IEEE 802.21 MIH based Handover for Next Generation MobileCommunication Systems

Jae-Han Seol and Jong-Moon ChungCommunication & Networking Laboratory (CNL)School ofElectrical & Electronic Engineering

Yonsei UniversityShinchon-Dong 134, Seodaemun-GuSeoul 120-749, Republic ofKorea

{hseol, jmc} @,yonsei. ac. kr

AbstractThis paper proposes a vertical handover (VHO)

solution between the two emerging future mobilecommunication systems, WiMAX and 3rd generationlong term evolution (3G-LTE)/system architectureevolution (SAE). Theproposed VHO scheme is based onIEEE 802.21 media independent handover functions(MIHFs) and new network entities for network basedmobility management scheme in the course of MIPsignaling.

1. Introduction

In this paper, a novel VHO solution between the twoemerging future mobile communication systems,WiMAX and 3G-LTE/SAE is presented based on IEEE802.21 MVIHFs. For fast VHO between 3G-LTE andWiMAX networks, many issues need to be solved.Some of the issues include mobility managementschemes, home agent (HA) registration procedures ofmobile nodes (MNs), interoperability between IPv4 andIPv6 systems, seamless adaptation to different IPversions of the network, to name a few. Other issuesinclude interoperable interfacing operations, linkconnection setup between heterogeneous networkprotocols, addition and location of new entities fortunneling of VHO signaling messages, mapping ofheterogeneous signaling messages depends on eachsystem using the combination of existed and new

entities. To resolve these issues, a novel mobilitysupport and VHO signaling message mapping schemebetween 3G-LTE/SAE and WiMAX are employed on

the access and connectivity points of the network. Onthe basis of combination of mobile IP (MIP) signalingsetup for network based mobility management andhandover messages, a novel primitive mapping betweenWiMAX and 3G-LTE/SAE, VHO solution isdeveloped.

2. Related works2.1. Setup for network based MIP signaling

Network based mobility management techniques are

capable of supporting mobility to MNs that are not MIPenabled. [1], [2]. For the network based support ofVHObetween 3G-LTE/SAE and WiMAX, proxy foreignagent (P-FA) of 3G-LTE/SAE and proxy mobile IP(PMIP) client ofWiMAX are necessary instead ofthosefunctions implemented on the MN, and thus L3 MIPsignaling is enabled by access routers and the HA. Inaddition, MIUF, MIIS server, and MIH are defined inboth network architectures as well as MIUF on the MNfor the compatibility of signaling messages ofheterogeneous systems. MIHF, therefore, is able tocomplete VHO by tunneling between 3G-LTE/SAE andWiMAX with equalization of layer 2 signalingmessages.

2.2. Primitive mapping principle for VHO

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Figure 1. Key primitive mapping principle forVHO based on MIHF.

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Table 1. MIH_SAP primitives mapping with802.16/WiMAX and 3G-LTE/SAE.

Primitives 802.16/WiMAX 3G-LTE/SAE

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M Neighbor Preparation(SM:System Management) Request

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MIH Event_Subscribe M Scanning Handover Initiation(C: Command)

MIH_Event_Unsubscribe (C) M_Scanning Handover Initiation

MIH Link Up (E: Event) M Registration CompleteHandovere

MIH Link Down (E) M Registration Complete ACK

MIH_Link_Going_Down (E) M_Registration Resource Release

MIH_Link_Event_Rollback M Registration Handover Required(E)

MIH_Link Detected (E) M ScanReport Handover InitiationMIH_Link_Parameters M ScanReport Handover Required

Report (E)MIH_Link_PDU_Transmit M ScanReport Handover Required

Status (E)MIH_Link Handover_ M-HOIND.Reques Handover Required

Imminent (E) t/ConformationMIH_Link Handover_ M-HOIND.Reques Handover

Complete (E) t/Conformation Complete

MIH Get Status (C) M Ranging HandoverHomandoe

MIH Switch (C) M Ranging HandoverHomandoe

MIH Configure (C) M Management HandoverHandover

MIH_Scan (C) M_Scanning PreparationRequest/Confirm

MIH Net HO Candidate HandoverQuery (C) - M_MACHandover Request/Confirm

MIH MN HO Candidate HandoverM MACHandover Preparation

Commit (C) tCnomto omn

Quemit (C) t/Conf n Request/ConfirmMIH_MN_NHO_Completery (C)M_MAHandover HandoverMIH_N2N_HO_CQuplete M MACHandover PreparationResources(C) ~~~Request/ConfirmMIH_NetwHOrCandidate M-HOINDReques Handover

