Channel Modeling and Estimation in High-Speed Mobile Environment

With the development of high-speed railway, the future wireless communication system is facing the high-speed mobile environment, where rapid and significant variations will emerge in the instantaneous wireless channel conditions. The main challenge on the channel estimation is that plenty of pilots should be inserted to track the fast- varying channel. In this paper, we propose a method to estimate the fast-varying channel with the aid of Basis Expansion Model (BEM) and uplink Sounding Reference Signal (SRS). BEM is used to model the fast-varying channel with the combination of a finite number of basis functions, and the combination coefficients are slow-varying. Therefore, the sparse SRS can be used to estimate the channel, which will reduce the pilot number compared to the estimation with demodulation reference signals. Simulation results show that our proposed method provides better performance than the traditional one in the fast- varying channel, and can accommodate to different Doppler frequency shift with changing the BEM order.

I. Introduction

Broadband mobile communication is changing our life, and the basic requirement is transmitting information more rapidly and accurately. It is predicted that hundreds of millions of devices will connect to the network by 2020 [1]. The devices may be in high-speed environment, and thus the channel exhibits fast time-variance. It poses great challenges on the channel estimation and high-rate data transmission. To meet the data rate requirement in high-speed mobile environment, the Long Time Evolution (LTE) has been suggested as one of the wireless transmission standards in high-speed mobile environment [2].