Incoming line identity and ALS

[Denis Kenzior]

Hi Chris,

> Hi all,
>
> I've been looking through the 0.8 source code for some indication of ALS
> support.
>
> ALS (or line-2) allow two different numbers to be attached to a mobile
> device. The device can accept calls from both numbers and make calls from
> either of the two numbers, effectively acting as if two lines were
> attached to the device.

ALS was never part of the core GSM specification.  It was an extension 
supported by several network providers and phone manufacturers.  It was 
incorporated into recent GSM specifications as 'Multiple Subscriber Profile.'

> First is selecting which line/number to use when making a call. I'm not
> certain how handsets make this distinction and I wonder if it might be
> vendor specific.. Changing out bound line seems to be set as a mode rather
> than on a
> per-call basis. Switching out bound lines is sometimes locked with PIN1.

This is done as a supplementary service control sent to the network over USSD.  
The details are pretty sketchy but the basics are described in 22.030 Section 
6.5.6.1.

>
> The other problem is identifying which line was called by a remote caller.
> I believe +CDIP includes this information (after each RING / +CRING)
>
> From what I've seen of the API, it has the ability to report the caller
> identity for in bound calls and the dialed number for out bound calls, but
> I can't seem to find any reference to the number called for in bound calls
> which would be used to identify which line was ringing..

CDIP (like CLIP) is issued after every RING/CRING.  Whereas CLIP returns the 
calling line identity, CDIP returns the called line identity (e.g. the phone 
number the remote caller dialed.)  According to the specification it is not 
reported for outbound calls.

>
> I was wondering if this service has been considered for ofono or if
> perhaps it is already there and I've missed it..

oFono currently does not support ALS/MSP and we do not foresee enabling this 
feature in the near term.  If you would like to help out, code / research / 
documentation contributions are always welcome :)

Regards,
-Denis