| The CDMA technique has been already used extensively by military in the research on anti-interference communication. In November 1989, the spot experiments of Qualcomm company in United States certificated that the capacity of the CDMA mobile communication system was twenty twice of the AMPS capacity theoretically. For the excited result, the CDMA technique became a hotspot object rapidly in the world. The development of the CDMA technique is not late in China, and there have been lots of technique backlogs in the long-term research by the military. In 1993, the research on CDMA technique was included in the 863 Plans in our country.Now, wireless mobile communication is developing rapidly, and along with the increment of mobile users and various high-speed services, the communication system must be able to provide big capacity, high speed rate and reliability service.The research on new mobile communication system has already become a hotspot of the communication research. In the scheme of the B3G communication system, multi-carrier CDMA is the focus of research. Multi-carrier CDMA is a new mobile broad-band communication system, which is combination of CDMA and OFDM. It's a new multi-carrier modulation technology which has the advantages of high spectra-efficiency and resisting on multi-delay. It introduces the three main modes of multi-carrier CDMA in this dissertation. They are MC-CDMA, MC-DS-CDMA and MT-CDMA. I select MC-CDMA as my main researching object, analyze its structure and design parameter detailedly. In the same time, I create the simulation model.Receiver of MC-CDMA system is to combine all received signals on different carriers and detect the transmitting data. The combining method is very important to the system and must be selected according to the real instance. Because of the difference of downlink and uplink, the selected combining method in them is quite different. There are main four combining methods in the downlink, which are EGC, MRC, ORC, and MMSEC. This dissertation will mainly research on simulation of the combining methods and analyzing their characters. |
