This paper presents the performance evaluation of 3G mobile networks for one kind of multimedia application called Voice over IP (VoIP) within Bangkok, the capital city of Thailand, using Line and Skype, two popular VoIP applications. This study used evaluation of voice quality provided by both applications. The tests have been conducted using stationary scenarios over 5 major 3G mobile networks, served by 5 operators, within 14 universities in the inner city of Bangkok in order to gather data of degraded speech files. Then, the data was measured using Perceptual Evaluation of Speech Quality (PESQ) to find Mean Opinion Score (MOS) before analyzing with ANOVA and T-test, which are statistical tools, so that the discussion and conclusion can be eventually derived.

This paper presents the comparison between two codecs, G.711 and G.722 at 64 kbps, referring to speech quality perception using a subjective method called interview tests. These subjective tests have been conducted with 201 subjects, who are Thai native speakers that use Thai which is a tonal language, for accuracy and reliability of results. The results from testing with both codecs are almost the same; the scores are 4.17 for G.722 and 4.14 for G.711. After analyzing the results, it has been confirmed that G.722 does not provide better speech quality than G.711 to the Thai subjects significantly, which is consistent with previous information. However, these results could be used as the benchmark of G.711 and G.722 for speech quality assessment within Thai environments.