Transcript Network-based mobility management in the evolved 3GPP

IEEE Communications Magazine, vol. 47, no. 2, pp. 58-66, 2009.
Network-Based Mobility Management
in the Evolved 3GPP Core Network
Irfan Ali, Motorola Inc.
Alessio Casati, Alcatel-Lucent
Kuntal Chowdhury, Starent Networks
Katsutoshi Nishida, NTT DoCoMo Inc.
Eric Parsons, Nortel Networks
Stefan Schmid, NEC Europe Ltd.
Rahul Vaidya, Samsung India Software Operations
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Outline
• Introduction
• Network-Based IP Mobility Management
• Network-Based Mobility Architecture of the EPC (evolved
packet core)
• Inter-Access System Mobility Flows
– Non-Optimized Handovers
– Optimized Handovers
• Summary and Future Work
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Introduction
• The Evolved Packet Core (EPC) of 3GPP system
– supports multiple access networks
– one common packet core network for 3GPP radio accesses (EUTRAN, UTRAN, and GERAN), as well as other wireless and wireline
access networks (e.g., eHRPD, WLAN, WIMAX, and DSL/Cable),
• providing the operator with a common set of services and capabilities
across the networks.
• A key requirement of the EPC is to provide seamless
mobility at the IP layer
– as the user moves within and between accesses.
– maintaining QoS is an important facet
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• This article provides an overview of the EPC specifications
– a network-based mobility mechanism based on Proxy Mobile
IPv6 to enable mobility between access networks.
– An overview of the “off-path” QoS model to supplement
PMIPv6 is also provided.
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Network-Based IP Mobility Management
• IP-based mobility management
– enables the UE (user equipment) to preserve IP address (referred
to as home address), even when the UE changes its point of
attachment.
• Two basic approaches
– Network-based mobility management and
– client-based mobility management.
• The UE obtains a new local-IP address (referred to as care-of-address) when
it moves to a new point of attachment.
• It is then the responsibility of the UE to update its home agent,
– which maintains a binding between the care-of-address and the home
address of the UE.
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• Network-based mobility management
– the network (e.g., access gateway), on detecting that the UE has changed
its point of attachment, provides the UE with the same IP address that it
had at its previous point of attachment.
– The network entity providing the IP address to the UE also handles
updating the mobility anchor
– The UE is not aware of the mobility management signaling.
• network-based mobility management fulfills these
requirements well:
– provide handover capability
– Efficient use of wireless resources
– minimize UE involvement
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Network-Based IP Mobility Management
(cont.)
• PMIPv6 was adopted as the IP mobility protocol for
mobility between 3GPP and non-3GPP accesses
– and as an option for intra-3GPP access mobility.
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Proxy Mobile IPv6 (PMIPv6)
• Mobile IPv6 requires client functionality in the IPv6 stack
of a mobile node.
– Host-based
• Network-based mobility is another approach to solving
the IP mobility challenge.
• Per-MN-Prefix model
– an addressing model where there is a unique network prefix or
prefixes assigned for each node.
S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury, and B. Patil, "Proxy Mobile IPv6," IETF, RFC 5213, 2008.
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• Local Mobility Anchor (LMA)
– has the functional capabilities of a MIPv6 home agent as with
the additional capabilities
– the topological anchor point for the MN’s “home network”
prefix(es) in a PMIPv6 domain
• Mobile Access Gateway (MAG)
– a function on an access router
– tracks the MN’s movements
– manages the mobility signaling on behalf of an MN
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Initiation
wide area
network
Proxy Binding Ack.:
with a home prefix
for the MN
(e.g., 1400:0112::1/64)
Proxy Binding Update:
with MN-ID and
the address of MAG1
correspondent node
home
domain
LMA
home domain
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(e.g., 1400:0112::0/40)
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MAG2
MAG1
(e.g., proxy-CoA1)
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AP1
1) Unicast Router Advertisement
2) Configure “home address”
(e.g., 1400:0112::1::30)
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AP2
L2 access authentication
with MN-ID
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CommunicationCommunicate with the MN
using the MN’s “home address”
(1400:0112::1::30::MN_MAC)
Downlink :
LMA tunnels packets that
destined to the MN’s
“home address”
to Proxy-CoA1
Uplink:
MAG1 tunnels packets from
the MN to the LMA
wide area
network
correspondent node
home
domain
LMA
home domain
(e.g., 1400:0112::0/40)
MAG1
AP1
MAG2
AP2
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Handover within the Home Domain
wide area
network
Proxy Binding Ack.:
with the same home prefix
for the MN
(i.e., 1400:0112::1/64)
Proxy Binding Update:
with MN-ID and
the address of MAG2
correspondent node
home
domain
LMA
home domain
3
(e.g., 1400:0112::0/40)
2
MAG2
MAG1
(e.g., proxy-CoA2)
AP1
1
4AP2
1) Unicast Router Advertisement
2) use the same “home address”
L2 access
(e.g., 1400:0112::1::30)
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authentication
Communication-2
Communicate with the MN
using the MN’s “home address”
(1400:0112::1::30::MN_MAC)
wide area
network
correspondent node
home
domain
LMA
home domain
(e.g., 1400:0112::0/40)
MAG1
AP1
MAG2
AP2
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Network-Based Mobility Architecture of
the Evolved Packet Core (EPC) - PMIP
Home Public Land
Mobile Network
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Key requirements and impacts
• Support of IPv4 UE:
– The EPC requires support for IPv4 only, IPv6 only, and dual stack hosts.
