Synchronization Technologies For OFDM Based Broadband-Satellite System

Broadband-satellite mobile communication pays an important role in modern wireless communication field, but it has so limited frequency resource, and is easily affected by circumstance condition such as rain, thus can be suppressed by nonideal channel characteristics.Orthogonal frequency division multiplex(OFDM) is suitable for Broadband-satellite mobile communication system with the advantage of robustness to muti-path and high bandwidth efficiency. In this thesis an OFDM based Broadband-satellite system is studied, emphasizing particularly on the synchronization technologies.This thesis describes the channel characteristics of Broadband-satellite communication system and establishes current channel simulation model. Following the introduction of the basic principle of OFDM, some nonideal effects on the performance of OFDM systems are discussed, such as carrier frequency offset, symbol timing offset and sampling clock deviation. Then synchronization technologies are analyzed in more detail, and some typical OFDM synchronization schemes are studied and improved.After investigating synchronization scheme proposed by Schmidl & Cox, an special training sequences with good auto correlation characteristics and less affected by noise are put forward, thus improve symbol timing and float frequency synchronization performance through average process.And a more effective integral frequency synchronization scheme by modify the adjudgement also is proposed. As the PN-sequence based scheme, a novel algorithm utilizing all the channel taps power is provided.This thesis also studied synchronization schemes based on pilots symbols and a scheme proposed by Moose, meanwhile, some modified points as above have been put forward.Besides, the whole synchronization schemes for the OFDM based Broadband-satellite communication system are designed .Through simulation and comparing, appropriate synchronization schemes for frame detection, symbol timing,frequency offset estimation and phase tracking are discussed separately, and the system performances with ideal and nonideal synchronization are compared.