Blind Channel Estimation for SIMO-OFDM and STBC-OFDM Systems without Cyclic Prefix

• Main Authors: Chia-Hao Chen, 甄家灝
• Other Authors: Jung-Lang Yu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/14042374566019531814

碩士 === 輔仁大學 === 電子工程學系 === 94 === In practical orthogonal frequency-division multiplexing (OFDM) systems, cyclic prefix insertion and channel estimation are indispensable to achieve coherent demodulation. In previously, there have subspace (SS) and linear smoothing (LS) based blind channel estimation methods for single input multiple output(SIMO) OFDM systems over a time-dispersive channel are investigated. SS method has better performance than LS method, but LS method has lower computation than SS method. The two proposed methods do not require a cyclic prefix and thus leading to higher spectral efficiency. In this paper, we propose a performance enhance measure by block matrix scheme to improve SS and LS methods. Because we are to cope with smaller autocorrelation matrix than SS and LS, we obtain such that computational cost is reduced. Besides, the performance enhances measure by block matrix scheme convergence faster than conventions SS and LS. In this paper, we also utilize the Alamonti’s Space-time block code (STBC) scheme and subspace (SS) channel estimation on the OFDM system without cyclic prefix. The STBC-OFDM system without cyclic prefix has higher diversity order than SIMO-OFDM system without cyclic prefix. We also propose two performances enhance methods, forward-backward averaging technique and block matrix scheme method, to improve SS channel estimation. The forward-backward technique doubles the data information without increasing computation. The block matrix scheme method not only makes convergence faster also has lower complex of operation by using smaller autocorrelation matrix than traditions (SS) channel estimation. After we are enhance the performance in STBC-OFDM system without CP, the performance even better than STBC-CP-OFDM and STBC-ZP-OFDM system. We will see it clearly in computer simulations.