Uplink Multiple Access Based on MIMO-OFDM with Adaptive Super-Orthogonal Convolutional Codes for Ultra Reliable and Low Latency Communications

Abstract

The combination of low-rate channel coding employing simple non-iterative decoder and non-orthogonal multiple access (NOMA) is a promising approach for the development of Tactile Internet which requires ultra reliable and low- latency communications (URLLC) without compromising spectral efficiency. In the framework of NOMA, each user in the uplink of a multiuser network is subject to different propagation loss depending on its distance from the base station (BS). Consequently, the performance of the user located far from the BS is significantly degraded due to strong interference by the users closer to the BS (i.e., near- far problem). In this paper, we consider an uplink NOMA based on MIMO-OFDM with a class of low-complexity low- rate convolutional codes, namely, super-orthogonal convolutional code (SOCC), and propose an adaptive coding algorithm to alleviate the near-far problem without transmission power control which typically results in severe loss of power amplifier efficiency. Numerical results demonstrate that our system with the proposed algorithm outperforms the conventional orthogonal multiple access scheme in terms of reliability and spectral efficiency.