Abstract:
A broadband wireless communication system is provided. An apparatus for an information server (IS) comprises an event module for determining whether updating the network information of at least one access network (AN) is needed, a generator module for generating at least one Information_Get_Request packet for requesting the network information of the at least one AN when the updating is needed, a communication module for transmitting at least one Information_Get_Request packet to the at least one AN, and a database (DB) module for storing network information within an Information_Get_Response packet received from the at least one AN.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Oct. 2, 2007 and assigned Serial No. 2007-99376, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a wireless communication system. More particularly, the present invention relates to an apparatus and method for supporting vertical handover in a wireless communication system. 
     BACKGROUND OF THE INVENTION 
     In accordance with the progress of wireless communication techniques, wireless communication systems having various standards have been being developed. Wireless communication systems are designed to support user terminals accessing a backbone network through an air channel. That is, from the point of view of the end-to-end elements which are a service user and a service provider, it does not matter which standard is employed by a wireless communication system in using contents. Accordingly, a technique for maintaining a satisfactory condition of an air connection by enabling the performance of a seamless handover between different networks of different mediums is being studied. 
     There exists the Institute of Electrical and Electronics Engineers (IEEE) 802.21 Media Independent Handover (MIH) as a typical technique for handover between different networks. The handover between different networks is called a vertical handover. According to the MIH, event service, command service and information service are defined for vertical handover. The event service denotes recognizing change of physical information in air access link, the command service denotes handling control commands for the vertical handover, and the information service denotes managing network information on different networks. Accordingly, a mobile terminal (MT) gets proper network information by using services as stated above, and performs the vertical handover. 
     Network information for the vertical handover is provided by an information server (IS), which is a separate entity in a wireless communication system. The IS manages network information on a plurality of networks, and provides the network information upon a request from the MT. IEEE 802.21 MIH standard defines a list of the network information, which has to be maintained at the IS. However, ways for getting, maintaining, updating and managing the network information and a structure of the IS for the ways are not defined. Therefore, there is a need to provide the structure of the IS for supporting vertical handover in a practical wireless communication environment. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and method for supporting vertical handover in a wireless communication system. 
     Another aspect of the present invention is to provide an apparatus and method for providing network information for a vertical handover. 
     In accordance with an aspect of the present invention, an apparatus for an Information Server (IS) in a wireless communication system is provided. The apparatus includes an event module for determining whether updating the network information for at least one access network (AN) is needed, a generator module for generating at least one Information_Get_Request packet for requesting the network information for the at least one AN when updating is needed, a communication module for transmitting at least one Information_Get_Request packet to the at least one AN, and a database (DB) module for storing network information within an Information_Get_Response packet received from the at least one AN. 
     In accordance with another aspect of the present invention, an operating method for an IS in a wireless communication system is provided. The method includes determining whether updating the network information for at least one AN is needed, generating at least one Information_Get_Request packet for requesting the network information for the at least one AN when updating is needed, transmitting at least one Information_Get_Request packet to the at least one AN, and storing network information within an Information_Get_Response packet received from the at least one AN. 
     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIGS. 1A and 1B  illustrate an example of a packet structure for getting and providing network information in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIG. 2  is a block diagram of an information server (IS) in a wireless communication system according to an exemplary embodiment of the present invention; 
         FIGS. 3A to 3E  are flowcharts illustrating operating processes of each module within the IS in a wireless communication system according to an exemplary embodiment of the present invention; and 
         FIG. 4  is a flowchart illustrating operating processes of the IS in a wireless communication system according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 through 4 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. 
     Hereinafter, a technique for providing network information which is needed for a vertical handover will be described. Hereinafter, an entity which provides the network information for the vertical handover will be addressed ‘Information Server (IS)’. 
     The IS according to an exemplary embodiment of present invention stores network information about a plurality of access networks (ANs), and updates the network information when needed. For instance, the network information which is managed by the IS includes items shown in Table 1 below. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 IE type 
                 IE 
                 description 
               
               
                   
               
             
             
               
                 General 
                 TYPE_IE_NETWORK_TYPE 
                 Available network link type 
               
               
                 IEs 
                 TYPE_IE_OPERATOR_IDENTIFIER 
                 Operator identifier of 
               
               
                   
                   
                 access network/core network 
               
               
                   
                 TYPE_IE_SERVICE_PROVIDER_IIDENTIFIER 
                 Identifier of service provider 
               
