Power-saving GPS for phones unveiled

By David Meyer on 29 July 2009, 10:34am

Cambridge Silicon Radio has unveiled a new GPS architecture that it says will let phones be aware of their location constantly, without draining their batteries.

The architecture, SiRFstarIV, was announced alongside the first product to use it, Cambridge Silicon Radio's GSD4t receiver for mobile phones and other portable devices.

Mobile phones increasingly have GPS built-in for navigation and other location-based services. However, current GPS architecture is a major contributor to battery drain – a situation the company is hoping to fix.

CSR's chief marketing officer, Kanwar Chadha, told CNET UK's sister site ZDNet UK that smart phones using current GPS platforms deliver a worse experience than dedicated personal navigation devices with the same technology. He attributed this lag in smart phones to three factors: battery consumption, the time it takes to get a fix on GPS satellites (as the GPS has to turn on and off to save power), and interference from other electronics inside the devices.

"GPS was not designed to be navigation-centric," Chadha said. "If you try to make location available all the time, you drain the battery very quickly. Other radios, the LCD display and the processor also interfere with the GPS signal."

This situation was a driver for the creation of SiRFstarIV, which is "not on all the time, and not off all the time", Chadha said.

The platform instead uses an 'aware' state, which "keeps the necessary information to do a very fast calculation from the satellite [and is] alive all the time but in a very low micropower mode", he explained. This approach means the device's GPS does not need to be continually turned on and off to conserve power -- hence the speed with which it can get a satellite fix.

Chadha said the SiRFstarIV platform uses between 50-500 microamps. That power consumption level is substantially lower than that found in existing GPS platforms, which burn up power in the milliamps.

The company also looked at the other drags on GPS performance in smartphones for the new architecture.

"The second thing we did is [to] put in a new technology which scans for all the noisy signals that interfere with GPS, and eliminates interferers before they can hit the GPS signal," Chadha said.

The GSD4t receiver is now available in sample quantities to manufacturers of mobile phones and other portable devices, with full-scale production scheduled for October. Chadha says the first handsets using SiRFstarIV should be in the shops in early 2010.