Abstract:
A method is provided for allocating resources by a Base Station (BS) in a wireless communication system. The method includes persistently allocating one or more resource slots among a plurality of resource slots, the persistently allocated one or more resource slots being allocated to corresponding one or more Mobile Stations (MSs), de-allocating at least one persistently allocated resource slot of the one or more persistently allocated resource slots, determining whether a hole is created due to the de-allocation among the one or more persistently allocated resource slots not de-allocated, and shifting a location of at least one of the one or more non-de-allocated persistently allocated resource slots when it is determined that the hole is created due to the de-allocation.

Description:
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. 18, 2007 and assigned Serial No. 2007-105287, a Korean patent application filed in the Korean Intellectual Property Office on Jan. 4, 2008 and assigned Serial No. 2008-1491, and a Korean patent application filed in the Korean Intellectual Property Office on Aug. 20, 2008 and assigned Serial No. 2008-81602, the entire disclosure of each of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention The present invention relates to a method and apparatus for allocating resources in a wireless communication system and a system thereof. More particularly, the present invention relates to a method and apparatus for allocating resources in a wireless communication system using a persistent resource allocation scheme and a system thereof. 
     2. Description of the Related Art 
     Next-generation communication systems are being developed to provide various high-speed, high-capacity services to Mobile Stations (MSs). A next-generation communication system includes an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system and a Mobile Worldwide Interoperability for Microwave Access (WiMAX) communication system. The Mobile WiMAX communication system is a communication system based on the IEEE 802.16 communication system. 
     With reference to  FIG. 1 , a description will now be made of a frame structure in an IEEE 802.16 communication system. 
       FIG. 1  is a diagram illustrating a frame structure in an IEEE 802.16 communication system. 
     As illustrated in  FIG. 1 , a frame  111  includes a DownLink (DL) subframe  113 , a Transmit/Receive Transition Gap (TTG) interval  115 , an UpLink (UL) subframe  117 , and a Receive/Transmit Transition Gap (RTG) interval  119 . A length of the frame  111  is t frame , a length of the DL subframe  113  is t DL     —     subframe , a length of the TTG interval  115  is t TTG , a length of the UL subframe  117  is t UL     —     subframe , and a length of the RTG interval  119  is t RTG . 
     The DL subframe  113  includes a preamble region  121 , a Frame Control Header (FCH) region  123 , a DL_MAP region  125 , a UL_MAP region  127 , and a DL data burst region  129 . A synchronization signal, e.g., preamble signal, for synchronization acquisition between a signal transmission apparatus, e.g., a Base Station (BS), and a signal reception apparatus, e.g., a MS, is transmitted during the preamble region  121 . Basic information on subchannels, ranging and a modulation scheme is transmitted during the FCH region  123 . A DL_MAP message is transmitted during the DL_MAP region  125 , and a UL_MAP message is transmitted during the UL_MAP region  127 . The DL_MAP message includes a DL_MAP Information Element (IE) indicating information about the DL data burst region  129 . The UL_MAP message includes a UL_MAP IE indicating information about a UL data burst region  133 . DL data bursts are transmitted during the DL data burst region  129 . 
     The UL subframe  117  includes a control region  131  and the UL data burst region  133 . Although not separately illustrated in  FIG. 1 , the control region  131  includes a ranging region, a Channel Quality Indicator Channel (CQICH) region, an ACKnowledgment (ACK) channel (ACKCH) region, and a sounding region. The ranging region is a region during which an MS transmits a ranging code, and when performing an initial network entry operation, performing a handoff operation or requesting resource allocation, an MS transmits a ranging code through the ranging region according to its purpose. The CQICH region indicates a region during which an MS transmits its CQI, and the ACKCH region indicates a region during which an MS transmits its success/failure in reception of DL data bursts. A sounding signal for allowing an MS to perform UL channel estimation is transmitted during the sounding region. 
     As described in  FIG. 1 , the IEEE 802.16 communication system allocates resources to an MS to exchange DL and UL traffic data with it, and provides the resource allocation information to the MS using a resource allocation message. The resource allocation message can be a DL_MAP message or a UL_MAP message. A transmission period of the DL_MAP message and UL_MAP message is a frame period. 
     However, in the service where traffic data is periodically transmitted to an MS, for example, in Voice over Internet Protocol (VoIP) service, BSs transmitting a resource allocation message at every frame to transmit resource allocation information for the resources allocated to the corresponding MS may cause an unnecessary waste in resources. Therefore, when providing a service having a periodic traffic transmission period like the VoIP service, it is preferable to persistently allocate resources for the corresponding MS. A scheme of persistently allocating resources for a particular MS is referred to as a ‘persistent resource allocation scheme’. For convenience, the persistent resource allocation scheme will be referred to herein as a ‘circuit-mode resource allocation scheme’. 
