Robust THP Transceiver Designs for Multiuser MIMO Downlink with Imperfect CSIT

TL;DR

This paper develops robust joint transceiver designs for multiuser MIMO downlink systems using Tomlinson-Harashima precoding, addressing CSIT imperfections with stochastic and norm-bounded error models, and proposing iterative algorithms for optimization.

Contribution

It introduces robust transceiver design algorithms for multiuser MIMO downlink with imperfect CSIT, considering both stochastic and worst-case error models, and extends to per-antenna power constraints.

Findings

Proposed iterative algorithms effectively optimize transceivers under CSIT errors.

Robust designs outperform non-robust counterparts in imperfect CSIT scenarios.

Algorithms involve semi-definite programming for efficient solutions.

Abstract

In this paper, we present robust joint non-linear transceiver designs for multiuser multiple-input multiple-output (MIMO) downlink in the presence of imperfections in the channel state information at the transmitter (CSIT). The base station (BS) is equipped with multiple transmit antennas, and each user terminal is equipped with one or more receive antennas. The BS employs Tomlinson-Harashima precoding (THP) for inter-user interference pre-cancellation at the transmitter. We consider robust transceiver designs that jointly optimize the transmit THP filters and receive filter for two models of CSIT errors. The first model is a stochastic error (SE) model, where the CSIT error is Gaussian-distributed. This model is applicable when the CSIT error is dominated by channel estimation error. In this case, the proposed robust transceiver design seeks to minimize a stochastic function of the sum mean square error (SMSE) under a constraint on the total BS transmit power. We propose an iterative algorithm to solve this problem. The other model we consider is a norm-bounded error (NBE) model, where the CSIT error can be specified by an uncertainty set. This model is applicable when the CSIT error is dominated by quantization errors. In this case, we consider a worst-case design. For this model, we consider robust i) minimum SMSE, ii) MSE-constrained, and iii) MSE-balancing transceiver designs. We propose iterative algorithms to solve these problems, wherein each iteration involves a pair of semi-definite programs (SDP). Further, we consider an extension of the proposed algorithm to the case with per-antenna power constraints.