Scalable voip mobility intedration and deployment- P7: The term voice mobility can mean a number of different things to different people. Two words that can be quite trendy by themselves, but stuck together as if forgotten at a bus station long past the last ride of the night, the phrase rings a number of different, and at times discordant, bells. | Elements of Voice Quality 59 equipment being measured. PESQ then returns with the expected mean opinion score a group of real listeners are likely to have thought. PESQ uses a perceptual model of voice much the same way as perceptual voice codecs do. The two audio samples are mapped and remapped until they take into account known perceptual qualities such as the human change in sensitivity to loudness over frequency sounds get quieter at the same pressure levels as they get higher in pitch . The samples are then matched up in time eliminating any absolute delay which affects the quality of a phone call but not a recording. The speech is then broken up into chunks called utterances which correspond to the same sound in both the original and distorted recording. The delays and distortions are then analyzed counted and correlated and a number measuring how far removed the distorted signal is from the original signal is presented. This is the PESQ score. PESQ is our first entry into the area of mathematical or algorithmic determination of call quality. It is good for measuring how well a new codec works or how much noise is being injected into the sample. However because it requires comparing what the talker said and what the listener heard it is not practical for real-time call quality measurements. Voice Over IP The E-Model How can we have access to a way of measuring the quality of voice over IP networks measuring the contribution to the distortion caused uniquely by the voice mobility network Once again the ITU is here to the rescue. ITU introduces the E-model a computational model that takes into account measurable network effects to determine the call quality that should have been expected for the call as seen on the network. The output of the E-model is what is known as an R-value a number on a scale from 0-100 similar to that used to produce letter grades in high school. The structure is as follows 90 and up Very Satisfied 80 -90 Satisfied 70 -80 .
