Estimation of Rain Attenuation based on ITU-R Model in Guntur (A.P), India

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1 Etimation of Rain Attenuation baed on ITU-R Model in Guntur (A.P, India M. Sridhar,K. Padma Raju, and Ch. Srinivaa Rao 3 Department of ECE, KL Univerity, Guntur, India ridhar.m@kluniverity.in Department of ECE, JNTU Kakinada, Kakinada, India padmaraju_k@yahoo.com 3 Department of ECE, Sri SaiAditya Intitute of Science & Technology, Surampalem, India ch_rao@rediffmail.com Abtract Satellite communication ytem operating at Ku (/4 GHz and Ka band (0/30 GHz frequencie are ued for broadband multimedia and internet baed ervice. At thee frequencie, the ignal will be affected by variou propagation impairment uch a rain attenuation, cloud attenuation, tropopheric cintillation, ionopheric cintillation, water vapour attenuation, and rain and ice depolarization. Among all the propagation impairment, rain attenuation i the mot important and critical parameter. In thi paper, rain attenuation i calculated at KL Univerity, Guntur uing ITU-R rain attenuation model. The preliminary reult of the work will be ued to calculate the attenuation experimentally and comparion can be made, which help to develop a new rain attenuation model at Ku and Ka band. Index Term atellite communication, propagation impairment, rain attenuation, ITU-R model, rain fall rate I. INTRODUCTION Communication ytem deign require the development of a link budget between the tranmitter and the receiver that provide an adequate ignal level at the receiver demodulator to achieve the required level of performance and availability []. The performance and availability of the link can be pecified or meaured uing Bit Error Rate (BER and Carrier-to-Noie ratio (C/N. It i the link deigner tak to enure that lo of ignal occur for no longer than the time permitted for that ervice. The development of an accurate link budget, which include loe due to the paage of the ignal through the atmophere, i critical. There are many phenomena that lead to ignal lo on tranmiion through the earth atmophere. Thee include: cloud attenuation, tropopheric cintillation, ionopheric Scintillation, Water vapour attenuation, rain and ice depolarization, and rain attenuation [].Among all the propagation impairment, rain attenuation i the mot important for frequencie above 0 GHz, a it caue M. Sridhar i with KL Univerity, Guntur, Andhra Pradeh, India ( ridhar.m@kluniverity.in. Dr. K. Padma Raju i preently working a Principal, Univerity College of Engineering, JNTU Kakinada, Kakinada, Andhra Pradeh, India ( padmaraju_k@yahoo.com. Dr. Ch. Srinivaa Rao i working a Principal, Sri Sai Aditya Intitute of Science & Techology, Surampalem, Andhra Pradeh, India ( ch_rao@rediffmail.com. 6 maximum attenuation and therefore, i the limiting factor in Ku and Ka band atellite link deign [3]. The rain drop aborb mot of the electromagnetic energy at thee frequency range and ome of the energy get cattered by Rayleigh and Mie cattering mechanim [4]. The rain drop ize ditribution i exponential when expreed mathematically a, ( N ( D N 0e D Dm mm - m -3 ( where D i the median drop diameter and i the m N( DdD number of drop per cubic meter with diameter between D and D + dd mm [5]. The rainfall rate R i related to N (D and alo to the terminal velocity of V (D the falling drop in meter per econd with diameter D by 3 3 R D V ( D N ( D dd mm/hr ( A. Rain Attenuation Prediction Model The amount of fading due to rain i a function of the frequency and i highly correlated with rain rate. By uing rain tatitic for a given region, it i poible to determine the probability that a given fade depth will be exceeded. The rain availabilityof a communication link i the complement of the probability of the link fade margin being exceeded [6]. Rain fade mitigation technique like power control, ignal proceing and ite diverity method are ued to improve the performance of link deign and thi require proper prediction of attenuation due to rain [7]. There are two approache to predict the rain attenuation namely, a phyical method in which rain i decribed all the way along the path, and an empirical method which ue the effective path length and rainfall rate uing the information from variou data bae [8]. Variou rain attenuation prediction model are available baed on the geographical and climatic condition. The important model are Crane global model [9], Two-component model [0], Simple Attenuation model (SAM, Excell model, MimeWaldteufel model, Garcia model [], International Telecommunication Union Radio Communication ector (ITU-R model [], Bryant model, Dianayake, Allnutt and Haidara (DAH model [], and Moupfouma model []. Among thee model, ITU-R model provide the mot accurate tatitical etimate of attenuation on lant path []. B. ITU-R P Rain Attenuation Model The ITU Radio communication Sector (ITU-R i one

