703 Research Article Robust Blind Frequency and Transition Time Estimation for Frequency Hopping Systems Kuo-Ching Fu and Yung-Fang Chen Department of Communication Engineering National Central University Jung-da Road Jung-li City Taoyuan 32001 Taiwan Correspondence should be addressed to Yung-Fang Chen yfchen@ Received 27 April 2010 Revised 24 September 2010 Accepted 5 November 2010 Academic Editor Kutluyil Dogancay Copyright 2010 . Fu and . Chen. 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. In frequency hopping spread spectrum FHSS systems two major problems are timing synchronization and frequency estimation. A blind estimation scheme is presented for estimating frequency and transition time without using reference signals. The scheme is robust in the sense that it can avoid the unbalanced sampling block problem that occurs in existing maximum likelihood-based schemes which causes large errors in one of the estimates of frequency. The proposed scheme has a lower computational cost than the maximum likelihood-based greedy search method. The estimated parameters are also used for the subsequent time and frequency tracking. The simulation results demonstrate the efficacy of the proposed approach. 1. Introduction Frequency hopping spread spectrum FHSS techniques are widely used in military communications for combating narrowband interference and for security purposes. The two parameters that are required for the estimation in FHSS are transition time and hopping frequency. Regular synchronization is divided into two stages coarse acquisition and fine tracking 1 . Reference signals may be used to estimate the parameters 2-6 but they may not