We have done some testing with the STE modem for call termination,
and this is the result:
TC |Call #1 | Call #2 | Call #3 | Command | Result
1 |ACTIVE | ACTIVE | .. | ATH | call 1, 2 terminated
2 |ACTIVE | ACTIVE | .. | AT+CHUP | call 1, 2 terminated
3 |ACTIVE | ACTIVE | HELD | ATH | call 1, 2 terminated
4 |ACTIVE | ACTIVE | HELD | AT+CHUP | call 1, 2 terminated
5 |ACTIVE | ACTIVE | HELD | AT+CHLD=0;H | call 1, 2 and 3 terminated
6 |ACTIVE | ACTIVE | WAITING | ATH | call 1, 2 terminated
7 |ACTIVE | ACTIVE | WAITING | AT+CHUP | call 1, 2 terminated
8 |ACTIVE | HELD | WAITING | CHLD=0 | call 3 terminated,
9 |ACTIVE | HELD | WAITING | ATH | call 1 terminated
10 |ACTIVE | HELD | WAITING | AT+CHUP | call 1 terminated
11 |HELD | HELD | ACTIVE | AT+CHLD=0 | call 1, 2 terminated
12 |HELD | HELD | ACTIVE | AT+CHLD=0;H | call 1, 2 and 3 terminated
13 |HELD | DIALING | .. | ATH | call 2 (MO) terminated
14 |HELD | DIALING | .. | CHUP | call 2 (MO) terminated
15 |HELD | DIALING | .. | AT+CHLD=12 | call 2 (MO) NOT terminated
16 |HELD | WAITING | .. | AT+CHLD=0 | call 2 terminated
17 |HELD | .. | .. | ATH | call 1 NOT terminated
Denis Kenzior wrote:
>> oFono already takes care of this for single calls (see
>> src/voicecall.c voicecall_hangup.) So this is only an issue in the
>> case of three way calls, is this what you're referring to here?
> Kind of. This is very good, it takes care of the situation with
> emergency call which cannot be terminated with CHLD commands.
> But I think there are more issues. If I am not mistaken STE-modems
> have the following behavior:
> CHLD=1X can only terminate call in state ACTIVE or HELD. (I think
> is as STE interprets the standards).
The standards specify that CHLD=1X can only terminate an ACTIVE call.
Most modems implement it this way. There are vendor extensions that
provide this functionality (e.g. CHLD=7X on TI.) By default oFono
assumes that release_specific will simply fail if a user attempts to
use it on an e.g. HELD call with no modem support.
For the STE modem, AT+CHLD=1x terminates calls in state ACTIVE and HELD.
> a) If you are in a active call and receives a new incoming call
> (ALERTING) and want to reject the new ALERTING call, then STE modem
> cannot terminate this call with CHLD=1X. It has to be terminated
> with CHLD=0 (cause=BUSY) or ATH (possible CHUP).
Ok, lets get the terminology clear here. In this case the incoming
call is not ALERTING, it is WAITING. WAITING calls are always
rejected by using CHLD=0. ALERTING calls are always outgoing calls
that transitioned from DIALING to alerting the user.
> b) Or you may have the following situation. One call on HOLD,
> another ACTIVE call, and then you receive a new incoming call
> ALERTING. If you try to terminate the new incoming (ALERTING) call
> with CHLD=0,
> I think you as a side effect will terminate the call on hold as well.
> If I am not mistaken ATH (possible CHUP) would be the correct in this
> situation for STE modems
The standards are quite clear here, the WAITING call always takes
and thus only the WAITING call is affected. Can you check that STE
indeed get this wrong? If the modem is standards compliant, oFono
right thing here.
STE is standard compliant, only the WAITING call is terminated with AT+CHLD=0. (TC 8)
> c) If you have an call on hold and initiate a new call, but want to
> terminate the newly initiated call (DIALING), then this call cannot
> be terminated with CHLD=1X, but you would have to use ATH (or
> possible CHUP).
Yes, so this is the case that we do need to take care of in the core.
modems let us get away with sending release_specific up to this point.
For the STE modem, calls in state DIALING and ALERTING will have to be
terminated with ATH or AT+CHUP, AT+CHLD=1x does not work.
This means that the current implementation, using release_specific
(and thus AT+CHLD=1x) will not work.
>> What I have been considering to take care of this case is to
>> end_all and end_all_active callbacks. According to 27.007/22.030
>> ATH should end all calls (active + held) except waiting calls, while
>> +CHUP should only end the currently active call. At least on one TI
>> modem I tried this works as expected. Do your modems implement the
>> same behavior?
> No, I don't think so. I think ATH will only terminate one call.
> In order to terminate all calls you would probably need to do
> something like: AT+CHLD=0;H But I'm not sure this works in all
> possible scenarios either...
Can you check the behavior of ATH vs CHUP on STE modems? We need to
right one here or both HELD and ACTIVE/DIALING/ALERTING will be
If using CHUP and ATH doesn't work out we'll have to come up with
For the STE modem, ATH will only terminate the active call,
not the held call. (TC 9). For more information about ATH and AT+CHUP,
please see the table above.