4 User-to-User Signalling (UUS); served mobile subscriber side

04.873GPPStage 3TSUser-to-User Signalling (UUS) supplementary service

4.1 UUS1

For UUS1, both parties may exchange UUI during the set-up and the clearing phases of a call by including User-user information element(s) in basic call control messages (ALERTING, CONNECT, DISCONNECT, PROGRESS, RELEASE, RELEASE COMPLETE, SETUP).

UUS1 can be activated implicitly or explicitly. When UUS1 has been activated, either subscriber may include UUI when accepting, rejecting or terminating the call.

UUS1 is automatically deactivated when the call is cleared.

4.1.1 Operation when implicitly activated

To activate UUS1 implicitly, the MS A shall include a User-user information element in the SETUP message as part of a normal call request. See GSM 04.08. Implicitly activated UUS1 is active for the duration of the call; i.e. the remote party is not required to send a response to the implicit activation request. However, the remote party may include a User-user information element in the call response.

The served subscriber or the remote party may terminate the call before a connection is established.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
User-user

.
ALERTING
<—————————————————————————————————————————-
User-user (Note 1)

CONNECT
<—————————————————————————————————————————-
User-user (Note 1)

.

.
DISCONNECT / RELEASE / RELEASE COMPLETE
<—————————————————————————————————————————>
User-user (Note 1), (Note 2)

NOTE 1: The User-user information element is optional.

NOTE 2: Under normal conditions DISCONNECT message is used for clearing the call, but also RELEASE or RELEASE COMPLETE message may be used as the first call clearing message.

Figure 1: UUS1 when implicitly activated

4.1.2 Operation when explicitly activated

UUS1 is explicitly requested by the MS A when including a Facility information element with a UserUserService invoke component in the SETUP message. See GSM 04.08, GSM 04.80. The UserUserService invoke component shall indicate whether the service is "UUS required" or "UUS not required".

If the remote party accepts the request, the network shall include a Facility information element with a UserUserService Return Result component in the ALERTING or the CONNECT message sent to the MS A.

If the request is not accepted, the network shall include a Facility information element with a UserUserService Return Error component in the DISCONNECT message (when UUS required) or in the ALERTING or in the CONNECT message (when UUS not required) sent to the MS A. See errors in GSM 04.80.

An explicit activation request may include UUI. The network may include User-user information element when accepting the activation request.

The served subscriber or the remote party may terminate the call before a connection is established.

For UUS1 explicit activation SS Version Indicator value 3 or above has to be used.

4.1.2.1 UUS required

If the MS A gives the "UUS required" indication, the call shall not be completed if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS1, UUS required)), User-user (Note 1)

.

.

ALERTING
<—————————————————————————————————————————-
Facility (Return Result), User-user (Note 1), (Note 2)

DISCONNECT / RELEASE COMPLETE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error), Cause (Note 3)

CONNECT
<—————————————————————————————————————————-
User-user (Note 1), (Note 2), (Note 4)

.

.
DISCONNECT / RELEASE / RELEASE COMPLETE
<—————————————————————————————————————————>
User-user (Note 1), (Note 5)

NOTE 1: The User-user information element is optional.

NOTE 2: The Return Result component in the Facility information element shall be sent either in the ALERTING or in the CONNECT message.

NOTE 3: If the remote party rejects the service request or does not respond with an explicit service 1 acceptance or rejection, DISCONNECT message is sent to the MS A with Facility information element including Return Error component with error value "rejectedByUser". If the network rejects the request, the error value shall be "rejectedByNetwork". See information on Cause values in Annex A.

NOTE 4: If the MS A does not receive an explicit service 1 acceptance or rejection in the ALERTING or the CONNECT message, the MS A shall clear the call. UUS1 is not activated.

NOTE 5: Under normal conditions DISCONNECT message is used for clearing the call, but also RELEASE or RELEASE COMPLETE message may be used as the first call clearing message.