2 among the three diviion of the International Telecommunication Union (ITU which i reponible for radio communication. It manage the international radiofrequency pectrum and atellite orbit reource and alo enhance tandard for radio communication ytem with the objective of enuring the effective ue of the pectrum. The ITU-R provide global rain tatitic by dividing the earth into rain region and aigning a rain rate to each region along with the probability of that rain rate being exceeded [6]. Thi model ue the rain rate at % probability level for the etimation of attenuation and then applie an adjutment factor to the predicted rain fade depth for other probabilitie. It can be ued for the frequencie from 4-55 GHz and % percentage probability range. It i baed on log-normal ditribution and both rain intenity and path attenuation ditribution conform to the ame log-normal ditribution. Inhomogeneity in rain in both horizontal and vertical direction i conidered in the prediction [3]. II. METHOD FOR ESTIMATION OF RAIN ATTENUATION The propoed experimental etup i at KL Univerity, Guntur which i located 9.08 m above ea level. The latitude and longitude of the location are 6.46' N and 80.54' E repectively. Two DTH receiver operating in Ku band i intalled in the location which receive the ignal from NSS6 atellite ( 95 E. A didrometer can be ued to meaure and record the rainfall intenity (mm/hr with -min integration time which alo pecifie rain drop ize. The atellite ignal trength will be meaured uing a pectrum analyzer and the information can be recorded with a data logger. The rainfall rate exceeding % of an average year in mm/hr for the location i calculated uing Recommendation ITU-R P which require the coordinate of the location. The input parameter requiredto thi model are: point rainfall rate for % of an average year (mm/hr with -min integration time, height of the location above mean ea level (Km, elevation angle of the receiver (degree, latitude of the location (degree, frequency (GHz, polarization angle (degree, and effective radiu of the Earth (Km [4]. Table I give the geographical and experimental parameter for the experimental ite. TABLE I. GEOGRAPHICAL/EXPERIMENTAL PARAMETERS FOR THE LOCATION Latitude N Longitude E Height Above Sea Level 0.09 Km Elevation Angle Polarization Angle A. Calculation of Attenuation baed on ITU-R Model Fig. how the chematic repreentation of earth pace path link and the detail of the parameter ued in the model. Baed on the geographical condition and meaured rainfall uing the didrometer, the rain attenuation can be calculated uing ITU-R P model in the following 7 manner [5]: Step. Calculate the rain height recommendation ITU-R P.839 a hr (Kmfrom the h Km ( where h 0 i the 0 C iotherm height above mean ea level at the deired location [6]. Figure. Schematic preentation of an earth-pace path A: Frozen precipitation B: Rain Height C: Liquid precipitation D: Earth-Space path Step. Determine the lant-path length L, below the rain height from ( hr h L Km if 5 in (4 where i Elevation angle in degree, h i the height of the location above ea level in Km, and h R i the rain height in Km. Step 3. Obtain the horizontal projection, L G, of the lant path length from L L co Km (5 G Step 4. Determine the rainfall rate, R,exceeded for % of an average year, with -min integration time. It can be calculated with the help of tatitical data available in variou meteorological databae or from the map provided by ITU-R P.837. Step 5. Calculate the pecific attenuation, R, by uing the frequency dependent regreion coefficient provided in ITU-R P.838 Recommendation and uing [7], k k( R R R db/km (6 where and depend on frequency, polarization, raindrop ize ditribution and temperature and obtained uing, k H kv ( k H kv co co( t k (7 kh H kvv ( kh H kvv co co( t (8 k where t i the polarization tilt angle relative to horizontal. Step 6. Determine the horizontal path adjutment factor, for % of the time uing r 0.0 L f h R G R LG e r (9

