The Eigenvalue Moment of Correlation Matrix in Asynchronous CDMA System

• Main Authors: Chin-Han Lee, 李青翰
• Other Authors: Chien-Hwa Hwang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/28854730823077450414

碩士 === 國立清華大學 === 通訊工程研究所 === 93 === The analysis of long-code direct sequence-code division multiple access (DS-CDMA) system has been well addressed in recent years. However, most work concentrates on synchronous systems, which leaves the study of asynchronous sys- tems unexplored. In this thesis, we consider the eigenvalue moment of correlation matrix in a long-code quasi-synchronous CDMA system, where quasi-synchronous denotes users’ chip boundaries are aligned but symbol boundaries are not. Since the random spreading in a long-code system makes the analysis very difficult, a large system assumption is made, where both the user number K and the spreading gain N approach infinity while their ratio K/N is kept as a constant. It is known that, in synchronous CDMA system, the output SINR of a linear multiuser receiver is related to the moment computation of spreading codes’ cor- relation matrix. We first make use of the one-shot approach to render a quasi-syn- chronous system into a synchronous one. By doing so, each user of quasi-synchr- onous CDMA is separated into two virtual ones in synchronous CDMA with their spreading codes being single-sided. To account for the effect of single-sided spreading codes, a graphical approach is developed for the moment computation of single-sided spreading codes’ correlation matrix. It is shown that, with the large system assumption, the graphical method is very efficient in solving the moment computation problem.