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 [TOPIC] A-GPS
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Fuzzerony

2 Posts

Posted - 07 févr. 2005 :  18:40:31  Show Profile  Reply with Quote
Hi,

I am looking for a GSM device or module that supports 3GPP A-GPS.

Is there anything currently available in the market?

Thx

Fuz

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gpspassion

94668 Posts

Posted - 08 févr. 2005 :  01:11:42  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Nothing at the consumer level, no, at least as far as I know, why ?

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Fuzzerony

2 Posts

Posted - 08 févr. 2005 :  16:54:13  Show Profile  Reply with Quote
Why? Because I'm looking for such devices/modules.
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gpspassion

94668 Posts

Posted - 13 févr. 2005 :  02:12:59  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Hum...ok !

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wayneh

United Kingdom
8 Posts

Posted - 09 mars 2005 :  18:43:15  Show Profile  Visit wayneh's Homepage  Reply with Quote
The 3G Operator 3 (available in UK, Italy, Austria, Sweden, Denmark, Hong Kong and Australia) has 3G/2G (ie WCDMA/GSM) handsets from Motorola and NEC which are A-GPS enabled (NEC 616 even includes a digital compass)
3 provides application which utilise A-GPS - these will run when the phone is in GSM mode IF the 3 country has enabled this

Wayne
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gpspassion

94668 Posts

Posted - 09 mars 2005 :  21:27:54  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Right and talking about A-GPS, I found an excellent explanation >>HERE<< ("Why AGPS ?" paragraph) that should downplay the "magic" that some marketing people are attributing to AGPS ;-)

What chipsets do the NEC and Motorola use ? Even without a full baseband/rf combo I doubt you can do real time navigation like you would with a standalone GPS, easier for LBS though of course.

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wayneh

United Kingdom
8 Posts

Posted - 09 mars 2005 :  21:47:15  Show Profile  Visit wayneh's Homepage  Reply with Quote
There's no magic - A-GPS simply lessens the TTFF (important if normal state of GPS if OFF as in a mobile phone) and allows fix to be made with weaker signals as no data needs to be demodulated from the signal - only the 'time-stamp' is required.

The Motorola A920/A925/A835 uses SiRF IIe/LP. The GPS chipset in the Motorola A1000, E1000 and NEC E616 has not been announced

All these devices support A-GPS via J2ME. The Motorola A920/A925/A100 also support Symbian A-GPS software.

Support real time navigation given appropriate software (eg see http://www.nhgps.com/) is not an issue

The only major issue is loading the software onto the devices as some 3 countries have locked J2ME access !!


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gpspassion

94668 Posts

Posted - 09 mars 2005 :  22:14:41  Show Profile  Visit gpspassion's Homepage  Reply with Quote
The "magic" comment was not directed to you but originated from an article I just read online in a "serious" French webzine (01net.com) that made AGPS look like magic, sorry for not clarifying in the first place. I found that the article I linked just gets down to business explaining what AGPS can do. I think CDMA networks give some extra help at the timing level.

The big plus obviously is not having to download the ephemeris data and "focusing" the available horsepower on decoding signals that are known to be available. Since some of the original aiding data (ephemeris) is IP based before getting fed to networks, I've been asking whether some "custom" AGPS couldn't be done by getting the data over GPRS with say a PDAPhone and feeding it to the receiver manually, no answer so far :-(

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wayneh

United Kingdom
8 Posts

Posted - 10 mars 2005 :  00:56:39  Show Profile  Visit wayneh's Homepage  Reply with Quote
Yes CDMA networks are synchronised (by GPS receivers) whereas GSM/WCDMA are not - therefore handsets can be given a better estimate of time than GSM/WCDMA handsets

Traditionally the assistance data is sent to the handset over the control plane in a mobile network (both CDMA and GSM/WCDMA)

There is work going on in the Open Mobile Alliance to standardise sending it over an IP connection (no changes required in the operators infrastructure!!). Standard is due out mid year so expect to see many WCDMA A-GPS phones using this around the end of the year. WCDMA because IP and voice can happen at the same time whereas with GSM its either voice or IP - not good for emergency location !

Note that SiRF has defined their own NMEA sentences to send basic assistance data to there chipsets

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gpspassion

94668 Posts

Posted - 10 mars 2005 :  01:40:07  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Thanks for the info. It seems all UMTS/3G networks would be WCDMA ?

So it seems that for SiRF receivers it would be pretty easy to send ephemeris data collected from the web especially since I think SiRF provide a turnkey "SiRFsoft" solution that includes aiding data sent over IP. Not sure they'd let end users connect directly though ;-)

As usual it's by experimenting that you can get a good grasp of a technology, but I'm wondering how much AGPS can bring in terms of getting a fix indoors, clearly getting the ephemeris data directly can be make or break, and knowing which satellites to focus on can't hurt, but it's not always going to be enough, right. I guess a simple experiment is to get a good fix with a SiRFstarIII GPS and then walk into a building and look at the signal level coming down and then the fix being lost. In this case you have a valid ephemeris (I think it helps to update it at least every 30 minutes) but the signal is just too low to track. While aiding can possibly help by focusing the work on known signals, I'm not sure it would do better than the "brute force" of SiRFstarIII. Done any experimenting yourself ?


