Laser-powered UAV Wireless Communication Systems Design

With the promotion and application of UAVs in life,UAVs can be used to solve sudden obstacles in communication services.The UAV-assisted wireless communication has recently become a promising solution to improve the coverage and network capacity of the terrestrial wireless communication systems,by exploiting UAVs as mobile relays or mobile base stations.However,as the development of the UAV industry continues to accelerate,the spread of applications continues to expand,the bottleneck of the endurance capability of UAVs is becoming more prominent.The UAVs' operation is quite energy-consuming in order to support their propulsion in the air,communication with the ground devices,as well as various application-specific purposes,while conventional battery-powered UAVs only have very limited battery capacity.Therefore,it is challenging to practically implement the UAV-assisted wireless communication systems in a large scale.In order to alleviate this problem,various approaches have been proposed to reduce the UAV's energy consumption,by,e.g.,reducing the UAV's weight and designing energy efficient UAV traveling path.Despite these research efforts,the energy supply for the battery-powered UAVs is still fundamentally unsustainable due to the finite battery capacity.Recently,laser power is becoming a viable solution to provide unlimited endurance aloft for UAVs in flight.As compared to other wireless power transfer(WPT)techniques enabled by radio frequency(RF)signals,the laser-beamed power transfer is able to deliver much larger energy amounts to the receivers with narrower energy beam divergence.Therefore,the laser WPT is expected to efficiently support various energy-hungry operations of the UAVs over a long distance.The filed tests have successfully shown the feasibility of laser-powered UAVs.The research of laser-powered UAV wireless communication systems is a very interesting and promising topic.And to our best knowledge,the design of laser-powered UAV wireless communication with laser energy harvesting constraints has not been investigated yet.In this paper,we study a laser-powered UAV wireless communication system,where laser transmitters send laser beams to charge a UAV in flight,and the UAV uses the harvested laser energy to communicate with ground stations.To maintain the UAV's sustainable operation,its total energy consumption cannot exceed that harvested from the laser transmitter.Under such a laser energy harvesting constraint,we maximize the downlink communication throughput from the UAV to each ground station over a finite time duration,by jointly optimizing the UAV's trajectory and its transmit power allocation.However,due to the complicated UAV energy consumption model,this problem is non-convex and difficult to be solved.To tackle the problem,we propose an efficient solution to balance the tradeoff between maximizing the performance of laser energy harvesting versus wireless communication at the UAV by applying the techniques of alternating optimization and sequential convex programming(SCP).Finally,numerical results are provided to validate the communication throughput performance of the proposed design.