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

1. 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. AlessioCasati, Alcatel-Lucent KuntalChowdhury, Starent Networks Katsutoshi Nishida, NTT DoCoMo Inc. Eric Parsons, Nortel Networks Stefan Schmid, NEC Europe Ltd. RahulVaidya, Samsung India Software Operations

2. 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

3. 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

4. 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.

5. 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-basedmobility 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.

6. 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 addressthat 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

7. 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.

8. 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.

9. 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

10. 3 1 4 2 Initiation correspondent node homedomain LMA home domain (e.g., 1400:0112::0/40) wide area network MAG2 MAG1 Proxy Binding Ack.: with a home prefix for the MN(e.g., 1400:0112::1/64) AP2 AP1 L2 access authenticationwith MN-ID Proxy Binding Update: with MN-ID and the address of MAG1 (e.g., proxy-CoA1) 1) Unicast Router Advertisement 2) Configure “home address”(e.g., 1400:0112::1::30)

11. Communication Communicate with the MN using the MN’s “home address” (1400:0112::1::30::MN_MAC) data packets correspondent node homedomain LMA home domain (e.g., 1400:0112::0/40) 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 MAG2 MAG1 AP2 AP1

12. 3 4 1 2 Handover within the Home Domain data packets correspondent node homedomain LMA home domain (e.g., 1400:0112::0/40) wide area network MAG2 MAG1 Proxy Binding Ack.: with the samehome prefix for the MN(i.e., 1400:0112::1/64) AP2 AP1 Proxy Binding Update: with MN-ID and the address of MAG2 (e.g., proxy-CoA2) 1) Unicast Router Advertisement 2) use the same “home address”(e.g., 1400:0112::1::30) L2 access authentication

13. Communication-2 Communicate with the MN using the MN’s “home address” (1400:0112::1::30::MN_MAC) correspondent node homedomain LMA home domain (e.g., 1400:0112::0/40) wide area network MAG2 MAG1 AP2 AP1

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

15. 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.

16. 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.

17. 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 policyrelated to the access, network, and service. • To not overload PMIPv6 signaling with QoS and PCC aspects, an “off-path” PCC model was developed

18. 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 rulesto the Bearer Binding and Event Reporting Function for enforcement. Policy and Charging Control

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

20. 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.

21. 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.

22. Non-Optimized Handovers UE attachment Call setup

23. Non-Optimized Handovers UE discovering and handing over

24. 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.

25. Optimized Handovers LTE CDMA2000 evolved-High Rate Packet Data

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

27. Optimized Handovers Preparation Exeecuration

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

29. Summary and Future Work • This article presented the motivation, design, and realization of inter-access system mobility supportbased 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 handoversbetween E-UTRAN and eHRPD were provided.

30. 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.