【作者】 李卫卫；

【导师】 肖丽萍；

【作者基本信息】 燕山大学 ， 通信与信息系统， 2011， 硕士

【摘要】 近似同步码分多址(AS-CDMA)系统,其同步误差可根据需要控制在一个或几个码片周期之内。于是人们只要求扩频序列在同步误差范围内具有或接近理想相关特性。ZCZ序列恰能满足这一特性。使用性能良好的ZCZ序列,可以降低甚至消除多径干扰和多址干扰(MAI)。但是,由于ZCZ序列的设计受到许多条件的限制,目前它的寻找还存在一定的困难。ZCZ序列偶作为ZCZ序列的扩展,用于AS-CDMA系统中的扩频序列,可以获得更多数量的地址码。首先,本文提出了ZCZ序列偶集及大容量ZCZ序列偶集的构造方法。通过对最佳序列偶进行不同的移位,再与一定阶数的酉矩阵进行相关积运算,构造出了近似最优及最优两类ZCZ序列偶集;通过对已有的ZCZ序列偶集进行适当的移位再与相应的酉矩阵进行相关积运算,构造出了更大容量和更长零相关区的ZCZ序列偶集。其次,通过对正交矩阵偶进行移位、交织运算,再进行n次递归,构造出ZCZ序列偶集;通过对已知的ZCZ序列偶集进行移位、交织运算,再进行n次递归,构造出新的大容量ZCZ序列偶集。最后,本文还提出了一种扩大ZCZ序列偶集零相关区宽度的构造方法,对已知ZCZ序列偶集进行交织运算,再通过m次递归构造,在保持序列偶数目M不变的条件下,序列偶的零相关区宽度和长度都变成了原序列偶的M m倍。上述方法适用于二元、三元、四相及多相情况。构造出的ZCZ序列偶集性能优良,在同步误差允许的范围内,能够满足多用户AS-CDMA系统的要求。更多还原

【Abstract】 In the Approximately-synchronized code-division multiple-access (AS-CDMA) system, the synchronization error can be controlled in a few cycles within the chip. So people only requires spreading sequence in the synchronization error range (such as one or chip period) associated with or close to the ideal characteristics. ZCZ sequences satisfy this characteristic. ZCZ sequences with good performance, can reduce or eliminate multipath interference and multiple access interference (MAI). However, the ZCZ sequence design by many conditions, there are still some difficulties to look for them. ZCZ sequence pairs as the expansion of ZCZ sequence , as the AS-CDMA system of spread spectrum sequence can get more number of address code.First of all, in this paper, new methods for constructing set of ZCZ sequence pairs and ZCZ sequence pairs with large family size are proposed. First, almost optimal or optimal ZCZ sequence pairs set can be generated from the correlation product of unitary matrix and perfect sequence pairs with difference shift operation. Second, a new method for constructing ZCZ sequence pairs set with larger family size and longer zero correlation zone from a known one is presented.Secondly, a ZCZ sequence pairs set can be generated form orthogonal matrix pair with different shift, interleaved operation and n times recursive constructions; A new method for constructing ZCZ sequence pairs set with large family size from a known one is presented.Finally, in this paper, a new method for constructing ZCZ sequence pairs set with large zero correlation zone from a known one is presented, new ZCZ sequence pairs set can be generated from the original one with interleaved operation. The zero correlation zone of ZCZ sequence pairs set is M mtimes than the known one by m times recursive constructions with the new method.In addition, The methods are suitable for binary, ternary, four-phase and multiphase conditions. And the new ZCZ sequence pairs set has excellent performance that can satisfy Multi-users of AS-CDMA system.更多还原