               
                 Access 
                 TYPE_IE_ACCESS_NETWORK_IDENTIFIER 
                 Identifier of access network 
               
               
                 Network 
                 TYPE_IE_NETWORK_SYSTEM_ID 
                 System identifier used by 
               
               
                 Specific 
                   
                 network 
               
               
                 IEs 
                 TYPE_IE_ROAMING_PARTNERS 
                 Roaming partner 
               
               
                   
                 TYPE_IE_COST 
                 Cost 
               
               
                   
                 TYPE_IE_NETWORK_SECURITY 
                 Security character in link 
               
               
                   
                   
                 layer 
               
               
                   
                 TYPE_IE_NETWORK_QOS 
                 QoS character in link layer 
               
               
                   
                 TYPE_IE_NETWORK_DATA_RATE 
                 Minimum/Maximum data rate 
               
               
                   
                   
                 in link layer 
               
               
                   
                 TYPE_IE_NETWORK_IP_CONFIG_METHODS 
                 Available IP configuration 
               
               
                   
                   
                 method 
               
               
                   
                 TYPE_IE_NETWORK_CAPABILITIES 
                 Bitmap for capabilities 
               
               
                   
                   
                 of access network 
               
               
                 PoA 
                 TYPE_IE_POA_ADDRESS 
                 MAC address of PoA 
               
               
                 Specific 
                 TYPE_IE_POA_LOCATION 
                 Location of PoA 
               
               
                 IEs 
                 TYPE_IE_POA_DATA_RATE 
                 Minimum/Maximum data rate of 
               
               
                   
                   
                 PoA 
               
               
                   
                 TYPE_IE_POA_CHANNEL_RANGE 
                 Channel range/parameter of 
               
               
                   
                   
                 PoA 
               
               
                 PoA 
                 TYPE_IE_SUBNET_INFORMATION 
                 Subnet information of PoA 
               
               
                 Specific 
                 TYPE_IE_POA_IP_CONFIG_METHODS 
                 IP configuration method 
               
               
                 Higher 
                   
                 supportable by PoA 
               
               
                 Layer 
                 TYPE_IE_POA_CAPABILITIES 
                 Bitmap for capabilities of PoA 
               
               
                 Service 
                 TYPE_IE_POA_IP_ADDRESS 
                 IP address of PoA 
               
               
                 IEs 
               
               
                 Other 
                 Vendor Specific IEs 
                 Vender specific IE 
               
               
                 IEs 
               
               
                   
               
             
          
         
       
     
     In Table 1, the Point of Access (PoA) denotes a node which connects to a mobile terminal (MT) through air channel, and the roaming partner denotes a list of handover-able network candidates. 
     The IS gets, manages and provides the network information as shown in Table 1 by exchanging Media Independent Handover (MIH) packets with a Media Independent Handover Function (MIHF) of the MT and an MIHF of the AN. 
       FIGS. 1A and 1B  illustrate an example of a packet structure for getting and providing network information in a wireless communication system according to an exemplary embodiment of the present invention. 
       FIG. 1A  illustrates a structure of an Internet Protocol (IP) packet, and the IP packet consists of an IP header and data. The IP header includes various fields. If the IP packet is an MIH packet, a protocol field  110  among the various fields is set to ‘IPPROTO_MIH’. The data includes an MIH frame, and the MIH frame consists as shown in  FIG. 1B . 
     The MIH frame includes an MIHF fixed header and an MIHF variable load. Particularly, an MIH message IDentifier (ID) within the MIHF fixed header consists of Session ID (SID)  120 , Opcode  130  and Action ID  140 . When the MIH frame is utilized for getting information or providing information, the SID  120  is set to ‘Information_Service’, and the Action ID  140  is set to ‘MIH_Get_Information’. When the MIH frame is utilized for requesting information, the Opcode  130  is set to ‘Request’, and when the MIH frame is utilized for providing information, the Opcode  130  is set to ‘Response’. 
       FIG. 2  is a block diagram of an IS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 2 , the IS includes a communication module  210 , a capture module  220 , a parsing module  230 , an event module  240 , a generator module  250 , and database (DB) module  260 . 
     The communication module  210  performs a function for converting between bit streams and physical signals, and routing transmit and receive MIH packets for MTs and ANs. 
     The capture module  220  captures an MIH packet from packets received through the communication module  210  and provides the parsing module  230  with the MIH packet. More specifically, the capture module  220  receives the MIH packet. For instance, the capture module  220  may receive the MIH packet by using raw socket. After receiving a packet from kernel, the capture module  220  examines a protocol field in an IP header of the packet to determine whether the protocol field is set to ‘IPPROTO_MIH’ or not. If the protocol field is set to ‘IPPROTO_MIH’ (i.e., the packet is an MIH packet), the capture module  220  examines an Action ID field in an MIH header of the MIH packet to determine whether the Action ID field is set to ‘MIH_Get_Information’ or not. If the Action ID field is set to ‘MIH_Get_Information’, the capture module  220  extracts a source address field from the IP header and an MIH frame. Herein, the MIH frame is included in data range of the MIH packet. After that, the capture module  220  sends a message including the source address and the MIH frame to the parsing module  230 . 
     The parsing module  230  classifies the MIH frame from the capture module  220  as an information request frame or an information response frame, and sends the information request frame or the information response frame to the generator module  250  of the DB module  260 . More specifically, the parsing module  230  receives the MIH frame from the capture module  220 , and determines whether the MIH frame is the information request frame or the information response frame by examining the Opcode field in the MIH header. When the MIH frame is the information request frame, the parsing module  230  examines whether there exists a Querier Location TLV in the MIH frame. If the Querier Location TLV exists, the parsing module  230  classifies the requested information type. For instance, requested information types are shown in Table 2 below. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 No 
                 Type 
                 Identifier 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 TYPE_IE_NETWORK_TYPE 
                 0x10000000 
               
