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GPS Performance Compared
Posté le 13 septembre 2009 à 19:02:21 par gpspassion.

8. February 2008 - 4 PDAPhones - SiRF keeps the Edge

Samsung i780, HTC TyTn II, Eten X600, Nokia N95

Samsung i780, HTC TyTn II, Eten X600, Nokia N95

GPS is everywhere these days and particularly in PDAPhones or Smartphones, no mean feat since there are significant constraints to cram in all the "connected technologies" in these ever more compact devices, GSM, WiFi, Bluetooth, GPS, a bright screen. Needless to say RF interference runs rampant and a high sensitivity GPS chipset is a requirement. Until last year there was only one player, SiRF, with the powerful SiRFstarIII chipset released in early 2005. The other original high sensitivity chipsets by uBlox, NemeriX, MTK, SkyTraq, have not cracked the connected device world yet, but Qualcomm's and TI's have and will be used in this comparison, thanks to the GSM/WiFi integration for the former and to Nokia's decision for the latter.

While some will argue that a chipset must be judged on a test bench to remove problems with the design of the device, at the end of the day, what matters is the user experience and real life side by side comparisons of actual devices are the best way to get an idea of what it is. The line-up for this article is as follows :
- Eten X600 - SiRFstar3lt
- HTC TyTn II - Qualcomm MSM7200
- Nokia N95 8Gb - TI v3
- Samsung i780 - Qualcomm MSM6200

To overcome the reduced signal fed to the chips by the diminutive GPS antennas, all these PDAPhones have some form of A-GPS, "Ephemeris AGPS" for the X600 with SiRFInstantFixI and the HTC TyTn II with gpsOneXtra, and MS-Based for the Nokia N95 (supl Nokia) and the Samsung i780 (supl Orange). As a result, warm TTFF is obtained in less than ten seconds. For the purposes of this comparison, all the systems were left to "settle" for 10 minutes in the open to remove the impact of these various forms of AGPS

Driving around the high rise buildings of the budding business complex of Noisy le Grand is a good way to gauge the accuracy of the various systems :

A. Overview

B. Zoom #1

B. Zoom #2

B. Zoom #3

In addition to the qualitative approach of analyzing the raw tracks, the quantitative analysis of the signal levels obtained from the NMEA can be useful to explain some observations.

No surprise here, the ultra-slim form factor of the i780 likely forced Samsung to use a thin PIFA antenna and as a result the Qualcomm chipset has the lowest signal level to work with. This certainly explains the degraded accuracy of the i780 compared to the HTC TyTn II, also Qualcomm based. Or it could be that the MSM7200 chipset offers improved performance compared to the MSM6200 of the Samsung.

Apart from the TI equipped N95 that doesn't recover from the multipath rich passage under and between high rise buildings, the overall performance is very good in light of the constraints of building GPS into the devices. The Qualcomm based Samsung i780 and HTC TyTn II offer good results as long as the conditions are not extreme with a slight advantage for the TyTn II, but the SiRFstar3lt based Eten X600 remains the best performer, being able to handle all types of environments, including pedestrian use as seen in this comparison. Whether this is due to SiRF's expertise in navigation software for high sensitivity chipsets honed in the field since early 2005 or to the better design of the Eten X600 is hard to say, probably a bit of both. It will be interesting to see if the new SiRFprima platform with what looks like a SiRFstarIV chipset is included on upcoming PDAPhones.

If you have questions, comments or suggestions, you can use this thread of the forums

<< 7. July 2007 - Pedestrian Mode Comparison - SiRF vs MTK 9. September 2009 - GPS Chipsets : SiRFAtlas IV Impresses >>

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