Transcript X.P 0057-A:eHRPD Optimized HO for MUPSAP

X.P0057-A
Handover Considerations for MUPSAP
ZTE Corporation
Rajesh Bhalla, Bi YiFeng
Abstract: This contribution highlights some issues related to MUPSAP handover
between LTE and eHRPD systems. The contribution also provides two proposals for
addressing these issues.
Recommendations: Discuss and concept approve the proposals.
Contributors grants a free, irrevocable license to 3GPP2 and its Organization Partners to incorporate text or other copyrightable material contained in the
contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner’s name any
Organizational Partner’s standards publication even though it may include portions of the contribution; and at the Organization Partner’s sole discretion
to permit others to reproduce in whole or in part such contributions or the resulting Organizational Partner’s standards publication. Contributors is also
willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of
practicing an Organizational Partner’s standard which incorporates this contribution.
This document has been prepared by Contributors to assist the development of specifications by 3GPP2. It is proposed to the Committee as a basis for
discussion and is not to be construed as a binding proposal on the contributor. Contributors specifically reserves the right to amend or modify the material
contained herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to any intellectual property of the
contributor other than provided in the copyright statement above.
1
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Background
• MUPSAP Note allows multiple PDN connections to an APN by the same UE
• PC-ID is used to distinguish multiple PDN connections to the same APN
• LTE and eHRPD systems choose their respective IDs as the PC-ID
– LTE chooses LBI as the PC-ID
– eHRPD has chosen the PDN-ID/UC-ID as the PC-ID
• During inter-RAT HO:
– If the UE hands over between 3GPP access and a non-3GPP access (e.g.,
eHRPD) and the UE has more than one PDN connection to a given APN in the
source access and multiple PDN connections to a single APN are not
supported via the target access, only one PDN connection to the given APN
will be established in the target access. (Clause 8.1, TS23.402)
– If the UE hands over between 3GPP access and a non-3GPP access (e.g.,
eHRPD) and the UE has more than one PDN connection to a given APN in the
source access and multiple PDN connections to a single APN is supported in
the target access, all PDN connections to the same APN shall be handed over.
(Clause 8.1, TS23.402)
Note: The real short name of “Multiple PDN Connections to the Same APN for PMIP-based Interfaces” is MUPSAP but not
MAPSUP. But during the R9 phase in 3GPP, the MAPSUP and MUPSAP were used in a confusion, because of that, in the first
contribution of this feature in 3GPP2, the wrong name was copied. Now ZTE proposes to correct it as MUPSAP.
2
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Some Related Issues
• Issue #1: Session Association
– How to match the PCC sessions, BCE and BULE with the PDN
Contexts in the UE, when the UE requests PDN connections
with “Attach type=HO” during HO procedure from LTE to
eHRPD
• Issue #2: Pre-registration establishment and
maintenance for multiple PDN connections
Note: In this contribution, all the PDN connections refer to the multiple PDN connections that belong to the
same APN
3
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue #1: Session Association
4
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
3GPP Mechanism for Issue #1
PCRF
1
UE hands over from eHRPD to LTE
2
PDN context in UE
5
PCC policy in PCRF
Se
1
2
2.
1.NAS: attach Request
ccept
attach a
7. NAS:
1
3
UE
p
tu
se
GC
S
S
IC
4.
tu
p
BULE in SGW
3
BCE in P-GW
3. PBU
6. PBA
1
2
3
MME/S-GW
P-GW
Figure 1
• For 3GPP access: “how to match the PCC sessions, BCE and BULE with the
PDN Contexts in the UE” has been a major issue because the is no “IP address”
in the “NAS: Attach request” and “PBU” messages. Therefore, there is no
direct way for the P-GW and the PCRF to match the PCC sessions ,BCE and
BULE with the UE PDN contexts
• The solution adopted by 3GPP access: is that the P-GW and the PCRF pick
these sessions randomly, and the UE adjusts the PDN context via the NAS
5
messaging . See Figure 1 above.
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
3GPP2/eHRPD Solution Analysis for Issue #1
PCRF
1
UE hands over from LTE to eHRPD
1
PDN context in UE
BCE in P-GW
BULE in HSGW
PCC policy in PCRF
1.VSNCP config-Req
(IP address)
6. VSNCP Config-Resp
2.
G
(IP CS S
ad etu
dr
es p
s)
2
4.
IC3
S
se
tu
p
3. PBU (IP address)
5. PBA
(IP
ad
dr
e
ss
)
1
2
2
3
3
UE
HSGW
P-GW
Figure 2
• In 3GPP2 (eHRPD) access , the case is different compared to that in 3GPP
• During the discussion of “X50-20100125-015 ZTE Discussion paper on PDN address in X.P0057 A”
and “X50-20100125-037r1 ZTE X.P0057 A PDN Address in Configure-Request messag.doc”, it has
been agreed that the VSNCP and PBU messages contain the IP address which
has been allocated in the source network during the HO from LTE to eHRPD.
• Then the P-GW and the PCRF can match the PCC sessions, BULE and BCE
based on the IP address obtained from the PBU, PCC messages, thereby
associate with the PDN context in the UE unambiguously. See Figure 2.
6
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Conclusion for Issue #1
• In eHRPD, the P-GW and the PCRF can associate the PCC
sessions, BULE and BCE with the UE PDN context based on
the IP address in the VSNCP, PBU, and PCC messages.
• The existing messages and parameter are enough to associate
these sessions unambiguously, and there is no need to update
the call flows etc.
