Abstract:
An apparatus and method for providing a seamless communication service in a mobile communication system. The method includes transmitting a first message to a base station when an IP subnet has been changed due to movement of the portable terminal, the first message including a Medium Access Control (MAC) address of the portable terminal, receiving IP address information from the base station, which can be used in a new IP subnet, and configuring a new IP address based on the received IP address information.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2005-0085849, entitled “Method And System For Configuring IP Address In A Mobile Communication System”, filed in the Korean Industrial Property Office on Sep. 14, 2005, the entire disclosure of which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a mobile communication system. More particularly, the present invention relates to a method and a system for configuring an Internet Protocol (IP) address in a mobile communication system.  
         [0004]     2. Description of the Related Art  
         [0005]     In the 4 th  Generation (4G) communication system, which is the next communication system, active research is being carried out in order to provide users with various Quality of Services (QoSs) having a transmission speed of about 100 Mbps. A representative of the 4G communication systems is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.  
         [0006]     Meanwhile, a mobile Internet service, that is, the Wireless Broadband (WiBro) communication system, has a standard which is compatible with the IEEE 802.16 communication system standard. The WiBro communication system provides a high speed data service through various types of Portable Subscriber Stations (PSSs) in an indoor or outdoor stationary environment or in a mobile environment of walking speed or middle/low speed (about 60 km/h). The WiBro communication system is currently implemented in connection with the Internet Protocol version 6 (IPv6), which is the next generation address system.  
         [0007]     Hereinafter, a network structure of a typical WiBro communication system will be described with reference to  FIG. 1 .  
         [0008]      FIG. 1  illustrates a network structure of a typical WiBro communication system.  
         [0009]     Referring to  FIG. 1 , the WiBro communication system includes a PSS  100  corresponding to mobile stations of the IEEE 82.16 communication system, a plurality of Radio Access Stations (RASs)  110 ,  120 ,  130 , and  140  corresponding to base stations of the IEEE 82.16 communication system, Access Control Routers (ACRs)  150  and  160  corresponding to base station controllers of the IEEE 82.16 communication system, an Authentication Authorization Accounting (AAA) server  170 , and a Home Agent (HA)  180 .  
         [0010]     The RAS is an element which is located at a terminal of a wire network and performs transmission/reception with the PSS through a wireless interface. The RAS supports the mobility of the PSS and manages and controls wireless resources. The ACR manages Medium Access Control (MAC) addresses, connection identifier and IP addresses of the PSSs in a lower network stage, controls the PSSs and RASs, performs IP packet routing and authentication/security tasks, and provides QoS to the PSS. The AAA  170  performs authentication, authorization, and accounting for the PSS. The HA  180  stores address information of the PSS.  
         [0011]     When the PSS  100  moves to a new RAS of ACR #2  160  which has an IP subnet different from that of RAS #1  110  of ACR #1  150  to which the PSS  100  currently belongs, the PSS  100  must perform a network reentry process. Hereinafter, the network reentry process will be described with reference to  FIG. 2 .  
         [0012]      FIG. 2  is a signal flowchart illustrating a network reentry process between a PSS and an RAS in a typical IEEE 802.16/WiBro communication system.  
         [0013]     Referring to  FIG. 2 , according to movement of the PSS  200  to a new RAS  250 , the PSS  200  receives a preamble of a downlink frame transmitted from the RAS  250  and acquires a system synchronization with the RAS  250 . Thereafter, the PSS  200  receives base station information broadcast by the RAS  250 , that is, base station information included in a Downlink Channel Descriptor (DCD) message, an Uplink Channel Descriptor (UCD) message, a Downlink MAP (DL-MAP) message, and an Uplink MAP (UL-MAP) message, thereby acquiring a downlink synchronization.  
         [0014]     Then, the PSS  200  transmits a ranging request (RNG_REQ) message to the RAS  250  at step  202 , and receives a ranging response (RNG_RSP) message, which is a response to the RNG_REQ, from the RAS  250 , thereby acquiring an uplink synchronization with the RAS  250  at step  204 .  
         [0015]     After completing the ranging process, the PSS  200  transmits a subscriber station basic capability request (SBC_REQ) message to the RAS  250  as step  206 , and receives a subscriber station basic capability response (SBC_RSP) message from the RAS  250  at step  208 , thereby completing a basic capability negotiation process.  
         [0016]     After completing the basic capability negotiation process, the PSS  200  transmits a Privacy Key Management (PKM) request (PKM_REQ) message to the RAS  250  at step  210 , and receives a PKM response (PKM_RSP) message from the RAS  250  at step  212 , thereby completing an authentication process.  
