azimuth and tilt optimization.pptx

Antenna Tilt, Azimuth Optimization

Information Security Level 1 – Confidential© 2014 – Proprietary and Confidential Information of Amdocs2

Introduction

The tilt is used when we want to reduce interference and/or coverage in some specific areas, having each cell to meet only its designed area.

Before we talk about tilt, it is necessary to talk about another very important concept: the antennas radiation diagram.


Antenna Radiation Diagram

The antenna irradiation diagram is a graphical representation of how the signal is spread

through that antenna, in all directions

An example of a 3D diagram of an antenna (in this case, a directional antenna with horizontal beamwidth of 65 degrees).

The representation shows, in a simplified form, the gain of the signal on each of these directions. From the center point of the X, Y and Z axis, we have the gain in all directions.

The representation shows, in a simplified form, the gain of the signal on each of these directions. From the center point of the X, Y and Z axis, we have the gain in all directions.


Antenna Radiation DiagramThe diagram of antenna 'from above', and also 'aside', we would see something like the one shown below.

These are the Horizontal (viewed from above) and Vertical (viewed from the side) diagrams of the antenna.

• The 'straight lines' tells us the direction (azimuth) – as the numbers 0, 90, 180 and 270 in the figures above.

• And the 'curves' or 'circles' tells us the gain in that direction (for example, the larger circle tells you where the antenna achieves a gain of 15 db).


Effects of Tilt on radiation Pattern

According to the applied tilt, we'll have a different modified diagram, i.e. we affect the coverage area. For example, if we apply an electrical tilt of 10 degrees to antenna shown above, its diagrams are as shown below.

The most important here is to understand this 'concept', and be able to imagine how would the 3D model be, a combination of its Horizontal and Vertical diagrams.


TiltsThe tilt represents the inclination or angle of the antenna to its axis.

MT ET

The mechanical tilt is very easy to be understood: tilting the antenna, through specific accessories on its bracket, without changing the phase of the input signal, the diagram (and consequently the signal propagation directions) is modified.

And for the electrical tilt, the modification of the diagram is obtained by changing the characteristics of signal phase of each element of the antenna, as seen below.


Changes in Radiation diagrams: depends on the Tilt Type


Tilting (Coverage prediction)

With the mechanical tilt, the coverage area is reduced in central direction, but the coverage area in side directions are increased.

With the electrical tilt, the coverage area suffers a uniform reduction in the direction of the antenna azimuth, that is, the gain is reduced uniformly.

Conclusion: the advantages of one tilt type to another tilt type are very based on its application – when one of the above two result is desired/required.But in General, the basic concept of tilt is that when we apply the tilt to an antenna, we improve the signal in areas close to the site, and reduced the coverage in more remote locations. In other words, when we're adjusting the tilt we seek a signal as strong as possible in areas of interest (where the traffic must be), and similarly, a signal the weakest as possible beyond the borders of the cell.


Basic Formula to Calculate the tilt

Angle = ArcTAN (Height / Distance)

Note: the height and distance must be in the same measurement units


ET and MT On antenna

Mechanical Tilt

Adjustment option

Electrical Tilt

Adjustment option


Recommendations• The main recommendation to be followed when applying tilts, is to use it with caution. Although the tilt

can reduce interference, it can also reduce coverage, especially in indoor locations.

• So, calculations (and measurements) must be made to predict (and check) the results, and if that means coverage loss, we should re-evaluate the tilt.

• It is a good practice to define some 'same' typical values (default) of tilt to be applied on the network cells, varying only based on region, cell size, and antennas heights and types.

• It is recommended not to use too aggressive values: it is better to start with a small tilt in all cells, and then go making any adjustments as needed to improve coverage/interference.

• When using mechanical tilt, remember that the horizontal beamwidth is wider to the antenna sides, which can represent a problem in C/I ratio in the coverage of neighboring cells.

• Always make a local verification, after changing any tilt, by less than it has been. This means assessing the coverage and quality in the area of the changed cell, and also in the affected region. Always remember that a problem may have been solved ... but another may have arisen!


Practical Scenario (Highway 2 PA-1)

Pre PCI

Post PCI

Pre CINR

Post CINR

As We can See in the Marked area lot of Server

are serving on the Highway As a result the interference

level is quite high

After Downtilting the Overshooters we have

dedicated Server on the road and interference got

decreased


Practical Scenario (Highway 2 PA-1)

Pre Servers

Post CINR

Post Servers

Problem Area Category Site Name Details Comments Action Site Action Cell

PA-1 AR 33433LN1 Poor Downlink Quality Down Tilt 33433LN1 S2 (PCI= 352) from M-6 / E-10 to M-0 / E-10 33433LN1 112

PA-1 AR 330M1LN1 Poor Downlink Quality Down Tilt 330M1LN1 S3 (PCI= 200) from M-6 / E-10 to M-6 / E-15 330M1LN1 113

PA-1 AR 330H7LN1 Poor Downlink Quality Down Tilt 330H7LN1 S3 (PCI= 83) from M-8 / E-4 to M-8 / E-8 330H7LN1 113

PA-1 AR 33477LN1 Poor Downlink Quality Down Tilt 33477LN1 S2 (PCI= 217) from M-6 / E-12 to M-6 / E-15 33477LN1 112

PA-1 CR 330M1LN1 Poor Downlink QualityReduce Power dlcellPwrred from 0 to 40 for 330M1LN1 S3

(PCI=200) . 330M1LN1 113


FootPrint Comparison

Post

Post Servers

Pre

Post

Pre

Post

Pre

Post

Pre


Final Tips

A final tip is when applying tilts in antennas with more than one band.

This is because in different frequency bands, we have different propagation losses. For this reason, antenna that allow more than one band has different propagation diagrams, and above all, different gains and electrical tilt range.

Suppose as an example an antenna that has the band X, the lower, and a band Y, highest.Analyzing the characteristics of this specific antenna, you'll see that the ranges of electrical tilt are different for each band.

For example, for this same dual antenna we can have:X band: electrical tilt range from 0 to 10 degrees.Y band: electrical tilt range from 0 to 6 degrees.

The gain of the lower band is always smaller, like to 'adjust' the smaller loss that this band has in relation to each other. In this way, we can achieve a coverage area roughly equal on both bands – of course if we use 'equivalent' tilts.


Final Tips

But in the example above, the maximum is 10 and 6. What would be equivalent tilt?

So the tip is this: always pay attention to the correlation of tilts between antennas with more than one band being transmitted!

The suggestion is to maintain an auxiliary table, with the correlation of these pre-defined values.Thus, for the electrical tilt of a given cell:

X Band ET = 0 (no tilt), then Y Band ET = 0 (no tilt). Ok.X Band ET = 10 (maximum possible tilt), then Y Band ET = 6 (maximum possible tilt). Ok.X Band ET = 5. And there? By correlation, Y Band ET = 3!

Obviously, this relationship is not always a 'rule', because it depends on each band specific diagrams and how each one will reach the areas of interest.

But worth pay attention to not to end up applying the maximum tilt in a band (Y ET = 6), and the 'same' (X ET = 6) in another band – because even though they have the same 'value', actually they're not 'equivalent'.

So Based on that a correlation Table can be created based on the bands used by the antennas


Antennas with details (Used in TWM Network)

Antenna Specification


Thank You

azimuth and tilt optimization.pptx

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