TS 23.402**): Non-Roaming Reference
Architecture for non-3GPP Accesses
HSS
Wx*
**) Colouring of non3GPP accesses and red
arrows (incl. text in red)
added for this
presentation
2G/3G
SGSN
S6a
S4
PCRF
S3
MME
Rx+
S7
S11
SGi
S1-MME
S10
EUTRAN
S1-U
Serving
SAE
Gateway
PDN
SAE
Gateway
S5
Operator’s IP
Services
(e.g. IMS, PSS
etc.)
S6c
S2b
S2c
S2a
3GPP AAA
Server
Wn*
HPLMN
Trusted/Untrusted*
Non-3GPP IP
Access
or 3GPP Access
Trusted
Non-3GPP
IP Access
UE
* Untrusted non3GPP access
requires ePDG in the
data path
Wm*
ePDG
Handovers (Discovery and
Selection of non-3GPP Access
is needed before)
Untrusted
Non-3GPP
IP Access
Non3GPP
Networks
Wa*
Ta*
1
Key Issue NW Discovery & Selection (NW-DS)
(Excerpt from TR 23.882)
It is necessary to optimize NW-DS procedures for frequent mobility events.
It is desirable that the concept for NW-DS in SAE supports effective means for
minimizing processing.
Looking at the currently defined NW-DS principles for I-WLAN in TS 23.234 it becomes
clear that they cannot be extended for time critical handovers and for other RATs, due to
complexity and latency:
 per available WLAN access NW a scan/probe has to be performed
 if a WLAN AN is connected to more than one 3GPP NW this is only detected after
L2 association and trying authentication.
It is therefore necessary to develop or adopt new, more efficient mechanisms, for both
idle and active mode (where this differentiation is applicable).
Solutions may be based on concepts developed in other fora (e.g. IEEE 802.11u, IEEE
802.21, IETF) or based on concepts defined by 3GPP (e.g. provision of specific
databases). Further mechanisms are FFS. When selecting solutions, the amount of
signalling, size of stored and transferred data, especially over the radio interface, and
terminal power consumption shall be taken into account.
2
Example of HO Message Flow
(from informative annex of TS 23.402)
Untrusted
Untrusted
Non-3GPP
non-3GPP
Access
IPIPAccess
UE
EUTRAN
Serving
GW
MME
-
PDN
GW
ePDG
HSS/
AAA
PCRF
1. GTP/PMIPv6 Tunnel
2. UE discovers the
2. UE discovers the untrusted
untrusted
non-3GPP
non-3GPP access
system and
initiates
HO
access system
and
initiates HO
3. Access Auth
3. Access Authentication
4. ePDG
Discovery
5. IKEv2/Ipsec SA setup (CoA config)
5. AAA Auth/ Authz
6. AAA Auth/
6. IKEv2/Ipsec SA setup
Authz
7. BU/BA (IP Addr)
8. DSMIPv6 Tunnel
Ipsec Tunnel
3