Hybrid CRB Analysis for Location Sensing in UAV mmWave Systems Under Jittering Effects

Unmanned aerial vehicle (UAV) systems are vulnerable to the inevitable UAV jitter, the impacts of which on both communications and sensing become more detrimental in the high frequency millimeter wave (mmWave) band. While the UAV jittering effects on communications have been intensively investigated, those on sensing have so far drawn little attention. In this paper, we investigate the location sensing performance of the UAV mmWave system in the presence of jitter. To this end, we identify that the location sensing performance under jittering effects is determined not only the deterministic target's location, but also random instantaneous attitude angles of the UAV. Based on this identification, we derive the closed-form expression of the hybrid Cramer-Rao bound (HCRB) and its approximation to characterize the location sensing performance of our considered system, revealing how the UAV jitter introduces extra location sensing error. Through numerical results, we validate our HCRB analysis. Moreover, we show that the detrimental effects of UAV jitter can be well alleviated by increasing the number of measurements.