摘要
由于扩频通信具有节约频率资源，抗干扰性强，保密性好等特点，近20年中，CDMA通信系统得到了迅速地发展，成为当今通信发展的主流。而在CDMA通信系统中，地址码的选取极其重要。它决定着系统的容量，抗干扰性，接入和转换速度等性能指标。
在CDMA通信系统中，主要使用二元序列作为地址码。二元序列的研究已经较为广泛和深入，人们运用近世代数的理论，得到了一批性能优越的二元序列，如GMW序列，No序列，Bent序列等。虽然二元序列的各种构造方法有其各自的优点，但却共同存在着许多限制，如地址码数量过少，相关性能改善程度已趋近于零等，从而无法适应移动用户数量的不断增加且无法满足用户对通信质量不断提高的要求。为了突破这种限制，多相序列的研究已引起学者们的更多关注，其中Suehiro的一种多相序列构造方法较为典型，他在FH序列的基础上用矩阵论的方法构造出多相正交序列，使独立地址码的数量更多，相关性能更好。从而使CDMA通信系统地址码的研究有了一个广阔的前景。
本文将在该多相序列的构造理论基础上，研究多相序列的相关性能，并对其进行仿真。就最大旁瓣值、循环相关函数绝对值的平均值、均方值等指标与比较优良的二元序列进行对比，从而证明多相序列更加稳定和具有更强的抗同道多址干扰的能力。
由于工程上对地址码的要求是必须具有尖锐的自相关函数，而互相关函数接近于零。因此，本文还对完全互补序列进行了部分研究，从而使序列达到理想的互相关特性。此外，还将对完全互补序列的构造方法进行改进，从而使序列的产生、复制更加方便、灵活。其后对四相完全互补序列进行了搜索研究。
本文最后指出了目前多相序列理论中存在的不足和未来的主要研究方向。
In the recent 20 years, CDMA communication system develops very fast because spread spectrum communication has the characteristics of saving spectrum resource ,having ideal anti-jamming and secrecy. Spread spectrum communication has become the mainstream of the development of today's communication. However, in CDMA communication system, the choice of address code is very importance. It decides the capability, anti-jamming and speed of connect and conversion of the system.
Today, in CDMA communication system, we use duality sequence as address code. People have deep and wide research in duality sequence. With the use of recent century algebra, people get a lot of duality sequences such as GMW sequence, No sequence, Bent sequence and so on. Although the construction methods of duality sequence have their excellences, they have limit. For example, there are few number of address code, and the improved degree of correlation is near to zero. Therefore, the duality sequence can not satisfy the demand of users and adapt the increase of user. In order to break through this limit, the research of multiphase has aroused the attention of scholars. One of the multiphase sequence construction method is advanced by Suehiro. The method is based on FH sequence and matrix. We can get more address codes and the correlation of the code is excellent. This make the research of address code in CDMA communication has a wide future.
This paper is based on the construction theory of multiphase sequence. We research and simulate the correlation of multiphase sequence. Then we will compare with duality sequence in several guidelines. We can prove multiphase sequence is more stabilization and has good anti-jamming ability.
The require of address code in project is that the sequence has acuity auto-correlation and the cross-correlation is near to zero. We research the complete complementary in this paper which has ideal cross-correlation. This paper also improve the construction of complete complementary and make the sequences are produced more easily. In the last, we search the 4-phase complete complementary.
Finally, this paper point out the shortcomings and main direction of research in the future.3
引文
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