Selection of Antenna parameters:
Antenna parameters such as height, orientation and
tilt are so chosen to obtain the best possible coverage with the least possible
signal suppression.
Height: Height ranges from 20m
to 30m (for rooftop antennas) and 35m to 50m (for ground base towers) depending
upon the height of clutter and the area in
vicinity.
Orientation: Orientation of the antennas is the direction at which the specified
area to be covered. The orientation angle for the sectors is taken in
the clockwise direction considering north as the reference at 0°.
Tilt: This is done to carry
out the process of either decreasing or increasing the coverage area of a
sector. This is done to avoid interference arising out of the fact that the
sector under consideration is radiating out of the desired area of its coverage
and hence affecting other neighboring sectors.
Tilt is given by the following means:
·
Electrical tilt: This tilt is given by
changing the phase relations in between various elements of an antenna. If a down tilt is being given
electrically, then there will be a down tilt in both the front and the back
lobe of the antenna.
·
Mechanical tilt: This tilt is given manually by changing the angle
antenna makes with the vertical. If a down tilt is being given mechanically,
then there will be a down tilt in the front lobe but an up tilt in the
backlobe.
Mechanical
tilt is more often used than electrical tilt.
After simulating the above inputs planning tool can
be used to generate various images to check the resultant network. Some of the
important images that are used to analyze the network are as follows:
- Downlink best signal strength: The image provides a comprehensive knowledge
of the zones receiving signal sent out by Base Transceiver Station (BTS)
and the
amount of signal
received. This signal is the signal received by our handsets or Mobile Stations
(MS).
- Downlink best Server/Sector: Different antennas
of the site are called sectors. With the help of this image an RF engineer
can visualize the amount of signal that is being released by each sector
of the site.
The initial stage of planning and designing
the network is followed by a second stage of optimization of network.
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