Propagation Research An Internal Perspective

1. Propagation Research An Internal Perspective

2. THE VIEWPOINT

3. The licensing process R U L E S Application Issue Technical assignment tools

4. Technical software The technical computing and propagation modelling unit

5. SG 3 T C P M Research Models Testing Measurements

6. THE TASK

7. 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

8. 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.

9. Wanted and unwanted signals (8 combinations for two point-to-point links)

10. 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.

11. LIMITATIONSOFPRESENT METHODS

12. No correlation model for signal variations What is thecorrelation betweensignal variationson paths d1 and d2? How does it vary with angle ‘A’, frequency, topography, climate,and % time ?

13. No correlation model for signal variations What is thecorrelation betweensignal variationson paths d1 and d2? How does it vary with angle ‘A’, frequency, topography, climate,and % time ? At present there is insufficient information for a practical assignment model. Conservativeassumptions must be made

14. Rain modelling for different climates The ‘CCIR’ rain zones show wide variations of rain climate.

15. Rain modelling for different climates The ‘CCIR’ rain zones show wide variations of rain climate. P.530 uses a singletime-variability distribution

16. Rain modelling for different paths No models take account of the spatial structure of rain in relation to path length and orientation

17. 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.

18. NEW REQUIREMENTS

19. 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.

20. 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

21. CONCERNS

22. CONCERN 1 BUDGETSA change in emphasis towards short and medium term objectives will make it difficult to budget for long-term measurement programmes.

23. CONCERN 2 EXPERTISEA work environment based around competitive tendering may mitigate against the retention of scientific expertise.

24. CONCERN 3 INTERNATIONALLack of participation by appropriate experts damages the process of internationally standardising propagation models.

25. CONCERN 4 THE BLUE SKYIn radiowave propagation,the curiosity-driven researcher will become an endangered species.

26. IT IS HOPED THAT THIS IS NOT THE END

27. IT ISN’T TECHNICALAPPENDIX

28. Wantedandunwantedsignals 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%.