Research On Channel Estimation Algorithm In Mobile Environment

Due to the difficulty in predicting and controlling the wireless transmit environment, the channel character of wireless mobile communication is usually time varying. This character will hamper enhancement of mobile communication system's capacity and reliability. Therefore, a fast and accurate channel estimation is necessary. At first, the signal-to-noise ratio estimation algorithm in the mobile transmit environment is discussed in this paper, and then the channel estimation algorithm in CDMA system and the channel estimation algorithm in OFDM system are researched to find the effective and exact channel estimation algorithms in the wireless communication system.SNR estimation is one of the important parts of channel estimation. According to the model of SNR estimation in AWGN channel, some kinds of algorithms are reviewed. These methods are usually effective in the high SNR. In order to improve it, a SNR estimation algorithm based on EM is proposed. The analysis and comparison have been made between the proposed method and the existing ones. The simulation results show that the performance of the estimation algorithm based on EM is better than the previous method in the low SNR.In CDMA system, the broadband signal can present the frequency selective character when it transmits in multi-path channel, and it will result in the error of receiver. In order to improve the performance of receiver, the technology of RAKE diversity receiving is usually adopted, which needs the exact channel estimation information. In fact, the process of channel estimation of CDMA system is to obtain the optimal solution of minimum variance(MV) receiver. Therefore, the basic principle of MV receiver is introduced after the discussion of channel estimation model of CDMA system. Then, the singular value decomposition(SVD) algorithm is researched. The inversion of received data autocorrelation matrix is involved in the traditional SVD method, but the calculation process is complex and time-consumed, which make it difficult to implement in practice. In this paper, a modified SVD method based on matrix iteration method is proposed, and the simulation results show that the modified algorithm reduces the computational complexity with the same accuracy.In order to get the excellent receiving results, the accurate channel estimation information is needed during the process of coherent demodulation in the receiving end. After introducing the channel model of OFDM system briefly, a STC-OFDM channel estimation algorithm based on subspace is proposed in this paper. It not only contains the diversity gain of STC, but also involves the advantage of the anti multi-path of OFDM system. Meanwhile,...