VOL. 10, NO 21, NOVEMBER, 2015 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences ©2006-2015 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 10096 A MODIFIED EFFECTIVE PATH LENGTH FOR PREDICTING RAIN ATTENUATION BASED ON MEASUREMENTS IN PENANG-MALAYSIA Ali Kadhim Lwas 1 , MD. Rafiqul Islam 1 , Mohamed Hadi Habaebi 1 , Singh Jit Mandeep 2 , Ahmad Fadzil Ismail 1 , Jamal Ibrahim Daoud 3 and Alhareth Zyoud 1 1 Department of Electrical and Computer Engineering, University of International Islamic Malaysia, Jalan Gombak, Kuala Lumpur, Selangor, Malaysia 2 Department of Electrical, Electronic and Systems Engineering, University Kebangsaan Malaysia, Jalan Reko, Bangi, Selangor, Malaysia 3 Department of Science in Engineering, University of International Islamic Malaysia, Jalan Gombak, Kuala Lumpur, Selangor, Malaysia E-Mail: alilawas@yahoo.com ABSTRACT A modification to an effective path length for predicting rain attenuation in Malaysia is proposed in this paper. Due to the scarcity of actual signal measurements at high frequencies-bands in tropical climates make predicted models are key resource for generating rain attenuation. A modification to calculate the effective path length is introduced in the original model. A control parameter rho is also induced based on the rain intensity variations along the slant path. A new value is suggested according to measurements in Malaysia. The results showed that modified rain attenuation model has significantly improved the rain attenuation prediction in Malaysia. Keywords: effective path length, rain attenuation, prediction model. INTRODUCTION Knowledge about the outage probability of a satellite system is essential for any satellite communication system designer. Therefore, it is very important to determine the rain fade characteristics, and analyze the rain attenuation in-depth. Accurate estimation of rain attenuation leads to propose the appropriate and suitable mitigation technique for the rain effect. Any error in the estimation of rain attenuation leads to increase the outage probability and lost the satellite signal for some period of time [1]. Most of the available studies in the literature are conducted in temperate region where rain has different characteristics, thus, such results and analysis proposed by these studies will not be appropriate for tropical regions like Malaysia [2-3]. In temperate regions, the rain cell size is large and the rainfall is moderate while in the tropical regions the cell size is smaller and the rain is convectional [4-7]. The differences between temperate and tropical regions are not only in rainfall rate but also in the rain structure and spatial structure between the Earth base station and the satellite [8]. The rain height in temperate region is less than the rain height in tropical region where it reaches up to 10 km [9]. Evidently, the slant path of satellite signal between the Earth base station and the satellite is a function of the elevation angle. Therefore, the slant path in tropical regions will be subject to strong and higher rainfall rate than in temperate regions. Of course, not the whole path of the satellite signal will be subject to rain. The part of the path that is covered by rain is called the effective length as shown in Figure-1. Based on previous studies, the effective length is a function of elevation angle, rain height, and rainfall rate. Based on the above description, therefore, the effective path length determination models proposed for temperate regions will not be accurate for tropical regions. Furthermore, the rain attenuation prediction models which are proposed based on the data from temperate regions will be unsuitable to be applied in tropical regions too. Therefore, and based on the above description, the effective path length determination models that proposed for temperate regions will not be that accurate for tropical regions. Furthermore, the rain attenuation prediction models which proposed based on data from temperate regions will not suitable also to be applied in tropical regions too. The objectives of this paper are to modify the equation used to calculate the effective path length, and to propose control parameters of variation intensity in Malaysia. To meet these objectives, rain rate and rain attenuation were measured concurrently at University Science Malaysia (USM) campus (5.17° N, 100.4° E) and were used to test the modified model. This paper shows very promising results for the rain attenuation prediction in tropical regions.