Capacities of simplex and duplex VHF air/ground mobile radio communication systems employing cylindrical cells

Abstract

The channel capacities of simplex and duplex VHF air/ground (A/G) mobile radio communication systems employing cylindrical cells are compared considering co-channel and adjacent channel interferences criteria currently adopted by the International Civil Aviation Organization (ICAO) and the Federal Aviation Administration (FAA). According to ICAO recommendations, the co-channel interference source must be beyond the radio line-of-sight (RLOS) of the receiver. The FAA co-channel interference criterion requires a signal-to-interference ratio of at least 14 dB or beyond RLOS protection. Capacity depends mainly on the frequency reuse distance. In order to prevent air-to-air interference, simplex systems using the same frequency for air-to-ground and ground-to-air require a larger frequency reuse distance than duplex systems which do not require air-air interference since different frequency bands are used for uplink and downlink communications. A comparison is presented between the capacities of the two systems. It is shown that the capacity ratio of the two systems depends on the cell dimensions. It is concluded that the duplex system has more capacity than the simplex system for cells of large radii and small heights.