         [0017]     After completing the authentication process, the PSS  200  transmits a registration request (REG_REQ) message to the RAS  250  at step  214 , and receives a registration response (REG_RSP) message from the RAS  250  at step  216 , thereby completing the registration in the RAS  250 . Steps  202  to  216  correspond to the network reentry process performed in layer  2 , in which it takes a long time to complete the ranging, basic capability negotiation, authentication, and registration.  
         [0018]     After completing the process up to step  216 , the PSS  200  must perform an IP address auto-configuration process for IP connection at step  218 . According to the IP address auto-configuration, an IP address of a total of 128 bits is configured through a combination of a 64 bit prefix of an AR, which is included in a Routing Advertisement (RA) message periodically received by the PSS  200  from the RAS  250 , and an interface identifier (ID) of a mobile node with 64 bits, that is, a 64 bit MAC address. After completing the IP address auto-configuration, the PSS  200  performs Duplicate Address Detection (DAD) in order to determine if the 128 bit IP address is being used by another PSS in the same subnet. As a result of the DAD process, when the auto-configured IP address is not yet occupied, the PSS  200  performs signal transmission/reception by using the auto-configured IP address.  
         [0019]     As described above, when the PSS changes the subnet through movement, the PSS must sequentially perform a layer  2  network reentry process, an IP address auto-configuration process, and a DAD process. Therefore, the PSS cannot avoid interruption of communication until the network reentry process and the DAD process are completed. This problem undermines the object of the IEEE 802.16/WiBro communication system, which is to provide a seamless communication service.  
         [0020]     Accordingly, a need exists for a system and method for reducing interruption of communication during a network entry process.  
       SUMMARY OF THE INVENTION  
       [0021]     Accordingly, exemplary embodiments of the present invention have been made to address the above-mentioned problems occurring in the prior art, and an object of exemplary embodiments of the present invention is to provide an apparatus and method for providing a seamless communication service in a mobile communication system.  
         [0022]     In order to accomplish this object, a method is provided for configuring an Internet Protocol (IP) address during a network entry process by a portable terminal in a mobile communication system, the method comprising the steps of transmitting a first message to a base station when an IP subnet has been changed due to movement of the portable terminal, the first message comprising a Medium Access Control (MAC) address of the portable terminal, receiving IP address information from the base station, which can be used in a new IP subnet, and configuring a new IP address based on the received IP address information.  
         [0023]     In accordance with another aspect of exemplary embodiments of the present invention, a method is provided for allocating an Internet Protocol (IP) address during a network entry process by a base station in a mobile communication system, the method comprising the steps of receiving a ranging request message from a portable terminal, the ranging request message comprising a Medium Access Control (MAC) address of the portable terminal, determining with reference to the MAC address if the portable terminal has moved from another IP subnet, requesting a base station controller to send IP address information for use by the portable terminal when the portable terminal has moved from another IP subnet, receiving the IP address information from the base station controller, and transmitting the IP address information to the portable terminal.  
         [0024]     In accordance with another aspect of exemplary embodiments of the present invention, a method is provided for allocating an Internet Protocol (IP) address during a network entry process by a base station controller in a mobile communication system, the method comprising the steps of receiving an IP address information request message from a base station, the IP address information request message comprising a Medium Access Control (MAC) address of a portable terminal, determining an IP address for use by the portable terminal through a combination of the MAC address and a network prefix, and transmitting determined IP address information to the base station.  
         [0025]     In accordance with another aspect of exemplary embodiments of the present invention, a mobile communication system is provided for configuring an Internet Protocol (IP) address during a network entry process, the mobile communication system comprising a portable terminal, wherein the portable terminal transmits a first message to a base station when an IP subnet has been changed due to movement of the portable terminal, the first message comprising a Medium Access Control (MAC) address of the portable terminal, receives IP address information from the base station, which can be used in a new IP subnet, and configures a new IP address based on the received IP address information.  
