Speech Quality of VoIP: Assessment and Prediction

Finally a comprehensive overview of speech quality in VoIP from the user’s perspective!

Speech Quality of VoIP is an essential guide to assessing the speech quality of VoIP networks, whilst addressing the implications for the design of VoIP networks and systems. This book bridges the gap between the technical network-world and the psychoacoustic world of quality perception.  Alexander Raake’s unique perspective combines awareness of the technical characteristics of VoIP networks and original research concerning the perception of speech transmitted across them.

Starting from the network designer’s point of view, the different characteristics of the network are addressed, and then linked to features perceived by users. This book provides an overview of the available knowledge on the principal, relevant aspects of speech and speech quality perception, of speech quality assessment, and of transmission properties of telephone and VoIP networks, and of the related perceptual features and resulting speech quality. Discussing new research into the specific time-varying degradations VoIP brings along, but also the considerable potential of quality improvement to be achieved with wideband speech transmission, Alexander Raake demonstrates how network and service characteristics impact on the users perception of quality.

Speech Quality of VoIP:

• Offers an insight into speech quality of VoIP from a user's perspective.
• Presents an overview of different modelling approaches and a parametric network-planning model for quality prediction in VoIP networks.
• Draws on innovative new research on the quality degradation characteristic of VoIP.
• Explains in detail how telephone speech quality can be greatly enhanced with VoIP’s wideband speech transmission capability.
• Assesses the vast collection of references into the technical and scientific literature related to VoIP quality.
• Illustrates concepts throughout with mathematical models, algorithms and simulations.
  

Speech Quality of VoIP is the definitive guide for researchers, engineers and network planners working in the field of VoIP, Quality of Service, and speech communication processing in telecommunications. Advanced undergraduate and graduate students on telecommunication and networking courses will also find this text an invaluable resource.

 

Table of Contents

Preface.

List of Abbreviations.

Introduction.

