Quantitative assessment of voice quality
Avi Perry · Cambridge University Press eBooks · 2006
Chapter 2 kicks off the presentation with an overview of the standard metrics and methodologies followed by a description of specialized tools employed for obtaining subjective voice-quality scores through genuine opinion surveys and via computer modeling emulating human perceptive evaluation of speech quality. It then relates voice-quality scores obtained via surveys or computer evaluations to the perception of worth. It elaborates on the relationships between opinion scores and the potential return on investment in voice-quality technology. It examines results of voice-quality studies with reference to the three popular GSM codecs – full rate (FR), enhanced full rate (EFR) and half rate (HR). The presentation includes a discussion of the effect of noise and transmission errors on the relative performance of these codecs. Introduction It is widely agreed that the most vital element affecting the performance of voice quality in wireless networks is the type of codec used in the communication session. It is also well known that spectrum is the most expensive (per channel) building block contributing to the viability of wireless infrastructure. Yet most European GSM wireless operators, throughout the nineties and the first half of the following decade, have opted to restrict their service offerings to full-rate (FR) or enhanced full-rate (EFR), rather than embracing the half-rate (HR) option, which could cut their spectrum consumption in half and save them millions of dollars in operating expenses.