# Presentation: 226807

## TESTING OF P.1812 DIFFRACTION MODELS WITH RESPECT TO MOBILE MEASUREMENT DATA

**Richard Rudd**
**3K1 correspondence group workshop**
**London, 11-13 March 2008**

## Background

**Testing of diffraction models against mobile measurements**
- Majority of P.1812 testing relates to paths of >10km and fixed receivers, typically 10m height
- Recent OFCOM-funded mobile measurements at 2-6 GHz
- Opportunity taken to examine performance of Deygout three-edge and Bullington models with respect to this data
**Caveats:**
- Majority of measurement data is outside intended frequency range of P.1812
- Is P.1812 intended to be used for such short paths?

## Measurement campaign

**Both fixed and mobile measurements**
**Frequencies of:**
- 2.4 GHz
- 3.4 GHz
- 5.7 GHz
**Total of 85 measurement ‘runs’**

## Measurement areas

**Measurements in four UK areas**
- Suburban Cheshire (fixed only)
- Rural Oxfordshire
- Winchester (small cathedral city)
- Croydon (dense urban area in London)

## 9th order distance correction

- 9th order distance correction

**Bullington implemented as per CGD-12**
- Includes taper to ensure free-space for LOS paths
**9th-order distance correction as per CGD-14, applied...**
- Additively, to CGD-12 algorithm
- As a substitute for existing distance term:

## Overall results

| Model | Mean | SD |
| --- | --- | --- |
| D3E | 2.36 | 10.22 |
| Bullington | -1.96 | 8.43 |
| Bullington+correction | 3.21 | 8.94 |
| Bullington sub correction | -4.64 | 7.90 |

*(But D3E as good as Bullington if related edges identified)*

## Assumed clutter heights

| Category | Original | ‘Tuned’ |
| --- | --- | --- |
| Sea, roads, fields, unknown | 0m | 4m |
| Woodland | 7m | 7m |
| Suburban | 8m | 9m |
| Urban | 10m | 10m |
| Dense Urban | 15m | 7m |

## Sensitivity to assumed clutter height

| model | Mean |  | SD |  |
| --- | --- | --- | --- | --- |
|  | original | tuned | original | tuned |
| D3E | -1.39 | 2.36 | 10.54 | 10.22 |
| Bullington | -5.36 | -1.96 | 8.90 | 8.43 |

**Tuning clutter heights improves the model performance **
**Not tuned for these models, but optimisation likely to be possible**

## Rural route (2.4 GHz)

## Winchester (5.7 GHz)

## Undulating rural route (5.7 GHz)

## Profile spacing

## Comments

**These comparisons may not be relevant to P.1812**
- Frequencies largely outside model range
- Paths (possibly) much shorter than intended applications
**Bullington performance is good**
- Avoids spurious edge issues with no apparent loss of detail
**But other comparisons show Bullington to fail on longer paths**
- Systematic understimate of spherical surface loss
- Deygout 3E gives realistic answers by non-physical means
**Making Bullington ‘look like’ D3E at longer distances may be one answer**
- Or one might ‘correct’ D3E to give better performance at short range

## Issues

**Not much data available for shorter, mobile paths**
- Clutter information a particular difficulty
- Need to tune ‘representative’ clutter heights
**Should this type of path be covered by P.1812?**
- Generally, what is the ‘specification’ for P.1812
**Is an empirical correction for long (spherical diffraction) paths the best approach?**
- Polynomial  or other correction to Bullington?
- ‘accidental’ fit of D3E?

## Thank you!

**Richard Rudd**
*Aegis Systems Limited*
*www.aegis-systems.co.uk*