Adaptive Modulation-Coding Scheme for Link Adaptation in Aeronautical Mobile Airport Communications Systems (Aeromacs)

The unpredictability caused by random fluctuations of the airport radio channel characteristics, makes the standard approach of using a single modulation scheme that represents an optimum choice under various conditions on an airport surface environment, unrealistic. Same observation maybe made in regards to choosing a channel coding technique. The IEEE 802.16-2009 standard supports a variety of modulation formats and coding schemes. The essence of adaptive modulation coding (AMC) is the selection of appropriate modulation and coding combination to confront the propagation conditions of the airport channel. In this tutorial article, the AeroMACS mandatory modulation schemes, consisting of three square M-ary Quadrature Amplitude Modulation, are characterized. Channel coding process and the mandatory forward error correction scheme, a tail-biting non-systematic non-recursive convolutional code, are briefly described. AMC is the methodology of link adaptation in AeroMACS systems. The role of AMC and link adaptation in AeroMACS networks is in achieving high spectral efficiency while maintaining received signal reliability at an acceptable level, as the airport channel changes in time and frequency. Channel condition information is acquired from the channel quality feedback indicator. AeroMACS standard allows for seven combinations of modulation and coding schemes. The downlink data rate can dynamically change from 0.53 to 14.26 Mbits/s, as the airport channel conditions change.