Abstract:
An apparatus and method for managing a Connection IDentifier (CID) in a communication system are provided. The method includes mapping a different index to at least one CID allocated by a base station (BS) and, if simultaneously transmitting packets for at least two CIDs, indexing a CID for packet transport by an index mapped to each CID and simultaneously transmitting packets for at least two CIDs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application claims priority under 35 U.S.C. §119(a) to a Korean Patent Application filed in the Korean Intellectual Property Office on Jan. 21, 2008 and assigned Serial No. 10-2008-0006334, the contents of which are herein incorporated by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to a communication system. More particularly, the present invention relates to an apparatus and method for managing several Connection IDentifiers (CIDs) included in one mobile station (MS) in a communication system. 
     BACKGROUND OF THE INVENTION 
     A communication system allocates a Transport Connection IDentifier (TCID) on a per service-flow basis to each mobile station (MS). Thus, a base station (BS) can identify if packets received through TCIDs received from MSs located in a service area are for any service flow of any MS. For example, when an MS requests uplink bandwidth allocation, the MS requests an uplink bandwidth on the basis of a CID allocated to a service flow. A BS confirms the service flow requesting the uplink bandwidth through the CID received from the MS. 
     One MS includes several CIDs and, thus, can simultaneously transmit packets for several CIDs. For example, if requesting an uplink bandwidth, an MS constructs and transmits uplink bandwidth request information on several CIDs as shown in  FIG. 1 . That is, the MS constructs an uplink bandwidth request message for several CIDs using a generic Media Access Control (MAC) header and a band request header. 
       FIG. 1  is a diagram illustrating a structure for transmitting packets for a plurality of CIDs in an MS of a communication system according to the conventional art. The following description is made assuming that packets of a plurality of CIDs including a CID included in a generic MAC header are transmitted. 
     As shown in  FIG. 1 , if requesting an uplink bandwidth, an MS  110  constructs a message including uplink bandwidth allocation request information on a CID # 205  (hereinafter, referred to as “1 st  CID”)  101 , a CID # 302  (hereinafter, referred to as “2 nd  CID”)  103 , and a CID # 4331  (hereinafter, referred to as “3 rd  CID”)  105 . At this time, the MS  110  includes the bandwidth allocation request information on the 1 st  CID  101  included in a generic MAC header  120  using a grant management sub header  130  of 2 bytes. The MS  110  includes the bandwidth allocation request information on the 2 nd  CID  103  and 3 rd  CID  105  using bandwidth request headers  140  and  150  of 6 bytes. 
     Thus, the MS  110  concatenates and transmits the generic MAC header  120 , the grant management sub header  130 , the bandwidth request header  140 , and the bandwidth request header  150  to a BS. The generic MAC header  120  includes the 1 st  CID  101 . The grant management sub header  130  includes a bandwidth information  102  required by the 1 st  CID  101 . The bandwidth request header  140  includes a bandwidth information  104  required by the 2 nd  CID  103 , and the 2 nd  CID  103  information. The bandwidth request header  150  includes a bandwidth information  106  required by the 3 rd  CID  105 , and the 3 rd  CID  105  information. 
     The BS confirms the 1 st  CID  101  in the generic MAC header  120  of the message constructed as above, and confirms the bandwidth information  102  required by the 1 st  CID  101  in the grant management sub header  130 . The BS confirms the 2 nd  CID  103  and the bandwidth information  104  required by the 2 nd  CID  103  through the bandwidth request header  140 . The BS confirms the 3 rd  CID  105  and the bandwidth information  106  required by the 3 rd  CID  105  through the bandwidth request header  150 . 
     After that, the BS allocates an uplink bandwidth to the MS according to a bandwidth required by each of CIDs. 
     As described above, if one MS transmits packets for a plurality of CIDs, the MS uses a grant management sub header of 2 bytes for a CID included in a generic MAC header. Also, the MS transmits a packet using a separate header for CIDs not included in the generic MAC header and thus, there is a problem of increasing an overhead. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, it is a primary aspect of the present invention to substantially solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, one aspect of the present invention is to provide an apparatus and method for simultaneously transmitting packets of a plurality of Connection IDentifiers (CIDs) allocated to one mobile station (MS) in a communication system. 
     Another aspect of the present invention is to provide an apparatus and method for, when an MS simultaneously transmits packets of a plurality of CIDs, reducing an overhead using a piggyback CID index mapped to each CID in a communication system. 
