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Voice Feature Guide 01

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Call Waiting

Call Waiting

The call waiting (CW) service is callee-side service. If it is provisioned and activated and the user who is engaged in an ongoing call is notified of a new incoming call, this new incoming call will be in waiting state and the waiting party hears the CW tone. The user can either accept, reject, or ignore this new incoming call.

Call Waiting

This topic describes the definition and principle of the call waiting (CW) service.

Definition

If this callee-side service is provisioned and activated and the user who is engaged in an ongoing call is notified of a new incoming call, this new incoming call will be in waiting state and the waiting party hears the CW tone. The user can either accept, reject, or ignore this new incoming call.

Assuming that user A registers the CW service, user B is placed on hold, and user C is the third party (CW party), the principle of the CW service is shown in Figure 1-47.
Figure 1-47 Principle of the CW service
  1. User A is communicating with user B.
  2. User C calls user A.
  3. User A receives the incoming call prompt from user C.
  4. User A wants to communicate with user C and places user B on hold.
  5. User A answers the call from user C.
  6. User A communicates with user C.
  7. User A presses hookflash to hold the call with user C.
  8. User A restores the call with user B.
Benefit

Beneficiary

Benefits

Carrier

The CW service helps improve the ratio of successful call connections, enhances carriers' competitiveness and provides carriers with new revenue growth potential.

Users

  • The CW service prevents a caller from dialing a number for multiple times and improves the ratio of successful call connections.
  • The CW service reduces the number of missed calls and the possibility of missing expected calls. The CW service can be canceled temporarily so that the ongoing call is not affected.
Standards Compliance
  • ETSI TS 03027
  • 3GPP TS 24615-820
  • ETSI EN 300 058-1
  • ETSI 300 102-1
  • ETSI TS 183 015
  • ETSI TS 186 022
  • ETSI TS 183 036
  • ETSI TS 183 043
  • ITU-T Q.931

Call Waiting Service Flow

This topic takes users A, B, and C as an example to describe the service flow of call waiting for a POTS and ISDN user.

POTS Call Waiting Service Flow

Figure 1-48 shows the service flow of the POTS call waiting service. User A is communicating with user B, user A places user B on hold and communicates with user C (from waiting to connected), and then user A puts user C on hold and communicates with user B (from on hold to connected).

Figure 1-48 POTS call waiting service flow

The call waiting service flow for a POTS user is as follows:
  1. User A is communicating with user B. User C picks up the phone and calls user A.
  2. AG2 sends an Invite message to user A.
  3. The IMS sends an Invite message to AG1.
  4. After receiving the call message from user C, AG1 determines that A has the call waiting service permission and plays the CW tone to A.
  5. AG1 sends a 182 response to the IMS.
  6. The IMS sends a 182 response to AG2.
  7. After receiving the 182 (or 180) response from the IMS, AG2 plays the ringback tone or call waiting tone to C.
  8. User A presses hookflash to answer the call from user C, hears the special dial tone, and dials 2 (SOC).
  9. After detecting the hookflash event, AG1 sends an Invite message to user B, setting the media stream direction to sendonly.
  10. After receiving the Invite message, the IMS sends the Invite message to AG2.
  11. After receiving the message, AG2 modifies the media attribute and direction of user B and returns a 200 OK response to the IMS. The 200 OK response carries the SDP, indicating that user B can only receive media.
  12. The IMS sends the 200 OK response to AG1.
  13. After receiving the 200 OK message, AG1 sends an Ack message to the IMS.
  14. The IMS sends an Ack message to AG2.
  15. User B is placed on hold and hears a call hold tone.
  16. AG1 returns a 200 OK response to user C. The 200 OK response carries an SDP packet, indicating that user A can receive and send media.
  17. The IMS sends a 200 OK response to AG2.
  18. After receiving the 200 OK message, AG2 sends an Ack message to the IMS.
  19. The IMS sends an Ack message to AG1. The call with user B is held successfully, and user B hears a call hold tone. User A starts communicating with user C.
  20. User A presses hookflash to communicate with user B, hears the special dial tone, and dials 2 (SOC).
  21. AG1 sends a ReInvite message to user C, with an SDP setting the media direction to sendonly.
  22. The IMS sends the ReInvite message to AG2.
  23. After receiving the ReInvite message, AG2 changes the media direction to recvonly and returns a 200 response to the IMS.
  24. The IMS sends a 200 message to AG1.
  25. AG1 sends an Ack message to the IMS.
  26. The IMS sends an Ack message to AG2.
  27. After receiving the Ack message, AG2 plays the call hold tone to user C and the call with user C is held successfully.
  28. After user C is held, AG1 sends a ReInvite message (in which the SDP direction is sendrecv) to resume the call with user B.
  29. The IMS receives the ReInvite message and sends the ReInvite message to AG2.
  30. After receiving the ReInvite message, AG2 changes the media direction to sendrecv and returns a 200 message to the IMS.
  31. The IMS sends the 200 message to user A.
  32. After receiving the 200 message, AG1 sends an Ack message to the IMS.
  33. The IMS sends an Ack message to AG2. The call between users A and B is resumed.
CW Service Flow for an ISDN User