     When using the circuit-mode resource allocation scheme, an MS, once it is allocated resources from a BS, can persistently use the allocated resources without receiving the resource allocation message at every frame. Of course, when the resource allocation for the MS is changed or released, the BS can notify the MS of the change and release of the resource allocation using a separate resource allocation message. As a result, when using the circuit-mode resource allocation scheme, the BS has no need to transmit the resource allocation message at every frame, thereby making it possible to prevent the waste of resources caused by the transmission of the resource allocation message. 
     With reference to  FIG. 2 , a description will now be made of a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system. 
       FIG. 2  is a diagram schematically illustrating a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system. 
     Before a description of  FIG. 2  is given, it should be noted that the IEEE communication system uses two resource allocation schemes, namely a packet-mode resource allocation scheme and a circuit-mode resource allocation scheme. Referring to  FIG. 2 , both a resource allocation method based on the packet-mode resource allocation scheme and a resource allocation method based on the circuit-mode resource allocation scheme are illustrated. For convenience, however, a description of the resource allocation method based on the packet-mode resource allocation scheme will be omitted herein. For convenience, resources allocated using the circuit-mode resource allocation scheme will be referred to as ‘circuit-mode resources’. 
     The slot numbers referred to herein and illustrated in  FIGS. 2 and 3  are numbered separately for each of the packet-mode resource allocation scheme and the circuit-mode resource allocation scheme in order to simplify the explanation. The slot numbers for the packet-mode resource allocation scheme are numbered in the same direction as the resource allocation beginning with the first slot used for the packet-mode resource allocation scheme. The slot numbers for the circuit-mode resource allocation scheme are numbered in the opposite direction to the resource allocation beginning with the last slot used for the packet-mode resource allocation scheme. The slot numbers used herein are merely for the purpose of explanation and any other slot numbering scheme may equally be used, such as numbering all of the slots of a subframe. Further, the direction of the resource allocation is merely an example, as at least one of the packet-mode resource allocation scheme and circuit-mode resource allocation scheme may employ a resource allocation in a direction opposite to that described herein. 
     Referring to  FIG. 2 , when resources are allocated for UL data bursts included in a UL subframe using the circuit-mode resource allocation scheme, UL resources are allocated slot by slot beginning from a start offset. The start offset indicates a location from which the BS starts allocating UL resources using the circuit-mode resource allocation scheme, and a slot # 10  assumed to be the start offset in  FIG. 2 . A detailed description of the start offset will be given below. 
     For example, in  FIG. 2 , a circuit-mode resource # 1  includes 2 slots in the forward direction from slot # 10 , which in this example is the start offset, a circuit-mode resource # 2  includes 2 slots in the forward direction from a slot # 8 , which is the next slot of the slots included in the circuit-mode resource # 1 , and a circuit-mode resource # 3  includes 6 slots in the forward direction from a slot # 6 , which is the next slot of the slots included in the circuit-mode resource # 2 . 
     However, the use of the circuit-mode resource allocation scheme described in  FIG. 2  may cause a reduction in resource efficiency, which will be described with reference to  FIG. 3 . 
       FIG. 3  is a diagram illustrating a case where a circuit-mode resource is de-allocated in an IEEE 802.16 communication system. 
     Referring to  FIG. 3 , it is assumed that the circuit-mode resource # 2  among the 3 circuit-mode resources allocated in  FIG. 2  is de-allocated. It is also assumed that after the circuit-mode resource # 2  is de-allocated, a circuit-mode resource # 4 , or a new circuit-mode resource, may be allocated. The number of slots included in the circuit-mode resource # 4  is assumed to be 4. In this case, the number of slots included in the circuit-mode resource # 4  exceeds the number  2  of slots included in the de-allocated circuit-mode resource # 2 . Therefore, the circuit-mode resource # 4  cannot use the slots which were included in the circuit-mode resource # 2 , and should therefore include new slots following the circuit-mode resource # 3  that as illustrated in  FIG. 3  would comprise larger slot numbers than the start offset. The slots included in the circuit-mode resource # 4  include 4 slots in the forward direction from a slot # 14 , which is the new start offset. As a result, the 2 slots of a slot # 8  and a slot # 7 , which were included in the de-allocated circuit-mode resource # 2 , become a hole, and the hole is an unavailable resource. 
     As described in  FIG. 3 , the use of the circuit-mode resource allocation scheme may cause creation of the hole, impeding continuity of resource allocation. The creation of the hole reduces the resource efficiency, resulting in a decrease in efficiency of the IEEE 802.16 communication system. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is 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 a method and apparatus for allocating resources in a wireless communication system, and a system thereof. 
