Abstract:
Method and apparatus for providing a solution to the handoff problem includes negotiation of new media codes (coders/decoders) for utilization in cases where the two devices involved in the handoff are incompatible. Although mobile IP (MIP) is presently utilized to perform handoff procedures, this technique lacks a trigger mechanism to initiate handoff between two different devices which communicate with two different networks or one common network. In addition, MIP does not address the issue of compatibilities between media types, codes and supported bit rate. The handoff utilizes a session protocol (SIP) message for handoff.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional Patent Application Ser. No. 60/526,135, filed Dec. 1, 2003, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to performing a handoff between two devices which employ different technologies and which are connected to an internet protocol (IP) network by way of two different systems. More particularly, the present invention is related to a method and apparatus for performing a handoff employing SIP protocol conducted during real time sessions between such different devices, and either such different networks or a common network.  
       BACKGROUND  
       [0003]     Session initiation protocol (SIP) protocol is employed to initiate and to modify a multimedia session over the internet protocol (IP) network. For example, SIP is used in one of a universal mobile telecommunications system (UMTS) network to establish a multimedia session between two users wherein at least one of the users operates on the UMTS system. However, SIP protocol has not heretofore been utilized as a mechanism to perform handoff between different devices operating in different systems.  
       SUMMARY  
       [0004]     The present invention is characterized by method and apparatus for providing a unique solution to the handoff problem including negotiation of new media codecs (coders/decoders) for utilization in cases where the two devices involved in the handoff are incompatible. Although mobile IP (MIP) is presently utilized to perform handoff procedures, this technique lacks a trigger mechanism to initiate handoff between two different devices which communicate with two different networks or one common network. In addition, MIP does not address the issue of compatibilities between media types, codecs and supported bit rate. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0005]     The present invention will be understood from a consideration of the accompanying figures wherein like elements are designated by like numerals and, wherein:  
         [0006]      FIG. 1  is a simplified schematic diagram of a network architecture incorporating two incompatible devices and two different systems communicating with said devices.  
         [0007]      FIG. 2  is a flow diagram showing the manner in which a handoff from a wireless local area network (WLAN) network user to a UMTS network user is triggered from the WLAN network;  
         [0008]      FIG. 3  is a flow diagram showing the manner in which a handoff from a WLAN network user to a UMTS network user is triggered from a UMTS network.  
         [0009]      FIG. 4  is a flow diagram similar to that of  FIG. 2  wherein the handoff is made from the UMTS user to the WLAN network user and is triggered from the WLAN network.  
         [0010]      FIG. 5  is a flow diagram similar to that shown in  FIG. 3  wherein the handoff is made from a WLAN network user to a UMTS network user and is triggered from the UMTS network. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]     Making reference to the network architecture  10  of  FIG. 1  there is shown therein two different wireless devices  12  and  32 , device  12  being a personal computer (PC) having a WLAN card  13  enabling the device  12  to establish a wireless communication with a WLAN access point/access router (AP/AR)  14 . PC  12  may be a desktop or laptop and is fitted with a WLAN card  13  and is able to establish a wireless communication with WLAN  14 , through a suitable interface (not shown for purposes of simplicity). PC  12  is coupled to the AAA unit  16  through WLAN  14  to establish access, authorization and accounting (AAA) at  16  and is coupled through internet protocol (IP) network  18  and router  20  to a service server  22  in order to communicate with a called subscriber or other source (not shown) in the network, for example.  
         [0012]     User equipment (UE)  32 , which may be a wireless cell phone, PDA wireless device or other like device having similar capabilities, is adapted for wireless communication with a third generation partnership project (3 GPP) system  23 . UE  32  communicates with the system  23  which receives a wireless message from UE  32  over antenna  30  that couples the communication to a general packet radio service (GPRS) support node (GSN)  28 . The message is also conveyed from GSN  28  to a home subscriber server (HSS)  26  and an AAA  24  (similar to AAA  16 ) for access, authentication and accounting. The home subscriber server (HSS)  26  performs a number of database functions such as the home location register (HLR) function, which provides routing information for mobile terminated calls and short message service and maintains user subscription information which is distributed to the relevant visitor location register (VLR), not shown for purposes of simplicity, or is distributed to the serving GPRS support node (SGSN). The AAA  24  securely determines the identity and privileges of the UE and tracks the UE&#39;s activities.  
         [0013]     A description will now be provided for performing a handoff using SIP when a user wishes to handoff an existing multimedia session between two different types of networks. The two different networks of the example to follow are a WLAN network  14  and a 3GPP UMTS network  23 . The handoff will be described as from a PC, such as the PC  13  shown in  FIG. 1  and equipped with a WLAN card  13 , to a user equipment (UE)  32  which may be a cell phone or the like which optionally may also be equipped with image reception and display capability, to accommodate a multimedia session in accordance with the 3GPP standards.  
