Patent Publication Number: US-2007110075-A1

Title: Media independent handover application server for facilitating seamless integration of multi-technology networks

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application claims the benefit of U.S. Provisional Application No. 60/733,705 filed Nov. 4, 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 to implementing media independent handover (MIH) services, (e.g., handover commands, event notification and network information services), by incorporating Internet protocol (IP) multimedia subsystems (IMS) within Third Generation Partnership Project ( 3 GPP) networks.  
     BACKGROUND  
      The IEEE 802.21 standard defines mechanisms and procedures that aid in the execution and management of inter-system handovers. Under IEEE 802.21, three main services can be accessed by mobility management applications in order to aid in the management of handover operations and system discovery and system selection. These services include an event service, an information service and a command service. These services do not depend on each other and, as a result, may be delivered independently.  
      Currently, however there are no interfaces or mechanisms that describe how IEEE 802.21 services may interact with existing mobility management and handover functionality already defined within relevant 3GPP specifications. There are no procedures or functionality to integrate IEEE  802 . 21  services within  3 GPP unless existing mobility management mechanisms and handover procedures are modified. Therefore, an MIH application server that is capable integrating MIH Services in a 3GPP based network is required.  
     SUMMARY  
      The present invention is related to an MIH application server which facilitates seamless integration of multi-technology networks. The MIH application server includes a higher layer transport unit for interfacing with at least one dual mode terminal, a layer  2  (L 2 ) transport unit for interfacing with the dual mode terminal via a first access network, (e.g., IEEE 802.21, Ethernet and the like), and a session initiation protocol (SIP) interface for interfacing with the dual mode terminal via a second access network, (e.g., a 3GPP network). The MIH application server facilitates seamless integration of Internet protocol (IP) functions of the dual mode terminal via the higher layer transport unit, facilitates seamless integration of IEEE 802 functions of the dual mode terminal via the L 2  transport unit, and supports SIP signaling between the MIH application server and the dual mode terminal via the second access network.  
      The present invention provides a mechanism that allows IEEE 802.21 servers to communicate with 3GPP systems. The present invention defines a network architecture that supports IEEE 802.21 based intersystem handovers using an MIH server as an application server or part of an application server handling mobility or call control which interfaces with 3GPP systems.  
      In the 3GPP specification TS 23.228 IP multimedia subsystem, stage  2  (release  7 ), the concept of an application server is defined. The present invention takes advantage of some application server properties, such as the possibility to reside within the user&#39;s home network or in a third party location. The application server may then present two main interfaces: one interface supporting the IEEE 802.21 protocol, (or a subset of it), and a standard session initiation protocol (SIP) with IMS extensions. The present invention may be incorporated into 3GPP networks by becoming an IMS application server.  
      The present invention is applicable to IEEE 802 technologies, wireless local area network (WLAN) baseline air interface standards, IEEE 802.11 baseline, IEEE 802.11a orthogonal frequency division multiplexing (OFDM) 5GHz WLAN, IEEE 802.1 lb high rate direct sequence spread spectrum (HR-DSSS) 2.4GHz WLAN, IEEE 802.11g OFDM 2.4GHz WLAN, IEEE 802.11j OFDM 10 MHz option WLAN, IEEE 802.11n high-throughput (HT) WLAN, IEEE 802.16 broadband wireless access systems, IEEE 802.21 MIH, WLAN standards supplements to extend operation for particular scenarios, cellular standards such as 3GPP or 3GPP 2  , and other standardized or proprietary wireless technologies similar to IEEE 802 WLANs, such as IEEE 802.15 Bluetooth, and HIPERLAN/ 2 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention will be better understood when read with reference to the appended drawings, wherein:  
       FIG. 1  is a multi-technology network reference model that supports IEEE 802.xx and 3GPP capabilities of a dual mode terminal through the use of an MIH application server which is configured in accordance with the present invention;  
       FIG. 2  is a detailed block diagram of the MIH application server used in the multi-technology network reference model of  FIG. 1 ; and  
       FIG. 3  is a detailed block diagram of an alternate configuration of the MIH application server used in the multi-technology network reference model of  FIG. 1 .  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention allows the introduction of MIH Services, (e.g., handover commands, event notification and network information services), by making use the IMS architecture. The IMS architecture in 3GPP facilitates the introduction of application services, by establishing a set of common rules that all applications must follow, based on SIP signaling. From this perspective, MIH may be perceived as an application server on its own right, or even as part of another application server such as the voice call continuity (VCC) application server, (e.g., consisting of domain transfer function (DTF)/call session adaptation function (CSAF) that supports the VCC application at the IMS network entity, or a mobility management entity (MME) in long term evolution (LTE)).  
