# Presentation: 664929

## Testing of “Low Frequency” P.452Against DataLow frequencies, Low time percentages

**K H Craig**

## Low Frequency P.452

- A “low frequency” extension of P.452 proposed in 3K/132
- This model is just P.452-12 with the lower frequency limit removed
- No other changes
- It compared favourably with P.1546, but
- There were no data comparisons
- There was no testing below 1% time
- Low frequency (<700MHz) and low time percentage (<50%) testing
- Used ITU-R P.311 Table VI-1
- Old data (Ron Sandell, BBC)
- Frequencies: Band 1-7 (30-3000 MHz)
- Time percentages: [99.9, 99, 90,] 50, 10, 5, 3, 1, 0.5, 0.3, 0.1, 0.01
**“****The technique adopted underestimated the short-percentage time field strengths at the majority of receiving locations” **
**“****Analyses of measurements obtained throughout the 24 hour day can be significantly higher than those confined to the original broadcasting hours”**

## Key to Scatter Plots

- Colour of points is based on the P.452 identification of path type:
-  black:	line-of-sight
-  red:	transhorizon, diffraction dominates
-  green:	transhorizon, troposcatter dominates
-  blue:	transhorizon, ducting dominates

## P.452 v P.1546

- 2000 MHz
- 30 MHz

- 50%		        1%

## P.452 v P.1546

## ITU-R P.311 Table VI-1

- Only European region included
- Path length distribution
- Time percentage distribution
- Frequency distribution :

## P.452 v Measurements

- 2300 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 1647 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 752 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 536 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 183 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 90 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## P.452 v Measurements

- 54 MHz

- 0.1%		        0.01%

- 50%		        10%		1%

## Statistics: P.452

- Means
- Low time percentage data contaminated by day/night sampling issue
- Standard deviations
- Number of paths
- 7555 total

## Statistics: P.1546

- Means
**Model minimum time percentage is 1%**
- Low time percentage data contamination
- Standard deviations
- Number of paths
- 7555 total

## P.452 v P.1546 (50% – 0.01%)

- P.452
- Mean error (all data):  – 5.2dB
- SD:  14.1dB

- P.1546
- Mean error (all data):  7.9dB
- SD:  13.6dB

## P.452 v P.1546(50% – 1%)

- P.452
- Mean error (all data):  – 2.8dB
- SD:  12.8dB

- P.1546
- Mean error (all data):  5.2dB
- SD:  12.1dB

## Conclusions

- Low frequency P.452 fits the data down to 1% of the time
- At least as well as P.1546
- P.452 tends to give lower losses than the data while P.1546 gives higher losses than the data
- But the diurnal bias in the data is expected to give losses that are too high (misses night-time enhancements)
- So P.452 appears to have the “correct” bias
- There is no evidence that the P.452 models are misbehaving at frequencies below 700 MHz
- Certainly for time percentages from 50% to 1%
- Possibly even at time percentages from 1% to 0.01%
- Questions
- How do the other candidate models do at low time percentages?
- Are there measurements that do not have the day/night contamination?