     Another aspect of the present invention is to provide a method and apparatus for allocating resources to prevent the creation of a hole when a circuit-mode resource allocation scheme is used in a wireless communication system, and a system thereof. 
     According to another aspect of the present invention, a Base Station (BS) apparatus in a wireless communication system is provided. The apparatus includes a controller for generating a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots to corresponding one or more Mobile Stations (MSs), and when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, for generating a message including information on the at least one de-allocated resource slot and the resource move indicator, and a transmitter for transmitting the resource allocation message and the message to at least one MS. 
     According to yet another aspect of the present invention, a Mobile Station (MS) apparatus in a wireless communication system is provided. The apparatus includes a receiver for receiving a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots, and when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, for receiving a message including information on the at least one de-allocated resource slot and the resource move indicator. 
     According to still another aspect of the present invention, a wireless communication system is provided. The system includes a Base Station (BS) for transmitting a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots to corresponding one or more Mobile Stations (MSs), and when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, for transmitting a message including information on the at least one de-allocated resource slot and the resource move indicator, to the one or more MSs, and the one or more MSs for receiving the resource allocation message and the message. 
     According to still another aspect of the present invention, a method for allocating resources by a Base Station (BS) in a wireless communication system is provided. The method includes transmitting a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots to corresponding one or more Mobile Stations (MSs), and when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, transmitting a message including information on the at least one de-allocated resource slot and the resource move indicator, to at least one MS. 
     According to still another aspect of the present invention, a method for allocating resources by a Mobile Station (MS) in a wireless communication system is provided. The method includes receiving a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots, and when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, receiving a message including information on the at least one de-allocated resource slot and the resource move indicator. 
     According to still another aspect of the present invention, a method for allocating resources in a wireless communication system is provided. The method includes transmitting, by a Base Station (BS), a resource allocation message including a resource move indicator indicating whether it is possible to shift at least one persistently allocated resource slot of one or more persistently allocated resource slots to persistently allocate at least one resource slot among a plurality of resource slots to corresponding one or more Mobile Stations (MSs), receiving, by the corresponding one or more MSs, the resource allocation message, when at least one persistently allocated resource slot of the one or more persistently allocated resource slots is de-allocated, transmitting, by the BS, a message including information on the at least one de-allocated resource slot and the resource move indicator, to at least one MS, and receiving, by the at least one MS, the message. 
     Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating a frame structure in an IEEE 802.16 communication system; 
         FIG. 2  is a diagram schematically illustrating a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system; 
         FIG. 3  is a diagram illustrating a case where a circuit-mode resource is de-allocated in an IEEE 802.16 communication system; 
         FIG. 4  is a diagram schematically illustrating an example of a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention; 
         FIG. 5  is a diagram illustrating a method in which MSs, which have received a UL Persistent Allocation_IE, re-set a location of slots included in circuit-mode resources according to the UL Persistent Allocation_IE, according to an exemplary embodiment of the present invention; 
         FIG. 6  is a diagram illustrating a method in which MSs, which have received a UL Persistent Allocation_IE, re-set a location of slots included in a circuit-mode resource according to the UL Persistent Allocation_IE, and then allocate new circuit-mode resources, according to an exemplary embodiment of the present invention; 
         FIG. 7  is a diagram schematically illustrating an example of a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention; 
         FIG. 8  is a diagram illustrating a case where a circuit-mode resource is de-allocated, according to an exemplary embodiment of the present invention; 
         FIG. 9  is a flowchart illustrating a process in which an MS, which has already been allocated circuit-mode resources, changes a location of circuit-mode resources, in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention; 
         FIG. 10  is a diagram illustrating an internal structure of a BS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention; and 
         FIG. 11  is a diagram illustrating an internal structure of an MS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
     