Commit (C) t/Conformation CommandMIH_MNeHO_ Candidate MHOIND .Reques Handover

Commit (C) t/Conformation CommandMIH MN HO Complete (C) M MACHandover Handover

Comiplete/ACKMIH N2N HO_Complete M ACadvr Handover

(C) MM CadvrComplete/ ACKMIH Network Address MNiho Handover

Information (C) M egbr Command

MIH Get Information ~HandoverMI Ge nomto M ScanScheduling Preparation(I: Information)Reus

The primitive mapping principle for seamless VHOoperation can be explained in three steps. First, thesituation that requires signaling between other networksin order to build up the handover procedure should beconsidered. Second, messages that correspond to othernetworks, but have the same meaning in spite of thedifference of network architecture should be found outand categorized. Third, messages that could berepresented in the format of IEEE 802.21 's standard forlinking other networks should be defined and created.Using this principle, the key primitive mappingprinciple between WiMAX/IEEE 802.16, 3G-LTE/SAE,and NIHF is shovn in Figure 1. In WiMAX view, the (a)M_MACHandover.request and (b)M_MACHandover.response message, both of whichindicate the network decision to initiate handover to thetarget network, could be mapped to the (f)MIH Handover_Initiation.request and (g)MIH Handover_Initiation.res-ponse message of IEEE802.21, respectively. In primitive (h), the servingnetwork sends the MIH Handover_Commit.requestmessage to the UE/MS when the network receives the(g) MIH Handover_Initiation.response mes-sage inorder to command the UE/MS to set up a wireless linkin a foreign target network. This message could bemapped to the (c) M HOIND.request message ofWiMAX. Next, ifthe wireless link is set up, the UE/MSsends the (i) MIH Handover_Commit.responsemessage to the serving network. This message could bemapped to the (d) M HOIND.response message ofWiMAX. The serving network could release networkresources and the target network could provide theconnectivity service to the UE/MS. After the UE/MSreleases the radio resource of the source network, theUE/MS sends the (j)MIH_Handover_Complete.response message. Thismessage does not directly match to a message ofWiMAX, but the (e) M Registration.response messageof WiMAX works the similar function. As the sameprocess of WiMAX, primitive mapping procedurebetween 3G-LTE/SAE and MIH is conducted as shownin 3G-LTE/SAE view of Figure 1. Based on this keyprimitive mapping, MIH SAP primitives mapping withIEEE 802.16 and 3G-LTE/SAE is shown in Table 1 [3],[4], [5].

3. Novel vertical handover solution

Complete solution for inter VHO between WiMAXand 3G-LTE/SAE is obtained according to acombination of MIP signaling setup for network basedmobility management and the handover message,primitive mapping is applied into the handover process.IEEE 802.21 is intended to reuse dependent service

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access points (SAPs) and existing infrastructure. In thispaper, therefore, WiMAX and 3G-LTE/SAEprocedures are unchanged as much as possible. In orderto achieve this, our key idea is that the proxy FA /proxymobility management entity /Serving Gateway(P-FA/MME/S-GW) function and MIUF are added tothe process data network (PDN) Gateway of the SAEnetwork. The P-FA/MME/S-GW performs as if it is thetarget FA to the WiMAX network and servingMME/S-GW to the SAE network.

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Figure 2. Proposed VHO route betweenWiMAX and 3G-LTE/SAE based on MIHF.