1 Speech Quality in Telephony.

1.1 Speech.

1.1.1 Speech Acoustics.

1.1.2 Speech Perception.

1.2 Speech Quality.

1.2.1 Definition of Quality.

1.2.2 Speech Quality Assessment.

1.2.3 Quality Elements.

1.2.4 Speech Quality and Quality of Service.

2 Speech Quality Measurement Methods.

2.1 Auditory Methods.

2.1.1 Utilitarian Methods.

2.1.2 Analytical Methods.

2.2 Instrumental Methods.

2.2.1 Signal-based Models.

2.2.2 Parameter-based Models.

2.2.3 Monitoring Models.

2.3 Speech Quality Measurement Methods: Summary.

3 Quality Elements and Quality Features of VoIP.

3.1 Speech Transmission Using Internet Protocol.

3.1.1 VoIP Applications .

3.1.2 VoIP Quality of Service.

3.2 Overview of Quality Elements.

3.3 Quality Elements and Related Features.

3.3.1 Voice Activity Detection (VAD).

3.3.2 Codecs.

3.3.3 Jitter.

3.3.4 Delay.

3.3.5 Packet Loss.

3.3.6 Bit Errors.

3.3.7 Talker Echo.

3.3.8 Listener Echo.

3.3.9 Echo Cancellers.

3.3.10 Loudness.

3.3.11 Noise.

3.3.12 Noise Suppression.

3.3.13 Linear Distortion and Wideband Transmission.

3.3.14 User Interfaces.

3.4 Quality Dimensions.

3.5 Combined Elements and Combined Features.

3.6 Listening and Conversational Features.

3.7 Desired Nature.

3.7.1 Context.

3.7.2 Cost.

3.7.3 Service Options.

3.8 Open Questions.

3.9 From Elements to Features: Modeling VoIP Speech Quality.

3.9.1 Signal-based Measures and VoIP.

3.9.2 ParametricModels and VoIP.

3.10 Quality Elements and Quality Features of VoIP: Summary.

4 Time-Varying Distortion: Quality Features and Modeling.

4.1 Microscopic Loss Behavior.

4.1.1 Random Packet Loss.

4.1.2 Dependent Packet Loss.

4.2 Macroscopic Loss Behavior.

4.2.1 Macroscopic Loss with Segments of Random Loss.

4.2.2 Macroscopic Loss with Segments of Dependent Loss.

4.3 Interactivity.

4.4 Packet Loss and Combined Impairments.

4.4.1 Additivity and Multidimensional Feature Space.

4.4.2 Microscopic Loss Behavior: Random Packet Loss.

4.4.3 Macroscopic Loss Behavior: 3-State Markov Loss.

4.4.4 Model: Packet Loss and Combined Impairments.

4.5 Time-Varying Distortion: Summary.

5 Wideband Speech, Linear and Non Linear Distortion: Quality Features and Modeling.

5.1 Wideband Speech: Improvement Over Narrowband.

5.1.1 Summary.

5.2 Bandpass-Filtered Speech.

5.2.1 Listening Test.

5.2.2 Parametric Impairment Model.

5.3 Wideband Codecs.

5.4 Desired Nature.

5.4.1 User Interfaces.

5.4.2 Content.

5.4.3 Summary.

6 From Elements to Features: Extensions of the E-model.

6.1 E-model: Packet Loss.

6.2 E-model: Additivity.

6.3 E-model: Wideband, Linear and Non-Linear Distortion.

7 Summary and Conclusions.

8 Outlook.

A Aspects of a Parametric Description of Time-Varying Distortion.

A.1 4-state Markov Chain: Sojourn in Bad and Good State.

A.2 Impact of Other Quality Elements on Packet Loss.

A.2.1 Forward Error Correction.

A.2.2 Jitter and Jitter Buffer.

A.3 Impairment under GSM Bit Errors.

B Simulation of Quality Elements.

B.1 PSTN/ISDN.

B.1.1 Instrumental Verification.

B.2 Mobile Networks.

B.3 VoIP.

B.3.1 Analog to ISDN Conversion.

B.3.2 VoIP Gateways.

B.3.3 IP Network Simulation.

B.3.4 Instrumental Verification.

B.4 Wideband Transmission.

B.5 User Interfaces.

B.5.1 Handset Telephones.

B.5.2 Headsets.

B.5.3 Wideband Handset and Hi-fi Phone.

B.5.4 Bandpass Filters.

B.5.5 Hands-free Terminals (HFTs)

B.6 Test Rooms.

B.7 Simulation of Quality Elements: Summary.

C Frequency Responses.

C.1 Transmission Bandpass.

C.1.1 Narrowband.

C.1.2 Wideband.

C.2 User Interfaces.

C.2.1 Headsets.

C.2.2 Wideband Handsets.

D Test Data Normalization and Transformation.

D.1 Equivalent-QMethod.

D.2 Method According to ITU-T Rec. P.833.

D.3 Linear Transformation.

D.4 Note onMOS-terminology.

E E-model Algorithm.

F Interactive Short Conversation Test Scenarios (iSCTs).

F.1 Example.

G Auditory Test Settings and Results.

G.1 Global System for Mobile (GSM): Short Conversation and Listening Only Test.

G.2 2-stateMarkov Loss: Listening Only Test.

G.3 Random Loss: Conversation Test.

G.3.1 Test Setup.

G.3.2 Test Procedure.

G.3.3 Subjects.

G.3.4 Details on Selected Results.

G.4 3-state Markov Loss: Conversation Test.

G.4.1 Test Setup.

G.4.2 Test Procedure and Test Subjects.

G.4.3 Details on Selected Results.

G.5 Speech Sound Quality and Content.

H Modeling Details.

H.1 Time-Varying Distortions.

H.1.1 Macroscopic Loss Behavior.

I Glossary.

Bibliography.

Index.