Abstract:
A method and system for transmitting/receiving data in a heterogeneous communication system. A terminal accesses a first controller of a first communication system supporting a first communication service to make a communication path to the first communication system. After making the communication path to the terminal, the first controller determines whether it is possible to provide the first communication service to the terminal over the first communication system. If it is not possible, the first controller transmits to an interworking unit a first request indicating that the terminal requires the first communication service over the second communication system. The interworking unit transmits a second request to a second controller of the second communication system in response to the first request, the second request indicating that the second controller provides the first communication service to the terminal. Upon receiving a response to the second request, the interworking unit controls the first controller to provide the first communication service to the terminal over the second communication system according to the response.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a communication system, and in particular, to a method and system for transmitting and receiving data in a heterogeneous communication system. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the next generation communication system, intensive research is being conducted to provide users with services having a high data rate and various high-capacity Qualities-of-Service (QoSs). Particularly, in the current next generation communication system, Orthogonal Frequency Division Multiplexing (OFDM) scheme or Orthogonal Frequency Division Multiple Access (OFDMA) scheme is used for a Broadband Wireless Access (BWA) communication system, such as Wireless Local Area Network (WLAN) system and Wireless Metropolitan Area Network (WMAN) system, both of which are Institute of Electrical and Electronics Engineers (IEEE) 802.11 communication systems. Therefore, intensive research is being carried out on a technology for supporting high-speed services in the form of guaranteeing mobility and QoS, and an example of its typical communication system includes an IEEE 802.16 communication system. 
         [0003]    With reference to  FIG. 1 , a description will now be made of a general IEEE 802.11 communication system. 
         [0004]      FIG. 1  is a diagram illustrating a configuration of a general IEEE 802.11 communication system. 
         [0005]    Referring to  FIG. 1 , the IEEE 802.11 communication system includes a terminal  101 , access points (APs) of AP 1   111  and AP 2   113 , an access point controller (APC)  121 , a router  123 , an Internet Protocol (IP) network  131 , an Authentication, Authorization, Accounting (AAA) server  141 , and a public IP network  151 . 
         [0006]    The AP 1   111  and the AP 2   113  are network equipments for processing a wireless access protocol with the terminal  101  that accesses the IEEE 802.11 communication system. The APC  121 , network equipment for serving to control the AP 1   111  and the AP 2   113 , provides an IEEE 802.11 communication service to the terminal  101  over the AP 1   111  and the AP 2   113  using the line. 
         [0007]    The router  123  serves to perform a routing function for relaying between the APC  121  and the IP network  131 , and the IP network  131  is a network for providing the IEEE 802.11 communication service to the terminal  101  that accesses the IEEE 802.11 communication system. The AAA server  141  performs authentication, authorization and accounting functions on the terminal  101  that accesses the communication system. 
         [0008]    A description of the configuration of the general IEEE 802.11 communication system has been made so far with reference to  FIG. 1 . Next, with reference to  FIG. 2 , a description will be given of a configuration of a general IEEE 802.16 communication system. 
         [0009]      FIG. 2  is a diagram illustrating a configuration of a general IEEE 802.16 communication system. 
         [0010]    Referring to  FIG. 2 , the IEEE 802.16 communication system includes a terminal  210 , Radio Access Stations (RASs) of RAS 1   221  and RAS 2   223  which constitute an Access Network (AN)  220 , an Access Control Router (ACR)  225 , an IP network  230 , an AAA server  240 , and a public IP network  250 . 
         [0011]    The RAS 1   221  and the RAS 2   223  are network equipments for processing a wireless access protocol with the terminal  210  that accesses the IEEE 802.16 communication system. The ACR  225  is network equipment for performing such functions as authentication, Medium Access Control (MAC) protocol processing, IP address allocation, and routing on the terminal  210  that accesses the communication system. The IP network  230  is a server for performing authentication, authorization and accounting functions on the terminal  210  that accesses the communication system. 
         [0012]    A brief description of the configuration of the general IEEE 802.16 communication system has been made so far with reference to  FIG. 2 . Next, with reference to  FIG. 3 , a description will be made of a network configuration for service interworking between the IEEE 802.11 communication system and the IEEE 802.16 communication system. 
         [0013]      FIG. 3  is a diagram illustrating a network configuration for service interworking between a general IEEE 802.11 communication system and a general IEEE 802.16 communication system. 
