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1 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Investigation of how the Ericsson prediction models works together with antenna tilt

1 INTRODUCTION

In this document, an investigation is presented regarding the following subject: will antenna tilt work together with the Ericsson radio wave propagation models? Tests have been performed for Algorithm 9999 as well as the Urban Model and the tool is WCDMA Planner 3.2. Drive test data from Guildford using different tilt angles have been used in this investigation. The map database used is a 50 meters database including height and clutter information but no building data. This means that only the half-screen part of the Urban Model could be used.

2 GENERAL

When downtilting an antenna, the signal strength will decrease in the cell. This effect is depending on the distance from the site, the topography in the area as well as the antenna pattern. The actual horizontal and vertical patterns used in the predictions are given as follows:

Figure 1 Horizontal antenna pattern

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EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Figure 2 Vertical antenna pattern

The horizontal opening angle is 63° and the vertical opening angle is 6.5°. The antenna gain is 18 dBi.

The difference between measured signal strength values for the case with zero tilt and the case with a tilt of 2° will look as follows for a typical case:

-30

-20

-10

0

10

20

30

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2000 2500 3000 3500 4000

Distance [m]

Diff

eren

ce ti

lt 0

- tilt

2 [d

B]

Figure 3 Difference in signal strength values for 0° tilt compared to 2° tilt

As seen, the values of the differences between the un-tilted and tilted case are very spread, but more than 50 % of the values fall within the range of 4 – 7 dB. Thus this figure should be considered as a typical value of the difference between the un-tilted and tilted case.

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3 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

3 MEASUREMENT AREA

The measurements were performed in Guildford, UK, southwest of London, and the frequency was 2100 MHz, i.e. in the UMTS band. The antenna heights were 15 m for cells 123 and 131 and 21 m for cell 195.

The area where the measurements were taken in general was low built with typically British semi-detached two-three storey houses with an approximate height of 10-15 m. Thus the antenna heights exceeded or were in the same level as the clutter heights in this case.

4 RESULT

The idea is as follows: if a prediction model is optimised for a specific result, e.g. zero tilt, it should also give a satisfactory result even if the tilt angle is changed.

Three different cells are used in the investigation and the models have been tuned for zero tilt. Then the result is compared when the tilt angle has been changed to 2°. One complication is that the drive routes are not completely comparable for the two cases; in general less measurement data are collected for the 2° cases.

4.1 ALGORITHM 9999

4.1.1 CELL 123

Algorithm 9999 was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.0

Standard deviation: 5.9

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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4 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

-130

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Samples

Sign

al s

tren

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[dB

]

Measured SSPredicted SS

Figure 4 The predicted signal strength compared to the measured signal strength for cell 123, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: -0.5

Standard deviation: 6.9

4.1.2 CELL 131

Algorithm 9999 was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.0

Standard deviation: 5.9

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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5 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

-130

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Samples

Sign

al s

tren

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[dB

]

Measured SSPredicted SS

Figure 5 The predicted signal strength compared to the measured signal strength for cell 131, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: 1.5

Standard deviation: 4.5

4.1.3 CELL 195

Algorithm 9999 was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.0

Standard deviation: 8.5

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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6 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

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-50

Samples

Sign

al s

tren

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[dB

]

Measured SSPredicted SS

Figure 6 The predicted signal strength compared to the measured signal strength for cell 195, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: -2.9

Standard deviation: 7.9

4.2 URBAN MODEL

4.2.1 CELL 123

The Urban Model was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.0

Standard deviation: 6.1

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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7 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

-130

-120

-110

-100

-90

-80

-70

Samples

Sign

al s

tren

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[dB

]

Measured SSPredicted SS

Figure 7 The predicted signal strength compared to the measured signal strength for cell 123, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: -0.75

Standard deviation: 6.3

4.2.2 CELL 131

The Urban Model was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.1

Standard deviation: 6.8

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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8 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

-130

-120

-110

-100

-90

-80

-70

Samples

Sign

al s

tren

gth

[dB

]

Measured SSPredicted SS

Figure 8 The predicted signal strength compared to the measured signal strength for cell 131, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: 0.7

Standard deviation: 5.2

4.2.3 CELL 195

The Urban Model was tuned for the drive route with zero tilt. The following statistical values were obtained:

Mean error: 0.0

Standard deviation: 10.1

The prediction was then performed for a tilt angle of 2° and compared to the measurements from the drive route for 2° tilt.

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9 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

Tilt 2°

-110

-100

-90

-80

-70

-60

-50

Samples

Sign

al s

tren

gth

[dB

]

Measured SSPredicted SS

Figure 9 The predicted signal strength compared to the measured signal strength for cell 195, for a tilt angle of 2°

The statistical values for the 2° tilt drive route were as follows:

Mean error: 0.1

Standard deviation: 7.9

5 CONCLUSION

The result when changing tilting angle is not completely perfect, i.e. in some cases the predicted result is underestimated or overestimated compared to measurements. However, the agreement has shown to be rather good; no major deviations have been found in the comparisons. The results for Algorithm 9999 and the Urban Model are comparable, but in most cases the Urban Model will give slightly better result.

Here also must be noted that not exactly the same data points for the different tilt cases are used for the comparison. In the ideal case, exactly the same drive routes have been used for the tilted case, as for the un-tilted case, which was not possible to achieve. This circumstance may have some effect on the result.

This means that using predictions in a tool like TEMS Cell Planner will give a good hint of the effect of tilting antennas in a network. Thus some time for drive testing using different tilting angles can be saved.

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10 (10) Prepared (also subject responsible if other) No.

EAB/ZG/ND Maria Thiessen EAB/ZG-03:000150 Uen Approved Checked Date Rev Reference

EAB/ZG/ND [Åsa Svedenheim] ERAJEB 2003-12-09 A

6 FURTHER WORK

This investigation is just a first look. In order to have a complete view of how well the tilting function in TEMS Cell Planner is performing, the following work needs to be done:

• Investigations for various types of environments, e.g. flat, hilly, urban, dense urban areas, areas with high rise buildings etc.

• Investigations for different map resolutions, including high resolution data containing 3D building information.

• Investigations for different tilting angles, e.g. 2° tilt, 4° tilt, 6° tilt, 8° tilt, 10° tilt etc.

• Investigations also for different degrees of electrical tilt.

Furthermore, when performing the drive tests, exactly the same drive routes should if possible be chosen for the different tilt cases.