Transcript Fade Mitigation Process for Broadcast Satellite Systems

Evaluating Time Diversity Performance on
an On-Board Processing Satellite in Earth
Station Downlink.
Kufre Udofia & Ifiok Otung,
ICRC, Faculty of Advanced Technology
University of Glamorgan,
Pontypridd CF37 1DL, Wales. United Kingdom
([email protected])
.
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Content Outline
Introduction
 FMT
 TD
 Evaluation, Results and Analyses
 Discussions and Conclusions
 References
 Questions

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Introduction






Fade Mitigation Technique
FMT is a reliable and robust way of
overcoming fading in real-time
Increase development for high data rate
multimedia services
Congestion of conventional bands X, C and Ku
Improve link performance
Implementation necessary at Ka and V –bands
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Types of FMT








Power Control
Frequency Diversity
Spatial/Site Diversity
Time Diversity
Satellite Diversity
Antenna Diversity
Signal Processing
Adaptive Coding
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Time Diversity (TD)

Re-sending of signal until channel status
allows it to pass through
1 to 86400 samples
represents seconds
Sampled
Time Series
1 2 34 5 6
86400
 t  1 min
1
86400
t  5mins
1
86400
Delayed
Time Series
 t  10 min s
 t  n min s
delay
1
86400
1
86400
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Time Diversity (TD)






Based on the idea that events are short-lived
Dependent on the re-transmission delay
More affordable when compared to site
diversity and uses a single link unlike others
Provides high quality data rate multimedia
services
Provides high quality of service (QoS) and an
increase availability.
Able to combat large fading
Problem Definition

Evaluating time diversity performance on an
on-board processing satellite in earth station
downlink. A fade mitigation process to combat
effects of atmosphere on satellite-earth links at
Ka and V bands, a case study is the UK.
Properties of Ka Bands
Larger bandwidths and cost efficiency
 Reduced co-ordination problems due to
decreased wavelength
 Propagation impairments are very prominent

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Propagation Impairments Factors

Rain attenuation, melting layer, cloud,
attenuation, tropospheric scintillation,
depolarisation due to rain and ice
Effects of Propagation Impairments

Fading, signal attenuation, increase in the sky
noise temperature and intersystem interference
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Block View of the Link
UFO-9
20.7 GHz
Beacon
Payload
Signal
Directions
Adown From
Link
Cloud
Adown
BEACON
RAIN
Aup From
Scaled
Frequency
Earth-stations
with Beacon
Receivers
Dundee
600.2Km
Chilbolton
Sparsholt is about 7.8Km from Chilbolton
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Analysis of Time Series of Sites
Chilbolton
5
0
-5
0
1
2
3
4
5
6
7
8
9
4
Attenuation (dB)
x 10
Dundee
1
0
-1
0
1
2
3
4
5
6
7
8
9
4
x 10
Sparsholt
5
0
-5
0
1
2
3
4
5
Time (seconds)
6
7
8
9
4
x 10
Rain attenuation time series for three UK sites measured
at 20.7GHz on November 11, 2005.

Earth location, separation distances, frequency
and satellite earth link
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Cumulative distributions of measured rain
attenuation for Chilbolton compared with the
ITU-R 618v9 (predicted) model at 20.7 GHz with
an elevation angle of 30.
2
10
Measured
ITU
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
5
10
15
Attenuation (dB)
20
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30
11
Cumulative distributions of measured rain
attenuation for Sparsholt compared with the ITUR 618v9 (predicted) model at 20.7 GHz with an
elevation angle of 30.
2
10
Measured
ITU
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
5
10
15
Attenuation (dB)
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20
25
12
Cumulative distributions of measured rain
attenuation for Dundee compared with the ITU-R
618v9 (predicted) model at 20.7 GHz with an
elevation angle of 30.
2
10
Measured
ITU
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
5
10
15
Attenuation (dB)
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20
25
13
Cumulative distributions for three sites measured
at 20.7 GHz and the scaled distribution at 30 GHz
at 30 elevation angle.
2
10
20.7 GHz Chilbolton
20.7 GHz Sparsholt
20.7 GHz Dundee
30 GHz Chilbolton
30 GHz Sparsholt
30 GHz Dundee
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
2
4
6
8
10
12
Attenuation (dB)
14
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18
20
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Evaluation, Results and Analyses





Time diversity gain, time percentage, time
delay
Cumulative distributions of rain attenuation at
time, t and (t+delay) are considered, based on a
simple TD principle – retransmitted signals
Gain increases with increase in the delay and
decreases with increase in the time percentage
Improves the fade margin per increased delay
For retransmission, the time shift per sample
Tshift  t  t
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Evaluation and Analyses (contd.)

