Design And Implementation Of Wireless Chaotic Digital Communication System

Chaotic motion is a kind of deterministic pseudo-random process, which appears in the non-linear system. It is bounded, acyclic, convergent, sensitive to initial value. Moreover, the dynamic properties of chaotic signal such as ergodicity, aperiodic, uncorrelated, broadband and noise-like prove that chaotic signal is useful for communication.As a new development direction of secure communication, chaotic secure communication has very good application prospects. Recently, many schemes of chaotic secure communication are reported in both domestic and foreign literature, which are based on separate analogy circuit device to generate continuous chaotic signal. However, with the development of digital signal processing technology, the research and application of chaotic system become digital. The reports of generating chaotic signal with modern digital device and application of digital chaotic secure communication system are more and more. With the properties of high logical density, strong commonality, random programmable, short development time, can be repeated revision, digital device overcomes the shortcomings of the analogy device, such as the parameters can't accurate adjustment, performance vulnerable to environmental factors. The digital device brings great convenience for the research of chaotic system.At present, many digital chaotic secure communication are based on the cable channels. Cable channel is close to ideal channel, and the synchronization of chaotic systems is relatively easy during transmission. The speech chaotic secure communication system is based on wireless channels in this paper. It is more convenient than the system based on cable channels, but influenced by outside noise. As an attempt, micro power,short distance,high speed wireless transmission chip nrF24L01 is chosen; The simple Lorenz chaotic system,not the complex multi-scroll or the multi-wing chaotic system, is used to encrypt the speech; And the encryption way is relatively simple chaos masking.Firstly, this paper introduced the research background and meaning of the chaotic secure communication. After explaining some basic theories and concepts of chaos and secure communication, the method to generate chaotic attractor on DSP platform is expounded in detail. The Euler algorithm, which is used to discretize Lorenz chaotic system, is also introduced. According to drive-response synchoronous principle, the synchronization of drive system and response system is implemented on the same ICETEK-VC5509-A development board; Then, the wireless transmission of speech signal between two development boards and the synchronization of sending system and receiving system during wireless transmission are both implemented Based on this, the speech signal is added to the chaotic signal. According to the drive-corresponding synchronous principle, a real-time wireless speech chaotic secure communication system has been implemented finally.