Subjective evaluation of voice quality over GSM network for quality of experience (QoE) measurement

Recently, standard of voice quality on Voice Call-one of GSM service, is measured by using standard Quality of Service (QoS). However, according to ministerial of Communication and Information regulation (Permenkominfo) 2008, the guaranteed quality of Voice Call service was Endpoint Service Availability, and not the quality delivered to end-users. In this paper, we proposed a subjective method to measure voice quality valued by the experience of the end-users (Quality of Experience). The proposed method focuses on the degradation of voice quality and intelligibility between caller and receiver. Subjective measurement had been performed by using 2 different method, first method emphasized on measurement of 'Speech intelligibility' and the second one emphasized on measurement reduction of voice quality. To obtain it, we used value of Percent Correct Words and Degradation Mean Opinion Score (DMOS). The measurement objective was measured by using Perceptual Evaluation of Speech Quality (PESQ). The stimuli were recorded during busy hour (Permenkominfo, 2008), to obtain the greatest distortion possible in the GSM Networks. The result of this study was 98.9% in percent correct words, 4.5 in DMOS, and 3.44 in PSEQ. Although PESQ and DMOS does not have the same weight, but the trend seen from both DMOS and PESQ value was proportional with the correlation coefficient = 0.82. Based on the result of those 3 measurement values, the operator 2 had better voice quality than the operator 1. The experimental results suggest that the quality of the two operators are still in the good category (degradation is audible but not annoying) even in busy business hours.