Abstract:
A method and system for conveying media independent handover (MIH) capability information are disclosed. A wireless communication system includes a plurality of wireless networks deployed under different wireless communication protocols. A multi-mode wireless transmit/receive unit (WTRU) may perform a handover from one wireless network to another for continuous reception of services. The wireless network sends a message to the WTRU which indicates whether the wireless network supports MIH services and a supported MIH mode. The WTRU receives the message and makes a handover decision based on the message.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional application No. 60/661,379 filed Mar. 14, 2005, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention is related to wireless communication systems. More particularly, the present invention is related to a method and system for conveying media independent handover (MIH) capability information.  
       BACKGROUND  
       [0003]     Currently, many different types of wireless networks are deployed, which provide specific services that each wireless network is intended for. For example, wireless local area networks (WLANs), such as IEEE 802.xx based networks, provide high data rate services in a limited coverage area while cellular networks, such as universal mobile telecommunication system (UMTS) networks, provide relatively low to medium data rate services in a very large coverage area supporting high speed mobility.  
         [0004]     IEEE 802.21 MIH has been proposed for a seamless handover among these heterogeneous networks enabling continuous reception of services while roaming around these heterogeneous networks. However, MIH may not be supported by all networks and the supported MIH mode may vary from network to network. Therefore, it would be desirable to provide wireless transmit/receive unit (WTRU) MIH capability information, (e.g., including whether a wireless network supports MIH and, if it is supported, what mode of MIH is supported).  
       SUMMARY  
       [0005]     The present invention is related to a method and system for conveying MIH capability information. A wireless communication system includes a plurality of wireless networks deployed under different wireless communication protocols. A multi-mode WTRU may perform a handover from one wireless network to another for continuous reception of services. The wireless network sends a message to the WTRU which indicates whether the wireless network supports MIH services and a supported MIH mode. The WTRU receives the message and makes a handover decision based on the message. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawings wherein:  
         [0007]      FIG. 1  shows an exemplary wireless communication system configured in accordance with the present invention;  
         [0008]      FIG. 2  shows a medium access control (MAC) protocol data unit (PDU) with logical link control (LLC) encapsulation for conveying MIH services in accordance with the present invention;  
         [0009]      FIG. 3  shows an IP frame for conveying MIH services in accordance with the present invention;  
         [0010]      FIG. 4  shows an exemplary bit map for conveying MIH capability information using a full octet in accordance with the present invention;  
         [0011]      FIG. 5  shows an exemplary bit map for conveying MIH capability information in a capability information field of a beacon frame in accordance with the present invention;  
         [0012]      FIG. 6  shows an exemplary bit map for conveying MIH capability information in accordance with the present invention; and  
         [0013]      FIG. 7  is a block diagram of a WTRU in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     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 access point (AP) includes but is not limited to a Node-B, a site controller or any other type of interfacing device in a wireless environment.  
         [0015]     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.  
         [0016]      FIG. 1  shows an exemplary wireless communication system  100  configured in accordance with the present invention. The system  100  includes a plurality of wireless networks  110  and  111   a - 111   n  that are concurrently deployed under different wireless communication standards and provide specific services in specific coverage areas which may or may not overlap each other. For example, the system  100  may include a cellular network  110  and a plurality of wireless local area networks  111   a - 111   n . The cellular network  110  may be third generation partnership (3GPP) networks or 3GPP2 networks, and the wireless local area networks  111   a - 111   n  maybe IEEE 802 based networks, (such as 802.11 baseline, 802.11a, 802.11b, 802.11g, 802.11j, 802.11n, 802.11e, 802.11s, 802.11k, 802.11v, 802.15, 802.16 and 802.21 networks), Bluetooth™ networks, HIPERLAN/2, or any other type of networks. The cellular network  110  includes a plurality of cells  112 , each of which is covered by a base station  114 . The WLANs  111   a - 111   n  are served by APs  122   a - 122   n , respectively.  
         [0017]     As a WTRU  130  roams around an area where a plurality of heterogeneous networks  110  and  111   a - 111   n , (e.g., cellular networks and WLANs), are concurrently deployed, the WTRU  130  needs to determine, quickly, the most suitable network based on requirements of the service requested by the user. For example, a video application may require a high bandwidth channel, while a voice application may be sufficient with a low bandwidth channel. The speed at which the WTRU  130  can find a suitable network depends on its ability to retrieve network information from available networks.  
         [0018]     In accordance with the present invention, the networks  110  and  111   a - 111   n  convey MIH capability information to the WTRU  130  preferably via a broadcast channel. The MIH capability information may be transmitted over either a wired or wireless medium. The MIH capability information indicates not only whether the network support MIH services but also the supported MIH mode. MIH services include information service, event service and command service for conveying handover related information, events and command. The supported MIH mode indicates MIH functionality supported by the network. With these two pieces of information, the WTRU  130  can make a more intelligent decision with regards to whether or not the particular network should be considered for handover.  
         [0019]     For example, the MIH services may be provided either over layer 2 (L2) procedures and messages or over layer 3 (L3) procedures and messages, (such as Internet protocol (IP)).  FIG. 2  shows a MAC PDU  200  with LLC encapsulation for conveying MIH services in accordance with the present invention. The MAC PDU  200  includes MAC headers  202 , an LLC header  204 , an RFC 1042 encapsulation  206 , an Either Type field  208 , a frame body  210  and a frame check sequence (FCS) field  212 . The LLC header  204  includes a sub-network access protocol (SNAP) destination service access point (DSAP) field  214 , an SNAP source service access point (SSAP) field  216  and a control field  218 . The RFC 1042 encapsulation  206  and the Either Type field  208  are used for carrying IP datagram over IEEE 802 networks. The MIH protocol used for the provision of MIH services can be carried over a L2 transport using an LLC encapsulation by defining a new Ether Type  208  that uniquely identifies the MIH protocol. An MIH header  220  and an MIH payload  222  are included in the frame body  210 .  
