PATENT ABSTRACT
Methods and mechanisms enhance heterogeneous media independent handover (MIH) between different link layer technologies. Embodiments include using an MIH proxy entity, MIH capable network controller, and an MIH server. Enhancements are made to the query phase, preparation phase, execution phase and completion phase by including required information in MIH messages.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional applications 60/942,364 filed on Jun. 6, 2007, and 60/944,696 filed on Jun. 18, 2007, which are incorporated by reference as if fully set forth. 
     
    
     TECHNOLOGY FIELD 
       [0002]    The subject matter disclosed is related to wireless communications. More particularly, the subject matter is related to supporting media independent handover (MIH). 
       BACKGROUND 
       [0003]    The IEEE 802.21 standard provides a uniform set of functionalities that help enable and enhance handovers across different link layer technologies. IEEE 802.21 defines three main services available to Mobility Management applications, such as Client Mobile Internet Protocol (Client MIP) or Proxy MIP. Referring to  FIG. 1 , these services are the Event Service  100 , the Information Service  105  and the Command Service  110 . These services aid in the management of handover operations, system discovery and system selection by providing information and triggers from lower layers  115  to upper layers  120  via a media independent handover (MIH) function (MIHF)  125 . 
         [0004]    At a high level, this involves an upper layer MIH User which can communicate with an MIH Function  125  (either locally or remotely over some transport medium) through link-independent Event Service  100 , Information Service  105  and Command Service  110 . The MIH Function  125 , in turn, will interact with link-layer devices through the use technology-specific primitives; the functionalities expected from these technology-specific primitives are defined in the 802.21 standard. While  FIG. 1  shows MIHF  125  as a middle layer in a protocol stack, MIHF  125  may also be implemented as an MIH plane that is capable of exchanging information and triggers directly with different layers of the protocol stack. 
         [0005]    The Third Generation Partnership Project (3GPP) has identified three principles that describe how inter-system handovers between 3GPP and non-3GPP access (e.g. 3GPP2, IEEE 802.11 WLAN, IEEE 802.16 WiMAX, etc.) should be handled. However, these principles do not address how two different accesses can be integrated in order to allow handover execution. The first principle applies in multiple RAT scenarios where the wireless transmit/receive unit (WTRU) uses a single radio access technology (RAT) for all in-progress services. The second principle is that the Inter-RAT handover decision is made and the handover command is sent by the serving Radio Access Network (RAN). The target RAN may exercise admission control to the WTRUs that are handed over. The third principle is that the serving RAN receives information from the target RAN that can be included in the handover command. 
         [0006]    All these principles can be met by using the handover (HO) service provided by the 802.21 standard. This is especially needed when handover commands requesting a switch over toward or from a 3GPP based access is required, for example, when a handover takes place between IEEE 802.16 or WiMAX accesses and 3GPP accesses, or between IEEE 802.11 or WLAN systems and 3GPP systems. 
         [0007]      FIG. 2  depicts a typical GSM Edge Radio Access Network—UMTS Terrestrial Radio Access Network (GERAN-UTRAN) 3GPP packet switched (PS-domain) Inter-RAT architecture  200 . Referring to  FIG. 2 , the source network includes a serving GPRS support node SGSN  205 , a base station controller/radio network controller (BSC/RNC)  210 , and a base transceiver station (BTS)/Node B  215 . The BSC/RNC  210  communicates with the SGSN  205  through a Gb/IuPS interface  220 . In addition, the BSC/RNC  210  communicates with the BTS/Node B  215  through an Abis/Iub interface  225 . The target network includes a SGSN  230 , a BSC/RNC  235 , and a BTS/Node B  240 . The BSC/RNC  235  communicates with the SGSN  230  through a Gb/IuPS interface  245 . The BSC/RNC  235  communicates with the BTS/Node B  240  through an Abis/Iub interface  250 . The source and target SGSNs  205 , 230  communicate through a Gn interface  255 . 
         [0008]    Referring to  FIG. 2 , it is the source BSC/RNC  210  that controls the handover. The mobile node (MN)  260  is requested to take measurements in the target network and, upon meeting the handover conditions, the source BSC/RNC  210  requests the target BSC/RNC  235  to prepare the resources for the MN  260 . The target BSC/RNC  235  performs admission control and responds with the new resource allocation. Once the new resources have been allocated, the source BSC/RNC  210  commands the MN  260  to handover to the new network. Upon detecting the MN  260  in the new network, the target BSC/RNC  235  informs the source BSC/RNC  210  of the handover completion. 