         [0014]    Referring to  FIG. 3 , the network configuration for service interworking between the communication systems includes RASs of RAS 1   310  and RAS 2   312  for processing a wireless access protocol with a terminal  300  accessing the IEEE 802.16 communication system; an ACR  320  for performing such functions as authentication, MAC protocol processing, IP address allocation, and routing on the terminal  300 ; APs of AP 1   330  and AP 2   332  for processing a wireless access protocol with the terminal  300  accessing the IEEE 802.11 communication system; an APC  340  for serving to control the AP 1   330  and the AP 2   332 ; an IP network  350  for providing the IEEE 802.16 communication service and the IEEE 802.11 communication service to the terminal  300 ; an AAA server  360  for performing authentication, authorization and accounting functions on the terminal  300  accessing the IEEE 802.16 communication system and the IEEE 802.11 communication system; a Home Agent (HA)  370  for performing a routing function for relaying between the IEEE 802.16 communication system and the IEEE 802.11 communication system; and a public IP network  380 . 
         [0015]    As described above, the network configuration should be prepared to provide both the IEEE 802.16 communication service and the IEEE 802.11 communication service to the terminal  300 . To provide the foregoing services, there is a need for a scheme capable of seamlessly providing the services over the optimal wireless access network determined according to the position and service requirements of the terminal. In addition, when the terminal intends to perform handover between different communication systems, the scheme should assign Mobile IP to support handover. However, in order to perform handover as described above, the terminal should be assigned an address of Mobile IP from the public IP network  380 . This is because the terminal may suffer from a time delay such as signaling delay and traffic delay during interworking between heterogeneous communication systems. 
       SUMMARY OF THE INVENTION 
       [0016]    To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to address at least the problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a method and system for transmitting and receiving data in a heterogeneous communication system. 
         [0017]    Another aspect of the present invention is to provide a data transmission/reception method and system for providing seamless services in a heterogeneous communication system. 
         [0018]    Further another aspect of the present invention is to provide a data transmission/reception method and system in which a terminal can perform fast handover in a heterogeneous communication system. 
         [0019]    Yet another aspect of the present invention is to provide a data transmission/reception method and system for allowing a base station to support heterogeneous systems rather than allowing the terminal to support heterogeneous systems in a heterogeneous communication system. 
         [0020]    Still another aspect of the present invention is to provide a method and system for allowing a terminal to transmit/receive data using its own network, or even though it belongs to another network, to transmit/receive data adaptively using its own network or another network according to the communication environment in a heterogeneous communication system. 
         [0021]    According to one aspect of the present invention, there is provided a method for transmitting and receiving data in a heterogeneous communication system. The method includes accessing, by a terminal, a first controller of a first communication system providing a first communication service, to make a communication path to the first communication system; after making the communication path to the terminal, determining by the first controller whether it is possible to provide the first communication service to the terminal over the first communication system; when it is not possible to provide the first communication service to the terminal over the first communication system, transmitting by the first controller to an interworking unit a first request indicating that the terminal requires to receive the first communication service over the second communication system; transmitting, by the interworking unit, a second request to a second controller of the second communication system in response to the first request, the second request indicating that the second controller requires to provide the first communication service to the terminal; and upon receiving a response to the second request from the second controller, controlling by the interworking unit the first controller to provide the first communication service to the terminal over the second communication system according to the response. 
         [0022]    According to another aspect of the present invention, there is provided a system for transmitting and receiving data in a heterogeneous communication system. The system includes a terminal; a first controller of a first communication system providing a first communication service; a second controller of a second communication system; and an interworking unit. The terminal accesses the first controller to make a communication path to the first communication system. After making the communication path to the terminal, the first controller determines whether it is possible to provide the first communication service to the terminal over the first communication system, and when it is not possible to provide the first communication service to the terminal over the first communication system, the first controller transmits to the interworking unit a first request indicating that the terminal requires to receive the first communication service over the second communication system. The interworking unit transmits a second request to the second controller in response to the first request, the second request indicating that the second controller requires to provide the first communication service to the terminal, and upon receiving a response to the second request from the second controller, the interworking unit controls the first controller to provide the first communication service to the terminal over the second communication system according to the response. 
