ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012Estimation of Rain Attenuation based on ITU-R Model             ...
ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012among the three divisions of the International                  ...
ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012where f is the frequency in GHz.                                ...
ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012 15 GHz with a rainfall rate 0.01  62.83 mm/hr using ITU-      ...
ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012     1995. Vol. 13. P. 105–115.                                 ...
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Estimation of Rain Attenuation based on ITU-R Model in Guntur (A.P), India


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Satellite communication systems operating at Ku
(12/14 GHz) and Ka band (20/30 GHz) frequencies are used
for broadband multimedia and internet based services. At these
frequencies, the signal will be affected by various propagation
impairments such as rain attenuation, cloud attenuation,
tropospheric scintillation, ionospheric scintillation, water
vapour attenuation, and rain and ice depolarization. Among
all the propagation impairments, rain attenuation is the most
important and critical parameter. In this paper, rain
attenuation is calculated at KL University, Guntur using
ITU-R rain attenuation model. The preliminary results of the
work will be used to calculate the attenuation experimentally
and comparison can be made, which helps to develop a new
rain attenuation model at Ku and Ka bands.

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

  1. 1. ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012Estimation of Rain Attenuation based on ITU-R Model in Guntur (A.P), India M. Sridhar1,K. Padma Raju2, and Ch. Srinivasa Rao3 1 Department of ECE, KL University, Guntur, India Email: 2 Department of ECE, JNTU Kakinada, Kakinada, India Email: 3 Department of ECE, Sri SaiAditya Institute of Science & Technology, Surampalem, India Email: ch_rao@rediffmail.comAbstract — Satellite communication systems operating at Ku maximum attenuation and therefore, is the limiting factor in(12/14 GHz) and Ka band (20/30 GHz) frequencies are used Ku and Ka band satellite link design [3].for broadband multimedia and internet based services. At these The rain drops absorb most of the electromagnetic energy atfrequencies, the signal will be affected by various propagation these frequency ranges and some of the energy gets scatteredimpairments such as rain attenuation, cloud attenuation, by Rayleigh and Mie scattering mechanisms [4]. The raintropospheric scintillation, ionospheric scintillation, water drop size distribution is exponential when expressedvapour attenuation, and rain and ice depolarization. Amongall the propagation impairments, rain attenuation is the most mathematically as, ( D )important and critical parameter. In this paper, rain N ( D )  N 0 e Dm mm-1m-3 (1)attenuation is calculated at KL University, Guntur using where Dm is the median drop diameter and N(D)dD is theITU-R rain attenuation model. The preliminary results of the number of drops per cubic meter with diameters between Dwork will be used to calculate the attenuation experimentally and D + dD mm [5]. The rainfall rate R is related to N (D) andand comparison can be made, which helps to develop a new also to the terminal velocity of V (D) the falling drops inrain attenuation model at Ku and Ka bands. meters per second with diameter D byIndex Terms — satellite communication, propagation R  0.6  10 3  D 3V ( D ) N ( D ) dD mm/hr  (2)impairments, rain attenuation, ITU-R model, rain fall rate A. Rain Attenuation Prediction Models The amount of fading due to rain is a function of the I. INTRODUCTION frequency and is highly correlated with rain rate. By using Communications system design requires the development rain statistics for a given region, it is possible to determineof a link budget between the transmitter and the receiver that the probability that a given fade depth will be exceeded. Theprovides an adequate signal level at the receiver ’s rain availabilityof a communication link is the complement ofdemodulator to achieve the required level of performance the probability of the link fade margin being exceeded [6].and availability [1]. The performance and availability of