User's Manual

DRAFT TrimTrac Locator Technical Manual 10
These tables are the Public Land Mobile Network (PLMN) tables and each GSM
network has its own unique PLMN number. This number is the Mobile Country
Code (MCC) and the Mobile Network Code (MNC), which are also the first
numbers of the subscriber’s IMSI. (The IMSI is the MCC, plus the MNC, plus the
MSIN.) The PLMN table finds either the subscriber’s home network or a network
that will allow service, and registers to the network consistent with the handset.
The responding network’s Mobile Switching Center (MSC) passes this request for
service to the Visitor Location Register (VLR). If the VLR has information about
this IMSI, then it passes the request to the authentication center. If the VLR
cannot find any information on this IMSI, it must pass the request to the HLR and
get approval before passing on the request.
Once the VLR has approval to grant the request for service, it knows the user
identity, what features are authorized, and the authentication codes. The VLR then
passes the request back to the MSC for routing to destination address specified by
the TrimTrac locator. If the destination address is a land-based number, the MSC
passes the call to the Public Switched Telephone Network (PSTN) for connection.
If the destination address is another mobile number, the MSC repeats the process
described above to locate the number being dialed.
Global Positioning System
The Global Positioning System (GPS) is a satellite-based navigation system operated and
maintained by the U.S. Department of Defense. GPS consists of a constellation of 24
satellites providing worldwide, 24-hour, three-dimensional (3D) coverage. Although
originally conceived for military needs, GPS has a broad array of civilian applications
including timing, surveying, fleet management, marine, land, aviation, and vehicle
navigation. GPS is the most accurate technology available for navigation. As a satellite-
based system, GPS is immune from the limitations of land-based systems, which have
limited coverage and whose accuracy varies with geographic location and, even under
ideal conditions, cannot compare with GPS. By computing the distance to GPS satellites
orbiting the earth, a GPS receiver can calculate an accurate position. This process is
called satellite ranging. GPS receivers can also provide precise time, speed, and course
measurements that are important for vehicle mobile positioning and communications
applications.
GPS Receiver
The TrimTrac locator includes an advanced GPS receiver, which provides the
position, course, speed and time information required for mobile asset
management applications. A brief overview of the GPS receiver’s architecture
and operation is provided below. The TrimTrac locator’s GPS receiver features a