Performance of multiuser communication system using phase coded linear chirp modulation
Arijit Roy, Harshal Bhalchandra Nemade, Ratnajit Bhattacharjee · 2017
Chirp spread spectrum (CSS) technique is capable of providing high processing gain, low power, robustness to multipath interference and immunity to Doppler frequency offset. The paper presents a new phase-coded modulation technique for CSS multiuser communication. The construction of a nth power chirp signal is explained and the design of the phase-coded linear chirp signal is presented in detail. The modulation scheme benefits from the merits of both chirp signal and pseudo noise (PN) codes: chirp signal is immune to Doppler frequency offset and cross-correlation among PN codes reduces multiple access interference. Another advantage is that low cost implementation of the proposed scheme is possible using passive devices such as surface acoustic wave (SAW) filters/correlators. A generic multiuser communication system model is presented 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 performance of a multiuser communication system using the proposed scheme is compared with that of a multiuser linear CSS system reported in literature. The effect of Doppler frequency offset on the system performance is also presented.