Iridium NAL Research Corporation 9602-NAL, User Manual

Page: 34 / 40

9602-N User Guide Version A
Document Number: 451-92695-001A 34 of 40
The modem can then be used to call another computer, a remote LAN, or an ISP, as shown in
Figure 14 . The handshaking and protocols are established between the modems independent
of the landline.
Figure 14: PSTN Dial-up Connectivity
The Iridium dial-up data service, as shown in Figure 15 , functions in much the same way as the
PSTN dial-up connectivity. From the perspective of a computer, the Iridium modem is just
another external modem. The only difference is that the dialed telephone number must
conform to the international dialing pattern used by Iridium. When a data call is placed, the
Iridium modem actually dials and initiates a connection with the Iridium gateway through the
Iridium satellite constellation. Because the Iridium modem is requesting to establish a data
connection, the switch at the gateway routes the call through another modem. The modem at
the Iridium gateway then dials into and connects to another modem at the other end. Figure 15
illustrates how an Iridium dial-up data service call is routed. The handshaking and protocols
established between the modems are independent of the Iridium network.
For those ISU-to-ISU dial-up calls where data transmission delay is critical, such as the
application of TCP/IP protocol, DAV should be considered in the design. This option eliminates
the Iridium gateway once authentication and registration is completed, allowing ISU-to-ISU
communication without the gateway in the loop.
4.4 VD
C
RS232
NAL
Rese
arc
h
Antenna
4.4 VD
C
RS232
NAL
Rese
arc
h
Antenna