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Unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) complement each other, promising a variety of benefits for unmanned cooperative systems. When infrastructures for communication are unavailable, such as disaster relief and patrol mission in sparsely populated areas, UGVs can be controlled to go to the esignated areas with the aid of a UAV. Specifically, the UAV hovers over the UGVs, sending commands to the UGVs and obtaining location information from the UGVs. In this paper, we consider integrating millimeter wave communication and UAV–UGV cooperative system. For high mobile unmanned cooperative systems, we develop two joint radar-aided hybrid precoding schemes, which are suitable for a fully connected (FC) hybrid precoding structure and partially connected (PC) hybrid precoding, respectively. Specifically, an effective hybrid precoding scheme is first proposed by using location information to jointly design hybrid precoding and power allocation. Moreover, we also derive the radar parameter estimation problem Cramér-Rao lower bound (CRLB). In order to ensure the minimum quality-of-service (QoS) of UGVs, we propose a QoS-aware power allocation scheme based on the difference-of-two-convex-function (D.C.) programming. Finally, a heuristic hybrid precoding design algorithm, where the analog precoding matrix is usually implemented by low-resolution phase shifters (PSs), is proposed based on antenna dynamic grouping and radar parameter acquisition, with the aim of maximizing the sum-rate of the UAV–UGV cooperative systems. Extensive computer simulation results indicated the validity of the proposed radar-aided location-based hybrid precoding schemes in the UAV–UGV heterogeneous cooperative system. |
