How It Works |
| # Overview of a Globalstar Phone Call |
| # Making a Call via Satellite vs. Cellular |
| # Roaming |
| |
| Overview of a Globalstar Phone Call |
| |
| 1. A caller uses Globalstar mode to place a call via the satellite
to one or more Gateways |
| 2. The Gateway routes the call to the existing phone network, in
the case indicated below, a cellular Public Land Mobile Network (PLMN)
network |
| 3. The PLMN routes the call to the intended receiver. The call
is completed! |
| 4. The call duration, service used, and service area are reported
to the Service Provider for billing. |
| |
| Making a Call via Satellite vs. Cellular |
| |
| 1. A subscriber in Russia is calling her friend in San Francisco
on her Globalstar satellite phone. Her signal is handled by a passing
satellite. |
| 2 .The satellite relays the call to a Gateway in its footprint. |
| 3 .The Gateway converts the signal to work with the
local PSTN and passes on the call. Depending on the distance between
the callers, a Globalstar satellite call might pass through several
Gateways and PSTNs before locating the receiving phone. The PSTN uses
the call's routing information to connect to another Gateway that
knows where the receiving phone is located. |
| 4. The Gateway located closest to the receiving phone
converts the signal to Globalstar format and uplinks it to a satellite.
This Gateway knows that the receiving phone is in its contact area
because an earlier satellite relayed that phone's power-on registration
message to the Gateway. This information was stored in the Gateway's
Visitor Location Register (VLR). |
| 5. The call is relayed to the receiving phone and the call linkage
is complete! |
| |
| Roaming |
| |
| The Globalstar system supports phones that are ANSI-41-based
and GSM-based over the common Globalstar Air Interface (GAI). The
GAI allows an ANSI-41 user to roam to an area served by GSM or vice
versa. The Globalstar Gateway provides the ANSI-41 capability and
works with a GSM Mobile Switching Center (MSC) for GSM capability.
Each Gateway serving an area governed by GSM contains a GSM MSC. Although
each Gateway includes both ANSI-41 and GSM capability, each type of
phone only supports one of these standards. When a subscriber with
a Dual-Mode GSM phone roams to North America, his/her phone will operate
in Globalstar mode. When the Gateway receives the signal from the
satellite, it will be routed to the GSM MSC for processing. The phone
will continue to operate using GSM protocols. |
| |
| Similarly, if a subscriber with an ANSI-41 Tri-Mode
phone roams to Europe, the phone will operate in Globalstar mode using
ANSI-41 protocols. |
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