         [0026]     In accordance with another aspect of exemplary embodiments of the present invention, a mobile communication system is provided for configuring an Internet Protocol (IP) address during a network entry process, the mobile communication system comprising a base station for receiving a ranging request message from a portable terminal, the ranging request message comprising a Medium Access Control (MAC) address of the portable terminal, determining with reference to the MAC address if the portable terminal has moved from another IP subnet, requesting a base station controller to send IP address information for use by the portable terminal when the portable terminal has moved from another IP subnet, receiving the IP address information from the base station controller, and transmitting the IP address information to the portable terminal. The mobile communication system further comprises a base station controller for receiving an IP address information request message from a base station, the IP address information request message comprising a Medium Access Control (MAC) address of a portable terminal, determining an IP address for use by the portable terminal through a combination of the MAC address and a network prefix, and transmitting determined IP address information to the base station. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The above and other objects, features and advantages of exemplary embodiments of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0028]      FIG. 1  illustrates a network structure of a typical WiBro communication system;  
         [0029]      FIG. 2  is a signal flowchart illustrating a network reentry process between a PSS and an RAS in a typical IEEE 802.16/WiBro communication system;  
         [0030]      FIG. 3  is a signal flowchart of a network reentry process between a PSS and an RAS in a mobile communication system according to an exemplary embodiment of the present invention;  
         [0031]      FIG. 4  is a flowchart of a process performed by the ACR in the network entry process in a mobile communication system according to an exemplary embodiment of the present invention;  
         [0032]      FIG. 5  is a flowchart of a process performed by the RAS in the network entry process in a mobile communication system according to an exemplary embodiment of the present invention; and  
         [0033]      FIG. 6  illustrates the format of an ICMP message according to an exemplary embodiment of the present invention. 
     
    
       [0034]     Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0035]     Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted for clarity and conciseness.  
         [0036]     Exemplary embodiments of the present invention provide a system and method for allocating an IP address during a network entry process in a mobile communication system to which the Internet Protocol version 6 (IPv6) is applied, for example, an IEEE 802.16 communication system and a WiBro communication system. Specifically, exemplary embodiments of the present invention provide for new messages exchanged between a Radio Access Station (RAS) and an Access Control Router (ACR), so that the RAS or ACR can more rapidly allocate an IP address by using the new messages when the subnet of a Portable Subscriber Station (PSS) is changed due to movement of the PSS.  
         [0037]      FIG. 3  is a signal flowchart of a network reentry process between a PSS and an RAS in a mobile communication system according to an exemplary embodiment of the present invention.  
         [0038]     Referring to  FIG. 3 , according to movement of the PSS  300  to a new RAS  320 , the PSS  300  receives a preamble of a downlink frame transmitted from the RAS  320  and acquires a system synchronization with the RAS  320 . Thereafter, the PSS  300  receives base station information broadcast by the RAS  320 , that is, base station information included in a Downlink Channel Descriptor (DCD) message, an Uplink Channel Descriptor (UCD) message, a Downlink MAP (DL-MAP) message, and an Uplink MAP (UL-MAP) message, thereby acquiring a downlink synchronization.  
         [0039]     Then, the PSS  300  transmits a ranging request (RNG_REQ) message to the RAS  320  at step  301 . The RAS  320  having received the RNG_REQ message determines if the subnet of the PSS  300  has been changed, due to the movement of the PSS  300  to the RAS  320 , by using a Medium Access Control (MAC) address of the PSS  300  included in the RNG_REQ message. When the subnet of the PSS  300  has been changed due to the movement of the PSS  300  to the RAS  320 , the RAS  320  transmits an Address Request (ADDR_REQ) message, which is newly provided by exemplary embodiments of the present invention, to the ACR  340  at step  303 . The ADDR_REQ message may comprise, for example, an Internet Control Message Protocol (ICMP) message, the format of which is shown in  FIG. 6 , but is not limited thereto. In yet other exemplary embodiments of the present invention, another type of message instead of the ICMP message can be used.  
         [0040]     After receiving the ADDR_REQ message, the ACR  340  scans IP addresses which can be allocated to the PSS  300  as step  305 . Specifically, the ACR  340  can search for an IP address of a total of 128 bits which is obtained through a combination of a 64 bit MAC address of the PSS  300  and a 64 bit prefix of the network. If the MAC address is being used by at least one PSS other than the PSS  300 , the ACR  340  can search for the 128 bit IP address by using a MAC address which is not being used in the current network.  
         [0041]     The ACR  340  inserts a detected IP address into an Address Response (ADDR_RSP) message which is newly provided by exemplary embodiments of the present invention, and transmits the ADDR_RSP message to the RAS  320  at step  307 . The ADDR_RSP message may comprise, for example, an ICMP message, the format of which is shown in  FIG. 6 , but is not limited thereto.  
         [0042]     The RAS  320  recognizes the IP address included in the ADDR_RSP message, inserts the IP address into a ranging response (RNG_RSP) message, and transmits the RNG_RSP message to the PSS  300  at step  309 . At this time, the RAS  320  may insert the IP address into a registration response (REG_RSP) message instead of the RNG_RSP message, and may transmit the REG_RSP message to the PSS  300 .  
