Abstract:
The invention discloses a new protocol to minimize data loss, reduce overhead transmissions on the system, reduce time delays and signal interruption during a handover in a Mobile IP system. Prior art Mobile IP systems transfer policy and charging rules for a particular mobile user device from a server to a gateway after the handover occurs. The invention allows for the transfer of the policy and charging rules during the handover procedure so that the system does not need to wait on a subsequent transmission of the policy and charging rules in order to process the transmissions sent by or to the mobile user, which results in minimized data loss, reduced overhead, and reduced time delays and signal interruption.

Description:
RELATED APPLICATION DATA 
     This application is related to U.S. Provisional Patent Application Ser. No. 60/764,929 filed on Feb. 3, 2006, and priority is claimed for this earlier filing under 35U.S.C. §120.The Provisional Patent Application is also incorporated by reference into this utility patent application. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     An improved method and system for transferring policy and charging rules during an MIP handover. 
     BACKGROUND OF THE INVENTION 
     The Internet, like so many other high tech developments, grew from research originally performed by the United States Department of Defense. In the 1960s, the military had accumulated a large collection of incompatible computer networks. Computers on these different networks could not communicate with other computers across their network boundaries. 
     In the 1960s, the Defense Department wanted to develop a communication system that would permit communication between these different computer networks. Recognizing that a single, centralized communication system would be vulnerable to attacks or sabotage, the Defense Department required that the communication system be decentralized with no critical services concentrated in vulnerable failure points. In order to achieve this goal, the Defense Department established a decentralized standard communication protocol for communication between their computer networks. 
     A few years later, the National Science Foundation (NSF) wanted to facilitate communication between incompatible network computers at various research institutions across the country. The NSF adopted the Defense Department&#39;s protocol for communication, and this combination of research computer networks would eventually evolve into the Internet. 
     INTERNET PROTOCOLS 
     The Defense Department&#39;s communication protocol governing data transmission between different networks was called the Internet Protocol (IP) standard. The IP standard has been widely adopted for the transmission of discrete information packets across network boundaries. In fact, the IP standard is the standard protocol governing communications between computers and networks on the Internet. 
     The IP standard identifies the types of services to be provided to users and specifies the mechanisms needed to support these services. The IP standard also specifies the upper and lower system interfaces, defines the services to be provided on these interfaces, and outlines the execution environment for services needed in the system. 
     THE IP-BASED MOBILITY SYSTEM 
     In a typical Internet-based communication scenario, data is transmitted from an originating communication device on a first network across a transmission medium to a destination communication device on a second network. After receipt at the second network, the packet is routed through the network to a destination communication device using standard addressing and routing protocols. Because of the standard protocols in Internet communications, the IP protocol on the destination communication device decodes the transmitted information into the original information transmitted by the originating device. 
     The Internet protocols were originally developed with an assumption that Internet users&#39; communication devices would be connected to a single, fixed network. With the advent of cellular wireless communication systems using mobile communication devices (mobile units), the movement of Internet users within a network and across network boundaries has become common. Because of this highly mobile Internet usage, the implicit design assumption of the Internet protocols (e.g. a fixed user location) is violated by the mobility of the user. 
     In an IP-based mobile communication system, the mobile communication device (e.g. cellular phone, pager, computer, etc.) can be called a User Equipment or mobile station. Typically, a mobile station maintains connectivity to its home network while operating on a visited network. The mobile station will remain associated with its home network for IP addressing purposes and will have information routed to it by routers located on the home and visited networks. 
     In an IP-based mobile communication system, the mobile communication device (e.g. cellular phone, pager, computer, etc.) can be called User Equipment. Typically, User Equipment maintains connectivity to its home network through a foreign network. The User Equipment will always be associated with its home network for IP addressing purposes and will have information routed to it by routers located on the home and foreign networks. The routers can be referred to by a number of names including Home Agent, Home Mobility Manager, Home Location Register, Foreign Agent, Serving Mobility Manager, Visited Location Register, and Visiting Serving Entity. 