         [0020]     Alternatively, a higher layer protocol such as IP may be used to achieve similar results.  FIG. 3  shows an IP frame  300  for conveying MIH services in accordance with the present invention. MIH services are transported over an IP frame by defining a new Protocol ID  302  and encapsulating the MIH protocol within a data field  304  of the IP frame  300 .  
         [0021]     The present invention provides the WTRU with a means to determine which transport method is supported in a particular network. This information is provided through the MIH mode parameter.  
         [0022]     Since there is not much available space on current broadcast channels, minimum number of bits, preferably two bits, should be used to convey MIH capability information. A simple bit map provides the WTRU  130  with a quick indication of the capabilities of the networks  110  and  111   a - 111   n  with regards to MIH functionality. If more space is available, more information may be provided using more bits, (e.g., a full octet), as shown in  FIG. 4 .  
         [0023]     Exemplary bit maps using two bits, B 0  and B 1 , are explained hereinafter. A combination of two bits indicates whether the network  110  and  111   a - 111   n  supports MIH services and the supported MIH mode. For example, if B 1 =‘0’ and B 0 =‘0’, this indicates that the network  110  and  111   a - 111   n  does not provide any MIH services. However, in such case, the WTRU  130  may still be able to obtain MIH services over and an IP connection. If B 1 =‘0’ and B 0 =‘1’, this indicates that the network  110  and  111   a - 111   n  provides some MIH services, and information services may be accessed over L2 procedures over an Ethernet connection, (such as shown in  FIG. 2 ), without having to rely on IP connectivity. If B 1 =‘1’ and B 0 =‘1’, this indicates that the network  110  and  111   a - 111   n  provides MIH services, and information service is accessible over both L2 procedures and L3 procedures over an IP connection, (such as shown in  FIG. 3 ). If B 1 =‘1’ and B 0 =‘0’, this indicates that the network  110  and  111   a - 111   n  provides some MIH services, (i.e., command and event services), but information service may only be accessed over L3 procedures (i.e., via an IP connection).  
         [0024]      FIG. 5  shows an exemplary bit map for conveying MIH capability information in a capability information field  500  of a beacon frame in an IEEE 802.11 network in accordance with the present invention. In this example, an MIH support bit  502  and an MIH mode bit  504  are added in the capability field  500  of the beacon frame. B 0  and B 1  of the foregoing example are replaced with the MIH support bit  502  and the MIH mode bit  504 , respectively.  
         [0025]      FIG. 6  shows an exemplary bit map for conveying MIH capability information in an IEEE 802.16 network in accordance with the present invention. IEEE 802.16 defines a set of medium access control (MAC) management messages including a subscriber station (SS) basic capability request (SBC-REQ) message and an SS basic capability response (SBC-RSP) message. The SBC-REQ and SBC-RSP messages are exchanged between a WTRU and a network during initialization. A WTRU generates the SBC-REQ message and sends it to the network. The WTRU includes supported physical parameters and bandwidth allocation in the SBC-REQ message. The network sends the SBC-RSP message in response to the SBC-REQ message. The network responds to the subset of the capabilities present in the SBC-REQ message indicating whether they may be used.  
         [0026]     In accordance with the present invention, a new MAC management message type for SBC-REQ and SBC-RSP messages is defined for MIH support.  FIG. 6  shows an exemplary IEEE 802.16 bit map for this purpose. Bit # 0  is reserved. Bit # 1  set to ‘0’ indicates no MIH is supported by the network and bit # 1  set to ‘1’ indicates MIH services are supported by the network. Bit # 2  set to ‘0’ indicates MIH information is accessible over Ethernet transport and bit # 2  set to ‘1’ indicates MIH information is accessible over IP transport. Other bits may be used to convey other capability information.  
         [0027]     Referring again to  FIG. 4 , an exemplary bit map for conveying MIH capability information using a full octet in accordance with the present invention is shown. A first bit, B 0 , indicates whether the network supports MIH services, (i.e., if B 0 =‘1’, this indicates that the network supports MIH services, and if B 0 =‘0’, this indicates that the network does not support MIH services). If the network supports MIH services, (i.e., B 0 =‘1’), then additional bits, (in the example of  FIG. 4 , seven (7) bits, B 1 -B 7 ), provide further information with regards to the capability of the network to deliver these services. If B 1 =‘0’, this indicates that MIH services are available without the need to contact a separate network entity over IP. If B 1 =‘1’, this indicates that the network does not support MIH services, (particularly, information services), over L2 procedures, and therefore the WTRU is required to contact an information server over an L3 transport. If B 2  is set, (i.e., B 2 =‘1’), this indicates that the network provides cellular integration support and if B 3  is set, (i.e., B 3 =‘1’), this indicates that the network provides IEEE 802.16 support. Other capability information may be provided in a similar manner.  
         [0028]     It should be noted that the bit maps shown in  FIGS. 4-6  are provided as an example, not as a limitation and any variation is possible.  
         [0029]      FIG. 7  is a block diagram of a WTRU  700  in accordance with the present invention. The WTRU  700  includes a receiver  702  and a handover controller  704 . The receiver  702  is configured to receive a message transmitted from a network. The handover controller  704  is configured to extract MIH information from the message. The MIH information indicates whether the wireless network supports MIH services and a supported MIH mode as described hereinbefore. The handover controller  704  then performs a handover based on the MIH information. The WTRU  700  may further comprise a transmitter  706  configured to send a request to the network to request the message, whereby the message may be sent in response to the request.  
         [0030]     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.