CSR plc debuted the SiRFstarV 5e, a new Global Navigation Satellite System (GNSS) chip in early June (press release). Directions Magazine asked CSR’s director of product line, Dave Huntingford, and director of mobile segment marketing, James Cheng, about the new chip’s features and the state of outdoor and indoor positioning.
Directions Magazine (DM): The SiRFstarV 5e supports GLONASS, GPS, QZSS and SBAS from ROM. GLONASS is the Russian GNSS and GPS is the U.S. GNSS. What are QZSS and SBAS? And, why are those terms unfamiliar?
Dave Huntingford and James Cheng (CSR): QZSS (Quasi-Zenith Satellite System) is an operational regional satellite navigation system that improves the availability and accuracy of GPS services by providing ranging and correction data for quite a wide region in Asia. Although it is primarily targeted at Japan, the QZSS orbits provide coverage down to Australia. The first satellite was launched in 2010 and it is planned to be a four-satellite constellation by 2018. Because it’s limited to Japan and Oceania/Australia, it hasn’t gotten the attention it deserves outside of those regions.
SBAS (Satellite-Based Augmentation System) is a system that supplements GNSS, with wide-area or regional augmentation via geostationary satellites that broadcast correction messages. Data from the satellites, such as long-term errors of satellite orbits, clock errors, Ionospheric delays and integrity are calculated at ground stations at precisely located positions and broadcast to satellites so that locations are much more exact. Many systems are available around the world, for example, WAAS in the U.S., EGNOS in Europe, MSAS and QZSS in Asia. SBAS is not a satellite system by itself, so it is less known than the main satellite system.
DM: What is the general strategy for “power saving modes”? Can you give examples of how the chip saves power?
CSR: SiRFstarV 5e saves overall system power by having the location engine built into the chip, letting the host system to go to sleep, since it is not needed for positioning. SiRFstarV 5e also has the following power saving modes to further reduce power consumption on the chip itself:
- SiRFAware maintains hot start capability with ultra low power
- Push-to-Fix can adaptively reduce power, depending on the environment and motion conditions (< 6 mW)
- TricklePower mode requires <10mW
- TricklePowerII adaptive modes to reduce continuous tracking power
DM: The new "InstantFix Extended Ephemeris” feature will help time to first fix. How does this work?
CSR: Ephemeris data is positioning information broadcast by a GPS satellite that details its exact position in the sky. Every 30 seconds or so, a typical satellite very precisely broadcasts its location and orbit data for the next 2 to 4 hours. SiRFInstantFix can be downloaded to the GNSS chip via an Internet connection beforehand, and it significantly improves the time to first fix (TTFF) for location-centric devices by autonomously forward predicting Ephemeris. SiRFInstantFix offers 14 and 31 days of EE data for GLONASS and GPS, respectively. The 5e also supports predicting Ephemeris orbit data locally for a few days, for products that are not connected or infrequently connected.
DM: The SiRFstarV 5e might find its way into wearable navigation solutions, such as glasses. What are the key features of a chip for that sort of use? Are they significantly different from those in a phone?
CSR: An important issue for wearable navigation solutions is that they need to have low power consumption while maintaining good performance. A smartphone generally has a rather powerful application processor and large battery, whereas most wearable gadgets cannot afford them. SiRFstarV 5e with its built-in location engine and advanced power saving modes is the key to saving overall system power.
DM: With the big push for indoor navigation, is an “indoor/outdoor” chip likely in the future? What are the current challenges or barriers to such an engine?
CSR: The challenge of the indoor solution is the fusion of indoor and outdoor solutions. In many cases, indoor location is affected by the weak GNSS signal picked up indoors that points to a location outside due to poor satellite visibility. The key for successful indoor location is the ability to fuse satellite, MEMS [microelectromechanical systems - technology of very small devices] sensor and other available wireless signals into a good indoor position.