x50-20100426-022 zte x.p 0057-a handover consideration for mupsap

7/29/2019 X50-20100426-022 ZTE X.P 0057-A Handover Consideration for MUPSAP

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X.P0057-A

Handover Considerations for MUPSAPZTE Corporation

Rajesh Bhalla, Bi YiFeng

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contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partners name any

Organizational Partners standards publication even though it may include portions of the contribution; and at the Organization Partners sole discretion

to permit others to reproduce in whole or in part such contributions or the resulting Organizational Partners standards publ ication. 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 Partners 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 thecontributor other than provided in the copyright statement above.

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.


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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 thesource access and multiple PDN connections to a single APN are notsupported via the target access, only one PDN connection to the given APNwill 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 thesource access and multiple PDN connections to a single APN is supported inthe target access, all PDN connections to the same APN shall be handed over.(Clause 8.1, TS23.402)

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A Handover Consideration for MUPSAP

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 firstcontribution of this feature in 3GPP2, the wrong name was copied. Now ZTE proposes to correct it as MUPSAP.


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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 toeHRPD

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

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Issue #1: Session Association

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3GPP Mechanism for Issue #1

Figure 1

For 3GPP access: how to match the PCC sessions, BCE and BULE with thePDN Contexts in the UE has been a major issue because the is no IP addressin the NAS: Attach request and PBU messages. Therefore, there is nodirect way for the P-GW and the PCRF to match the PCC sessions ,BCE andBULE with the UE PDN contexts

The solution adopted by 3GPP access: is that the P-GW and the PCRF pickthese sessions randomly, and the UE adjusts the PDN context via the NASmessaging . See Figure 1 above.

UE hands over from eHRPD to LTE 1

2 3

1

3

2

1 1

3

2

1.NAS: attachRequest2.

GCSSe

tup

3.PBU

4.ICSsetup

5

6.PBA7.NAS:attachacc

ept

MME/S-GWUE P-GW

PCRF

PDN context in UE

BULE in SGW

BCE in P-GW

PCC policy in PCRF

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3GPP2/eHRPD Solution Analysis for Issue #1

UE hands over from LTE to eHRPD 1

2 3

1

3

2

1

3

2

1.VSNCP config-Req(IP address)

2.GCSSetup

(IP

address)

3. PBU (IP address)

4.ICSsetup(IPaddress)

5. PBA6. VSNCP Config-Resp

HSGWUE P-GW

PCRF

PDN context in UE

BULE in HSGW

BCE in P-GW

PCC policy in PCRF

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 Aand X50-20100125-037r1 ZTE X.P0057 A PDN Address in Configure-Request messag.doc, it hasbeen agreed that the VSNCP and PBU messages contain the IP address whichhas 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 BCEbased on the IP address obtained from the PBU, PCC messages, thereby

associate with the PDN context in the UE unambiguously. See Figure 2.

Figure 2

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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.

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0 20 000 26 00 00


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Issue #2: Pre-registrationEstablishment and Maintenance

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Background

After the UE has pre-registered in eHRPD system, UE may not switch its radioto eHRPD from LTE at once. There is a period during which the UE and thenetwork should maintain and update the pre-registration information.

During the Pre-registration maintenance period, the UE may establish newPDN connection or release an existing PDN connection. If a pre-registered

PDN connection is released from LTE, the pre-registration information for thatPDN 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 PDNconnections 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 thelatest PDN connection out of the active PDN connections for the given APN, i.e. the PDNconnection that was activated last out of the active PDN connections for the given APN.

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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 TS23.402 requirements

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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.

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Issue Descriptions and Analysis [3]Solution and Proposal for Issue #2.2

Option 1: Even though a new PDN connection is established in R9 EPSsystem during the period between the pre-registration and handover to aRev-0 eHRPD system, the PDN connection pre-registration information willbe kept for the former pre-registered PDN connection. When the UEhands over to the Rev-0 eHRPD system, the pre-registered PDNconnection 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 PDNconnection as that chosen by the UE.

Option 2: If a new PDN connection is established in the R9 EPS systemduring the period between the pre-registration and handover to a Rev-0eHRPD system, the formerly pre-registered PDN connections pre-registration information should be deleted and the newly established PDNconnection should be pre-registered. See the Figure on next slide!

Proposal #2 : Adopt Option 2.

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Issue Descriptions and Analysis [4]Call flow: Option 2 for Issue #2.2

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

1st PDN conn

2nd PDN conn

2nd PDN conn pre-registration

3rd PDN conn

3rd PDN conn pre-registration

Note1: All the PDN connections shown in the Figure belongs to the same APN.

Note2: The eHRPD system (Rev 0) does not support MUPSAP.Note3: The LTE system (R9) supports MUPSAP.

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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 connectionbecomes 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

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Issue Description and Analysis [6]Call flow: for Issue 2.3

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

MS

S-GW

P-GW

HSGWMME

LTEeHRPD

1st PDN conn

2nd PDN conn

2nd PDN conn pre-registration

3rd PDN conn

3rd PDN conn pre-registration

Note1: All the PDN connections shown in the Figure belongs to the same APN.

Note2: The eHRPD system (Rev 0) does not support MUPSAP.Note3: The LTE system (R9) supports MUPSAP.

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Recommendations

Concept approve Proposal # 1



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Thanks!

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