高階差分幅相移鍵調變行動通訊傳輸系統中通道估測之DSP實現

Abstract

在論文中我們研究應用在高階差分幅相移鍵(DAPSK)的調變傳輸系統中的通道估測技術,此系統使用了前置輔助信號(preamble-assisted signal)以改善行動通訊系統中的通道衰落和頻率飄移問題。在接收端,接收到的前置輔助信號(preamble-assisted signal)用來估測由多重路徑衰落和頻率飄移所造成的通道衰退.同樣地,所接收到的資料(data symbols)也用來加強對通道估測的精準度。 同時我們也藉由電腦模擬來研究六十四階前置輔助信號的差分幅相移鍵調變傳輸系統中的位元錯誤率。在模擬中我們使用非頻率選擇的通道,並且考慮頻率飄移的問題。最後,我們使用Blue Wave Systems的DSP板來實現DAPSK傳輸系統之即時處理。

This thesis presents a channel estimation technique, combining fading estimation and frequency offset estimation, for preamble-assisted high-level differentially encoded amplitude-and phase-shift keying (64-DAPSK) transmission in the digital mobile radio system. The received preamble symbols are used to estimate the combined distortions caused by multipath fading and frequency offset. The detected data symbols as well as preamble symbols are used to enhance the accuracy of the estimation process. A series of computer simulations have been carried out to investigate the bit error rate performances of the preamble-assisted 64-DAPSK signals with uncertain frequency offset in the frequency-nonselective fading channels. Finally, the real-time processing of a 64-DAPSK transmission system with channel estimation is implemented by a Blue Wave Systems DSP board.