GMSK Viterbi Demodulation for Satellite-AIS

This paper presents a novel Viterbi method based on one-bit differential detection for Gaussian minimum shift keying (GMSK) used in the satellite based automatic identification system (AIS), which is easy to achieve in hardware. Because of the inherent intersymbol interference (ISI) of the GMSK, the bit error rate (BER) of hard decision based demodulation methods is always seriously exacerbated by Gaussian white noise especially under a small BT value. Correlation based traditional Viterbi method for GMSK will consume a mass of multiplier and adder resources and is not suitable for the hardware achievement. A phase rotation based differential Viterbi method is proposed in this paper, which just consumes few calculation resources and has better BER performance comparing with the hard decision method. The corresponding comparable result of the BER is also shown.