Optimized Study Of LS And LA Sequence Set In The QS-CDMA System

This thesis discussed a generalized loosely synchronized (GLS) code and its optimization in qusi-synchronized CDMA(QS-CDMA), investigated the optimiza -tion of the large area synchronized CDMA(LAS-CDMA), and proposed a generalized multi uncorrected mates LS(GMLS) code based on uncorrected complement sequence set.Based on the generalized description of LS code, we further gave the standard and method to hunt the optimized GLS code. GLS code can be constructed by the combination of uncorrelated pairs and the Hadamard Matrices. First the average and worst Bit error rate(BER) expression of QS-CDMA system was deduced, when the synchronous error is uniformly distributed within the symmetrical area. Second the algorithm to search GLS code minimizing the BER value of QS-CDMA was given. Computation and simulation reveal that the optimized GLS code can greatly improve the QS-CDMA system performance.The optimized GLS also can be used in the LAS-CDMA system, and the system BER can been reduced too, just as QS-CDMA situation. And in other ways, because of much more choices with the GLS code parameters, much more choices appeared to the system design, so that the system capacity can be increased in certain circumstances. The main problems of LAS-CDMA system in the multi-cell construction also were analysed, and a new method to dynamically assign LA codes for each cell with different wireless subframe was proposed. The analysis indicates that in multi-cell circumstances, our method implemented easily, can efficiently overcome the difficults, and extraordinarily enhance the LAS-CDMA system performance.Analogizing the GLS code construction, a new GMLS code was devised based on the uncorrected sequence set. The new codes can be derived from M uncorrected mates combination and the M-order Hadamard Matrix with "multiplication". And the new codes become P parts to make correlation comparing to 2 parts of GLS codes, respectively. The new codes have ideal auto correlation, and the corss correlation exists a certain length zero correlatonzone(ZCZ). Out of the ZCZ, the maximal correlation peak is 1/M of the main correlation peak. After padding some 0 strings in the new code, we can get an almost binary aperiodic(periodic or odd periodic) ZCZ sequence set,which almost reach the related mathematic bound.