the Rain fade mitigation techniques like power control, signallink can be specified or measured using Bit Error Rate (BER) processing and site diversity methods are used to improveand Carrier-to-Noise ratio (C/N). It is the link designer’s task the performance of link design and this requires properto ensure that loss of signal occurs for no longer than the prediction of attenuation due to rain [7]. There are twotime permitted for that service. The development of an approaches to predict the rain attenuation namely, a physicalaccurate link budget, which includes losses due to the method in which rain is described all the way along the path,passage of the signal through the atmosphere, is critical. and an empirical method which uses the effective path lengthThere are many phenomena that lead to signal loss on and rainfall rate using the information from various data basestransmission through the earth’s atmosphere. These include: [8]. Various rain attenuation prediction models are availablecloud attenuation, tropospheric scintillation, ionospheric based on the geographical and climatic conditions. TheScintillation, Water vapour attenuation, rain and ice important models are Crane global model [9], Two-componentdepolarization, and rain attenuation [2].Among all the model [10], Simple Attenuation model (SAM), Excell model,propagation impairments, rain attenuation is the most MismeWaldteufel model, Garcia model [1], Internationalimportant for frequencies above 10 GHz, as it causes Telecommunication Union Radio Communication sector M. Sridhar is with KL University, Guntur, Andhra Pradesh, India (ITU-R) model [2], Bryant model, Dissanayake, Allnutt and(email: Haidara (DAH) model [11], and Moupfouma model [12]. Dr. K. Padma Raju is presently working as Principal, University Among these models, ITU-R model provides the mostCollege of Engineering, JNTU Kakinada, Kakinada, Andhra Pradesh, accurate statistical estimate of attenuation on slant paths [2].India (email: Dr. Ch. Srinivasa Rao is working as Principal, Sri Sai Aditya Insti- B. ITU-R P. 618 - 9 Rain Attenuation Modeltute of Science & Techology, Surampalem, Andhra Pradesh, India The ITU  Radio  communication  Sector (ITU-R)  is  one(© 2012 ACEEE 6DOI: 01.IJCOM.3.2. 4
  2. 2. ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012among the three divisions of the International manner [15]:Telecommunication Union (ITU) which is responsible Step 1. Calculate the rain height h R(Km)from thefor radio communication. It manages the international radio- recommendation ITU-R P.839 asfrequency spectrum and satellite orbit resources and alsoenhances standards for radio communication systems with hR  h0  0.36 Km (3)the objective of ensuring the effective use of the spectrum. where h 0is the 0° C isotherm height above mean sea level at The ITU-R provides global rain statistics by dividing the the desired location [16].earth into rain regions and assigning a rain rate to each regionalong with the probability of that rain rate being exceeded[6]. This model uses the rain rate at 0.01% probability levelfor the estimation of attenuation and then applies anadjustment factor to the predicted rain fade depth for otherprobabilities. It can be used for the frequencies from4 - 55 GHz and 0.001 - 5% percentage probability range. It isbased on log-normal distribution and both rain intensity andpath attenuation distribution conform to the same log-normaldistribution. Inhomogeneity in rain in both horizontal andvertical directions is considered in the prediction [13]. Figure 1. Schematic presentation of an earth-space path II. METHOD FOR E STIMATION OF RAIN ATTENUATION A: Frozen precipitation The proposed experimental setup is at KL University, B: Rain HeightGuntur which is located 29.08 m above sea level. The latitude C: Liquid precipitation D: Earth-Space pathand longitude of the location are 16.46 N and 80.54 Erespectively. Two DTH receivers operating in Ku band is Step 2. Determine the slant-path length L s , below the raininstalled in the location which receives the signal from NSS6 height fromsatellite ( 95 E). A disdrometer can be used to measure and ( h  hs ) Ls  R Km if   5 (4)record the rainfall intensity (mm/hr) with 1-min integration sin where  is Elevation angle in degrees,h s is the height of thetime which also specifies rain drop size. The satellite signal location above sea level in