Network-Based Mobility Management in the Evolved 3GPP Core Network 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

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

Introduction The Evolved Packet Core (EPC) of 3GPP system supports multiple access networks one common packet core network for 3GPP radio accesses (E-UTRAN, 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

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.

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.

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

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.

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.

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

Initiation wide area network correspondent node Proxy Binding Ack.: with a home prefix for the MN (e.g., 1400:0112::1/64) home domain LMA home domain (e.g., 1400:0112::0/40) 3 2 Proxy Binding Update: with MN-ID and the address of MAG1 (e.g., proxy-CoA1) MAG2 MAG1 4 1 AP2 1) Unicast Router Advertisement 2) Configure “home address” (e.g., 1400:0112::1::30) AP1 L2 access authentication with MN-ID

Communication Communicate 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 data packets correspondent node home domain LMA home domain (e.g., 1400:0112::0/40) MAG2 MAG1 AP2 AP1

Handover within the Home Domain wide area network data packets correspondent node Proxy Binding Ack.: with the same home prefix for the MN (i.e., 1400:0112::1/64) home domain LMA home domain (e.g., 1400:0112::0/40) 3 2 Proxy Binding Update: with MN-ID and the address of MAG2 (e.g., proxy-CoA2) MAG2 MAG1 1 4 AP2 AP1 1) Unicast Router Advertisement 2) use the same “home address” (e.g., 1400:0112::1::30) L2 access authentication

Communication-2 home domain 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) MAG2 MAG1 AP2 AP1

Network-Based Mobility Architecture of the Evolved Packet Core (EPC) - PMIP Home Public Land Mobile Network

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.

Unique UE identification across accesses on EPC PMIPv6 interfaces: an international mobile subscriber identity (IMSI)-based network-access 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 IMSI-based 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.

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

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

Network-Based Mobility Architecture of the Evolved Packet Core (EPC) - AAA Authentication, Authorization and Accounting

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.

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.

Non-Optimized Handovers UE attachment Call setup

Non-Optimized Handovers UE discovering and handing over

For dual-radio-capable UEs, where the radios of both access technologies can transmit and receive packets simultaneously, non-optimized 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.

Optimized Handovers LTE CDMA2000 evolved-High Rate Packet Data

Optimized Handovers Pre-registration ‧The purpose of pre-registration is to avoid lengthy delays ‧pre-registration can take several seconds

Optimized Handovers Preparation Exeecuration

Release 8 of the EPC standard only defines optimized handover between eHRPD and E-UTRAN.

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.

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.