Abstract:
A method and system for integrating media independent handover (MIH) under IEEE 802.21 and unlicensed mobile access (UMA) are disclosed. A public land mobile network (PLMN) and an unlicensed mobile access network (UMAN) are concurrently deployed. UMA is supported such that a multi-mode wireless transmit/receive unit (WTRU) may access the UMAN to receive PLMN services through the UMAN. MIH entities are included both in the WTRU and the UMAN and the MIH entity of the WTRU monitors handover events and information and generates a handover trigger for handover between the PLMN and the UMAN. The MIH entity in the UMAN interacts with the MIH entity of the WTRU to report a remote event, handover information and command.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/681,259 filed May 16, 2005, which is incorporated by reference as if fully set forth. 

   FIELD OF INVENTION 
   The present invention is related to wireless communication systems. More particularly, the present invention is related a method and system for integrating media independent handovers (MIHs) under IEEE 802.21 and unlicensed mobile access (UMA). 
   BACKGROUND 
   Different types of wireless communication systems have been developed to provide different types of services. Some examples of the wireless communication systems include a wireless local area network (WLAN), a wireless wide area network (WWAN) and a cellular network such as universal mobile telecommunication systems (UMTS). Each of these systems have been developed and tailored to provide specific applications for which each system is intended. 
   With the pervasive adoption of wireless communication networks in enterprise, residential and public domains, continuous connectivity can be supported as the users move from one network to the other. With the emerging “always-on” life style, wireless transmit/receive units (WTRUs), (i.e., mobile stations), are required to support multiple heterogeneous networks. For seamless handover between these networks, an IEEE 802.21 MIH has been proposed. 
   In the meanwhile, UMA technology provides access to a global system for mobile communication (GSM) and general packet radio services (GPRS) over unlicensed spectrum technologies, such as Bluetooth™ and IEEE 802.11. By deploying UMA technology, service providers can enable subscribers to roam and handover between cellular networks and public and private unlicensed wireless networks using dual-mode WTRUs. With UMA, subscribers receive continuous services as they transition between networks. 
   However, UMA technology does not address how a particular handover condition arises and how heterogeneous link layers can communicate these conditions to the upper layers handling the handover. Thus, there are no procedures or functionality in UMA to generate triggers toward upper layers. Therefore, there is a need to provide the triggers for handover within the UMA architecture. 
   SUMMARY 
   The present invention is related to a method and system for integrating MIH under IEEE 802.21 and UMA. A public land mobile network (PLMN) and an unlicensed mobile access network (UMAN) are concurrently deployed. UMA is supported such that a multi-mode WTRU may access the UMAN to receive PLMN services through the UMAN. MIH entities are included both in the WTRU and the UMAN and the MIH entity of the WTRU monitors handover events and information and generates a handover trigger for handover between the PLMN and the UMAN. The MIH entity in the UMAN interacts with the MIH entity of the WTRU to report a remote event, handover information and command. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more detailed understanding of the invention may be had from the following description of a preferred example, given by way of example and to be understood in conjunction with the accompanying drawing wherein: 
       FIG. 1  shows a prior art UMA functional architecture of a wireless communication system; 
       FIG. 2  shows a WTRU and in a network along with signalling between MIH entities in accordance with the present invention; 
       FIG. 3  shows a UMA-MIH protocol architecture in a circuit switched (CS) domain in accordance with the present invention; 
       FIG. 4  shows a UMA-MIH protocol architecture in a packet switched (PS) domain in accordance with the present invention; 
       FIG. 5  shows a WTRU CS domain signaling architecture in accordance with the present invention; 
       FIG. 6  shows a WTRU PS domain signaling architecture in accordance with the present invention; and 
       FIG. 7  is a flow diagram of a process for triggering handover between a an unlicensed mobile access network (UMAN) and a public land mobile network (PLMN) in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereafter, the terminology “WTRU” includes, but is not limited, to a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” and “AP” include, but are not limited to, a Node-B, a site controller or any other type of interfacing device in a wireless environment. 
   The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components. 
