Research On Blind Multi-user Detection Algorithm Of 3G System

Code division multiple access is the main multiple access technology of the third generation mobile communication system and the capacity is limited to multiple access interference and near-far effects. As a technical to inhibite interference, multi-user detection makes use of all users'informations and adopts some appropriate signal processing methods to achieve the arm of restoreing the desired user's information. Among algorithms, blind adaptive multi-user detection update data in accordance with the changeable input without training sequences. The advantage of this algorithm shall save spectrum resources and be highly efficient and widely practical.To optimize system performance, firstly this paper introduces two basic blind multiuser detection algorithms - least mean square and recursive least squares. Under the condition of the static or dynamic gaussian white noise, using Matlab the paper simulates EOE and SIR. Simulation results show RLS is better than LMS in aspects of detection reliability and resistance to interference. Secondly, LMS is efficient and easier to implement, but its convergence performance is limited to the step size factor. To solve this problem, paper proposes an improved algorithm-variable step size least mean square algorithm. Through the simulation, the improved algorithm accelerates the convergence rate and increases resistance to interference. Finally, the ability of the resistance to interference of RLS is stronger but its gain coefficient is a fixed value, lack of flexibility even lose the ability to track the data. This paper proposes an improved algorithm-variable gain coefficient recursive least squares algorithm. Under gaussian and rayleigh channel, simulate the original and improved algorithm. The comparison shows that improved algorithm improves the ability of tracking the changeable data.