DOA Estimation for Arbitrarily Distributed Subarrays in UAV Swarm

In this paper, we consider the problem of DOA estimation for the arbitrarily distributed subarrays with application in unmanned aerial vehicle (UAV) swarm, where multiple small UAVs equipped with uniform linear array (ULA) are separated by unknown intervals due to the dynamic moving. Three parameters are used to formulate the steering vector, i.e., the direction of arrivals (DOAs) of the target users, the intervals of UAVs, and the orientation angles of UAVs. We first estimate the orientation angles using an auxiliary user and then obtain the DOAs via a search free rooting method, regardless of the intervals of the UAVs. The deterministic Cramér-Rao bound (CRB) of the DOA and orientation angle are derived in closed-form. Finally, numerical examples are provided to corroborate the proposed studies.