The Performance Evaluation of Spatial Multiplexing Transmission Applied to MIMO WiMAX System with Frequency Offset

• Main Authors: Ping-Feng Hsueh, 薛秉峰
• Other Authors: Shiann-Shiun Jeng
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/13653104190685574478

碩士 === 國立東華大學 === 電機工程學系 === 97 === The next generation wireless communication system, WiMAX system, is an OFDM-based system. The antenna technique, MIMO, is also popularly applied to OFDM systems. However, the mobility of the users results in Doppler effect, and frequency shifts are generated. Because of Doppler frequency shifts, the bit error rate of OFDM-based systems becomes higher at the receiver. Frequency shifts cause the incorrect estimation of the DOA and decay of the antenna gain. To solve this problem, WirelessMAN-OFDM PHY from IEEE 802.16e standard is used as system stage. In mobile channel and MIMO system, the channel matrix will be obtained by Spatial signature and Spatial multiplexing. We use the uniform-distributed allocation for pilot subcarriers in the multi-antenna transmitter, and then Doppler frequency shifts can be estimated. In addition to prove the full rank of channel matrix using the subspace smoothing, we also utilize the high resolution DOA estimation algorithm, TLS-ESPRIT, to estimate the DOAs and the autocorrelation matrix to estimate the channel matrix. Then we can estimate the frequency shifts by the proposed algorithm. Finally we compensate for the frequency shift, and the performance of the system becomes better.