Km, and h Ris the rain height in Km.strength will be measured using a spectrum analyzer and the Step 3. Obtain the horizontal projection, LG , of the slant pathinformation can be recorded with a data logger. The rainfall length fromrate exceeding 0.01% of an average year in mm/hr for thelocation is calculated using Recommendation ITU-R P. 837-5 LG  Ls cos  Km (5)which requires the coordinates of the location. The input Step 4. Determine the rainfall rate, R0.01 ,exceeded for 0.01%parameters requiredto this model are: point rainfall rate for of an average year, with 1-min integration time. It can be0.01% of an average year (mm/hr) with 1-min integration time, calculated with the help of statistical data available in variousheight of the location above mean sea level (Km), elevation meteorological databases or from the maps provided byangle of the receiver (degrees), latitude of the location ITU-R P.837.(degrees), frequency (GHz), polarization angle (degrees), and Step 5. Calculate the specific attenuation,  R , by using theeffective radius of the Earth (Km) [14]. Table I gives the frequency dependent regression coefficients provided ingeographical and experimental parameters for the experimental ITU-R P.838 Recommendation and R0.01 using [17],site. TABLE I. GEOGRAPHICAL/EXPERIMENTAL PARAMETERS FOR THE LOCATION  R  k ( R0.01 ) dB/Km (6) Latitude 160.46’N where k and  depend on frequency, polarization, raindrop size distribution and temperature and obtained using, Longitude 80 0.54’E  k H  kV  ( k H  kV ) cos 2  cos(2 t )  Height Above Sea Level 0.029 Km k   (7) 2 Elevation Angle 64.5 0  k H  H  kV  V  ( k H  H  kV  V ) cos 2  cos(2t )    (8)  Polarization Angle 40.4 0 2kA. Calculation of Attenuation based on ITU-R Model where t is the polarization tilt angle relative to horizontal. Fig. 1 shows the schematic representation of earth –space Step 6. Determine the horizontal path adjustment factor, r0.01path link and the details of the parameters used in the model. for 0.01% of the time usingBased on the geographical conditions and measured rainfall r0 .0 1  1using the disdrometer, the rain attenuation can be calculated LG  R (9) 1  0 .7 8 0 .3 8  1  e  2 L   G using ITU-R P. 618 - 9 model in the following f© 2012 ACEEE 7DOI: 01.IJCOM.3.2. 4
  3. 3. ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012where f is the frequency in GHz. TABLE II.VARIATION OF RAINFALL RATE AND ATTENUATION WITH RESPECT TO %Step 7. Calculate the adjusted rainy path length, L R (Km), TIME EXCEEDED % Time Rainfall Rate Attenuationthrough rain using exceeded (mm/hr) (dB) L r (10) L R  G 0 .0 1 fo r    co s  0.001% 115.89 25.28 ( hR  hS ) (11) 0.01% 62.83 12.47 LS  for  where sin  0.1% 17.32 2.03 1  hR  hS    tan   (12) 1% 1.96 0.11  LG r0.01 Step 8. Obtain the vertical reduction factor v0.01 , 5% 0 0for 0.01% of the time by using integration time. The obtained rainfall rate with different % 1 (13) v 0.01  time exceedence of average year will be compared and studied  LR  R  1 sin   31(1  e   /1   )  0.45  with practical rainfall rates measured with disdrometer   f2   arrangement as a next step in the research work.where   36   , for   36  (14)   0, for   36  (15)Step 9. Determine the effective path length through rain, L E(Km), given by LE  LR v0.01 (16)Step 10. Calculate the predicted attenuation exceeded for0.01% of an average year by using A0.01   R LE dB (17)Step 11. The estimated attenuation to be exceeded for theother percentages of an average year, in the range 0.001% to10% may then be estimated using A0.01 as p   0.65 5  0 .03 ln ( p )  0.04 5 ln ( A0.01 )   sin  (1  p )  A p  A0.01 ( ) 0.01 (18)where p is the percentage probability of interest and  isgiven by Figure. 2.Variations of rainfall rate (mm/hr) with respect for p  1%,   0 (19) to % time exceeded if   36  (20) for p  1%,   0 The attenuation of the signal is obtained at 11 GHz frequency, using ITU-R P. 838 - 1 Recommendation for different rainfall    0.005(   36) for  25 and   36  (21) rates. It is evident from Fig. 3 that the attenuation increases    0.005(   36)  1.8  4.25 sin  , (22) with rainfall rate. The theoretical results will be used to study for   25  and   36  and compare the amount of attenuation introduced practically in the extended future research work. III. RESULTS AND DISCUSSION The theoretical values for rain attenuation are calculatedfor different rainfall rates