Effects of lower sampling interval on rainfall queue characteristics over radio links in South Africa

Rain attenuation is a major problem on millimeter wave propagation especially around subtropical, tropical and equatorial regions in Africa. Previous research has determined that rainfall characteristics over sub-tropical and equatorial regions in Africa are essentially a queue process following an M/E
_k
/s/∞/FCFS queue discipline. Rainfall measurements consisting of 2000 observable rain spikes were retrieved from the disdrometer for the investigation of the queue parameters at 30-second sampling time in Durban (29°52'S, 30°58'E). The retrieved rainfall data is classified into four rain rate regimes namely: drizzle, shower, widespread and thunderstorm. Queue parameters required for rainfall traffic analysis - such as inter-arrival time and service time - are empirically determined to be Erlang-k distributed, whereas overlap time is Exponentially distributed. It is thus established that the queue discipline for the rainfall spikes over millimeter wave is E
_k
/E
_k
/s/∞/FCFS. Conclusively, rainfall events at 30-second and one-minute sampling behave as a semi-Markovian process. In this light, lower sampling time gives accurate results, since we see more rainfall spikes on the 30-second queue parameters.