Angle-Domain Doppler Pre-Compensation for High-Mobility OFDM Uplink with a Massive ULA

TL;DR

This paper introduces a Doppler pre-compensation method for high-mobility OFDM uplink using a large ULA, significantly reducing channel variation and enabling standard channel estimation techniques.

Contribution

The paper proposes a novel DFO pre-compensation scheme at the transmitter with a large ULA to mitigate Doppler effects in high-mobility OFDM uplink channels.

Findings

Doppler spread is reduced with increasing transmit antennas.

Channel variation can be suppressed effectively.

Standard channel estimation remains viable after compensation.

Abstract

In this paper, we propose a Doppler pre-compensation scheme for high-mobility orthogonal frequency division multiplexing (OFDM) uplink, where a high-speed terminal transmits signals to the base station (BS). Considering that the time-varying multipath channel consists of multiple Doppler frequency offsets (DFOs) with different angle of departures (AoDs), we propose to perform DFO pre-compensation at the transmitter with a large-scale uniform linear array (ULA). The transmitted signal passes through a beamforming network with high-spatial resolution to produce multiple parallel branches. Each branch transmits signal towards one direction thus it is affected by one dominant DFO when passing over the time-varying channel. Therefore, we can compensate the DFO for each branch at the transmitter previously. Theoretical analysis for the Doppler spread of the equivalent uplink channel is also conducted. It is found that when the number of transmit antennas is sufficiently large, the time-variation of channel can be efficiently suppressed. Therefore, the performance will not degrade significantly if applying the conventional time-invariant channel estimation and equalization methods at the receiver. Simulation results are provided to verify the proposed scheme.