A  Information flows for Lawful Interception invocation of circuit switched services  Word‑p. 283

The following figures show the information flows for the invocation of Lawful Interception for various types of calls. The figures show some of the basic signalling messages of the target calls and the events on the X2 and X3-interfaces. The call control messages to and from the network are shown for informational purposes only; some of them may not be sent or may be combined in certain networks. The handling of the bearers for the basic calls is not shown. The bearer points are established in a manner to minimise content loss without delaying the call to the target. The bearer establishment to agency will be in parallel or immediately following the bearer establishment to the target. The flows portray both forward and backward bearer establishment and release to the agency.

A.1  Mobile originated circuit switched calls

Figure A.1 shows the interception of a basic mobile originated circuit switched speech or data call where the originating mobile (A) is the target for interception. B is not necessarily also a mobile subscriber and resides on a different exchange.

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Figure A.1: Interception of mobile originated circuit switched calls

In Figure A.1 the result (answer) of the set-up of the stublines is not shown. This assumes no special action is taken in case of failure.

A.2  Mobile terminated circuit switched calls  Word‑p. 284

Figure A.2 shows the interception of a basic mobile terminated circuit switched speech or data call where the terminating mobile (B) is the target for interception. A is not necessarily also a mobile subscriber and resides on a different exchange.

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Figure A.2: Interception of mobile terminated circuit switched calls

A.3  Call hold / call waiting  Word‑p. 285

Figures A.3 and A.4 show the interception of calls involving call hold / call waiting. Figure A.3 covers the case where one pair of stublines is used per target, figure A.4 covers the case where a separate pair of stublines is used for each target call. The mobile that receives the waiting call (A) is the target for interception.

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Figure A.3: Interception of call hold / call waiting - stublines per target

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Figure A.4: Interception of call hold / call waiting - stublines per target call

A.4  Multiparty calls  Word‑p. 287

Figures A.5 and A.6 show the interception of multiparty calls. Figure A.5 covers the case where one pair of stublines is used per target, figure A.6 covers the case where a separate pair of stublines is used for each target call. The mobile setting up the multiparty call (A) is the target for interception.

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Figure A.5: Interception of multiparty calls - stublines per target

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Figure A.6: Interception of multiparty calls - stublines per target call

A.5  Call forwarding / call deflection  Word‑p. 290

A.5.0  General |R12|

The following pictures show the information flows for the interception of forwarded calls. Information flows will be given for three typical cases of call forwarding. All other types of call forwarding / call deflection are intercepted similar to one of these.

A.5.1  Unconditional call forwarding

Figure A.7 shows the interception of unconditionally forwarded calls. The mobile that activated unconditional call forwarding (B) is the target for interception. In this case interception will be performed at the 3G GMSC, where the Service Request Indicator (SRI) request for B is issued and subsequently the SRI response indicating that the call shall be forwarded is received.

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Figure A.7: Interception of unconditional call forwarding

A.5.2  Call forwarding on not reachable (IMSI detached)  Word‑p. 291

Call forwarding on not reachable because the IMSI is detached is also handled on the 3G GMSC. Interception of this type of call forwarding is similar to interception of unconditional call forwarding.

A.5.3  Call forwarding on busy (network determined)  Word‑p. 292

Figure A.8 shows the interception of call forwarding on busy (network determined). The mobile that activated call forwarding on busy (B) is the target for interception. In this case interception will be performed at the 3G MSC where B resides, where the busy condition is detected and the call is forwarded.

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Figure A.8: Interception of call forwarding on busy (network determined)

A.5.4  Call forwarding on not reachable (no response to paging/radio channel failure)  Word‑p. 293

Call forwarding on not reachable because of no response to paging or radio channel failure is also handled on the 3G MSC similar to call forwarding on busy (network determined). Interception of this type of call forwarding is therefore done in the same way (see clause A.5.3).

A.5.5  Call forwarding on no reply

Figure A.9 shows the interception of call forwarding on no reply. The mobile that activated call forwarding on no reply (B) is the target for interception. In this case interception will be performed at the 3G MSC where B resides, where the no reply condition is detected and the call is forwarded. Initially, the interception is similar to the interception of a basic mobile terminated circuit switched speech of data call. On no reply time-out, the interception will continue on the forwarded call to C.

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Figure A.9: Interception of call forwarding on no reply

In figure A.9 the release of the stublines is done after the forwarded call is released by A or C. It is a national option not to support interception of forwarded calls. In that case, the release of the stublines is done after the call is forwarded and B is no longer involved.

A.5.6  Call forwarding on busy (user determined)/call deflection  Word‑p. 294

Call forwarding on busy (user determined) and call deflection are also handled on the 3G MSC similar to call forwarding on no reply. Interception of this type of call forwarding is therefore done in the same way (see A5.5).

A.5.7  Call waiting / call forwarding on no reply  Word‑p. 295

Figures A.10 and A.11 show the interception of a call involving both call waiting and call forwarding on no reply. Figure A.10 covers the case where one pair of stublines is used per target, figure A.11 covers the case where a separate pair of stublines is used for each target call. The mobile that activated call forwarding on no reply and receives the waiting call (B) is the target for interception. In figure A.10 a new pair of stublines needs to be set up when the call is forwarded since the first pair of stublines is still used for the initial call.

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Figure A.10: Interception of call waiting / call forwarding on no reply - stublines per target

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Figure A.11: Interception of call waiting / call forwarding on no reply - stublines per target call

A.6  Explicit call transfer  Word‑p. 298

Figures A.12 and A.13 show the interception of explicit call transfer. Figure A.12 covers the case where one pair of stublines is used per target, figure A.13 covers the case where a separate pair of stublines is used for each target call. The mobile transferring the call (B) is the target for interception.

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Figure A.12: Interception of explicit call transfer - stublines per target

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Figure A.13: Interception of explicit call transfer - stublines per target call

In figures A.12 and A.13 the release of the stublines is done after the transferred call is released by A or C. It is a national option not to support interception of transferred calls. In that case, the release of the stublines is done after the call is transferred and B is no longer involved.

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