Figure 2 shows the proposed inter VHO routebetween WiMAX and 3G-LTE/SAE based on MIHIF[6]. Based on the existing WiMAX and 3G-LTE/SAEnetwork architecture, the main different points thatshould be highlighted are described as follows: PDNGateway (which serves the role as the HA) has aconnection S2a to the connectivity service network(CSN). Reference point S8a is established so as toconnect the S-GW in 3G-LTE/SAE network. Based onthese connections, new functional entities areestablished in the PDN Gateway in 3G-LTE/SAEnetwork. One is the P-FA/MME/S-GW, and another isthe MIUF. Likewise, the HA and MIIS Server areincluded in the CSN of the WiMAX network. PMIPClient, FA, and MIUF reside on the ASN of theWiMAX network. By means of the link connectionsetup and new functional entities added, the VHO routebetween WiMAX and 3G-LTE/SAE could becompleted. Based on the principle of newly proposedVHO the complete solution for inter VHO fromWiMAX to SAE/LTE is illustrated in Figure 3. TheFigure 3 presents the MIH solution of inter VHObetween WiMAX and 3G-LTE/SAE based on IEEE802.21. The MIH functions and messages between3G-LTE/SAE and WiMAX networks were mappedconsidering the two networks at equal levels. Thismeans that it is assumed that a network's core is notincluded in the other network structure, thus

constituting flat interconnected network architecture.Due to the flat and equivalent level structure, it isassumed in the proposed VHO model that each networkhas its own authentication, authorization, accounting(AAA) server and other connectivity service entities(e.g., HA, DHCP server, policy rules server, etc.) [4].Based on the handover message, primitive mapping ofIEEE 802.21, IEEE 802.16, and 3G-LTE/SAE,seamless VHO solution for inter VHO betweenWiMAX and 3G-LTE/SAE is presented.1. The IP bearer service is established between UE andBS2, BS2 and FA, and also between the FA and the HA.An IEEE 802.21 Link Parameter change event (ES:Event Service) is indicated because of the unstabletraffic flow.2-3. Through MIUF which is located on the WiMAXaccess network, the MIH_Link_Parameters_Report issent to the MIH User within the local network.4. The MIH User transmits the MIH Capability-Discover.request to MIIS Server within the WiMAXCSN.5. The MIH Capability-Discover.response is deliveredfrom the MIIS Server to the MIH User in the WiMAXaccess network.6-8. Through MIUF, which is located on WiMAXAccess network, the MIH Handover_Initiate.request issent to the MIH User within the UE/MS.9-11. The MIH Handover_Initiateresponse iscontinuously transmitted through the MIUF, located inthe UE/MS and WiMAX access network. At this stage,this command service is arrived at the MIH User withinthe WiMAX access network.12-13. The MIH User that has received response for thehandover initialization sends the MIH Handover_Preparation.request to MIUF, located in the WiMAXaccess network. Then, the MIUF forwards theMIH Handover_ Preparation.request to the MIUF,located in the PDN Gateway.14. According to the MIUF within the PDN Gateway,the Handover Required message is transmitted to P-FA(MME/S-GW).15. The P-FA(MME/S-GW) sends HandoverPreparation Request message to target MME/S-GW asif it was serving MME/S-GW.16-19. The steps 16-19 are standard SAE handoverpreparation procedures.20. After the handover preparation procedures arecompleted, the P-FA(MME/S-GW) sends HandoverCommand messages to the MIUF.21-22. Through MIUF, which is located on WiMAXAccess network and PDN Gateway of SAE core, theMIH_ Handover_Preparation.response is sent to theMIH User within the WiMAX Access network.23. The MIH User triggers handover to SAE network.

