An efficient FPGA implementation of GMSK (BT=0.3) transceiver with non coherent sequence detection for tactical V/UHF waveforms

Abstract

The paper presents FPGA implementation of GMSK (BT = 0.3) transceiver that uses a non-coherent sequence detection scheme. The receiver has a fairly low complexity 4-state trellis. Additional complexity reduction has been done through novel optimizations in phase state update, metric update and non-coherent recursive phase reference calculations. The receiver outperforms the non-coherent binary cross-correlator demodulator [4] by more than 4 dB in AWGN environment. It is robust against moderate carrier frequency offset variations up to 4% of symbol rate with marginal performance degradation up to 1.5 dB.