         [0023]    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; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. 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 
         [0024]    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: 
           [0025]      FIG. 1  is a diagram illustrating a configuration of a general IEEE 802.11 communication system; 
           [0026]      FIG. 2  is a diagram illustrating a configuration of a general IEEE 802.16 communication system; 
           [0027]      FIG. 3  is a diagram illustrating a network configuration for service interworking between a general IEEE 802.11 communication system and a general IEEE 802.16 communication system; 
           [0028]      FIG. 4A  is a diagram illustrating a network configuration for data transmission/reception in a heterogeneous communication system according to an embodiment of the present invention; 
           [0029]      FIG. 4B  is a diagram illustrating an interworking unit apparatus in a heterogeneous communication system according to an embodiment of the present invention; 
           [0030]      FIG. 5  is a diagram illustrating a process in which a terminal accesses an IEEE 802.16 communication system according to an embodiment of the present invention; 
           [0031]      FIG. 6  is a diagram illustrating a process in which a terminal accesses an IEEE 802.11 communication system in a communication system according to an embodiment of the present invention; 
           [0032]      FIG. 7  is a diagram illustrating a process of providing a service through an interworking unit in a communication system according to an embodiment of the present invention; and 
           [0033]      FIG. 8  is a diagram illustrating a process of providing a service through an interworking unit in a communication system according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]      FIGS. 1 through 8 , 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 communication system. 
         [0035]    The present invention provides a method and system for transmitting and receiving data in a heterogeneous communication system. Although a description of the present invention will be given with reference to an Institute of Electrical and Electronic Engineers (IEEE) 802.16 communication system and an IEEE 802.11 communication system as heterogeneous systems, by way of example, the data transmission/reception method and system proposed by the present invention can also be applied to other heterogeneous communication systems. 
         [0036]    In addition, the present invention provides a data transmission/reception method and system capable of seamlessly providing a communication service when an arbitrary terminal moves to another communication system while receiving a service from one communication system, in a heterogeneous system including a first communication system, e.g., 802.16 communication system, and a second communication system, e.g., 802.11 communication system. 
         [0037]    Further, the present invention provides a data transmission/reception method and system for providing a service of a first communication system to an arbitrary terminal over a second communication system, when a load occurs in the first communication system from which the terminal intends to receive the service. 
         [0038]    With reference to  FIG. 4A , a description will now be made of a network configuration for service interworking between an IEEE 802.11 communication system and an IEEE 802.16 communication system in a heterogeneous communication system according to an embodiment of the present invention. 
         [0039]      FIG. 4A  is a diagram illustrating a network configuration for data transmission/reception in a heterogeneous communication system according to an embodiment of the present invention. Shown in  FIG. 4A  is a network configuration for service interworking between an IEEE 802.11 communication system and an IEEE 802.16 communication system. 
         [0040]    Referring to  FIG. 4A , the network configuration for service interworking includes an IEEE 802.16 communication system and an IEEE 802.11 communication system. A description of an embodiment of the present invention will be given for an exemplary case where a terminal moves to a second communication system, e.g., IEEE 802.11 communication system, while receiving a service from a first communication system, e.g., IEEE 802.16 communication system, to which it is now connected. In this exemplary case, the terminal can access both the IEEE 802.16 communication system and the IEEE 802.11 communication system. 
         [0041]    The network configuration includes Radio Access Stations (RASs) of RAS 1   410  and RAS 2   412  for processing a wireless access protocol with a terminal  400  accessing the IEEE 802.16 communication system and for serving as base stations, an Access Control Router (ACR)  420  for performing such functions as authentication, Medium Access Control (MAC) protocol processing, Internet Protocol (IP) address allocation, and routing on the terminal  400 , an Authentication Authorization Accounting (AAA) server  430  for performing authentication, authorization and accounting functions on the terminal  400  accessing the IEEE 802.16 communication system, and an IP network  470  for providing the IEEE 802.16 communication service to the terminal  400 . 
         [0042]    Further, the network configuration includes APs of AP 1   440  and AP 2   442  for processing a wireless access protocol with the terminal  400  accessing the IEEE 802.11 communication system and for serving as base stations, an APC  450  for serving to control the APs  440  and  442 , an AAA server  460  for performing authentication, authorization and accounting functions on the terminal  400  accessing the IEEE 802.11 communication system, and an IP network  480  for providing the IEEE 802.11 communication service to the terminal  400 . In addition, the network configuration includes a public IP network  490  for providing the IEEE 802.16 service and the IEEE 802.11 service, and an interworking unit  495  for interworking between the IEEE 802.16 communication system and the IEEE 802.11 communication system. The interworking unit  495  can be included in the ACR and/or APC. Alternatively, as shown in  FIG. 4A , the interworking unit  495  can be provided separately from the ACR and the APC. A detailed description of the interworking unit  495  will be given below. 