     PACKET-BASED COMMUNICATION SYSTEMS 
     Telecommunication networks are complex networks used to establish connections between two or more telecommunication devices. Frequently, the devices involved with a telecommunications call or connection are referred to as the originating device and the terminating device. The user typically enters an identifying number into the originating device of the terminating device to which a call is to be placed. The network responds to entry of the identifying number of the terminating device and performs a call setup procedure that establishes, among other things, a connection between the originating device and the terminating device using IP addressing. Call data, voice or multimedia, is then routed between the two devices according the IP addressing assigned to each device. 
     In Internet Protocol (IP) networks, the communication process is very different from prior conventional telecommunication systems. In an IP network communication, there is no open switched connection established between the caller and recipient devices. The information being transmitted between the caller and recipient devices is broken into packets of data, and each packet of data is transmitted to the recipient device in pieces. The data packets individually contain routing information to direct each packet to the recipient device. These packets are then reassembled into a coherent stream of data at the recipient device. 
     Voice and data transmitted according to the IP packet standard is the evolving and most current communication protocol for cellular telephone communication. With this migration to the IP standard and miniaturization of computer chip technology with dramatic increases in clock speeds, computational power, and memory storage has come increasingly sophisticated services such as email access, streaming video and audio data transfers, instant messaging, text messaging, multimedia applications, picture messaging, 
     Internet website access, e-commerce applications, games and other services. Cell phones have accordingly evolved from relatively crude devices limited to telephony communication to near mini-computers with operating features and capabilities equal to if not superior to early personal computers. 
     A typical cellular communication system is comprised of multiple cell sites, each covering an intended geographic region. Each of the cell sites can be assigned an address for routing information packets, and each User Equipment can be assigned an address for their physical connectivity to the cell site. 
     Each cell site supports voice and data communication to the linked User Equipment present within that geographic area. A wireless communication link is maintained by a transceiver at or very near the center of the cellular coverage area. The transceiver is coupled to a base station transceiver substation which is coupled to a base station controller, with controls the packet transmissions within the cell site area. The base station controller is also coupled to a mobile switching center, which routes calls handled by the base station controller and base transceiver station to a public switched telephone network or a packet data service node interface with the Internet. The gateway described herein is equivalent to the base station controller and packet data service node in a CDMA network. 
     Information packets on the communication system are processed by the base station controller for transmission to the public switched telephone network or the Internet. The base station controller processes the information packets for transmission to the public switched telephone network, the Internet, or User Equipment (“UE”). As User Equipment moves across cellular boundaries, it changes its connectivity and its connectivity address. 
     Routers on the communication network have to be updated with this new connectivity address so that information packet can continue to be properly routed. The address used for routing can be a single IP address, a combination of an IP address and a connectivity address, or some other similar addressing scheme providing packet routing data on the communication network corresponding to the physical connectivity of the User Equipment. 
     CDMA SYSTEMS 
     Code Division Multiple Access (CDMA) is an evolving generation communication system standard for wireless communication systems that can transmit multimedia services using the packet-based Internet protocol. These CDMA mobile communication systems support multimedia telecommunication services delivering voice (VoIP) and data, to include pictures, audio, video, streaming video, messaging, and other multimedia information over mobile wireless connections. As used herein, “CDMA” encompasses code division multiple access technologies being developed by Third Generation Partnership Project (“3GPP”) and the Third Generation Partnership Project 2 (“3GPP2”) bodies, as well as other CDMA technologies. 
     As the capability of the various communication standards have improved, there has been an increasing need for high-speed transmissions and increased user capacity. New CDMA protocols and packet air interface have been developed that offer improvements over earlier CDMA systems by implementing high-speed shared-traffic packet data channels on the forward air-link connection as well as other improvements in data signal flow. Other standards are evolving that also make use of the shared packet channel and multiplex packet communication for high-speed data and voice communication. 