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24-26. The MIH Handover Commit.request iscontinuously transmitted through the MIUF located inWiMAX and UE/MS access network. At this stage, thiscommand service arrives at the MIH User within theUE/MS.27. The MIH User sends a MIH Handover_Commit.response command to the MIUF.28. After receiving theMIH Handover_Commit.response, the MIUF sends aMIH_Configure command to LTE LI/L2 in order to setup the new radio interface.29. LTE LI/L2 sends MIH Link UP event service to theMIUF when the radio link bearer is established.3 0-32. The MIUF informs to the MIH User that the LTEradio bearer is established, and then, through the MIUF,which is located within UE/MS and WiMAX accessnetwork, the MIH Handover_Commit.response is sentto the MIH User within the WiMAX access network.33. After receiving the MIH Link UP event service, theMIH User starts the network registration to the targetMME/S-GW.34-35. The target MME/S-GW sends the temporaryidentity to the P-FA(MME/S-GW) then, theP-FA(MME/S-GW) transfers the UE context.36. Completing the procedures above, theauthentication procedure is performed between theMIH User and target MME/S-GW, target MME/S-GW,and home subscriber server (HSS) in the SAE corenetwork.37-38. The target MME/S-GW registers the MME to theHSS, then (assuming that all is acceptable) the HSSconfirms the registration.39-41. After the MIH User receives theMIUF_Handover_Commit.reponse, it sendsR3_Relo-cate.Request to the PMIP client and the PMIPclient responds with a R3 Relocate.Confirm. Then, thePMIP client sends a MIP Registration Request to theP-FA(MME/S-GW) because the PMIP client considersthe P-FA as the target FA.42-44. When the P-FA(MME/S-GW) receives the MIPRegistration Request from the PMIP client, theP-FA(MME/S-GW) sends MIP Registration Request tothe HA in the WiMAX CSN. Then, the HA in theWiMAX CSN replies with a MIP Registration Reply,and the P-FA(MME/S-GW) sends a MIP RegistrationReply to the PMIP Client. At this time, the direction oftraffic destined to the UE/MS would be changed to theSAE network.45-47. After the target MME/S-GW receives theRegistration confirm message from the HSS, the targetMME/S-GW sends a PMIP Registration Request to theHA of the SAE network. Then, the HA replies with aPMIP Registration Response. After that, the target

MME/S-GW sends a Network Registration Confirmmessage to the MIH User.48. When the PMIP client receives the MIP RegistrationReply, it sends R3_Relocate.Response to theMIH User.49-50. According to the MIUF within the WiMAXaccess network and UE/MS, theMIH-Handover_Complete.request is transmitted to theMIH User in the UE/MS.51. The MIH User determines the radio interfaceswitching to LTE LI/L2 and sends the MIHSwitch.request command to the MIUF.52. When the MIUF receives the MIH Switch.request,the MIUF sends a MIH Handover_Complete.responseto the MIH User through the MIUF located in theWiMAX Access network.53-55. The MIUF sends Link Teardown.request to theIEEE 802.16 radio interface and the IEEE 802.16 radiointerface replies with a Link_Teardown.response. Then,the MIH User in UE/MS receives MIH Switch.responsethough the MIUF. Finally, the new data flow could beestablished [3], [4], [5], [6], [7].

4. Conclusion

This paper presents a novel VHO solution betweenthe two emerging future mobile communicationsystems, WiMAX and 3G-LTE/SAE based on MIHinterface of IEEE 802.21. The key idea behind theproposed solution is to add the P-FA (i.e., proxyMME/S-GW), the MIUF to the PDN Gateway on the3G-LTE/SAE network and the PMIP client, the MIH1Fto the ASN Gateway on the WiMAX network. In orderto provide MIH services, all of the access networksshould have the MIUF and the MIH User. However,dependent SAPs are reused and existing standardprocedures are unchanged as much as possible. It is notonly a very cost-effective solution but also has anadvantage in the aspect of deployment.

5. Acknowledgment

This research was supported by the MIC (Ministry ofInformation and Communication), Korea, under theITRC support program supervised by the IITA(IITA-2007-C 1090-0701-0038).

6. References

[1] R. Koodli, Ed., "Fast Handovers for Mobile IPv6," RFC4068, IETF, July 2005.

[2] S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury,

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B. Patil, "PMIPv6," IETF, March, 2007.

[3] EEE 802.21/D04.00, "Draft EEE Standard for Local andMetropolitan Area Networks: Media Independent HandoverServices," Draft EEE 802.21, EEE, Feb. 2007.[4] WiMAX Forum, "WiMAX End-to-End Network SystemArchitecture," 060301_NWG_Stage-2, Aug. 1, 2006.[5] 3GPP TR 23.882 v1.9.0 "3GPP System ArchitectureEvolution, Report on Technical Options and Conclusions,"Release 7, 3GPP, Apr. 2007.

[6] 3GPP TS 23.401 vO.4.1 "3GPP System ArchitectureEvolution, GPRS enhancements for E-UTRAN access,"Release 8, 3GPP, Apr. 2007.[7] EEE P802.16g, "Air Interface for Fixed and MobileBroadband Wireless Access Systems," Amendment 3:Management Plane Procedures and Services, EEE, Apr.2007.

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