1
|
A handover
trigger occurs at the UE.
|
2, 3
|
RRC
Connection Request/Connection Setup. The UE and eNodeB exchange signaling to
set up an RRC connection (5.3.3, TS 36.331).
|
4
|
RRC
Connection Setup Complete [Attach Request]. The UE sends RRC Connection Setup
Complete message to the eNodeB.
|
5
|
Attach
Request from eNB to MME. The UE indicates in the Attach Request to LTE that
this is a Handover Attach. The eNodeB selects the MME. The eNodeB forwards the
Attach Request message in an Initial UE Message to the MME.
|
6
|
MME
selects the same P-GW of SAEGW based on HSS provided PGW FQDN and sends the
Create Session request.
|
8
|
The MME
selects the PGW/SGW of SAEGW. The MME sends a Create Session Request to the SGW
of SAEGW with RAT as EUTRAN and the handoff indicator set to TRUE.
|
9
|
The SGW of
SAEGW sends a Create Session Request to the PDN GW in order to establish the
handoff (handoffindicator is set to true). RAT type is E-UTRAN.
|
10
|
P-GW of
SAEGW to PCRF CCR IP-CAN Session Modification Procedure. The PCEF sends a
CC-Request (CCR) Command with CC-Request-Type set to UPDATE_REQUEST. The
APN-AMBR is included in the QoS-information AVP.
|
12
|
The P-GW
of SAEGW sends AAR to 3GPP-AAA and includes the RAT type of the new connection.
|
SW1.
SAR/SAA
|
The
3GPP-AAA sends SAR to HSS to retrieve the user profile, the HSS returns an SAA.
The P-GW-FQDN is not updated as the 3GPP-AAA is not registered for this user.
|
11
|
PCRF to
P-GW of SAEGW: CCA IP-CAN Session modification Procedure. On receiving the CCR
the PCRF shall send a CC-Answer (CCA) Command to install the PCC rules and
event triggers for all configured and established bearers. The QoS-Information
AVP contains APN-AMBR-UL and APN-AMBR-DL.
|
13
|
The
3GPP-AAA responds with AAA.
|
16
|
P-GW of
SAEGW to S-GW of SAEGW: Create Session Response + Create Bearer Request. The
P-GW of SAEGW responds with a Create Session Response message to the S-GW of
SAEGW. The P-GW of SAEGW provides IPv6 Prefix.
Subject to
operator configuration the P-GW of SAEGW can begin to forward downlink data and
the S-GW of SAEGW buffers any downlink data packets.
|
17
|
P-GW of
SAEGW to OFCS: ACR. After the P-GW of SAEGW sends the PBA, the P-GW of SAEGW
sends an ACR-Interim to the OFCS.
|
18
|
OFCS to
P-GW of SAEGW: ACA. The OFCS responds with an ACA to the P-GW.
|
19
|
Create
Session Response. The S-GW of SAEGW sends Create Session Response to the MME.
|
20
|
Initial
Context Setup Request/Attach Accept. The Attach Accept is sent as NAS PDU in
the Initial Context Setup Request from MME to eNodeB. Attach Accept message
contains new GUTI.
|
D
|
These
procedures occur independently of the location procedures. These procedures
only apply to initial attach scenarios.
|
21
|
RRC
Connection Re-configuration. The eNodeB sends the RRC Connection
Reconfiguration message including the EPS Radio Bearer Identity to the UE, and
the Attach Accept message to the UE. The APN is provided to the UE to notify it
of the APN for which the activated default bearer is associated.
|
22
|
RRC
Connection Re-configuration Complete. The UE sends the RRC Connection
Reconfiguration Complete message to the eNodeB.
|
23
|
Initial
Context Setup Response. The eNodeB sends Initial Context Setup Response to the
MME.
|
24
|
Uplink
Information Transfer. The UE sends an Uplink Information Transfer message.
|
25
|
Attach
Complete. The eNodeB forwards the received Attach Complete message in an Uplink
NAS Transport as part of NAS PDU.
