A novel QAM-DCSK secure communication system

Differential Chaos Shift Keying (DCSK) employs noncoherent demodulation technology and it´s unnecessary for the receiver to generate synchronous chaotic signals at the receiving end. The structure of DCSK is simple and has good anti-noise performance. However, the security performance of DCSK is not enough, and it is easier to be cracked. For the above problems, a novel QAM-DCSK system was proposed in this paper. The system combines the advantages of Quadrature Amplitude Modulation (QAM) and DCSK. The information is scattered and transmitted in two orthogonal channels, thus the security performance can be greatly enhanced. At the same time, the good performance of the old one is also remained. The theoretical analysis was deeply carried out for this system. The relationship among Bit Error Ratio (BER), the frequency spread factor M and E_b/N₀ was also deeply studied. It was finally applied in an image transmission system as an example. Compared with the old one, the simulation results indicated that the performance of BER and security were greatly improved. Therefore, it has great significance in the practical application.