Two-Timescale Hybrid Analog-Digital Beamforming for mmWave Full-Duplex MIMO Multiple-Relay Aided Systems

Abstract

Due to the severe pathloss experienced by electromagnetic wave transmission in the mmWave band, one challenge for the design of millimeter wave (mmWave) communication systems is coverage extension. Aiming to improve the coverage and sum rate performance of mmWave communications, we investigate new schemes for the design of full-duplex (FD) mmWave multiple-input multiple-output (MIMO) multiple-relay systems. Specifically, we propose a novel two-timescale analog-digital hybrid beamforming scheme to maximize the sum rate, while reducing the system complexity and channel state information (CSI) signalling overhead, as well as mitigating the effects of selfinterference and CSI errors caused by the delays. In the proposed scheme, the long-timescale analog beamforming matrices are designed based on the available channel statistics and updated in a frame-based manner, where a frame contains a fixed number of time slots, while for each time slot, the short-timescale digital beamforming matrices are optimized based on low-dimensional effective CSI matrices available in real-time. We develop an effective analog beamforming algorithm based on the cut-set bound and stochastic successive convex approximation (SSCA) and an innovative digital beamforming algorithm that relies on the theory of penalty dual decomposition (PDD) to maximize the system sum rate. The convergence properties and computational complexity of the proposed algorithms are also examined. Our simulation results show that the proposed two-timescale hybrid beamforming design significantly outperforms the conventional beamforming algorithms both in terms of the CSI-signalling overhead and the achievable sum rate in the presence of CSI delays.

On the Physical Layer Security of Untrusted Millimeter Wave Relaying Networks: A Stochastic Geometry Approach

“…Furthermore, the coverage probability of spatially random decode-and-forward (DF) relays was investigated both for direct transmission and for relay-aided links in [10] to highlight the performance gains brought about by relaying. By investigating a full-duplex mmWave multi-relay system, Cai et al [11] proposed an innovative two-timescale analogdigital hybrid beamforming scheme, based on low-dimensional effective matrices for maximizing the sum rate. The authors of [12] also investigated the potential advantages of utilizing two-way amplify-and-forward (AF) relays to assist the bidirectional exchange of data between two nodes in a mmWave system.…”

Practical Hybrid Beamforming for Millimeter Wave Massive MIMO Full Duplex with Limited Dynamic Range

“…(57) Further, taking the gradient for G RF leads to the same generalized eigenvector solution as in (24). Also, note that this alternative representation has the same form as (50).…”

“…In [19], the authors proposed joint HYBF and combining for a point-to-point FD communication. In [24], a novel HYBF design for an FD mmWave MIMO relay is proposed. In [25], a machine-learning based HYBF for a oneway mmWave FD relay is investigated.…”

“…Initialize: G RF , V j , ∀j ∈ D and U k , ∀k ∈ U. Set: µ i = 0 and µ i = µ imax ∀i ∈ M 0 or ∀i ∈ M k , ∀k ∈ U Repeat until convergence Compute G RF (24), do unvec(G RF ) and ∠G RF . Compute F RF with (28), and do ∠F RF .…”

Deep-Unfolding Beamforming for Intelligent Reflecting Surface assisted Full-Duplex Systems

“…Fortunately, there have been key advances to address this issue [7]- [9], such as passive suppression, analog and digital cancellations, etc.. Therefore, the FD technique has many applications in wireless communications, such as bidirectional communications [10], relays [11], [12], and multi-user systems [13], [14].…”