A Multiple Base Stations Cooperation Strategy for Downlink Transmission in Cellular and UAV Integrated Networks

This paper studies the UAV downlink transmission problem in a cellular and UAV integrated network, and proposes a multiple base station (BS) cooperation strategy for improving the downlink transmission performance for an aerial UAV. The proposed cooperation strategy uses multiple BSs to provide downlink transmission for a UAV in a cooperative manner with an objective to improve the coverage provability for the UAV while not largely reducing the spectrum efficiency of the network. To achieve the objective, a network utility function is introduced to find the optimal number of cooperative BSs, taking into account both the coverage probability for a UAV and the normalized spectrum efficiency of the network. Moreover, the concept of a cooperation area for a UAV is introduced and the radius of the cooperation area is derived in order to determine the optimal cooperative BSs. Based on the cooperation area determined for a UAV, the optimal number of BSs that are closest to the UAV are supposed to be selected as the cooperative BSs among those BSs which have a link to the UAV with a high LoS probability. Simulation results show that the proposed cooperation strategy can significantly improve the downlink transmission performance in terms of the coverage probability for a UAV compared with a single BS strategy while not largely reducing the normalized spectrum efficiency of the network.