Research Of Acquisition Technology In DS/CDMA Communication System

With the development of software radio in recent years, the CDMA spread spectrum communication technology has become the mainstream technology in the wireless communication field with good addressing capability, anti-interference performance and security function. DS/CDMA system is the spread spectrum system currently that has the most mature technology and has been used most. Spread spectrum code acquisition is a key step for reliable communication in DSSS system. Therefore, how to realize the low delay, low complexity and high reliability acquisition method becomes a hot research issue. The paper makes a discussion and study on acquisition method in DSSS system based on the constructed CDMA audio conference system hardware platform.The paper introduces the theory and classification of CDMA spread spectrum communication system at first and takes DSSS system as the research focus. Then the paper analyzes and contrasts the commonly used code acquisition methods deeply. Then the paper summarizes the CDMA audio conference system based on FPGA from two aspects of hardware and architecture. According to the performance requirement of CDMA audio conference system, the paper adopts serial and parallel correlation acquisition method as the acquisition scheme. The acquisition scheme provides a balance between two factors like hardware complexity and acquisition time, and reduces the acquisition time by properly increasing hardware resources. Then the paper uses simulation tool Matlab to verify the correlation property of spread spectrum code and simulate the acquisition algorithm. On this basis, the acquisition scheme is designed through modules which are realized by the hardware description language and has hardware simulation through ModelSim. Finally, the paper gives a hardware test and analyzes the acquisition result and the use rate of hardware resources. Spread spectrum code generation circuit, acquisition circuit and threshold circuit of system adopt modularized design which contributes to modification, extension and portability of system later. At the same time, the system has low utilization rate of resources that reduces the hardware complexity and provides more resources for other modules.