  This paper investigates the problem of resource allocation for joint
communication and radar sensing system on rate-splitting multiple access (RSMA)
based unmanned aerial vehicle (UAV) system. UAV simultaneously communicates
with multiple users and probes signals to targets of interest to exploit
cooperative sensing ability and achieve substantial gains in size, cost and
power consumption. By virtue of using linearly precoded rate splitting at the
transmitter and successive interference cancellation at the receivers, RSMA is
introduced as a promising paradigm to manage interference as well as enhance
spectrum and energy efficiency. To maximize the energy efficiency of UAV
networks, the deployment location and the beamforming matrix are jointly
optimized under the constraints of power budget, transmission rate and
approximation error. To solve the formulated non-convex problem efficiently, we
decompose it into the UAV deployment subproblem and the beamforming
optimization subproblem. Then, we invoke the successive convex approximation
and difference-of-convex programming as well as Dinkelbach methods to transform
the intractable subproblems into convex ones at each iteration. Next, an
alternating algorithm is designed to solve the non-linear and non-convex
problem in an efficient manner, while the corresponding complexity is analyzed
as well. Finally, simulation results reveal that proposed algorithm with RSMA
is superior to orthogonal multiple access and power-domain non-orthogonal
multiple access in terms of power consumption and energy efficiency.
