On multiuser MIMO capacity benefits in air-to-ground communication for air traffic management

In this paper, we focus on communication from airplanes to air traffic control (ATC) towers at airports, employing multiple antennas at the ATC. The whole air-to-ground communication system can then be modeled as a MIMO MAC channel with mobile users. The main aim is to demonstrate that multiuser MIMO systems can be useful for achieving spectrally efficient aeronautical communications, to quantify the achievable capacity gains when using such systems, and to show that they can be implemented by deploying multiple antennas at reasonable inter-antenna distances at the ATC. In particular, we analyze the issue of antenna separation of a uniform linear array (ULA) at the ATC, for the case of line of sight (LoS) air-to-ground channels. It turns out that at high frequency (1 GHz), the use of large ULAs is indeed possible since the maximum (ergodic) capacity gain is achieved already for antenna separation on the order of a few centimeters. We also observe the system performance in Ricean fading channels. The performance is evaluated with respect to ergodic multiuser capacity throughout.