         [0009]    In order to perform heterogeneous handover between a 3GPP and non-3GPP network, the network architecture must provide capability for an MIH User to acquire measurement reports and capability for an MIH Function to reserve link layer resources through the use of standardized MIH primitives and messages. While the 802.21 standard provides mechanisms to obtain such measurement reports, query for resources, reserve these resources, execute the handover and inform the peer network about the completion of the action, the mechanisms have deficiencies that deprive implementers from the use of key functionalities and from complete control of the measurement-reporting process. This is specifically true for handover between 3GPP (e.g. GERAN, UTRAN and LTE) and non-3GPP networks, which are also known as Inter-Radio Access Technology (Inter-RAT) handovers. 
         [0010]    When two peer networks are to perform a handover, typically based on Mobile Node (MN) (also referred to as User Equipment or UE) measurement reports, the network instructs the MN to switch to another cell and indicates what configuration to use in the new cell. This implies that the Inter-RAT handover decision is made by the serving Radio Access Network (RAN), whereas the target RAN may exercise admission control on the MN that is being handed over. 
         [0011]    Hence, the sequence of events is 1) a Query phase used to determine the status of resources at both source and target networks before taking a handover decision, 2) a Preparation phase where resources are reserved at the target network once a handover decision has been taken, 3) an Execution phase when the handover commands are sent and performed, and 4) a Completion phase when the result of the handover is informed and the original resources are released. 
         [0012]    The IEEE 802.21 specification defines messages that can be used to perform the actions described above. However, the functionality provided by the currently defined messages is insufficient to convey all the required information between source and target networks, especially in the case of 3GPP to non-3GPP handover (and vice versa). It would therefore be desirable to provide messages to convey all the required information between source and target networks without compromising functionality. In order to perform heterogeneous handover between a 3GPP and non-3GPP network, it would also be desirable to design a network architecture to provide capability for an MIH User to acquire measurement reports and capability for an MIH Function to reserve link layer resources through the use of standardized MIH primitives and messages. 
       SUMMARY 
       [0013]    A method and apparatus for access-independent mobility management. The method and apparatus are used in handover between 3GPP and non-3GPP networks which use enhanced media independent handover functionalities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    A more detailed understanding may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein: 
           [0015]      FIG. 1  is an IEEE 802.21 protocol architecture according to the prior art; 
           [0016]      FIG. 2  is a block diagram for a 3GPP PS-domain Inter-RAT architecture according to the prior art; 
           [0017]      FIG. 3  is a block diagram of a system performing Inter-RAT Handover with a Proxy MIH Node; 
           [0018]      FIG. 4  is a block diagram of a system performing for an Inter-RAT Handover with an MIH-capable SGSN/Network Controller; 
           [0019]      FIG. 5  is a block diagram of a system performing an Inter-RAT Handover with MIH Server; 
           [0020]      FIG. 6  is a block diagram of a system performing Inter-RAT Handover; 
           [0021]      FIG. 7  is a block diagram of a system using media independent normalizing functions to interpret 3GPP commands and map their functionality into equivalent generic handover commands; 
           [0022]      FIG. 8  is a block diagram of a system using media independent normalizing functions to interpret 3GPP commands and map their functionality into equivalent generic handover commands; 
           [0023]      FIG. 9  shows a block diagram of a roaming scenario where the MN is in a visited network; 
           [0024]      FIG. 10  is a WTRU, Access Point (AP) or Point of Access (PoA) and a Point of Service (PoS) or MIH Server configured to perform heterogeneous handover between a 3GPP and non-3GPP network using MIH messaging; 
           [0025]      FIG. 11  is a signal diagram of a system performing Inter-RAT Handover using media independent normalizing functions; 
           [0026]      FIG. 12  is a signal diagram of a system performing Inter-RAT Handover using media independent normalizing functions and single-radio with on-off techniques; and 
