基於OFDM多重進接技術在蜂巢式系統方面應用之研究

Abstract

OFDM被認為可能將成為下一代蜂巢式系統的一種調變技術。這篇論文將介紹數種目前在學術界被提出多重進接的方式，而且我們會提出一套利用分頻多重進接的寬頻OFDM系統。這套系統的特點是在蜂巢架構中，所有的頻率可被每個蜂巢細胞重複使用，而要傳送出去的資料，會先被一Walsh碼所展頻，再乘上一個攪亂碼來達到足夠的處理增益。此系統也包含了一個簡單的通道估計演算法，其原理是利用收到事先已知的資料來估計通道。電腦將模擬整個系統在數種通道下的效能與涵蓋率分析。

Orthogonal Frequency Division Multiplexing (OFDM) is regarded as one promising solution for next generation cellular systems. This thesis introduces several OFDM-based multiple access schemes and we also propose a new wideband OFDM system with FDMA. Our proposed system applies universal frequency reuse in cellular structure. The data is first spreaded by a Walsh code and multiplied by a short scrambling code. The purpose of spreading process is to obtain enough processing gain. A simple channel estimation algorithm is achieved by sending a known data. The system performance and coverage analysis are simulated by computer under several channel models.