Rain fade dynamics for Ka-band satellite communication mitigation technique in equatorial Malaysia

Abstract

Modern satellite communication system in higher frequency (Ka-band and above) is very much impaired by rain attenuation particularly in tropical and equatorial region. The desired Quality of Service (QoS) and system availability can be guaranteed only by resorting to smart strategies, named Propagation Impairment Mitigation Techniques (PIMTs) such as power control, adaptive modulation schemes and link diversity. These requires knowledge of the first- and second-order statistics of rain attenuation. Hence, this work concentrates on those aspects in equatorial Johor Bahru, Malaysia, based on one year Ka-band propagation measurement campaign, utilizing the equipment of Beacon Receiver and 2D-Video-Disdrometer (2DVD). Study begins by investigation the rain fade behaviour such as rain attenuation, fade duration, inter-fade duration and fade slope as well as their seasonal and diurnal variations. It is observed that rain attenuation experienced by the Ka-band link requires fade margin of 26.8 dB for 99.9% link availability with the convective events mostly like to occur during the afternoon hour (12:00 pm to 6:00 pm) at high intensity, shorter duration and relatively high rate of change of attenuation particularly during Northeast Moonsoon. Then, the Stratiform Convective-Synthetic Storm Technique (SC-SST) is proposed to estimate the dynamic characteristics of rain attenuation in equatorial region. The SC-SST is found 11% better than SST and 51% better than ITU-R P.1623-1 model in average value of fade dynamics prediction. Finally, a time diversity technique is recommended to mitigate strong signal fades in equatorial region. The results depicted that 10-minute outage tolerance will significantly lower the fade margin requirement to 15 dB for 99.9% of link availability. Afterwards, the generation of time diversity statistics is modelled which can be best represents by gamma-law in this area. The results can provide system engineers with critical information in the design and implementation of PIMTs, and it is expected that the probability of system outages will be greatly reduced.