The Study Of Joint Channel Estimation For OFDM System Based On Pilot

As the developing of wireless communications technology, to achieve seamless high-speed, high-quality mobile multimedia and data transmission became its development goals. Orthogonal Frequency Division Multiplexing (OFDM) is a parallel multi-carrier transmission scheme, which uses a number of mutually orthogonal subcarriers to transmit information with high spectrum efficiency and good anti-multipath performance. This technology can be used to transfer high rate and multi-media data, and is considered as one of the core technology for the fourth generation mobile communications.Channel Estimation is one of the key technologies of OFDM systems. The channel estimation techniques in general can be divided into three categories: the pilot-based channel estimation, channel estimation based on the decision feedback and blind channel estimation. The pilot-based one estimates the whole channel response through the pilot sub-channel response, which able to track channel changes. This method is suitable for practical application for its good performance over uncomplex situation.In this paper, we study the pilot-based channel estimation. First of all, we briefly introduced the basic principles of OFDM systems, and the mathematical model of wireless channel is given in this part. Then we focus on the traditional pilot-based channel estimation method, and introduced the comb-like and the block-like pilot channel estimation algorithm in principle and performance. For the block pilot method, we discuss the least-squares estimation algorithm (LS), minimum mean square error estimation algorithm (MMSE) and the estimation algorithm by singular value decomposition (SVD). For the comb pilot method, we analyse the least squares estimation in frequency domain of the pilot sub-carrier, and use some traditional interpolation ways, such as linear interpolation, Gauss interpolation, Sinc interpolation and zero-interpolation in transform domain, to get the full channel frequency response. And then we carried out the performance comparison by computer simulation and analysis.Finally, by the combination of computer simulation of these algorithms, we give a comprehensive analysis and comparison for the above method, and proposes a least square (LS) method of joint channel estimation. This method estimates the channel information more accurate by combining the transmitted data and pilot. So the new method improves the system performance. Simulation results show that our method better than the classical method.