“eGPS” and “software GPS” are technology inherited from the acquisition of GPS specialists NordNav Technologies AB and Cambridge Positioning Systems in January 2007.
A-GPS (Assisted GPS) techniques are a popular method for reducing GPS's limitations when implemented on handsets. A network-located server provides Ephemeris and Almanac data to shorten time to fix. However, A-GPS cannot help a handset to sense position when GPS signals are unavailable.
eGPS extends the aiding concept by supplementing Ephemeris and Almanac information with a database of GSM/WCDMA base station locations and a timing model of the network, in order to generate fine time and frequency aiding to speed GPS fixes. It also provides positional information based on cellular network information alone, providing a fallback position accuracy of some 100m.
Satellite time information is maintained accurately and autonomously within the handset, which has the practical benefit of speeding time to fix in poor GPS environments. This accelerates fix times by as much as three times compared with A-GPS claims CSR. Satellite time calibration can even be maintained autonomously by the handset alone for hours following a fix - allowing systems to operate with or without a network-located server - ensuring that users can sense position when roaming.
The impact on power consumption is said to be small, as the cellular information is continuously derived via the handset's cellular modem, allowing the GPS subsystem to be powered up only when an accurate position fix is required. According to CSR, “a typical eGPS push-to-fix should be available in less than 4 seconds, accurate to within 10m, and require the equivalent power of less than 1 second of handset talk time”.
CSR CEO bullish, but will the operators follow?
CSR’s CEO, Joep van Beurden commented, “Our working silicon and demonstrations at Mobile World Congress are all significant steps on CSR’s roadmap towards adding high performance, yet power-efficient eGPS to cellular phones at an additional cost of less than $1.” van Beurden continued, “Our patented eGPS technologies are ready to change the market for location technologies in mobile handsets.”
However, the drawback of eGPS technology is that it requires wireless operators to deploy eGPS servers. Many wireless operators still have to deploy A-GPS and make a real place to location in their service offering, so it might take a bit of time before they are even thinking about eGPS.