An immobile installation is a device that does not move during its deployment. Vehicles
and people are mobile.
The first thing you need to do is create a collection of pay as you go sims with
2G and 3G access enabled. These sims can be obtained usually free of charge or for
a small fee from your mobile operator or phone shop. The next thing to do is go onto
the internet for each mobile operator and check out the coverage maps.
The coverage checkers will give you a rough idea of what networks are available.
However this is a rough guide as to the networks and signal power that will be available
on site. The reason for this is because there are many obstacles that can degrade
and alter a cellular signal. Metal beams, concrete, trees in leaf can all seriously
attenuate a mobile signal. Heavy machinery especially motors can cause radio frequency
interference. In other places cell phone signals may actually be jammed. Cell phones
may be jammed in public places such as theatres or cinemas and within the vicinity
of penal institutions.
In certain areas the coverage checking map will be inaccurate or misleading. On a
large industrial / military sites there might not be any data showing that mobile
phone coverage exists as no one has been allowed to go there and measure it.
In order to site a device a site visit is essential, this can be done using the Ezee3G
software and a laptop, plus Samba 3G modem. A hand held GPS device may also prove
useful although bear in mind that GPS does not work indoors unless you are near a
window. See performing a site measurement.
The USB specification allows you to have a 3 meter USB cable between your USB device
and host computer system. The advantage of an external modem is that it can be moved
around to get better reception.
If you are siting your device inside a building try to site it as high as you can
and as near to a window as is possible. You could even stick the modem to the window.
If you find that your installation point is in a basement or cellar mobile phone
signals won’t penetrate beneath the ground. In these cases it will be necessary to
use a device called a USB extender. A USB extender should allow you to place the
modem much further away from the host computer. Make sure you buy an extender which
supports USB 2, unfortunately these are a lot more expensive than USB 1.1 extenders
at the moment.
If your modem does not support GPS the a hand held GPS device will be useful.