The challenges of GPS in telematics

What's more, the GPS has made inroads into many recreational applications, including devices for everything from mountain bikes to digital cameras and mobile phones. Certainly the most common commercial application is telematics, and the market is growing fast. Ten years ago truck dispatching was the main application, and SMS was the preferred means of communication. Today more data can be sent far faster and at much lower cost via GPRS, and the number of applications has clearly increased.

More and more systems providers are offering solutions that do anything from simply locating stolen vehicles to supporting insurance applications and providing sophisticated diagnostic data. It would appear that the GPS has advanced to the point where it can readily be used everywhere. However, the devil is in the details, and some remaining challenges merit consideration. This article discusses those challenges arising in telematics applications.

The term telematics is generally taken to mean the linking of information and telecommunication. In vehicles, this technology is used in combination with the GPS " that is, the system providing information on location, speed, direction, and time. The added requirements determine how complex a box will be. Is it a matter of reading outputs or setting inputs? Is it necessary to access vehicle information (frequently via CANbus)? Are there interfaces to other sensors? Is there a need to display information? Does it require driver interaction? Telematics applications are also making branching out into other fields, for example, personal and asset tracking applications that trace and find people and goods. All these systems have two characteristics in common: They come with a GSM/GPRS unit (and often also CDMA, rarely a satellite communication unit, and sometimes both) and are GPS-enabled.

Once a manufacturer of such telematics boxes has made the buy-or-build decision, he has to determine whether to use a GPS chipset or a module for his proprietary design. It takes quite a few unit numbers " 250,000 is the typical figure " for a chipset to pay off. Using a module, in turn, entails investing considerable effort.

After all, it takes special components to provide optimum support for the chipset - first and foremost, a precision temperature-compensated crystal oscillator (TCXO). And it requires an LNA (low noise amplifier), a SAW filter (a band-pass filter with a narrow bandwidth) and an exceedingly clean voltage supply. The attendant clock quartz is a somewhat simpler matter.

All these components must be precision-tuned to match the chipset and connected using a well-designed PCB track. Of course, chipset manufacturers devote most of their design support to applications with high unit numbers. This allows a module manufacturer to get the best performance from the chipset and enable fastest integration into a telematics box. In the simplest-case scenario, the effort is limited to providing power, a serial interface, and of course a clean antenna connection.

And there are other obvious advantages to using a module: While the manufacturer has to buy just one component when opting for a module, a proprietary design requires contacting, negotiating, and nurturing a relationship with a specialized manufacturer or distributor. Furthermore, using a module shortens the design cycle for the overall product so it can go into production that much sooner.

Vincotech A1035-H GPS antenna module built around the SiRF GSC3 chip set with a sensitivity of -159dBm and power consumption down to 86mW.