Power control for mobile radio systems using perceptual speech quality metrics

Behrooz Rohani Mehdiabadi

    Research output: ThesisDoctoral Thesis

    97 Downloads (Pure)

    Abstract

    As the characteristics of mobile radio channels vary over time, transmit power must be controlled accordingly to ensure that the received signal level is within the receiver's sensitivity. As a consequence, modern mobile radio systems employ power control to regulate the received signal level such that it is neither less nor excessively larger than receiver sensitivity in order to maintain adequate service quality. In this context, speech quality measurement is an important aspect in the delivery of speech services as it will impact satisfaction of customers as well as the usage of precious system resources. A variety of techniques for speech quality measurement has been produced over the last few years as result of tireless research in the area of perceptual speech quality estimation. These are mainly based on psychoacoustic models of the human auditory systems. However, these techniques cannot be directly applied for real-time communication purposes as they typically require a copy of the transmitted and received speech signals for their operation. This thesis presents a novel technique of incorporating perceptual speech quality metrics with power control for mobile radio systems. The technique allows for standardized perceptual speech quality measurement algorithms to be used for in-service measurement of speech quality. The accuracy of the proposed Real-Time Perceptual Speech Quality Measurement (RTPSQM) technique with respect to measuring speech quality is first validated by extensive simulations. On this basis, RTPSQM is applied to power control in the Global System for Mobile (GSM) communication and the Universal Mobile Telecommunication System (UMTS). It is shown by simulations that the use of perceptual-based power control in GSM and UMTS outperforms conventional power control in terms of reducing the transmitter signal power required for providing adequate speech quality. This in turn facilitates the observed increase in system capacity and thus offers better utilization of available system resources. To enable an analytical performance assessment of perceptual speech quality metrics in power control, the mathematical frameworks for conventional and perceptual-based power control are derived. The derivations are performed for Code Division Multiple Access (CDMA) systems and kept as generic as possible. Numerical results are presented which could be used in a system design to readily find the Erlang capacity per cell for either of the considered power control algorithms.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2007

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