GPS vs A-GPS

[AsharSalman]

Hi all,
I am a little confused about the A-GPS. I have read the articles about its working and benefits over GPS but I have following questions (Here i am concerned with 5800 Xpress Music A-GPS);

1. Could A-GPS be used as standalone GPS receiver? I mean if you are out of network service range but you can get GPS satellite signals, would in such case A-GPS would work?.
2. Could we use A-GPS with WLAN? or it always requires GPRS/EDGE access point?
3. Would it work with any service provider(which has GPRS/EDGE)? or it requires additional support from service providers?

The thing which confused me is that when I compared the specification of N95 with 5800 Xpress Music, I found that both have A-GPS but only N95 has GPS. This confused me that A-GPS couldn't be used as standalone GPS (When you don't want to use network trafic). Please someone guide.
Thanks
Ashar

[petrib]

A-GPS requires a data connection to the A-GPS server. Without the data connection, you have to rely on the actual GPS receiver to pick up the location.

Also the 5800 has built-in GPS receiver + the A-GPS support in software (like the N95).

[AsharSalman]

Thanks but why the specifications show GPS under N95 and N96 and not in 5800 Xpress Music, N97, N86 8MP etc (They all have A-GPS)? There must be some difference... Can anybody explain please?

[mahbub_s60]

Hi all,
I am a little confused about the A-GPS. I have read the articles about its working and benefits over GPS but I have following questions (Here i am concerned with 5800 Xpress Music A-GPS);

1. Could A-GPS be used as standalone GPS receiver? I mean if you are out of network service range but you can get GPS satellite signals, would in such case A-GPS would work?.
2. Could we use A-GPS with WLAN? or it always requires GPRS/EDGE access point?
3. Would it work with any service provider(which has GPRS/EDGE)? or it requires additional support from service providers?

The thing which confused me is that when I compared the specification of N95 with 5800 Xpress Music, I found that both have A-GPS but only N95 has GPS. This confused me that A-GPS couldn't be used as standalone GPS (When you don't want to use network trafic). Please someone guide.
Thanks
Ashar

1. A-GPS is assisted GPS. Since integrated GPS does not know from where to start searching satellites. A-GPS gives some data to GPS module so that GPS module can use it as starting point. A-GPS data is taken from a server (depends on operator) over GPRS connection. So A-GPS data is very rough data (not precise as GPS) that will help to locate the satellites.

2. I think we can't access WLAN, user of the phone does not know from where the phone is receiving data. For Nokia default location is supl.nokia.com. Of course we can't access it via WLAN.

3. For Nokia devices it works always if there is GPRS connection. If operators want to override it then that services will be used.

There is an article in wiki that explains more

http://wiki.forum.nokia.com/index.ph...methods_in_S60

Hope this help you.

[AsharSalman]

@Mahbub thankyou.
But can anyone explain why i have both GPS and A-GPS in N95/N96. And only A-GPS in 5800 XM, N97, N85 8MP etc? If A-GPS can be used as GPS then why specification page doesn't show it?

[petrib]

You can't use A-GPS "as GPS". And the 5800XM, N97, N86 8MP, etc., all have a real GPS receiver, too. If marketing web sites or even Forum Nokia developer pages have errors or are misleading, it doesn't change the fact that the devices have all both an actual, real GPS receiver and in addition also A-GPS software support.

[AsharSalman]

@Petrib
Thanks, now I know that I am not the only one to think that forum nokia device comparison service (http://www.forum.nokia.com/Resources...mparison.xhtml) is misleading and have errors :P

[mikemoore]

Thanks, now I know that I am not the only one to think that forum nokia device comparison service (http://www.forum.nokia.com/Resources...mparison.xhtml) is misleading and have errors :P

I'm not sure this is the right way to look at it. A-GPS is GPS with some additional features that Assist in obtaining a location fix more quickly.

A-GPS is GPS plus extra functionality. The fact that the N95 allows you to switch off the extra functionality is interesting but should not be confusing. The information sources you have do not contain an "error" and are certainly not "misleading".

A-GPS typically does not use the data network (i.e. it's not a chargeable service) - there are some implementations that do, but these will ask first if you want to connect and can easily be configured to use WiFi if you want.

Mostly, the functionality lives in the cell tower and the A- of A-GPS gets whatever it needs as a part of the cell phones normal "inactive" connection to the tower. If the A- is not available from the tower then you just have GPS.

- Mike
NAVTEQ Network for Developers
The community for developing innovative location-based applications
http://NN4D.com

[AsharSalman]

I'm not sure this is the right way to look at it. A-GPS is GPS with some additional features that Assist in obtaining a location fix more quickly.