           [0027]      FIG. 13  is a signal diagram of a system performing Inter-RAT Handover using media independent normalizing functions and multi-radio techniques. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, a mobile node (MN), or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, an Enhanced Node-B (eNB), a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment. 
         [0029]    The embodiments below are described in reference to the 802.21 protocol and messages for simplicity. Although the embodiments described below refer to messages defined in the 802.21 protocol, the concepts can be applied messages defined in other technologies containing similar information elements to 802.21 messages. 
         [0030]    IEEE 802.21 services, for example, and in particular Command and Information services, can be used to integrate multiple access technologies. This includes system architecture that show where the Media Independent Handover function can be placed in order to allow this integration. Also included is a mechanism that shows how mobility principles, as outlined by 3GPP standards, can be met using the proposed architecture. Through the use of services provided by the MIH Function, a mobility mechanism supporting Handover between 3GPP and non-3GPP access can be realized. The location of the MIH function within the 3GPP architecture is logically distributed and it might depend on the level of integration that is desired, that is, whether a tight coupling or a loose coupling scenario is being addressed. 
         [0031]    Three logical components, i.e., the MME, the Gateway, and the IP server, can be identified. These logical components can communicate amongst each other or act independently depending on specific deployment scenarios. Logically the MIH function could also reside within a specific access if a particular deployment warrants it. 
         [0032]    The basic functionality for the 3GPP architecture is defined in  FIG. 2  above. Using the basic architecture from  FIG. 2 , the following three network architectures can be derived for the non-3GPP case to support heterogeneous handover. 
         [0033]      FIG. 3  shows one possible architecture  300  that can be used to support the heterogeneous handover between 3GPP and non-3GPP networks. Referring to  FIG. 3 , the source network includes a SGSN  305 , a base station controller/radio network controller (BSC/RNC)  310 , and a BTS/Node B  315 . The BSC/RNC  310  communicates with the SGSN  305  through a Gb/IuPS interface  320 . In addition, the BSC/RNC  310  communicates with the BTS/Node B  315  through an Abis/Iub interface  325 . The target network includes a Generic Network Gateway  330 , a Generic Network Controller  335 , and a Generic Base Station  340 . 
         [0034]    Referring to  FIG. 3 , an 802.21 MIH node  345  is used to translate and act as a proxy between the Generic Network Gateway  330  and the 3GPP SGSN  305 . If a conventional SGSN is used, the handover messages communicated between the MIH Proxy  345  and the SGSN  305  would be the same as described in the 3GPP Gn interface  350 . If the network is small, or the SGSN  305  and BSC/RNC  310  are collocated, the MIH Proxy  345  could connect directly to the BSC/RNC  310  by using Iu messages  355 . 
         [0035]      FIG. 4  shows another possible network architecture  400  to perform an Inter-RAT Handover with MIH-capable SGSN/Network Controller. Referring to  FIG. 4 , it is assumed that the SGSN  410  and Generic Network Gateway  420  implement MIH capabilities  415 , 425 , and therefore are capable of communicating one to another with MIH messages  430 , such as messages defined in the 802.21 protocol or messages defined in other technologies containing similar information elements to 802.21 messages. 
         [0036]    A similar approach could be applied where the Generic Network Controller  435  and BSC/RNC  440  were MIH-capable. For this approach, these two nodes would be able to communicate with MIH messages without passing through the gateways. For simplicity, this approach is not shown in  FIG. 4 . 
         [0037]      FIG. 5  shows an alternative network architecture  500  for an Inter-RAT Handover with MIH Server. In this architecture, the MIH Server  510  acts on behalf of the Network Controller for taking handover decisions (e.g. as source Network Controller) and setting up the resources at the target network. In this figure, it is shown that the MIH Server  510  can communicate to the SGSN  515 , for example, through a Gn interface  520 , and/or to the BSC/RNC  525 , for example, through a Gb/Iu interface  530 . Also in this figure, the MIH Server  510  communicates directly to the mobile Node (MN)  535  via L2/L3 protocols (e.g. 802.11, 802.16, IP, etc.)  540 . 
         [0038]    In order to support heterogeneous handover between a 3GPP and a non-3GPP network, media independent handover messages can be used. For instance, the existing 802.21 standard messages or other technologies standards can be updated to include the following messages:
       MIH_N2N_HO_Commit request; and   MIH_N2N_HO_Commit response.       
 
