Single-Tap Precoders and Decoders for Multi-User MIMO FBMC-OQAM under Strong Channel Frequency Selectivity

TL;DR

This paper proposes a low-complexity single-tap precoding and decoding scheme for multi-user MIMO FBMC-OQAM systems that effectively handles strong channel frequency selectivity by optimizing MSE under ZF and MMSE criteria.

Contribution

It introduces a novel single-tap per-subcarrier precoding/decoding method that accounts for channel frequency selectivity without assuming flatness, improving performance in MU MIMO FBMC systems.

Findings

Optimized precoders and decoders improve MSE performance.

Extra BS antennas help mitigate channel frequency selectivity.

Simulation confirms effectiveness of the proposed approach.

Abstract

The design of linear precoders or decoders for multiuser (MU) multiple-input multiple-output (MIMO) filterbank multicarrier (FBMC) modulations in the case of strong channel frequency selectivity is presented. The users and the base station (BS) communicate using space division multiple access (SDMA). The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the base station (BS) in the downlink/uplink. As opposed to classical approaches that assume flat channel frequency selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by channel frequency selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong channel selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing (ZF) or minimum mean squared error (MMSE). Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the channel frequency selectivity.