Perceptual Voice Quality Measurements for Wireless Networks

Perceptual Voice Quality Measurements for Wireless Networks

Dorel Picovici (Institute of Technology Carlow, Ireland) and John Nelson (University of Limerick, Ireland)
DOI: 10.4018/978-1-59904-820-8.ch011
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Abstract

Perceptual voice quality measurement can be defined as an objective quantification of an overall impression of the perceived stimulus. An alternative to laborious subjective testing is objective predictive modelling, which employs a perceptual model of the human auditory and cognitive system to predict the human response to a voice signal in terms of its quality. This chapter describes subjective and automated objective testing methods, and provides a test case scenario for measuring voice quality.
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Introduction

Wireless communications have opened up a range of new opportunities for telecommunication companies and service providers. In particular, wireless local area networks (WLANs), continue to provide increasing data bandwidth at lower cost, and now enable support for advanced mobile services. Although most existing wireless LANs based on the IEEE 802.11 specifications (the popular Wi-Fi networks) are predominantly targeted at best effort data traffic, there has been a very strong interest in integrating support for voice traffic using VoIP. Given the performance limitations of these wireless systems, assessing and addressing the perceptual voice quality is of major importance for both service providers and telecommunication system designers.

Perceptual voice quality measurement can be defined as an objective quantification of an overall impression of the perceived stimulus. Until the 1990s, the most reliable method for obtaining true perceptual measurement was to conduct a subjective test, which gives the group’s mean opinion score (MOS) of the quality of a voice signal under evaluation. Subjective tests are, however, slow and expensive to conduct, making them accessible only to a small number of laboratories and unsuitable for long-term or large scale voice quality monitoring.

An alternative to the subjective tests is represented by objective predictive modelling techniques. This approach employs the use of a perceptual model of the human auditory and cognitive system to predict the human response to a voice signal in terms of its quality. Such approaches are reported to be highly effective as the aim of the perceptual models is to simulate the response of listeners (end-users) participating in a subjective test. This has made the objective predictive modelling techniques very attractive for meeting the demands for perceptual voice quality measurements. Objective measurement techniques can be sub-divided into two types of predictive models:

  • a.

    Intrusive models: Compare an original voice signal with its degraded version that has been processed by a network under test. Due to their use of both signals (original and distorted) for processing such models are also known as comparison-based or full-reference.

  • b.

    Non-intrusive models can be used in mainly two configurations: (1) Non-intrusive signal-based models (also termed as no-reference, or single-ended models) where only the distorted voice signal is required for measuring its perceptual quality and (2) non-intrusive parametric models. Here, instead of using voice signals, several properties of the underlying transport and/or terminal, such as echo, delay, noise, network characteristics and reception measures are used to estimate the subjective MOS.

Following this introduction, Section 2 details the tests and methods used during subjective determination of voice quality. Due to their high price and time consuming subjective testing is not always practical. Automated objective models that can replace the subjective testing are reviewed in Section 3. Methods that are widely used for voice quality measurements for wireless networks are identified in Section 4. In addition, a test case scenario for measuring voice quality using the first wireless test platform for IEEE 802.11 wireless networks is also presented. Section 5 concludes the chapter and discusses future trends.

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Subjective Determination Of Voice Quality

Voice quality assessment measures that are based on ratings by human listeners are called subjective measures (ITU-T Recommendation P.800, 1996). These tests seek to quantify the range of opinions that listeners express when they hear voice transmission of systems that are under test. Properly designed subjective tests provide the most accurate way of assessing voice quality. However, the results of subjective tests are influenced by the conditions of the tests such as (ITU-T Recommendation E. 800, 1994):

  • Speech material: Perception of a speech signal depends on the gender of talkers, their particular pronunciation, the language, content, and length of the signal.

  • Test set-up: Results for the same test can vary depending on the listener’s previous experience with listening tests, nationality, the duration of the test, and the level of understanding.

  • Listening conditions: The individual ratings during the test are influenced by the loudness of the presented speech signals and choice of equipment used (i.e. headphones/ telephone handset).

