Exploiting Multi-Hop RIS-Assisted UAV Communications: Performance Analysis

Future wireless communication networks are expected to extensively utilise unmanned aerial vehicles (UAVs) and reconfigurable intelligent surfaces (RISs) to improve performance, extend coverage, and enhance energy efficiency. In this letter, the fundamental limits of the system performance of a multi-hop RIS-assisted UAV communication system are analysed and characterised. We derive accurate closed-form approximations for the statistical distributions of the RIS-assisted channels which are then exploited to derive an analytical expression for the signal-to-noise ratio (SNR), outage probability, and bit error rate (BER). Moreover, we derive outage probability expressions in the high SNR regime. Our analysis demonstrates that strategically placing RIS with an adequate number of elements can effectively enhance the performance of UAV communications in different fading scenarios. RIS dynamically adapts to changing channels and user positions, enhancing performance as the UAV navigates diverse geographical areas, when ideal Line of Sight (LoS) conditions may not be consistently attainable due to the UAV's altitude and dynamic mobility.