Propagation Research

An Internal Perspective

THE VIEWPOINT

The licensing process

Application R U L E S Issue

Technical assignment tools

Technical software

The technical computing and propagation modelling unit

T C P MSG 3 Research

MeasurementsTestingModels

THE TASK

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

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.

Wanted and unwanted signals

(8 combinations for two point-to-point links)

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.

LIMITATIONS

OF

PRESENT METHODS

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 ?

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 ?

Rain modelling for different climates

The ‘CCIR’ rain zones show wide variations of rain climate.

Rain modelling for different climates

The ‘CCIR’ rain zones show wide variations of rain climate.

P.530 uses a single

time-variability distribution

Rain modelling for different paths

No models take account of

the spatial structure of

rain in relation to path length

and orientation

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.

NEW

REQUIREMENTS

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.

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

CONCERNS

CONCERN 1

BUDGETSA change in emphasis towards short

and medium term objectives will make it difficult to budget for long-term

measurement programmes.

CONCERN 2

EXPERTISEA work environment based around competitive tendering may mitigate

against the retention of scientific expertise.

CONCERN 3

INTERNATIONALLack of participation by appropriate

experts damages the process of internationally standardising

propagation models.

CONCERN 4

THE BLUE SKYIn radiowave propagation,

the curiosity-driven researcher will become an endangered species.

IT IS HOPED THAT THIS IS NOT

THE END

IT ISN’T

TECHNICALAPPENDIX

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%.