     FIG. 1  shows a prior art UMA functional architecture of a wireless communication system  100 . The wireless communication system  100  comprises a UMAN  110  and a PLMN  120 . The UMAN  110  may be a Bluetooth™ network, an IEEE 802.11 network or other similar wireless networks using unlicensed frequency band. The PLNM  120  may be any type of cellular networks including, but not limited to, third generation partnership project (3GPP) and 3GPP2 networks. 
   The UMAN  110  comprises at least one AP  112  and at least one UMA network controller (UNC)  116  and a broadband IP network  114  connecting the AP  112  and the UNC  116 . The AP  112  provides radio access to a WTRU  102 . The broadband IP network  114  provides connectivity between the AP  112  and the UNC  116 . The WTRU  102  is a multi-mode device which supports more than one interface including, but not limited to, IEEE 802.3, 802.11, 802.15, 802.16, 802.20, Bluetooth™, HYPERLAN/2, 3GPP and 3GPP2. The PLMN  120  includes, among other things, a mobile switching center (MSC)  122 , a serving GPRS support node (SGSN)  124 , an authentication, authorization and accounting (AAA) server  126  and a home location register (HLR)  128 . The UNC  116  connects to the MSC  122  and the SGSN  124  for supporting circuit switched (CS) and packet switched (PS) services, respectively, for the WTRU  102  through the UMAN  110 . 
     FIG. 2  shows signalling between a WTRU  202  and a UMAN  210 , (i.e., an AP  212 , a UNC  216  and an MIH network entity  218 ), in accordance with the present invention. MIH entities  252 ,  254  are included in the WTRU  202  and the network  210 , respectively, to support seamless handover between heterogeneous networks. The MIH entities  252 ,  254  are separate layer-independent entities and may work independently as a sole handover management entity or may coordinate with an existing technology-specific handover entity. The MIH entity  254  in the network may be a separate entity or may reside in any entity, such as the AP  212  or the UNC  216 . 
   The WTRU  202  includes an IEEE 802 interface  220 , a GSM EDGE radio access network (GERAN) network interface  230  and an MIH entity  252 . The WTRU  202  may have one or more additional MIH user  232 . The IEEE 802 interface  220  includes a logical link control/convergence sub-layer (LLC/CS)  222 , a medium access control (MAC) layer  224 , and a physical (PHY) layer  226 . It should be noted that  FIG. 2  shows only lower layer entities for simplicity and higher layer entities are shown in  FIG. 5 . 
   The MIH entity  252  in the WTRU  202  exchanges local handover events, information and commands  244   a - 244   d  with lower layers of the WTRU  202 , (i.e., the LLC/CS layer  222 , the MAC layer  224  and a PHY layer  226 ), and exchanges remote events, information and commands  242  with the MIH entity  254  of the network  210 . Local handover information is communicated between the MIH entity  252  and the MAC/PHY layers  224 / 226  by an information service (IS)  244   a , and a command service (CS)  244   b  and an event service (ES)  244   c  are exchanged between the MIH entity  252  and the MAC/PHY layers  224 / 226  for local handover events and commands via management entity  228 . These local events, information and commands  244   a - 244   c  are communicated through a LINK-SAP  264  of the MIH entity  252 . The remote events  242  are also communicated between the MIH entity  254  and the MIH entity  252  by an IS, CS and ES over layer  2  transport  242 . The MIH entity  252  also communicates with the LLC/CS  222  through LLC-SAP  262  for the local events. 
   The GERAN network interface  230  communicates handover events with the MIH entity  252  by ES, CS and IS  244   e  via a 3G-LINK-SAP  266 . The additional MIH user  232  also communicates handover events with the MIH entity  252  by ES, CS and IS  244   x  via an MIH-SAP  268 . The MIH user  232  is any mobility application that can take advantage of MIH services provided by the MIH entity  252 . UMA-RR  512  and GSM-RR  522  in  FIG. 5  are examples of MIH users. 
   The handover events and information may be any events or information relevant to handover. For example, if an unrecoverable failure condition occurs in the network  210 , the network  210  may signal this occurrence to the WTRU  202  so that the WTRU  202  may switch to a different network interface. Another example is the existence of alternative networks with better radio/service condition, (e.g., better price or better QoS). Commands are sent from the MIH User, (e.g., UMA-RR  512  or GSM-RR  522  in  FIG. 5 ), to order an execution of a handover. 
