Adaptive DSP-based MFSK modems for HF aeromobile channels

An adaptive digital-signal-processing (DSP)-based MFSK modem using the PICCOLO modulation scheme has been developed, primarily as a research platform for the investigation of adaptive HF radio modems. The authors describe several important design features of the implementation, including a novel data-derived synchronization scheme. The modem exhibits a far greater degree of responsiveness to both user requirements and channel state than previous implementations. Of particular interest are the efficient memory shadowing technique used in the tone synthesis, the ability to vary the number of samples/symbol, the frequency offset correction method, and the modulation-derived synchronization (MDS) embedded synchronization technique which eliminates the need for any specific synchronization overheads. The use of the model in a semiorthogonal MFSK mode is also discussed