Implementation of Adaptive OFDM for Aeronautical Channel

This paper presents the design and performance of an Adaptive Orthogonal Frequency Division Multiplexing (AOFDM) modulation system for aeronautical telemetry. This work takes advantage of the quasi-stationary behavior of aeronautical channels. Such channels dominate most aeronautical applications and justify special treatment. Our result shows that AOFDM increases the overall data transmission by enabling high data rates (6 bits/tone) for selective tones, simultaneously reducing unnecessary errors by avoiding tones degraded by the Channel. It also allows operation on poor channels with an 8dB signal to noise ratio (SNR). We also demonstrated the quasi-stationarity nature of the 2-ray aeronautical Channel and the feasibility of a backchannel at a low data rate. The AOFDM system learns the performance of each OFDM tone and adjusts the modulation to optimize the performance. Such a design demonstrates a significant enhancement of spectrum efficiency compared to current modulation schemes used.