         [0041]    By including these two messages, the MIH network functionality (or similar network functionality) has the capability to reserve resources when two networks control the handover, similar to the 3GPP networks. 
         [0042]    Although the 802.21 standard, for example, can be updated to include the required messages, the contents of these messages do not fulfill the requirements of the 3GPP network handover. Hence, an enhancement to the MIH messages is required to support handovers between 3GPP and non-3GPP networks. This enhancement would follow the Inter-RAT Handover (GERAN/UTRAN) philosophy described in the background section above. 
         [0043]    The enhanced messages and their encoding, e.g., TLV IEs (Type-Length-Value Information Elements), are discussed in the embodiments below. Where the networks are not pre-configured with each other&#39;s parameters, the source network can request the target network about the available resources (e.g. cell list, cell parameters, etc.). For this, the source network can either ask the target to report on all available resources, or on a specific type of network. 
         [0044]    In one embodiment, this information could be included in the following MIH Messages:
       N2N Query Resources Request (from source to target network to request reporting on available resources that could be used by the source to handover).   MN HO Query Request (from mobile to target network to request reporting on available resources that could be used by the source to handover).       
 
         [0047]    One possibility is to use the Network Type element to request information about a specific network. Another possibility is to include the network information as part of the Available Resource field of the above mentioned message as a suggestion from the source. 
         [0048]      FIG. 6  shows how the updated handover messages can be used to perform an Inter-RAT Handover  600 . Before the handover process starts, it is required for the WTRU to start searching neighboring cells  605  and provide measurements. In order to perform such measurements for 3GPP GERAN/UTRAN/LTE or non-3GPP networks, neighbor list and measurement information is required by WTRU to take measurements on neighbor cells. Thresholds and event criteria (i.e., when to report measurements), periodicity of measurements, and number of cells to report can optionally be included in this information. 
         [0049]    In one embodiment, the information required for 3GPP GERAN/UTRAN/LTE or non-3GPP networks could be included in the following enhanced MIH Messages:
       N2N Query Resources Response (from target to source network to inform the available cells that should be scanned in the network);   Net HO Query Request (from source network controller to MN to let the MN know which cells to monitor); and   MIH Scan Request (from source network controller to MN to let the MN know which cells to monitor).       
 
         [0053]    One possibility is to include the information as part of the Available Resource field of the above mentioned enhanced messages. 
         [0054]    Referring to  FIG. 6 , when MIH server requests reports  610 , or the WTRU independently triggers a measurement report  605 , the required information, such as the cell ID of the best cell or list of best cells, could be included in the following enhanced MIH Messages:
       Link Parameter Report (from MN to the network to report on measurements);   Net HO Query Response (from MN to the network to respond to the query request and report on measurements); and   MIH Scan Response (from MN to the network to respond to the request and report on measurements).       
 
         [0058]    One possibility is to include the information as part of the Link Parameters, Link Resource, or Scan Response fields of the above mentioned enhanced messages. 
         [0059]    Referring to  FIG. 6 , upon receiving a measurement report, the MIH server performs reservation of resources for the target cell  615 . To perform a reservation, the MIH can communicate directly to the target SGSN or mobility management entity (MME)  620  or alternatively to the eNB, RNC or MSC  625  by making use of existing handover messages, such as “Prepare Handover”. 
         [0060]    The required information to reserve resources on the target network could be included in the following enhanced MIH Messages:
       N2N HO Commit Request (from source to target network to request reservation of the resources); and   MN HO Commit Request (from MN to network to request reservation of the resources).       
 
         [0063]    This information could, in one embodiment, be included in the Query Resource, or Reserve Resource fields of the above mentioned enhanced messages. 
         [0064]    Referring to  FIG. 6 , once the resources have been reserved by the target network  630 , the source network (or WTRU) is informed about the successful reservation of resources  635  so that the handover can take place. Hence, the information required by the MN to make the connection to the new network could be included in the following updated MIH Messages:
       N2N HO Commit Response (from target to source network to report reservation of the resources);   MN HO Commit Response (from network to MN to report reservation of the resources); and   Net HO Commit Request (from the network to the MN to report reservation of resources and command the MN to handover to these resources).       
 