       FIG. 1  is a multi-technology network reference model  100  that supports IEEE 802.xx, (e.g., IEEE 802.21), and 3GPP capabilities of a dual mode terminal  110  through the use of an MIH application server  105  which is configured in accordance with the present invention. The network reference model  100  includes an MIH application server  105 , a dual mode terminal  110 , an IEEE 802.xx access network  115  and an S-CSCF unit  120  which operates in a 3GPP access network  125 . SIP signaling is used by the MIH application server  105  to communicate with the S-CSCF unit  120  over an SIP higher layer transport interface  130 . The IEEE 802.xx access network  115  may be an IEEE 802.xx access point (AP) or an IEEE 802.xx access router (AR).  
      The dual mode terminal  110  includes an MIH user unit  135 , a higher layer transport unit  140 , an MIH function unit  145 , a 3GPP interface  150  and an IEEE 802.xx interface  155 .  
      The dual mode terminal  110  is connected to the IEEE 802.xx access network  115  via an L 2  transport connection  160 , over which information service is provided, and an L 2  transport connection  165  over which MIH commands are provided. When the 3GPP interface  150  of the dual mode terminal  110  is connected to the 3GPP access network  125  via an IP connection  170 , mobility is controlled according to the 3GPP specification.  
      The MIH application server  100  includes an L 2  interface  180  by which information service is established via the L 2  transport connection  160 , MIH commands are exchanged via the L 2  transport connection  165  and events are received via L 2  transport connections  168 . The dual mode terminal  110  exchanges IMS messages with the S-CSCF unit  120  in the 3GPP access network  125  via the IP connection  170  over which IP multimedia session control is supported through SIP. An IP connection  175  is established between the dual mode terminal  110  and the MIH application server  105  to provide a pathway for implementing an event service (ES), a command service (CS) and an information service (IS) over a higher layer (IP) transport. The dual mode terminal  110  is adaptable to multi-technology and multi-modes, (e.g., UMTS/GSM, IEEE 802.11/802.16 and the like). The dual mode terminal  110  supports IEEE 802.xx technology, (e.g., IEEE 802.21, Ethernet and the like), and SIP.  
      When the dual mode terminal  110  needs to switch from the 3GPP access network  125  to the IEEE 802.xx access network  115 , mobility is controlled by the MIH application server  105  via the L 2  interface  180 , (e.g., IEEE 802.xx based), or via the L 3  interface  185 , (e.g., IP based).  
       FIG. 2  shows a detailed block diagram of the MIH application server  105  used in the multi-technology network reference model  100  of  FIG. 1 . The MIH application server  105  includes an MIH function unit  205 , an interworking function (IWF) interface  210 , an SIP interface  215 , a mobility and handover policy function (MHPF) unit  220 , a high layer transport unit  225  and an L 2  transport unit  230 .  
      The MIH application server  105  facilitates seamless integration of IP functions to/from the dual mode terminal  110  over any IMS capable network via the higher layer transport unit  225 . The MIH application server  105  facilitates seamless integration of IEEE 802.xx functions to/from the dual mode terminal  110  via an 802.xx access network  115  via the L 2  transport unit  230 . The MIH application server  105  also supports SIP signaling and interfaces with the S-CSCF  120  in the 3GPP access network  125  via the SIP interface  215 .  
      The MIH function unit  205  receives handover triggers in the form of MIH events, and also receives handover messages in the form of handover command responses, (e.g., a handover complete message), via the higher layer transport unit  225  and/or the L 2  transport unit  230 .  