    
    
     Therefore, a need exists for an improved image forming apparatus capable of double-sided printing with one printing module. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the present invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
     Exemplary embodiments of the present invention provide a method and apparatus for allocating resources in a wireless communication system, and a system thereof. Further, exemplary embodiments of the present invention provide a resource allocation method and apparatus for increasing resource efficiency by allocating resources to prevent creation of a hole(s) when a persistent resource allocation scheme is used as a resource allocation scheme in a wireless communication system, and a system thereof. For convenience, the persistent resource allocation scheme will be referred to as a ‘circuit-mode resource allocation scheme’. Although an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system will be described herein as an example of a wireless communication system, the resource allocation method and apparatus and a system thereof, proposed by exemplary embodiments of the present invention, can be used not only in the IEEE 802.16 communication system, but also in other wireless communication systems such as a Mobile Worldwide Interoperability for Microwave Access (WiMAX) communication system. 
     The slot numbers referred to herein and illustrated in  FIGS. 4-8  are numbered separately for each of the packet-mode resource allocation scheme and the circuit-mode resource allocation scheme in order to simplify the explanation. The slot numbers for the packet-mode resource allocation scheme are numbered in the same direction as the resource allocation beginning with the first slot used for the packet-mode resource allocation scheme. The slot numbers for the circuit-mode resource allocation scheme are numbered in the opposite direction to the resource allocation beginning with the last slot used for the packet-mode resource allocation scheme. The slot numbers used herein are merely for the purpose of explanation and any other slot numbering scheme may equally be used, such as numbering all of the slots of a subframe. Further, the direction of the resource allocation is merely an example, as at least one of the packet-mode resource allocation scheme and circuit-mode resource allocation scheme may employ a resource allocation in a direction opposite to that described herein. 
       FIG. 4  is a diagram schematically illustrating a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
     Before a description of  FIG. 4  is given, it should be noted that the IEEE communication system uses two resource allocation schemes, namely a packet-mode resource allocation scheme and a circuit-mode resource allocation scheme. Referring to  FIG. 4 , both a resource allocation method based on the packet-mode resource allocation scheme and a resource allocation method based on the circuit-mode resource allocation scheme are illustrated. For convenience, however, a description of the resource allocation method based on the packet-mode resource allocation scheme will be omitted herein. For convenience, resources allocated using the circuit-mode resource allocation scheme will be referred to as ‘circuit-mode resources’, and the minimum allocation unit of resources allocated using the circuit-mode resource allocation scheme can be referred to as a slot. 
     Referring to  FIG. 4 , it will be assumed that a total of 2 circuit-mode resources, i.e., a circuit-mode resource # 1  and a circuit-mode resource # 3 , are allocated and one circuit-mode resource, i.e., a circuit-mode resource # 2 , is de-allocated in a UpLink (UL) data burst region included in a UL subframe. Referring to  FIG. 4 , a start offset is slot # 10 , and the start offset indicates a location from which a BS starts allocating UL resources using the circuit-mode resource allocation scheme. A detailed description of the start offset will be given below. When resources are allocated using the circuit-mode resource allocation scheme as illustrated in  FIG. 4 , slots included in the de-allocated resource become a hole, and the hole becomes unavailable resources, causing a reduction in the resource efficiency. 
     Therefore, exemplary embodiments of the present invention newly propose a UL circuit-mode resource allocation message, i.e., UL Persistent Allocation_Information Element (UL Persistent Allocation_IE), including a Release Resource Move indicator indicating a release of resource allocation, in order to use the hole. That is, exemplary embodiments of the present invention propose a method in which, in order to use the hole, a BS shifts the location of the allocated circuit-mode resource(s) other than the de-allocated circuit-mode resource to prevent the creation of the hole, and informs MSs of the shift before they shift the circuit-mode resource so that the MSs can also shift the circuit-mode resource allocated to themselves. 
     A format of the UL Persistent Allocation_IE can be made as shown in Table 1. 
     
