What it does

MMTel Communication Waiting (CW) is a service that alerts the subscriber when a new call arrives while a call is already in progress. The called party can accept, ignore, or reject the call. If accepted, the existing call can be put on hold.

This service can also play an announcement to the caller. See Announcements.

Interactions with other services

Call barring

The MMTel call barring services always take precedence over call waiting. If an incoming call is barred, the call will be terminated without waiting. See Call barring.

Communications Diversion (CDIV)

The MMTel CDIV takes precedence over communication waiting. If the called subscriber is already on a call, the call will be forwarded without waiting. See Communications Diversion (CDIV).

Communication Hold (HOLD)

If the subscriber accepts the new call, the call of current caller can be put on hold.


The example for sentinel-volte-gsm-config.yaml and example for sentinel-volte-cdma-config.yaml show example configuration relevant to call waiting in the sentinel-volte/mmtel/communication-waiting section.

What you need

  • ❏ The ID of the announcement to play to the caller.

  • ❏ The time in seconds to give the called party to answer the call before giving up and tearing down the call.

Setting up call waiting

I want to…​

Play an announcement to the caller that the call is waiting

Call waiting configuration only needs the announcement ID of the announcement to be played. The details of that announcement should be configured beforehand. For details about how to do this, see Announcements.


                announcement-id: 24
Change the number of seconds to give the called party to answer the call

In the communication-waiting section, set timer-seconds to the desired limit:

                timer-seconds: 30
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