Joint Sparse Beamforming and Power Control for Large-scale DAS with Network-Assisted Full Duplex

Abstract

In this paper, we studied joint sparse beamforming and power control for network-assisted full duplex (NAFD) in a large-scale distributed antenna system (L-DAS), where the remote antenna units are operating in either half-duplex mode or fullduplex mode and are all connected to the central processing unit (CPU) via high-speed backhaul links. With joint processing at the CPU, NAFD can achieve truly flexible duplex, including flexible half-duplex and full-duplex modes. Cross-link interference and finite-capacity backhaul are the main problems of NAFD in an L-DAS. To solve these problems, we aim to maximize the aggregated uplink and downlink rates subject to quality-ofservice constraints and backhaul constraints. Two approaches have been proposed to solve the optimization problem, where the first approach converts the objective function to the difference of two convex functions with semi-definite relaxation (SDR), and then, an iterative SDR-block coordinate descent method is applied to solve the problem. The second method is based on sequential parametric convex approximation. Simulation results have shown that the proposed algorithms yield a higher rate gain compared to the traditional time-division duplex scheme.Index Terms-sparse beamforming, power control, networkassisted full duplex, Large-scale DAS (L-DAS), semi-definite relaxation-block coordinate descent (SDR-BCD), sequential parametric convex approximation (SPCA).