     On the CDMA standard, User Equipment or Access Terminals (ATs), roam within and across cellular communication sites. Each of the cells possesses one or more transceivers coupled to a Base Transceiver Station (BTS) onto the communication network. The BTSs are in turn coupled to an Access Network. 
     UE can be physically located anywhere on the network or sub-network, and its routing address data will change and require updating on other nodes. As UE migrates across cellular borders or across network boundaries, its connection to its Home Network changes. 
     Wireless IP networks handle the mobile nature of UE with handover procedures designed to update the communication network and sub-network with the location of the User Equipment for packet routing purposes. Because User Equipment can move within sub-networks and between networks, handover procedures are needed to insure that packets are continually routed without delays or interruption to the recipient UE as it moves from one network to another or from one sub-network to another. 
     As the CDMA standards evolve, newer methods and enhancements to transmitting packets on the network are being developed and deployed. There is a currently a need for an improved handover method that is also compliant with the standardized protocol interface between the base station and packet-switching equipment (PDSN, PCF), as well as other standards. 
     SUMMARY OF THE INVENTION 
     The invention discloses a new protocol to minimize data loss, reduce overhead transmissions on the system, reduce time delays and signal interruption during a handover in a Mobile IP system. Current Mobile IP systems transfer policy and charging rules for a particular mobile user device from a server to a gateway after the handover occurs. Waiting on the transfer of the policy and charging rules after a handover, however, can cause an interruption in the signal flow to and from the mobile user. 
     The invention allows for the transfer of the policy and charging rules during the handover procedure so that the system does not need to wait on a subsequent transmission of the policy and charging rules in order to process the transmissions sent by or to the mobile user, which results in minimized data loss, reduced overhead, and reduced time delays and signal interruption. A confirmation transmission of the policy and charging rules for a UE can be sent after the handover occurs. This invention will result in less dropped packets and reduced noticeable interruptions in data sessions with real time characteristics, such as Voice over IP applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements and in which: 
         FIG. 1  is a schematic diagram of the functional elements of a wireless communication network based on an implementing architecture for a CDMA system; 
         FIG. 2  is a prior art system showing the high level overview of architecture of the handover of UE; 
         FIG. 3  is a schematic diagram of the functional elements of a wireless communication network based on an implementing architecture for a CDMA system; 
         FIG. 4  is the system showing the high level overview of architecture of the handover of UE using the present invention; 
         FIG. 5  is a message flow for handover for a predictive handover; and, 
         FIG. 6  is a message flow for handover for a reactive handover. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the typical IP-based cellular communication system components utilizing the invention. Referring to  FIG. 1 , gateway 1  130  and base transceiver station  115  are coupled by connector  110 . This cell site initially supports the wireless communication with User Equipment  105 . 
     As the User Equipment  105  moves through the Visited Network  100 , the User Equipment needs to be handed over to a new cellular site, which included gateway 2  135  coupled to a base transceiver station  125  via connector  120 . Gateway 1  130  is coupled to gateway 2 and separately connected to Home Agent  175  via connector  140 . Gateway 2  135  is coupled to Home Agent  175  via connector  145 . Gateway 1  130  and gateway 2  135  are equivalent to the base station controller and packet data service node in a CDMA network. 
     The Home Agent  175  located on Home Network  150 , which is coupled to the Internet  170  via connector  165 . The Home Agent  175  is also connected to IMS Service  155  via connector  160 . 
     Policy and charging rules define, per subscriber, what types of traffic are allowed, what Quality of Service is provided, and how much it costs the subscriber to send and receive transmissions. When the UE  105  initially couples to the gateway 1  130 , the Home Network  150  sends policy and charging rules to the gateway 1  130 . That gateway 1  130  enforces that policy and charging rules on behalf of the Home Network  150  while the UE  105  is associated with gateway 1  130  on the Visited Network  100 . 
