正交分頻多工傳輸系統通道估計方法之研究

Abstract

正交分頻多工傳輸技術是由多載波調變演變而來，它具備了對抗碼際干擾能力，並能在低接收機複雜度下提供高速傳輸，目前已有數個系統採用此技術作為實體層傳輸技術。本文將介紹正交分頻多工技術的特性，及目前應用正交分頻多工作為實體層傳輸技術之系統，包括數位音響廣播，數位影像廣播之地面廣播，以及為於5GHz頻段的IEEE802.11a 無線區域網路。本論文中將介紹數種利用在已知次載波位置放置參考訊號，藉以估計通道響應的方法。此外，還提出利用嵌入式領航符元估計通道，藉以增加資料傳輸的可用次載波數目。經過電腦模擬結果顯示，利用嵌入式領航符元估計通道在大部分的情況下都有較佳的表現。

Orthogonal Frequency Division Multiplexing （OFDM）comes from multi-carrier transmission technique. It alleviates the inter-symbol interference（ISI） and achieves high-data-rate transmission with low complexity. In this thesis, three existing OFDM-based systems are introduced, including the Digital Audio Broadcasting system （DAB）, the Terrestrial Digital Video Broadcasting system （DVB-T）, and the wireless LAN on the 5GHz band. Besides, several channel estimation methods based on pilot carrier insertion are introduced. Moreover, a new channel estimation method using embedded pilot signals is proposed. Our computer simulations show that in most cases the embedded-pilot-signal-based channel estimation outperforms the pilot-carrier-based channel estimation.