UAV-Assisted Cooperative NOMA System with the nth Best Relay Selection

Abstract

We propose a downlink non-orthogonal multiple access (NOMA) architecture with a source, N one-way unmanned aerial vehicle (UAV) relays, and K destination users where the amplify-and-forward protocol is considered with the partial relay selection strategy. Then, we derive closed-form expressions for the bit error probability (BEP) of the NOMA users over the Rayleigh fading channel. This research investigated the selection of the nth best available UAV relay while presenting the bit error rate (BER) performance of a NOMA system. In addition, we analyze the diversity order and develop an asymptotic closed-form expression of the BEP in the high signal-to-noise ratio regime. To verify the accuracy of the analytical study of BER, numerical results are also provided taking into account the number of UAV relays, path loss exponent, power allocation coefficient, and channel gains. Finally, we validate that the simulation results precisely match our proposed theoretical analysis.