               
                 2 
                 TYPE_IE_OPERATOR_IDENTIFIER 
                 0x10000001 
               
               
                 3 
                 TYPE_IE_SERVICE_PROVIDER_IDENTIFIER 
                 0x10000002 
               
               
                 4 
                 TYPE_IE_ACCESS_NETWORK_IDENTIFIER 
                 0x10000100 
               
               
                 5 
                 TYPE_IE_ROAMING_PARTNERS 
                 0x10000101 
               
               
                 6 
                 TYPE_IE_COST 
                 0x10000102 
               
               
                 7 
                 TYPE_IE_NETWORK_STANDARDS 
                 0x10000103 
               
               
                 8 
                 TYPE_IE_NETWORK_SECURITY 
                 0x10000104 
               
               
                 9 
                 TYPE_IE_NETWORK_QOS 
                 0x10000105 
               
               
                 10 
                 TYPE_IE_POA_ADDRESS 
                 0x10000200 
               
               
                 11 
                 TYPE_IE_POA_LOCATION 
                 0x10000201 
               
               
                 12 
                 TYPE_IE_POA_DATA_RATE 
                 0x10000202 
               
               
                 13 
                 TYPE_IE_POA_CHANNEL_RANGE 
                 0x10000203 
               
               
                 14 
                 TYPE_IE_SUBNET_INFORMATION 
                 0x10000204 
               
               
                 15 
                 TYPE_IE_POA_CONFIG_METHOD 
                 0x10000205 
               
               
                 16 
                 TYPE_IE_POA_CAPABILITIES 
                 0x10000206 
               
               
                 17 
                 TYPE_IE_POA_IP_ADDRESS 
                 0x10000207 
               
               
                 18 
                 TYPE_IE_POA_DHCP_SERVER_ADDRESS 
                 0x10000208 
               
               
                 19 
                 TYPE_IE_POA_FA_AR_ADDRESS 
                 0x10000209 
               
               
                 20 
                 TYPE_CONTAINER_LIST_OF_NETWORKS 
                 0x10000300 
               
               
                   
                 Contained information: 
               
               
                   
                 Access Network Container #1 
               
               
                   
                 Access Network Container #2 (optional) 
               
               
                   
                 . . . 
               
               
                   
                 Access Network Container #k (optional) 
               
               
                   
                 Vender Specific IE (optional) 
               
               
                 21 
                 TYPE_CONTAINER_NETWORK 
                 0x10000301 
               
               
                   
                 Contained information: 
               
               
                   
                 Network TYPE IE 
               
               
                   
                 Operator Identifier IE 
               
               
                   
                 Roaming Partners IE (optional) 
               
               
                   
                 Cost IE (optional) 
               
               
                   
                 Network Security IE (optional) 
               
               
                   
                 QoS IE (optional) 
               
               
                   
                 PoA Container #1 
               
               
                   
                 PoA Container #2 (optional) 
               
               
                   
                 . . . 
               
