Danladi Ali and  Onah Festus Iloabuchi,  Wavelet Based Residual Method of Detecting GSM Signal Strength Fading.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2014, vol. 93(9). 1633 - 1636
    [viewed 15 August 2020]. Available from: https://publications.waset.org/pdf/9999464.