Architecture and Handoff with S-RNC Fatih Ulupinar, Peerapol Tinnakornsrisuphap, Jun Wang Notice...
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Transcript of Architecture and Handoff with S-RNC Fatih Ulupinar, Peerapol Tinnakornsrisuphap, Jun Wang Notice...
Architecture and Handoff with S-RNC
Fatih Ulupinar, Peerapol Tinnakornsrisuphap, Jun Wang
NoticeContributors grant 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 are 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 the 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 contributors. Contributors specifically reserve 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 contributors other than provided in the copyright statement above.
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Potential Architecture with S-RNC
HomeAgent
eBTS
S-RNC
AccessGateway
eBTS eBTS
IAP
AccessGateway
eBTS
S-RNC
eBTS eBTS
WiFiAP
PDIF
3
Pros & Cons of S-RNC
• Potential benefits of separating S-RNC from eBS
– Reliability of Users session• Centrally located S-RNC provides higher reliability to user’s session
compared to eBTS deployed at the edge.
– Provide UATI stability as IAP moves between eBSes.• Note, UATI HA can provide UATI stability using an off-the-shelf
solution.• Separate S-RNC solution does not require a UATI-HA
– Centralize paging area management
• Disadvantages of S-RNC
– Additional protocol complexity as new interfaces has to be defined
– One more (S-RNC) air interface aware node has to be built
4
Functions of S-RNC
• Session Anchor (Session Storage Point)
– UATI Points to S-RNC
• Paging and Location Management
• Idle State Management
• EAP Authenticator Functions (see EAP Authenticator Placement contribution)
– AAA Client
• Optionally served as IAP when the AT is in idle State:
– Buffer Incoming User Data when the AT is in idle state
– PMIP Client
5
Related Entities• Internet Attachment Point (IAP) – the entity that the AGW points its
tunnel for FL traffic to
• S-RNC is a separate functional entity from AN. However, the AT always maintain a logical route to S-RNC, i.e., S-RNC is also a member of the Active Set
• S-RNC can either be a stand-alone entity, collocated with AGW or collocated with eBS. This allows flexible deployment options based on operators and vendors’ requirements
• As a member of the Active Set, S-RNC may become IAP if appropriate– Alternatively, UMB air-interface allows S-RNC to disable data through S-
RNC route if S-RNC cannot handle user data
6
S-RNC Interfaces
• Interface between S-RNC and eBS:
– Same as inter-eBS interface
– Key is distributed to the eBS
• Interface between S-RNC and AGW:
– No specific 3GPP2 signaling interface is needed between S-RNC and AGW
– Same as interface between eBS and AGW
– PMIP tunneling can be established when the AT moves to idle
7
Paging Options
• Allows both the following options:
– Option 1: (IAP (Data Anchor) is always separate than S-RNC)• IAP receives the data from AG• IAP contacts S-RNC for paging• S-RNC pages via other APs• AT accesses APx• APx retrieves data from the IAP and forwards to AT• APx starts L3 HO to itself
– Option 2: (S-RNC is the IAP when idle)• S-RNC receives data from AG• S-RNC pages via other APs• AT accesses APx• APx retrieves data from the S-RNC and forwards to AT• APx starts L3 HO to itself
• If an S-RNC vendor can not handle user data, then it can use option 1
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Paging (Option1)
AN2 IAP ANAT AN1 AN3
10. Traffic Channel established
6. AN3 pages the AT in the designated paging cycle
2. AT registers with S-RNC through AN3 (UATI)
3. Paging Request
5. PagingRequest
5. Paging Request
6. AN2 pages the AT in the designated paging cycle
6. AN1 pages the AT in the designated paging cycle
7.AT requests connection with AN1 (UATI)
Data Data
AGW
Registration Trigger