               
                   
                 PoA Container #k (optional) 
               
               
                   
                 Vender Specific Network IE (optional) 
               
               
                 22 
                 TYPE_REPORT_POA == 
                 0x10000302 
               
               
                   
                 TYPE_CONTAINER_POA 
               
               
                   
                 Contained information: 
               
               
                   
                 PoA Location IE 
               
               
                   
                 PoA Data Rate IE 
               
               
                   
                 PoA Channel Range IE 
               
               
                   
                 PoA Subnet Information IE 
               
               
                   
                 PoA IP Configuration Methods IE 
               
               
                   
                 PoA Capabilities IE 
               
               
                   
                 PoA PHY TYPE IE (No. 18) 
               
               
                   
                 PoA Address IE (No. 14) 
               
               
                   
                 Vender Specific PoA IE (optional) 
               
               
                   
               
             
          
         
       
     
     When the MIH frame is the information response frame, the MIH frame is transmitted by an AN. It is the network information within the MIH frame that is requested to each AN periodically by the event module  240 . Accordingly, the network information is classified, and classified network information is sent to the DB module  260 . 
     The event module  240  determines whether updating the network information is needed or not, and instructs the generator module  250  to generate an Information_Get_Request packet when the updating is needed. For instance, in case that the network information is updated periodically upon a predefined system setting, the event module  240  informs the generator module  250  of each passing period. More specifically, the event module  240  transmits the information request frame to each AN. The event module  240  maintains a list which has network information on each AN. Herein, the network information on the list is able to be controlled by using Command Line Interface (CLI). 
     The generator module  250  generates an Information_Get_Response packet for providing the network information to the MT and an Information_Get_Resquest packet for requesting network information to the ANs. More specifically, when a message including addresses of the ANs is sent from the event module  240 , the generator module  250  generates an information request frame, and sets up the MIH header and the IP header. In this case, the Action ID field is set to ‘MIH_Get_Information’, the SID field is set to ‘Information_Service’, and the Opcode field is set to ‘Request’ in the MIH header. When a message having a result of classifying requested information is sent from the parsing module  230 , the generator module  250  gets the requested information from the DB module  260 , and generates an information response frame. In this case, the Action ID field is set to ‘MIH_Get_Information’, the SID field is set to ‘Information_Service’, and the Opcode field is set to ‘Response’ in the MIH header. 
     The DB module  260  stores the network information received from ANs. The network information stored by the DB module  260  includes the items shown in Table 1. More specifically, when a message including classified information is sent from the parsing module  230 , the database module  260  executes an insert operation to store the classified information to database. On the other hand, when a message including a result of classifying requested information is sent from the generator module  250 , the database module  260  executes a query operation to get the requested information from database, and returns the requested information to the generator module  250 . 
       FIGS. 3A to 3E  are flowcharts illustrating operating processes of each module within the IS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 3A , the capture module  220  checks whether a packet is received or not in step  301 . When the packet is received, the capture module  220  determines whether the packet is an MIH packet in step  303 . In other words, the capture module  220  examines a protocol field in an IP header of the packet to determine whether the protocol field is set to ‘IPPROTO_MIH’ or not. If the protocol field is not set to ‘IPPROTO_MIH’ (i.e., the packet is not an MIH packet), the capture module  220  drops the packet in step  305 , and returns the step  301 . If the protocol field is set to ‘IPPROTO_MIH’ (i.e., the packet is an MIH packet), the capture module  220  examines an Action ID field in an MIH header of the MIH packet to determine whether the Action ID field is set to ‘MIH_Get_Information’ or not in step  307 . If the Action ID field is not set to ‘MIH_Get_Information’, the capture module  220  drops the packet in step  305 , and returns the step  301 . If the Action ID field is set to ‘MIH_Get_Information’, the capture module  220  extracts a source address field of the IP header, and an MIH frame in step  309 . After that, the capture module  220  sends a message including the source address and the MIH frame to the parsing module  230  in step  311 . 
