Optimal Analog Beamforming and Power Allocation for Multiuser TDMA Systems

TL;DR

This paper develops globally optimal algorithms for joint analog beamforming and power allocation in multiuser TDMA systems, improving performance benchmarks under hardware constraints.

Contribution

It introduces branch-and-bound algorithms for optimal phase-shift design, addressing a key challenge in multiuser beamforming with hardware-efficient architectures.

Findings

Proposed algorithms achieve global optimality.

Numerical results validate the effectiveness of the algorithms.

Benchmarks for low-complexity methods are established.

Abstract

The joint design of analog beamforming and power allocation is investigated for a single radio-frequency chain multiuser time-division multiple access system under a max-min signal-to-noise ratio (SNR) criterion. A hardware-efficient phased-array architecture is considered, where the beamforming vector is shared by all users and is subject to constant-modulus constraints. For any fixed analog beamformer, the optimal power allocation is first derived in closed form, by which the original problem is reduced to phase-shift optimization only. Then, globally optimal branch-and-bound (BB) algorithms are developed for discrete and continuous phase shifts. Numerical results show that the proposed BB algorithms achieve the global optimum and provide reliable benchmarks for evaluating the performance gap of low-complexity alternating-optimization methods.