         [0043]     After receiving the RNG_RSP message, the PSS  300  can recognize the IP address and perform an IP address auto-configuration. Thereafter, the PSS  300  performs a basic capability negotiation process at steps  311  and  313  by using a subscriber station basic capability request (SBC_REQ) message and a subscriber station basic capability response (SBC_RSP) message, and performs an authentication process at steps  315  and  317  by using a Privacy Key Management (PKM) request (PKM_REQ) message and a PKM response (PKM_RSP) message, in substantially the same way as in step  206  to  212  of  FIG. 2 .  
         [0044]     When the RAS  320  has received a registration request (REG_REQ) message from the PSS  300  at step  319 , the RAS  320  may transmit an ADDR_REQ message to the ACR  340  at step  321 . Then, the ACR  340  performs steps  323  and  325  in substantially the same way as in steps  305  and  307 . Then, the RAS  320  transmits the REG_RSP message to the RAS  320  at step  327 . As described above, the transmitted REG_RSP message may carry the IP address inserted by the RAS  320 .  
         [0045]     As described above, the PSS according to exemplary embodiments of the present invention can perform the IP address configuration during the network entry process. Therefore, the PSS need not perform the Duplicate Address Detection (DAD) process and thus can reduce a communication interruption time as long as that necessary for the DAD process, thereby minimizing the communication interruption time.  
         [0046]      FIG. 4  is a flowchart of a process performed by the ACR in the network entry process in a mobile communication system according to an exemplary embodiment of the present invention.  
         [0047]     Referring to  FIG. 4 , the ACR receives the ADDR_REQ message for requesting an IP address of the PSS from the RAS in step  402 . Then, in step  404 , the ACR determines if a MAC address of the PSS conflicts with a MAC address of another PSS. As a result of the determination, the ACR proceeds to step  405  when the MAC address of the PSS conflicts with a MAC address of another PSS, and proceeds to step  406  when the MAC address of the PSS does not conflict with a MAC address of another PSS.  
         [0048]     In step  405 , the ACR configures a 128 bit IP address by using a MAC address which is not being used in the subnet, and then proceeds to step  408 . In step  406 , the ACR configures an IP address through a combination of a network prefix and a MAC address of the PSS requested the IP address, and then proceeds to step  408 . In step  408 , the ACR transmits an ADDR_RSP message including the configured IP address to the RAS.  
         [0049]      FIG. 5  is a flowchart of a process performed by the RAS in the network entry process in a mobile communication system according to an exemplary embodiment of the present invention.  
         [0050]     Referring to  FIG. 5 , the RAS receives the RNG_REQ message in step  502  and then proceeds to step  504 . The transmitted RNG_REQ message includes the MAC address of the PSS. Then, in step  504 , the RAS determines if the PSS has moved from another IP subnet. Then, the RAS proceeds to step  508  when the PSS has moved from another IP subnet and proceeds to step  506  when the PSS has not moved from another IP subnet.  
         [0051]     In step  506 , the RAS performs the ranging, basic capability negotiation, authentication, and registration with the PSS.  
         [0052]     In step  508 , the RAS requests the ACR to send an IP address for the PSS. Then, in step  510 , the RAS receives an IP address from the ACR as a response to the request for the IP address. Then, in step  512 , the RAS transmits the IP address information to the PSS.  
         [0053]      FIG. 6  illustrates the format of an ICMP message according to an exemplary embodiment of the present invention.  
         [0054]     The ICMP message shown in  FIG. 6  is used for the ADDR_REQ message and the ADDR_RSP message. The ICMP message has a size totaling four bytes, and comprises one byte of type field, one byte of code field, two bytes of checksum field, and a message body. The message body may comprise a MAC address of the PSS or an IP address to be used by the PSS. For example, when the ICMP message is used as the ADDR_REQ message, the ACR, upon receiving an ICMP message having a code field recorded by a value of “1,” recognizes that the RAS is requesting an IP address. In contrast, when the ICMP message is used as the ADDR_RSP message, the RAS, upon receiving an ICMP message having a code field recorded by a value of “2,” recognizes that the ICMP message received by the RAS contains a response to the request for the IP address. When the ACR reports that the MAC address of the PSS is specific, the message body of the ADDR_RSP message is filled with “0” which contains no information. In the opposite case, the message body of the ADDR_RSP message is filled with a specific address which is not found in the system.  
         [0055]     According to exemplary embodiments of the present invention as described above, a PSS is allocated a new IP address during a network entry process and need not perform a DAD process in a WiBro or IEEE 802.16 communication system. Therefore, exemplary embodiments of the present invention can reduce communication interruption time by a period as long as that caused by the DAD process, thereby minimizing the communication interruption time.  
         [0056]     While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.