臺灣博碩士論文加值系統

在無線光通訊系統的環境中，利用紅外線光訊號來傳輸資料有以下的優點：它可以提供一個很大的頻寬、可以防止多路徑的衰減、而且可以在每個建築的房間裡重複使用頻段等優點。我們使用脈波位置調變(PPM)來增加它的功率使用效率，但因為它較差的頻寬使用效率，使得PPM更容易遭受到訊符間干擾的影響。
此論文中我們在室內無線紅外線通道上分析脈波位置調變加上格狀碼的性能，我們可以看出格狀碼應用在脈波位置調變上可以有效的減低多路徑所引起的訊符間交互干擾。我們使用的是2/3格狀碼和3/4格狀碼加上脈波位置調變以配合實際情形，然後推導出它的上限區域跟下限區域並與實際模擬結果做比較。並且評估在不同的通道衰減係數下格狀碼脈波位置調變系統的位元錯誤機率和訊號雜訊比的需求量。最後我們使用蒙地-卡羅模擬來驗證我們的分析。證實在高速紅外線通道上使用格狀碼加上脈波位置調變是一種很好的方法

In the wireless optical communication environment, data transmission by an optical signal has the following advantages over a conventional RF signal: offering a large potential bandwidth, immunity to multipath fading, and allowing the reuse of the same spectrum in every room of a building. In practice we use the Pulse Position Modulation (PPM) scheme to increase the power efficiency. However, due to its poor bandwidth efficiency, PPM is more susceptible to intersymbol interference (ISI).
In this thesis, we analyze the performance of PPM with trellis-coded modulation (TCM) on indoor wireless infrared channels. We show that the application of TCM to PPM can effectively reduce the influences of ISI induced by dispersive channel. The TCM 8-PPM with the code rate of 2/3 and the TCM 16-PPM with the code rate of 3/4 are used for our study to comply with practical situation.
The upper bound and lower bound of the BER performance are derived and the numerical results are compared with these from simulations. We execute the bit-error rate analysis and evaluate the signal-noise ratio requirements for different TCM-PPM schemes over the dispersive channel with various delay spreads. Finally we present Monte Carlo simulation results to verify our analysis. Our results indicate that TCM is a very promising coding technique for L-PPM on high speed infrared channels.

Abstract in Chinesei
Abstract in Englishii
Acknowledgmentiii
Contentsiv
List of Figures and Tablesvi
Chapter 1 Introduction1
1.1 Wireless Optical LAN1
Chapter 2 Basic Principles4
2.1 L-PPM Systems4
2.1.1 Representations for Pulse Position Modulation Systems6
2.2 Trellis Coded Modulation System10
2.2.1 Fundamentals of TCM10
2.2.2 Uncoded Transmission12
2.2.3 The concept of TCM13
2.2.4 Trellis Representation15
2.2.5 Trellis Coded Modulation (TCM)16

Chapter 3 System Model and Performance Analysis26
3.1 Non-directed Wireless Infrared Channel and Noise Model26
3.2 Trellis Coded Modulation Performance Evaluation29
3.3 Upper Bound to Error Probability30
3.4 Error State Diagram33
3.5 The Transfer Function Bound34
3.6 An improved Upper Bound35
3.7 Bit Error Probability36
3.8 Computation of the Transfer Function37
3.9 An improved Bit Error Probability Upper Bound38
3.10 Lower Bound to Error Probability42
Chapter 4 Numerical and Simulation Result44
4.1 The PPM System44
4.2 The PPM System with TCM48
4.3 The TCM PPM System with Block Decision Feedback Equalizer (BDFE)52
4.4 The Numerical Upper and Lower Bound of TCM PPM system56
Chapter 5 Conclusions and Future Works58
5.1 Conclusions58
References60
List of Figures and Tables

Fig.2.1 Transmitter of L-PPM system 6
Fig.2.2 Transmitter of L-PPM system, where L=8 in this example 7
Fig.2.3 Transmitter of L-PPM system8
Fig.2.4 Transmitter of L-PPM system8
Fig.2.5 General model for TCM15
Fig.2.6 The Trellis of a TCM scheme with four states16
Fig.2.7 General structure of combined encoder/modulator17
Fig.2.8 (a) Trellis Code Encoder18
Fig.2.8 (b) State table18
Fig.2.9 General model for TCM19
Fig.2.10 State transition table19
Fig.2.11 Trellis diagram for an 8-PPM TCM scheme20
Fig.2.12 Set partitioning for 8-PPM20
Fig.2.13 TCM scheme based on a four-state trellis, M’=4 and M=8. Two error events are shown. The free distance is determined by the error event21
Fig.2.14 Transmitter of wireless optical Trellis coded L-PPM block diagram23
Fig.2.15 Receiver of wireless optical Trellis coded L-PPM block diagram23

Fig.3.1 Normalized impulse response of exponential channel with different Dt28
Fig.3.2 Model of a TCM encoder30
Fig.3.3 Error state diagram for a four state with the weight profile34
Fig.3.4 Error state diagram for a four state37
Fig.3.5 Set partitioning for 8-PPM39
Fig.3.6 Trellis diagram for an 8-PPM TCM scheme40
Fig.3.7 Error state diagram for a four state with the weight profile40
Fig. 4.1.1 The bit error probability versus SNR for different dispersion parameters as indicated for 8-PPM system.45
Fig. 4.1.2 The bit error probability versus SNR for different dispersion parameters as indicated for 16-PPM system.46
Fig. 4.1.3 A comparison of the bit error probabilities 8-PPM and 16-PPM systems in the ISI free environment46
Fig. 4.1.4 The bit error probability versus SNR for 8-PPM and 16-PPM systems with different values of normalized dispersion parameters.47
Fig. 4.2.1 The bit error probability versus SNR for different dispersion parameters as indicated for TCM 8-PPM system. 49
Fig. 4.2.2 The bit error probability versus SNR for different dispersion parameters as indicated for TCM 16-PPM system.49
Fig. 4.2.3 The bit error probability versus SNR for 8-PPM and TCM 8-PPM systems with different values of normalized dispersion parameters.50
Fig. 4.2.4 The bit error probability versus SNR for 16-PPM and TCM 16-PPM systems with different values of normalized dispersion parameters.50
Fig. 4.2.5 The bit error probability versus SNR for TCM 8-PPM and TCM 16-PPM systems with different values of normalized dispersion parameters.51
Fig. 4.3.1 The bit error probability versus SNR for different dispersion parameters as indicated for TCM 8-PPM with BDFE system.53
Fig. 4.3.2 The bit error probability versus SNR for different dispersion parameters as indicated for TCM 16-PPM with BDFE system.53
Fig. 4.3.3 The bit error probability versus SNR for 8-PPM and TCM 8-PPM with BDFE systems with different values of normalized dispersion parameters.54
Fig. 4.3.4 The bit error probability versus SNR for 16-PPM and TCM 16-PPM with BDFE systems with different values of normalized dispersion parameters.54
Fig. 4.3.5 Comparison for SNR requirement for 8-PPM and 16-PPM system55
Fig. 4.4.1 The numerical upper and lower bound of TCM 8-PPM.56
Fig. 4.4.2 The numerical upper and lower bound of TCM 16-PPM.57
Table 3.1(a) Computation of W(011)39
Table 3.1(b) Computation of W(011)39

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