         [0043]    In such heterogeneous communication systems, i.e., IEEE 802.16 communication system and IEEE 802.11 communication system, the network elements for data transmission/reception are equal to those described in  FIGS. 1 and 2 . Therefore, the following description will be focused on the interworking unit  495  newly proposed by the present invention. For convenience, the following description will be given for the exemplary case where the terminal  400  first receives a first communication service over the RAS 1   410 . 
         [0044]    When the terminal  400  accesses the first communication system to receive a first communication service, it receives the first communication service over the RAS 1   410  and the ACR  420 . 
         [0045]    If a load occurs in the first communication system while the terminal  400  is receiving the first communication service, the terminal  400  accesses the second communication system in order to receive the first communication service over the second communication system. In this case, the terminal  400  receives the service over the RAS 1   410  that provides the first communication service over the AP 1   440  and the APC  450  (or the AP 2   442  and the APC  450 ) and the interworking unit  495 . 
         [0046]    If the terminal  400  performs handover with an intention to receive the second communication service while receiving the first communication service, the terminal  400  performs handover to the second communication system using the intact IP address allocated from the first communication system. 
         [0047]    In this case, the RAS and the AP each have a physical layer structure and a MAC layer structure supporting heterogeneous devices. 
         [0048]    Next, the following description will be made for the exemplary case where the terminal  400  receives the second communication service over the AP 1   440 . 
         [0049]    When the terminal  400  accesses the second communication system to receive the second communication service, the terminal  400  receives the second communication service over the AP 1   440  and the APC  450 . 
         [0050]    If a load occurs in the second communication system while the terminal  400  is receiving the second communication service, the terminal  400  receives the second communication service over the first communication system. That is, the terminal  400  accesses the first communication system, and receives the service over the APC  450  that provides the second communication service over the RAS 1   410  and the ACR  420  (or the RAS 2   412  and the ACR  420 ) and the interworking unit  495 . 
         [0051]    The RAS 1   410 , RAS 2   412 , AP 1   440  and AP 2   442  each include elements capable of supporting both the first communication system and the second communication system. Therefore, in the case where the terminal  400  accesses the first communication system to receive the first communication service, even though Mobile IP allocation is impossible due to the load occurred in the ACR  420 , RAS 1   410  and RAS 2   412  which are providing the first communication service, the terminal  400  can receive the first communication service over the second communication system. Specifically, the terminal  400  can receive the first communication service over the APC  450  by way of the RAS 1   410  (or the RAS 2   412 ) and the interworking unit  495 . 
         [0052]    Also, in the case where the terminal  400  accesses the second communication system to receive the second communication service, even though Mobile IP allocation is impossible due to the load occurred in the APC  450 , AP 1   440  and AP 2   442  which are providing the second communication service, the terminal  400  can receive the second communication service over the first communication system. Specifically, the terminal  400  can receive the second communication service over the ACR  420  by way of the AP 1   440  (or the AP 2   442 ) and the interworking unit  495 . 
         [0053]    With reference to  FIG. 4B , a description will now be made of a function of the interworking unit  495  for data transmission/reception in the heterogeneous communication system according to an embodiment of the present invention. 
         [0054]      FIG. 4B  is a diagram illustrating an interworking unit apparatus in a heterogeneous communication system according to an embodiment of the present invention. 
         [0055]    Referring to  FIG. 4B , since the interworking unit  495  can support both the IEEE 802.16 communication system and the IEEE 802.11 communication system as described above, it should have wireless access protocols of both the IEEE 802.16 communication system and the IEEE 802.11 communication system. In addition, the interworking unit  495  has a function of detecting signals of an arbitrary terminal that desires to access the system, for example, the IEEE 802.16 communication system, from which it intends to receive the service, or a function of detecting signals of a terminal intending to access the IEEE 802.11 communication system. Therefore, upon detecting signals of the system from which the arbitrary terminal desires to receive the service, the interworking unit  495  provides the service according to the signals desired by the terminal. 
         [0056]    The interworking unit  495  is divided into layers available by the 802.11 communication system and layers available by the 802.16 communication system. For example, when a signal of the terminal intending to receive the 802.11 communication service is received, a bridge included in the interworking unit bridges it to the layers supporting the 802.11 communication system, and when a signal of the terminal intending to receive the 802.16 communication service is received, the bridge included in the interworking unit bridges it to the layers supporting the 802.16 communication system. 