     A further aspect of the present invention is to provide an apparatus and method for performing mapping between a plurality of CIDs allocated to one MS and piggyback CID indexes on a point-to-point basis for management in a communication system. 
     The above aspects are achieved by providing an apparatus and method for managing a CID in a communication system. 
     According to one aspect of the present invention, a method for managing a CID in an MS of a communication system is provided. The method includes mapping a unique index to at least one CID allocated by a base station (BS) and, if simultaneously transmitting packets for at least two CIDs, indexing a CID for packet transport by an index mapped to each CID and simultaneously transmitting packets for at least two CIDs. 
     According to another aspect of the present invention, a method for managing a CID in a BS of a communication system. The method includes mapping a different index to at least one CID allocated to at least one MS and, if receiving packets for at least two CIDs allocated to an MS, confirming CIDs for packet transport through indexes indexed in respective packets. 
     According to a further aspect of the present invention, an apparatus for managing a CID in an MS of a communication system is provided. The apparatus includes a controller and a transmitter. The controller maps a unique index to at least one CID allocated by a BS. If simultaneously transmitting packets for at least two CIDs, the transmitter indexes a CID for packet transport by an index mapped to each CID and simultaneously transmits packets for at least two CIDs. 
     According to a yet another aspect of the present invention, an apparatus for managing a CID in a BS of a communication system is provided. The apparatus includes a receiver and a controller. The receiver receives a signal. The controller maps a different index to at least one CID allocated to at least one MS and, if receiving packets for at least two CIDs allocated to an MS, confirms CIDs for packet transport through indexes indexed to respective packets. 
     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 
       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: 
         FIG. 1  is a diagram illustrating a structure for transmitting packets for a plurality of Connection IDentifiers (CIDs) in a mobile station (MS) of a communication system according to the conventional art; 
         FIGS. 2A and 2B  are diagrams illustrating mapping tables between CIDs and piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention; 
         FIG. 3  is a diagram illustrating a structure of a header used to transmit packets for a plurality of CIDs in an MS of a communication system according to an exemplary embodiment of the present invention; 
         FIG. 4  is a flow diagram illustrating a process of piggyback CID index mapping according to Dynamic Service Addition (DSA) in a communication system according to an exemplary embodiment of the present invention; 
         FIG. 5  is a flow diagram illustrating a process of piggyback CID index mapping according to DSA in a communication system according to another exemplary embodiment of the present invention; 
         FIGS. 6A ,  6 B, and  6 C are diagrams illustrating mapping tables for managing CIDs and mapped piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention; and 
         FIG. 7  is a block diagram illustrating a construction of an apparatus for managing CIDs and mapped piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 through 7 , 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. 
     A technology for managing piggyback Connection IDentifier (CID) indexes mapped to a plurality of CIDs allocated to one mobile station (MS) in a communication system according to an exemplary embodiment of the present invention is described below. The piggyback CID indexes represent indexes of CIDs allocated to Service Flows (SFs) of each MS. 
     A base station (BS) of a communication system manages CIDs using piggyback CID indexes each mapped to CIDs allocated to SFs of each MS. Also, an MS manages CIDs using piggyback CID indexes mapped to CIDs of SFs allocated by a BS. For example, the BS and MS manage CIDs by mapping piggyback CID indexes to the CIDs, respectively, as shown in  FIG. 2 . 
       FIGS. 2A and 2B  are diagrams illustrating mapping tables between CIDs and piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention. 
     In detail,  FIG. 2A  illustrates a structure for managing piggyback CID indexes mapped to respective CIDs in a BS, and  FIG. 2B  illustrates a structure for managing piggyback CID indexes mapped to respective CIDs in an MS. 
     As shown in  FIG. 2A , a BS includes mapping tables including piggyback CID indexes mapped to CIDs allocated to SFs of an MS  1  and an MS  2  that are located in a service area. 
     The BS manages a mapping table using a piggyback CID index pointer. That is, when mapping a CID to a piggyback CID index, the BS maps a CID to a piggyback CID index indicated by the piggyback CID index pointer of the mapping table. After that, the BS increases the piggyback CID index pointer by ‘1’ until finding a piggyback CID index not mapped to a CID. At this time, the BS performs a control such that the piggyback CID index pointer is within a given range. That is, if the piggyback CID index pointer is out of the given range, the BS sets the piggyback CID index pointer as an initial value. 
