Timing, Frequency Synchronizations and Channel Estimation of an OFDM System

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基本資料

Project title

Code/計畫編號

NSC98-2221-E019-011

Translated Name/計畫中文名

OFDM系統時間同步、頻率同步及通道快速估測方法之研究

Project Coordinator/計畫主持人

Chi-Min Li

Funding Organization/主管機關

National Science and Technology Council

Co-Investigator(s)/共同執行人

湯譯增
吳家琪

Department/Unit

Department of Communications, Navigation and Control Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=1914068

Year

2009

Start date/計畫起

01-08-2009

Expected Completion/計畫迄

31-07-2010

Bugetid/研究經費

695千元

ResearchField/研究領域

電信工程

"正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)系統，因以正交子載波傳輸資料，具有高頻寬使用率，並能有效克服頻率選擇性衰弱通道(frequency selective fading channel)，已被廣泛應用於無線通訊系統，例如IEEE802.11a/g、Terrestrial Digital Video Broadcasting (DVB-T)、DVB-H (Digital Video Broadcasting for Handheld)與 IEEE802.16 Wireless MAN 等。 OFDM 系統研究的課題之一為探討同步(Synchronization)問題，包含時序同步(Timing Synchronization)與載波頻率偏移(Carrier Frequency Offset, CFO)同步兩部分。時序同步的目的為標示出時域符元的起始時間點，而時序偏移的存在，將導致符元間的干擾 (Inter-Symbol Interference, ISI)，進而降低資料傳輸的正確率。載波頻率偏移則會影響子載波間的正交性，即子載波間的頻率干擾(Inter-Carrier Interference, ICI)。通道估測一般為利用接收端已知的Pilot，估測未知通道的資訊，藉以降低傳輸訊號受通道環境的影響。本計畫為『OFDM 系統時間同步、頻率同步及通道快速估測方法之研究』，本計畫主要討論OFDM 系統之時序同步、頻率偏移及通道估測，並提出Constant Pilot Padding Method。此方法為在頻域上，規律的安插調變資料符元，可在時域產生具備重複(repetitive) 特性之Preamble 符元，藉以進行時序同步估測及頻率偏移估測，並以在頻域所填補之 Pilot 符元，提供通道估測能力。在此方法所產生之Preamble 符元中，由於可傳送一定數目之資料符元，可藉以改善傳統Data Aided 同步方法，系統通道容量使用效率不佳之缺點。本計畫將以一年時間，完成下列主題: 1. 建立OFDM 訊號產生及處理能力。 2. 提出一對OFDM 時間偏移、頻率偏移、通道響應快速估測方法。 3. 利用實測通道驗證提出方法的實用性。 4. 論文發表及專利申請。""Orthogonal Frequency Division Multiplexing (OFDM) has been widely adopted in the current wireless communication systems, such as IEEE802.11a/g, Digital Video Broadcasting for Handheld (DVB-H), and IEEE802.16 Wireless MAN, due to its high bandwidth efficiency and the ability of overcoming frequency selective fading channel. The synchronization problems of the OFDM system include the timing synchronization and the frequency synchronization. Improper synchronization will result in the inter-symbol interference (ISI) and the inter-carrier interference (ICI). Besides, channel estimation of a wireless system can be conducted via using the pilot symbols at the transmitter to reduce the channel distortion. In this project, we will analyze and propose a Constant Pilot Padding Method (CPPM) to perform the timing, frequency synchronization and the channel estimation of an OFDM system. The time domain preamble generated by the CPPM contains the repetitive waveform to perform both the timing and frequency synchronizations. Besides, due to the symbols-carrying ability of the generated preamble, the CPPM method can improve the bandwidth inefficient drawback of the conventional data-aided synchronization methods such as the S&C Method and the Park’s Method. One year is planned to execute this project. Related working issues are listed below: 1. We will build up the signal processing ability of the OFDM system. 2. We will propose a novel CPPM method to solve the synchronization and the channel estimation problems of the OFDM system. 3. We will also use the measured channels to verify the proposed method. 4. Papers and patent applications will be submitted of the project results."

DSpace CRIS

Timing, Frequency Synchronizations and Channel Estimation of an OFDM System

基本資料

Description