Fully-Connected vs. Sub-Connected Hybrid Precoding Architectures for mmWave MU-MIMO

Abstract

Hybrid digital analog (HDA) beamforming has attracted considerable attention in practical implementation of millimeter wave (mmWave) multiuser multiple-input multiple-output (MU-MIMO) systems due to its low power consumption with respect to its digital baseband counterpart. The implementation cost, performance, and power efficiency of HDA beamforming depends on the level of connectivity and reconfigurability of the analog beamforming network. In this paper, we investigate the performance of two typical architectures for HDA MU-MIMO, i.e., the fully-connected (FC) architecture where each RF antenna port is connected to all antenna elements of the array, and the one-stream-per-subarray (OSPS) architecture where the RF antenna ports are connected to disjoint subarrays. We jointly consider the initial beam acquisition phase and data communication phase, such that the latter takes place by using the beam direction information obtained in the former phase. For each phase, we propose our own BA and precoding schemes that outperform the counterparts in the literature. We also evaluate the power efficiency of the two HDA architectures taking into account the practical hardware impairments, e.g., the power dissipation at different hardware components as well as the potential power backoff under typical power amplifier (PA) constraints. Numerical results show that the two architectures achieve similar sum spectral efficiency, but the OSPS architecture outperforms the FC case in terms of hardware complexity and power efficiency, only at the cost of a slightly longer time of initial beam acquisition.

Channel Estimation for 6G V2X Hybrid Systems Using Multi-Vehicular Learning

“…The authors in [23] and [24] propose a grid-based method for FC-HBF architecture, by first estimating the Angles of Arrival/Departure (AoAs/AoDs) of the channel through a closed-loop beam training, after which the path gain of each pair AoA/AoD is derived. In [25], [26], a similar approach is proposed for SC-HBF architecture under practical hardware impairments. In both architectures, the performance tends to be limited by the codebook resolution, while the complexity increases with the number of users.…”

Machine Learning-Inspired Hybrid Precoding for mmWave MU-MIMO Systems with Domestic Switch Network

“…Hybrid precoding also adds constraints to the RF precoder where only B -bit quantized shift can be applied to each element, i.e., where f ( p , q ) is the ( p , q ) th element of F . It has been considered in many studies to achieve full precoding gain [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Most of these algorithms decompose the problem into analog precoder design and digital precoder design separately.…”

“…Hybrid precoding has been studied in much literature. In [ 9 ], the authors investigate the performance of two typical precoding architectures for hybrid precoding, namely fully-connected (FC) and sub-connected (SC). Numerical results show that the SC structure achieves comparable spectral efficiency performance with its counterpart but saves substantial hardware complexity and power consumption.…”

Hierarchical Energy Efficient Hybrid Precoding for Configurable Sub-Connected MIMO Systems

“…Two typical precoding architectures are generally used to realize the hybrid precoding, i.e., fully-connected (FC) and sub-connected (SC) structure. Numerical results show that SC structure achieves comparable spectral efficiency performance with its counterpart but saves a lot of hardware complexity and power consumption [10].…”