     Referring to  FIG. 3B , the parsing module  230  checks whether a message including an MIH frame and a source address is provided from the capture module  220  in step  321 . When the massage is provided, the parsing module  230  determines whether the MIH frame is an information request frame or an information response frame by examining the Opcode field in the MIH header in step  323 . If the MIH frame is an information request frame, the parsing module  230  examines whether there exists a Querier Location TLV in the MIH frame in step  325 . If the Querier Location TLV does not exist, the parsing module  230  drops the message in step  327 , and returns to step  321 . If the Querier Location TLV exists, the parsing module  230  classifies the requested information type in step  329 , and sends the result of classifying the requested information and the source address to the generator module in step  331 . When the MIH frame is the information response frame, the parsing module  230  classifies the response information in step  333 , and sends the classified response information to the DB module  260  in step  335 . 
     Referring to  FIG. 3C , the event module  240  checks whether an availability timer about network information within a list has expired or not in step  341 . When the availability timer has expired, the event module  240  confirms addresses of ANs in the list in step  343 , and restarts the availability time in step  345 . After that, the event module  240  sends a message including the addresses of the ANs to the generator module  250  in step  347 . 
     Referring to  FIG. 3D , the generator module  250  checks whether a message is provided from the parsing module  230  or a message is provided from event module  240  in step  361 . When the message including a result of classifying requested information is provided from the parsing module  230 , the generator module  250  gets the requested information from the DB module  260  in step  363 , and generates an information response frame in step  365 . Then, the generator module  250  sets up an IP header and an MIH header in step  367 , and transmits a packet consisting of the IP header and the information response frame. When the message including addresses of the ANs is provided from the event module  240 , the generator module  250  generates an information request frame in step  371 , and sets up the MIH header and the IP header in step  373 . Then, the generator module  250  transmits a packet consisting of the IP header and the information request frame in step  375 . 
     Referring to  FIG. 3E , the DB module  260  checks whether a message is provided from the parsing module  230  or the generator module  250  in step  381 . When the message including classified information and a source address is provided from the parsing module  230 , the DB module  260  executes an insert operation in step  383 . In other words, the DB module  260  updates network information corresponding to the source address. On the other hand, when the message including a result of classifying requested information is provided from the generator module  250 , the DB module  260  executes a query operation in step  385 . In other words, the DB module  260  gets the requested information from the database. After that, the DB module  260  sends the requested information to the generator module  250  in step  387 . 
       FIG. 4  is a flowchart illustrating operating processes of the IS in a wireless communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , the IS determines whether updating network information on the ANs is needed or not in step  401 . The network information includes the items shown in Table 1, and is stored a database within the IS. For instance, in the case that the network information is updated periodically upon a predefined system setting, the IS determines to update the network information upon the passing of every time period. 
     When updating is needed, the IS generates an MIH Information_Get_Request packet for requesting the network information from the ANs in step  403 . That is, the IS confirms addresses of the ANs in a list including the network information, and generates the MIH Information_Get_Request packets including the addresses of the ANs. 
     After generating the MIH Information_Get_Request packets, the IS transmits the MIH Information_Get_Request packets to the ANs in step  405 . 
     Then, the IS checks whether an MIH packet is received or not in step  407 . That is, the IS checks whether the MIH packet is captured from received packets. In other words, the IS checks whether there exists a packet including a protocol field set to ‘IPPROTO_MIH’ among the received packets. 
     When the MIH packet is received, the IS determines whether the MIH frame included the MIH packet is an information response frame or an information request frame in step  409 . That is, the IS checks whether an Opcode field of the MIH frame is ‘Request’ or ‘Response’ . Herein, the information response frame is received from an AN, and the information request frame is received from an MT. Moreover, the information response frame is received as a response to the MIH Information_Get_Request packet transmitted in step  405 , or is received without a request when network information for the AN is changed. 
     If the MIH frame is an information response frame, the IS stores the network information within the information response frame in step  411 . That is, the IS classifies response information within the information response frame, and stores the response information to the database according to the result of classifying. 
     If the MIH frame is an information request frame, the IS gets information requested by the information request frame, and generates an MIH Information_Get_Response packet in step  413 . In other words, the IS gets requested information from the database, and generates an information response frame. Then, the IS sets up an IP header and an MIH header. In this case, the IS sets an Action ID field to ‘MIH_Get_Information’, the SID field to ‘Information_Service’ and the Opcode field to ‘Response’ in the MIH header, and an protocol field to ‘IPPROTO_MIH’ in the IP header. 
     After generating the MIH Information_Get_Response packet, the IS transmits the MIH Information_Get_Response packet in step  415 . 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.