DSSS Differential GMSK With Space-Time Modulation for Robust Mobile Data Links
A new modulation scheme combing GMSK with Direct-Sequence Spread Spectrum (DSSS) and differential modulation is proposed in this paper, which is named DS-DGMSK. The demodulation can achieve BER performance comparable to DBPSK while the bandwidth efficiency and power efficiency are higher thanks to GMSK. By combining with spread spectrum and differential demodulation, the scheme is robust at low SINR and high moving speed without accurate carrier frequency recovery. It can be further enhanced by Differential Space-Time Modulation (DSTM) giving transmit diversity which further improves robustness. The proposed modulation is suitable for low-bit-rate mobile data link which requires high robustness, low complexity and nonlinear power amplifier which is low-cost and less power-consuming.