Page 204 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes

Notes A service connector is available for maintenance purposes.

ProTrak Service

ProTrak is a service for the localization and tracking of stolen vehicles. Upon activation by the Data
Center or, optionally, by an alarm system in the car, the position of the car is reported to a central
desk of the customer. Here the information is processed and the appropriate action can be taken.

For the ProTrak application, a radio modem is installed in a place inside the car that is not easily
accessible. Because of the small dimensions of the unit, it can be hidden easily in various spots in
the car. A GPS receiver antenna and a ProTrak mobile antenna are also installed unobtrusively.
The unit has no external user controls, since its purpose is to be activated by the customer Call
Center or an alarm system only.
When the ProTrak unit is activated, the processor sends a unique identification plus the last
known position to the modem for transmission to the Call Center for action. As long as the
unit remains activated, regular position updates are transmitted to allow tracking of the stolen
vehicle.
The ProTrak service can be extended with an alarm or assistance call activated by the car driver.
The data is then sent to the Call Center for appropriate action. Using a set of push buttons the
user may specify one out of a number of request types such as technical assistance, medical
assistance or police assistance. The radio modem for this so-called ProTrak Plus service is slightly
different from the ProTrak unit; it is controlled and activated in a different way. Furthermore, it
is not necessary to hide the Pro Trak Plus equipment.
12.2.5 Principles of Meteor Burst Communication

Meteor burst refers to a unique means of long-distance communication via reflections by ionized
gas trails in the upper atmosphere. These gas trails are generated by the burn up of small meteors
impacting on the Earth’s atmosphere. The typical meteor trail is only available for a few hundred
milliseconds.
As communication is only possible in very short intervals, the term ‘burst’ is introduced. Due
to the nature of the phenomenon used, waiting times are introduced. The delay between the
appearance of two consecutive trails ranges from seconds to minutes, depending on the time of
year, the time of day and design factors of the system.
The network supports a variety of data communication services for road transport and telemetry
applications. The FleetTrak service has been developed for fleet management systems and
provides two-way data communication plus vehicle tracking for trucks. A second service, offered
under the name ProTrak, has been developed for private cars and provides after-theft tracking
and alarm messaging as shown in figure 12.6.
In remote areas the meteor burst communication system can be used to transfer data from a
measurement site to the central office. Examples of these telemetric applications are snow height
and tide gauge measurements.
Most meteor scatter applications operate between 30 and 50 MHz. At frequencies below 30 MHz
absorption and noise, both galactic and artificial, increase drastically. Furthermore, the antenna
size and cost increase at lower frequencies. The data communication capacity will decrease
when frequencies above 50 MHz are used, as the average burst length decreases with increasing
frequency. Additionally, radio and television allocations preclude meteor burst operation above
50 MHz.

198 LOVELY PROFESSIONAL UNIVERSITY