         [0068]    This information could, in one embodiment, be included in the Query Resource, or Reserve Resource fields of the above mentioned messages. 
         [0069]    Referring to  FIG. 6 , once the reservation of resources is complete, the handover information is sent to the MN or WTRU  640  in order to perform handover to the target network  645 . Once the handover is complete, handover complete messages can be sent  650  to re-route traffic through the new network and release resources from the source network. 
         [0070]    Depending on the type of network, the handover can be performed in a variety of ways. For GSM, once the BSC has reserved the radio resources of GERAN cell resources it has to give the necessary information for the WTRU to complete the handover and synchronize to the new cell. This information is transmitted to the WTRU via the source network in a transparent container. Such type of transparent container can be used in other types of network to convey the information of the radio resources either from source to target or vice versa. 
         [0071]    The following information for the WTRU, transmitted in a transparent container, could be contained in the MIH message:
       Synchronization Indication (SI);   Normal Cell Indication (NCI);   ARFCN, BSIC-BCCH frequency and BSIC of new cell;   CCN Support Description;   Frequency parameters;   Extended dynamic allocation;   Network Control Order;   RLC reset;   Packet timing Advance;   UL control timeslot;   GPRS, EGPRS mode; and   UL/DL TBFs (PFI, TFI assignment, TBF timeslot allocation, RLC mode, USF allocation);   Optional:   NAS container.       
 
         [0086]    For UTRAN, once the RNC has reserved the radio resources for the cell id, it has to give the necessary information for the Mobile station to complete the handover and synchronize to the new cell. This information is transmitted to the WTRU via the source network in a transparent container. 
         [0087]    The following information, transmitted in a transparent container in a MIH message, is required by the WTRU to make the connection to the 3G cell:
       WTRU identities (U-RNTI, H-RNTI, E-RNTI);   Ciphering algorithm;   RB information elements (SRB information to setup list, RAB information to setup list);   UL/DL transport channel information (UL/DL Transport channel information common for all transport channels, Added or Reconfigured TrCH information UL/DL);   UL radio resources (Uplink DPCH info, E-DCH Info);   DL radio resources (Downlink HS-PDSCH Information, Downlink information per radio link, Downlink information common for all radio links);   Frequency info; and   Maximum allowed UL tx power.       
 
         [0096]    In addition, the RNC may provide information for Commit time/activation for synchronous handovers. 
         [0097]    Alternatively, predefined configurations can be used if the WTRU supports them. A predefined configuration will require less information to be transmitted to the WTRU:
       Default configuration mode (FDD, TDD);   Default configuration identity;   RAB info; and   UL DPCH info.       
 
         [0102]    The RNC may also provide MIH Complete Request/Response Messages. Once the MN has been handed over from the source to the target network, handover complete messages are sent to re-route traffic through the new network and release resources from the source network. 
         [0103]    In one embodiment, this information could be included in the following enhanced MIH Messages:
       Net HO Commit Response;   N2N Complete Request; and   N2N Complete Response.       
 
         [0107]    For LTE and other 3GPP technologies such as WCDMA and GERAN media independent normalizing functions can be used to interpret 3GPP commands and map their functionality into equivalent generic handover commands, such as the ones described in IEEE 802.21.  FIGS. 7 ,  8  and  9  show how this media independent handover function can be logically placed, for example, within the PDN Gateway  710  as this is the central point of contact across multiple access systems. The 3GPP network  715  shown in  FIG. 7  includes an MME  720  capable of supporting E-UTRAN  720  communications. The MME  720  is also in communication with a 2G/3G SGSN  725 , which is capable of supporting UTRAN  730  and GERAN  735  communications. The non-3GPP network  740  includes an ePDG  745  capable of supporting untrusted non-3GPP access  750 . The trusted non-3GPP access  755  is in direct communication with the PDN Gateway  710 . 
         [0108]    As described in  FIG. 8 , the WTRU  805  remains under the domain of 3GPP handover mechanism while the current connection is progress. The Target MIH PoS PDN Gateway  810  serves as the central point of contact between the 3GPP  815  and non-3GPP networks  820 . The source SGSN/MME  825  can use Forward_Relocation_Req  830  and Forward_Relocation_Complete 835 messages to communicate with the Target MIH PoS PDN Gateway  810 . The Trusted Non-3GPP Access  840  can use MIH_N2N_HO_CandidateQuery/MIH_N2N_HO_Commit request  845  and MIH_N2N_HO_Candidate_Query/MIH_N2N_HO_Commit response  850  messages to communicate with the Target MIH PoS PDN Gateway  810 . Similarly, the MN can use HO Commit and Query request and response types of messages to trigger or initiate the handover and to obtain the required information for handover once the preparation is finished. 
         [0109]      FIG. 9  shows an example of a roaming scenario  900  where the MN  905  is in a visited network  910 . In this scenario, there are two gateways in which the MIH  915  could reside, the Serving Gateway  920  and the Anchor Gateway  930 . This scenario may also include an IP server  940  which can communicate with the MN  905 , for example using an IP interface. The MIH functionality  915  may also be located in the MME  950 . This example is also be applicable to the home scenario. In an alternative embodiment, the MIH  915  may be located in E-UTRAN  960 . 
         [0110]    The WTRU may or may not be able to simultaneously support multi radio capabilities or only one radio technology at time. If multiple radio capabilities are supported either by using multi-radio or single-radio with on-off techniques, the WTRU might be able to measure radio environments from multiple accesses while still connected to the current access. Normalized measurement reporting capabilities, such as the ones described in 802.21, could be used to provide a service access point for measurement collection purposes, exposing a unified interface regardless of the underlying technology. 
         [0111]    The WTRU might also rely on information provided via higher layers over the current access by using information services such as the ones provided by IEEE 802.21. This information allows the WTRU to request access relocation, even when no specific measurements are provided. 
         [0112]    When preparing and reserving radio resources, the MIH Function is able to map the relocation request to a suitable MIH Command. This allows the target access system to exercise admission control functions prior to granting resources. The command that triggers the handover from the 3GPP access is generated entirely according to 3GPP specifications, possibly using information provided by the target access system via MIH mapping. 
         [0113]    Table 1 below shows a possible mapping between the MIH, e.g., enhanced 802.21, and 3GPP GERAN/UTRAN/LTE messages that could be used, for instance, by the proxy function. 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 Air 
                 LTE 
               
