Anti-interception Waveform Design Of Communication Signal Based On Frequency Shift Chirp Modulation

Frequency shift chirp modulation(FSCM)has become a powerful solution in the area of internet of things(Io T)due to its long-distance and low-power consumption characteristics.At the same time,it has attracted the attention of military Io T due to the chirp spread spectrum technology originating from radar scenes.However,the simple modulation and insufficient security performance have become the main bottlenecks restricting the development of FSCM in high-security application scenarios.Therefore,the anti-interception waveform design of communication signals based on FSCM is studied in this paper,aiming to improve the anti-interception performance of this modulation method while ensure the normal communication of legal communication transceivers.Firstly,the modulation and demodulation basis and time-frequency domain characteristics of conventional FSCM signals are analyzed.In addition,the influence of different sampling frequencies and synchronization error of transceivers on demodulation performance is studied,and the autocorrelation performance of FSCM signal is analyzed.These studies lay a theoretical foundation for establishing anti-interception evaluation system and designing anti-interception waveform.Secondly,the detection probability of signal existence,the estimation accuracy of instantaneous frequency change rate and the bit error rate(BER)of demodulation are selected as the evaluation indexes at different interception levels,so as to establish an anti-interception evaluation system suitable for FSCM signals.In addition,the concept of constellation-like map is also proposed to analyze the modulation and demodulation changes.The simulation results show that the traditional FSCM signal has the advantage of anti-interception.However,in order to further enhance the communication security,the latter two interception layers,which are easy to improve the performance,are selected as the basis for waveform design.Then,according to the physical layer characteristics of FSCM,the anti-interception waveform based on cyclic shift value transform(CSVT)is designed.The scheme combines the secret key extraction method based on received signal strength indication and the secret key sharing method based on Chinese remainder theorem.The simulation results show that no matter whether there is synchronization error,the proposed scheme can effectively avoid interception at the third level without causing the performance loss of the legal receiver.In addition,this scheme does not increase additional hardware equipment and transceiver power consumption.Finally,an anti-interception waveform based on time-frequency division and scrambling(TFDS)is designed for the inherent defects of CSVT.Based on the timedomain shaping window algorithm,the scheme combines pseudo-random sequence generation technology and Chinese remainder theorem.The simulation results show that the proposed scheme can effectively improve the anti-interception performance at the second and third interception levels compared with the traditional FSCM without security design.This scheme is more flexible than the previous one,which not only reduces the negotiation process but also improves the anti-interception performance.