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The E-model The E-model is the idea and culmination of the career of Nils-Olof Johanesson who was a lifelong Swedish expert in ITU-T and latterly in ETSI. It was developed jointly by ETSI TM5, TE4 & BTC2 between 1993 to 1996 and is described in ETR 250 (July 96). The purpose of the model is: to predict the subjective effect of combinations of impairments using stored information on the effects of individual impairments to help network planners design networks to replace hierarchical models and apportionment, which are difficult to apply in a liberalized market The basic principle of the model is that: "Psychological factors on the psychological scale are additive." The model works in transmission ratings (R) which are related to the Mean Opinion Score (MOS). The basic equation for the model is:    R = Ro - Is - Id - Ie + A where: Ro =S/N at 0 dBr point. Is = Impairments simultaneous to voice signal Id = Impairments delayed after voice signal Ie = Effects of special equipment e.g. codecs A = Advantage factor (to take account of user advantages such as mobility) Windows based computer implementations of the model, with exceptionally well represented user interfaces, have been developed by Peter Meschkat, latterly an Alcatel representative in ETSI. There are two different versions of the model : Version for end-end performance estimation (to support ETR 250) Speech Communication Quality Mouth To Ear for Windows - short 'SCQME' Order no: 3AV 00019 5044 Price: 98 EURO Version for network planning (to support EG 201 050) Overall Transmission Plan Aspects for Telephony in a Private Network - short 'TPE' Order no: 3AV 00019 5050 Price: 148 EURO Both models can be purchased from: Alcatel SEL AG, Business Systems Division c/o Mr. Loew, Dep. PS/OLMB Motorstrasse 55, D-70499 Stuttgart, Germany Telephone +49 711 821 35444 Telefax +49 711 821 35431 You can download a presentation on the E-model PDF 175k  or Powerpoint97  540k

Last updated: 2008-07-07 13:33:33