Quality Bounds for Packetized Voice Transport

  • Published 2000


The first term R0 groups the effects of noise, such as background noise and circuit noise. The second term Is includes impairments that occur simultaneously with the voice signal, such as those caused by quantization, by too loud a connection and by too loud a side tone. The third term Id encompasses delayed impairments, including impairments caused by talker and listener echo or by a loss of interactivity. The fourth term Ie covers impairments caused by the use of special equipment; for example, each low bit rate codec has an associated impairment value. This impairment term can also be used to take into account the influence of packet loss. The fifth term A is the expectation factor, which expresses the decrease in the rating R that a user is willing to tolerate because of the “access advantage” that certain systems have over traditional wirebound telephony. As an example, the expectation factor A for mobile telephony (e.g. GSM) is 10. ITU-T draft Recommendation G.109 [7] states that a rating R in the ranges [90,100], [80,90], [70,80], [60,70], [50,60] corresponds to best, high, medium, low and poor quality, respectively. A rating below 50 indicates unacceptable quality. Throughout this article, the classes are color coded according to Table 1. As far as quality is concerned, a packetized voice call introduces more delay and distortion than a traditional STN call. First, the delay for packetized voice calls, where the most important contributions are encoding, packetization, propagation, queuing, service, dejittering and decoding delay, is larger than for a traditional circuitswitched voice call, where the mouthto-ear delay is mainly made up of the Quality bounds for packetized voice transport

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@inproceedings{2000QualityBF, title={Quality Bounds for Packetized Voice Transport}, author={}, year={2000} }