The Algorithm Research Of Channel Estimation And The Analysis Of Channel Capacity In MIMO-OFDM Systems

Combining space diversity, frequency diversity and time diversity together efficiently, the Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) technology can improve the wireless communication channel capacity and transfer rates greatly, and can resist fading effectively, restrain the interference and noise, has drawn people's attention and been widely considered the core of next generation wireless mobile communication.At the beginning, this thesis describes the research background and OFDM, MIMO technology development status. The basic characters of radio fading channels are elaborated by introducing large-scale fading, shadow fading, small-scale fading, and multipath fading. And then this thesis focused on the Wide Sense Stationary Uncorrelated Scatter (WSSUS),Raylaiy, Ricean, and MIMO-OFDM systems. Based on the study above, the research situation of pilot symbol-assisted in channel estimate and channel capacity is analyzed, and also the research problems are given in this article.The least squares (LS) method based on frequency domain has a lower complexity, but has the bad error performance. The fourth chapter of this thesis has designed a new pilot structure embarked from arbitrary receiving antenna under the rule of the mean square error(MSE). In the new pilot structure, the sequences of pilot phase are mutually orthogonal and evenly distributed, the theoretical derivation proved that the proposed structure has the minimum mean square error; the element of the proposed pilot matrix in this paper is real number or purely imaginary number so as to reduce the compute complexity effectively. The simulation results showed that the proposed algorithm is better than the traditional method of least squares in mean square error, which is more obvious with the increase of signal to noise ratio (SNR); The proposed algorithm has the very low system error rate (SER) than the traditional least-square, and has much better performances with the increasing number of sub-carriers in the case of high SNR.More antennas at the transmitter or at the receiver can offer larger channel capacity in MIMO communication systems. However, some defects are remained in studying the change of channel capacity to the multi-antenna system currently, such as high computational complexity, limited to a specific system, and so on. The fifth chapter of this thesis embarked from antenna selection algorithms, the change of channel capacity to the multi-antenna system are demonstrated in details. Theoretical derivation proved that the increasing(decreasing) number of antennas can increase (decrease) the channel capacity of system. Simulation results of MATLAB showed that when the signal to noise ratio is certain, the greater the number of antennas, the larger channel capacity of system and the faster the increasing rate of the system channel capacity; Further more, both the average channel capacity of system reflected by the probability distribution function (PDF) and the increasing rate of the channel capacity of system reflected by cumulative distribution function(CDF) will increase with the increasing the number of antennas more obviously.