               
                 802.21 
                 Gn 
                 Iu 
                 Gb 
                 Interface 
                 (S11/S3/S4) 
               
               
                   
               
             
             
               
                 N2N Commit 
                 Forward 
                 Relocation 
                 PS 
                   
                 Forward 
               
               
                 Request 
                 Relocation 
                 Request 
                 Handover 
                   
                 Relocation 
               
               
                   
                 Request 
                   
                 Required 
                   
                 Request 
               
               
                 N2N Commit 
                 Forward 
                 Relocation 
                 PS 
                   
                 Forward 
               
               
                 Response 
                 Relocation 
                 Request 
                 Handover 
                   
                 Relocation 
               
               
                   
                 Response 
                 Ack 
                 Required 
                   
                 Response 
               
               
                   
                   
                   
                 Ack 
               
               
                 Net HO Commit 
                   
                   
                   
                 PS 
                 PS HO 
               
               
                 Request 
                   
                   
                   
                 Handover 
                 Command 
               
               
                   
                   
                   
                   
                 Command 
               
               
                 Net HO Commit 
                   
                   
                   
                 HO to 
                 HO to E- 
               
               
                 Response 
                   
                   
                   
                 UTRAN 
                 UTRAN 
               
               
                   
                   
                   
                   
                 Complete 
                 Complete 
               
               
                 N2N HO Complete 
                 Forward 
                 Relocation 
                   
                   
                 Forward 
               
               
                 Request 
                 Relocation 
                 Complete 
                   
                   
                 Relocation 
               
               
                   
                 Complete 
                   
                   
                   
                 Complete 
               
               
                 N2N HO Complete 
                 Forward 
                   
                   
                   
                 Forward 
               
               
                 Response 
                 Relocation 
                   
                   
                   
                 Relocation 
               
               
                   
                 Complete 
                   
                   
                   
                 Complete 
               
               
                   
                 Ack 
                   
                   
                   
                 ACK 
               
               
                 N2N Commit 
                   
                   
                   
                   
                 Update 
               
               
                 Request 
                   
                   
                   
                   
                 Bearer 
               
               
                   
                   
                   
                   
                   
                 Request 
               
               
                 N2N Commit 
                   
                   
                   
                   
                 Update 
               
               
                 Response 
                   
                   
                   
                   
                 Bearer 
               
               
                   
                   
                   
                   
                   
                 Response 
               
               
                 N2N Commit 
                   
                   
                   
                   
                 Forward 
               
               
                 Request 
                   
                   
                   
                   
                 SRNS 
               
               
                   
                   
                   
                   
                   
                 Context 
               
               
                 N2N Commit 
                   
                   
                   
                   
                 Forward 
               
               
                 Response 
                   
                   
                   
                   
                 SRNS 
               
               
                   
                   
                   
                   
                   
                 Context 
               
               
                   
                   
                   
                   
                   
                 ACK 
               
               
                 N2N_HO_Candidate —   
                   
                   
                   
