Research on CS-CSS Modulation System Based on Chirp Signal

Abstract

In recent years, with the development of Internet of Things (IoT) technology, many things around us are closely connected through network communication. In this paper, a Cyclic Shift Chirp Spread Spectrum (CS-CSS) technique is proposed by combining the reference coefficients and design indexes defined by the Long Range (LoRa) protocol. The technology combines Chirp spread spectrum (CSS) with Cyclic Code Shift Keying (CCSK) coding spread spectrum, maps the input data on Cyclic Shift Factor (CSF), and solves the corresponding Cyclic Shift Factor by FFT at the receiver. Compared with Chirp-BOK system, it has better Bit Error Rate(BER) performance and stronger anti-interference ability. In terms of performance, compared with the parameters and indicators specified in LoRaIoT protocol, it can meet the requirements. Then, the experiment shows that compared with the Chirp-BOK system, the BER performance has more than 10dB gain when the Spread Factor (SF) is 7, and the modulation efficiency of the system wm also increase or decrease with the change. Finally, the synchronization scheme is studied and the algorithms for estimating time offset and frequency offset are designed. The experimental results show that the proposed algorithm has good performance. In this paper, some advantages and contributions based on the proposed technology are also described in view of many bottlenecks facing the IoT industry at the present stage, such as cost, power consumption, synchronization implementation, modulation efficiency and other issues.