Fully-/Partially-Connected Hybrid Beamforming 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 the low power consumption with respect to its fully 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 that can be regarded as extreme cases, namely, the fully-connected (FC) and the one-stream-per-subarray (OSPS) architectures. In the FC architecture each RF antenna port is connected to all antenna elements of the array, while in the OSPS architecture the RF antenna ports are connected to disjoint subarrays. We jointly consider the initial beam acquisition and data communication phases, such that the latter takes place by using the beam direction information obtained by the former. We use the state-of-the-art beam alignment (BA) scheme previously proposed by the authors and consider a family of MU-MIMO precoding schemes well adapted to the beam information extracted from the BA phase. We also evaluate the power efficiency of the two HDA architectures taking into account the power dissipation at different hardware components as well as the power backoff under typical power amplifier constraints. Numerical results show that the two architectures achieve similar sum spectral efficiency, while the OSPS architecture is advantageous with respect to the FC case in terms of hardware complexity and power efficiency, at the sole cost of a slightly longer BA time-to-acquisition due to its reduced beam angle resolution. Index TermsX.

Performance Improvement for Multi-User Millimeter-Wave Massive MIMO Systems

“…• Fully-connected hybrid beamforming: According to [8], [10], the achievable spectral efficiency of a fully-connected hybrid beamforming structure could approach that obtained with fully digital beamforming with the appropriate signal processing design. However, hardware implementation and computational complexity currently are prohibitively high for the practical implementation of this kind of structure.…”

“…0] T ∈ N K ×1 for j = 1, as the j th zero-interference vector [35]. Then, the RZFBF receiver becomes a practical solution to (10), which is written as…”

A Kronecker-Based Sparse Compressive Sensing Matrix for Millimeter Wave Beam Alignment

“…We further assume that phase shifting as well as the amplitude control can be performed in the analog domain. This is a practically feasible assumption for mmWave systems as it has been shown in the literature [14] [15]. Assuming θ l ∈ [− π 2 , π 2 ] and φ l ∈ [− π 2 , π 2 ] respectively the AoD and AoA of the lth propagation path between the BS and UE, the array response vectors are given by…”

Min-SINR Maximization for mmWave Massive MISO-NOMA System With Randomly Directional Beamforming

“…Moreover, the BS serves a cluster of users over a beam achieved by RDB. Particularly, since analog precoding is adopted at the BS, we have Ns ≤ N ≤ M [5], [8], [41]. Without loss of generality, we assume N = N s .…”