                   
                 Forward 
               
               
                 Query Request 
                   
                   
                   
                   
                 Relocation 
               
               
                   
                   
                   
                   
                   
                 Request 
               
               
                 N2N_HO_Candidate —   
                   
                   
                   
                   
                 Forward 
               
               
                 Query 
                   
                   
                   
                   
                 Relocation 
               
               
                 Response 
                   
                   
                   
                   
                 Response 
               
               
                 N2N HO Complete 
                   
                   
                   
                   
                 Update 
               
               
                 Request 
                   
                   
                   
                   
                 Bearer 
               
               
                   
                   
                   
                   
                   
                 Request 
               
               
                 N2N HO Complete 
                   
                   
                   
                   
                 Update 
               
               
                 Response 
                   
                   
                   
                   
                 Bearer 
               
               
                   
                   
                   
                   
                   
                 Response 
               
               
                   
               
             
          
         
       
     
         [0114]    Tables 2-5 below show a possible realization combination of the message encoding that would carry the above mentioned parameters in a type-length-value (TLV) format. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 System Parameters List 
               
             
          
           
               
                   
                 Type 
                 Length 
                 Value 
               
               
                   
                   
               
               
                   
                 XXX 
                 Variable 
                 Structure consisting of 1) Network Type, 
               
               
                   
                   
                   
                 and 2) Network Specific System 
               
               
                   
                   
                   
                 Parameters 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Network Type 
               
             
          
           
               
                   
                 Type 
                 Length 
                 Value 
               
               
                   
                   
               
               
                   
                 XXX 
                 8 
                 Network Type and Revision as defined in 
               
               
                   
                   
                   
                 802.21 standard 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Network Specific Parameters 
               
             
          
           
               
                   
                 Type 
                 Length 
                 Value 
               
               
                   
                   
               
               
                   
                 XXX 
                 Variable 
                 Network Specific System Parameters. 
               
               
                   
                   
                   
                 802.16: 
               
               
                   
                   
                   
                 UCD, DCD, UIUC, DIUC 
               
               
                   
                   
                   
                 GSM/GRPS/EDGE (GERAN): 
               
               
                   
                   
                   
                 (defined depending on message type) 
               
               
                   
                   
                   
                 3GPP (UTRAN): 
               
               
                   
                   
                   
                 (defined depending on message type) 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 HANDOVER COMPLETION 
               
             
          
           
               
                 Type 
                 Length 
                 Value 
               
               
                   
               
               
                 XXX 
                 Variable 
                   
               
               
                 Parameter 
                 Integer 
                 Type of network 
               
               
                 type 
                   
                 0: IEEE 802.16 
               
               
                   
                   
                 1: GERAN 
               
               
                   
                   
                 2: 3GPP 
               
               
                   
                   
                 3-7: Reserved 
               
               
                 System 
                 Variable 
                 Depending on the parameter type 
               
               
                 parameter 
                   
                 0: UCD, DCD, UIUC, DIUC 
               
               
                 Value 
                   
                 1: (defined depending on message type) 
               
               
                   
                   
                 2: (defined depending on message type) 
               
               
                   
                   
                 3-255: Reserved 
               
               
                   
               
             
          
         
       
     
