Coverage Probability of Relay-Assisted NOMA Millimeter Wave Networks with Steerable-Beam

• Published in: Computer networks (Amsterdam, Netherlands : 1999) Vol. 209; p. 108929
• Main Authors: Tang, Kun, Jiao, Feiyu, Liu, Xuxun, Che, Wenquan, Xue, Quan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22.05.2022; Elsevier Sequoia S.A
• Subjects: coverage probability; Exact solutions; Mathematical analysis; Microwave frequencies; Millimeter waves; Millimeter-wave; non-orthogonal multiple access; Nonorthogonal multiple access; Optimization; Relay; resource allocation; steerable-beam; steerable-beam; coverage probability; Millimeter-wave; resource allocation; non-orthogonal multiple access
• ISSN: 1389-1286; 1872-7069
• DOI: 10.1016/j.comnet.2022.108929

In this paper, we consider a relay-assisted non-standalone (NSA) 5G network, where source (S) intends to transmit signals to users by assistance with a relay R, which receives the signals from S operating in microwave frequency and transfers to target users by utilizing steerable-beam non-orthogonal multiple access (NOMA) scheme operating in millimeter-wave (mmWave) frequency. The steerable-beam NOMA scheme can flexibly switch between single-beam and multi-beam modes according to angle difference of users in NOMA group, i.e., when at least one angle difference is smaller than mmWave beamwidth of main lobe, R adopts a single-beam for achieving NOMA transmission, otherwise multi-beam scheme is used to complete NOMA transmission. For insight into the performance of steerable-beam NOMA scheme, we analyze the coverage probability of the system in-depth for deriving the analytical expressions and approximately closed-form solutions of target users’ coverage probabilities within a NOMA group, where the first user Uo is selected with the shortest distance to the S and the paired user Up is determined based on the minimum angle difference to the first user. However, when R adopts multi-beam, the user with the smallest angle difference to the Uo may not be the best paired user due to the influence of path attenuation and antenna allocation. We then propose a two-stage scheme to obtain optimal user pairing by jointly considering the angle, distance, and sum-rate, while optimizing power allocation subject to maximize the sum-rate. Simulation results illustrate the coverage performance of the system with steerable-beam NOMA scheme for different parameters, and demonstrate the advantages of the proposed two-stage strategy offers a significant improvement in terms of average sum-rate compared to other schemes.