The Effects Of Harmattan Dust And Rainfall On Microwave Signals In Parts Of Ghana

ABSTRACT

Microwave signal attenuation due to harmattan and rainfall are two of the major constraints in selecting microwave bands in Ghana. With customer complaints of signal loss during these seasons, telecommunication companies compensate for sudden losses in signal strength by amplifying the signal wave. This study investigates the effect of harmattan and rainfall on communication link for frequencies ranging from 10 to 100 GHz for two locations in Ghana, namely Axim and Tamale.

Visibility and rain rate measurements were made over a two-year period in these locations (Axim and Tamale). The signal attenuation as a result of harmattan dust was calculated using the Zain Elabdin model for visibilities from measured data. The microwave attenuation was obtained for frequencies ranging from 10 GHz to 100 GHz. The rain attenuation was determined using the ITU-R Specific Attenuation Model for Rain (ITU-R P.838-3) for the design of microwave communication systems.

The results showed that both harmattan dust and rainfall have a significant impact on signal attenuation in parts of Ghana. The effect of attenuation due to harmattan dust was much more evident in Tamale whiles rain attenuation was more evident in Axim.

It was observed that the signal attenuation increased as the radius size increased for frequencies from 10 – 100 GHz.

The signal attenuation due to harmattan dust was calculated for frequencies ranging from 10 – 100 GHz for both Tamale and Axim. The signal attenuation due to harmattan dust increased with increasing frequencies for both locations. Upon comparison, it was observed that Tamale had the higher attenuation values. Axim showed relatively low attenuation values from frequencies of 10 GHz to 100 GHz and ranged from 0.00009 dB/km to 0.03841 dB/km whiles signal attenuation values for Tamale increased from 0.00146 dB/km to a maximum value of 0.6272 dB/km. This graph shows that attenuation due to dust was more prevalent in the Tamale than in Axim.

Furthermore, attenuation values calculated using measured rain rate were highest for high rainfall rates while the lowest attenuation values corresponded to the lowest rainfall rates, as shown in the ITU-R rain attenuation model.