Page 274 - 5G Basics - Core Network Aspects

1 Core network aspects

After the steps above, MUE_A and UE_B have established a call. It contains two service components for
MUE_A, which are through different interfaces and different networks, and only one service component for
UE_B.

IV.5 Service decomposition during call establishment
A service that supports multi-connection capability can be decomposed into several service components. The
procedure in the figure below takes place during call establishment. This procedure supports several of the
use cases described in [b-ITU-T Y-Sup.9].

MUE_B MUE_B
UE_A SCF(A) MAS_F SCF (B1) SCF (B2)
IF(1) IF(2)
1. SC-1 initial Req
2. SC-1 initial Req
3. Initial SC-2 and SC-3
with decomposed
SC related info of SC-1
4. SC-2 initial Req
5. SC-3 initial Req
6. Forward SC-2 initial Req
7. Forward SC-3 initial Req
8. SC-2 initial response
9. SC-3 initial response
10. Forward SC-2 initial response
11. Forward SC-3 initial response

12. Compose SC related
info and construct a new
response for UE_A
13. SC-1 initial Resp
14. Forward SC-1 initial Resp
Service component Service component to MUE_B IF(1)
from UE_A
Service component to MUE_B IF(2)

Y.2027(12)_FIV.6

Figure IV.6 – Service decomposition during call establishment
1)-2) UE_A, which can be an MUE or even an ordinary UE, initiates a service (SC-1) to MUE_B, which is an
MUE. The initial request is routed to SCF(A), and SCF(A) forwards it to MAS-F.
3) MAS-F identifies that SC-1 can be decomposed for MUE_B, since MUE_B is an MUE. So MAS-F splits
the SDP descriptions extracted from the initial request of SC-1, and initiates two new service
components (SC-2 and SC-3) to two interfaces of MUE_B, i.e., MUE_B IF(1) and MUE_B IF(2).
4)-7) MAS-F sends the new initial requests the MUE_B. The requests are routed through SCF(B1) and
SCF(B2) which correspond to the different interfaces of MUE_B.
8)-11) The responses are routed to MAS-F via the SCFs.
12) MAS-F composes service component related information from the two responses, and constructs a
new response.
13)-14) The responses are routed to UE_A through SCF(A).
After the steps above, UE_A and MUE_B have established a call. Within it, there are two service components
for MUE_B, which are through different interfaces and different networks, and only one service component
for UE_A.

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