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wayneh

United Kingdom
8 Posts

Posted - 10 mars 2005 :  11:34:01  Show Profile  Visit wayneh's Homepage  Reply with Quote
Yes - the 3G upgrade path for GSM operators is WCDMA. For CDMA operators its CDMA-1x (loose 3G definition is any mobile technology providing minimum 64K data pipe)

Whatever GPS chip is in use, "assisting" it by providing as much information as possible (time, approximate location, almanac, ephemeris, clock corrections etc) via a different path (eg mobile phone network) WILL improve both TTFF AND the use of weaker signals than would otherwise be possible

See the presentation - "IP Based A-GPS - The Technical Benefits" on my site at http://www.m-location.com/presentations/

NB Siemens have just announced their SXG75 WCDMA/triband GSM phone with both autonomous and Assisted GPS + a whole lot of other nice features




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gpspassion

94668 Posts

Posted - 10 mars 2005 :  12:08:00  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Yes that phone looks nice, haven't had time to investigate the technical details (chipset for instance) yet.

Right, regardless of the chipset, aiding will always help for TTFF (not for tracking although of course you can only track if you've been through the TTFF part!), the question is how far and how much with a "brute force" chipset like SiRFstarIII, see my example above on my thoughts/questions about this. Obviously, you still need to receive a minimal amount of GPS signal if you want to be able to correlate it and this is more or less being "ignored" in a lot of "PR" that claims that AGPS can get a fix inside a tunnel, inside a multi-level parking garage, etc...back to the "magic" comment. At 3GSM, SiRF had a great demo device that could let you vary signal strengh, add aiding, etc... not enough time to use it fully though.

In the "benefits" article you linked, the TTFF chart shows that with Ephemeris and location (from CELL ID triangulation ?) you can get a fix with ultra low signal, any idea how low that is ? I assume the "Time" for the blue line corresponds to CDMA corrections ?

Very interesting article by the way and it does reinforce the sense I'm getting that A-GPS is above all a huge "plus" for integration of GPS on mobiles by making the "Push to Fix" mode required for battery life preservation, practical. Unlike what PR would have us believe though, I don't see it changing much to GPS as we know it for real time navigation (power use, lost fixes in tunnels, etc...), except in the situations where it was the only way to get a fix in the first place.

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mochuelo

France
3 Posts

Posted - 16 avr. 2005 :  20:03:33  Show Profile  Reply with Quote
can anybody please points out the main differences between USER PLANE and CONTROL PLANE? and I mean from a technical point of view. By searching on the internet, it seems that the Control Plane is not ready yet and that the OMA is still working on the standars RRLP/RRC to make it possible. Basically, I see many propietary solutions.
Do you know if there is any current implementation of Control Plane with a 3G operator worldwide?.
Thanks everybody.
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gpspassion

94668 Posts

Posted - 27 avr. 2005 :  16:21:59  Show Profile  Visit gpspassion's Homepage  Reply with Quote
An interesting AGPS development on the HP hw6500! While the "HP Quick Connect" aiding is not real time with new data (Long Term Orbit) being updated every 3 days apparently, it does mark the first form of AGPS over the internet.

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wayneh

United Kingdom
8 Posts

Posted - 27 avr. 2005 :  16:47:31  Show Profile  Visit wayneh's Homepage  Reply with Quote
quote:
Originally posted by mochuelo

can anybody please points out the main differences between USER PLANE and CONTROL PLANE?
Have a look at my presentation "IP Based A-GPS - the technical benefits" here (IP based = User Plane)

Basically Control Plane is through all the components of the Mobile Operators infrastructure (costly !) whereas User Plane simply utilises the EXISTING IP connection between the mobile and a box back in the IT dept of the Operator.

Hence all the 3G UMTS operators are waiting on OMA SUPL (Secure User Plane Location) to be defined.

Vodafone UK has announced Control Plane A-GPS for the UK - note that with 2G you cannot have voice + data (ie User Plane) simultaneously - so you need to do Control Plane A-GPS to support US911 or EU112 location in 2G GSM

Note that SUPL can be used fro other things - eg returning a Cell-ID based location to a mobile in response to to mobile Java application call to the SUPL interface.

Wayne

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mochuelo

France
3 Posts

Posted - 28 avr. 2005 :  00:13:56  Show Profile  Reply with Quote
Thanks a million wayneh, as your presentation is really good.
Regarding only updating the assistance data every 3 days on the new HP hw6500, I think that does not have such a huge impact and it definitely reduces your bill if you pay per KBps TXed in GPRS, as the ephemeris data has a lifespan of 3 days and almanac data of 6 months. So, unless ionospheric data changes a lot or your approximation location is totally different, I do not see a great problem...
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