Study Of The Multiuser Detection And Signal To Interference Ratio Estimation In Satellite CDMA Systems

This dissertation studies the multiuser detection (MUD) techniques for asynchronous CDMA systems with convolutional codes, under the application background of a certain national engineering model item. It consists of four main parts:Based on the analysis of the single-user detection performance effect of multiple access interference (MAI) and the compare of several methods of MAI suppression, the essential to use MUD for MAI suppression is deduced.The principle of objective function-based MUD (0FMUD) and Symbol-level parallel interference cancellation (SPIC) are introduced In the second part. The performances of MMSE, Decorrelating Detector, OFMUD, PIC and SPIC in asynchronous DS-CDMA system are compared by simulation. It also compares the complexity of these algorithms and is deduced that the OFMUD and SPIC have low complexity and superior performance.The third part focus on the application of OFMUD and PIC in convolutional coded asynchronous DS-CDMA systems, A upswing algorithm which called objective function-based parallel interference cancellation is proposed based on the excellence of OFMUD and SPIC, the algorithm flow is also illuminated in detail. The improvements of implement complexity and BER performance compared with other MUDs discussed in this dissertation are proved by analysis and simulation.At last, a comparison of the performance of three SIR estimation techniques with the phase error has deduced. The result of simulation can give advice to the selection of SIR estimation algorithms in power control.