     As shown in  FIG. 2B , an MS includes a mapping table including piggyback CID indexes mapped to CIDs of SFs. 
     The MS manages the mapping table using a piggyback CID index pointer. That is, when mapping a CID to a piggyback CID index, the MS maps a CID to a piggyback CID index indicated by the piggyback CID index pointer of the mapping table. After that, the MS increases the piggyback CID index pointer by ‘1’ until finding a piggyback CID index not mapped to a CID. At this time, the MS performs a control such that the piggyback CID index pointer is within a given range. That is, if the piggyback CID index is out of the given range, the MS sets the piggyback CID index pointer as an initial value. 
     As described above, a BS and an MS manage CIDs by mapping the CIDs and piggyback CID indexes. Thus, when simultaneously transmitting packets of a plurality of CIDs for one MS, the MS transmits a plurality of packets using a piggyback CID index having a smaller size than a CID and, thus, can reduce an overhead. For example, if requesting an uplink bandwidth, an MS substitutes CIDs requesting the uplink bandwidth with piggyback CID indexes, thus being able to reduce a size of an uplink bandwidth request message. 
       FIG. 3  is a diagram illustrating a structure for transmitting packets for a plurality of CIDs in an MS of a communication system according to an exemplary embodiment of the present invention. The following description is made assuming that packets of a plurality of CIDs including a CID included in a generic MAC header are transmitted. 
     As shown in  FIG. 3 , an MS  310  constructs an uplink bandwidth request message in order to request uplink bandwidth allocation for a CID # 205  (hereinafter, referred to as “1 st  CID”)  301 , a CID # 302  (hereinafter, referred to as “2 nd  CID”)  303 , and a CID # 4331  (hereinafter, referred to as “3 rd  CID”)  305 . At this time, the MS  310  requests bandwidth allocation for the 1 st  CID  301  using a grant management sub header  330  of a type 1. The MS  310  requests bandwidth allocation for the 2 nd  CID  303  and 3 rd  CID  305  using grant management sub headers  340  and  350  of a type 2. 
     Thus, the MS  310  concatenates and transmits the generic MAC header  320  including the 1 st  CID  301 , the type-1 grant management sub header  330  for the 1 st  CID  301 , the type-2 grant management sub header  340  for the 2 nd  CID  303 , and the type-2 grant management sub header  350  for the 3 rd  CID  305  to a BS. The type-1 grant management sub header  330  includes a total number of CIDs requiring uplink bandwidth allocation, and bandwidth information required by the 1 st  CID  301 . The type-2 grant management sub header  340  for the 2 nd  CID  303  includes the piggyback CID index information mapped to the 2 nd  CID  303  and bandwidth information required by the 2 nd  CID  303 . The type-2 grant management sub header  350  for the 3 rd  CID  305  includes piggyback CID index information mapped to the 3 rd  CID  305  and bandwidth information required by the 3 rd  CID  305 . 
     The BS confirms the 1 st  CID  301  in the generic MAC header  320  of the uplink bandwidth request message constructed as above, and confirms the number  361  of CIDs requesting a bandwidth and bandwidth information  363  required by the 1 st  CID  301  in the type-1 grant management sub header  330 . Also, the BS confirms the 2 nd  CID information  371  mapped to the piggyback CID index of the type-2 grant management sub header  340  and bandwidth information  373  required by the 2 nd  CID  303 . Also, the BS confirms the 3 rd  CID  305  mapped to the piggyback CID index of the type-2 grant management sub header  350  and bandwidth information required by the 3 rd  CID  305 . 
     After that, the BS allocates an uplink bandwidth to the MS depending on the bandwidth information required by the respective CIDs. 
     As shown in  FIGS. 4 and 5 , a BS and an MS map a piggyback CID index to each CID. The following description is made assuming that a piggyback CID index is mapped to a CID through Dynamic Service Addition (DSA). If the BS sends a DSA request to the MS, the MS performs a piggyback CID index mapping process of  FIG. 4 , and the BS performs a piggyback CID index mapping process of  FIG. 5 . 