       
         
               
               
             
               
             
               
               
             
               
               
               
             
               
             
               
               
             
               
               
             
               
               
             
               
             
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Fields 
                 Description 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 UL Persistent Allocation_IE( ) { 
               
             
          
           
               
                   
                 Extended-2 UIUC 
               
               
                   
                 Length 
               
             
          
           
               
                   
                 UL Persistent Allocation IE 
                 Ox01 
               
               
                   
                 Release Resource Move indicator 
               
               
                   
                 Burst level start offset 
               
             
          
           
               
                 if (Burst level start offset=1) { 
               
             
          
           
               
                   
                 Start offset 
               
               
                   
                 } 
               
             
          
           
               
                 N_Burst 
                 Number of UL circuit-mode 
               
             
          
           
               
                   
                 control messages 
               
             
          
           
               
                 For (i=0; i&lt;N_Burst; i++) { 
               
               
                 UL Persistent Allocation subburst IE 
               
               
                 .. 
               
               
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     Before a description of Table 1 is given, it should be noted that in the IEEE 802.16 communication system, since circuit-mode resources are allocated in the UL in a one-dimensional manner, the UL Persistent Allocation_IE has no need to include a Region Identifier (ID), or region size/location information. 
     In Table 1, Extended-2 Uplink Interval Usage Code (UIUC) indicates Extended-2 UIUC of the UL Persistent Allocation_IE, and Length indicates a length of the UL Persistent Allocation_IE. Further, Burst level start offset is used for setting a start offset in front of a UL Persistent Allocation subburst IE in order to express the subburst to be allocated next, in duration. That is, Burst level start offset indicates if the UL Persistent Allocation_IE includes a Start offset of a subburst corresponding to the UL Persistent Allocation subburst IE included in the UL Persistent Allocation_IE. For example, if the Burst level start offset is set to a defined value, for example, 1, it indicates that the UL Persistent Allocation_IE includes a Start offset just after the Burst level start offset. 
     The Start offset, as described above, indicates a location from which circuit-mode resource allocation is started. Since circuit-mode resources are allocated in the UL in a one-dimensional manner, the Start offset can be represented in a one-dimensional manner, or can be represented using Orthogonal Frequency Division Multiple Access (OFDMA) symbol location and subchannel location. For convenience, it is assumed herein that the start offset is represented by the location of a slot. Unlike the foregoing description, it is also possible to notify of the Start offset by transmitting a UL Allocation start IE before transmitting the UL Persistent Allocation_IE. 
     When the UL Persistent Allocation_IE includes an enabled Release Resource Move indicator, i.e., when a value of the Release Resource Move indicator is set to a defined value, for example, 1, MSs other than the MS whose resources are actually de-allocated, detect the location of the de-allocated resources using the UL Persistent Allocation subburst IE. In this way, the MSs can detect the location of the resources allocated to themselves. A detailed description thereof will be given below. 
     When a value of Release Resource Move indicator is set to ‘1’, all MSs determine whether they should shift the location of the circuit-mode resources allocated to themselves using the UL Persistent Allocation subburst IE. If it is determined that the MSs should shift the location of the circuit-mode resources allocated to themselves, and if the resources de-allocated according to the UL Persistent Allocation subburst IE are located behind the resources allocated to themselves, the MSs shift back the resources allocated to themselves by a size of the de-allocated resources. That is, a UL Persistent Allocation subburst IE targeting another MS is used as resource shift information for the resources allocated to the MS itself, and a description thereof will be given below with reference to  FIG. 4 . 
