【作者】 黎超；

【导师】 唐小虎；

【作者基本信息】 西南交通大学 ， 计算机应用技术， 2006， 硕士

【摘要】 本文讨论了广义LS(GLS)码在QS-CDMA系统中的优化问题,大区域同步CDMA(LAS-CDMA)的优化问题,以及提出了一种基于互补序列集的广义多不相关基LS(GMLS)码的设计方法。 基于LS码的广义描述,我们给出了优选GLS码的准则和方法。GLS码由不相关对的组合方式和对应的哈达码矩阵唯一确定。我们首先推导出了QS-CDMA系统同步误差在对称区间上均匀分布的平均情况和最坏情况下系统误码率(BER)的表达式。然后给出了使QS-CDMA的BER值达最小的GLS码字搜索算法。计算和仿真结果表明优选出的GLS码能显著地提高QS-CDMA系统的性能。 优选出的GLS码用到LAS-CDMA系统中,同样可以有效地减小系统的BER。另一方面由于GLS码相对于LS码字参数选择上的灵活性,分析系统的容量后发现GLS码可以给系统设计带来方便,甚至在某些情况下可以提高系统的容量。我们进一步分析了LAS-CDMA系统在组网上的主要问题,提出了给每个小区不同时间的无线子帧分配不同的LA码来实现动态组网的方法。分析表明,这种动态组网的方法不仅实现简单,而且能有效地克服LAS-CDMA在组网中的困难,显著地提高了系统在多小区条件下的组网性能。 从互补序列集出发,我们通过类比GLS码的构造方法,提出了一种新的GMLS码字的设计方法。新的码字由具有M个不相关基的组合和M阶哈达码矩阵“相乘”而得到。新的码字由GLS码的两部分分开做相关变为P个部分分开做相关。新的码字具有理想的自相关,互相关存在一定的ZCZ区,并且在整个相关区间上相关值副峰的最大值为主峰的1/M。在新的码字中间插入一定数量的0后,便生成了一种几乎达到码界的几乎二元的非周期(周期、奇周期)的ZCZ序列集。更多还原

【Abstract】 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.更多还原