• Proposal #1:
As the solution in 3GPP2 is different from that in the 3GPP: it
is proposed that the requirements for the P-GW and the PCRF
for matching the PCC sessions, BCE and BULE to the UE PDN
Context based on the IP address, be made clear by the use of
clarification text in X.S0057-A.
7
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue #2: Pre-registration
Establishment and Maintenance
8
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Background
•
After the UE has pre-registered in eHRPD system, UE may not switch its radio
to eHRPD from LTE at once. There is a period during which the UE and the
network should maintain and update the pre-registration information.
•
During the Pre-registration maintenance period, the UE may establish new
PDN connection or release an existing PDN connection. If a pre-registered
PDN connection is released from LTE, the pre-registration information for that
PDN connection should be updated.
•
In 3GPP TS 23.402, it is required as that:
– If the UE hands over between 3GPP access and a non-3GPP access and the UE has more
than one PDN connection to a given APN in the source access and multiple PDN
connections to a single APN are not supported via the target access, only one PDN
connection to the given APN will be established in the target access.
– In order for the PDN GW and the PCRF to select the same PDN connection out of the
active PDN connections for a given APN, the PDN GW and the PCRF shall select the
latest PDN connection out of the active PDN connections for the given APN, i.e. the PDN
connection that was activated last out of the active PDN connections for the given APN.
9
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue Descriptions and Analysis [1]
Issue Description #2.1
• Issue #2.1: When the UE handovers to a Rev-0
eHRPD system which does not support MUPSAP
from a R9 EPS system which supports MUPSAP: the
latest PDN connection is to be selected in the eHRPD
system !!
– Needs to be assured: in order to be compliant to 3GPP TS
23.402 requirements
10
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue Descriptions and Analysis [2]
Issue Description #2.2
• Issue #2.2: If a new PDN connection to one APN which has
multiple PDN connections in a R9 EPS system is initiated
during the pre-registration information maintenance period,
then the pre-registered PDN connection is not the latest one
in Rev-0 eHRPD system
• When the UE hands over to the Rev-0 eHRPD system, which
PDN connection should be established in the eHRPD access?
– The pre-registered one or the newly established one?
– How do the PCRF, the P-GW and the UE choose the same PDN
connection.
11
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue Descriptions and Analysis [3]
Solution and Proposal for Issue #2.2
• Option 1: Even though a new PDN connection is established in R9 EPS
system during the period between the pre-registration and handover to a
Rev-0 eHRPD system, the PDN connection pre-registration information will
be kept for the former pre-registered PDN connection. When the UE
hands over to the Rev-0 eHRPD system, the pre-registered PDN
connection will be handed over, and the other (including the latest) PDN
connections will be released.
– Shortcoming 1: This solution is not aligned with the 3GPP requirements: only
the latest PDN connection should be handed over.
– Shortcoming 2:The P-GW and the PCRF cannot choose the same PDN
connection as that chosen by the UE.
• Option 2: If a new PDN connection is established in the R9 EPS system
during the period between the pre-registration and handover to a Rev-0
eHRPD system, the formerly pre-registered PDN connection’s preregistration information should be deleted and the newly established PDN
connection should be pre-registered.
– See the Figure on next slide!
• Proposal #2 : Adopt Option 2.
12
Issue Descriptions and Analysis [4]
Call flow: Option 2 for Issue #2.2
P-GW
MME
S-GW
P-GW
HSGW
MME
S-GW
eHRPD
LTE
HSGW
eHRPD
LTE
MS
MS
1st PDN conn
2nd PDN conn
2nd PDN conn pre-registration
3rd PDN conn
3rd PDN conn pre-registration
P-GW
P-GW
MME
S-GW
HSGW
MME
S-GW
HSGW
eHRPD
LTE
eHRPD
LTE
MS
MS
Note1: All the PDN connections shown in the Figure belongs to the same APN.
X50-201000426-xxx ZTE X.P0057 X.P 0057Note2: The eHRPD system (Rev 0) does not support MUPSAP.
A Handover Consideration for MUPSAP
Note3: The LTE system (R9) supports MUPSAP.
13
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Issue Descriptions and Analysis [5]
Issue Description #2.3
• Issue #2.3: If the latest established PDN connection (which is
registered in eHRPD) is released in the R9 EPS system during
the pre-registration information maintenance period, then
the pre-registration information for the released PDN
connection is useless, the second-latest PDN connection
becomes the latest one now.
• Should the second-latest PDN connection (now the latest one)
be pre-registered in Rev-0 eHRPD?
– Yes.
– See the Figure in next page.
• Proposal #3 : Adopt the above stated proposal
14
Issue Description and Analysis [6]
Call flow: for Issue 2.3
P- GW
MME
S-GW
P- GW
HSGW
MME
S-GW
eHRPD
LTE
eHRPD
LTE
1st PDN conn
2nd PDN conn
2nd PDN conn pre-registration
3rd PDN conn
3rd PDN conn pre-registration
MS
HSGW
MS
P- GW
P- GW
MME
S-GW
HSGW
MME
eHRPD
LTE
MS
Note1: All the PDN connections shown in the Figure belongs to the same APN.
X50-201000426-xxx ZTE X.P0057 X.P 0057Note2: The eHRPD system (Rev 0) does not support MUPSAP.
A Handover Consideration for MUPSAP
Note3: The LTE system (R9) supports MUPSAP.
S-GW
HSGW
eHRPD
LTE
MS
15
Recommendations
• Concept approve Proposal # 1
• Concept approve Proposal # 2
• Concept approve Proposal # 3
16
X50-201000426-xxx ZTE X.P0057 X.P 0057A Handover Consideration for MUPSAP
Thanks!
17