臺灣博碩士論文加值系統

本論文提出一種適用於無線通訊系統的時間與頻率偏移估測技術，利用雙啁啾信號可有效地估測時間與頻率誤差。此方法可應用於各種通訊環境之同步。我們提出時域與頻域兩種接收器，並比較兩者的效能與準確度。其中一接收器使用兩個時域相關器，藉著估測時間峰值進行線性組合運算以估測時間與頻率。另一則使用一組成對的頻域相關器，藉著估測頻率峰值進行線性轉換以估測時間與頻率。最後以正交分頻多工系統之參數進行模擬，結果證明其可有效地達成同步。

This paper describes two novel structures for reception of dual-chirp
waveforms. The approaches provide mechanisms for synchronization in
various communications environments. Both detection performance, and time
and frequency estimation accuracy are analyzed and simulated. One receiver
utilizes a dual time-domain correlator to initially estimate two peak times after
detection. Time and frequency estimates are obtained by linearly combining the
peak time estimates. The second receiver uses paired frequency-domain
correlators to initially estimate two peak frequencies and then linearly convert
them to the time and frequency estimates.

第一章緒論1
1.1 導論1
1.2 研究動機3
第二章正交分頻多工系統及無線傳輸通道4
2.1 正交分頻多工系統概述4
2.2 正交分頻多工系統之同步問題7
2.3 無線傳播通道10
2.3.1 衰落效應(Fading Effect) 10
2.3.2 都卜勒頻率偏移(Doppler Shift) 11
2.3.3 延遲展延(Delay Spread) 12
2.3.4 平坦衰落(Flat Fading) 13
2.3.5 頻率選擇性衰落(Frequency Selective Fading) 13
2.4 都卜勒擴散引起的衰落效應14
2.4.1 快速衰落(Fast Fading) 14
2.4.2 緩慢衰落(Slow Fading) 15
2.4.3 瑞雷衰落(Rayleigh Fading) 16
第三章以啁啾信號實現OFDM 信號同步18
3.1 啁啾信號之簡介19
II
3.1.1 啁啾信號(Chirp Signal) 19
3.1.2 雙啁啾信號(Dual Chirp Signal) 20
3.2 啁啾信號之同步接收器21
3.2.1 時域相關接收器21
3.2.2 頻域相關接收器27
3.2.3 時域相關接收器與頻域相關接收器之複雜度30
3.2.4 估測效能32
3.3 實際雙啁啾信號估測效能34
3.3.1 二階估測34
3.3.2 模擬結果35
3.3.3 PRP-OFDM 通道估測43
第四章結論與未來展望46
參考文獻47

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