Hybrid Multiple Access Scheme Employing NOMA and OMA Simultaneously Under Non-uniform User Distribution and Multiple Transmit Antennas

Abstract

The fifth generation (5G) mobile communication systems provide increased functionality and performance, and can be implemented through orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA). Both methods present advantages and disadvantages under certain conditions. In this study, we analyze the performance of a hybrid multiple access scheme using NOMA and OMA simultaneously in a practical scenario under non-uniform user distribution and multiple transmit antennas through computer simulations to verify its effectiveness. The proposed hybrid multiple access scheme avoids the NOMA-specific performance deterioration caused due to small channel gain differences between users by applying OMA within the same bandwidth. Additionally, we implement resource allocation to account for both the channel gain and desired user traffic volume considering the diversified wireless service for Beyond 5G (B5G). We apply the Thomas cluster process as user distribution and maximum ratio transmission (MRT) as transmit diversity, and elucidate the effects of the non-uniformity of user distribution and an increase in the number of transmit antennas on the performance of the proposed hybrid multiple access scheme.