Mimo-ofdm Channel Estimation Algorithm

OFDM has the characteristic of high-speed data transmission, high spectrum efficiency, selective fading with resisted frequency and multipath fading, while multiple input multiple output technology can improve communication systems capacity in case of not increasing system bandwidth. MIMO-OFDM is the key technology of next generation (4G) wireless communication with the advantages of both technologies, it can obtain three diversities of time, frequency and spatial at the same time. Channel estimation plays key roles in MIMO-OFDM system, it is essential to study the channel estimation method of MIMO-OFDM system.First, the article describes the basic principle and structure of OFDM systems, MIMO systems, MIMO-OFDM system, also, the spatial characteristic and fading feature of wireless channel, also, studies the channel estimation algorithm based on pilot symbols as for the least squares method and the singular value decomposition method concretely. Also, the article studies the commonly used interpolation algorithm such as linear interpolation, Gauss interpolation and Lagrange interpolation, getting the comparison curve of performance through computer simulation.Secondly, Focusing on MIMO-OFDM system under frequency selective fading channel, based on the model of Rayleigh fading channel and the autocorrelation of m sequence, the paper proposes a MIMO-OFDM least squares algorithm using m sequence as comb pilot, which avoids pseudo inverse of large matrix so as to reduce the computational complexity and improves the calculation performance of channel estimation.Finally, the paper introduces the MIMO-OFDM system with superimposed pilot, adopting the orthogonal multi-phase sequence as superimposed pilot, using the autocorrelation of pilot symbols, also the cross correlation of pilot and received signal, we propose a channel estimation algorithm based on selective superimposed pilot channel. Theoretical analysis and computer simulation show that the method has good performance in fast fading environment.