Optimum detection of differentially-encoded 8-ary phaseshift keying in a dispersive aeronautical channel: new results & approximations

Several different waveforms have been proposed for use in aeronautical data links in the next-generation National Airspace System for transmission of navigation, surveillance; and communications information. Among these are those in the Very High Frequency Digital Link (VDL) family. Reliability of the links, expressed in terms of the assurance of a very low probability of message error, is crucial. Because of these strict integrity requirements, optimal receiver detection (demodulation) schemes are of interest. The performance of the proposed waveforms in multipath channels has not been thoroughly studied to date, and this work extends some of our initial work on this topic (2001) to the VDL (modes 2 & 3) modulation scheme: differential 8PSK. The previous work has been based upon multiple symbol differential detection (MSDD), long known to improve the performance of differentially-encoded PSK on the additive white Gaussian noise channel. In this new work, we extend our initial results on binary PSK to the 8-ary case, and we also explore simplified versions of the receiver more suitable for implementation. Performance of the new detectors is compared via simulations.