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GPS Control Plane settings.. Possible GPS fix

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mpencexda
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Default GPS Control Plane settings.. Possible GPS fix

Hello,
I was wondering if anyone was familiar with the control plane option in SUPL settings.

The reason I ask is that I was playing around in the secret code area of SG Tools and noticed an area marked GPS
SGS Tools -> Secret Codes -> ServiceMode, Debug, Netz, Audio, Common -> Common -> GPS -> Display and Change CP Status.

I enabled the Control Plane and then set SUPL settings in lbstest to supl.google.com etc and change SUPL Mode to Control Plane. My gps has been crazy awesome since then. Also change application settings Accuracy to 25.. I do have the jupiter file gps fix installed but GPS would still loose me until I made these changes. I was hoping someone could explain Control Plane and or someone would test these settings for themselves and let me know how it works. I am running Axura Beta 5 with Setiron Kernel 1.4.2
 
MikeyMike01
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None of those settings "fix" GPS.
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mpencexda
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Thanks for the reply. Are you aware of what the control plane setting is for?
 
norcal einstein
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Not that I'm actually interested in this "fix", but is your "crazy awesome" GPS just giving you faster initial position locks?

Getting a position lock is one thing, but having the GPS actually be able to track your movement and be accurate is different...which many overlook when they say their GPS works. If you were to use to Captivate in the car to navigate with, would it be accurate? If you can say yes to that, you could consider your GPS working then.
 
mpencexda
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Quote:
Originally Posted by norcal einstein View Post
Not that I'm actually interested in this "fix", but is your "crazy awesome" GPS just giving you faster initial position locks?

Getting a position lock is one thing, but having the GPS actually be able to track your movement and be accurate is different...which many overlook when they say their GPS works. If you were to use to Captivate in the car to navigate with, would it be accurate? If you can say yes to that, you could consider your GPS working then.
I am getting faster locks.. more sattelites.. I also tested while driving and it stayed good the entire time.. I am going to test again on my hour drive home tonight..


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mpencexda
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Also my main interest is in finding out more information on what this setting does as well. It is my opinion that this has helped and I wanted more imformation and also to see if it helps qnyone else..

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drancid
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I dunno why but set as control plane gives me more sats and faster locks even better tracking.
This is the first thing i do every time after flashing a new rom to my cappy.
ms base mode, google supl sever with control plane mode and secure socket off.


Sent from ATT Captivate operated by Perception build 5
 
mpencexda
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Originally Posted by drancid View Post
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I dunno why but set as control plane gives me more sats and faster locks even better tracking.
This is the first thing i do every time after flashing a new rom to my cappy.
ms base mode, google supl sever with control plane mode and secure socket off.


Sent from ATT Captivate operated by Perception build 5
Have you checked to see if the control plane is enabled via sgstools?

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drancid
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Originally Posted by mpencexda View Post
Have you checked to see if the control plane is enabled via sgstools?

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nope but i'll check it now..

Sent from ATT Captivate operated by Perception build 1
 
Da_G
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Control Plane is an alternative method of accessing the AGPS server from User Plane (SUPL). Control Plane goes over the cellular providers Control Plane (fancy that!) whereas SUPL goes out over the GPRS network (HSPA, 3G, etc.)

For Control Plane to work, the cellular provider has to have in place specific technology intended for use with AGPS. All older AGPS solutions prior to the deployment of SUPL use Control Plane. Basically it's "the old way"

Note that you can obtain the exact same AGPS data through a SUPL connection to the same set of servers AT&T maintains. This is the default setting for "Server FQDN Type" - AUTO Config.

Basically, setting it to AGPS Mode - Control Plane (regardless of other server settings) is the same as setting AGPS Mode - SUPL, SUPL Secure Socket - ON, Server - h-slp.mnc410.mcc310.pub.3gppnetwork.org, Server Port - 7275. AND is also the same as using "Server FQDN Type" - AUTO Config, providing your cellular provider is AT&T (MNC 410 MCC 310).

Note that the specifications for AUTO Config will read the MCC/MNC of your network provider (in my example above, AT&T) and change the mncXXX.mccYYY part to match your providers MNC/MCC. Per the 3gpp SUPL spec, when in a home network, the URL to access for SUPL services is h-slp.mncXXX.mccYYY.pub.3gppnetwork.org, which breaks down to:

h-slp - Home SUPL Location Platform
mncXXX - MNC of the current network the phone is parked on
mccYYY - MCC of the current network the phone is parked on
pub.3gppnetwork.org - A (purposefully) un-registered domain name free for use by cellular providers.

When you are roaming, the URL changes to:
v-slp.mncXXX.mccYYY.pub.3gppnetwork.org
where v-slp instead means Visiting SUPL Location Platform.

So, to sum that up, if your cellular provider is following 3gpp SUPL recommendations properly, when you attempt a SUPL connection to h-slp.mncXXX.mccYYY.pub.3gppnetwork.org, your cellular provider should connect you to THEIR provided SUPL server. In the case of AT&T this is fully functional. Note that this will NOT work on Wi-Fi, the DNS will not resolve (since you aren't connected to a cellular network, the ISP you're on will not maintain a SUPL server for you, unless they are just THAT nice)

Note that if you use a program like MarketAccess to change your MNC/MCC to allow access to other markets, the SUPL address will also change (to reflect the altered MNC/MCC) and thus be broken in automatic mode.

Anywho, all of this only affects the initial lock time, when set to MS-Based. (Defaults on the stock ROM to standalone, which doesn't use AGPS at all, and sane people will use MS-Based)

Tracking once you have a lock should NOT be affected by any of these changes.

In case you're wondering where I got my information, it's not my first go-round to this particular party. I did all the legwork for this a bit over a year ago, and put up a compendium post about it in March 2009: http://forum.xda-developers.com/showthread.php?t=489887 All the info I reference from the SUPL specifications is obtained by spending hours reading the actual, incredibly boring whitepapers.

I haven't had time to properly devote to the GPS problem for captivate like I have for previous WM devices (I just got the cappy), but i'm guessing there's some errors in either the satellite correlation done in the baseband, or in the driver's interpretation of the output in the kernel code. It might also be the case that the phone is relying on a clock generator that isn't putting out the exact cycles they have it programmed for, thus introducing clock drift into the correlation algorithm. The clock has to be precise and synced up to the GPS clocks in order to properly trilaterate location. This might explain the drift over time and then snapping back to a real location once the clocks are properly synced again. (GPS satellites send the complete information required to sync a clock accurately every 12.5 minutes.)

Do note that the clock i'm referring to is the internal GPS reference clock, which is not related in any way to the time set on the device. Internally, the device does keep track of the offset between GPS time and Device Time, but Device Time is not used in the GPS calculations (a different internal clock is used, and synced to the satellites themselves with each transmission) - Previously it has been suggested that ensuring the phones clock is as accurate as possible would make a difference, but that is not the case (due to it not being the same clock)

Either way, any changes to gps.conf or secgps.conf aren't gonna cut the mustard with this particular issue. Initial fix time and number of initial sats, sure. But once the GPS is fired up and running, and has time to pick up a constellation update from the satellites, you're in the same boat as anyone else.

BTW. You can read the adb logcat output to easily see if your phone is utilizing AGPS. You will get an initial fix with an accuracy of appx. 1500m and the log will show that it is not a GPS fix but instead a network provided location. It will then show this location being injected into the GPS driver (AGPS)
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