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Wireless Systems Design

Collaborators Get A Fix On E-GPS

For many OEMs in the wireless-network and mobile-device spaces, Enhanced Global Positioning Systems (E-GPS) are high on the wish list. E-GPS addresses the problem of providing quality timing assistance to GPS-enabled devices in asynchronous networks, such as GSM and W-CDMA. The lack of a common synchronization source means that devices can take longer to provide a location reading. E-GPS brings together two independent positioning methods to achieve both faster location fixes and lower power consumption.

In two separate collaborations, Cambridge Positioning Systems Ltd. (CPS) is working with other vendors to find ways around this difficult challenge. For example, CPS and Trimble ( plan to work together to demonstrate how E-GPS will improve in-building and urban-canyon operation. The companies' joint solution will combine device and server software intelligence to provide optimal accuracy, the best possible coverage, and minimum latency for GPS-enabled handsets and other mobile devices.

By deriving accurate timing for mobile stations using GSM and W-CDMA radios, CPS and Trimble hope to discover positive implications for the use of GPS in difficult environments like in-building and urban-canyon settings. Without an accurate knowledge of time, GPS sensitivity is constrained by acquisition time and computational resources. The companies' work combines CPS's Matrix location technology, which is comprised of Matrix client and server software,with Trimble's GPS hardware. It has the potential to produce a low-cost and capable positioning system for GSM and W-CDMA handsets.

In a second collaboration, CPS is working with SiGe Semiconductor ( to develop E-GPS capabilities for 2G and 3G cellular networks. The pair has demonstrated seamless coverage with fast location fixes by interfacing a GSM handset, which is equipped with SiGe's SE8901L GPS receiver IC, to a network powered by the CPS Matrix software (SEE FIGURE). In an E-GPS system, this technology combination enables both satellite- and network-based measurements to allow fast, all-area, all-segment positioning. Preliminary tests demonstrate consistent positioning within seconds as well as continuous tracking and high accuracy.

This partnership combines the technology strengths of CPS's Matrix software with SiGe's GPS and chip-set expertise. The pair is working to develop E-GPS products for GSM and 3G. When operating in obstructed environments, such as deep within buildings, an E-GPS-equipped handset can access the CPS Matrix system. It can thereby provide position information in locations where competing GPS systems might not work. The Matrix system also provides time synchronization, which allows the SiGe SE8901L GPS receiver IC to return a position faster and with greater accuracy than competing approaches.

TAGS: Mobile
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