The pdf of the observed rain attenuation series
for a satellite to earth link is given by
p{A(t )  a}  1  p{A(t )}

From a model for TD by Ismail & Watson
developed for equatorial climate, a joint
distribution is deduced to
p[ AT  A(t )]  1  p[min{A(t ), A(t  t )}]

This is the percentage time exceeded for an
effective or minimal attenuation, and is
described by the function
AT  Aeff  min{A(t ), A(t  t )}
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Evaluation and Analyses (contd.)

Effective attenuation, is the minimum of the
two instantaneous attenuation values with time
delay
GTD  A(t  1s)  [min{A(t  1s), A(t  t  1s)}]
GTD  A(t  1s)  AT (t  t  t )
GTD  A(t )  AT

The gain is a function of delays and time
percentages
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Time diversity statistics at Chilbolton. This
denotes gains achieved with outage probabilities
at varying time delays
2
10
1 mins
5 mins
10 mins
15 mins
30 mins
45 mins
60 mins
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
2
4
6
8
10
Gain (dB)
12
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16
18
18
Time diversity statistics at Sparsholt. This
denotes gains achieved with outage probabilities
at varying time delays
2
10
1 mins
5 mins
10 mins
15 mins
30 mins
45 mins
60 mins
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
2
4
6
8
Gain (dB)
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10
12
14
19
Time diversity statistics at Dundee. This denotes
gains achieved with outage probabilities at
varying time delays
2
10
1 mins
5 mins
10 mins
15 mins
30 mins
45 mins
60 mins
1
Time Abscissa is Exceeded (%)
10
0
10
-1
10
-2
10
-3
10
0
2
4
6
8
Gain (dB)
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12
14
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Discussions and Conclusions

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Relevant to communications network operators
and system designers in the UK wishing to
offer improved broadband
Relevant to the UK propagation research
programme
Improvement of performance for wireless
communication systems involving BSS
Video-on-demand services
Electronic data broadcasting and file transfers
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Discussions and Conclusions

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Access to the internet and data base
E-commerce and re-mote teaching access such
as the Open University
TD as a fade mitigation scheme for broadcast
satellite systems
TD gain is a function of time delay and the
time percentages
The study of TD gain on a single downlink
(OB Satellite to ES) and a subsequent study of
a complete link, ES to Satellite to ES will lead
to a complete evaluation of TD performance.
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References
1. Watson, P.A., Ismail, A.F., Seng, P. A., Ja, Y. Y., Kamaruddin, H. S.,
Eastment, J. D. & Thurai, M., (1998), ”Investigation of Rain
Fading and Possible Countermeasures on Satellite-Earth Links in
Tropical climates”, URSI-F Open Symposium, Aviero, Portugal,
pp.3-7.
2. Fukuchi, H, (1992), “Slant Path Attenuation Analysis at 20 GHz for
Time Diversity Reception of future Satellite Broadcasting”, URSIF Symposium Colloque, pp.6.5.1-6.5.4, Ravenscar, UK.
3. Ventouras, S., Wrench C. L. & Callaghan, S. A., (2000), “EarthSpace Propagation, Measurement and Analysis of Satellite Beacon
Transmissions at Frequencies up to 50GHz, Part 2: Attenuation
Statistics and Frequency Scaling of Attenuation Values”, RCRU,
CLRC Chilton, UK
4. Emilio Matricciani, (2006), “Time Diversity as a Rain Attenuation
Countermeasure in Satellite Links in the 10-100 GHz Frequency
Bands,” Department of Electronic and Information, Milan
Polytechnic, Milan.
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References
5. Ismail, A. F. & Watson, P. A., (2000), “Characteristics of Fading
and Fade Countermeasures on a Satellite-Earth Link Operating in
an Equatorial Climate, with Reference to Broadcast Applications”,
IEE Proc. Microwave, Antenna Propagation, vol.147, No.5, pp.369373
6. Fabbro, V. and Castanet, L. (2006), “Characterisation and Modeling
of Time Diversity in 20-50GHz Band,” Department of
Electromagnetism and Radar, Unite of Research APR: Antenna
and Radioelectric Propagations, Toulouse, France.
7. Fukuchi, H & Nakayama, T. (2004), “Quantitative Evaluation of
Time Diversity as a Novel Attenuation Mitigation Technology for
Future High Speed Satellite Communication”, IEICE Trans.,
vol.E87-B, pp.2119-2123.
8. “Propagation data and prediction methods required for the design
of Earth-space telecommunication systems”, Recommendations
ITU-R P.618-9, 2007, Geneva, Switzerland.
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Thank you
Questions Please