Complete Chapter List

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Table of Contents
Foreword
Abbas Jamalipour
Preface
Nicola Cranley , Liam Murphy
Chapter 1
Ronan Skehill, William Kent, Dorel Picovici, Michael Barry, Sean McGrath
This chapter introduces quality of service in multi-access wireless networks. Specifically it demonstrates how QoS is implemented in IEEE 802.11 and... Sample PDF
Evaluating QoS in a Multi-Access Wireless Network
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Chapter 2
Dirk Staehle, Andreas Mäder
This chapter gives an overview of the background and functionality of the high speed downlink packet access (HSDPA), and provides insights into the... Sample PDF
Radio Resource Management Strategies for HSDPA-Enhanced UMTS Networks
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Chapter 3
Nidal Nasser, Tarek Bejaoui
Major research challenges in the next generation of wireless networks include the provisioning of worldwide seamless mobility across heterogeneous... Sample PDF
Handoff Management in Next Generation Wireless Networks
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Chapter 4
Ming Li, Roberto Riggio, Francesco De Pellegrini, Imrich Chlamtac
This chapter provides a comprehensive review of the architectures, algorithms, and protocols in the topic of resource management in IEEE... Sample PDF
Resource Management in IEEE 802.11 Based Wireless Networks
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Chapter 5
Anna Sfairopoulou, Carlos Macián, Boris Bellalta
Network Technologies and Strategies (NeTS) Research Group, Universitat Pompeu Fabra, SpainThis chapter introduces the problems caused to voice over... Sample PDF
Adaptive Codec Selection for VoIP in Multi-Rate WLANs
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Chapter 6
Michael M. Markou, Christos G. Panayiotou
This chapter introduces the network buffer control techniques as a mean to provide QoS. This problem has been extensively studied in the context of... Sample PDF
Buffer Control Techniques for QoS Provisioning in Wireless Networks
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Chapter 7
Gabriel-Miro Muntean, Janet Adams
Wireless networks are becoming a part of everyday life for many people. When a mobile device has wireless LAN capability, multimedia content can be... Sample PDF
Power Saving in Wireless Multimedia Streaming to Mobile Devices
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Chapter 8
Jose Luis Jodra, Fidel Liberal, Begoña Blanco Jauregi
This chapter introduces the principal characteristics of MANETs and shows how these particularities may affect both QoS conditions and QoS... Sample PDF
Multimedia Services Provision in MANETs
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Chapter 9
Andrej Kos, Mojca Volk, Janez Bester
Commonly understood as the next generation networks (NGN), a composite environment of proven telecommunications and Internet-oriented mechanisms has... Sample PDF
Quality Assurance in the IMS-Based NGN Environment
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Chapter 10
Marcio Nieblas Zapater, Graça Bressan
This chapter discusses the quality assurance of multimedia services over IP networks from the end user standpoint and introduces the concept of... Sample PDF
Quality of Experience for Video Services
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Chapter 11
Dorel Picovici, John Nelson
Perceptual voice quality measurement can be defined as an objective quantification of an overall impression of the perceived stimulus. An... Sample PDF
Perceptual Voice Quality Measurements for Wireless Networks
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Chapter 12
Tacha Serif, Gheorghita Ghinea
This chapter describes an investigation exploring user experiences of accessing streamed multimedia content, when that content is tailored according... Sample PDF
Enhancing the Multimedia Tour Guide Experience: Transmission Tailoring Based on Content, Location, and Device Type
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Chapter 13
Harilaos Koumaras, Fidel Liberal, Lingfen Sun
The concept of PQoS, although in general it deals with the user satisfaction with a specific delivered/ requested service, is in practice... Sample PDF
PQoS Assessment Methods for Multimedia Services
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Chapter 14
Peifang Zhang, Scott Jordan
Emerging wideband code division multiple access (WCDMA) data services will likely require resource allocation to ensure that throughput targets are... Sample PDF
Scheduling and Access Control for Wireless Connections with Throughput Guarantees
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Chapter 15
Paolo Chini, Giovanni Giambene, Snezana Hadzic
Nowadays there is an increasing need of broadband communication anytime, anywhere for users that expect to receive multimedia services with support... Sample PDF
Broadband Satellite Multimedia Networks
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Chapter 16
Panagiotis Papadimitriou, Vassilis Tsaoussidis
An increasing demand for multimedia data delivery coupled with reliance in best-effort networks, such as the Internet, has spurred interest on... Sample PDF
End-to-End Support for Multimedia QoS in the Internet
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Chapter 17
Tarek Bejaoui, Nidal Nasser
This chapter introduces the cross layer design for resource allocation over multimedia wireless networks. Conventional layered packet scheduling and... Sample PDF
Cross-Layer Radio Resource Management Protocols for QoS Provisioning in Multimedia Wireless Networks
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Chapter 18
Gürkan Gür, Suzan Bayhan, Fatih Alagöz
This chapter introduces the QoS issues and support in transport protocols for wireless multimedia transmission. After an overview of the transport... Sample PDF
Transport Protocols and QoS for Wireless Multimedia
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