New Approach of Implementing STBC Technique for MIMO system and MIMO-OFDM Channel Estimation

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Duaa Waleed
Rawya Deriah
Walaa Hammoudeh
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Abstract The fundamental detection problem in fading channels involves the correct estimation of transmitted symbols at the receiver in the presence of Additive White Gaussian Noise (AWGN). This project adopts a different view to estimator performance, by evaluating the accuracy of CSI. The superior performance promised by the MIMO-OFDM and OFDM technologies rely on the availability of accurate Channel State Information (CSI) at the receiver by transmitting pilots along with data symbols.Pilot symbol assisted channel estimation is especially attractive for wireless links, where the channel is time-varying.In this project we investigate and compare various efficient pilot based channel estimation schemes; Least Square Error (LSE) and Minimum Mean Square Error (MMSE) channel estimators has been employed for OFDM system. Then conclude that LS algorithm gives less complexity but MMSE algorithm provides comparatively better results. Also in this project, performance analysis of channel estimation for Multiple-Input Multiple-Output (MIMO) communication system combined with the Orthogonal Frequency Division Multiplexing (OFDM) through different algorithms for estimating channel using different modulation scheme are investigated. The estimation implemented here of channel at pilot frequencies is based on Least Square, Weiner Filter Estimator and Orthogonal Training Sequence Estimator algorithms. We have compared the performances of channel estimation algorithm by measuring bit error rate vs. SNR. Weiner Filter Estimator has been shown to perform much better than LS but is more complex than other channel estimation algorithm. Also compared the actual and the estimated channel in Orthogonal Training Sequence channel estimation and notice that errors in the CSI estimation are as a result of AWGN in the received symbols.Finally, new methods for implementing QO-STBC and DHSTBC over OFDM for four, eight and sixteen transmitter antennas are presented. The QO-STBC and DHSTBC over OFDM scheme eliminates the interference from the detection matrix and improved the performance by increasing the diversity order in the transmitter side. The proposed code promote the diversity gain when compared with the real STBC scheme and DHSTBC gives the best performance; both techniques  reduce the effect of Inter Symbol Interference (ISI) due to the existence of OFDM.