The CW service flow for ISDN users is implemented in either of the following cases based on whether the service detection is performed on the IMS or ATOM GPS, as shown in Figure 1-49.

Figure 1-49 ISDN user CW service flow-IMS detection

The CW service flow for an ISDN user is as follows:
  1. User A is communicating with non-service user B. Non-service user C initiates a call to user A.
  2. AG2 initiates a call to user A.
  3. When the IMS determines that the number of calls and media of the called party exceeds the maximum number of calls and media, and no other services conflict with this call. That is, the CW service is triggered if the CW conditions are met. The IMS sends an Invite message to AG1. The Invite message carries the CW-Indication indicator.
  4. After receiving the Invite message that carries the CW-Indication indicator, AG1 determines that the CW service should be triggered by the IMS and maps the Setup message to the service party.
  5. User A answers the Alert message.
  6. AG1 sends a 180 response to the IMS and adds the P-Notification:Call is a waiting call header field to indicate the call waiting status.
  7. The IMS sends a 183 response to AG2.
  8. After receiving the 183 response, AG2 maps the 183 response to the Alert message of user C. The message carries the notification information element, telling user C: "Call is a waiting call."
  9. User A presses hookflash to place user B on hold.
  10. After detecting the hookflash event, AG1 converts the event into a ReInvite message and returns a user A Hold Ack response message.
  11. After receiving the ReInvite message, the IMS modifies the SDP and sends a ReInvite message to user B. After receiving the ReInvite message, AG2 modifies the media attribute of user B so that user B can only receive but cannot send media.
  12. AG2 sends a Notify message to notify user B that user B is held.
  13. AG2 sends a 200 OK response to the IMS.
  14. The IMS sends a 200 OK response.
  15. After receiving the 200 OK message, AG1 sends an Ack message to user B.
  16. The IMS sends an Ack message to user B.
  17. User A sends a Connect message for communicating with user C.
  18. After receiving the Connect message, AG1 maps the Connect message to the 200 message and sends the 200 message to the IMS.
  19. The IMS sends a 200 message to AG2.
  20. After receiving the 200 message, AG2 sends a Connect message to user C.
  21. After receiving the Connect message, user C returns a ConnectAck message.
  22. AG1 sends an Ack message to the IMS.
  23. The IMS sends an Ack message to AG2.
  24. User A receives a ConnectAck message. The call between users A and C is set up.
NOTE:
  • The preceding flow is the call waiting service detection flow on the IMS side. Another scenario involves detection on the AG side, as shown in the blue dashed line box in Figure 1-49. The difference between detection on the AG side and detection on the IMS side in the call waiting service flow for ISDN users is as follows: The Invite message sent from the IMS to AG1 does not carry the CW-Indication indicator. AG1 determines whether to trigger the CW service based on whether the called party has the CW service permission and whether the B channel is unavailable. The other steps are the same and are not described here.
  • When A has a call waiting message on the ISDN terminal, the following options are available: 1. to accept the waiting party and hold the current party; 2. to accept the waiting party and release the current party; 3. to reject the waiting party and continue the current call. The preceding service flow uses the first option as an example. The flow of accepting the waiting party, releasing the current party, and releasing the waiting party is the same as that of a basic call service. For details, see the corresponding service.
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Updated: 2019-02-22

Document ID: EDOC1100067358

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