[MM RFC] Signal quality and access technology

[Aleksander Morgado <aleksander lanedo com>]

Hey,

In the new MM DBus API we allow reporting multiple current access
technology values, for modems which can connect to more than one network
at a time (e.g. CDMA1x and EV-DO, or LTE).

But, we still report only a single signal quality value, while each
access technology may have its own. Currently the choice of which to
report is let to the core or plugin implementation; e.g. the base logic
is to report the maximum value of those gathered (in QMI modems). A
better approach is probably to give different priority to different
technologies, e.g. give LTE signal quality value if that is available,
otherwise give WCDMA signal quality value if that is available,
otherwise give GPRS/EDGE signal quality value if that is available. Same
could apply for EV-DO and CDMA1x.

Anyway, given that we're still changing the DBus API, why not just let
the users of the interface decide which signal quality value to report?
Instead of giving a "ub" signal quality ("u" for the value, "b" to
indicate if the value is taken in the last 60s), we could give it as an
*array* of "uub" values (being the additional first "u" the access
technology). This would effectively mean that we're merging the signal
quality values reported with the access technology report (which is now
given as a bitmask in a single "u" value).

Another approach, if we still want to keep the consolidated single
signal quality value, would be to implement a completely new
Modem.Signal interface with deeper details of the current radio signal.
We could give per-access-technology details, including Ec/Io, RSSI, GSM
timing advance...

Thoughts?

-- 
Aleksander