Fundamentals of Voice-Quality Engineering in Wireless Networks 无线网络语音质量工程基础

Network operators are faced with the challenge of maximizing the quality of voice transmissions in wireless communications without impairing speech or data transmission. This book provides a comprehensive survey of voice quality algorithms, features, interactions, and trade-offs, at the device and system level. Using a practitioner rather than algorithm-designer angle, this book is unique. It elaborates on the root cause of impairments and ways for resolving them, as well as methodologies for measuring and quantifying voice quality before and after applying the remedies. The key issues are exemplified using case studies. Avoiding complex mathematics, the approach is based on real and sizable field experience supported by scientific and laboratory analysis. This title is suitable for practitioners in the wireless communications industry and graduate students in electrical engineering. Further resources for this title including a range of audio examples will be available online at www.cambridge.org/9780521855952.

Dr Avi Perry, a key contributor to the ITU-T G.168 standard, is currently an independent consultant. He was Vice President at NMS Communications, where he was responsible for core technology, system engineering, competitive analysis, documentation, and technical support. He has also held positions at Lucent Technologies and Bell Laboratories and the Northwestern University Graduate School of Management.

Preface
List of abbreviations
Introduction Plan of the book
Part Ⅰ Voice-quality foundations
1 An overview of voice-coding architectures in wireless communications
1.1 Introduction
1.2 Pulse-code modulation
1.3 Wireless codecs
1.4 Summary
1.5 Transmission media
1.6 Audio illustrations
2 Quantitative assessment of voice quality
2.1 Introduction
2.2 Measuring and quantifying voice quality
2.3 Relating voice-quality metrics to perceived worth
2.4 Mean opinion scores of wireless codecs
2.5 Standard computerized tools for speech-quality assessment
Part Ⅱ Applications
3 Electrical echo and echo cancelation
3.1 Electrical echo
3.2 Echo in wireless and long-distance networks
3.3 Echo control
3.4 Placement in the network
3.5 Convergence and adaptation processes
3.6 Tail delay and its impact on performance
3.7 Far-end echo cancelation
3.8 Background music-music on hold
3.9 Voice-response systems-barging
3.10 Hot signals
3.11 Voice-band data and fax
3.12 Signaling systems nos. 5, 6, and 7
3.13 Conclusions
4 Acoustic echo and its control
4.1 Introduction
4.2 Round-trip delay and echo dispersion
4.3 Reasons for perceiving acoustic echo in wireless communications
4.4 Controlling acoustic echo in digital-wireless networks-main considerations
4.5 Acoustic-echo activity detection
4.6 Residual acoustic-echo control in the frequency domain
4.7 The impact of comfort-noise matching on the performance-Of acoustic-echo control
4.8 Correcting impairments caused by some acoustic-echo control algorithms built into mobile handsets
4.9 Network topology of acoustic-echo control
4.10 Conclusions
5 Noisy ambience, mobility, and noise reduction
5.1 Noise in wireless networks
5.2 Introduction to noise reduction
5.3 The noise-reduction process
5.4 Noise reduction and GSM DTX
5.5 Noise reduction and CDMA EVRC and SMV codecs
5.6 Noise-reduction level compensation
5.7 Noise reduction and signals other than voice
5.8 Network topology of noise reduction
6 Speech-level control
6.1 Introduction
6.2 Basic signal-level measurements and definitions
6.3 Automatic level control (ALC)
6.4 Noise compensation (NC)
6.5 Combined NC and ALC
6.6 High-level compensation
……
Part Ⅲ Wireless architectures
Part Ⅳ A network operator's guide for selecting, appraising, and testing a VQS
Part Ⅴ Managing the network
Part Ⅵ Afterthoughts and some fresh ideas
Part Ⅶ Recordings