3 where f i the frequency in GHz. Step 7. Calculate the adjuted rainy path length, through rain uing LG r LR for co (Km, ( hr hs LS for where in ( hr hs tan LG r ( Step 8. Obtain the vertical reduction factor v, for % of the time by uing v (3 / LR R in 3( e 0.45 f where 36, for 36 (4 0, for 36 (5 Step 9. Determine the effective path length through rain, (Km, given by L (6 E LRv Step 0. Calculate the predicted attenuation exceeded for % of an average year by uing A db (7 RLE Step. The etimated attenuation to be exceeded for the other percentage of an average year, in the range 0.00% to 0% may then be etimated uing A a ( p ln ( p ln ( A in ( p A p A (8 where p i the percentage probability of interet and i given by for for p %, 0 p %, 0 if 36 (9 ( ( 36 for 5 and 36 ( III. RESULTS AND DISCUSSION ( ( in, ( for 5 and 36 The theoretical value for rain attenuation are calculated for different rainfall rate uing ITU-R model at KL Univerity. The DTH receiver intalled in the ite operate in Ku band whoe elevation angle i The rainfall rate are calculated baed on the geographical latitude and longitude, and will be ued to meaure attenuation at different frequencie [5]. Table II give the variation of rainfall rate and attenuation with repect to % time exceeded of an average year at GHz. The rainfall rate i calculated uing the ITU-R P Recommendation and the variation of the rainfall rate (mm/hr i a hown in Fig., for different exceedence percentage. At GHz operating frequency, it can be oberved that the maximum rainfall rate i 5.89 mm/hr at 0.00% time of an average year. The rainfall rate i 6.83 mm/ hr exceeded for % of an average year, with -min L R L E 8 TABLE II.VARIATION OF RAINFALL RATE AND ATTENUATION WITH RESPECT TO % TIME EXCEEDED % Time Rainfall Rate Attenuation exceeded (mm/hr (db 0.00% % % % % 0 0 integration time. The obtained rainfall rate with different % time exceedence of average year will be compared and tudied with practical rainfall rate meaured with didrometer arrangement a a next tep in the reearch work. Figure..Variation of rainfall rate (mm/hr with repect to % time exceeded The attenuation of the ignal i obtained at GHz frequency, uing ITU-R P Recommendation for different rainfall rate. It i evident from Fig. 3 that the attenuation increae with rainfall rate. The theoretical reult will be ued to tudy and compare the amount of attenuation introduced practically in the extended future reearch work. Figure. 3. Variation of attenuation with repect to rainfall rate The attenuation i calculated for frequencie from GHz to

4 5 GHz with a rainfall rate R mm/hr uing ITU R model. With an increae in frequency, there i a ignificant increae in the attenuation a hown in Fig. 4. The attenuation i db at GHz frequency and.39 db at 5 GHz. rain attenuation i the predominant. In thi paper, ITU-R model i ued to predict the rainfall rate and attenuation due to rain, at KL Univerity, Guntur. The attenuation i calculated, for different rainfall rate and exceedence percentage of an average year. The preliminary reult indicate that the attenuation increae with frequency and rainfall rate. Thee predicted value can be compared with the meaured experimental data after intallation of the etup in the location. ACKNOWLEDGMENTS The author wih to thank Dr. K. Sarat Kumar, Aociate Dean, Sponored Reearch and Dr. D. Venkata Ratnam, KL Univerity for their valuable uggetion. Thi work wa upported in part by a grant from Department of Science and Technology, New Delhi, India. REFERENCES Figure.4. Rain Attenuation Variation with Frequency at Rainfall Rate mm/hr R 6.83 The rain attenuation i calculated for 0.00% to 5% exceedence percentage of an average year a hown in Fig. 5. The attenuation i 5.8 db with 0.00% and 0 db with 5% exceeded time of an average year. The rainfall rate (mm/hr for the location i obtained from India Meteorological Department and tudied for five conecutive year from The tatitical analyi i done by calculating cumulative ditribution function for every month uing MATLAB and it ha been oberved that the rainfall rate i maximum and for more duration during July and Auguta hown in Fig. 6. and hence the rain attenuation will be predominant during the above period. Figure. 5. Variation of Rain Attenuation with Repect to % Time Exceeded DOI: 0.IJCOM IV. CONCLUSIONS Due to the pectral congetion of frequency band allotted and requirement of higher bandwidth, the importance of higher frequency band like Ku band ( /4 GHz and Ka band ( 0/30 GHz i becoming more predominant nowaday for atellite communication ervice. At thee frequencie, variou impairment will caue the ignal to fade, among which 9 [] Pratt, T., C. W. Botian, and J. E. Alnutt, Satellite Communication, John Wiley and Son, 003,536 pp. [] Cot Action 55 Final Report, Radiowave Propagation Modelling for SatCom Service at Ku-Band and Above, ESA Publication Diviion, Noordwijk, The Netherland, 00. [3] K. P. Lioli, A. D. Panagopoulo, and S. Scalie, On the combination of tropopheric and local environment propagation effect for mobile atellite ytem above 0 GHz, IEEE