  In this paper, we studied the joint sparse beamforming and power control for
network-assisted full duplex (NAFD) in large-scale distributed antenna system
(L-DAS), where the remote antenna units either be operating in half-duplex mode
or full-duplex mode are all connected to the central processing unit (CPU) via
high-speed backhaul links. With joint processing at CPU, NAFD could achieve
truly flexible duplex, including flexible half-duplex and full-duplex.
Cross-link interference and the finite-capacity backhaul are the main problems
of NAFD in L-DAS. To solve these problems, we aim to maximize the aggregated
rate of uplink and downlink subject to quality of service constraints and
backhaul constraints. Two approaches have been proposed to solve the
optimization problem, where the first approach converts the object function to
the difference of two convex functions with semi-definite relax (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.
