5 research outputs found
A Rank-Constrained Coordinate Ascent Approach to Hybrid Precoding for the Downlink of Wideband Massive (MIMO) Systems
© 2023 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/TVT.2023.3293933.[Abstract]: An innovative approach to hybrid analog-digital precoding for the downlink of wideband massive MIMO systems is developed. The proposed solution, termed Rank-Constrained Coordinate Ascent (RCCA), starts seeking the full-digital precoder that maximizes the achievable sum-rate over all the frequency subcarriers while constraining the rank of the overall transmit covariance matrix. The frequency-flat constraint on the analog part of the hybrid precoder and the non-convex nature of the rank constraint are circumvented by transforming the original problem into a more suitable one, where a convenient structure for the transmit covariance matrix is imposed. Such structure makes the resulting full-digital precoder particularly adequate for its posterior analog-digital factorization. An additional problem formulation to determine an appropriate power allocation policy according to the rank constraint is also provided. The numerical results show that the proposed method outperforms baseline solutions even for practical scenarios with high spatial diversity.Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G 2019/01This work has been supported in part by grants ED431C 2020/15 and ED431G 2019/01 (to support the Centro de Investigación de Galicia “CITIC”) funded by Xunta de Galicia and ERDF Galicia 2014-2020, and by grants PID2019-104958RB-C42 (ADELE) and PID2020-118139RB-I00 funded by MCIN/AEI/10.13039/501100011033. The authors thank the Defense University Center at the Spanish Naval Academy (CUD-ENM) for all the support provided for this research
System Energy-Efficient Hybrid Beamforming for mmWave Multi-user Systems
This paper develops energy-efficient hybrid beamforming designs for mmWave
multi-user systems where analog precoding is realized by switches and phase
shifters such that radio frequency (RF) chain to transmit antenna connections
can be switched off for energy saving. By explicitly considering the effect of
each connection on the required power for baseband and RF signal processing, we
describe the total power consumption in a sparsity form of the analog precoding
matrix. However, these sparsity terms and sparsity-modulus constraints of the
analog precoding make the system energy-efficiency maximization problem
non-convex and challenging to solve. To tackle this problem, we first transform
it into a subtractive-form weighted sum rate and power problem. A compressed
sensing-based re-weighted quadratic-form relaxation method is employed to deal
with the sparsity parts and the sparsity-modulus constraints. We then exploit
alternating minimization of the mean-squared error to solve the equivalent
problem where the digital precoding vectors and the analog precoding matrix are
updated sequentially. The energy efficiency upper bound and a heuristic
algorithm are also examined for comparison purposes. Numerical results confirm
the superior performances of the proposed algorithm over benchmark
energy-efficiency hybrid precoding algorithms and heuristic ones.Comment: submitted to TGC