Downlink Asynchronous Non-Orthogonal Multiple Access Systems with Imperfect Channel Information

Abstract

In this letter, we study a two-user downlink asynchronous non-orthogonal multiple access (ANOMA) with limited feedback. We employ the max-min criterion for the power allocation and derive the closed-form expressions for the upper and lower bounds of the max-min rate. It is demonstrated that ANOMA can achieve the same or even higher average maxmin rate with a lower feedback rate compared with NOMA. Moreover, we propose a quantizer optimization algorithm which applies to both NOMA and ANOMA. Simulation results show that the optimized quantizer significantly improves the average max-min rate compared with the conventional uniform quantizer, especially in the scenario with a low feedback rate.Index Terms-Asynchronous non-orthogonal multiple access, limited feedback, quantizer optimizationThe authors are with

Detection of symbol‐asynchronous uplink NOMA with imperfect time offsets

“…The work in [28] studied the MUD for the asynchronous multiple access system with perfect time offsets, where time offsets between users were treated as an additional resource in the multiple access system. Works in [29, 30] focused on the downlink asynchronous NOMA system, where the authors in [29] considered the outage probability under imperfect channel information, and the authors in [30] optimised the average transmit power under the downlink transmit beamforming for wireless transmission. We are motivated to design the MUD algorithm for the uplink asynchronous NOMA system with imperfect time offsets, and users arrive at the BS with equal power.…”