Tran. Veh. Technol., vol. 59, no. 3, pp. 09 0, Mar. 00. [4] Timothy, K. I.; Ong, J. T. &Choo, E. B. L. (00, Raindrop Size Ditribution Uing Method of Moment for Terretrial and Satellite Communication Application in Singapore, IEEE Tranaction on Antenna and Propagation, Vol. 5, No. 0, October 00, 40-44, ISSN: X. [5] Maitra A., Rain Attenuation Modeling From Meaurement of Rain Drop Size Ditribution in The Indian Region, IEEE Antenna and Wirele Propagation Letter. Vol. 3, P. 80 8, 004. [6] John S. Seybold, Introduction to RF Propagation, John Wiley & Son, 005. [7] Athanaio D. Panagopoulo, Panteli - Daniel M. Arapoglou, and Panayoti G. Cotti, Satellite Communication at Ku, Ka, and V Band: Propagation Impairment and Mitigation Technique, IEEE Communication urvey, Volume 6, No.3, 004. [8] Ojo, J. S., M. O. Ajewole, and S. K. Sarkar, Rain rate and rain attenuation prediction for Satellite Communication in Ku and Ka band over Nigeria, Progre in Electromagnetic Reearch B, Vol. 5, 07-3, 008. [9] R. K. Crane, Prediction of attenuation by rain, IEEE Tran. Commun., vol. 8, pp , Sept [0] R. K. Crane and H. C. Shieh, A two-component rain model for the prediction of ite diverity improvement performance, Radio Sci., vol. 4, no. 6, pp , 989. [] A. Dianayake, J. Allnutt, and F. Haidara, A Prediction Model that Combine Rain Attenuation and other Propagation Impairment along Earth-Satellite Path, IEEE Tran. Antenna Propag., vol. 45, no. 0, 997, pp [] Moupfouma F., Martin L. Modelling of the rainfall rate cumulative ditribution for the deign of atellite and terretrial communication ytem, International J. of Satellite Comm.,

5 995. Vol. 3. P [3] Dong You Choi, Jae Young Pyun, Sun Kuh Noh, and Sang Woong Lee, Comparion of Meaured Rain Attenuation in the.5 GHz Band with Prediction by the ITU-R Model, International Journal of Antenna and Propagation, Hindawi Publiher, 0. [4] International Telecommunication Union, Characteritic of precipitation for propagation modeling, Recommendation ITU- R, P.837-5, Geneva 007. [5] ITU-R P.68-9, Propagation data and prediction method required for the deign of earth-pace telecommunication ytem, International Telecommunication Union, Geneva, Switzerland, 007. [6] Rain height model for prediction method, Recommendation ITU-R P.839-3, ITU-R P Ser., Int. Telecomm. Union, Geneva, 00. [7] Specific attenuation model for rain for ue in predictionmethod, Recommendation ITU-R P.838-3, ITU- R P Ser., March 005. BIOGRAPHIES M. Sridhar received B. Tech degree from Acharya Nagarjuna Univerity, Guntur, India in 00 and M.Tech degree from Jawaharlal Nehru Technological Univerity, Anantapur, India in 009. He i a Member of The Intituition of Electronic and Telecommunication Engineer (IETE and preently working a an Aociate Profeor in KL Univerity, Guntur, India. He i puruing Ph.D in Jawaharlal Nehru Technological Univerity Kakinada, Kakinada, India and hi reearch area of interet i Satellite Communication. He i having year of teaching experience. K.Padma Raju received B.Tech from Nagarjuna Univerity, M. Tech from NIT Warangal, Ph. D from Andhra UniverityIndia and Pot-Doctoral Fellowhip at Hoeo Univerity, South Korea. He ha worked a Digital Signal Proceing Software Engineer in Signion Sytem Pvt. Ltd., Hyderabad, India, before joining Jawaharlal Nehru Technological Univerity Kakinada, India.He ha 7 year of teaching experience and i Profeor of Electronic andcommunication Engineering, Jawaharlal Nehru Technological Univerity Kakinada, India. Preently he i working a Principal, Univerity College of Engineering, Jawaharlal Nehru Technological Univerity Kakinada, India.He worked a Reearch Profeor at Hoeo Univerity, South Korea during He ha publihed 30 technical paper in National/International Journal/Conference proceeding and guiding 06 reearch tudent in the area of Antenna, EMI/ EMC and Signal Proceing Hi field of interet are Signal Proceing Miicrowave and Radar Communication and EMI/ EMC. Ch. Srinivaa Rao i currently working a Profeor of Electronic & Communication Engineering, Sri SaiAditya Intitute of Science & Technology, Surampalem, Andhra Pradeh, India. He obtained Ph. D from Univerity College of Engineering, Jawaharlal Nehru Technological Univerity Kakinada, Kakinada, Andhra Pradeh, India in 009. He received M. Tech. degree from JNTU, Hyderabad and B. Tech from Nagarjuna Univerity. He ha International Journal, Conference Publication and one Monograph to hi credit. He i guiding 06 reearch tudent in Digital Image/Signal Proceing and Communication Engineering. Dr. Rao i a Fellow of IETE and member of IEEE & CSI. Figure. 6. Cumulative Ditribution Function of Rainfall rate during in Guntur 0