Ayo-Bello, Oluwabukola, et al. “A QOS ESTIMATION ALGORITHM FROM CALLER RINGTONE ANALYSIS IN GSM NETWORK”. International Journal of Software Engineering and Computer Systems, vol. 8, no. 1, May 2022, pp. 53-68, https://doi.org/10.15282/ijsecs.8.1.2022.6.0096.