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

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					                                                                              ACEEE Int. J. on Communications, Vol. 03, No. 03, Nov 2012



Estimation 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: sridhar.m@kluniversity.in
                                     2
                                       Department of ECE, JNTU Kakinada, Kakinada, India
                                                Email: padmaraju_k@yahoo.com
                    3
                      Department of ECE, Sri SaiAditya Institute of Science & Technology, Surampalem, India
                                                 Email: ch_rao@rediffmail.com

Abstract — 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 at
frequencies, the signal will be affected by various propagation               these frequency ranges and some of the energy gets scattered
impairments such as rain attenuation, cloud attenuation,                      by Rayleigh and Mie scattering mechanisms [4]. The rain
tropospheric scintillation, ionospheric scintillation, water
                                                                              drop size distribution is exponential when expressed
vapour attenuation, and rain and ice depolarization. Among
all 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 the
ITU-R rain attenuation model. The preliminary results of the                  number of drops per cubic meter with diameters between D
work will be used to calculate the attenuation experimentally                 and D + dD mm [5]. The rainfall rate R is related to N (D) and
and comparison can be made, which helps to develop a new                      also to the terminal velocity of V (D) the falling drops in
rain attenuation model at Ku and Ka bands.                                    meters per second with diameter D by
Index 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 determine
of a link budget between the transmitter and the receiver that                the probability that a given fade depth will be exceeded. The
provides an adequate signal level at the receiver ’s                          rain availabilityof a communication link is the complement of
demodulator 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, signal
link can be specified or measured using Bit Error Rate (BER)                  processing and site diversity methods are used to improve
and Carrier-to-Noise ratio (C/N). It is the link designer’s task              the performance of link design and this requires proper
to ensure that loss of signal occurs for no longer than the                   prediction of attenuation due to rain [7]. There are two
time permitted for that service. The development of an                        approaches to predict the rain attenuation namely, a physical
accurate 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 length
There are many phenomena that lead to signal loss on                          and rainfall rate using the information from various data bases
transmission through the earth’s atmosphere. These include:                   [8]. Various rain attenuation prediction models are available
cloud attenuation, tropospheric scintillation, ionospheric                    based on the geographical and climatic conditions. The
Scintillation, Water vapour attenuation, rain and ice                         important models are Crane global model [9], Two-component
depolarization, 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], International
important 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: sridhar.m@kluniversity.in).                                           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 most
College of Engineering, JNTU Kakinada, Kakinada, Andhra Pradesh,              accurate statistical estimate of attenuation on slant paths [2].
India (email: padmaraju_k@yahoo.com).
   Dr. Ch. Srinivasa Rao is working as Principal, Sri Sai Aditya Insti-       B. ITU-R P. 618 - 9 Rain Attenuation Model
tute of Science & Techology, Surampalem, Andhra Pradesh, India                   The ITU  Radio  communication  Sector (ITU-R)  is  one
(email:ch_rao@rediffmail.com).
© 2012 ACEEE                                                              6
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                                                                        ACEEE Int. J. on Communications, Vol. 03, No. 03, Nov 2012


among the three divisions of the International                          manner [15]:
Telecommunication Union (ITU) which is responsible                      Step 1. Calculate the rain height h R(Km)from the
for radio communication. It manages the international radio-            recommendation ITU-R P.839 as
frequency spectrum and satellite orbit resources and also
enhances 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 region
along with the probability of that rain rate being exceeded
[6]. This model uses the rain rate at 0.01% probability level
for the estimation of attenuation and then applies an
adjustment factor to the predicted rain fade depth for other
probabilities. It can be used for the frequencies from
4 - 55 GHz and 0.001 - 5% percentage probability range. It is
based on log-normal distribution and both rain intensity and
path attenuation distribution conform to the same log-normal
distribution. Inhomogeneity in rain in both horizontal and
vertical 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 Height
Guntur which is located 29.08 m above sea level. The latitude                                C:   Liquid precipitation
                                                                                             D:   Earth-Space path
and longitude of the location are 16.46' N and 80.54' E
respectively. Two DTH receivers operating in Ku band is                 Step 2. Determine the slant-path length L s , below the rain
installed in the location which receives the signal from NSS6           height from
satellite ( 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 the
time 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 path
information can be recorded with a data logger. The rainfall            length from
rate exceeding 0.01% of an average year in mm/hr for the
location 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 be
0.01% of an average year (mm/hr) with 1-min integration time,           calculated with the help of statistical data available in various
height of the location above mean sea level (Km), elevation             meteorological databases or from the maps provided by
angle 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 the
effective radius of the Earth (Km) [14]. Table I gives the              frequency dependent regression coefficients provided in
geographical 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                                                 2k

A. 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, r0.01
path link and the details of the parameters used in the model.   for 0.01% of the time using
Based on the geographical conditions and measured rainfall                 r0 .0 1 
                                                                                                       1
using 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                                                   7
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                                                                                                    ACEEE Int. J. on Communications, Vol. 03, No. 03, Nov 2012


where 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          Attenuation
through 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                      0
for    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 for
0.01% of an average year by using
                          A0.01   R LE dB                                             (17)
Step 11. The estimated attenuation to be exceeded for the
other percentages of an average year, in the range 0.001% to
10% 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  is
given 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 calculated
for different rainfall rates using ITU-R model at KL University.
The DTH receiver installed in the site operates in Ku band
whose elevation angle is 64.50 . The rainfall rates are calculated
based on the geographical latitude and longitude, and will be
used to measure attenuation at different frequencies [15].
Table II gives the variation of rainfall rate and attenuation
with respect to % time exceeded of an average year at 11 GHz.
    The rainfall rate is calculated using the ITU-R P. 837 - 5
Recommendation and the variation of the rainfall rate
(mm/hr) is as shown in Fig. 2, for different exceedence
percentages. At 11 GHz operating frequency, it can be
observed that the maximum rainfall rate is 115.89 mm/hr at
0.001% time of an average year. The rainfall rate is 62.83 mm/                                         Figure. 3. Variation of attenuation with respect to rainfall rate
hr exceeded for 0.01% of an average year, with 1-min                                                The attenuation is calculated for frequencies from 1 GHz to
© 2012 ACEEE                                                                                    8
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                                                                        ACEEE Int. J. on Communications, Vol. 03, No. 03, 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 model
R 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, for
is 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”, ESA
exceedence 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 the
with 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 10
Department 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), “Raindrop
cumulative distribution function for every month using
                                                                             Size Distribution Using Method of Moments for Terrestrial
MATLAB and it has been observed that the rainfall rate is                    and Satellite Communication Applications in Singapore”, IEEE
maximum 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. 1546–58
of 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 terrestrial
for 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                                                        9
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                                                                        ACEEE Int. J. on Communications, Vol. 03, No. 03, 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 from
presently working as an Associate Professor in KL
                                                                                        University College of Engineering,
University, Guntur, India. He is pursuing Ph.D in
                                                                                        Jawaharlal Nehru Technological University
Jawaharlal Nehru Technological University Kakinada,
                                                                        Kakinada, Kakinada, Andhra Pradesh, India in 2009. He
Kakinada, India and his research area of interest is Satellite
                                                                        received M. Tech. degree from JNTU, Hyderabad and B. Tech
Communications. 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                                                       10
DOI: 01.IJCOM.3.3. 4

				
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Description: 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.