Spreading Code Structural Analyses for DS/CDMA Communication

• Main Authors: Chin-Chai Kang, 康晉嘉
• Other Authors: Jen-Fa Huang
• Format: Others
• Language: en_US
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/57936442142183902051

碩士 === 國立成功大學 === 電機工程研究所 === 84 === In DS/CDMA system, each channel is given its own spreading code as channel distinction in order to transmit signal on the same bandwidth. The performance of a CDMA system depends mainly on the multiple access interference coming from other channel. The cross-correlation of spreading codes is an important fact that results in the interference. Because the cross-correlation of aligned orthogonal codes is zero. orthogonal codes are introduced to construct spreading codes by QUALCOMM.Generally, orthogonal codes can be derived by the Walsh-Hadamard matrix.In this thesis, a Walsh encoder and a Walsh decoder are proposed. They are used in a DS/CDMA prototype design. The spreading codes are composed of msequence code, Gold code and Walsh code. The proposed Walsh encoder can be used as a Walsh code generator. Several such Walsh code generators can generate aligned different Walsh code sequences. The generated Walsh codes used in the forward link make the spreading codes orthogonal and reduce the interference. The Walsh code encoding used in the reverse link improves the transmitted signal's orthogonality. Because the auto-correlation of the Walsh codes is not good, acquisition of the orthogonal covering may depend on the acquisition of the pilot PN code in the forward link. It can be achieved by proper desgin for the spreading code structure. Such a design makes the forward link receiver able to access multiple channels simultaneously by a pilot PN code synchroniza- tion device. It simplifies the mobile station's receiver.