Rainer Grosskopf Institut für Rundfunktechnik GmbH Propagation Considerations Overview of the activities within Task Group 6/8 BR Information Meeting on RRC-04/05 Rainer Grosskopf Institut für Rundfunktechnik GmbH

Propagation Considerations History Recommendation ITU-R P.1546 Propagation curves for non-European areas Requirements for terrain data Receiving antenna height loss correction Miscellaneous Conclusions

Introduction It seemed to be a simple task to provide propagation information for the planning to be undertaken by the RRC 04/05 There is just one ITU-R-Recommendation dealing with propagation for terrestrial point-to-area services in the frequency range 30 MHz to 3GHz Recommendation ITU-R P.1546 (replacing former Recs. 370, 529, 1146) Unfortunately the Task Group 6/8 did not fully support that idea

History Chairman’s Report, Doc. 14 (Jan 2002) The recommended point-to-area prediction method for the planning to be undertaken by the RRC is Recommendation ITU-R P.1546 - Method for point-to-area predictions for terrestrial services in the frequency range 30 MHz to 3 000 MHz Task Group 6/8 is of the opinion that this will be a satisfactory basis for developing a plan by the Conference

History Chairman’s Report, Doc. 142 (July 2003) The currently recommended point-to-area prediction method for the planning to be undertaken by the RRC is Recommendation ITU-R P.1546 - Method for point-to-area predictions for terrestrial services in the frequency range 30 MHz to 3 000 MHz Task Group 6/8 is of the opinion that this will be a satisfactory basis for developing a plan by the Conference

History But life was not as easy as it looks like Some countries and/or delegates wished to use the former Rec. 370 the GE89 curves for their regions (Africa) curves based on former Rec. 370 for T-DAB planning in Band III (CEPT) Rec. 1546 only in Band V path specific methods with terrain profile data

History Unfortunately there are still some anomalies in Rec. 1546 WP 3K is aware of the problem and works to solve it The main problem is the mixed land-sea path approach WP 3K tried to avoid the mixed land-sea path anomaly (unphysical recovery effect) in former Rec. 370 But new anomalies were built in by the new approach Unfortunately there are still some anomalies in Rec. 1546 (also in former Rec. 370 - but nobody cares)

Recommendation ITU-R P.1546 Extended range of applicability : All frequencies between 30 to 3000 MHz Distances between 1 to 1000 km All time percentages between 1% and 50% New curves for 10 m and 20 m transmitting antenna height h1 Method for point-to-area predictions for terrestrial services in the frequency range 30 MHz to 3 000 MHz

Recommendation ITU-R P.1546 Curves are considered applicable in temperate climates Variation of field strength with distance is to a large extent controlled by the vertical refractivity gradient Rec. 453 contains global database of the vertical refractivity gradients dN in N-units/km in the lowest 65 m of the atmosphere (in electronic form) Applicable for all climatic regions of the world :

Recommendation ITU-R P.453 dN values for 1 % of time

Recommendation ITU-R P.1546 The field strength curves of Rec. 1546 are considered to represent temperate climate with a reference value of gradient dN0 , e.g. dN0= - 43.3/ -141.9/ -301.3 N-units/km for 50/ 10/ 1 % of time For a different radio-climatic region of the world, calculate the difference in gradient  = dN0 – dN  is used to adjust curves for other climatic regions

Curves for non-European areas Propagation curves are needed for regions prone to extreme super-refractivity and ducting To get a consistent set of propagation curves for various climatic regions it is advisable to use only one method Rec.1546 provides a procedure to extend the applicability of the field strength curves for various regions of the world This procedure was used to derive propagation curves for the geographical zones defined in Geneva 89

Curves for non-European areas dN-values were chosen in a way to fit the curves based on Rec.1546 as good as possible to the original curves of GE89 Parameters used to derive the new curves based on Rec.1546 for various climatic zones are Description of the geographical zones in GE89 Path type Refractivity gradient Effective transmitting antenna height

Curves for non-European areas Geographical division of the planning area into propagation zones GE89

Curves for non-European areas

Curves for non-European areas GE89 curves can be reproduced, largely, using the procedures for modifying the temperate zone curves found in Rec.1546 Necessary to adopt somewhat extreme values of dN (Rec.453) However, recent measurements in the Gulf area indicate: dN  –2000 for 1 % of time (-1780 lowest value in Rec. 453) The values of dN can be widely variable in any climatic zone RRC may find it advisable to recommend appropriate refractive index lapse rates as parameters in Rec.1546 for each Zone

Requirements for terrain data Rec.1546 can be used with or without terrain height data Worldwide terrain data (~1 km) are available: GLOBE Due to the increase in computation time it is not practical to use terrain data in the context of RRC calculations Detailed prediction methods can be used on a bilateral or multilateral agreement or for coverage area calculations Higher resolution of terrain data (~100 m) necessary

Requirements for terrain data Not intended to use TCA-correction in RRC calculations heff values should be provided by administrations Terrain data could be used to provide heff values Ground cover data (urban, open) not necessarily needed Type of propagation path, such as land, sea or mixed land-sea paths can be derived from digital maps, such as IDWM Information on cold sea/warm sea divisions and geographic data for other propagation areas are needed

Receiving antenna height loss correction For planning purposes the ground cover at rx is not known Receiving antenna at 10 m in open area is assumed Height loss correction for a receiving height of 1.5 m a.g.l. Height loss from 10 m to 1.5 m is approximately: 13 dB at VHF and 16 dB at UHF (Rec. 1546, former 370) For planning purposes, other values may be used In bilateral negotiations when the ground cover type is known, the height loss correction formula may be used (Rec.1546)

Miscellaneous Several subsections did not cause much discussion Mixed paths over Zones of different propagation characteristics Prediction of wanted and unwanted signal levels Location statistics Propagation information for shared services

Conclusions Most discussions were on choice of prediction method Final decision will be made at first session of RRC in 2004 Factors influencing the choice of a prediction method Impact on existing plans Usage of various methods may be confusing Desirable to have one single method for the whole planning area and for all frequency bands  Rec.1546 However, Rec.1546 has still some anomalies

Conclusions Alternative methods in the Report to RRC are: Recommendation ITU-R P.1546 Curves based on Rec.1546 for various climatic zones Former Recommendation ITU-R P.370 (used for ST61) GE89 curves based on former Rec.370 (derived and used for the planning in the African Broadcasting Area) VHF curves based on former Rec.370 (derived and used for T-DAB allotment planning in Wiesbaden 95

Conclusions Further alternative: There is still a lack of propagation data in some parts of the planning area affected by ducting phenomena (e.g. the Gulf, the Red Sea and the East Mediterranean area) If any new reliable data for those areas show anomalies with the prediction methods used by the Conference Propagation predictions for requirements affected are to be re-calculated and the matter dealt with as the RRC decides

Acknowledgement I would like to thank all participants of TG 6/8 and WP 3K for their contributions and fruitful discussions Good luck to WP 3K in November Good luck to all those who will participate in the first session of the RRC in 2004 - and make wise decisions