Propagation Research An Internal Perspective
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Transcript of Propagation Research An Internal Perspective
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Propagation Research
An Internal Perspective
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THE VIEWPOINT
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The licensing process
Application R U L E S Issue
Technical assignment tools
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Technical software
The technical computing and propagation modelling unit
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T C P MSG 3 Research
MeasurementsTestingModels
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THE TASK
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Technical assignment of fixed services
High technical work-load as result of:-
• Each terminal fully engineered;
• Intensive intra- and inter-service frequency sharing;
• Propagation outages down to 0.001% annual;
• International coordination distances.
About 98% of TCPM’s software work relates to fixed services
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Bands allocated to fixed services
Up to 40 GHz, the current licensed bands, nearly 9 GHz is allocated to terrestrial and satellite fixed services, including FWA/BFWA.
A further 3.8 GHz above 40 GHz soon.
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Wanted and unwanted signals
(8 combinations for two point-to-point links)
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COST 210
The models used for annual outage down to 0.001% annual are largely based on a major measurement
programme conducted under COST 210.They are embodied in
ITU-R Recommendations P.452 and P.620 and the newly-revised
Appendix S.7 of the Radio Regulations.
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LIMITATIONS
OF
PRESENT METHODS
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No correlation model for signal variations
What is thecorrelation between
signal variationson paths d1 and d2
?
How does it vary with angle ‘A’, frequency, topography, climate,
and % time ?
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No correlation model for signal variations
At present there is insufficient information for a practical
assignment model.
Conservativeassumptions must be made
What is thecorrelation between
signal variationson paths d1 and d2
?
How does it vary with angle ‘A’, frequency, topography, climate,
and % time ?
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Rain modelling for different climates
The ‘CCIR’ rain zones show wide variations of rain climate.
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Rain modelling for different climates
The ‘CCIR’ rain zones show wide variations of rain climate.
P.530 uses a single
time-variability distribution
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Rain modelling for different paths
No models take account of
the spatial structure of
rain in relation to path length
and orientation
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The effect of rain structure
Links differing only in orientation to a rain system will experience different intensity and duration of the rain attenuation event.
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NEW
REQUIREMENTS
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Recommendations G.82X
Link performance is now defined by Recommendations such as G.826, G.828, based on the distribution of errored and severely-errored seconds.
Annual statistics are thus not enough.
The spatial and temporal structures of the relevant phenomena are required to a resolution of 1 second.
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Temporal structure of signal variations
At present only the aggregate of events in an annual year or worst month are considered.
To meet current design standards, the probabilities P(t) are needed for event durations and spacings
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CONCERNS
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CONCERN 1
BUDGETSA change in emphasis towards short
and medium term objectives will make it difficult to budget for long-term
measurement programmes.
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CONCERN 2
EXPERTISEA work environment based around competitive tendering may mitigate
against the retention of scientific expertise.
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CONCERN 3
INTERNATIONALLack of participation by appropriate
experts damages the process of internationally standardising
propagation models.
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CONCERN 4
THE BLUE SKYIn radiowave propagation,
the curiosity-driven researcher will become an endangered species.
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IT IS HOPED THAT THIS IS NOT
THE END
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IT ISN’T
TECHNICALAPPENDIX
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Wantedand
unwantedsignals
The above diagram lumps the annual fade and enhancement times into single events
and assumes that they are uncorrelated.
Current models can do this down to 0.001%.