CS-3G Digital Transceiver Kits (including the COM111 modem)
8
vary from 5 up to 20 mA. The logger and interfaces to the modem also
consume additional current when the modem is active.
Because the power use can be relatively high compared to the quiescent
power use of most Campbell dataloggers careful consideration must be made
of the likely power use versus the available power on site when running a
remote system.
Please see the relevant sections below under the IP and GSM dial-up
sections to see ways of minimising the power use.
3.3 Network coverage
One of the main advantages of using a cell phone network is being able to
set up a communications link to a data logger virtually anywhere without
installing land or telephone lines. However, this only applies if a suitable
network covers your installation site.
Within the Europe the coverage of many networks is good in most areas.
However, coverage in remote areas can still be quite poor and sometimes only
2G coverage is available. Unless coverage is known to be good at the proposed
site, we strongly recommended that you test the coverage using a standard
handset (on the same network as the COM111 modem is to be used) to
measure the exact signal strength. Make sure the phone is reporting good
signal strength with the correct type of data connection available, noting some
networks will switch to another network for voice only when there is no signal
on the providers network. The COM111 does not work on 4G networks.
Even areas shown as having good coverage on network maps
can have ‘holes’ due to local interference or other technical
reasons, so site testing is recommended.
In areas of normal signal strength the COM111 modem can be used with a
small, low gain, wideband antenna (as supplied in the CS-3G package).
However, if the signal strength is marginal it may be possible to improve
reception using a raised and/or a higher gain antenna. Poor quality reception
will normally lead to breaks in communication or result in the PC software
having to make multiple requests to ensure uncorrupted data is collected.
This will not usually lead to data loss or corruption, but may result in longer
calls and thus higher call charges.
The network provider will be able to offer advice on coverage problems.
Campbell Scientific can also offer further advice on suitable antennae to suit
the application.
4.
Using GPRS and 3G IP communications
This section discusses the principles of using the COM111 for GPRS and 3G
data transfer in more detail.
4.1 Using GPRS and 3G IP communications introduction
In recent years GPRS (General Packet Radio Service) on 2G networks
(GSM/Edge) and 3G (UTMS) services have become a standard for “always-
NOTE