A-GPS is GPS plus extra functionality. The fact that the N95 allows you to switch off the extra functionality is interesting but should not be confusing. The information sources you have do not contain an "error" and are certainly not "misleading".

A-GPS typically does not use the data network (i.e. it's not a chargeable service) - there are some implementations that do, but these will ask first if you want to connect and can easily be configured to use WiFi if you want.

Mostly, the functionality lives in the cell tower and the A- of A-GPS gets whatever it needs as a part of the cell phones normal "inactive" connection to the tower. If the A- is not available from the tower then you just have GPS.

- Mike
NAVTEQ Network for Developers
The community for developing innovative location-based applications
http://NN4D.com

Well, I am afraid you have also been misled.
You said N95 allows to switch off A-GPS but so does 5800 XM. Then what is the difference between GPS of N95 and 5800XM? You can't tell by simply using it (May be they have performance differences). Both provide similar positioning methods and you can switch ON/OFF any one. So where is the difference?
A-GPS is chargeable service, unless your operator implemented its own positioning server and doesn't want to charge for it. Otherwise whenever you send data to supl.nokia.com via GPRS/EDGE you are charged for it. I just checked it, my A-GPS of N95 used 50KB. May be you have different scenario, like your operator is generous or you are using WLAN as an access point to supl.nokia.com.
Like I said before, I am not sure about WLAN, but I read somewhere that you can't use A-GPS via WLAN.
And you are right about it "If the A- is not available from the tower then you just have GPS."

Please correct me if I am wrong or misled, I am still investigating this.
Thanks for your time.

[mikemoore]

You said N95 allows to switch off A-GPS but so does 5800 XM. Then what is the difference between GPS of N95 and 5800XM? You can't tell by simply using it (May be they have performance differences).

If you turn off A-GPS on any device, then you have simply GPS. I'm not sure why you think there is a such a big difference between these two devices. I'm not sure why you think anyone is being "misled"... you are simply misunderstanding the terminology.

A-GPS is chargeable service, unless your operator implemented its own positioning server and doesn't want to charge for it.

This statement is correct.

whenever you send data to supl.nokia.com via GPRS/EDGE you are charged for it.

This statement is also correct.

These two statements are not mutually exclusive.

my A-GPS of N95 used 50KB

As an aside, if you are concerned about a 50Kb data transaction then how you are going to create your locaton based application? Almost all location based applications (and certainly the interesting ones) require a data connection to a server and will be transferring far more than 50Kb in any given session.

Like I said before, I am not sure about WLAN, but I read somewhere that you can't use A-GPS via WLAN.

I checked on a couple of phones (N95 and E71) and it seems that the access point does indeed have to be GPRS/EDGE based.

And you are right about it "If the A- is not available from the tower then you just have GPS."

But doesn't this statement solve your problem? My understanding is that you are concerned about paying for the data traffic when using A-GPS. If so, turn off A-GPS and just use GPS.

- Mike
NAVTEQ Network for Developers
The community for developing innovative location-based applications
http://NN4D.com

[petrib]

Regarding "A-GPS is chargeable service". Note that the A-GPS service per se is not chargeable (in other words Nokia will not invoice you for using the Nokia A-GPS service), but if you use network operator's packet data connection, the network operator will charge for that data traffic (unless you have an "all-you-can-eat" fixed data plan).

[AsharSalman]

@ mikemoore
I appreciate your response. I have got answers for almost all questions, but I have only one question left; what is the real difference between GPS of N95 and GPS of 5800XM? If there is no difference then why specification page has mentioned A-GPS in both mobiles but GPS only in N95? There must be some difference otherwise specification pages have errors.

[petrib]

There is no difference. Ignore what you read in specifications or marketing materials (or at least don't try to read too much into how they've been written).

Both the 5800 and the N95 have a built-in GPS receiver and both support also A-GPS.

I essentially already stated this in response #2 above in this very same thread.

[AsharSalman]

@Petrib
I already ignored that, I was just helping everyone to ignore that. Or may be Forum Nokia realize it and change specification page.
Thanks

[mikemoore]

There is no difference.

Definitely correct.

Again, the marketing material is not actually "wrong"... A-GPS *IS* GPS, with added functionality. The marketing material is right in both cases, it's just stated differently (at different times and by different people).

The closest analogy I can get is that a DVD player can play CDs. But you don't often hear marketing people explaining that a DVD player will also play CDs anymore, everyone already knows. However, a few years ago, this was an important message, it's just that it's stopped being said.

- Mike
NAVTEQ Network for Developers
The community for developing innovative location-based applications
http://NN4D.com