INVESTIGATION OF MULTIPATH PROPAGATION AND FADE STATISTICS IN THE COASTAL AREA OF NIGERIA

Abstract

Multipath propagation is one of the factors that causes radio signal degradation. The irregularity of the atmosphere causes variation of Point Refractive Gradient (PRG) with height and time of the day as well as season. This variation provides information on the occurrence of multipath propagation, which often leads to signal fading. This study investigates multipath propagation and fading in the coastal area of Nigeria, using five (5) years (Jan 2014-Dec 2018) reanalysis data, obtained from the archives of European Center for Medium-Range Weather Forecasts (ECWMF). The primary atmospheric parameters of temperature, relative humidity, and pressure were obtained both at surface and at 110 m height, for seven (7) locations in the coastal region of Nigeria: Badagry, Port-Harcourt, Ekeremor, Burutu, Ibeno, Ilaje, Akpabuyo. The Point refractivity gradient, the geoclimatic factor (K), fade statistics and the percentage of time that a certain fade depth leads to signal outage were estimated using the ITU-R P530-17 recommendation. The results show that the value of surface radio refractivity during the dry season months is higher than the values during the wet season months; this is attributed to the dry term of refractivity (Ndry), which clearly contributed about 90% of the computed refractivity, where wet term contributes 10%. The cumulative distribution of refractivity gradient estimated shows that super-refractivity dominates in all locations considered. The result of PRG and K further shows that the worst propagation condition occurs mostly in the rainy season except for Badagry and Ilaje that have their worst propagation condition in the dry season. Based on the Inverse Distance Weighting (IDW) spatial interpolating technique, contour maps were developed for geoclimatic factor K over the coastal area of Nigeria. The results of geoclimatic factor will provide information necessary for prediction of signal outages, due to multipath propagation associated with line of sight link in the region.