Research On Channel Estimation Algorithms Of OFDM Systems In Time-varying Channel

Wireless communication channel takes on randomness and complexity. When the signaltravels through the time-varying wireless channel, signal amplitude, phase and frequency willcause distortion, which requires compensation by obtaining accurate channel stateinformation. Therefore, time-varying channel estimation becomes particularly important.In this paper, the research direction is estimating the time-varying channel in OFDMsystems. Firstly, basic principles of wireless communication channel model and OFDM areintroduced. Then existing channel estimation algorithm of OFDM system is illustrated indetails.On this basis, LMMSE estimation algorithm of joint channel is proposed in reference tothe combination of estimated channel value by comb pilot and AR prediction model. LMMSEestimation algorithm is linked up with the estimated values of comb pilot which can tracktime-variation in the channel wonderfully well. Meanwhile, it incorporates the estimatedchannel values of AR prediction model to maintain better perdition effect than that inestimation algorithm of comb pilot. Simulation results indicate that, comparing with methodswith only AR prediction model, LMMSE estimation algorithm and LMMSE-AR estimationalgorithm of joint channel reduce the mean square error of the channel estimation andimprove the BER performance.LMMSE estimation algorithm demands a priori knowledge of the channel; still, itoperates complex calculation. In order to enhancing practicality of joint channel estimationmethod, LS estimation algorithm of joint channel is put forward. Simulation results show that,as opposed to methods with only AR prediction model, LS estimation algorithm and LS-ARestimation algorithm of joint channel greatly improve the estimation performance andeffectively reduce the impact of noise on the accuracy of channel estimation.