     Assume that in the state where slot # 7  and slot # 8  are allocated to an MS # 1 , a BS sets a value of Release Resource Move indicator to ‘1’ in order to de-allocate slot # 7  and slot # 8 , and then transmits a UL Persistent Allocation subburst IE along with the UL Persistent Allocation_IE. In this case, an MS # 2  using a slot # 9  to slot # 10  can detect the de-allocation of slot # 7  and slot # 8  by receiving the UL Persistent Allocation_IE. Determining that the de-allocated slot # 7  and slot # 8  are located at slot numbers that are lower than slot numbers used by the MS # 2  itself, the MS # 2  shifts the location of the its resources by 2 slots which corresponds to a size of the de-allocated resources, and then uses slot # 7  to slot # 8 . 
     Further, in Table 1, an N_Burst field indicates the number of UL Persistent Allocation subburst IEs included in the UL Persistent Allocation_IE. The UL Persistent Allocation subburst IE is a sub resource allocation message for controlling all circuit-mode resource allocation operations of allocating resources to MSs using the circuit-mode resource allocation scheme, de-allocating the circuit-mode resources allocated to the MSs, and changing the circuit-mode resources allocated to the MSs. 
     A format of the UL Persistent Allocation subburst IE can be made as shown in Table 2. It should be noted in Table 2 that the UL Persistent Allocation subburst IE is written as UL Persistent HARQ chase_Subburst_IE. 
     
       
         
               
               
               
             
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
             
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
               
             
               
               
               
             
               
               
               
             
               
               
             
               
               
             
               
               
               
               
             
               
             
               
               
             
               
               
               
             
               
               
             
               
             
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Length 
                   
               
               
                 Fields 
                 (bits) 
                 Description 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 UL Persistent HARQ 
               
               
                 chase_Subburst_IE( ) { 
               
             
          
           
               
                   
                 RCID IE 
               
             
          
           
               
                   
                 Allocation Flag 
                 0: New Resource Assignment 
               
             
          
           
               
                   
                 1: Resource Release 
               
             
          
           
               
                   
                 Dedicated UL Control Indicator 
                 1 
               
             
          
           
               
                 if (Dedicated UL Control 
               
               
                 Indicator=1){ 
               
               
                 Dedicated UL Control IE 
               
               
                 } 
               
             
          
           
               
                   
                 if (burst level start offset=0){ 
               
             
          
           
               
                   
                 Subburst level start offset 
                 Start offset for current Subburst, 
               
             
          
           
               
                   
                 when burst level start offset=1, 
               
               
                   
                 start offset for each subburst is 
               
               
                   
                 referred from the end of the 
               
               
                   
                 previously allocated subburst 
               
             
          
           
               
                   
                 } 
               
             
          
           
               
                   
                 Duration 
                 Allocation duration 
               
             
          
           
               
                   
                 Period 
                 Allocation Period 
               
               
                   
                 Expire 
                 Allocation Expire 
               
             
          
           
               
                   
                 Start ACID 
                 Start ACID 
               
             
          
           
               
                 # of ACID 
                 Number of ACID 
               
             
          
