Evaluating Time Diversity Performance on an OnBoard Processing Satellite in Earth Station Downlink.

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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 (kmudofia_at_glam.ac.uk) .
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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

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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

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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

• Sparsholt is about 7.8Km from Chilbolton

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Analysis of Time Series of Sites
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?.
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Cumulative distributions of measured rain
attenuation for Sparsholt compared with the ITU-R
618v9 (predicted) model at 20.7 GHz with an
elevation angle of 30?.
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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?.
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Cumulative distributions for three sites measured
at 20.7 GHz and the scaled distribution at 30 GHz
at 30? elevation angle.
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Evaluation, Results and Analyses

• Time diversity gain, time percentage, time delay
• Cumulative distributions of rain attenuation at
  time, t and (tdelay) 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

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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

• From a model for TD by Ismail Watson developed
  for equatorial climate, a joint distribution is
  deduced to

• This is the percentage time exceeded for an
  effective or minimal attenuation, and is
  described by the function

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Evaluation and Analyses (contd.)

• Effective attenuation, is the minimum of the two
  instantaneous attenuation values with time delay

• 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
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Time diversity statistics at Sparsholt. This
denotes gains achieved with outage probabilities
at varying time delays
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Time diversity statistics at Dundee. This denotes
gains achieved with outage probabilities at
varying time delays
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Discussions and Conclusions

• 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

• 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, URSI-F
  Symposium Colloque, pp.6.5.1-6.5.4, Ravenscar,
  UK.
• 3. Ventouras, S., Wrench C. L. Callaghan, S.
  A., (2000), Earth-Space 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.369-373
• 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