         [0057]    A description of the network elements for data transmission/reception in the heterogeneous communication system according to an embodiment of the present invention has been made so far with reference to  FIGS. 4A and 4B . Next, with reference to  FIG. 5 , a description will be made of a process in which a terminal accesses the IEEE 802.16 communication system according to an embodiment of the present invention. 
         [0058]      FIG. 5  is a diagram illustrating a process in which a terminal accesses an IEEE 802.16 communication system according to an embodiment of the present invention. 
         [0059]    A terminal  501  searches for a RAS of the IEEE 802.16 communication system where it is now located (Step  510 ). If a specific RAS of the IEEE 802.16 communication system is searched, the terminal  501  matches its synchronization with the searched RAS  503  (Step  512 ). The RAS  503 , which is synchronized with the terminal  501 , acquires a path (route) to an ACR  505  (Step  514 ). Thereafter, the terminal  501  generates a Registration Request (REG-REQ) message and delivers it to the ACR  505  over the RAS  503  (Step  516 ). Upon receiving the REG-REQ message, the ACR  505  transmits a request for a user profile to an AAA server  507  to acquire the user profile. Then the ACR  505  generates a Registration Response (REG-RSP) message and delivers the REG-RSP message to the RAS  503  (Step  518 ). 
         [0060]    After delivering the REG-RSP message, the ACR  505  performs an IP address allocation procedure (Step  520 ). The terminal  501  is allocated an IP address by means of the ACR  505 , and performs environment setup according to the allocated IP address (Step  522 ). Next, the terminal  501  performs an access authentication process with the AAA server  507  (Step  524 ). Through this procedure, the terminal  501  is connected to the IEEE 802.16 communication system, and a subscriber receives the IEEE 802.16 communication service over the connected terminal  501 . 
         [0061]    A description of the process in which the terminal accesses the IEEE 802.16 communication system in the communication system according to an embodiment of the present invention has been made with reference to  FIG. 5 . Next, with reference to  FIG. 6 , a description will be made of a process in which a terminal accesses the IEEE 802.11 communication system in a communication system according to an embodiment of the present invention. 
         [0062]      FIG. 6  is a diagram illustrating a process in which a terminal accesses an IEEE 802.11 communication system in a communication system according to an embodiment of the present invention. 
         [0063]    A terminal  601  searches for an AP of the IEEE 802.11 communication system where it is now located. When a specific AP of the IEEE 802.11 communication system is searched, the terminal  601  performs synchronization with the searched AP  603 , and performs an authentication and association procedure on the terminal  601  according to a wireless access protocol defined by the IEEE 802.11 communication system (Step  610 ). Next, the terminal  601  performs an Extensible Authentication Protocol (EAP) process with an APC  605  (Step  612 ). The APC  605 , after performing the EAP process, transmits an Access Request message to an AAA server  607  (Step  614 ). The AAA server  607  determines whether the access can be made according to the Access Request message, and then transmits to the APC  605  an Access Response message including the accessibility (Step  616 ). 
         [0064]    Next, the terminal  601  transmits a Connection Request message to the AP  603  (Step  618 ). Upon receiving the Connection Request message, the AP  603  transmits an REG-REQ message to the APC  605  (Step  620 ). The APC  605  generates an REG-RSP message corresponding to the REG-REQ message, and transmits the generated REG-RSP message to the AP  603  (Step  622 ). Upon receiving the REG-RSP message, the AP  603  generates a Connection Response message and transmits it to the terminal  601  (Step  624 ). The terminal  601  is allocated an IP address from the APC  605 , and performs environment setup according to the allocated IP address (Step  626 ). Through this procedure, the terminal  601  is connected to the IEEE 802.11 communication system, and a subscriber receives the IEEE 802.11 communication service over the connected terminal  601 . 
         [0065]    A description of the process in which the terminal accesses the IEEE 802.11 communication system in the communication system according to an embodiment of the present invention has been given with reference to  FIG. 6 . Next, with reference to  FIG. 7 , a description will be made of a process in which a terminal accesses an IEEE 802.16 communication system and receives a service from an IEEE 802.11 communication system through an interworking unit in the communication system according to an embodiment of the present invention. 
         [0066]      FIG. 7  is a diagram illustrating a process of providing a service through an interworking unit in a communication system according to an embodiment of the present invention. 