           
               
                   
                 UIUC 
               
               
                   
                 Repetition 
               
             
          
           
               
                   
                 CQI Report flag 
                 1 
                 1: CQI Report through UL subburst 
               
             
          
           
               
                 if(CQI Report flag==1){ 
               
             
          
           
               
                 period 
                 Reporting period 
               
               
                 Frame offset 
               
               
                 } 
               
             
          
           
               
                   
                 ACKdisable 
                 1 
               
             
          
           
               
                   
                 if (ACKdisable==0){ 
               
             
          
           
               
                 ..DL ACK bitmap index 
               
               
                 } 
               
             
          
           
               
                   
                 } 
               
               
                   
                   
               
             
          
         
       
     
     In the example of  FIG. 4 , since resources are allocated for a UL subframe using the circuit-mode resource allocation scheme, a UL Persistent Allocation IE is generated. However, if resources are allocated for a DownLink (DL) subframe using the circuit-mode resource allocation scheme, a DL Persistent Allocation IE rather than the UL Persistent Allocation IE is generated. 
     Meanwhile, each MS, when circuit-mode resources allocated to the MS itself are located in front of the de-allocated slots, detects the number of de-allocated slots, and shifts the location of slots included in the circuit-mode resource allocated to the MS itself. A description thereof will be given with reference to  FIG. 5 . 
       FIG. 5  is a diagram illustrating a method in which MSs, which have received a UL Persistent Allocation_IE, re-set a location of slots included in circuit-mode resources according to the UL Persistent Allocation_IE, according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , since the UL Persistent Allocation_IE of  FIG. 4  indicates de-allocation of the circuit-mode resource # 2 , the circuit-mode resource # 1  located in slots having a slot numbers that are less than slots associated with the de-allocated circuit-mode resource # 2  should be shifted by the number  2  of slots included in the de-allocated circuit-mode resource # 2 . That is, since a start offset of the non-de-allocated circuit-mode resource # 1  is less than a start offset of the de-allocated circuit-mode resource # 2 , the circuit-mode resource # 1  is shifted by the number  2  of slots included in the de-allocated circuit-mode resource # 2 . Therefore, an MS, which is allocated the circuit-mode resource # 1 , shifts the location of the slots included in the circuit-mode resource # 1  so that the circuit-mode resource # 1  includes 2 slots in the forward direction from slot # 8  rather than slot # 10 . In this way, since the location of the circuit-mode resource # 1  is changed, its start offset is also changed from slot # 10  to slot # 8 . It will be assumed herein that the location change by the UL Persistent Allocation_IE is performed after a defined number of frames have elapsed from the frame where the UL Persistent Allocation_IE was transmitted. 
     Meanwhile, as described in  FIG. 5 , it will be assumed that after the de-allocated circuit-mode resources are used, a circuit-mode resource # 4 , or a new circuit-mode resource, may be allocated. The number of slots included in the circuit-mode resource # 4  is assumed to be 4. In this case, since the circuit-mode resource # 4  is a new circuit-mode resource that is different from the previously allocated circuit-mode resources, the BS can notify of the start offset and the slot length to the MS using a resource allocation message. A description thereof will be given with reference to  FIG. 6 . 
       FIG. 6  is a diagram illustrating a method in which MSs, which have received a UL Persistent Allocation_IE, re-set a location of slots included in circuit-mode resources according to the UL Persistent Allocation_IE, and then allocate new circuit-mode resources, according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 6 , a BS can allocate the new circuit-mode resource # 4  by setting a start offset to a slot # 12  and transmitting a length  4  of the circuit-mode resource # 4  along with information on the set start offset. 
