多片率多碼展頻系統

Abstract

在展頻系統中,發射端的窄頻資料先經由選定的展頻碼展成寬頻訊號後,再經射頻調變傳送出去,而在接收端則以相應的碼解展頻完成接收。因此選擇優良的展頻碼架構,對展頻系統的效能將有很正面的影響。本文首先研究在不增加現有頻寬的前提下,採用多片率多碼架構的可行性與效能評估。模擬結果發現相較於傳統的單一片率/單一展頻碼傳輸型式,採用多片率多碼架構並適當搭配展頻碼,其整體干擾量可以達到一定程度之改善。此外鑑於傳統的二元展頻碼受限於特定的長度,本文提出一種不受長度限制的三極性正交碼,詳細研究其建構方式及錯誤率相關性質,並和傳統的二元展頻碼做比較。

In a spread spectrum system, the narrowband data streams in the transmitter are spread into wideband signals by specific spreading codes and then transmitted through RF carriers. In the receiver, the corresponding spreading codes must be used to recover the data sequences. Thus the proper selection of spreading code families will effectively increase the system efficiency. In this thesis we first focus on the capability and performance evaluation of the multiple-chip-rate / multiple-code (MCR/MC) architecture, under the condition that no additional bandwidth is required. We found that with proper utilization of multiple spreading code sets with multiple chip rates, the interference performance of the MCR/MC spread spectrum systems can be superior to that of the traditional single-chip-rate / single-code spread spectrum systems. In addition, we propose trinary coding which generates orthogonal spreading codes with arbitrary code length in order to alleviate the restriction of binary spreading codes which can only have some specific code length. The construction algorithm and related properties are studied and compared with the binary coding.