         [0067]    A terminal  701  searches for a RAS of the IEEE 802.16 communication system where it is now located (Step  710 ). When a specific RAS of the IEEE 802.16 communication system is searched, the terminal  701  matches its synchronization with the searched RAS  703  (Step  712 ). The RAS  703 , which is synchronized with the terminal  701 , acquires a path to an ACR  705  (Step  714 ). Thereafter, the terminal  701  generates an REG-REQ message and transmits it to the ACR  705  over the RAS  703  (Step  716 ). In this case, if load traffic has occurred in the RAS  703  or allocation of an IP address is impossible, the ACR  705 , which has received the REG-REQ message, forwards the REG-REQ message to an interworking unit  707  (Step  718 ). Then the interworking unit  707  forwards the REG-REQ message to an AP/APC  709  (Step  720 ). Upon receiving the REG-REQ message, the AP/APC  709  determines its acceptability of the terminal  701 , and transmits a request for a user profile to an AAA server  711  to acquire the user profile. Then the AP/APC  709  generates an REG-RSP message and transmits it to the interworking unit  707  (Step  722 ), and the interworking unit  707  forwards the REG-RSP message to the ACR  705  (Step  724 ). 
         [0068]    Upon receiving the REG-RSP message, the ACR  705  performs an IP address allocation procedure (Step  726 ). The terminal  701  is allocated an IP address by means of the ACR  705 , and performs environment setup according to the allocated IP address (Step  728 ). Next, the terminal  701  performs an access authentication process with the AAA server  711  (Step  730 ). Through this procedure, the terminal  701  is connected to the IEEE 802.16 communication system by way of the AP/APC  709  that manages the IEEE 802.11 communication system, and a subscriber receives the IEEE 802.16 communication service over the connected terminal  701 . 
         [0069]    A description of the process in which the terminal accesses the IEEE 802.16 communication system and receives the IEEE 802.16 service from the IEEE 802.11 communication system through the interworking unit in the communication system according to an embodiment of the present invention has been made with reference to  FIG. 7 . Next, with reference to  FIG. 8 , a description will be made of a process in which a terminal accesses an IEEE 802.11 communication system and receives an IEEE 802.11 service from an IEEE 802.16 communication system through an interworking unit in a communication system according to an embodiment of the present invention. 
         [0070]      FIG. 8  is a diagram illustrating a process of providing a service through an interworking unit in a communication system according to an embodiment of the present invention. 
         [0071]    A terminal  801  searches for an AP of the IEEE 802.11 communication system where it is now located. When a specific AP of the IEEE 802.11 communication system is searched, the terminal  801  performs synchronization with the searched AP  803 , and performs an authentication and association procedure on the terminal  801  according to a wireless access protocol defined by the IEEE 802.11 communication system (Step  810 ). Next, the terminal  801  performs an EAP authentication process with an APC  805  (Step  812 ). In this case, if load traffic has occurred in the AP  803 , or allocation of an IP address is impossible, the APC  805  transmits an Access Request message to an interworking unit  807  (Step  814 ). The interworking unit  807 , which has received the Access Request message, forwards the Access Request message to an ACR/RAS  809  (Step  816 ). Then the ACR/RAS  809  forwards the Access Request message to an AAA server  811  (Step  818 ). The AAA server  811  determines whether the access can be made according to the Access Request message, and then transmits to the ACR/RAS  809  an Access Response message including the accessibility (Step  820 ). The ACR/RAS  809  forwards the Access Response message to the interworking unit  807  and the APC  805  (Steps  822  and  824 ). 
         [0072]    Next, the terminal  801  transmits a Connection Request message to the AP  803  (Step  826 ). Upon receiving the Connection Request message, the AP  803  forwards the Connection Request message to the APC  805  (Step  828 ). Upon receiving an REG-RSP message from the interworking unit  807  (Step  830 ), the APC  805  allocates an IP address to the terminal  801  and performs environment setup according to the IP address (Step  832 ). Next, the terminal  801  performs an access authentication process with the AAA server  811  (Step  834 ). Through this process, the terminal  801  is connected to the IEEE 802.11 communication system by way of the ACR/RAS  809  that manages the IEEE 802.16 communication system, and a subscriber receives the IEEE 802.11 communication service over the connected terminal  801 . 
         [0073]    Although not illustrated in the drawings, even when the terminal performs handover from the 802.11 communication system to the 802.16 communication system, the present invention can perform handover rapidly without service drop, enabling stable data transmission/reception. 
         [0074]    As is apparent from the foregoing description, according to the present invention, the base station in the heterogeneous communication system is equipped with the interworking unit supporting the heterogeneous mode, thereby facilitating data transmission/reception without service drop. In addition, the terminal can enable data transmission/reception without service drop even during handover. 
         [0075]    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.