1. Rain Attenuation in Satellite Communications
Associate Professor Dr.Yagasena Appannah
FACULTY OF INTEGRATIVE SCIENCES AND TECHNOLOGY
School of Engineering and Computer Technology
QUEST INTERNATIONAL UNIVERSITY PERAK
22nd August 2013

2. What is Rain Attenuation ?
The attenuation of a signal due to rain is the extent to which the strength of a signal is reduced when passing through rain from a transmitter to a receiver, Also called rain fade.

4. Climatic Factors Affecting Satellite-Earth Link
Cloud attenuation
Gaseous attenuation
Water vapor attenuation
Oxygen attenuation
Rain attenuation

5. Factors Affecting Satellite-Earth Link in Rain
Frequency of operation
Elevation angle of satellite
Slant-path length
Rain rate
Rain height

6. How does it affect you ?
All forms of wireless terrestrial and extra-terrestrial mode of communication will be disrupted.
Example:
Satellite TV
Satellite data transmission
Mobile communication

7. Why Study Rain Attenuation ?
Rain attenuation is a major constraint in satellite link design above 10 GHz.
The International Telecommunication Union (ITU) model is based on data collected predominantly from temperate regions. Hence not accurate for use in tropical & equatorial regions

8. Rainfall Classification
Stratiform Rain – medium & low intensity, wide area, long duration.
Convective Rain – high intensity, small area, short duration.

9. ITU Rain Region (0.01%)

10. Uplink / Downlink

11. Frequency Allocations

12. Types of Satellites

13. Data Collection Set Up

14. Beacon Signal Receiver

15. Types of Rain Gauges
Tipping Bucket
Optical

16. Satellite/Receiving Antenna Specifications
Parameters
Specifications
Satellite Position
144oE (Superbird-C)
Beacon Frequency
GHz
Receiving antenna elevation
40.1o
Receiving antenna height
100 m above sea level
Receiving antenna diameter
2.4 m
Earth station location
4.367oN, 101oE

17. Clear Sky Signal

18. Cloud Attenuation

19. Rain rate & Beacon level (1)

20. Rain rate & Beacon level (2)

21. Rain rate & Beacon level (3)

22. Rain rate & Beacon level (4)

23. Rainfall Distribution (1)

24. Rainfall Distribution (2)

25. Diurnal Variation of Rain rate

26. Attenuation vs Instantaneous Rain Rate

27. Attenuation vs Rain Rate

28. ITU Availability Criteria
Data Transmission – 99.99% (0.01% unavailability ~ 53 min/year)
Broadcast – 99.9% (0.1% unavailability ~ 9 hr/year))

29. Measured vs ITU % Attenuation (dB) Rain rate (mm/h) Measured ITU 0.3
7.34
4.50
28.6
16.5
0.1
15.94
8.07
60.3
41.6
0.03
27.32
13.05
95.6
73.8
0.01
34.10
18.34
124.7
145.0

30. Comparison of Rain Rate Models

31. Comparison of Attenuation Models

32. Comparison With Other Tropical Countries
Location
Frequency
(GHz)
Elevation (deg)
Attenuation (dB)
Rain rate (mm/hr)
Malaysia
12.255
40.1
34.10
124.7
Singapore
11.198
42.9
32.00
125.5
Thailand
12.748
45.0
25.00
100.0
Indonesia
12.247
64.7
17.00
120.0

33. Proposed Two-Part Attenuation Model (2000)

34. Proposed Two-Part Attenuation Model (2000)

35. Rain Mitigation Techniques
Site Diversity
Power Control
Frequency Diversity
Data Rate Reduction

36. Conclusion
ITU satellite-earth propagation model underestimates the rain attenuation in tropical and equatorial regions.
Two-Part model must be incorporated into ITU prediction model to accommodate different rainfall characteristics for more accurate prediction.

37. Firm sues MEASAT over dishes
Wednesday September 29, 2010
By NURBAITI HAMDAN and ONG HAN SEAN
KUALA LUMPUR: A TV support equipment supplier is suing Astro’s subsidiary Measat Broadcast Network Systems Sdn Bhd and another company for more than RM1.3bil over an alleged breach of a “non-disclosure agreement”.
AV Asia Sdn Bhd claimed that its confidential information was used by Measat to reduce the problem of rain fade – a situation where the satellite transmission would be interrupted during rain.
According to the statement of claim, the Malaysian Commu­nications and Multimedia Com­mission made recommendations for Measat to conduct studies on the use of different satellite dishes to reduce rain fade in May 2008.

38. Astro satellite issue: Trouble beyond rain
KUALA LUMPUR: Astro customers have been left confused over unsettling revelations in a RM1.3 billion suit involving “leaked” confidential data for a new satellite dish that reduces signal loss during rainstorms
On rain fade, AV Asia’s chief executive officer Mr.XXX claimed Astro, while using the new dish, was not installing it correctly. “If installed using a digital level meter, it would definitely reduce rain fade. Right now, they're installing it manually,” he said.
Posted by Global News-n-Views at Saturday, October 02, 2010