Data
S-RNC
4. S-RNC determines paging area of the AT
based on AT’s registration
5. PagingRequest
8. AN1 retrieves a copy of the session
1. IAP doesn’t change when AT goes to Idle
9. AN1 establishes L3 Tunnel
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Paging (Option2)
AN2AT AN1 AN3
8. Traffic Channel established
5. AN3 pages the AT in the designated paging cycle
2. AT registers with IAP through AN3 (UATI)
4. PagingRequest
4. Paging Request
5. AN2 pages the AT in the designated paging cycle
5. AN1 pages the AT in the designated paging cycle
6. AT requests connection with AN1 (UATI)
Data Data
AGW
Registration Trigger
Data
S-RNC
1. S-RNC becomes IAP when AT goes to Idle
4. PagingRequest
7. AN1 retrieves a copy of the session and establishes L3 Tunnel
3. S-RNC determines paging area of the AT
based on AT’s registration
10
Why Data should be buffered in IAP?- If AGW buffers the data when AT is idle
• AGW needs to be aware of the status of the AT (active/idle)
– Extra signaling messages need to be defined• This will be 3GPP2 UMB specific functionality• Even PDSN right now is not aware of the status of the AT – PCF was created to ‘shield’
such information from PDSN• AGW has two different behaviors depending on the status of the AT – introducing more
race conditions, error scenarios to be addressed (e.g., AT is active while AGW still believes AT is idle) and additional delay
• Air-interface does not only have active and idle state but also has semi-connected state and these may change in the future – change in the air-interface spec should not affect AGW
– Excessive additional signaling load will be introduced• eBS needs to inform AGW every time an AT changes status from active to idle – this is a
very frequent event, for example– To save power, AT may transition to idle state after a short inactivity timer expires – this can be
during a short reading time between each web page or Instant Messaging KeepAlive
– Every time AT wakes up to register, the AGW will receive idle->active indication and then immediately active->idle indication
– Bandwidth between AGW to eBS is likely to be limited and expensive• We do not believe this is a scalable solution when the number of AT served by AGW is
large
• The concept is unproven – no other system has chosen this particular design
11
Why Data should be buffered in IAP?- If IAP buffers the data when AT is idle
• If buffering data at the eBS is a concern, then S-RNC can become IAP when AT becomes idle
– Typical amount of data that needs to be buffered when AT is idle is small anyway, e.g., Mobile-Terminated SIP INVITE
• Allow flexibility for deployment options depending on the physical location of S-RNC while the standard can remain option-free
• No need for defining extra interfaces
– Between AGW and BS for AT status update
– Between S-RNC and AGW for paging trigger
• Compatible with the current PDSN functionalities
• Avoid extraneous signaling messages as IAP location is more stable than active/idle states
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Active Set Add (AN2 belongs to same AGW, Interface ID=AGW1 )
ATAN1
(IAP/FLSA/RLSA)
AN2
Phy Signal
AN-AN MsgData MIP Signal
L2 Signal IMS SignalTunneled Data
AT is in connected-state with AN1/S-RNC in the Active Set
RLP Tunnel
[AN2]RouteOpenRequest
(RouteID) UMB:RouteOpenRequestCT-Session
Information Request(SessionSignature)
CT-Session Information Notification
(SessionSignature, Session, IAP ANID)
Active Set Add completes; AN1/AN2/AN3/S-RNC are all in the Active Set
AT wants to add AN2 into Active Set
RouteOpenAccept(Interface ID)
Manycast [AN1-3]:RouteIDMapping UMB:RouteIDMapping
UMB:RouteIDMapping
Ack
Ack
UMB:RouteOpenAccept (Interface ID)
S-RNC
L3TunnelSetup
L3TunnelSetup
13
Active Set Add (AN2 belongs to different AGW, Interface ID=AGW1 )