   The AP  212  includes an LLC/CS  272 , a MAC layer  274 , a PHY layer  276 . In the network, local handover events, information and commands are communicated between the MAC/PHY layers  274 / 276  and the MIH entity by IS, CS and ES  246   a - 246   c  via a management entity  278 , and between the LLC/CS  272  and the MIH entity  254 . 
   The MIH entity  254  may exist separately and communicate the local and remote events, information and commands with the AP  212  using a higher layer transport protocol or L2 transport. Alternatively, the MIH entity  254  and the AP  212  may reside in the same place. The MIH entity  254  includes a LINK-SAP  282  for communicating local events from the MAC/PHY layers  274 / 276  and an LLC-SAP  284  for communicating remote events and local events from the LLC/CS  272 . 
   Current and any anticipated future changes in condition of different networks may be signalled via NET-SAPs  269 ,  286  between the MIH entities  252 ,  254  and/or the MIH network entity  218 , (such as an MIH server controller), by IS/CS/ES  280  over a higher layer transport protocol, such as IP. These conditions include changes in the MAC layer and the PHY layer states or changes in certain network attributes, such as changes in load conditions. The MIH entity  252  of the WTRU  202  determines whether a handover is required based on the collected events, information and commands in accordance with certain criteria, such as link quality, service and subscription. 
   The MIH network entity  218  is any entity within the network that is able to operate according to the IEEE 802.21 protocol. The MIH network entity  218  handles messages used by any of the MIH services, (i.e., ES, IS and CS). However, the MIH network entity  218  does not have to respond or act upon these messages, but may ignore the messages. The MIH entity  254  communicates the handover events with the MIH network entity  218  by an IS, ES, CS via MIH-SAP  288 . The MIH network entity  218  also communicates with the UNC  216  using a higher layer transport protocol. For example, the MIH network entity may generate handover commands and information and send them to the MIH entity  254  and the MIH entity  254  may generate remote events and inter-technology network information requests. In both cases messages flow though the  280  interface. 
   The UNC  216  provides network capability information to the MIH network entity  218 . In addition the interface between the UNC  216  and the MIH network entity  218  can be used to support inter-technology mobility management messages for WTRUs that are IEEE 802.21 capable but do not support UMA functionality. In this scenario the MIH network entity  218  may serve as an inter-working function between the UNC and the WTRU. 
     FIGS. 3 and 4  show UMA-MIH protocol architecture in a CS domain and a PS domain, respectively, in accordance with the present invention. The UMA protocol architecture is well known in the art and, therefore, will not be explained herein for simplicity. In accordance with the present invention, the MIH entities  352 ,  354  are included in the protocol stack of the WTRU  302  and the network, respectively, as explained hereinabove. The MIH entity in the network may be a separate entity or may reside in any network entity, such as the AP  312  as shown in  FIGS. 3 and 4 . The MIH entity  352  in the WTRU  302  interacts with the MIH entity  354  to send and receive remote events as indicated by arrows  302 ,  402 . The  FIGS. 3-5  depict IEEE 802.xx technology in the lower layers as an example, and it should be noted that any UMA technology, such as Bluetooth™, may be implemented instead of IEEE 802.xx technology. 
     FIG. 5  shows a WTRU CS domain signaling architecture in accordance with the present invention. The WTRU  502  is a multi-mode device including both a UMA interface and a GSM interface. It should be noted that  FIG. 5  depicts a GSM interface as an example and 3GPP, 3GPP2 or any other cellular network interface may be implemented. The WTRU  502  comprises a UMA protocol stack  510 , a GSM protocol stack  520 , an MIH entity  530  and an access mode switch  540 . The MIH entity  530  is provided in the WTRU  502  for monitoring handover triggering events, information and commands and generates and sends a handover trigger to an upper layer, (such as a mobility management (MM) layer  526 ). The MM layer  526  and a connection management (CM) layer  527  operate in common for both a GSM mode and a UMA mode and the GSM mode and the UMA mode is selectively switched by the access mode switch  540 . The individual layers and entities of the UMA protocol stack  510  and the GSM protocol stack  520  are well known in the art and, therefore, will not be explained herein for simplicity. The UMA-radio resource entity (UMA-RR)  512  and the GSM-radio resource entity (GSM-RR)  522  provide radio resource management functions and interact with the MIH entity  530 . 
