dun APN type from your APN
configuration.
- If your chosen carrier includes the supl APN type in their APN
- configuration, SUPL will be used to provide A-GNSS in order to greatly improve
- location lock time for GNSS (GPS, GLONASS, etc.). The fallback SUPL server is
- supl.google.com if the carrier doesn't choose a specific one. You
- can remove supl from APN types if you don't want to use this, but
- it will greatly increase GNSS location lock time if your carrier lacks control
- plane A-GNSS via the cellular network and fully relies on user plane A-GNSS
- (SUPL) to provide this instead.
When you have both a cellular connection and Location enabled, control plane
+ and/or user plane (SUPL) A-GNSS is used in addition to PSDS to greatly reduce
+ the time needed for GNSS to obtain an initial location lock. These obtain
+ coarse location info from a server based on nearby cell towers. Control plane
+ A-GNSS is provided by the cellular connection itself and therefore doesn't
+ have any real privacy implications while SUPL connects to a server often not
+ provided by the carrier. Most A-GNSS services only accelerate obtaining a satellite-based
+ location and won't provide an estimate on their own. The carrier can choose a
+ SUPL server as part of their carrier configuration but most leave it at the
+ default of supl.google.com. By default, GrapheneOS overrides the
+ carrier/fallback SUPL server and uses the supl.grapheneos.org proxy. GrapheneOS adds a
+ toggle for configuring SUPL in Settings ➔ Location where you can choose
+ between the default supl.grapheneos.org proxy, the standard server
+ (carrier/fallback) or disabling it completely. GrapheneOS also disables
+ sending IMSI and phone number as part of SUPL. Pixels with a Qualcomm baseband
+ use it to provide both cellular and GNSS including both control plane and user
+ plane A-GNSS being implemented inside the baseband. For Qualcomm baseband
+ devices, SUPL is only enabled if the APN configuration for the carrier
+ includes supl as an APN type. Pixels with a Samsung baseband have
+ a separate Broadcom GNSS chip without integration between them so SUPL is done
+ by the OS with regular networking (can use Wi-Fi and VPN) and SUPL is used
+ regardless of the carrier's APN type configuration. GrapheneOS upgrades the
+ Broadcom SUPL implementation to only using TLSv1.2 instead of using TLSv1.1
+ and older.
MMS, RCS, SMS over LTE, VVM (Visual Voicemail), VoLTE (carrier-based calls on 4G and higher) and VoWi-Fi are largely implemented by the OS via TCP/IP