Coherent Viterbi and threshold demodulators for pulse-driven GMSK signals

Abstract

Pulse-driven Gaussian minimum shift keying (PDGMSK) was introduced to facilitate a trade between bandwidth efficiency and receiver complexity when using the classical GMSK waveform. The waveform was purposely devised to converge, as the data rate decreases, to SDPSK or DPSK without expanding the absolute bandwidth. This paper studies the optimal coherent demodulation of the PDGMSK waveform, and provides simulation results of a near-optimal Viterbi demodulator and a low-complexity threshold demodulator in both single and multiple carrier settings. Trade-off among the signal-to-noise ratio (SNR), adjacent channel interference (ACI) level and carrier frequency spacing is also provided.