Figure 2: Request for explicit activation of UUS1, UUS required

4.1.2.2 UUS not required

If the MS A gives the "UUS not required" indication, the call will be completed even if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS1, UUS not required)), User-user (Note 1)

.

.

ALERTING
<—————————————————————————————————————————-
Facility (Return Result), User-user (Note 1), (Note 2)

ALERTING / CONNECT

<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error) (Note 3)

CONNECT
<—————————————————————————————————————————-
User-user (Note 1), (Note 2)

.

.

.
DISCONNECT / RELEASE / RELEASE COMPLETE
<—————————————————————————————————————————>
User-user (Note 1), (Note 4)

NOTE 1: The User-user information element is optional.

NOTE 2: The Return Result component in the Facility information element shall be sent either in the ALERTING or in the CONNECT message.

NOTE 3: If the MS A does not receive an explicit service 1 acceptance or rejection in the ALERTING or the CONNECT message, the served subscriber shall continue normal call handling. UUS1 is not activated.

NOTE 4: Under normal conditions DISCONNECT message is used for clearing the call, but also RELEASE or RELEASE COMPLETE message may be used as the first call clearing message.

Figure 3: Request for explicit activation of UUS1, UUS not required

4.2 UUS2

For UUS2, both parties may send UUI after the alerting indication has been sent/received and until the connect indication has been sent/received. The UUI is sent in USER INFORMATION message and is limited to two messages in each direction.

UUS2 is automatically deactivated when the called subscriber is no longer being informed of the call, i.e. if the call is established or released.

4.2.1 Operation

In order to activate UUS2 the MS A shall include a Facility information element with a UserUserService invoke component indicating service 2 in the SETUP message. See GSM 04.08, GSM 04.80. The UserUserService invoke component shall also indicate whether the service is "UUS required" or "UUS not required".

If the remote party accepts the request, the network shall include a Facility information element with a UserUserService Return Result component in the ALERTING message received by the MS A.

If the request is not accepted, the network shall include a Facility information element with a UserUserService Return Error component in the DISCONNECT message (when UUS required) or in the ALERTING or in the CONNECT message (when UUS not required) sent to the MS A. See errors in GSM 04.80.

At any time between the activation of UUS2 and the connection is being established, either subscriber may transfer up to two USER INFORMATION messages in each direction to the other subscriber involved in the call.

User-user information element is mandatory in USER INFORMATION message (refer GSM 04.08). More data information element may be included in USER INFORMATION message indicating that another USER INFORMATION message pertaining to the same message block will follow.

For UUS2 activation SS Version Indicator value 3 or above has to be used.

4.2.1.1 UUS required

If the MS A gives the "UUS required" indication, the call shall not be completed if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS2, UUS required))

.

.

ALERTING
<—————————————————————————————————————————-
Facility (Return Result) (Note 1)

DISCONNECT / RELEASE COMPLETE / RELEASE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error), Cause (Note 2)

USER INFORMATION
<—————————————————————————————————————————->
User-user, More data (Note 3)

.

.
CONNECT
<—————————————————————————————————————————-
(Note 1)

NOTE 1: If the MS A does not receive an explicit service 2 acceptance or rejection in the ALERTING message or does not receive an ALERTING message before receiving the CONNECT message, the served subscriber shall clear the call. UUS2 is not activated.

NOTE 2: If the remote party rejects the service request or does not respond with an explicit service 2 acceptance or rejection, DISCONNECT message is sent to the MS A with Facility information element including Return Error component with error value "rejectedByUser". If the network rejects the request, the error value shall be "rejectedByNetwork". See information on Cause values in Annex A.

NOTE 3: User-user information element is mandatory and More data information element is optional in USER INFORMATION message.

Figure 4: Request for explicit activation of UUS2, UUS required

4.2.1.2 UUS not required

If the MS A gives the "UUS not required" indication, the call will be completed even if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS2, UUS not required))

.

.

ALERTING
<—————————————————————————————————————————-
Facility (Return Result) (Note 1)

ALERTING
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error))

USER INFORMATION
<—————————————————————————————————————————>
User-user, More data (Note 2)

.