         [0014]     Making reference to  FIG. 2 , in which a handoff is triggered by the WLAN network  14 , it is assumed that there is a real time session between PC  12  and a called party which is represented in  FIG. 1  as a real time session in which PC  12 /WLAN card  13  communicates with WLAN network  14  shown at S 1 , WLAN network  14  communicating with IP network  18 , shown at S 2 , the IP network  18 , in turn providing the two-way communication between the PC 12  and service server  12 , shown at S 3 . At this time neither UE  32  nor PC  12  is communicating with UMTS network  23 .  
         [0015]     The user of both PC  12  and UE  32  turns on UE  32  and establishes a connection with the UMTS network  23 , at, S 4 , S 5  and S 6 . The user then decides to trigger a handoff from PC  12  to the UE  32  at S 7  and communicates this handoff request, at S 8 , to the WLAN network  14 . WLAN network  14 , at S 9 , transmits an SIP message, which may either take the form of a SIP handoff message or a SIP invite accompanied with either a target IP address or an email address or a telephone number. This is conveyed through IP network  18 , at S 10 , to service server  22 . Service server  22  transmits an SIP 200 (OK) message, at S 11 , to acknowledge the handoff(HO) message.  
         [0016]     WLAN-equipped PC  12 , receives the SIP 200 OK acknowledgement and, at S 12 , sends an SIP acknowledgement (ACK) to service server  22 . Service server  22  transmits an SIP invite setting forth a list of media types, IP addresses, bit rates, codecs and the like, at S 13  which, in turn, is conveyed through IP network  18  to UMTS network  23  at S 14  and, in turn, from UMTS network  23  to UE  32 , at S 15 . UE  32 , upon receipt of the SIP invite, at S 16 , transmits an SIP 200 OK message acknowledging the acceptable media types, codecs, bit rate and IP address. This is transferred through UMTS network  23  to IP network  18  at S 17 , the IP network  18  conveying this message to service server  22 , at S 18 . Service server  22 , upon receipt of the SIP 200 OK from UE  32 , at S 19 , conveys an SIP acknowledge (ACK) to UE  32 , thereby completing the handoff of the real time session from the WLAN—capable PC  12  to UE  32 , the communication of the real time session now being established between UE  32  and a given source through UMTS network  23 , at S 20 , network  23  conveying this two-way communication to IP network  18  at S 21  and IP network  18  conveying this two-way communication between IP network  18  and service server  22 , at S 22 . The user terminates the session between PC  12  and WLAN network  14 , at S 23 .  
         [0017]      FIG. 3  shows the manner in which a handoff from a PC  12  to a UE  32  is triggered from the UMTS network.  
         [0018]     Initially, it is assumed that the real time multi-media session, which may be voice over internet protocol (VoIP) or video, is presently taking place as represented by the two-way communication S 1  between PC  12  with WLAN card  13  and WLAN network  14  as represented by step S 1 , two-way communication of this session between WLAN network  14  and IP network  18  shown at S 2  and two-way communication between IP network  18  and service server  22 , being shown at S 3 . It is assumed that the user wishes to perform a handoff from PC  12  to UE  32 . This is initiated by turning on UE  32 , at S 4 , so as to connect UE  32  to the UMTS network as shown at S 5  and to the IP network  18 , as shown at S 6 .  
         [0019]     Once the connection with UE  32  is established and the user decides to trigger a handoff to UE  32 , at S 7 , the UE  32 , at S 8  sends an SIP message which may either be a new SIP handoff message or an SIP invite message with new information elements to identify the existing session. This message is transferred through UMTS network  23  to IP network  18 , at S 9 , and thereafter to service server  22 , at S 10 . Service server  22 , upon receipt of the SIP message, transmits an SIP 200 OK to acknowledge the HO message which is conveyed, at S 11 , to IP network  18  which then conveys this message, at S 12  to UMTS network  23 , which, in turn conveys the SIP 200 OK message to UE  32  at S 13 .  
         [0020]     UE  32 , at S 14 , responds to the SIP 200 OK message by sending an SIP acknowledge to the service server  22  thereby establishing the real time session, which originally included PC  12  as a participant, to UE  32  as shown at S 15 , S 16  and S 17 . It should be noted that steps S 15 , S 16  and S 17  are substantially the same as steps S 20 , S 21  and S 22  shown in  FIG. 2 .  
         [0021]     After completing the handoff, service server  22 , at S 18  transmits an SIP BYE to terminate the real time session on the WLAN network. This is conveyed to IP network  28  at step S 18 , which in turn conveys the message to WLAN network  14 , at S 19  which, in turn, conveys the message to the PC  12 , at S 20 .  
         [0022]     PC  12 , equipped with the WLAN card  13 , sends an SIP 200 OK response to acknowledge the termination, which response is conveyed to WLAN network  14  at S 21  and is, in turn, conveyed to IP network  18  at S 22 . The IP network  18 , in turn, conveys the SIP 200 OK message to service server  22  at S 23 . Upon receipt of this message, the service server  22  sends an SIP acknowledge (SIP ACK) which is initially conveyed to IP network  18 , at S 24 , which transfers the SIP ACK message to WLAN  14  at S 25 , WLAN network  14  transferring the SIP ACK message to PC  12  with WLAN card  13 , at S 26 .  
