The relevance of the CLP measure of a VoIP system with regard to QoV
Daniel Riordan, Pat Doody · 2008
Communication systems are undergoing constant and rapid innovation, both at the design stage and in the field. This in turn has led to an increasing need for fast, efficient, portable and economic methods for the testing of these systems. For voice carrying communication systems the quality of the transmitted voice that the system produces is a large factor in the systems overall performance rating. This measure is known as the 'Quality of Voice' (QoV) and can be evaluated either subjectively or objectively. Speech quality is a complex subjective phenomenon that can be best quantified by subjective testing. A subjective QoV measurement requires a 'listener' to rate a sample of speech produced by the system under test. To achieve accurate results an average rating, or Mean Opinion Score (MOS), must be found from a large panel of listeners. This results in subjective QoV testing being a highly expensive and time consuming process to conduct. This has driven the requirement for automated objective QoV testing systems which can operate efficiently and cost-effectively. The method described here aims to increase the efficiency of a previously established Non-intrusive objective QoV estimation system designed for use with a VoIP based network. The existing system takes as its inputs four operational parameters (Conditional and Unconditional Packet Loss Probabilities, Codec Type and Speaker Gender) of the communication system under test. These parameters are then mapped to a QoV score. This paper will identify the Conditional Loss Probability (CLP) parameter as being of least significance with regard to the QoV score achieved by the VoIP network. A similar QoV estimation system will then be developed with the CLP measure eliminated. This system will be tested to demonstrate that a system taking only three operational parameters of a VoIP system can still maintain a high degree of accuracy.