     When the UE  105  moves to gateway 2  135 , policy and charging rules are needed on gateway 2  135  to enforce the rules for the transmission of packets to and from the UE  105 . In the prior art system, the policy and charging rules are transmitted to gateway 2  135  after the handover of the UE occurs to gateway 2  135 . The transmission of voice packets and data packets may be blocked until policy and charging rules are obtained on gateway 2  135 , even if it only takes a short time period to receive those rules after the handover of the UE  105  to gateway 2  135 . The present invention allows the policy and charging rules to be placed on the destination gateway 2  135  during the handover process to avoid interruption of the voice or data connection. By receiving policy and charging rules during the handover routine, the transmission of data and voice packets is not blocked waiting for the receipt of the policy and charging rules. The invention is particularly useful in avoiding interruption of signal in transmission types that approximate real-time criteria, such as VoIP transmissions. 
     As shown in  FIG. 2 , the high level architecture is shown for a system where there is a proxy P-CSCF  283  in the IMS system  299 . The IMS  299  is coupled to Home Network policy and charging rules functions H-PCRF  287  through connector  285  and Rx  280 . The H-PCRF  287  serves as an anchor point for policy and charging control purposes. 
     The H-PCRF  287  is coupled to the Mobile IP Home Agent  293  via connector  290  and Gx  277 . The MIP HA  293  possesses the policy and charging enforcement function PCEF  295 . 
     The Visited policy and charging rules function 1  235  (V-PCRF 1) is coupled to the H-PCRF  287  through connection  273  and Gw on line  273 . The V-PCRF 1  235  is coupled to gateway 1  250  via connector  245  and Gx  240 . Gateway 1  250  includes policy and charging enforcement function 1 thereon. When UE  200  is associated with gateway 1  250 , the policy and charging rules are transmitted to the gateway 1 by the H-PCRF  287 . 
     The Visited policy and charging rules function 2  220  (V-PCRF 2) is coupled to the H-PCRF  287  through connection  255  and Gw  265  on line  255 . The V-PCRF2  220  is coupled to gateway 2  230  via connector  215  and Gx on connector  215 . Gateway 2  230  includes policy and charging enforcement function PCEF 2  225  thereon. When the handover of UE  200  is initiated, UE leaves the gateway 1 service area and proceeds to gateway 2. Sometimes, a bidirectional tunnel is established temporarily for forwarding of packets to the UE  200  when it moves to the new gateway 2. 
     After UE  200  arrives at the gateway 2  230  service area, the UE receives a new care-of address from the gateway 2  230 . It is possible that gateway 1  250  may tunnel packets to gateway 2  230 . If not, it is also possible that the gateway 1  250  will buffer packets, but these packets may have to be discarded if no tunnel is established. The UE  200  registers its new care-of address with the MIP Home Agent  297 , so the packets addressed to UE  200  may be forwarded to gateway 2  230  for transmission to UE  200 . Any temporary bi-directional tunnel can be removed at this point, and data and voice packets can be transmitted and received by UE  200  at this point through its gateway 2 connection. 
     Looking at  FIG. 2 , the policy and charging rules function does not possess the policy and charging rules for UE when the handover occurs or when the care-of address gets registered, and the gateway  230  may refuse to transmit data and voice packets addressed to UE or sent from UE without the appropriate policy and charging rules. The delays in receiving the most appropriate rules for the policy and charging enforcement function  295  may result in delays or lost data and voice packets. 
     The gateway 2  230  notifies the policy and charging rules function V-PCRF 2  220  about the presence of UE  200  on the gateway 2  230 , and V-PCRF 2  220  retrieves policy and charging rules information for the UE  200  from H-PCRF  287  and forwards the policy and charging information to gateway 2  230  for operation on data packets transmitted and received by UE  200 . While waiting for the receipt of the rules, there is a possibility that data packets will be lost and discarded, which will result in an interruption of service until the policy and charging information is received and applied to the system. Delay sensitive devices and services (e.g. VoIP) are especially susceptible to these interruptions of packet transmissions. 
