Antenna Selection in MIMO Non-orthogonal Multiple Access Systems

TL;DR

This paper develops efficient antenna selection algorithms for two-user MIMO NOMA systems, improving sum-rate and user fairness while reducing computational complexity, applicable to fixed power and cognitive radio-inspired scenarios.

Contribution

Introduces novel antenna selection schemes for MIMO NOMA, providing near-optimal performance with lower complexity in different NOMA scenarios.

Findings

A$^3$-AS maximizes sum-rate in F-NOMA.

AIA-AS enhances user fairness.

MCG-AS achieves near-optimal secondary user rate.

Abstract

This paper considers the joint antenna selection (AS) problem for a classical two-user MIMO non-orthogonal multiple access (NOMA) system, where both the base station (BS) and users (UEs) are equipped with multiple antennas. Specifically, several computationally-efficient AS algorithms are developed for two commonly-used NOMA scenarios: fixed power allocation NOMA (F-NOMA) and cognitive radio-inspired NOMA (CR-NOMA). For the F-NOMA system, two novel AS schemes, namely max-max-max AS (A$^3$-AS) and max-min-max AS (AIA-AS), are proposed to maximize the system sum-rate, without and with the consideration of user fairness, respectively. In the CR-NOMA network, a novel AS algorithm, termed maximum-channel-gain-based AS (MCG-AS), is proposed to maximize the achievable rate of the secondary user, under the condition that the primary user's quality of service requirement is satisfied. The asymptotic closed-form expressions of the average sum-rate for A$^3$-AS and AIA-AS and that of the average rate of the secondary user for MCG-AS are derived, respectively. Numerical results demonstrate that the AIA-AS provides better user-fairness, while the A$^3$-AS achieves a near-optimal sum-rate in F-NOMA systems. For the CR-NOMA scenario, MCG-AS achieves a near-optimal performance in a wide SNR regime. Furthermore, all the proposed AS algorithms yield a significant computational complexity reduction, compared to exhaustive search-based counterparts.