Goodbye Rec. 370 Welcome Rec. 1546

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1 Goodbye Rec. 370 Welcome Rec LS Day 2002, Lichtenau Rainer Grosskopf Institut für Rundfunktechnik GmbH IRT R. Grosskopf 12 June

2 Goodbye Recommendation ITU-R P.370 Introduction Retrospect on Recommendation ITU-R P.370 New Recommendation ITU-R P.1546 (former DNR P.[BLM]) Comparison of Recommendation ITU-R P.1546 and Recommendation ITU-R P.370 Comparison with measurements Conclusion IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

3 Introduction Field strength prediction methods are needed for network planning, e.g. for Revision of Stockholm 61 Path specific methods (terrain data based) Still rather time consuming calculations No world-wide agreed method available (Broadcasting) Path general methods (ITU-Recs. 370, 1146, 529, 1546) Fast and easy to use Limited applicability IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

4 Introduction : Path general methods Various methods (Rec. 370, 529, 1146) for similar or even identical applications gave different answers (confusing) ITU developed Rec. P.1546 to overcome known limitations (e.g. frequency, distance range) and to combine the various methods to one unique method One path general method for point-to-area predictions for terrestrial services in the frequency range MHz IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

5 Retrospect on Recommendation P.370 Rec. 370 existed for 50 years Several revisions - but the fundamental idea remained Propagation curves for effective transmitter heights (37.5 m 1200 m) 10 m receiving antenna height (home reception) VHF and UHF range additional corrections based on terrain ( h, TCA) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

6 Retrospect on Recommendation P.370 Some shortcomings of Rec. 370 Curves start at 10 km Gap between VHF (30 to 250 MHz) and UHF (450 to 1000 MHz) range No curves for L-Band (1.5 GHz, T-DAB) Calculation of effective transmitting antenna height Recovery effect (unphysical) for mixed land sea paths Strange anomalies within set of curves IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

7 Recommendation ITU-R P.1546 Unique method for point-to-area predictions for terrestrial services in the frequency range 30 to 3000 MHz DNR P.[BLM] was adopted by the ITU-R Study Group 3 in June 2001 (Doc. 3/45) Seeking approval amongst Member States in Doc. 3/BL/26 Approved in October 2001 Now it is Recommendation ITU-R P.1546 IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

8 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 h 1 IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

9 Recommendation ITU-R P.1546 Application of Rec. P.1546 to yield unique results : Propagation curves are also provided in tabular form Formulas for interpolation and extrapolation of field strength as a function of distance, frequency, transmitter height, time percentage are given in Rec. P.1546 Step-by-step procedure to determine field strength is specified e.g. order of interpolation IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

10 Recommendation ITU-R P.1546 Overview of elements of Rec. P.1546 : Propagation curves for distance between 1 to 1000 km for : 100, 600, 2000 MHz 10, 20, 37.5, m transmitter height h 1 1, 10, 50% of time Land, cold sea, warm sea, (hot sea?) Interpolation and extrapolation possible IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

11 Recommendation ITU-R P.1546 Transmitting antenna height h 1 : Method takes account of effective height of the transmitting antenna (h eff as in Rec. 370) For distances d < 15 km the method also takes account of the height of the transmitter above ground h a h 1 to be used in calculations (in propagation curves) h 1 = h a for d 3 km h 1 = h a + (h eff -h a )(d-3)/12 for 3 km < d < 15 km h 1 = h eff for d 15 km IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

12 Recommendation ITU-R P.1546 Transmitting antenna height h 1 (mobile services): Where terrain information is available when propagation predictions are being made, h 1 is a function of distance h 1 = h a + (h b -h a ) d/15 for d < 15 km h b is the height of the antenna above terrain height averaged between 0.2 d and d km h a is antenna height above the ground cover in its vicinity IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

