Research And Implementation Of Multiple Access Interference Suppression Algorithm For Asynchronous CDMA

Direct sequence spread spectrum communication and CDMA system are important communication technologies in modern communication system.All users can occupy the same channel at the same time and use different spreading codes to distinguish different users.However,with the increase of users,the more serious the multiple access interference is,which limits the upper limit of users and the performance of CDMA system.In the general analysis,it is often considered that CDMA system is a synchronous system,but in practical application,there are still some systems which are asynchronous systems and may not have power control.Therefore,the research and implementation of asynchronous CDMA multiple access interference suppression is very necessary.In this paper,the serial interference cancellation system is studied and implemented.Firstly,the basic principle of asynchronous CDMA system and multiple access interference cancellation is studied.From the introduction of CMDA asynchronous communication system to the generation and theoretical analysis of multiple access interference,and analyzes the current mainstream methods of multiple access interference elimination,and finally chooses serial interference cancellation as the final implementation of this paper.Secondly,a practical system is designed for CDMA interference cancellation system.The system includes DSSS transmitter,DSSS receiver and serial interference cancellation.The design of serial interference cancellation is the focus of this paper,and the simulation of serial interference cancellation is carried out to verify the feasibility of serial interference cancellation in this system.Finally,this paper introduces how to implement the asynchronous CDMA interference cancellation system in FPGA.The hardware platform FPGA and RF agile transceiver ad9361 are introduced.Then,the FPGA implementation of asynchronous CDMA modulator and asynchronous CDMA demodulator are introduced.And the FPGA implementation of serial interference cancellation is introduced.