OFDM系統中的前導序列偵測

Abstract

在現行的正交分頻多工(OFDM)系統和標準，對於時間和頻率的初始同步大多使用前導訊號波形，因此如何正確地偵測前導訊號序列是十分重要的議題。在現有的文獻中，通常使用自相關方法(autocorrelation method)或互相關方法(crosscorrelation method)進行前導訊號序列的偵測，然而這些方法對於通道的變化是敏感的。 在這篇論文中，基於廣義概似比檢驗(GLRT)和尼曼皮爾森(Neyman Pearson)標準，新的前導訊號偵測方法被提出，這些方法在前導訊號偵測的效果對於通道變化十分不敏感，能夠在未知的通道環境中提供強大的表現。

In practical orthogonal frequency division multiplexing systems and standards, preamble waveforms are adopted to facilitate initial timing and frequency synchronization. Therefore, how to detect preamble sequences correctly is a crucial issue. In the literature, autocorrelation method and crosscorrelation method are commonly used to detect preamble sequences. However, both of the two methods are sensitive to the channels which preamble is transmitted in. In this thesis, the new preamble detection methods based on the generalized likelihood ratio test (GLRT) principle and the Neyman Pearson (NP) criterion are proposed. These preamble detection methods are not sensitive to channels, and they can provide a robust performance even if channel is unknown.