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9. GSM network operators, subscriptions and services
The GD-01 US support several services in the GSM network. In order to get the unit
to work properly its important that the GSM service used in a specific application also
is enabled on the subscription (the SIM card).
When ordering a SIM card from a network operator its necessary to confirm that the
specific service needed for the application is enabled before trying to set up the commu-
nication link.
The implementations of the networks may also differ slightly from network to network.
Hints:
… When using a GSM modem in a fixed installation its in most cases a good idea to
disable the PIN code on the SIM card. In some GSM operators’ subscriptions its not
possible to disable the PIN code.This means that every time the unit is restarted, the
SIM card wants to have the PIN code before it can register to the GSM network and
work properly. However, most of the GSM network operators allow the user to dis-
able the PIN code and the SIM card security is in most cases sufficient when the unit
is installed in a restricted and locked area.
… When using the CSD service its important to confirm with the operator that the
service is enabled. Some networks do not support all the data rates supported by
the GD-01 US.
… When using a GSM modem in another GSM operators network its important
to check the roaming agreements between the “home” network operator
(the operator that provided the SIM card) and the other network operator.
… The coverage area of a specific network may not be sufficient for a reliable connection
on a specific place of installation. Several network operators may cover the same area
and it could be a good idea to contact other operators to see which network opera-
tor that provide the best GSM signal strength.
… When using a GSM modem in a fixed location, the network could be equipped with
a functionality that de-registers mobile stations that do not originate or receives any
connections.When a modem not is registered its not possible to make any outgoing
or incoming connections. Some networks de-registers a fixed “idle” user after 2–3
weeks and some other network operators does not have this functionality at all.
However, this problem can be solved with an AT-command <AT+WRST> that allows
the user to configure a timeout period after which the unit will make a reset and re-
register to the network. Please refer to the AT-command listing in the AT-Command
guide.The network operator should also be able to provide information whether this
function is enabled or not.