using ITU-R model at KL University.The DTH receiver installed in the site operates in Ku bandwhose elevation angle is 64.50 . The rainfall rates are calculatedbased on the geographical latitude and longitude, and will beused to measure attenuation at different frequencies [15].Table II gives the variation of rainfall rate and attenuationwith respect to % time exceeded of an average year at 11 GHz. The rainfall rate is calculated using the ITU-R P. 837 - 5Recommendation and the variation of the rainfall rate(mm/hr) is as shown in Fig. 2, for different exceedencepercentages. At 11 GHz operating frequency, it can beobserved that the maximum rainfall rate is 115.89 mm/hr at0.001% time of an average year. The rainfall rate is 62.83 mm/ Figure. 3. Variation of attenuation with respect to rainfall ratehr exceeded for 0.01% of an average year, with 1-min The attenuation is calculated for frequencies from 1 GHz to© 2012 ACEEE 8DOI: 01.IJCOM.3.2. 4
  4. 4. ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012 15 GHz with a rainfall rate 0.01  62.83 mm/hr using ITU- R rain attenuation is the predominant. In this paper, ITU-R modelR model. With an increase in frequency, there is a significant is used to predict the rainfall rate and attenuation due to rain,increase in the attenuation as shown in Fig. 4. The attenuation at KL University, Guntur. The attenuation is calculated, foris 0.00814 dB at 1 GHz frequency and 21.39 dB at 15 GHz. different rainfall rates and exceedence percentages of an average year. The preliminary results indicate that the attenuation increases with frequency and rainfall rate. These predicted values can be compared with the measured experimental data after installation of the setup in the location. ACKNOWLEDGMENTS The authors wish to thank Dr. K. Sarat Kumar, Associate Dean, Sponsored Research and Dr. D. Venkata Ratnam, KL University for their valuable suggestions. This work was supported in part by a grant from Department of Science and Technology, New Delhi, India. REFERENCES [1] Pratt, T., C. W. Bostian, and J. E. Alnutt, “Satellite Figure.4. Rain Attenuation Variation with Frequency at Rainfall Communication”, John Wiley and Sons, 2003,536 pp. Rate R0.01  62.83 mm/hr [2] Cost Action 255 Final Report, “Radiowave Propagation The rain attenuation is calculated for 0.001% to 5% Modelling for SatCom Services at Ku-Band and Above”, ESAexceedence percentages of an average year as shown in Publications Division, Noordwijk, The Netherlands, 2002.Fig. 5. The attenuation is 25.28 dB with 0.001% and 0 dB [3] K. P. Liolis, A. D. Panagopoulos, and S. Scalise, “On thewith 5% exceeded time of an average year. The rainfall rate combination of tropospheric and local environment(mm/hr) for the location is obtained from India Meteorological propagation effects for mobile satellite systems above 10Department and studied for five consecutive years from GHz”, IEEE Trans. Veh. Technol., vol. 59, no. 3, pp. 1109–2007 – 2011. The statistical analysis is done by calculating 1120, Mar. 2010. [4] Timothy, K. I.; Ong, J. T. &Choo, E. B. L. (2002), “Raindropcumulative distribution function for every month using Size Distribution Using Method of Moments for TerrestrialMATLAB and it has been observed that the rainfall rate is and Satellite Communication Applications in Singapore”, IEEEmaximum and for more duration during July and Augustas Transactions on Antennas and Propagation, Vol. 15, No. 10,shown in Fig. 6. and hence the rain attenuation will be October 2002, 1420- 1424, ISSN: 0018-926X.predominant during the above period. [5] Maitra A., “Rain Attenuation Modeling From Measurements of Rain Drop Size Distribution in The Indian Region”, IEEE Antennas and Wireless Propagation Letters. Vol. 3, P. 180– 181, 2004. [6] John S. Seybold, “Introduction to RF Propagation”, John Wiley & Sons, 2005. [7] Athanasios D. Panagopoulos, Pantelis - Daniel M. Arapoglou, and Panayotis G. Cottis, “Satellite Communications at Ku, Ka, and V Bands: Propagation Impairments and Mitigation Techniques”, IEEE Communications surveys, Volume 6, No.3, 2004. [8] Ojo, J. S., M. O. Ajewole, and S. K. Sarkar, “Rain rate and rain attenuation prediction for Satellite Communication in Ku and Ka bands over Nigeria”, Progress in Electromagnetics Research B, Vol. 5, 207-223, 2008. [9] R. K. Crane, “Prediction of attenuation by rain”, IEEE Trans. Commun., vol. 28, pp. 1717–1733, Sept. 1980. Figure. 