     If an MS sends a DSA request to a BS, the BS performs a piggyback CID index mapping process of  FIG. 4 , and the MS performs a piggyback CID index mapping process of  FIG. 5 . The following description is made assuming that the BS sends a DSA request to the MS. Thus, the MS maps a piggyback CID index to an added CID as shown in  FIG. 4 . 
       FIG. 4  is a flow diagram illustrating a process of piggyback CID index mapping according to DSA in a communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , in step  401 , an MS confirms if a DSA REQuest signal (DSA REQ) is received from a BS. 
     If the DSA REQ is received, in step  403 , the MS transmits a DSA ReSPonse signal (DSA RSP) responsive to the DSA REQ to the BS. 
     Then, in step  405 , the MS drives a timer expiring after a predetermined time. 
     Then, in step  407 , the MS confirms if a DSA ACKnowledgement signal (DSA ACK) responsive to the DSA RSP is received before the timer expires. 
     If the DSA ACK responsive to the DSA RSP is not received before the driven timer of step  405  expires, the MS returns to step  403  and again transmits a DSA RSP to the BS. At this time, the MS resets the timer. 
     If the DSA ACK responsive to the DSA RSP is received before the driven timer of step  405  expires, the MS goes to step  409  and confirms a piggyback CID index indicated by a piggyback CID index pointer in a mapping table. 
     Then, in step  411 , the MS map the piggyback CID index indicated by the piggyback CID index pointer to a CID newly allocated by the BS according to DSA. 
     After mapping the piggyback CID index to the newly allocated CID, in step  413 , the MS increases a piggyback CID index pointer. At this time, the MS increases the piggyback CID index pointer by ‘1’. 
     After increasing the piggyback CID index pointer, in step  415 , the MS confirms if the increased piggyback CID index pointer is within a range of a piggyback CID index pointer. 
     If the increased piggyback CID index pointer of step  413  is within the range of the piggyback CID index pointer, the MS goes to step  419  and confirms if there is a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer. 
     If the increased piggyback CID index pointer of step  413  is out of the range of the piggyback CID index pointer, the MS goes to step  417  and initializes the piggyback CID index pointer. That is, the MS sets the piggyback CID index pointer as an initial value. 
     After initializing the piggyback CID index pointer, in step  419 , the MS confirms if there is a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer. 
     If there is a TCID mapped to the piggyback CID index indicated by the piggyback CID index pointer in step  419 , the MS returns to step  413  and increases the piggyback CID index pointer. 
     If there is not a TCID mapped to the piggyback CID index indicated by the piggyback CID index pointer in step  419 , the MS terminates the process according to an exemplary embodiment of the present invention. 
     As described above, if an MS maps a piggyback CID index to a CID, a BS requesting DSA maps a piggyback CID index to a CID as shown in  FIG. 5 . 
       FIG. 5  is a flow diagram illustrating a process of piggyback CID index mapping according to DSA in a communication system according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , in step  501 , a BS transmits a DSA REQ to an MS so as to request DSA. 
     After transmitting the DSA REQ, in step  503 , the BS confirms if a DSA RSP responsive to the DSA REQ is received from the MS. 
     If the DSA RSP is received, in step  505 , the BS transmits a DSA ACK responsive to the DSA RSP to the MS. 
     Then, in step  507 , the BS drives a timer expiring after a predetermined time. 
     Then, in step  509 , the BS confirms if a DSA RSP responsive to a DSA REQ is again received before the timer expires. 
     If the DSA RSP responsive to the DSA REQ is again received before the driven timer of step  507  expires, the BS returns to step  505  and again transmits a DSA ACK responsive to the DSA RSP to the MS. At this time, the BS resets the timer. 
     If the DSA RSP responsive to the DSA REQ is not received before the driven timer of step  509  expires, the BS goes to step  511  and confirms a piggyback CID index indicated by a piggyback CID index pointer. 
     Then, in step  513 , the BS maps the piggyback CID index indicated by the piggyback CID index pointer to a CID newly allocated to the MS according to DSA. 
     After mapping the piggyback CID index to the CID, in step  515 , the BS increases the piggyback CID index pointer. At this time, the BS increases the piggyback CID index pointer by ‘1’. 
     After increasing the piggyback CID index pointer, in step  517 , the BS confirms if the increased piggyback CID index pointer is within a range of a piggyback CID index pointer. 
     If the increased piggyback CID index pointer of step  515  is within the range of the piggyback CID index pointer, the BS goes to step  521  and confirms if there is a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer. 
