Low-Complexity Equalization of 3GPP High-Speed Train Channel.

Traditional low-complexity channel equalization techniques for the orthogonal frequency-division multiplexing (OFDM) in the uplink are applicable only to the channels with small Doppler spreads such as a highway channel. The highspeed train (HST) channel defined by the 3GPP, however, has an extremely higher Doppler shift in each multipath component. In this work, we develop a received signal model suitable for the OFDM transmitted signal and the HST channels in the uplink, and propose a low-complexity equalization technique. The key idea is to pre-process the time-domain samples of the received signal by derotating the phases of samples relative to the line-ofsight (LoS) path and then to use a low-complexity equalizer for small Doppler spreads. Numerical results are provided.