| Abstract [eng] |
The aim of this thesis is to investigate voice quality in Lithuanian mobile networks (Bitė Lietuva, Omnitel, Tele2). The data for research were collected from Anite Nemo Outdoor software from ten cities of Lithuania. The POLQA perceptual measurement algorithm was chosen. Moreover, the paper provides an overview of the audio codecs and call setup-procedure in mobile 2G/3G networks. The thesis describes the key characteristics and network parameters related to bad voice quality. On the basis of the results of this research, it can be concluded that audio codec and its bitrate are main factors for voice quality. Average MOS score using AMR-WB 12.65 codec is 0,4 bigger than using AMR-NB 12.2. Other network parameters related to voice quality: insertion gain, audio quality SNR, Ec/N0, BLER, RSCP, delay, RX quality sub and RX level sub. Structure: introduction, task analysis, review of similar studies, audio codecs, audio codecs implementation in 2G/3G mobile networks, main differences between PESQ and POLQA, experiment and evaluation of results, conclusions, references. Thesis consist of: 64 p. text without appendixes, 61 pictures, 10 tables, 29 bibliographical entries. Appendixes included. |
