Fast varying channel estimation in downlink LTE systems

This paper tackles the problem of fast varying channel estimation in LTE systems. Particular attention is given to downlink transmission where OFDMA is used as the multiple access technique for the air interface. In OFDMA, fast variation of the channel results in significant inter-carrier interference (ICI) which cannot be mitigated with conventional estimation and equalization techniques. In this paper, we investigate the polynomial modeling of rapidly time varying channels. Specifically, we propose a time-domain estimation method and a low-complexity frequency-domain estimation method both of which leverage the special structure of the approximated channel matrix to compute ICI channel components. It is shown by simulations that these two methods provide a considerable performance improvement over conventional methods by means of improved ICI mitigation. We further study the robustness of these two methods to both partial and full channel profile knowledge. It has been shown that the frequency-domain approach has much lower complexity and better robustness compared to the time domain approach.