     In summary, the prior art supports the system where the UE  200  receives a new care-of address from gateway 2. Then, the policy and charging rules are transferred to the gateway 2 by the H-PCRF  287  after that address is established. After handover but before the policy and charging rules are transferred to the new gateway 2, the transmission of voice and data to UE  200  can be interrupted or delayed. 
     The H-PCRF  287  provides an anchor point for policy and charging rules purposes. UE network access identifier (NAI) is used for PCRF addressing V-PCRF  235  to discover the H-PCRF  287 . Although the scenario shown in the application shows a roaming function, the concept is applicable and useful in non-roaming scenarios. 
     The temporary tunnel can be seen in  FIG. 3 , where the Mobile IP Home Agent  350  is coupled to the Previous Access Router  300  and New Access Router  310  via connector  360 . Connector  360  is also known as an L3 interface. The Previous Access Router  300  is coupled to the New Access Router  310  via tunnel  340 . Previous Access Router  300  is equivalent to gateway 1  250  shown in a prior figure. Likewise, New Access Router  310  is equivalent to gateway 2  230  shown in a prior figure. When the UE moves from L2 Net A  320  to L2 Net B  330 , the UE registers its new care-of address with the Mobile IP Home Agrent  350  through New Access Router  310 . Until the policy and charging rules can be transferred to the New Access Router  310 , the tunnel  340  permits a forwarding of data and voice packets, but there is not complete reliability in the use of the tunnel. 
     As shown in  FIG. 4 , the high level architecture of the present invention is shown for a system where the proxy CSCF  485  in the IMS system  499 . The IMS  499  is coupled to Home Network policy and charging rules functions H-PCRF  489  through connector  487  and Rx thereon. The H-PCRF  489  serves as an anchor point for policy and charging control purposes. 
     The H-PCRF  489  is coupled to the Mobile IP Home Agent  495  via connector  490  and Gx thereon. The MIP HA  495  possesses the policy and charging enforcement function PCEF  493 . 
     The Visited policy and charging rules function 1  435  (V-PCRF 1) is coupled to the H-PCRF  489  through connection  473  and Gw on line  473 . The V-PCRF 1  435  is coupled to gateway 1  450  via connector  440  and Gx thereon. Gateway 1  450  includes policy and charging enforcement function PCEF 1  445  thereon. When UE  400  is associated with gateway 1  450 , the policy and charging rules are transmitted to the gateway 1  450  by the H-PCRF  489 . The policy &amp; enforcement rules functions are coupled to the gateway 1  450  from the MIP Home Agent  495  via connector  480  and Gi connected thereon. 
     The Visited policy and charging rules function 2  415  (V-PCRF 2) is coupled to the H-PCRF  489  through connection  470  and Gw thereon. The V-PCRF 2  415  is coupled to gateway 2  430  via connector  420  and Gx on connector  420 . Gateway 2  430  includes policy and charging enforcement function PCEF 2  425  thereon. 
     When the handover according to the present invention is initiated, UE  400  leaves the gateway 1  450  service area and proceeds to gateway 2  430 . Gateway 1  450  initiates a fast handover of UE  400  to gateway 2  430 , and during that handover, gateway 1  450  sends the policy and charging information for the UE  400  to gateway 2  430  as part of the exchange of information  455  between the gateways in the handover procedure. Also as part of the exchange of rules information and other information, a tunnel is set up between gateway 1 and gateway 2 to forward packets. 
     UE  400  receives its care-of address from the gateway 2  430 . It is possible that gateway 1  450  may tunnel packets to gateway 2  430 . If not, it is also possible that the gateway 1  450  will buffer packets, but these packets may have to be discarded without an existing tunnel. The UE  400  registers its new care-of address with the MIP Home Agent  495 , so the packets addressed to UE  400  may be forwarded to gateway 2 for transmission to UE  400 . Any temporary bi-directional tunnel can be removed at this point, and data and voice packets can be transmitted and received by UE  400  at this point through its gateway 2 connection. 