13 Recommendation ITU-R P.1546 Transmitting antenna height h 1 : Interpolation for 10 m < h 1 < 1200 m is as in Rec. 370 Extrapolation for h 1 > 1200 m is as in Rec. 370 Extrapolation for h 1 < 10 m is nearly identical to Rec. 370 (except for sea paths) For sea paths the procedure requires the distance at which the path has 0.6 of the first Fresnel zone just obstructed by the sea surface IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

14 Recommendation ITU-R P.1546 Reference receiving antenna height R (new concept): For land paths the curves give field-strength values for a reference receiving antenna at a height R, representative of the height of the ground cover surrounding the receiver Examples of reference heights are 30 m for a dense urban area 20 m for an urban area 10 m for a suburban area IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

15 Recommendation ITU-R P.1546 Reference receiving antenna height R : If the receiving antenna height, h 2, is different from R, a correction should be added to the field strength taken from the curve The correction depends on the ground cover The minimum value of R is 10 m (open areas) For sea paths the notional value of R is 10 m IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

16 Recommendation ITU-R P.1546 Example for reference receiving antenna height R : Receiving antenna height h 2 = 10 m in an urban area Correction of field strength F cur taken from curve is necessary F cur F rec h 2 =10m R=20 m f = 100 MHz h1 = 150 m d = 50 km Fcur = 58.3 db Frec = 53.0 db IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

17 Recommendation ITU-R P.1546 Example for reference receiving antenna height R : Receiving antenna height h 2 = 10 m in rural area No correction of field strength F cur taken from curve f = 100 MHz h1 = 150 m F rec = F cur h 2 =10m R=10 m d = 50 km Fcur = 58.3 db Frec = 58.3 db IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

18 Recommendation ITU-R P.1546 Terrain clearance angle (TCA) correction : Taking account of obstacles close to receiver site TCA R (m) 16 km Nearly identical to Rec. 370 Improvement for line-of-sight case IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

19 Recommendation ITU-R P.1546 Location variability refers to the spatial statistics of local ground cover variations including multipath variations (no path variations) is typically quoted for an area of approximately 100m x 100m Multipath fading is frequency selective. Thus knowledge of effective radio system bandwidth becomes important Field strength distribution due to ground cover variations over such an area is approximately lognormal IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

20 Recommendation ITU-R P.1546 Location variability : Nearly identical to Rec. 370 (broadcasting) Standard deviation for digital systems having a bandwidth of 1 MHz or greater, σ = 5.5 db for all frequencies Standard deviation for analogue systems depends on frequency f σ = K log(f) K = 5.1 for broadcasting IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

21 Recommendation ITU-R P.1546 Mixed land-sea paths : New approach based on Recommendation ITU-R P.452 Total path length over land d l is important E mix (dtot) = E sea (d tot ) {E land (d l ) - E sea (d l )} E = E mix (dtot) - E land (dtot) E = E land (dtot) + E * χ χ - interpolation factor to take account of long-range effect of land on propagation χ(α,β,d l, h 1 ) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

22 Recommendation ITU-R P.1546 Comments on mixed land-sea path model : The original UK TG 3-2 model is simply E mix (α =1) α = 0 applies the Rec. 452 land effect correction, except that here the total path length d tot is used rather than the longest contiguous land path length α in the range 0 to 1, depending on the desired long range behaviour of the model IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

23 Recommendation ITU-R P.1546 Applicable for all climatic regions of the world : new 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) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

24 Recommendation ITU-R P.1546 The field strength curves of Rec are considered to represent reference values of gradient dn 0 given by: dn 0 = N-units/km for 50% of time dn 0 = N-units/km for 10% of time dn 0 = N-units/km for 1% of time To adjust the field strength curves for a different radio-climatic region of the world, calculate the difference in gradient given by: = dn 0 -dn IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

25 Recommendation ITU-R P.1546 is used to adjust curves for other climatic regions: Temperate climates dn 0 = (t=1%) Most extreme value found in Rec. 453 dn = (t=1%) Field strength (dbuv/m) UHF Land 1% curves Tropical region Temperate climates Distance (km) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

26 Comparison of Rec and Rec. 370 Obvious differences between Rec. 370 and Rec which caused some discussions : Sea curves Mixed land-sea paths IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