      The MIH function unit  205  outputs handover commands either through the higher layer transport unit  225 , (e.g., over IP), or through the L 2  transport unit  230 , (e.g., the IEEE 802.11 management plane), in response to the MIH events and handover messages received via the higher layer transport unit  225  and/or the L 2  transport unit  230 . The MIH function unit  205  may also output events signaling to the MHPF unit  220 , (e.g., the change of the current state of the link layer technology supporting the session). The MIH function unit  205  may also output events signaling to the IWF interface  210 , (e.g., indicating the successful completion of a handover).  
      The IWF interface  210  interprets SIP messages received via the SIP interface  215  using predetermined logic and translates the SIP messages into MIH messages for transmission, and vice versa.  
      The IFW interface  210  receives events from the MIH function unit  205 , SIP signaling from the SIP interface  215  and commands from the MHPF unit  220  that need to be translated into either MIH or SIP signaling. The IFW interface  210  outputs commands to the MIH function unit  205  or the SIP interface  215 .  
      The MHPF unit  220  dynamically determines the specific behavior and mapping of SIP Messages to MIH Messages, and vice versa. The MHPF unit  220  may control handovers across heterogeneous networks supporting both IEEE 802.21 and SIP based signaling.  
      The MHPF unit  220  receives handover events and SIP signaling, and outputs handover commands and SIP call control signaling.  
      The SIP interface  215  receives commands from the MHPF unit  220  for session control purposes, and may also receive events from the MIHF unit  220  via the IWF interface  210 . The SIP interface  215  outputs SIP signaling for call/session control purposes.  
       FIG. 3  shows a detailed block diagram of an alternate embodiment of an MIH application server  105 ′ used in the multi-technology network reference model  100  of  FIG. 1 . In the MIH application server  105 ′, a mapping function interface  310  is used in lieu of the IFW interface  210  shown in  FIG. 2 . The IWF interface  310  is responsible for mapping IEEE 802.xx messages and procedures into SIP signaling based on a simple translation table, without the use of any additional logic.  
      The MIH application server  105  integrates both IEEE 802.21 based and SIP based call control functionality for calls or sessions that are handled over a packet data network with both  3 GPP and IEEE 802.xx access networks.  
      A practical example could be the handling of a voice over Internet Protocol using SIP as the call control mechanism. The following constitutes basic session set-up procedure and how the MIH application server  105  could handle this scenario, including mobility.  
      A first IMS user initiates an IMS session with a second IMS user by transmitting an SIP INVITE message to the S-CSCF unit  120  in the 3GPP access network via the IP connection  170 . The SIP INVITE message is forwarded by the S-CSCF unit  120  to the SIP interface  215 . The SIP interface  215  analyzes the SIP INVITE message and routes it to the second IMS user.  
      The second IMS user, (e.g., the called party), answers the SIP INVITE message with an SIP ACCEPT message, which is sent to the first IMS user via the MIH application server  105 . The SIP ACCEPT message authorizes the establishment of a session between the first and second IMS users, thus allowing the flow of media through a media plane which supports the session. The MIU application server  105  remains in the signaling path between the first and second IMS users, such that the mobility of the session can be monitored and controlled.  
      Once the session is established, the first IMS user may change its serving network from the current  3 GPP access network  125  to an available IEEE 802.xx access network  115 , (e.g., an IEEE 802.11 access network or an Ethernet network). This is detected though an IEEE 802.xx, (e.g., IEEE 802.21), event that is routed from the dual mode terminal  110  of the first IMS user to the MIH function unit  205  within the MIH application server  105 .  
      The MIH function unit  205  relays this message to the MHPF unit  220  which determines that a handover should be triggered towards the IEEE 802.xx network  115 . The MHPF unit  220  uses IEEE 802.xx messages to trigger the handover.  
      When the handover has been successfully completed, a handover complete message is received at the MIH function unit  205  residing within the MIH application server  105 . The handover complete message is relayed to the IWF interface  210  or the mapping function interface  310 , which then translates the handover complete message into an SIP REINVITE message which is then output toward the second user via the SIP interface  215  and the 3GPP access network  125 . The SIP REINVITE message indicates to the IMS second user that the first IMS user has moved to a new network.  
      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.