5. Variation of Rain Attenuation with Respect to % Time [10] R. K. Crane and H. C. Shieh, “ A two-component rain model Exceeded for the prediction of site diversity improvement performance”, Radio Sci., vol. 24, no. 6, pp. 641–655, 1989. IV. CONCLUSIONS [11] A. Dissanayake, J. Allnutt, and F. Haidara, “A Prediction Due to the spectral congestion of frequency bands Model that Combines Rain Attenuation and other Propagation Impairments along Earth-Satellite Paths,” IEEE Trans.allotted and requirement of higher bandwidths, the importance Antennas Propag., vol. 45, no. 10, 1997, pp. 1546–58of higher frequency bands like Ku band ( 12/14 GHz) and Ka [12] Moupfouma F., Martin L. “Modelling of the rainfall rate cu-band ( 20/30 GHz) is becoming more predominant nowadays mulative distribution for the design of satellite and terrestrialfor satellite communication services. At these frequencies, communication systems”, International J. of Satellite Comm.,various impairments will cause the signal to fade, among which© 2012 ACEEE 9DOI: 01.IJCOM.3.2.4
  5. 5. ACEEE Int. J. on Communications, Vol. 03, No. 02, Nov 2012 1995. Vol. 13. P. 105–115. K.Padma Raju received B.Tech from[13] Dong You Choi, Jae Young Pyun, Sun Kuh Noh, and Sang Nagarjuna University, M. Tech from NIT Woong Lee, “Comparison of Measured Rain Attenuation in Warangal, Ph. D from Andhra the 12.25 GHz Band with Predictions by the ITU-R Model”, UniversityIndia and Post-Doctoral Fellow- International Journal of Antennas and Propagation, Hindawi ship at Hoseo University, South Korea. He Publishers, 2012.[14] International Telecommunication Union, “Characteristics of has worked as Digital Signal Processing precipitation for propagation modeling”, Recommendation Software Engineer in Signion Systems Pvt. ITU- R, P.837-5, Geneva 2007. Ltd., Hyderabad, India, before joining Jawaharlal Nehru[15] ITU-R P.618-9, “Propagation data and prediction methods Technological University Kakinada, India.He has 17 years of required for the design of earth-space telecommunication teaching experience and is Professor of Electronics systems”, International Telecommunication Union, Geneva, andCommunication Engineering, Jawaharlal Nehru Techno- Switzerland, 2007. logical University Kakinada, India. Presently he is working[16] “Rain height model for prediction methods”, Recommendation as Principal, University College of Engineering, Jawaharlal ITU-R P.839-3, ITU-R P Sers., Int. Telecomm. Union, Geneva, Nehru Technological University Kakinada, India.He worked 2001. as Research Professor at Hoseo University, South Korea[17] “ Specific attenuation model for rain for use in predictionmethods”, Recommendation ITU-R P.838-3, ITU- during 2006-2007. He has published 30 technical papers in R P Sers., March 2005. National/International Journals/Conference proceedings and guiding 06 research students in the area of Antennas, EMI/ BIOGRAPHIES EMC and Signal Processing His fields of interest are Signal M. Sridhar received B. Tech degree from Processing Miicrowave and Radar Communications and EMI/ Acharya Nagarjuna University, Guntur, In- EMC. dia in 2001 and M.Tech degree from Ch. Srinivasa Rao is currently working as Jawaharlal Nehru Technological University, Professor   of  Electronics & Communica- Anantapur, India in 2009. He is a Member tion Engineering, Sri SaiAditya Institute of of The Instituition of Electronics and Tele- Science & Technology, Surampalem, Andhra communications Engineers (IETE) and Pradesh, India. He obtained Ph. D frompresently working as an Associate Professor in KL University College of Engineering,University, Guntur, India. He is pursuing Ph.D in Jawaharlal Nehru Technological UniversityJawaharlal Nehru Technological University Kakinada, Kakinada, Kakinada, Andhra Pradesh, India in 2009. HeKakinada, India and his research area of interest is Satellite received M. Tech. degree from JNTU, Hyderabad and B. TechCommunications. He is having 11 years of teaching from Nagarjuna University. He has 12 International Journal,experience. Conference Publications and one Monograph to his credit. He is guiding 06 research students in Digital Image/Signal Processing and Communications Engineering. Dr. Rao is a Fellow of IETE and member of IEEE & CSI. Figure. 6. Cumulative Distribution Functions of Rainfall rate during 2007 – 2011 in Guntur© 2012 ACEEE 10DOI: 01.IJCOM.3.2. 4