.
CONNECT
<—————————————————————————————————————————-
(Note 1)

NOTE 1: If the MS A does not receive an explicit service 2 acceptance or rejection in the ALERTING message or does not receive an ALERTING message before receiving the CONNECT message, the served subscriber shall continue normal call handling. UUS2 is not activated.

NOTE 2: User-user information element is mandatory and More data information element is optional in USER INFORMATION message.

Figure 5: Request for explicit activation of UUS2, UUS not required

4.3 UUS3

For UUS3, both parties may send UUI in the active phase of a call using USER INFORMATION messages.

UUS3 shall be activated explicitly, when a call is originated or after the connection has been established.

After UUS3 has been activated, either subscriber may transfer UUI in USER INFORMATION messages to the other subscriber on the call.

UUS3 is automatically deactivated when the call is released.

For UUS3 activation SS Version Indicator value 3 or above has to be used.

4.3.1 Activation when originating a call

When UUS3 is activated during call establishment, the MS A shall include Facility information element with UserUserService operation in an Invoke component indicating UUS3 in the SETUP message. See GSM 04.08, GSMĀ 04.80. The UserUserService operation shall also indicate whether the service is "UUS required" or "UUS not required".

If the remote party accepts the request, the network shall include a Facility information element with a UserUserService Return Result component in the CONNECT message sent to the MS A.

If the request is not accepted, the network shall include a Facility information element with a UserUserService Return Error component in the DISCONNECT message (when UUS required) or in the CONNECT message (when UUS not required) sent to the MS A. See errors in GSM 04.80.

4.3.1.1 UUS required

If the MS A gives the "UUS required" indication, the call shall not be completed if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS3, UUS required))

.

.
CONNECT
<—————————————————————————————————————————-
Facility (Return Result) (Note 1)

DISCONNECT / RELEASE COMPLETE / RELEASE
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error), Cause (Note 2)

NOTE 1: If the MS A does not receive an explicit service 3 acceptance or rejection in the CONNECT message, the MS A shall clear the call.

NOTE 2: If the remote party rejects the service request or does not respond with an explicit service 3 acceptance or rejection, DISCONNECT message is sent to the MS A with Facility information element including Return Error component with error value "rejectedByUser". If the network rejects the request, the error value shall be "rejectedByNetwork". See information on Cause values in Annex A.

Figure 6: Request for explicit activation of UUS3 when originating a call, UUS required

4.3.1.2 UUS not required

If the MS A gives the "UUS not required" indication, the call will be completed even if UUI cannot be passed to the remote party.

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS3, UUS not required))

.

.
CONNECT
<—————————————————————————————————————————-
Facility (Return Result)

CONNECT
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error)) (Note 1)

NOTE 1: If the MS A does not receive an explicit service 3 acceptance or rejection in the CONNECT message, the MS A shall continue normal call handling and assume that service 3 is not activated.

Figure 7: Request for explicit activation of UUS3 when originating a call, UUS not required

4.3.2 Activation during an active call

When UUS3 is activated during an active call, the MS A shall include a Facility information element with a UserUserService invoke component indicating service 3 in a FACILITY message. See GSM 04.08, GSM 04.80. The UserUserService operation shall indicate that the service is "UUS not required".

If the remote party accepts the request, the network shall include a Facility information element with a UserUserService Return Result component in the FACILITY message sent to the MS A.

If the request is not accepted, the network shall include a Facility information element with a UserUserService Return Error component in the FACILITY message sent to the MS A. See errors in GSM 04.80.

MS A NETWORK
Active call
<—————————————————————————————————————————->

FACILITY
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS3, UUS not required))

FACILITY
<—————————————————————————————————————————-
Facility (Return Result)

FACILITY
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Facility (Return Error (Error)) (Note 1)

NOTE 1: If the remote party rejects the service request or does not respond with an explicit service 3 acceptance of rejection, the FACILITY message includes Facility information element with Return Error component indicating error "rejectedByUser". If the network rejects the request, the error value shall be "rejectedByNetwork".

