Broadband SISO / MIMO-OFDM System Channel Parameter Estimation

Multiple Input Multiple Output(MIMO) technology and Orthogonal Frequency Division Multiplexing(OFDM) technology has been adopted as one of critical techniques for the current or existing wireless communication standards, and is also an important technical foundation of the next generation wireless communication standards. Channel estimation is the important part of MIMO-OFDM system, it can provide a reliable channel state information (CSI) for transmit beamforming and receive MIMO detection. So, the accuracy of the channel estimation has an important impact on the performance of the MIMO-OFDM system. This thesis mainly includes three aspects as follows:1) In order to deal with the problem of energy leakage of the channel impulse response with non-integer sampling interval, a novel time-domain discriminant analysis channel estimation(TD-DACE) scheme is proposed in this paper. According to the channel model specified by LTE standard, and based on the frame structure of LTE downlink system, a comparative study has also been conducted between the TD-DACE and several existing channel estimators.The simulation results show that the bit error rate (BER) performance of the proposed TD-DACE is better than the least square. Meanwhile, compared with linear minimum mean square error algorithm, the BER performance of the proposed scheme is slightly worsen, but it has a lower complexity.2) In order to track time-varying channel accurately under the high-speed mobile environment, four basis expansion models(BEM) have been studied, including complex exponential BEM、 discrete prolate spheroidal BEM、polynomial and discrete Karhunen-Loeve BEM. Based on the four BEM channel models, three criterions of estimating the weighted parameters of basis have been studied:LS、MMSE, and best linear unbiased, combining four basis expansion models with three criterions yields a total of12fast time-varying channel estimators. The simulation results of those time-varying channel estimators are given.3) In the OFDM system with IQ imbalances, this paper proposed a time-domain least square (TD-LS) algorithm to estimate channel and IQ-imbalance parameters. To further exploit the sparsity of the wireless channel, iterative shrinkage (IS) and parallel coordinate descent (PCD) are combined with the proposed TD-LS to form a new joint channel estimator TD-LS-IS-PCD. From simulation, in terms of bit error rate (BER), the proposed TD-LS and TD-LS-IS-PCD algorithms perform much better than the traditional frequency-domain least square (FD-LS) when the same least square equalizer is adopted. Furthermore, the BER performance of TD-LS-IS-PCD approaches that of the ideal channel estimator.