Least-Square Channel Estimation Technique Assisted from Postfixed a PN Sequence for Wireless OFDM Communication System

• Main Authors: Te-Yun Su, 蘇德昀
• Other Authors: Jia-Chin Lin
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/r4fj95

碩士 === 國立中央大學 === 通訊工程研究所 === 96 === Recently, OFDM (Orthogonal Frequency Division Multiplexing) techniques have received a great deal of interest due to its high transmission rate capability with high bandwidth efficiency, and its robustness against several types of channel, such as multipath fading, impulse noise, and so forth. There are still some problems in OFDM systems, such as inter-symbol interference (ISI), inter-carrier interference (ICI), and peak-to-average power ratio (PAPR). These problems can reduce the performance of OFDM system. In the cause of improving these problems, channel estimation in coherent OFDM system is necessary and essential. To avoid ISI and ICI, adding cyclic prefix (CP) is widely used. Here proposed a modify scheme by using a pseudo noise (PN) sequence instead of a CP. A PN sequence is inserted in the postfix of each OFDM symbol to estimate the channel impulse response (CIR). In order to enhance system performance, a least-square (LS) channel estimation technique is proposed in this thesis. The proposed algorithm includes least-square technique with decision-directed data-assistance and least-square estimator. The proposed techniques can achieve excellent estimation performance, and its good ability of estimating and tracking the channel variations. It is suitable in presence of large Doppler spreads. The simulations are given to illustrate the better performance of the proposed channel estimation techniques.