A Robust Demodulator for OQPSK–DSSS System

Abstract

IEEE802.15.4 standard has quickly become a benchmark in the era of Internet of things. The mandatory mode of 2.4 GHz physical layer of IEEE802.15.4 standard employs offset quadrature phase shift keying (OQPSK) modulation with direct sequence spread spectrum (DSSS). The performance of conventional differential demodulator is not satisfactory. The coherent demodulator is vulnerable to initial phase mismatch or frequency offset. In this paper, we propose a new non-coherent demodulator for the OQPSK---DSSS system. The proposed demodulator is robust against initial phase mismatch and frequency offset. At $$-$$ - 1.3 dB SNR in additive white Gaussian noise channel, the proposed demodulator achieves the target sensitivity at 1 % packet error rate. Simulation results demonstrate the effectiveness and robustness of the proposed demodulator.