多頻正交分頻多工系統同步之研究

Abstract

多頻正交分頻多工系統 (MB-OFDM) 為一種利用跳頻展頻(FHSS)將 OFDM訊號頻寬展開的超寬頻 (Ultra-wide band)系統。然而因其為慢跳頻( slow frequency hopping) 及有限的可跳頻頻帶，在多個子網路 (piconet) 時，其頻帶可能因交錯而互相干擾，因此在設計 MB-OFDM 接收機時，其對共頻帶干擾的強健性為一重要的課題。 本論文提出一個對干擾具有高強健性的封包偵測架構。此架構是利用一匹配濾波器 (match filter)，對輸入信號與封包頭的訓練序列(training sequence)進行匹配濾波。並利用訓練序列的週期性，將匹配濾波器的輸出進行延遲相關 (delay correlate)運算而達成高強健性的目的。本論文同時提出對其他的同步問題作出討論，並提出一可行的同步程序。

Multi-band orthogonal frequency-division multiplexing (MB-OFDM) is an UWB modulation technique which combines OFDM and frequency hopping spread spectrum (FHSS) to archive high data rate and low interference to other communication systems. Due to its slow-hopping pattern, OFDM technology and the limited number of frequency bands available, when geographically overlapped multiple piconets are considered, there is no coordination of transmissions among different piconets. The robustness to interference is thus an important issue for MB-OFDM systems. This thesis provides a packet detection scheme which is robust to the interference of simultaneous operating piconets (SOP). This scheme makes use of a match filter (MF) to match the preamble, and a delay correlator is utilized to take advantage of the periodicity of MB-OFDM preamble. This thesis also discuss other synchronization issues like carrier frequency offset and sampling clock offset for MB-OFDM system.