Joint 3D Codebook Design and Beam Training for UAV Millimeter-Wave Communications

Owing to its excellent flexibility, unmanned aerial vehicles (UAV) have been widely adopted as aerial access points to provide data collection services for the Internet of Things (IoT) devices. Moreover, Millimeter-Wave (MmWave) aided UAV communications to achieve extremely high data rate has also become the hot issue in recent research. Codebook designing and beam training are the enabling technologies of MmWave communications. However, the existing solutions for communication systems cannot be directly applied in the UAV Mmwave communications, because of the increased complexity in moving and 3D UAV scenarios. Therefore, this paper focuses on joint codebook design and beam training. Firstly, a 3D codebook is designed which can provide flexible access for IoT devices and achieve the optimal system throughput. Then, based on the designed codebook, a Angle Forecast based Fast Beam Alignment (AFFBA) mechanism is proposed. This mechanism infers the potential angle range of ideal AoD from the beam adopted by the current serving UAV. Combing the angle range and the trajectory model of UAV, the optimal beam is forecasted. The proposed joint 3D codebook design and beam training significantly reduce the dimension of beam sweeping space. Simulation results demonstrate the superior performance of the proposed mechanism, and show that the proposed mechanism significantly reduce the beam sweeping space and effectively improve the normalized spectral efficiency (NSE) compared to existing exhaustive training mechanism.

I. Introduction

Thanks to the highly flexibility contrast to conventional base station, unmanned aerial vehicles (UAVs) are given strong expectations in 5G wireless networks [1]. Now, UAV has been widely adopted as aerial access points to provide communication services for Internet of Things (IoT) devices. For example, UAV as aerial relay nodes for dynamic routing, while mitigating the impact of occlusions on the terrestrial links [2]. However, in some scenarios, like video stream services and monitoring tasks [3], the data rate requirements cannot be satisfied with conventional communication technologies. Fortunately, Millimeter-Wave (MmWave) communications with multi-gigahertz bandwidth availability enables high speed data rate transmission for UAV [4]. UAV MmWave communications with flexible coverage, low latency and sufficient bandwidth, has been extensively studied [5].