Study On Non-linear And Adaptive Multiuser Detection Techniques

For the increasing density of multiplexing, the conventional single-user detector becomes less able to meet the demands. On the other hand, since the technology of Multiuser Detection was applied in Third Generation of Cellular Telephony successfully, it has been attracting an increasing number of researchers. In addition, for the condition of the increasingly scarce spectrum resource, multiuser detection becomes more popular in many other wireless communication fields as an effective technology for mitigating multi-access interference accompany with the multiplexing. However, the majority of the researches are focused on the Linear Modulation case at present.In this paper, the application of multiuser detection in CDMA system is discussed. For short code and long code CDMA system in fading channel, the multiuser system models are built respectively. And through the calculation and analysis the design of the multiuser detector is completed. In the discussion about the short code CDMA system, this paper gives the solution of the general model and two representative specific models. For the long code CDMA system, after the establishment of the system signal model, based on the actual application scenarios, the noise environment of the system is adequately modeled. Aiming at the discommodity of the traditional long code CDMA systems multiuser detection in posteriori estimation, the Bayes detector and Monte Carlo method combined detection scheme based on Markov chain and the Monte Carlo method is proposed.Subsequently, according to the analysis of the current research, in order to increase the channel capacity and spectral efficiency of Nonlinear Modulation, a study on multiuser detection in Nonlinear Modulation case is conducted. Specifically, M-PSK is chosen to be the elementary modulation mode in this paper. Based on it, the general approach to the problem is introduced through an overall analysis using Hypothesis Testing theory and Maximum a Posteriori criterion. Moreover, the performance of the detector is analyzed theoretically.In the end, for a more intuitive knowledge of the performance of the detectors, in addition to the theoretic deductions, consistent results from simulation experiments conducted on each detector are obtained.