Preamble Design Technique for GMSK-Based Beamforming System With Multiple Unmanned Aircraft Vehicles

The use of beamforming techniques at the ground station is known to be effective in obtaining coverage extension or SNR gain for communication with unmanned aerial vehicles (UAVs). When a UAV moves, periodic beam tracking is necessary to maintain beam gain. To track beams for multiple UAVs, the ground station needs to receive different preambles from multiple UAVs. In this paper, a Hadamard sequence is considered for designing preambles for multiple UAVs because of its ideal cross-correlation property. A preamble that is appropriate for a Gaussian minimum shift keying (GMSK)-based communication system with multiple UAVs is proposed after analyzing the property of received signals in the system with the Hadamard sequence as the input. A preamble appropriate for asynchronous channel environments is also proposed after analyzing the property of the signals received from multiple UAVs with different time delays. The performance of the proposed preambles in the GMSK-based communication system with multiple UAVs is evaluated via simulation with a 3-D spatial channel model in both synchronous and asynchronous channel environments.