High-throughput unmanned aerial vehicle (UAV) communication may unleash the true potential of novel applications for aerial vehicles but also represents a threat for cellular networks due to the high levels of generated interference. In this article, we investigate how a beamforming system installed on board a UAV can be efficiently used to ensure high-throughput uplink UAV communications with minimum impact on the services provided to users on the ground. We study two potential benefits of beamforming, namely, spatial filtering of interference and load balancing, considering different beam switching methodologies. Our analysis is based on system-level simulations followed by a series of measurement campaigns in live Long-Term Evolution (LTE) networks. Our results show that using UAV-side beamforming has a great potential to increase uplink throughput of a UAV while mitigating interference. When beamforming is used, even up to twice as many UAVs may be served within a network compared with UAVs using omni-directional antennas, assuming a constant uplink throughput target. However, to fully exploit the potential of beamforming, a standardized solution ensuring alignment between network operators and UAV manufacturers is required.
The usage of beamforming in Unmanned Aerial Vehicles (UAVs) has the potential of significantly improving the air-to-ground link quality. This paper presents the outcome of experimental trial of such a UAV-based beamforming system over live cellular networks. A testbed with directional antennas has been built for the experiments. It is shown that beamforming can extend the signal coverage due to antenna gain, as well as spatially reduce interference leading to higher signal quality. Moreover, it has a positive impact on the mobility performance of a flying UAV by reducing handover occurrences. It is also discussed, in which situations beamforming should translate into the uplink throughput gain.
Cellular networks will be one of the main pillars in the development of future vehicular communications. However, downlink (DL) and uplink (UL) channels must be improved to cope with the required reliability and high throughput of the coming vehicular use cases. Vehicle side solutions which benefit from the high antenna gains could improve the performance of the UL channel whose coverage is limited by UL transmit power. In this paper we experimentally evaluate the performance of a directional antennas switching system based on live Long Term Evolution (LTE) measurements. A total of more than 150 km have been driven comprising different radio propagation scenarios. The results show considerable improvements of Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), together with a reduction of handovers specially in scenarios with high Line-Of-Sight probability. Additionally, it has been found that the UL throughput does not improve with the increase of antenna gain probably due to the UL Power Control mechanism used in LTE.
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