The Analysis And Implementation Of Rake Receiver Based On The Muti-Carrier Spreading Communication System

Because of the complexity of mobile environment, wireless signalis fading in the process of transmission and receiving. Especially in the high frequency band wireless communication, muti-path fading is the most serious interference. Through diversity receiving, Rake receiver is very effective in resisting muti-path fading of CDMA system. As a new multi-access scheme, multi-carrier CDMA fully utilizes the optimum frequency utilization of OFDM as well as the multi-access capability and frequency diversity of CDMA. Those characteristics make MC-CDMA the most promising candidate of future 4G communication system.In this paper, the theory and designing method of Rake receiver in the muti-tone spreading communication is being discussed and it being implemented with FPGA.The history of mobile communication system, as well as OFDM and CDMA principles are first presented in this paper, three types of OFDM and CDMA combined systems (MC-DS-CDMA, MT-CDMA, MC-CDMA), their principles and system models are described. Next, the thesis analyzes the theory and importance of Rake receiver. Because multipath signal contains useful Information, the receiver can change SNR by receiving it. Rake receiver is based on receiving multipath signal by multireceiver. Based on this, the thesis introduces a project of MT-DS-CDMA system and analyzes the designing principles of Rake receiver in this project, then it presentes the simulation result of the system's bits error rate with Maximal rate combination method. Based on the discussion above we use Verilog HDL to implement the function of the FPGA part on the hardware board. After testing the system some related simulation results and test results are presented.The simulation results presentes that the BER decreases when the number of receiving multipath signal increases. It shows that the performance of the Rake receiver is very good in resisting muti-path fading. Especially in MT-DS-CDMA system, the implementation of diversity receiving is much easier. And the result and performance of the implementation with FPGA is same as the simulation, which has much practical value.