Research On The Design Of Spread Spectrum Sequence And Code Synchronization Based On TT&C System

In modern communication, direct sequence spread Spectrum communications was widely used in the fields of telemetering and telecontrol systems, because of low interception probability, its high noise resistance and good security. This thesis is focused on research on theory and system characteristics of direct sequence spread spectrum communications and code synchronization, as well as related simulation.The thesis first introduces theory basis of spread spectrum, essential principle and construction of system. In the third chapter, the design of PN sequence is investigated. Also the performance is analyzed and how to make optimal selection is given. A universal model for generating arbitary length and arbitary quantity M sequences is given in the thesis. The generation algorithm and the performance of LAS codes are investigated; In the fourth chapter, a series of algorithm are proposed which can be usually used in DSSS communication systems, including the PN code acquisition algorithm and the PN code tracking algorithm. A new PN code acquisition method is studied using cross correlation of auxiliary signals with PN sequence. Comparing the traditional way, the proposed system provides an improved the performance under normal operating conditions. An improved method of the preamble acquisition is proposed based on digital matched filter in the fifth chapter. It not only considers the effect of frequency error and data modulation, but also realizes code synchronization and frame synchronization at the same time.All these research work will give a valuable reference to the design of the new communication systems.