MIMO-Aided Nonlinear Hybrid Transceiver Design for Multiuser Mmwave Systems Relying on Tomlinson-Harashima Precoding

Abstract

Hybrid analog-digital (A/D) transceivers designed for millimeter wave (mmWave) systems have received substantial research attention, as a benefit of their lower cost and modest energy consumption compared to their fully-digital counterparts. We further improve their performance by conceiving a Tomlinson-Harashima precoding (THP) based nonlinear joint design for the downlink of multiuser multiple-input multipleoutput (MIMO) mmWave systems. Our optimization criterion is that of minimizing the mean square error (MSE) of the system under channel uncertainties subject both to realistic transmit power constraint and to the unit modulus constraint imposed on the elements of the analog beamforming (BF) matrices governing the BF operation in the radio frequency domain. We transform this optimization problem into a more tractable form and develop an efficient block coordinate descent (BCD) based algorithm for solving it. Then, a novel two-timescale nonlinear joint hybrid transceiver design algorithm is developed, which can be viewed as an extension of the BCD-based joint design algorithm for reducing both the channel state information (CSI) signalling overhead and the effects of outdated CSI. Moreover, we determine the near-optimal cancellation order for the THP structure based on the lower bound of the MSE. The proposed algorithms can be guaranteed to converge to a Karush-Kuhn-Tucker (KKT) solution of the original problem. The simulation results demonstrate that our proposed nonlinear joint hybrid transceiver design algorithms significantly outperform the existing linear hybrid transceiver algorithms and approach the performance of the fully-digital transceiver, despite its lower cost and power dissipation.

Hybrid Nonlinear Transceiver Optimization for the RIS-Aided MIMO Downlink

“…In order to eliminate the explicit effect of the power constraint, the digital TPC F D is transformed into the following formula [10]…”

“…The iterative algorithms such as stochastic successive convex approximation (SSCA) [7], penalty-concave-convex procedure (CCCP) [8] and gradient projection (GP) [9], invest computational complexity for seeking improved performance. The authors of [10] successively optimize the elements of the analog TPC successively while keeping other elements fixed. Although the element-wise subproblem is easy to solve, the performance remains suboptimal owing to relying on iterations among numerous variables.…”

“…The interference between users and data streams can be further mitigated by employing a nonlinear transceiver. Nonlinear transceivers include Tomlinson-Harashima precoders (THPs) [10], [18]- [24] at the transmitters or decision feedback equalizers (DFEs) [20]- [24] at the receivers. Most papers aim for optimizing the THPs and DFEs using either zero-forcing (ZF) [18]- [20] or Cholesky decomposition based methods [21]- [24].…”

“…However, the ZF method achieves limited system performance owing to potential noise-amplification, while the conventional Cholesky decomposition-based method cannot be directly employed in multiuser-MIMO (MU-MIMO) systems. The authors of [10] addressed this problem by conceiving a partial derivative (PD)-based method. To avoid the high complexity caused by iterations between the receivers' equalizers and the THP feedback matrix, we conceive the Cholesky decomposition based MU-MIMO solution, so that the receivers, as well as the THP feedback matrix and the permutation matrix can be jointly optimized.…”

System-Level Assessment of Low Complexity Hybrid Precoding Designs for Massive MIMO Downlink Transmissions in Beyond 5G Networks

“…The concept of precoding based on adaptive RF-chain-to-antenna was only introduced in [13] for single user (SU) scenarios but showed promising results. In [14], a nonlinear hybrid transceiver design relying on Tomlinson-Harashima precoding was proposed. Their approach only considers FC architectures but can achieve a performance close to the fully-digital transceiver.…”