Direct Sequence Spread Spectrum Signal Detection And Its Security Analysis

The direct sequence spread spectrum technology has been used widely in both military and commercial communication. The advantages of spread spectrum communication are as follows: low probability of intercept, good anti-fading and anti-multi-path interference capability, so it is very important for communication systems. For the different application conditions, the designer of the communication system should adjust the requirement of the system's security and the reliability. And then, it can be found the balance of the system security and the reliability, and also good performance. In this dissertation the acquisition the PN code technology for spread spectrum communication systems is analysed. By introducing the principle of spread spectrum communication methods and performances of acquisition are analysed. A practical acquisition scheme is given. And both the theoretical analysis and experimental results indicate that the adopted analysis method and the supposed synchronization scheme are feasible.In Chapter 2,the signal model of DS system is built, some key technologies, such as the PN code detection, the PN code tracking, the detection probability of the DS signal were analyzed and computed in different conditions.A scheme about quick symbol synchronization technique of DS/FH digital burst communication is proposed in Chapter 3. The scheme points to actual features of DS/FH communication signal; propose a scheme of the biggest judgement for the multi-channel parallel detection. Based on this scheme and implementation by FPGA, the measurement results were also showed.The LPI system and the security are analysed in Chapter 4. The design of a communication link to have low probability of interceptor capability is predicated on the requirement for it should be operated in a hostile environment wherein the enemy tries to detect the presence of the communicator's transmission. The communicator should minimize the power as low as possible. The detection probability of the LPI system is very low. Later a few of anti-intercept capability spread spectrum signals in LPI signals, surveillance intercept possibility and some concerned basis technologies are also researched.The technology of CCSK spread spectrum communication is introduced in Chapter 5, and its application in security comnication are investigated.The whole paper is summarized and the expectations for following work are given in Chapter 6.