Difference between "Usage preference" "voice-centric" or "data-centric"?

[Dan Williams]

On Wed, 2025-02-12 at 18:31 +0100, Martin Maurer wrote:
> Hello,
> 
> when using this command:
> 
> # qmicli -p -d /dev/cdc-wdm0 --nas-get-system-selection-preference
> [/dev/cdc-wdm0] Successfully got system selection preference
>          Emergency mode: 'no'
>          Mode preference: '5gnr'
>          Disabled modes: 'none'
>          Band preference: 'wcdma-2100, wcdma-pcs-1900, wcdma-1700-us,
> wcdma-850-us, wcdma-900, wcdma-850-japan'
>          LTE band preference: '1, 2, 3, 4, 5, 7, 8, 12, 13, 14, 17,
> 18, 
> 19, 20, 25, 26, 28, 29, 30, 32, 34, 38, 39, 40, 41, 42, 43'
>          LTE band preference (extended): '1, 2, 3, 4, 5, 7, 8, 12,
> 13, 
> 14, 17, 18, 19, 20, 25, 26, 28, 29, 30, 32, 34, 38, 39, 40, 41, 42,
> 43, 
> 46, 48, 66, 71'
>          NR5G SA band preference: '1, 2, 3, 5, 7, 8, 12, 13, 14, 18,
> 20, 
> 25, 26, 28, 29, 30, 38, 40, 41, 48, 66, 70, 71, 75, 76, 77, 78, 79'
>          NR5G NSA band preference: '1, 2, 3, 5, 7, 8, 12, 13, 14, 18,
> 20, 25, 26, 28, 29, 30, 38, 40, 41, 48, 66, 70, 71, 75, 76, 77, 78,
> 79'
>          TD-SCDMA band preference: 'a, b, c, d, e, f'
>          Roaming preference: 'any'
>          Network selection preference: 'automatic'
>          Service domain preference: 'cs-ps'
>          GSM/WCDMA acquisition order preference: 'automatic'
>          Usage preference: 'data-centric'
>          Voice domain preference: 'ps-preferred'
>          Registration restriction: 'unrestricted'
>          Acquisition order preference: '5gnr, lte, umts'
> #
> 
> there is "Usage preference", which can be "voice-centric" or "data-
> centric".
> 
> In Quectel RM520N-GL there is an AT command, where I can choose
> between 
> the two modes.
> 
> What is the difference between them?
> 
> What does the module do different when choosing the one or the other?
> 
> Could it be (with voice centric) that it builds up a connection to 
> somewhere, for voice calls,
> which could influence my data calls (especially when choosing APN/IP-
> Type)?

I'm not 100% sure, but I believe if voice-centric is selected then the
device should try as hard as it can to only attach to networks that
provide voice services. That might mean detaching from 5G and re-
attaching to LTE automatically if the 5G network doesn't provide voice
services that the device wants or is capable of using.

I would say that unless you care about voice calls, keeping the usage
preference as data-centric is probably best.

Dan