|
26
|
Uplink
Information Transfer. When the UE has received Activate dedicated EPS Bearer
Context Request message in the Attach Accept message, the UE sends Activate
Dedicated EPS Bearer Context Accept message in a Uplink Information Transfer
message.
|
27
|
UL NAS
Transport. The eNB passes the Activate Dedicated EPS Bearer Context Accept
message received in Step 14.b, to the MME in a UL NAS Transport message. At
this time, the uplink data can be sent on the dedicated bearer.
|
32
|
Router
Solicitation. This step may happen any time after step 26. For IPv6 PDN, the UE
may send a Router Solicitation to the P-GW.
|
33
|
Router
Advertisement. This step may happen any time after step 29 if the UE requested
IPv4v6 or IPv6 PDN type. On receipt of the RS or prior the P-GW of SAEGW sends
a Router Advertisement and include the globally unique /64 IPv6 prefix
previously assigned.
|
28
|
Modify
Bearer Request / Create Bearer Response. On receiving both Initial Context
Setup Response and Attach Complete, the MME sends a Modify Bearer Request
message to the S-GW of SAEGW.
The MME
piggybacks the Modify Bearer Request message on the Create Bearer Response
message.
|
29
|
The S-GW
of SAEGW processes each message independently. The S-GW of SAEGW forwards the
Create Bearer Response to the P-GW. At this time, the P-GW of SAEGW can send
downlink data on the dedicated bearer for the IMS traffic.
Since
Handover Indication is set to TRUE in the Modify Bearer Request, the S-GW of
SAEGW sends Modify Bearer Request to the P-GW of SAEGW separately.
Based on
TS 23.401, the P-GW of SAEGW switches the downlink traffic to S5 upon receiving
this message. However, subject to operator configuration, this switching occurs
at Create Session Request above (C3).
|
30
|
The P-GW
of SAEGW sends Modify Bearer Response (Cause) message to the S-GW.
|
C1. CCR-u
|
P-GW of
SAEGW to OCS: CCR-U. If the Online AVP is set in the CCA from the PCRF, the
P-GW of SAEGW conditionally sends a CCR-Update to the OCS to request online
charging quota for the PDN session.
|
C1. CCA-u
|
OCS to
P-GW of SAEGW: CCA. The OCS responds with a CCA to the P-GW of SAEGW.
|
31
|
The S-GW
of SAEGW sends Modify Bearer Response to the MME. The S1 S-GW F-TEID is the
same as the S1-U S-GW F-TEID sent in Create Session Response from the S-GW of
SAEGW to the MME.
The S-GW
of SAEGW can now start sending downlink packets to eNB and the switching of the
data path from WiFi to LTE occurs after the Modify Bearer Response.
|
33a
|
SIP
Re-registration RAT Change. The UE sends a SIP Re-Register to the P-CSCF to
indicate that it detected a RAT change and assigned IP address remained
unchanged.
|
34
|
P-GW of
SAEGW to ePDG: Delete Bearer Request. The P-GW of SAEGW sends Delete Bearer
Request to ePDG to disconnect the session.
|
35
|
ePDG to
UE: IKEv2 Information Delete Request. The ePDG sends IKEv2 Informational Delete
Request () to UE to disconnect the session.
|
34
|
UE to
ePDG: IKEv2 Informational Delete Response. UE responds with IKEv2 Information
Delete Response () and initiates air interface resource release. This step is
conditional and UE may not send this response.
|
37
|
ePDG to
P-GW of SAEGW: Delete Bearer Response. The ePDG sends Delete Bearer Response to
the P-GW.
|
38
|
ePDG to
AAA: Session Termination Request. The ePDG sends STR to the 3GPP AAA.
|
39
|
AAA to
HSS: Server Assignment Request. The AAA sends Server-Assignment-Request to
de-register.
HSS to
AAA: SAA. The HSS sends Server-Assignment-Answer.
|
40
|
AAA to
ePDG: Session Termination Answer. The AAA sends STA to the ePDG.
|