Being a key technology for beyond fifth-generation wireless systems, joint communication and radar sensing (JCAS) utilizes the reflections of communication signals to detect foreign objects and deliver situational awareness. A cellular-connected unmanned aerial vehicle (UAV) is uniquely suited to form a mobile bistatic synthetic aperture radar (SAR) with its serving base station (BS) to sense over large areas with superb sensing resolutions at no additional requirement of spectrum. This paper designs this novel BS-UAV bistatic SAR platform, and optimizes the flight path of the UAV to minimize its propulsion energy and guarantee the required sensing resolutions on a series of interesting landmarks. A new trajectory planning algorithm is developed to convexify the propulsion energy and resolution requirements by using successive convex approximation and block coordinate descent. Effective trajectories are obtained with a polynomial complexity. Extensive simulations reveal that the proposed trajectory planning algorithm outperforms significantly its alternative that minimizes the flight distance of cellular-aided sensing missions in terms of energy efficiency and effective consumption fluctuation. The energy saving offered by the proposed algorithm can be as significant as 55%.Index Terms-Joint communication and radar sensing, bistatic synthetic aperture radar, cellular-connected unmanned aerial vehicle, block coordinate descent.
I. INTRODUCTIONRecent advancements in the fifth-generation and beyond (5G/B5G) networks are increasingly enabling extensive background situation-and position-aware smart applications, including autonomous driving, distant medical care, and smart industry [1]. 5G/B5G networks are also envisioned to offer high-resolution sensing in support of these applications [2]. For this reason, joint communication and radar sensing (JCAS) has been deemed as one of the essential technologies in 5G/B5G systems [3]. By integrating radio communication and sensing into a single system, JCAS measures the reflections of communication signals to sense the location, velocity, and feature signal of targets and motions [4], [5]. This is