Research On The Combination Of Multiuser Detection And Two-Dimensional Space-Time Processing In CDMA Communication System

Code-Division Multiple-Access (CDMA) technology has become the main technology studied in the Personal Communication Service(PCS) recently because it has lots of benefits, such as large system content, high voice quality , easy frequency scheme, low cost of the net making and so on .Direct Sequence-Code Divition Multiple Access (DS-CDMA) technology is achieved easily and used widely at present Its receiver capability is confined by two factors , one of which is the multiple access interference (MAI) which makes the capacity low , another of which is the near-far problem. Traditional receiver can not solve these questions, so the multiuser detection technology is proposed. But the computational complexity of the optimum multiuser detection, which can not be applied for the channel where are too many users, is too large, so the Sub-optimum Multiuser Detection is used in the practical systems.Because there are still some shortcomings in the Sub-optimum Multiuser Detection technology, that the combination of the Two-Dimensional Space-Time Processing and the Multiuser Detection can improve the capability of the receiver is expected. This article proposes two solutions to the question, one of which is the combination of the Space-Time MMSE Receiver and the Decorrelating Multiuser Detector, another of which is the combination of the Space-Time MLSE Receiver and the Decision-Feedback Detector. The results of the computer simulation can prove that the two solutions can improve the capacity of the receiver indeed.