         [0115]      FIG. 10  is a WTRU  1000  and access point  1005  configured to implement the IEEE 802.21 Inter-RAT Handover as described above. WTRU  1000  includes a processor  1010 , an MIH function  1015 , and a plurality of transceivers  1020   a  . . .  1020   n , each configured to operate using a different radio access technology and protocol. The processor  1010  and MIH function  1015  are configured to operate protocol stacks according to the above described embodiments. Further, the Processor  1010  and MIH function  1015  are capable of generating enhanced messages as described above, for example, with reference to  FIG. 8 . The processor  1010  and MIH function  1015  are further configured to implement IEEE 802.21 protocols for MIH peer messaging. The IEEE 802.21 messages may be transmitted to MIH peers via any of the plurality of transceivers  1020   a  . . .  1020   n . The processor  1010  and MIH function  1015  are further configured to implement local IEEE 802.21, for example for the IEEE 802.21 Command service. The transformation of MIH messages, and the extraction of MIH messages from received messages may be performed by either processor  1010  or MIH function  1015 , or by a combination of the two. 
         [0116]    Access point  1005  includes a processor  1025 , an MIH function  1030 , and a transceiver  1035 . The access point  1005  communicates with WTRU  1000  via air interface  1040 . The processor  1025  of the access point  1005  processes received IEEE 802.21 messages received from WTRU  1000  via transceiver  1035 . The processor  1025  and MIH function  1030  of the access point  1005  are further capable of generating enhanced messages as described above, for example, with reference to  FIG. 8 . The processor  1025  and MIH function  1030  are further configured to implement IEEE 802.21 protocols for MIH peer messaging, such as messaging between the access point  1005  and an MIH server (MIHS)  1045 , or a PoS (not shown). The transformation of MIH message, and the extraction of MIH messages from received messages may be performed by either processor  1025  or MIH function  1030 , or by a combination of the two. 
         [0117]      FIG. 11  is a signal diagram of a system  1100  performing Inter-RAT Handover using 802.21 media independent normalizing functions. The system includes a WTRU  1110 , a source network  1020 , an MIH Proxy  1130  and a target network  1140 . 
         [0118]    Referring to  FIG. 11 , the WTRU  1110  searches neighboring cells  1115  and provides a measurement report  1125  to the MIH Proxy  1130  via the source network  1120 . The MIH Proxy  1130  performs reservation of resources  1135  for the target network  1140 . Once the resources are reserved  1150  in the target network  1140 , the source network  1120  is informed of the successful reservation of resources  1155  via the MIH Proxy  1130 . The handover information  1160  is then sent from the source network  1120  to the WTRU  1110 . The WTRU  1110  then performs the handover  1165  to the target network  1140 . The target network  1140  then sends a handover complete message  1170  to the source network  1120 . 
         [0119]      FIG. 12  is a signal diagram of a system  1200  performing Inter-RAT Handover using 802.21 media independent normalizing functions and single-radio with on-off techniques. The system includes a WTRU  1210 , a source network  1220 , an MIH server  1230 , and a target network  1240 . 
         [0120]    Referring to  FIG. 12 , the WTRU  1210  searches neighboring cells  1215  and provides neighbor information  1225  to the MIH. Optionally, the WTRU  1210  may be triggered by an MIH request  1235  to begin searching neighboring cells  1215 . Upon receiving the neighbor information  1225 , the MIH server  1230  performs reservation of resources for the target cell  1245  via the source network  1220 . Once the resources are reserved  1250  in the target network  1240 , the source network  1220  is informed of the successful reservation of resources  1255 . The handover information  1260  is then sent from the source network  1220  to the WTRU  1210 . The WTRU  1210  then performs the handover  1265  to the target network  1240 . The target network  1240  then sends a handover complete message  1270  to the source network  1220 . 
         [0121]      FIG. 13  is a signal diagram of a system  1300  performing Inter-RAT Handover using 802.21 media independent normalizing functions and multi-radio techniques. The system includes a WTRU  1310 , a source network  1320 , an MIH server  1330 , and a target network  1340 . 
         [0122]    Referring to  FIG. 13 , the WTRU  1310  searches neighboring cells  1315  and provides neighbor information  1325  to the MIH. Optionally, the WTRU  1310  may be triggered by an MIH request  1335  to begin searching neighboring cells  1315 . Upon receiving the neighbor information  1325 , the MIH server  1330  performs reservation of resources for the target cell  1345 . Once the resources are reserved  1350  in the target network  1340 , the source network  1320  is informed of the successful reservation of resources  1355 . The handover information  1360  is then sent from the source network  1320  to the WTRU  1310 . The WTRU  1310  then performs the handover  1365  to the target network  1340 . The target network  1340  then sends a handover complete message  1370  to the source network  1320 . 
         [0123]    Note that the target network  1340  can also send the resource reservation directly to the WTRU  1310  using the target network air interface (not shown), without having to go through the source network  1320 . The WTRU  1310  has dual radio so it can receive from the target network  1340  without service interruption from the source network  1320 . The source network  1320  should be notified that the handover has been completed, but either the target network  1340  or the WTRU  1310  can release the connection. In this situation, the MIH server  1330  informs the WTRU  1310  to perform the handover based either on dynamic measurements or static policies. The WTRU  1310  then proceeds to reserve and connect directly to the target network  1340  without passing through the MIH server  1330  or the source network  1320 . 
         [0124]    Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. The methods or flow charts provided in the present invention may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
         [0125]    Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. 
         [0126]    A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) module.