Location-Aware ICI Reduction in MIMO-OFDM Downlinks for High-Speed Railway Communication Systems

In the long-term evolution for railway, orthogonal frequency-division multiplexing (OFDM) is adopted to provide seamless connection to existing ground cellular network and support high mobility communication in future 5G. However, due to the high velocity of high-speed railway (HSR), the channel is fast time-varying and serious intercarrier interference (ICI) is introduced, meaning that low-complexity and real-time ICI reduction methods are needed, which has not been well discussed in previous works. In this paper, we focus on the HSR downlinks with distributed transmit antennas and develop two corresponding ICI reduction methods for additive white Gaussian noise (AWGN) and Rician channels, respectively. With the information of relative locations and velocities between corresponding antenna pairs, we show that the ICI matrices in AWGN and Rician channels can be mathematically calculated, and they are approximately unitary. With these results, we propose two corresponding low-complexity ICI reduction methods to avoid matrix inversion and suit fast time-varying nature. Simulation results show our proposed ICI mitigation method can achieve similar service quantity with that obtained on the case without ICI when velocity is about 300 km/h.