Coexistence of 5G Communication Systems With Radar Altimeters

With the growing demand for 5G, many countries have allocated additional spectrum above 3.7 GHz, potentially causing serious interference to radar altimeters operating at the 4.2–4.4 GHz band. Therefore, in this paper, a general mathematical model is proposed to estimate interference from 5G base stations to a radar altimeter which can be applied for aircraft, helicopters, unmanned aerial vehicles, satellites, and hot-air balloons. Using this model, the interference at the radar altimeter is evaluated in several environments such as rural, suburban, and urban. Two types of antennas are considered which are omnidirectional and multiple-input and multiple-output antennas (4-by-4, 8-by-8, and 16-by-16). Additionally, a power control-aided distance protection method is introduced to enable the coexistence of the 5G base stations and the radar altimeters. To validate the effectiveness of the proposed protection method, the Monte Carlo method is employed. Numerical results present the heights of the radar altimeter where the interference-to-noise ratio becomes higher than the interference protection threshold of −6 dB. In addition, it shows that the radar altimeter can coexist with the 5G base stations with the proposed protection scheme.