   New service access points (SAPs) are provided in addition to existing SAPs, (UMAGSM-SAP  514  and GSMUMA-SAP  524 ), between the UMA-RR  512  and a remote IP layer  517  and the MIH entity  530  and between the GSM-RR  522  and the MIH entity  530  in accordance with the present invention. An MIH-SAP  504  is provided between the MIH entity  530  and the UMA-RR  512  and a 3GLINK-SAP  508  is provided between the MIH entity  530  and the GSM-RR  522 . A NET-SAP  506  is provided between the MIH entity  530  and a remote IP layer  517 . 
   The GMS-RR  522  provides an interface to an existing radio condition that might be used by the MIH entity  530  to generate a handover indication. This information can be retrieved directly from the GSMUMA-SAP  524 . The difference between the GSMUMA-SAP  524  and the 3GLINK-SAP  508  is that going through the MIH entity  530  a compound message including both IEEE 802 and GERAN is sent to the UMA-RR user as opposed to only GERAN information. 
   The MIH entity  530  collects local events  544  from the LLC layer  516 , the MAC layer  518 , (via a MAC layer management entity (MLME)  518   a ), and the PHY layer  519 , (via a PHY layer management entity (PLME)  519   a ), and remote events  542  and handover related information from MIH peers in the network. The MIH entity  530  monitors handover triggering events and generates a handover trigger based on the collected events and information if a certain threshold is exceeded. 
     FIG. 6  shows a WTRU PS domain signaling architecture in accordance with the present invention. The WTRU  602  is a multi-mode device including both a UMA interface and a GPRS interface. It should be noted that  FIG. 6  depicts a GPRS interface as an example and 3GPP, 3GPP2 or any other cellular network interface may be implemented. The WTRU  602  comprises a UMA protocol stack  610 , a GPRS protocol stack  620 , an MIH entity  630  and an access mode switch  640 . The MIH entity  630  is provided in the WTRU  602  for monitoring handover triggering events, information and commands and generates and sends a handover trigger to an upper layer. The LLC layer  650  operates in common for both a GPRS mode and a UMA mode and the GPRS mode and the UMA mode is selectively switched by the access mode switch  640 . The UMA-radio link control (UMA-RLC) layer  512  peers with the GPRS-RLC layer  522  to provide coordination for access mode switching and handovers. 
   New service access points (SAPs) are provided in addition to existing SAPs, (UMAGPRS-SAP  614  and GPRSUMA-SAP  624 ), between the UMA-RLC  612  and the MIH entity  630  and between the GPRS-RLC  622  and the MIH entity  630  in accordance with the present invention. An MIH-SAP  604  is provided between the MIH entity  630  and the UMA-RLC  612  and a 3GLINK-SAP  608  is provided between the MIH entity  630  and the GPRS-RLC  622 . 
   The MIH entity  630  collects local events  644  from the LLC layer  616 , the MAC layer  618 , (via a MAC layer management entity (MLME)  618   a ), and the PHY layer  619 , (via a PHY layer management entity (PLME)  619   a ). The MIH entity  630  exchanges remote events and handover information  642 ,  644  from MIH peers in the network. The remote events and handover information may be sent via a NET-SAP  652  to an MIH peer. The MIH entity  630  monitors handover triggering events and generates a handover trigger based on the collected events and information if a certain threshold is exceeded. 
     FIG. 7  is a flow diagram of a process  700  for triggering handover between a UMAN and a PLMN in accordance with the present invention. An MIH entity is provided in a WTRU and a network, respectively (step  702 ). The MIH entity of the WTRU collects handover events and handover related information from lower layers and peer MIH entities in the network (step  704 ). The MIH entity of the WTRU determines whether a threshold for triggering handover is met based on the collected handover events and handover related information (step  706 ). If the determination at step  706  is positive, the MIH entity of the WTRU initiates a handover between the PLMN and the UMAN by sending a handover trigger to an upper layer (step  708 ). If the threshold is not met, the process  700  returns to step  704  to monitor handover events and information. 
   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.