Complexity reduction for continuous phase modulation using basis functions

A basis function expansion to reduce the demodulation complexity of continuous phase modulation (CPM) signals applicable for either coherent or non-coherent reception in tactical networks is presented. Results show that a signal space receiver based on B-splines approximates a wide variety of CPM signal sets with only a small number of basis functions and is particularly useful for spectrally efficient CPM waveforms.

I. Introduction

Continuous phase modulation is a desirable transmission format for narrowband tactical communications due to its spectral properties and constant envelope for power amplifier efficiencies. Detectors for CPM typically consist of a number of matched filters followed by some form of trellis based maximum likelihood (ML) detection. The overall complexity of this two stage detection is dependent on the number of matched filters used and the number of phase states. The former is related to the modulation memory, , and signal alphabet, , whereas the latter is related to and the modulation index, .