ATAN1
(IAP/FLSA/RLSA)
AN2
Phy Signal
AN-AN MsgData L3 Signal
L2 Signal IMS SignalTunneled Data
Same as singe AG Active Set Add call flow except for Interface ID=AGW2
RLP Tunnel
PMIP BU
PMIP BA (AT’s Prefix /64 or AT’s IP add)
Route Advertisement (AT’s Prefix /64)
S-RNC AGW2
Simple IPv6
MIPv4 FA CoAFA Advertisement (FA CoA)FA Advertisement (FA CoA)
Simple IPv4DHCPDISCOVERw/Rapid Commit
DHCPACK w/Rapid Commit (AT’s IP Add)
New IP Interface Created
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L3 HO w FL Data (Intra-AG HO, no CoA change)
AT SS ANSource IAP AN
AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
PMIP-BA
PMIP-BU
IAPMoveReq(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data
Data
Data
Notify(IAP)
NotifyAck
IAPAssignment(Accept, NoAck)
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L3 HO w RL Data (Intra-AG HO, no CoA change) *Assuming reverse tunneling through IAP
AT SS ANSource IAP AN
AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
PMIP-BA
PMIP-BU
IAPMoveReq(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data Data Data
Data Data Data
Data Data Data
Notify(IAP)
NotifyAck
IAPAssignment(Accept, NoAck)
16
L3 HO w RL Data (Intra-AG HO, no CoA change)*Assuming RL data can be directly tunneled from RLSA to AG
AT SS ANSource IAP AN
AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
DataAnchorMoveReq(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data Data
Data Data
Data Data
Notify(IAP)
NotifyAck
DataAnchorAssignment(Accept/Reject, NoAck)
PMIP-BACK
PMIP-BU
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L3 HO w FL data (Inter-AG HO, CoA change)AT SS AN
Source IAP AN
Source AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
PMIP-BACK
PMIP-BU
IAPMoveRequest(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data
Data
Leftover data in Source AG
HATargetAG
Notify(IAP)
NotifyAck
IAPAssignmentProcessed( Transaction_ID)
IAPAssignment(T1,Accept, ProcessCompletinAckRequired)
BU
BAck
AT can not drop Target A-AN from AS Data
18
L3 HO with RL data (CoA change, Inter-AG HO)*Assuming RL data can be directly tunneled from RLSA to AG
AT SS ANSource IAP AN
Source AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
PMIP-BACK
PMIP-BU
DataAnchorMoveRequest(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data
Data
HATargetAG
Notify(IAP)
NotifyAck
DataAnchorAssignmentProcessed(TransID)
DataAnchorAssignment(TransId,Accept, ProcessCompletinAckRequired)
BU
BAckData
AT can not drop Target IAP-AN from AS
To AS members
19
L3 HO with RL data (CoA change, Inter-AG HO)*Assuming reverse tunneling through IAP
AT SS ANSource IAP AN
Source AG
AT decides to do L3 handoff
Target IAP AN
NotifyAck
Notify(IAP)
Phy Signal
Backhaul SigData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
PMIP-BACK
PMIP-BU
DataAnchorMoveRequest(SeqNo)
S-RNC
Notify(IAP)
NotifyAck
Data
Data
HATargetAG
Notify(IAP)
NotifyAck
DataAnchorAssignmentProcessed(TransID)
DataAnchorAssignment(TransId,Accept, ProcessCompletinAckRequired)
BU
BAck
Leftover data from Source A-AN
Data
AT can not drop Target IAP-AN from AS
To AS members
20
S-RNC HO
AT SS APPrev
S-RNC
UATIAssign(UATI_n)
TargetS-RNC
UATIComplete(UATI_n,TargetRouteID)
Phy Signal
Backhaul MsgData MIP Signal
L2 Signal
L2TP Tunnel
IMS SignalTunneled Data
To AS members
Start timer to Release Previous
UATI
From AS Members
RouteClose() If Prev S-RNC is not in Radio Active Set
MoveSession
MoveSessionAck(Session, Current IAP,
SessionSig) Allocate UATI_n
MoveSessionCompleted
AGW/LAAA
HAAA
Optional EAP Re-authentication
EAP/RLP or EAP-ER/RLP EAP/AAAEAP/AAA
21
Recommendations
• No Specific 3GPP2 signaling interface between S-RNC and AGW
– Same interface as eBS-AGW interface shall be used
• Buffer the incoming data in either S-RNC or IAP when the MS is in idle
• AGW shall be an access agnostic entity