Figure 8: Request for explicit activation of UUS3 during an active call

4.3.3 Invocation and operation

After Service 3 has been activated, either subscriber may transfer UUI in USER INFORMATION messages to the other subscriber on the call after the connection has been established. User-user information element is mandatory in USER INFORMATION message. More data information element may be included in USER INFORMATION message indicating that another USER INFORMATION message pertaining to the same message block will follow.

MS A NETWORK
Active call
<—————————————————————————————————————————->

USER INFORMATION
<—————————————————————————————————————————->
User-user, More data (Note 1)

.

.
DISCONNECT /RELEASE / RELEASE COMPLETE
<—————————————————————————————————————————>
(Note 2)

NOTE 1: User-user information element is mandatory and More data information element is optional in USER INFORMATION message.

NOTE 2: Under normal conditions DISCONNECT message is used for clearing the call, but also RELEASE or RELEASE COMPLETE message may be used as the first call clearing message.

Figure 9: Sending USER INFORMATION messages when UUS3 has been activated

4.3.4 Flow Control

Network flow control mechanisms shall exist after the call has entered the Active call state to control USER INFORMATION message flow in each direction.

If USER INFORMATION messages are received at a rate which exceeds the flow control limit set by the network, the network shall discard the USER INFORMATION messages that cannot be handled and respond to the first discarded USER INFORMATION message with a control indication.

If USER INFORMATION message has been discarded due to flow control, a CONGESTION CONTROL message shall be sent to the MS.

When the flow control restrictions are removed, and a USER INFORMATION message has been discarded due to that restriction, an indication that further USER INFORMATION messages can be accepted shall be given.

MS A NETWORK
Active call
<—————————————————————————————————————————->

USER INFORMATION
—————————————————————————————————————————–>
User-user, More data (Note 1)

.

.
USER INFORMATION
—————————————————————————————————————————->
User-user, More data (Note 1), (Note 2)

CONGESTION CONTROL
<—————————————————————————————————————————–
Congestion level = receiver not ready, Cause #43 (access information discarded)

.

USER INFORMATION
—————————————————————————————————————————–>
User-user, More data (Note 1), (Note 2)

.

.

CONGESTION CONTROL
<—————————————————————————————————————————-
Congestion level = receiver ready

NOTE 1: User-user information element is mandatory and More data information element is optional in USER INFORMATION message.

NOTE 2: Due to the flow control the USER INFORMATION message is discarded.

Figure 10: UUS3, Flow control

A more detailed presentation of flow control mechanisms is given in UUS Stage 2.

4.4 Combination of UUS Services

Depending on the served subscriber’s subscription to the UUS supplementary service and the provision of the UUS services by the service provider, UUS1 implicit or explicit, UUS2 and UUS3 can be activated individually or in combination.

The following figure is an example of the situation, when UUS1, UUS2 and UUS3 are simultaneously activated as "UUS required".

MS A NETWORK
SETUP
—————————————————————————————————————————–>
Facility (Invoke=UserUserService (UUS1, UUS required), Invoke=UserUserService (UUS2, UUS required),
Invoke=UserUserService (UUS3, UUS required)), User-user (Note 1)

.

.

ALERTING
<—————————————————————————————————————————-
Facility (Return Result, Return Result), User-user (Note 1), (Note 2)

.

.

.
CONNECT
<—————————————————————————————————————————-
Facility (Return Result), User-user (Note 1), (Note 2)

NOTE 1: The User-user information element is optional.

NOTE 2: For UUS1 the Return Result component in the Facility information element may be sent either in the ALERTING or in the CONNECT message. For UUS2 the Return Result component in the Facility information element is sent in the ALERTING message. For UUS3 the Return Result component in the Facility information element is sent in the CONNECT message.

Figure 11: Request for explicit activation of UUS1, UUS2 and UUS3 simultaneously