Interference Cancellation Multiuser Detection Technology For CDMA Mobile Communication

The paper totally describes today the multi-user detection's development state, deeply researches the linear and nonlinear multi-user detection algorithms, and chooses the lower complicated and easier realized algorithms to be research goal, which are interference canceller algorithms. According the default of successive\parallel adaptive interference canceller, It is proposed the adaptive and blind adaptive improved algorithms, and the same time, used the improved blind adaptive parallel interference canceller to high speed channel. Basing on the aim which describes above, the paper mainly does four aspect jobs as follows:Firstly, it is compared the recently six multi-user detection algorithms in code division multiple access mobile communication system, which are conventional matched filter, optimal detection, decorrelating detection, minimum mean squared error detection, successive interference canceller and parallel interference canceller. At the same tiem, it is analysed their advantage and disadvantage and chose the successive/parallel interference canceller as the goal of the paper.Secondly, as successive interference canceller has the error cumulate default, and the LMS-based adaptive successive interference canceller has a long time to convergence, it is proposed to use RLS-based adaptive successive interference canceller; but adaptive successive interference canceller could improve the feebleness user's performance and could not improve the strong user's performance, it is proposed blind adaptive successive interference canceller which is added LSCMA at the beginning of the adaptive successive interference canceller.Thirdly, as parallel interference canceller has the error cumulate default too, and the partial adaptive parallel interference canceller ignored the first stage which did not used LMS, it is proposed the new LMS-based adaptive parallel interference canceller, which uses the LMS both on the first stage and second stage; Considering new LMS-based adaptive parallel interference canceller which has the same default with LMS-based adaptive successive interference canceller , it is proposed RLS-based adaptive parallel interference canceller. But the RLS-parallel interference canceller's algorithm complexity is growing as the user number's growing, it is proposed the blind adaptive parallel interference canceller to improve the system performance.Lastly, when adaptive interference canceller verdicts a user, it much make taxis to residual users, and as the user number is growing the algorithm complexity is bigger, so the paper only uses blind adaptive parallel interference canceller to MC-CDMA system, and the simulate result shows, the blind adaptive parallel interference canceller could realize the better performance on avoiding multiple access interference and inter symbol interference.