Relative Permittivity Based Model for GSM Signal Loss in Buildings

Abstract

In this work, measurements of GSM signal strength were conducted in buildings to determine the signal penetration loss through them. This was carried out using Radio Frequency Signal Tracker installed in Tecno N9 tablet. These buildings were made with different materials such as Mud, sandcrete, and alucoboard. The average penetration loss was computed by subtracting the indoor received signal strength from the outdoor received signal strength, the same for both closed and opened doors and windows and the in- building (obstructed) penetration path loss exponent was determined. Based on the measurement data, a path loss model was developed using Snell’s law and byconsidering the free space loss, log-normal loss, the deduced in-building path loss exponent, and the distance between the transmitter and receiver. The developed path loss model was compared with the ITU-R indoor path loss model and a Matlab based user interface for instant path loss prediction was also created. The measurement results indicated that the building with alucoboard wall cladding had the maximum signal penetration loss (104.52 dB) while the sandcrete building with unrusted corrugated iron sheet roof had the minimum signal penetration loss (81.85 dB). The results also showed that the in-building path loss exponent as the signal passed from outdoor to indoor through the building material were from 0.87 to 1.32. The path loss exponent from the transmitter to the receiver varied between 4.87 to 5.32, and the standard deviation between 17.0dB to 17.8dB. The comparison of the developed model to the ITU indoor path loss model showed very close relationship. This work has deduced a path loss exponent for GSM signal penetration in buildings which is dependent on the building material for the first time in Nigeria.