Research and Hardware Simulation of Multiuser Spread Spectrum Code Acquisition Based on FPGA
|School||Harbin Institute of Technology|
|Course||Information and Communication Engineering|
|Keywords||DS-SS Multi-user PN sequence acquisition FPGA|
Spread Spectrum Communication with the character of strong anti-jamming and well covered which can implement CDMA technique. Spread Spectrum technique is widely used in digital cell-phone mobile communication system,satellite mobile communication, inside wireless communication and future personal communication. In the Spread Spectrum system, Direct Sequence Code Division Multiple Access (DS-CDMA) system is the widest application spread system at present. DS-CDMA technique can implement asynchronous transmission of multimedia data operation, offer more system capacity than traditional Multi-address technique, restrain frequency selection decline in channel and offer Multi-access conveniently. This makes it as the decisive factor by application in future mobile communication system.Spectrum code acquisition is a stress research problem to DS-CDMA all through. In the Direct Sequence Spectrum system (DS-SS) with multiple users, Multiple Access Interference (MAI) will arise in spread spectrum signals of different users. This is one of the difficulties for Multi-user spread spectrum system. Making asynchronous CDMA system as Starting-point, this dissertation studies spread spectrum code acquisition in Multi-user DS-SS with five users.This dissertation expatiates on the theory of spread spectrum communication at first, then analyzes and compares the major direct sequence spread spectrum code acquisition ways at present. Facing to characteristics of the system and the problem of implementation, This dissertation selects a new structure of the acquisition, namely multi-delayed correlation acquisition. This structure is easy to achieve in the FPGA chips, and considers two factors of equipment complexity and acquisition time comprehensively. It improves the speed of acquisition satisfactorily in the case of complicating the hardware scale appropriately.And then, the dissertation performs soft simulation about the design of acquisition and verifies correlated algorithm using MATLAB. At the end, this dissertation gives an implementation to multi-delayed correlation acquisition by applying the High-speed hardware description language, basing on Altera’s FPGA, and performs system hardware simulation in Modelsim. The system is programmed with blocking design, and it is convenient to change the order of quantified data, correlating accumulator, spread spectrum codes of users and the length of each code. It is useful to the system’s expansion in the future and multi-use for similar spread spectrum system, showing good flexible and compatible.