Toward UL-DL Rate Balancing: Joint Resource Allocation and Hybrid-Mode Multiple Access for UAV-BS Assisted Communication Systems

TL;DR

This paper introduces a joint resource allocation and hybrid-mode multiple access scheme for UAV-assisted communication systems to balance uplink and downlink data rates, improving performance and robustness.

Contribution

It proposes a novel hybrid-mode multiple access scheme and a joint UL-DL resource allocation algorithm with a closed-form solution, addressing heterogeneous traffic and rate balancing in UAV systems.

Findings

HMMA outperforms pure NOMA or OMA in minimum average rate.

The joint UL-DL algorithm achieves quasi-balanced rates with optimal power allocation.

Enhanced-HMMA shows high robustness against SIC errors.

Abstract

In this paper, we investigate unmanned aerial vehicle (UAV) assisted communication systems that require quasi-balanced data rates in uplink (UL) and downlink (DL), as well as users' heterogeneous traffic. To the best of our knowledge, this is the first work to explicitly investigate joint UL-DL optimization for UAV assisted systems under heterogeneous requirements. A hybrid-mode multiple access (HMMA) scheme is proposed toward heterogeneous traffic, where non-orthogonal multiple access (NOMA) targets high average data rate, while orthogonal multiple access (OMA) aims to meet users' instantaneous rate demands by compensating for their rates. HMMA enables a higher degree of freedom in multiple access and achieves a superior minimum average rate among users than the UAV assisted NOMA or OMA schemes. Under HMMA, a joint UL-DL resource allocation algorithm is proposed with a closed-form optimal solution for UL/DL power allocation to achieve quasi-balanced average rates for UL and DL. Furthermore, considering the error propagation in successive interference cancellation (SIC) of NOMA, an enhanced-HMMA scheme is proposed, which demonstrates high robustness against SIC error and a higher minimum average rate than the HMMA scheme.