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Cellular Modem vs. Digi Cellular Gateways
White Paper
What Are the Differences Between Cellular Modems and
Digi Connect
®
Cellular Products?
Although the Digi Connect® WAN family products are are able to perform most functions of a cellular modem, they actually
do much more. Digi Connect WAN family products are intelligent gateways with a full TCP/IP stack and embedded
Real Time Operating System (RTOS) which allow remote devices and networks to be natively integrated with IP devices and
applications across high-speed digital cellular networks.
Cellular modems operate in the voice channel. This means throughput is slow and airtime is expensive. In addition, cellular
modems typically require a one-to-one connection to an analog (POTS) modem connection at the opposite end of the
connection. Multiple connections require modem banks to which remote sites dial in.
Digi Connect WAN family products operate as true TCP/IP devices. They connect seamlessly to the cellular provider’s IP
network where only one WAN access point is required to connect thousands of devices.
One of the key differences is that applications can natively connect to remote devices using TCP/IP without having to use a
standard analog modem at both ends.
2
Features
What does it do?
Network
architecture
Air interface
Bandwidth
Connection
Carrier charge
TCP/IP stack
Local intelligence/
memory
Requires analog
(POTS) modem at
opposite end
Supported
applications
Network bridging
Special features
Cellular Modems
Dial in/out to other analog (POTS)
modems
Circuit Switched
CDPD (analog)
GSM (voice circuit)
CDMA (Circuit Switched)
Low-speed (14.4 max)
Dial in/out
Per minute (expensive voice plan)
No
No
Yes (except CDMA QNC)
Low bandwidth SCADA
No (except via serial PPP)
Can dial in to RAS server for low
speed IP connection
Digi Connect WAN Family
Ethernet-to-IP cellular
gateway/router
Packet switched
GPRS/EDGE/UMTS/HSDPA
CDMA/EV-DO
High-speed (up to 230 Kbps)
Always on
Per packet (inexpensive data plan)
Yes
8 MB RAM/2 MB Flash
No
High bandwidth SCADA & remote
network bridging
Yes
Digi SureLink™ persistent
connection
Routing/rewall features
Integration with
Digi Connectware® Manager
enterprise software
RealPort® COM port redirection
Modem emulation
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