On the beamforming design of millimeter wave UAV networks: Power vs. trade-offs

The millimeter wave (mmWave) technology enables unmanned aerial vehicles (UAVs) to offer broadband highspeed wireless connectivity in 5G/6G networks. However, the limited footprint of a single UAV implementing analog beamforming (ABF) requires multiple aerial stations to operate in swarms to provide ubiquitous network coverage, thereby posing serious constraints in terms of battery power consumption. A possible remedy is to investigate the concept of hybrid beamforming (HBF) transceivers, which use a combination of analog beamformers to achieve higher flexibility in the beamforming design. This approach permits multiple ground users to be served simultaneously by the same UAV, despite involving higher energy consumption than its ABF counterpart. This paper presents a tractable stochastic analysis to characterize the ergodic capacity and power consumption of UAV mmWave networks, focusing on the trade-off between ABF and HBF architectures. A multi-beam coverage model is derived as a function of several UAV-specific parameters, including the number of UAVs, the deployment altitude, the antenna configuration, and the beamforming design. Our results show that, while ABF achieves better ergodic capacity at high altitudes, an HBF configuration with multiple beams, despite the use of more individually power-hungry RF blocks, always consumes less total power with limited capacity degradation.

Automated summary

The millimeter wave technology allows UAVs to provide high-speed wireless connectivity in 5G/6G networks, but the limited coverage of a single UAV implementing analog beamforming (ABF) requires multiple aerial stations to operate in swarms. This paper investigates the concept of hybrid beamforming (HBF) transceivers to achieve higher flexibility in the beamforming design and presents a stochastic analysis comparing the ergodic capacity and power consumption of UAV mmWave networks under ABF and HBF architectures. The results show that HBF configuration with multiple beams has lower total power consumption despite involving higher energy consumption.