     Looking at  FIG. 4 , because the policy and charging rules functions are initially transferred to the gateway 2 during the initial exchange of information during the handover process, there is no delay or interruption in the data and voice transmissions sent by or to gateway 2  430  for UE  400 . The gateway 2  430  notifies the V-PCRF 2  415  that the UE  400  is present on gateway 2  430 , and the V-PCRF 2  415  retrieves the latest policy and rules information from the H-PCRF  489  via connection  470 . The latest policy and charging rules information received from PCRF  489  confirms the prior information sent to gateway 2  430  if the same, and if not, the confirmation policy and charging rules received from H-PCRF  489  takes precedence over the prior policy and charging rules information received from gateway 1  450  during the fast handover exchange of information. 
     In this manner, there is no delay in receiving the policy and charging rules information to be applied to the UE  400 , and there should not be any lost data or voice packets caused by delays in the receipt of the policy and charging rules. The new gateway will have policy and charging information for UE  400 , as initially transmitted to the new gateway during the handover procedure, which can be confirmed later by the receipt of policy and charging information from H-PCRF  489 . 
     In  FIG. 5 , a message flow is shown for a predictive fast handover between the Mobile Node  500 , the Previous Access Router  510  and the next Access Router  520 . The Router Solicitation Proxy Advertisement  525  message is sent from Mobile Node  500  to Previous Access Router  510 , and the Proxy Router Advertisement  530  is sent back to the Mobile Node  500 . The Fast Binding Update  535  message is sent from the Mobile Node  500  to the Previous Access Router  510 , and the Handover Initiation  540  message is sent to the Next Access Router  520 . The Handover Initiation Message  540  may contain the policy and charging rules information (PCC) set forth therein. A tunnel can be set up between the Prior Access Router  510  and the Next Access Router  520  to assist with the transfer of data and voice packets. 
     The Handover Initiation Acknowledgement message  545  is sent back from the Next Access Router  520  to the Previous Access Router  510 . In that Acknowledgement message  545 , there is a request for a transmission of the latest policy and charging rules information if the policy and charging rules information (PCC) was not sent in the Handover Initiation Message  540 . The Previous Access Router  510  sends out 
     Fast Binding Acknowledgement messages  555  and  550  to the Next Access Router and the Mobile Node, respectively. The latest policy and charging rules are transmitted in message  555  back to the Next Access Router  520  if the policy and charging rules information (PCC) was not sent in the Handover Initiation Message  540 . 
     The Mobile Node  500  disconnects  575  the connection to the Previous Access Router  510 , and packets are forwarded to the Next Access Router at  560  via a tunnel. The Next Access Router  520  is connected  580  to the Mobile Node  500 , and the Fast Neighbor Advertisement FNA  565  is sent from Mobile Node  500  to Next Access Router  520 . Packets are then delivered without the need for a tunnel  560 , and with the latest policy and charging information, at  570  according to the teachings of the present invention using a predictive handover protocol. 
     In  FIG. 6 , a message flow is shown for a reactive handover between the Mobile Node  600 , the Previous Access Router  610  and the next Access Router  620 . The Router Solicitation Proxy Advertisement  630  message is sent from Mobile Node  600  to Previous Access Router  610 , and the Proxy Router Advertisement  640  is sent back to the Mobile Node  600 . 
     The Mobile Node  600  is disconnected  695  from the Previous Access Router  610  and connected  699  to the Next Access Router  620  through the Fast Neighbor Advertisement  650 . The Fast Binding Update message  660  is sent from the Next Access Router  620  to the Prior Access Router  610  with a request for the policy and charging rules, and the Prior Access Router  610  responds with the policy and charging rules in the Fast Binding Acknowledgement message  670  sent from the Previous Access Router  610  to the Next Access Router  620 . Packets are then delivered to the Next Access Router  620 , and packets are delivered  695  to the Mobile Node  600 , with the latest policy and charging information. 
     While the invention has been particularly shown and described with respect to preferred embodiments, it will be readily understood that minor changes in the details of the invention may be made without departing from the spirit of the invention. Having described the invention,