5 Support by "old" MSs
24.0913GPPExplicit Call Transfer (ECT) supplementary serviceRelease 17Stage 3TS
MSs which do not explicitly support ECT are not precluded from attempting to invoke ECT. It is however, an operator option to support the invocation of ECT by these mobile stations. Where operators support this option, the mechanism employed to offer the ECT service to these MSs shall be USSD. However, it should be noted that it may not be possible using this mechanism to offer the same degree of service to the served subscriber as described in clause 4.
5.1 Explicit Call Transfer invocation
MS A invokes the service by sending a REGISTER message to the network using a call independent supplementary service (SS) transaction, with the facility information element, indicating ProcessUnstructuredSS‑Request (the MMI is specified in 3GPP TS 22.030).
If the invocation of ECT is successful, then after the SS transaction has been cleared, the network shall release the CC transactions.
If the invocation of ECT is not successful, then the CC transactions shall not be released.
MS Network
REGISTER (PD=SS)
———————————————————————————————————————>
Facility (Invoke = ProcessUnstructuredSS-Request (ussd-DataCodingScheme,
ussd-String = <ECT Invocation String>))
RELEASE COMPLETE (PD=SS)
<———————————————————————————————————————
Facility (Return Result = ProcessUnstructuredSS-Request (ussd-DataCodingScheme,
ussd-String = <Successful Text String>))
DISCONNECT/RELEASE/RELEASE COMPLETE (TI=A-B, PD=CC)
<———————————————————————————————————————
DISCONNECT/RELEASE/RELEASE COMPLETE (TI=A-C, PD=CC)
<———————————————————————————————————————
RELEASE COMPLETE (PD=SS)
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – — – – – – – – – – — – – – – – –
Facility (Return Result = ProcessUnstructuredSS-Request (ussd-DataCodingScheme,
ussd-String = <Error Text string>))
RELEASE COMPLETE (PD=SS)
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – — – – – – – – – – — – – – – – –
Facility (Return error (Error))
RELEASE COMPLETE (PD=SS)
<- – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – — – – – – – – – – — – – – – – –
Facility (Reject (Invoke_problem))
Figure 6: Invocation of Explicit Call Transfer for non supporting MSs
NOTE: The text strings "<Successful Text String>" and "<Error Text String>" shall be defined by the network operator. Each network shall define only one "<Successful Text String>" and only one "<Error Text string>" for each error identified in table 1.
For Phase 1 USSD the operation ProcessUnstructuredSS-Request is replaced by ProcessUnstructuredSS-Data.
5.2 Notification to the remote parties
No alternative procedures are defined for sending notifications to remote parties indicating that the call has been transferred.
Annex A (informative):
Change history
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Change history |
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Date |
Meeting |
TDoc |
CR |
Rev |
Cat |
Subject/Comment |
New version |
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Apr 1999 |
Transferred to 3GPP CN1 |
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CN#03 |
Approved at CN#03 |
3.0.0 |
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CN#11 |
Approved at CN#11 |
4.0.0 |
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CN#16 |
References updated |
4.0.1 |
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CN#16 |
Rel-5 created after CN#16 |
5.0.0 |
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CN#26 |
Rel-6 created after CN#26 |
6.0.0 |
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CT#36 |
Upgraded unchanged from Rel-6 |
7.0.0 |
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CT#42 |
Upgraded unchanged from Rel-7 |
8.0.0 |
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2009-12 |
Update to Rel-9 version (MCC) |
9.0.0 |
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2011-03 |
Update to Rel-10 version (MCC) |
10.0.0 |
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2012-09 |
Update to Rel-11 version (MCC) |
11.0.0 |
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2014-09 |
Update to Rel-12 version (MCC) |
12.0.0 |
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2015-12 |
Update to Rel-13 version (MCC) |
13.0.0 |
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2017-03 |
Update to Rel-14 version (MCC) |
14.0.0 |
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2018-06 |
Update to Rel-15 version (MCC) |
15.0.0 |
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2020-07 |
Update to Rel-16 version (MCC) |
16.0.0 |
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2022-03 |
CT#95e |
– |
– |
– |
– |
Update to Rel-17 version (MCC) |
17.0.0 |