Coverage and Rate Analysis of Millimeter Wave NOMA Networks with Beam Misalignment

Abstract

    Non-orthogonal multiple access (NOMA) and millimeter wave (mmWave) are two key enabling technologies for the fifth generation (5G) wireless networks. In this paper, we develop a general performance analysis framework for downlink NOMA transmission in mmWave networks with spatially random users taking into account link blockages and directional beamforming. To facilitate NOMA transmission in mmWave networks, we propose an angle-based user pairing strategy, where the base station first randomly selects one user and then pairs it with the line-of-sight user that has the minimum relative angle difference. The proposed strategy increases the probability that both NOMA users are covered by the main lobe created by directional beamforming. To account for the randomness of link blockages and user locations, we consider dynamic user ordering among the paired NOMA users. Tools from stochastic geometry are utilized to derive the coverage probability, outage sum rate, and ergodic sum rate of the proposed NOMA scheme, where beam misalignment at both the base station and users is taken into account. Simulations validate the performance analysis and show that the proposed NOMA scheme achieves a larger coverage probability and higher outage and ergodic sum rates than conventional NOMA with distance-based user pairing and orthogonal multiple access.

Description

    We develop a general and tractable performance analysis framework for downlink NOMA transmission in mmWave networks with spatially random users taking into account link blockages, directional beamforming, beam misalignment, user pairing, and dynamic user ordering. We propose a novel angle-based user pairing strategy to facilitate NOMA transmission in mmWave networks by increasing the probability of exploiting antenna array gains.

We derive the distributions of random variables relevant for performance analysis, including the distances between the base station and the users, angle difference between the paired NOMA users, and the total directivity gains between the base station and the paired NOMA users. We derive the coverage probability, the outage sum rate, and the ergodic sum rate of the proposed NOMA scheme.