臺灣博碩士論文加值系統

超寬頻無線系統為一室內5到10公尺高速傳輸的無線通訊系統，因此訊號將遭遇到室內密集性多重路徑通道(Dense Multipath Channels)。倘若面對密集的多重路徑通道時，展頻碼正交特性不佳，將受到強烈的符際間干擾(Inter-Symbol Interference, ISI)，本篇論文將討論各種接收機在面對強大的符際間干擾時效能變化。犁耙接收機(Rake Receiver)可以收集散佈於通道的能量，但同時也納入因展頻碼非正交所產生的強烈干擾。最小均方誤差(Minimum Mean Square Error, MMSE)等化器雖然可以很成功地收集通道上的能量和抑制符際間干擾，但其運算複雜度太高。本篇論文是將干擾消除和犁耙接收機結合，我們將利用干擾消除來提升犁耙接收機的效能，若干擾消除在犁耙接收機之前，我們將此方法稱為ISIC RAKE；若干擾消除在犁耙接收機之後，我們將稱之為RAKE ISIC。我們將過去位元和下一個位元所造成的干擾消去，若為多使用者狀態時，我們不只減去使用者自己前後位元產生的符際間干擾，也消去其他使用者所產生的多重存取干擾(Multi-Access Interference, MAI)。由模擬結果顯示我們所提的方法效能會比傳統犁耙接收機好，且與最小均方線性等化器(LMS Linear Equalizer)相仿，但擁有較低的運算複雜度。

Ultra-wideband (UWB) system is an indoor communication system, high data rate transmission within 5-10m transmitted range. This system suffers from high dense multipath channels impairment. If the spreading code is not orthogonal in dense multipath channels, severe inter-symbol interference (ISI) will degrade the system performance. In this thesis, we will discuss the performance of various receivers in ultra-wideband channels.
Rake receiver can collect signal energy from different multipath. However, the imperfect orthogonal property of spreading code will cause severe ISI and degrade the performance of Rake receiver. Least mean square (LMS) chip equalizer not only combines the energy from different multipath, but also suppresses ISI. But, the complexity is too high to realize.
In this thesis, we combine Rake receiver with ISI canceller to enhance system performance. If the canceller is before Rake receiver, we define it as ISIC RAKE. If the canceller is behind Rake receiver, we define it as RAKE ISIC. In the ISI canceller, not only ISI caused by preceding bits is cancelled, but also the ISI caused by following bit is cancelled. In multiuser cases, we are also canceling multi-access interference (MAI). From simulation results, the proposed method outperforms conventional Rake receiver, Rake receiver combined with LMS symbol equalizer, and LMS chip equalizer. The complexity of proposed method is lower than LMS chip equalizer.

誌謝 i
摘要 ii
Abstract iii
目錄 iv
圖索引 vii
表索引 xiii
第一章 簡介 1
1.1 研究動機 1
1.2 各章提要 3
第二章 系統架構 4
2.1 系統架構 4
2.2 通道模型 6
第三章 接收機架構 9
3.1 犁耙接收機(Rake Receiver) 9
3.2 最小均方誤差等化器(MMSE Equalizer) 11
3.2.1 最小均方線性等化器（LMS Linear Equalizer） 12
3.2.2 最小均方決策回授等化器（LMS Decision Feedback Equalizer） 15
3.3 RAKE LMS Receiver 16
3.4 ISIC RAKE 和RAKE ISIC 17
3.4.1 ISIC RAKE 17
3.4.2 干擾消除位元數之探討 20
3.4.3 多使用者況狀下之延伸 23
3.4.4 RAKE ISIC 26
3.5 複雜度計算 28
3.5.1 最小均方線性等化器之複雜度計算 28
3.5.2 最小均方決策回授(LMS DFE)等化器之複雜度計算 29
3.5.3 犁耙接收機 複雜度計算 30
3.5.4 RAKE LMS之複雜度計算 30
3.5.5 ISIC RAKE複雜度計算 31
3.5.6 RAKE ISIC複雜度計算 32
3.5.7 複雜度綜合比較 34
第四章 系統模擬 37
4.1 系統模擬環境設定 37
4.2 犁耙接收機 38
4.2.1 有符際間干擾的狀況下 38
4.2.2 沒有符際間干擾的狀況下 41
4.3 最小均方線性切片等化器(LMS Linear Chip Equalizer) 44
4.4 RAKE LMS Receiver 47
4.5 ISIC RAKE Receiver 60
4.6 RAKE ISIC Receiver 65
4.7 單使用者效能的綜合比較 71
4.8 多使用者狀況下，ISIC RAKE效能 74
第五章 結論 82
參考文獻 83

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