Aerial base station

[10][3] In the early 2000s, both the costs and the size reduced, thus, UAVs civilian and commercial applications started to be predominant, allowing a myriad of uses in the wireless communications field with the support of the existing network architecture, such as package delivery and traffic control in smart city context, or precision agriculture and terrain inspection in Industry 4.0.

Lightweight, Commercial BSs are suitable to be mounted on UAVs with a moderate payload allowing a wide range of applications:[2][3][4][6] Models of such an innovative technology are provided by Qualcomm[12] and AT&T that have experimented the deployment of ABSs for enabling wide-scale wireless communications.

Also, projects such as Facebook Aquila, cell-on-wheels and wings (COW-W), Google SKYBENDER, Nokia F-Cell,[13] Huawei Digital Sky[14] are aimed for testing the benefits of ABS services.

[17] The International Civil Aviation Organization (ICAO) is concerned with the Asia guideline for the regulation and safe operation of unmanned aircraft systems.

[3] Although 3GPP is still concentrating its efforts on cellular-connected UAVs standardization,[20] there are different proposed wireless architectures that involve flying systems carrying an intelligent router.

The CNPC link is also used for delivering information about the network configuration, which determines time and frequency resource allocation, and to collect some information about the ABSs's flight data (such as GPS, relative elevation angle, and flight speed), residual energy, and performances about the provide connectivity (such as average bit error rate, received and transmitted power).

The frequency bandwidths allocated for this link are L-bands and C-bands since they do not suffer severe path loss, allowing a high reliability and low delay communications.

Since these latter are mainly dominated by LoS component, the utilization of millimeter-wave bandwidth is a prominent solution for guaranteeing the high capacity requirement.

[1][7][8][9] The problem of finding an optimum location and/or path planning is more challenging for ABSs compared to the conventional terrestrial BSs.

For instance, in case of cellular coverage ABSs-supported, the solution is to deploy static ABS that hovers above the centre of the area to be covered.

In case of real time applications or moving devices, it is more intuitive to employ more than one ABSs to cooperatively achieve low delay and high reliability communications.