2. 2
Global Positing Timing Satellite Timing
Timing and synchronization is so important
to the current Macro cell technologies that
without it a Service Provider Client would
be unable to process a mobile call and
hand-off from site to site.
The time and alignment delta between macro cell sites is
better than 1 millisecond (1 thousandth of a second)
alignment and it becomes more like 1 millionth of a second
precision when you include Small Cell.
Ted J. Pappas
3. 3
The GPS Signal
The GPS signals are actually two (2) carriers. The L1 carrier
is 1575.42 MHz and carries both the status message and a
pseudo-random code for timing. The L2 carrier is 1227.60
MHz and is used for the more precise military pseudo-random
code.
The actual signal is so complicated that it
almost looks like random electrical noise.
Hence the name "Pseudo-Random."
There are several good reasons for that complexity:
First, the complex pattern helps make sure that the
receiver doesn't accidentally sync up to some other
signal. The patterns are so complex that it's highly
unlikely that a stray signal will have exactly the
same shape.
Ted J. Pappas
4. 4
The GPS Antenna and Cable
The GPS antenna has a high-gain (26
dB) Low Noise Amplifier built in.
There are distance limitations on
cable length (distance based upon
cable type) that may require offset
calculations to be provided to the
Mobile Switching Center or entered
into the local “integration” software at
the cell site
Ted J. Pappas
5. 5
GPS Antenna Placement
The need for correct GPS Antenna placement has NEVER been more important
Unlike a TV Satellite Antenna who receives
its signal from a single direction the GPS
Antenna receives multiple signals from
multiple directions
The best placement for the GPS Antenna is as
close to the GPS Equipment as possible while
provide a 270 degree view of the sky
Ted J. Pappas
6. 6
GPS Antenna Placement
Where does it go?
The antenna should be installed to provide the best
available view of the entire sky.
It is recommended to have a clear view of the sky
above a 30 degrees from the horizontal in all
directions, and above 10 degrees from the horizontal
with a southern view for northern latitudes and a
northern view for southern latitude sites.
To minimize any damage due to lightning, it is required
to always mount the antenna below the top of the
lightning rod by a distance greater than 6 feet.
The GPS antenna should also never be located more
than 6 feet away from a lightning rod in the horizontal
direction. This allows the Base Station Timing Module
to select the best combination of GPS satellites for
best performance.
Ted J. Pappas
7. 7
GPS Antenna Cable Length
At the GPS receive frequency loses at high in the GPS Cable and as
such requires a special “low Loss” cable (RG-58) and/or in-line
amplifier depending on distance / length.
The standard length cable that comes with the it is nominally 100
feet.
Cable runs longer than 100 feet may require another solution such
as offsets and in-line amplification.
Ted J. Pappas
8. 8
A Ground Plane?
It is recommended to use a ground plane in
the installation to minimize the signal
degradation due to reflections.
Fading may also be caused by reflected
signals from vertical surfaces which are
above the plane of the base of the antenna.
