Abstract : We consider a scenario in which an Unmanned Aerial Vehicle (UAV) performs transmit Antenna Selection (AS) and is assisted by a Reconfigurable Intelligent Surface (RIS) for integrated sensing and communication. We optimize the antenna subset and transmit beamformer at the UAV and phase shift at RIS to maximize the beampattern gain towards the target under a specific rate constraint for the communication. To solve this, we propose an alternating optimization based algorithm in which the optimization problem is split into a sequence of sub-problems and presented as semidefinite programs. Our numerical results show that an improved average beampattern gain and outage performance is obtained by increasing number of transmit antennas or number of RIS elements. We show that by increasing the RIS elements, we can obtain the savings of radiated power while keeping the average beampattern gain fixed, a system with subset AS can obtain improved performance compared to a multi-antenna system. Our results also show that an improved average beampattern gain and outage performance can be obtained even when UAV goes away from the user and comes closer to the RIS and target. A discussion on real-time feasibility challenges and potential directions for future work is also presented.
Index terms : Antenna Selection (AS), beampattern gain, Reconfigurable Intelligent Surface (RIS), target, Unmanned Aerial Vehicle (UAV)