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.
