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

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.

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

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

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

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

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

ITU Rain Region (0.01%)

Uplink / Downlink

Frequency Allocations

Types of Satellites

Data Collection Set Up

Beacon Signal Receiver

Types of Rain Gauges Tipping Bucket Optical

Satellite/Receiving Antenna Specifications Parameters Specifications Satellite Position 144oE (Superbird-C) Beacon Frequency 12.255 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

Clear Sky Signal

Cloud Attenuation

Rain rate & Beacon level (1)

Rain rate & Beacon level (2)

Rain rate & Beacon level (3)

Rain rate & Beacon level (4)

Rainfall Distribution (1)

Rainfall Distribution (2)

Diurnal Variation of Rain rate

Attenuation vs Instantaneous Rain Rate

Attenuation vs Rain Rate

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

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

Comparison of Rain Rate Models

Comparison of Attenuation Models

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

Proposed Two-Part Attenuation Model (2000)

Proposed Two-Part Attenuation Model (2000)

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

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.

Firm sues MEASAT over dishes Wednesday September 29, 2010 By NURBAITI HAMDAN and ONG HAN SEAN newsdesk@thestar.com.my 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.

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