Research And FPGA Design Of Multiuser Detection Algorithm Based On DCD Interation

With the arrival of the third generation mobile communication,the three mainstream of 3G technology take CDMA as the basis of their air interface.Under the situation of rapid growth in the communication capacity,the adverse impact caused by MAI inherent in CDMA system on existing system become very serious,there is urgent demand to solve the problem of MAI.In this background, multi-user detection causes extensive discussions and research,and have become a hot topic.Multiuser detection is relative in terms of signal user detection,its basic principle is no longer to treat other users' signals as the interfering signals but useful signals,and actively use the signatures of other users signals, amplitude, timing and delay information to demodulate the desired user signal, so that multipath and multiple access interference can be decreased dramatically, while minimize the negative impact of Near-far effect. As a key technology for solving the above problem,MUD has been paid close attention,theorists have been making unremitting efforts in order to reduce the complexity of multiuser detection algorithm.Various MUD algorithms proposed currently still have high complexity,and they are difficult in the real-time implementation on hardware,so the MUD is not yet entered the practical stage.But with the continuous evolvement of MUD technology,various MUD algorithms which have excellent performance with not quite high complexity were brought up continuously.The integration level and the ability of calculation of hardware advanced with the help of the vigorous of microelectronics,the MUD Detection will come to practice surpassing its theoretical phase and it will finally applied in BASE Station or terminals.This paper use the ingenious DCD algorithm for reference which was presented by a foreign scholar. Surrounding of DCD application in Multiuser Detection and its design on hardware,the thesis mainly accomplished the following works:First,briefly described the principle and characteristic of CDMA,especially the most widely used,DS-CDMA.First of all,it point due to the spreading code can not keep orthogonal strictly,then some measures were presented to solve the problem,Accordingly, the thesis drew the concept of MUD,then introduced the development of MUD technology,through the analysis of those existing algorithms indicating the pros and cons of them.Second,we treat the MUD as a combinatorial optimization problem,as a result,some optimization search algorithms can be applied in the field of MUD,Then the general CD(Coordinate Descent)method which belong to the line search method was deduced;we got the DCD algorithm,then the related DCD algorithms programs were written in MATLAB and build the MUD model based on DCD iteration,running the simulation programs,observe the change of the algorithm's performance when its three controlling parameters change,finally the curve of SNR vs BER were draw.At last,the real-valued DCD algorithms was extend to complex-valued DCD algorithms,making its applicability increased greatly.The hardware design of DCD algorithm in MUD is presented. The introduction of the FPGA development idea which is novel in recent years is applied in this design,the design process float-point simulating in MATLAB first,and got the most ideal curve of performance simulation,keeping track of the key variable simultaneously,observing the dynamic change of their scope,drawing the probability distribution of each data using statistical method,then determine the length of data and the location of their decimal point;thus processing fixed-point simulation in MATLAB and got the final data format of variable which can meet the performance demand,finally entered the FPGA design phase, moreover the thesis also describes a method using MATLAB to generate test vectors, and points out the measure that combined MATLAB with the online logical analyzer can be used as the final board level validation method.