Software efficient implementation of GMSK modem for an automatic identification system transceiver

A software implementation of a GMSK modem for maritime safety applications is proposed. The implementation targets a low cost 16 bit fixed point DSP architecture. Alternative architectures for the modulator and demodulator have been investigated and an optimal I/Q-based configuration was chosen. Several optimizations have been carried out in order to respect the limitations imposed by the fixed point DSP platform while satisfying the real time operation requirement. A hardware implementation is presented and validation tests show that the proposed software modem meets the system specifications in terms of communication data rates.