     If the increased piggyback CID index pointer of step  515  is out of the range of the piggyback CID index pointer, the BS goes to step  519  and initializes the piggyback CID index pointer. That is, the BS sets the piggyback CID index pointer as an initial value. 
     After initializing the piggyback CID index pointer, in step  521 , the BS confirms if there is a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer. 
     If there is a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer in step  521 , the BS returns to step  515  and increases the piggyback CID index pointer. 
     If there is not a TCID mapped to a piggyback CID index indicated by the piggyback CID index pointer in step  521 , the BS terminates the process according to an exemplary embodiment of the present invention. 
     As described above, a BS and an MS map a piggyback CID index to a CID added according to DSA, and update a mapping table. Also, the BS and the MS unmap a piggyback CID index mapped to a CID deleted according to DSD, and update the mapping table. 
       FIGS. 6A ,  6 B, and  6 C are diagrams illustrating mapping tables for managing CIDs and mapped piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention. 
     In detail,  FIG. 6A  illustrates mapping tables managed in a BS and an MS,  FIG. 6B  illustrates mapping tables updated according to DSD, and  FIG. 6C  illustrates mapping tables updated according to DSA. 
     As shown in  FIG. 6A , a BS constructs a mapping table including piggyback CID index information mapped to CIDs allocated to SFs of an MS. Also, the MS constructs a mapping table including piggyback CID index information mapped to CIDs of SFs allocated by the BS. The piggyback CID index information mapped to the CIDs, which are included in the mapping tables of the BS and MS, are the same as each other. For example, the mapping tables of the BS and MS include the same information on a piggyback CID index # 1  mapped to a CID # 100  of an SF # 1 . 
     As shown in  FIG. 6B , if performing DSD for a CID # 200 , a BS deletes the CID # 200  mapped to a piggyback CID index # 2  from a mapping table. Also, an MS deletes the CID # 200  mapped to a piggyback CID index # 2  from a mapping table. 
     If performing DSA for a CID # 400  in the mapping table of  FIG. 6B , the BS maps the CID # 400  to a piggyback CID index # 4  indicated by a piggyback CID index pointer as shown in  FIG. 5  or  6 . Also, the MS maps the CID # 400  to a piggyback CID index # 4  indicated by a piggyback CID index pointer as shown in  FIG. 5  or  6 . 
     As described above, an MS and a BS are constructed as shown in  FIG. 7  so as to map and manage CIDs and piggyback CID indexes. Constructions of the MS and BS for mapping and managing the CIDs and piggyback CID indexes are the same as each other and thus, the constructions of the MS and BS are described using  FIG. 7 . 
       FIG. 7  is a block diagram illustrating a construction of an apparatus for managing CIDs and mapped piggyback CID indexes in a communication system according to an exemplary embodiment of the present invention. The communication system is described assuming that a Time Division Duplexing (TDD) scheme is used. 
     As shown in  FIG. 7 , an MS includes a radio frequency (RF) switch  701 , a receiver  703 , a message processor  705 , a controller  707 , a timer  709 , a storage unit  711 , a message generator  713 , and a transmitter  715 . 
     The RF switch  701  performs switching such that an antenna and the receiver  703  connect with each other to receive a signal in a reception mode. The RF switch  701  performs switching such that the transmitter  715  and the antenna connect with each other to transmit a signal in a transmission mode. 
     The receiver  703  converts a high frequency signal received through the RF switch  701  into a baseband signal. 
     The message processor  705  processes a control message received from the receiver  703  and provides the results to the controller  707 . For example, if the MS requests DSA, the message processor  705  provides the controller  707  with a DSA response message received from a BS responsive to a DSA request. If the BS requests DSA, the message processor  705  provides a DSA request message received from the BS and a DSA acknowledgement message responsive to the DSA request message to the controller  707 . 
     The controller  707  performs mapping between CIDs by SF and piggyback CID indexes according to a control message received from the message processor  705 . 
     The controller  707  manages mapping between the CIDs and the piggyback CID indexes according to DSA and DSD. For example, if performing DSA, the controller  707  maps a piggyback CID index indicated by a piggyback CID index pointer to a CID allocated by a BS according to DSA. 
     In another exemplary embodiment of the present invention, if performing DSD, the controller  707  deletes a CID from a mapping table stored in the storage unit  711  according to DSD. 
