Recent Evolution of ITU Method for Prediction of Multipath Fading on Terrestrial Microwave Links
Bibliographic record
Abstract
Three methods are commonly used to predict multipath fading on terrestrial line- of-sight (LOS) links namely Barnett-Vigants and Morita methods used respectively in North America and Japan, and the worldwide ITU method. This later gains in importance even in North America and in Japan, due to the regular updates proposed by Study Group 3 of the ITU Radiocommunications sector. The ITU recommendation, ITU-R P.530 provides guidelines based on fading measurements of 251 links in various geoclimatic regions. Since 1978, thirteen revisions were proposed. The paper reviews the evolution of ITU-R P.530 from 1997 to 2009 with focus on the difierence between the last two revisions (Rev. 12 versus Rev. 13). These difierences concern mainly the geoclimatic factor, which depends on the refractivity gradient and the terrain roughness, and the multipath fade occurrence factor that afiects worst month outage probability. The paper also presents parametric studies carried out using our prediction tool, Microwave link simulator, to determine the critical parameters afiecting link performance. In our studies, 20 links located in Quebec, Canada, are designed based on real-world parameters. The detailed link proflles are known and refractivity gradients are extracted from ITU database according to ITU-R P.453-9. Climatic conditions are also taken into account using local rain database. The results of this work show that three climatic parameters, namely rain intensity, refractivity gradient and annual mean temperature are critical. Likewise for equipments, radio signature and antenna cross-polarization discrimination highly reduce the overall performance in terms of link availability. Finally, two year measurements data of flve links are analysed. The results show a good agreement with ITU-R P.530-13.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.002 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".