Constellations disabled - Android power saving?

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Peter Mousley

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Oct 21, 2021, 6:59:46 PM10/21/21
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I noticed my phone sometimes disabling constellations and was able to determine it was happening as I moved from clear sky view (strong signal) to obscurred view (weak signal).  So I repeated this check using two other phones.

The phones and results:
  • OnePlus 5 (LineageOS 18, Android 11)
    • weak signal: GPS+GLO+GAL+BDS+QZS all enabled*
    • strong signal: GPS+GLO+QZS * enabled, GAL+BDS disabled
    • * note: only GPS is ever reported as being used in a solution, even when other constellations/satellites have strong signals, almanac and ephemeris data
  • OnePlus 6 (OxygenOS, Android 11)
    • weak signal: GPS+GLO+GAL+BDS+QZS all enabled
    • strong signal: GPS+GLO+GAL+QZS enabled, BDS disabled
  • Google Pixel 4a 5g (stock Google Android 11)
    • weak signal: GPS+GLO+GAL+BDS+QZS all enabled
    • strong signal: GPS+GLO+GAL+QZS enabled, BDS disabled
Results we uploaded to the database 2021-10-07, starting 11 pm.  There are two results for each phone:
  1. the first result for each phone is in clear sky/stong signal conditions
  2. the second result is in obscurred sky/weak signal conditions
The tests were repeatable: step under an obstruction and all constellations would be enabled, step into clear sky view and some constellations would be disabled after a few seconds.  Note that the blacklist file is empty.  Location is Australia.

Is this behaviour well known?  Is it power saving?  The OS decides it has enough satellites for a reasonable fix so disables some constellations to save power?

If this is common it would help explain some of the differing results in the database - similar results can be seen in the database for all three of these phones.  Perhaps many of the difering results are more about constellations being temporarily disabled rather than the country of use?

As for the OnePlus 5 only ever using GPS for a solution...???

Sean Barbeau

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Oct 28, 2021, 1:08:31 PM10/28/21
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Peter,
Yes, apparently some devices do indeed disable some GNSS and/or frequencies under certain conditions. You can override this behavior manually via enabling the "Force full GNSS measurements" setting in the Android system Developer Options on Android 9 and higher. If you're running Android 12 or higher, GPSTest now forces this behavior by default using a new Android system API that was added in Android 12.

Here's the Android 12 system API that describe the behavior:

>If true, GNSS chipset switches off duty cycling. In such a mode, no clock discontinuities are expected, and when supported, carrier phase should be continuous in good signal conditions. All non-blocklisted, healthy constellations, satellites and frequency bands that the chipset supports must be reported in this mode. The GNSS chipset will consume more power in full tracking mode than in duty cycling mode. If false, GNSS chipset optimizes power via duty cycling, constellations and frequency limits, etc.
>
>Full GNSS tracking mode affects GnssMeasurement and other GNSS functionalities including GNSS location.
>
>Full tracking requests always override non-full tracking requests. If any full tracking request occurs, all listeners on the device will receive full tracking GNSS measurements.

Meaning that if you don't enable this setting, duty-cycling is used and clock  discontinuities occur, healthy constellations and frequency bands may not be used, etc.

You can read more about this setting and it's effects in my post here:

>Perhaps many of the difering results are more about constellations being temporarily disabled rather than the country of use?

It's possible, although the country of use (and in many cases which 

> As for the OnePlus 5 only ever using GPS for a solution...???

I'd still report any "abnormal" looking behavior to OEMs - there have been a number of bugs in devices where the "U" flag in the data from the Android APIs for satellites used in the fix isn't being set correctly. In those cases, the underlying location engine is indeed using more satellites than the "U" flag in the data indicates. But only the OEM could answer this for sure.

Also, are the OnePlus 5 and 6 here running official OS builds from the OEM? If not that can cause compatibility issues between the OS and underlying GNSS drivers and data shown in GPSTest may be unreliable.

Sean

Sean Barbeau

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Oct 28, 2021, 1:10:20 PM10/28/21
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Whoops, didn't finish this sentence:

> It's possible, although the country of use (and in many cases which exact chipset is used) definitely makes a difference

lodrog...@gmail.com

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Oct 29, 2021, 3:55:16 AM10/29/21
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On Thursday, October 28, 2021 at 8:08:31 PM UTC+3 sjba...@gmail.com wrote:
Peter,
Yes, apparently some devices do indeed disable some GNSS and/or frequencies under certain conditions. You can override this behavior manually via enabling the "Force full GNSS measurements" setting in the Android system Developer Options on Android 9 and higher. If you're running Android 12 or higher, GPSTest now forces this behavior by default using a new Android system API that was added in Android 12.

this is not working at least for qualcomm SoC's

Sean Barbeau

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Oct 29, 2021, 12:21:34 PM10/29/21
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>this is not working at least for qualcomm SoC's

I think it depends on what you mean by "not working." It will always disable duty cycling, and I've seen this on a few Snapdragon devices, including the Pixel 5.

It will not always give you all GNSS constellations and carrier frequencies - that's still dependent on the device restrictions. Where I expect that to make a difference is in cases like those cited by Peter, where in certain cases the GNSS/CF show up and in other cases (e.g., good signal strength) they don't in the same geographic area.

Which cases are you referring to?

Sean

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lodrog...@gmail.com

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Oct 31, 2021, 1:39:18 AM10/31/21
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there people that confuse the qualcomm izat power save mode (gnss receiver) with google OS power save mode (Force full GNSS measurements)

Sean Barbeau

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Oct 31, 2021, 10:44:05 AM10/31/21
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AFAIK there isn't any separate power savings mode built into Android OS (i.e., AOSP) for GNSS. 

"Force full measurements" seems like it's just a switch to tell the OEM to turn off any native power savings mode they may have implemented.

On Sun, Oct 31, 2021, 1:39 AM lodrog...@gmail.com <lodrog...@gmail.com> wrote:
there people that confuse the qualcomm izat power save mode (gnss receiver) with google OS power save mode (Force full GNSS measurements)

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Vicentiu

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Jan 18, 2023, 7:19:36 AM1/18/23
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Peter, It's a known issue on LineageOS roms that OnePlus 5/T only uses the GPS constellation.
The issue was recently fixed in LOS 20.

I'm interested in getting this fix into an already installed Android 10. I'll report back if I find anything.
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