Motorola V186 - Cell Phone - GSM System Planner Manual page 123

Communications
MDLC over Dialup Modem Configuration
The ACE3600 can be connected to dial-up modem. The user can configure the modem
from the RTU using the MDLC over Dialup port. A configuration modem string can be
defined in the Physical Layer to configure the modem. The modem configuration file
enables the user includes the configuration modem string and other AT commands. If no
modem configuration file exists, the configuration modem string will be used. If both
exist, the modem configuration file will be used.
MDLC over Dialup is different than MDLC over IP in the way it configures modem and
connects it. It is important to note that in many cases the same modem can work in both
modes, but the user must decide when configuring the port, what method to use. With
MDLC over Dialup, the modem is placed in circuit data mode, meaning it establishes
phone call conversations with remote sites upon transmitting to them. It accepts calls
when another site transmits an MDLC frame to it. Most of the time the modem is idle,
meaning it is in command mode. It only moves into data mode, when it needs to transmit
or is called from another site. After a predetermined idle time, the modem disconnects the
call. With MDLC over IP, the modem is ALWAYS in a "call". The "call" is actually PPP
mode. This enables it to receive MDLC over IP frames from remote sites, as well as
sending them. This "call" does not consume any air resources since it begins with the
RTU and ends in the modem itself.
To make it more reliable when using wireless modems in dial mode, the modem can be
monitored periodically to check if it is registered in the wireless network. This is done
periodically every few seconds.
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