27 Sea curves Comparison of sea curves for 600 MHz (Rec.1546) and UHF (Rec. 370) : Differences up to 20 db between Rec. 370 and Rec in the distance range km Field strength (dbuv/m) MHz, Cold Sea, t=50% Rec. P.1546 Free space Free space Rec. P.370 Rec. P.370 Distance (km) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

28 Sea curves The P.370 sea curves show a large variation in field strength with effective transmitter height in the range from 10 to 50km Over this range of distance, even the lowest height antenna has a line of sight path to the receiver, often without the first Fresnel zone touching the surface It is extremely difficult to find a propagation mechanism for these paths at 50% time that will give a 25 db difference at 10 km between the 37.5 and 1200m high transmitter curves as does in P.370 IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

29 Sea curves The new Rec sea curves are based on various calculations using Recommendation ITU-R P.452, a point-topoint prediction method taking into account physical effects such as diffraction, troposcatter and ducting With increasing distance line of sight, diffraction and ultimately troposcatter propagation is dominating (50% of time), resulting in a physical shape of the new sea curves IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

30 Sea curves The smaller time percentage sea curves of P.1546 were then constructed from blending together the short range (1 to 50 km ) regions of the 50% lines with the existing tails from P.370 ( km) Thereby a consistent set of sea curves was derived This would then allow a mixed path model to be derived that was not fatally flawed from the outset IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

31 Mixed land-sea paths Recommendation ITU-R P.370 : Approach is based on percentage of land and sea along the propagation path Shows a recovery effect which becomes very pronounced at higher frequencies The properties of this recovery effect are non-physical IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

32 Mixed land-sea paths Recommendation ITU-R P.1546 : Based on the model of Recommendation ITU-R P.452 Longest contiguous land path is important (duct may break down over land) Avoids the recovery effect and is monotonic with range Follows the slope of the sea curve with an offset based on the preceding land portion IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

33 Mixed land-sea paths Mixed path, 2 GHz, t=1%, h=37,5 m Field strength (dbuv/m) Land Sea Land Sea 1 Sea Land Rec. P.370 Rec. P.1546 Distance (km) see Doc. 3K/5 19 December 2000 IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

34 Comparison with measurements IRT did comparison of predictions with Rec. P.370 and Rec. P.1546 with a dataset of profiles and measurements from EBU Project Group B/TDP (Doc. 3K/6, 16 Jan 2001) B/TDP dataset contains 3364 profiles from 9 countries long distances low receiving antenna heights upper part of the UHF range sea-paths and mixed land-sea paths are not very well represented IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

35 Comparison with measurements Prediction error E = E predicted E measured Prediction method Mean prediction error (db) Standard deviation (db) Largest error (db) ITU-Rec. P with TCA-correction ITU-Rec. P with TCA-correction IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

36 Conclusion A new Recommendation ITU-R P.1546 was developed It is a unique Method for point-to-area predictions for terrestrial services in the frequency range 30 to 3000 MHz Rec is based on approaches of former Recs. 370, 529 (Okumura/Hata), 1146 and of the point-to-point prediction method Rec. 452 Investigations show an improved prediction accuracy for broadcasting applications Recommendation 370 does not exist any longer Good Bye IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

37 Conclusion Further testing of Rec is necessary, in particular for sea and mixed land-sea paths and for various climatic regions of the world EBU Project Group B/TDP will develop a software of the new Recommendation P.1546 for planning purposes This software should be the propagation software tool for the revision of Stockholm 1961 (RRC in 2004/2006) Software should be available end 2002 IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

38 Acknowledgement The author would like to thank the participants of ITU Working Party 3K in particular Eldon Haakinson/USA (former Chairman) Ken Hunt/EBU (Subgroup Chairman) ITU Task Group 3-2 in particular Paul McKenna/USA (Chairman) David Bacon/UK, Ken Hunt/EBU (Vice Chairmen) IRT R. Grosskopf Goodbye Rec. 370 Welcome Rec June

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