Phase coded nonlinear chirp modulation in multiuser communication systems
Arijit Roy, Harshal Bhalchandra Nemade, Ratnajit Bhattacharjee · 2017
Chirp spread spectrum (CSS) technique has the ability to provide high processing gain, low power, robustness to multipath interference and immunity to Doppler frequency offset. This paper presents a new phase-coded nonlinear chirp modulation technique for CSS multiuser communication. The design of the phase-coded nonlinear chirp signal is presented in detail. The modulation scheme has the merits of both nonlinear chirp signal and pseudo noise (PN) codes, as chirp signal is immune to Doppler frequency offset and low cross-correlation between PN codes restricts multiple access interference. Moreover low cost implementation of the proposed scheme is possible using surface acoustic wave filters/correlators. Generic multiuser communication system model and its bit error rate (BER) performance is analyzed in additive white Gaussian noise (AWGN) channel and Rayleigh fading channel as a function of number of users. The effect of Doppler frequency offset on the system performance is also discussed.