     The timer  709  operates under the control of the controller  707  and automatically expires after a predetermined time. For example, if a BS requests DSA, the timer  709  is reset at a time a DSA response signal responsive to a DSA request message is transmitted under the control of the controller  707 . If an MS requests DSA, the timer  709  is reset at a time a DSA acknowledgement signal responsive to a DSA response signal responsive to a DSA request message is transmitted under the control of the controller  707 . 
     The storage unit  711  generates and updates a mapping table under the control of the controller  707  as shown in  FIG. 6 . 
     The message generator  713  generates a control message transmitted to a BS under the control of the controller  707 . For example, if an MS requests DSA, the message generator  713  generates a DSA request message and a DSA acknowledgement message responsive to the DSA request message under the control of the controller  707 . If a BS requests DSA, the message generator  713  generates a DSA response message responsive to a DSA request message under the control of the controller  707 . 
     In another example, if requesting an uplink bandwidth, the message generator  713  generates an uplink bandwidth request message of indexing CIDs requesting uplink bandwidths with piggyback CID indexes. At this time, the message generator  713  generates an uplink bandwidth request message constructed as shown in  FIG. 3 . 
     The transmitter  715  converts a control message received from the message generator  713  and transmission data into a high frequency signal, and transmits the converted signal to a BS through the RF switch  701  and the antenna. 
     In the case of a BS, the BS includes an RF switch  701 , a receiver  703 , a message processor  705 , a controller  707 , a timer  709 , a storage unit  711 , a message generator  713 , and a transmitter  715 . 
     The RF switch  701  performs switching such that an antenna and the receiver  703  connect with each other to receive a signal in a reception mode. The RF switch  701  performs switching such that the transmitter  715  and the antenna connect with each other to transmit a signal in a transmission mode. 
     The receiver  703  converts a high frequency signal received through the RF switch  701  into a baseband signal. 
     The message processor  705  processes a control message received from the receiver  703  and provides its result to the controller  707 . For example, if an MS requests DSA, the message processor  705  provides a DSA request message received from the MS and a DSA acknowledgement message responsive to the DSA request message to the controller  707 . If a BS requests DSA, the message processor  705  provides a DSA response message responsive to the DSA request message received from the MS, to the controller  707 . 
     The controller  707  performs mapping between CIDs by SF and piggyback CID indexes according to a control message received from the message processor  705 . 
     The controller  707  manages mapping between the CIDs and the piggyback CID indexes according to DSA and DSD. For example, if performing DSA, the controller  707  maps a piggyback CID index indicated by a piggyback CID index pointer to a CID allocated to an MS according to DSA. 
     In another exemplary embodiment of the present invention, if performing DSD, the controller  707  deletes a CID from a mapping table stored in the storage unit  711  according to DSD. 
     Also, if an MS requests an uplink bandwidth, the controller  707  confirms CIDs requesting uplink bandwidths according to piggyback CID indexes included in an uplink bandwidth request message received from the message processor  705 . 
     The timer  709  operates under the control of the controller  707  and automatically expires after a predetermined time. For example, if a BS requests DSA, the timer  709  is reset at a time a DSA acknowledgement signal responsive to a DSA response message responsive to a DSA request message is transmitted under the control of the controller  707 . If an MS requests DSA, the timer  709  is reset at a time a DSA response signal responsive to a DSA request message is transmitted under the control of the controller  707 . 
     The storage unit  711  generates and updates a mapping table under the control of the controller  707  as shown in  FIG. 6 . 
     The message generator  713  generates a control message transmitted to an MS under the control of the controller  707 . For example, if an MS requests DSA, the message generator  713  generates a DSA response message responsive to a DSA request message under the control of the controller  707 . If a BS requests DSA, the message generator  713  generates a DSA request message and a DSA acknowledgement message responsive to the DSA request message under the control of the controller  707 . 
     The transmitter  715  converts a control message received from the message generator  713  and transmission data into a high frequency signal, and transmits the converted signal to an MS through the RF switch  701  and the antenna. 
     As described above, an exemplary embodiment of the present invention has an advantage of, when transmitting packets for a plurality of CIDs, being able to reduce an overhead using a piggyback CID index not the CID by mapping a CID allocated to an MS on a per service-flow basis to each piggyback CID index and updating the mapping information according to DSA or DSD in a communication system. 
     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.