Toplevel Technologies is experienced
in using CDMA, GSM, and Serial RF modem technologies.
CDMA is a US standard developed by Qualcomm and
has much coverage in the United States.
CDMA was developed mainly for the US market and
is well established. Verizon is the main carrier
and we have found the system very robust when
it comes to data communications. We have experience
with circuit switched data on CDMA, and always-on
packet switched 1xRTT systems using both dynamic
and static IP address modes.
One issue to watch out for is the Preferred Roaming
List ( PRL ) used by CDMA. Make sure your modem
can automatically update the PRL especially if
using a dynamic IP address.
We have worked with GSM circuit switched data
in the past. At the time, it was necessary to
use a special "data number" to improve
connection rates. According to some sources there
were issues going across older networks. The GSM
system was ultimately tied together by T-Mobile.
The GPRS system is T-Mobile’s standard for
consumer based packet switched data on their system.
It is quite stable when using GPRS phone modems
to access the Internet.
The main difference between landline and cellular
RF modems is the wireless modem need to understand
its own connection quality on the system. So,
we are always concerned with Relative Signal Strength
Indication (RSSI) and network registration. (It
is possible to acquire good RSSI while not being
registered on the network).
Command and control issues are similar between
cellular modems and landline modems. Both have
the standard command mode where you tell the modem
what to do, and then there is data mode for data
Cellular modems are ideal for transmitting data
over long distances, when a landline is unavailable.
They are also ideal for mobile data collection
like fleet management, and where one set of data
must be compared to a remote set of data while
in motion. There is an associated monthly service
fee. Unlike cell phones you can sign up for an
account and add or remove individual cellular
modems as required. . The use of cellular modem
applications is constantly evolving as new methods
are devised for new applications.