Non-orthogonal multiple access for unmanned aerial vehicle communication system

Abstract

The Unmanned Aerial Vehicle (UAV) assisted communication systems provide users a unique connectivity platform to support high data traffic demand of the future. However, the practical proliferation of the aerial nodes is highly involved in finding solutions to the challenges of low spectral efficiency and limited energy reserves of the system. In spite of the fact that the power domain Non-Orthogonal Multiple Access (NOMA) has established its proficiency for the next generation terrestrial wireless networks, the design and validation of NOMA’s performance are still needed in the new perspective of an aerial Base Station (BS) deployment. Hence, the thesis investigates the capability of NOMA as a promising candidate for future aerial communication systems with the objectives to maximize jointly data-rate, coverage, and energy efficiency of the system. First, NOMA’s feasibility is established by formulating the problem of achievable sum-rate constituting a joint function of power allocation and UAV-BS altitude. Then, a constrained coverage expansion methodology, facilitated by the increase of NOMA user-rate is proposed. Next, a swarm intelligence based user-pairing strategy jointly optimized with UAV altitude and user power allocation is devised to minimize the transmission power of the aerial system. Finally, the formulated non-linear fractional programming problem of energy efficiency maximization is solved using a nested Dinkelbach’s structure. Taken together, the presented results manifest that NOMA performs better than the baseline scheme of Orthogonal Multiple Access (OMA). Particularly, the proposed NOMA schemes achieve 30% coverage radius expansion, 18% spectral efficiency enhancement, and 25% transmission power reduction compared to OMA. In addition, two times improvement in energy efficiency is observed for the NOMA system as it achieves 3 bps/joule compared to 1.5 bps/joule of OMA in dense-urban deployment. In conclusion, the research findings prove the proficiency of NOMA for future aerial communication systems.