於直接序列分碼多工通訊系統中, 給予每一通道不同的展頻碼作為通道區
隔之用,以使得所有的通道能在同一頻帶內傳送.該系統的效能主要受通道
間之互干擾所影響.通道的展頻碼間之互相關值為造成干擾的主要因素由
於對齊的正交碼之互相關值為零, QUALCOMM公司採用正交碼以構成具有低
互相關值之展頻碼集合. 正交碼集合一般可由Walsh-Hadamard矩陣求得.
本文提出Walshcode編碼器與解碼器之架構, 並將其運用於分碼多工雛型
設計上. 該雛型系統之展頻碼為m-sequence code, Gold code, 與
Walsh code所構成. 所提出之Walsh code編碼器於前向鍊路可作為一
Walsh code產生器使用. 此種Walsh code產生器多個可用於產生對齊良好
之Walsh序碼集合. 該正交序碼集合與一公用PN code (pilot PN code)合
成而產生正交性良好之展頻碼集合以便將通道間之相互干擾降至最低. 於
反向鍊路 上, 提出之Walsh編碼器用於將資料編碼以提高訊號的正交性.
由於Walsh code本身的自相關特性不良, 使得前向鍊路之序碼獲取稍有困
難. 利用適當的展頻碼長度設計與Walsh code之特性, 本文亦提出一藉由
同步pilot PN code來同步Walsh正交函蓋的方法.該方法使得前向鍊路接
收機於同步pilot PN code 後, 便擁有同時接收不同通道的能力. 意即該
接收機僅需一碼同步裝置即可對多個通道作同時接收. 該項設計將使得手
機更為簡便.

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.