         [0023]     Making reference to  FIG. 4 , in which handoff is triggered from the WLAN network  14 , it is assumed that there is a real time session between UE  32  and a remote party which is represented as a real time session in which UE  32  communicates with UMTS network  23  shown at S 1 , UMTS network  23  communicating with IP network  18 , shown at S 2 , the IP network  18 , in turn providing the two-way communication between the UE  32  and a called subscriber through service server  12 , shown at S 3 .  
         [0024]     The user, at S 4 , turns on PC  12  and establishes a connection with the WLAN network, at S 5 , and IP network  18 , at S 6 . The user then decides to trigger a handoff to the PC  12 , at S 7 , and communicates an SIP handoff request, at S 8 , to the IP network  18 , and service server  22 , at S 9 . The SIP message, may either take the form of a SIP handoff message or a SIP invite accompanied with either a target IP address or an email address or a telephone number. This is conveyed through IP network  18 , at S 9 , to service server  22 . Service server  22  transmits an SIP 200 (OK) message to PC  12 , at S 10 , to acknowledge the handoff (HO) message. WLAN-equipped PC  12 , receives the SIP 200 (OK) acknowledgement and, at S 11 , sends an SIP acknowledgement (ACK) to service server  22 . Service server  22  transmits an SIP invite setting forth a list of media types, IP addresses, bit rates, codecs and the like, at S 12 , which, in turn, is conveyed through IP network  18  to WLAN network  14 , at S 13 , and, in turn, from WLAN network  14  to PC  12 , at S 14 . PC  12 , upon receipt of the SIP invite, at S 15 , transmits an SIP 200 OK message to WLAN  14  acknowledging the acceptable media types, codecs, bit rate and IP address. The SIP 200 OK is transferred to IP network  18  through WLAN network  14 , at S 16 , and through IP network  18  to server  22 , at S 17 . Service server  22 , upon receipt of the SIP 200 OK from PC  12 , at S 18 , conveys an SIP acknowledge (ACK) to WLAN  14  and then to PC  12 , through WLAN network  14 , at S 19 , thereby completing the handoff of the real time session from the UE  32  to the WLAN—capable PC  12 . The communication of the real time session is thus established between PC  12  and a given source through WLAN network  14  and IP network  18 . The two-way communication is between WLAN network  14  and PC  12  at S 20 , IP network  18  at S 21 , and between IP network  18  and service server  22 , at S 22 . The user may terminate the session on WLAN  14 , at step S 23 .  
         [0025]      FIG. 5  shows the manner in which a handoff from a UE  32  to a PC  12  is triggered from the UMTS network  23 .  
         [0026]     Initially, it is assumed that the real time multi-media session, which may be voice over internet protocol (VoIP) or video, is presently taking place as represented by the two-way communication between UE  32  and UMTS network  23  as represented by step S 1 , two-way communication of this session between UMTS network  23  and IP network  18  shown at S 2  and the two-way communication between IP network  18  and service server  22  being shown at S 3 . It is assumed that the user wishes to perform a handoff from UE  32  to PC  12 . This is initiated by turning on PC  12 , at S 4 , so as to connect PC  12  to the WLAN network  14 , as shown at S 5 , and to the IP network  18 , as shown at S 6 .  
         [0027]     Once the connection with PC  12  is established and the user decides, at S 7 , to trigger a handoff to PC  12 , the UE  32 , at S 8 , sends an SIP message which may either be a new SIP handoff message or an SIP invite message with new information elements to identify the existing session. This message is transferred through network  23  to IP network  18 , at S 9 , and thereafter to service server  22 , at S 10 . Service server  22 , upon receipt of the SIP message, transmits an SIP 200 OK message to acknowledge the HO message which is conveyed, at S 11 , to IP network  18  which then conveys this message, at S 12 , to WLAN network  14 , which, in turn conveys the SIP 200 OK message to PC  12  at S 13 .  
         [0028]     PC  12 , at S 14 , responds to the SIP 200 OK message by sending an SIP acknowledge (ACK) to the service server  22  through WLAN network  14 , at S 14 , IP network  18 , at S 15  and then from IP network  18  to service server  22  at S 16 , thereby establishing the real time session, which originally included UE  32  as a participant, and is now handed off to PC  12  as shown at S 17 , S 18  and S 19 .  
         [0029]     Service server  22 , at S 20 , sends an SIP BYE to IP network which conveys it to UMTS network  23  at S 21 , which at S 22  conveys it to UE  32 . UE  32  sends an SIP  200  OK response to acknowledge the termination, which response is conveyed to UMTS network  23  at S 23  and is, in turn, conveyed to IP network  18  at S 24 , which, in turn, conveys the SIP 200 OK message to service server  22  at S 25 . Upon receipt of this message, the service server  22  sends an SIP acknowledge (SIP ACK) which is initially conveyed to IP network  18 , at S 26 , which transfers the SIP ACK message to UMTS  23 , at S 27 , UMTS network  23  transferring the SIP ACK message to UE  32 , at S 28 .