• Simultaneous access to multiple Packet Data Networks:
– An access point name (APN) is used to identify a PDN.
• Included in the PMIPv6 proxy binding update (PBU)
• the PDN GW (LMA) assign an IP address to the UE from the appropriate PDN.
• Support for overlapping address spaces of different PDNs:
– for example, the use of private address spaces.
– the generic routing encapsulation (GRE) key extensions for tunneling
packets between the LMA and MAG PMIPv6 are employed.
• enables the network to disambiguate traffic related to different PDNs based
on the GRE.
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• Unique UE identification across
accesses on EPC PMIPv6 interfaces:
– an international mobile subscriber identity (IMSI)-based networkaccess identifier (NAI),
• the IMSI is the identity that currently is used to identify the UE in
GSM/UMTS networks
– non-3GPP accesses must obtain the IMSI of the UE during access
authentication (either from the UE or from the HSS/AAA) and use the IMSIbased NAI on the PMIPv6 interfaces.
• Providing a PDN GW address to the target access:
– The EPC support multiple PDN GWs serving the same PDN
– the PDN GW identity along with the corresponding APN is stored in
the HSS/AAA
• provided to the MAG in the target access during authentication.
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Network-Based Mobility Architecture of
the Evolved Packet Core (EPC) - PCC
• The objective of the Policy and Charging Control (PCC)
architecture
– to provide QoS for IP-based service data flows
– to charge for the resources
• provided based on the user’s subscription and other policy related to the
access, network, and service.
• To not overload PMIPv6 signaling with QoS and PCC
aspects, an “off-path” PCC model was developed
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Policy and Charging Rules
Function :
makes policy decisions for a UE
and provides charging and QoS
rules to the Policy and Charging
Enforcement Function and QoS
rules to the Bearer Binding and
Event Reporting Function for
enforcement.
Policy and Charging Control
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Network-Based Mobility Architecture of
the Evolved Packet Core (EPC) - AAA
Authentication, Authorization and Accounting
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• The QoS information with the associated IP-flow
description also must be provided to the access network
– through the S-GW or A-GW node
• the off-path paradigm relies on the signaling of QoS
information off-the-bearer-path from the PCRF directly to
the access network.
– the PMIPv6 protocol is used only for mobility management and
has no notion of QoS tunnels.
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Inter-Access System Mobility
• Non-optimized handovers
– cover a situation where the source network is not involved in
preparing resources in the target network.
• Optimized handovers
– typically used when the UE is UNABLE to transmit and receive in
both the source and target networks simultaneously.
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Call setup
UE attachment
Non-Optimized Handovers
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UE discovering
and handing over
Non-Optimized Handovers
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• For dual-radio-capable UEs, where the radios of both access
technologies can transmit and receive packets simultaneously, nonoptimized handovers can provide a seamless handover
experience to the end user.
– A “make-before-break” can be achieved
• for single-radio terminals it would lead to substantial
interruption time during inter-technology handovers.
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Optimized Handovers
LTE
CDMA2000
evolved-High Rate Packet Data
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Pre-registration
Optimized Handovers
‧The purpose of pre-registration is to avoid lengthy delays
‧pre-registration can take several seconds
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Exeecuration Preparation
Optimized Handovers
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• Release 8 of the EPC standard only defines optimized
handover between eHRPD and E-UTRAN.
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Summary and Future Work
• This article presented the motivation, design, and
realization of inter-access system mobility support based
on Proxy Mobile IPv6 for the 3GPP EPC,
– enabling a common packet core to be used for access
technologies.
• The document also addresses the issues of QoS
provisioning and seamless handover support.
• Detailed flows illustrating the use of PMIPv6 to achieve
– non-optimized handovers between 3GPP accesses and other
non-3GPP accesses, as well as
– optimized handovers between E-UTRAN and eHRPD were
provided.
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• Release 8 is the first release of the EPC specification
• additional work is required to enhance and adapt the
new system
– For instance, further study is required to determine
• how to support the UE to access the EPC through multiple-access
networks simultaneously
• while providing mobility management and controlling the routing of
individual IP flows between the different radio interfaces.
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