Multi-party call Process

 

One call is in the activate status. Assume that you need to call another call and Access Point meetings,

1)
Atd10010; activate one call

2)
At + chld = 2, faclity UE-> NW, hold current active call

3)
Atd10086; activate the second call;

4)
At + chld = 3, add the held call to the conversation

 

(4) After that, the entire conversation is an activate multi-party call. If you still need to use the MO method to add another call together, Repeat 2.
-4; multi-party call of MT
Process:

1)
Atd10010; activate on call

2)
The MT call comes in. The ATC receives the message app_mn_setup_ind, And the ATC reports the message ecind.
Notification AP;

3)
AP uses at + chld = 2: Hold current activate call, answer incoming call;

4)
If you want to build multi-party call, the AP sends at + chld = 3

 

From the process, we can see that for mt call to use at + chld = 2, an AT command contains two processes: 1) hold the current active status call 2) Answer the call from Mt. In this test scenario, the call of MT comes in, the AP sends at + chld = 2, the first step is OK, and the current call is held, is to answer the second call of incomoing
At the underlying layer, T200 times out, and the link fails, causing the MT call to fail to be answered. Therefore, the ATC replies with an error. At this time, a call on the modem side has been held, but because the CME error is returned, the AP considers the at failure and the hold failure;

The AP and modem status are inconsistent. How can this problem be solved?