臺灣博碩士論文加值系統

為了達到更佳的頻寬使用效率及保護通過有雜訊的通道之語音資料一直是無線傳輸系統重要的課題. iLBC(網際網路低速率語言編解碼器)目前被廣泛使用於在網際網路以傳輸語音. 本篇論文主要討論iLBC應用在北美ISM(industrial, scientific and medical. 工業,科學及醫療)頻帶, 利用MSK(minium shift key, 最小移頻鍵)作為窄頻道雙向無線通訊. 在模擬的系統中, 使用了數種不同的非均等誤碼保護(UEP, unequal error protection)策略來保護不同重要等級, 且通過AWGN (additive white Gaussian noise, 高斯雜訊通道)之iLBC資料. 最後, 利用”知覺語音評價”(PESQ, Perceptual Evaluation of Speech Quality)來量測語音的品質. 本論文顯示, 透過非均等誤碼保護法能夠提高PESQ的得分, 進而証明此系統可以比美傳統的FM雙向無線電.

To achieve more efficient usage of channel band width and provide better protection for the speech payload transmitted over lossy wireless transmission is an important topic in wireless communication system design. iLBC (internet low bit rate codec) is widely used in VOIP (voice over IP) application. This paper is concerned with use iLBC in narrow band MSK (minimum shift key) wireless transmission under north America ISM (industrial, scientific and medical) band. Simulation using different strategies of unequal error protection (UEP) scheme to protect different sensitive payload which passing through the AWGN (additive white Gaussian noise) channel. Finally, we utilize PESQ (Perceptual Evaluation of Speech Quality) to evalute the perceptual speech quality. The result is significant of improve PESQ scores in some strategies, and proof this system can compete traditional FM two way radio.

書名頁 i
中文摘要 ii
英文摘要 iii
Acknowledgments iv
Contents v
List of Figures vii
List of Tables ix
Chapter1: Introduction 1
1.1 Motivation 2
1.2 Thesis Organization 2
Chapter 2: iLBC 3
Chapter 3: Uneven Level Protection 8
Chapter 4: Speech Quality Assessment and PESQ 10
4.1 Speech Quality Assessment 10
4.2 PESQ – Introduction 10
4.3 PESQ Algorithm overview [13] 12
4.4 PESQ output 13
Chapter 5: ISM Band Two-Way Radio 15
5.1 USA ISM Band 15
5.2 FCC Rules 16
5.3 Design Goals 17
Chapter 6: Simulations 18
6.1 Simulation Environment and Condition 18
6.1.1 Sample speech database 18
6.1.2 iLBC speech encoder and decoder 19
6.1.3 UEP (Unequal Error Protection) module 19
6.1.4 Protective strategy 19
6.1.5 Convolutional encoder 20
6.1.6 Puncturing 21
6.1.7 Convolutional decoder 21
6.1.8 MSK modulator and demodulator 22
6.1.9 Channel 22
6.1.10 Speech quality evaluation 23
6.2 Receiving sensitivity estimation 23
6.2.1 Noise figure of RF module 24
Chapter 7: Result 26
7.1 Investigation of MSK BER performance under AWGN channel. 26
7.2 Investigation of which degraded data dominate the speech quality 26
7.4 Strategy 2, 3 and 4: convolutional coding with coding rate 1/2 34
7.5 Strategy 5, 6 and 7: convolutional coding with coding rate 2/3 37
7.6 Strategy 8: convolutional coding with coding rate 1/2 for class 1, coding rate 2/3 for class 2. 40
7.7 Comparison of each strategy in receiving sensitivity and speech quality 42
Chapter 8: Conclusion 43
References 44

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