     With reference to  FIGS. 4 to 6 , the resource allocation method based on the circuit-mode resource allocation scheme has been described on the assumption that the IEEE 802.16 communication system first allocates packet-mode resources using the packet-mode resource allocation scheme, and then allocates circuit-mode resources using the circuit-mode resource allocation scheme. However, the same is possible even for the case where the IEEE 802.16 communication system first allocates circuit-mode resources using the circuit-mode resource allocation scheme, and then allocates packet-mode resources using the packet-mode resource allocation scheme. A description thereof will be given below with reference to  FIGS. 7 and 8 . 
       FIG. 7  is a diagram schematically illustrating an example of a resource allocation method based on a circuit-mode resource allocation scheme in an IEEE 802.16 communication system according to an embodiment of the present invention. 
     Shown in  FIG. 7 , unlike that in  FIG. 4 , is a method for first allocating circuit-mode resources using the circuit-mode resource allocation scheme, and then allocating packet-mode resources using the packet-mode resource allocation scheme in the IEEE 802.16 communication system. In this case, the forward direction for allocation of the circuit-mode resources is the opposite direction compared with the case where the packet-mode resource allocation is first performed, and when the circuit-mode resource allocation is first performed, the resources are allocated considering a Modulation and Coding Scheme (MCS) level. That is, an MS that uses the circuit-mode resource # 3  among the circuit-mode resources shown in  FIG. 7  has the lowest MCS level, and an MS that uses the circuit-mode resource # 1  has the highest MCS level. 
       FIG. 8  is a diagram illustrating a case where a circuit-mode resource is de-allocated, according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 8 , it will be assumed that the circuit-mode resource # 2  among the 3 circuit-mode resources allocated in  FIG. 7  is de-allocated. That is, since the circuit-mode resource # 3  and the circuit-mode resource # 1  are allocated and the circuit-mode resource # 2  is de-allocated, the BS generates a UL Persistent Allocation_IE. As illustrated in  FIG. 8 , the forward direction for allocation of the circuit-mode resources is the opposite direction compared with the case where the packet-mode resource allocation is first performed. 
     Since  FIG. 8  shows de-allocation of the circuit-mode resource # 2 , the circuit-mode resource # 1  having slot numbers greater than the slot numbers associated with the de-allocated circuit-mode resource # 2  should be shifted by the number  2  of slots included in the de-allocated circuit-mode resource # 2 . Therefore, an MS, which is allocated the circuit-mode resource # 1 , shifts the location of slots included in the circuit-mode resource # 1  so that the circuit-mode resource # 1  includes 6 slots in the forward direction from the slot # 8  rather than the slot # 10 . It will be assumed herein that the location change by the UL Persistent Allocation_IE is performed after a defined number of frames have elapsed from the frame where the UL Persistent Allocation_IE was transmitted. In  FIG. 8 , when the circuit-mode resources allocated to a corresponding MS that correspond to slot numbers that are lower than the slot numbers associated with the de-allocated circuit-mode resource, the corresponding MS uses the intact circuit-mode resource allocated to the MS. 
     Although the method for preventing the creation of unused resources due to the resource de-allocation has been described for the UL, by way of example, the same can be applied even to the DL. For example, when using Hybrid Automatic Repeat Request (HARQ) in the DL, the BS allocates an HARQ region, and performs one-dimensional resource allocation in the HARQ region, similar to the resource allocation for the UL. That is, the BS allocates resources in the HARQ region in ascending order of their frequency indexes, and when the HARQ region reaches the boundary with another region, the BS increases the time, and allocates the resources beginning at the frequency resource having the minimum frequency index at the increased time resource region. When one-dimensional resource allocation is performed as described above, the foregoing resource allocation method can be applied in the same way. 
     With reference to  FIG. 9 , a description will now be made of a method in which an MS, which has already been allocated circuit-mode resources, changes a location of the circuit-mode resources, in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
       FIG. 9  is a flowchart illustrating a process in which an MS, which has already been allocated circuit-mode resources, changes a location of circuit-mode resources, in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 9 , in step  911 , an MS, which has been allocated circuit-mode resources, receives a UL Persistent Allocation_IE. If Release Resource Move indicator included in the received Persistent Allocation_IE is enabled, the MS determines in step  913  if there is any de-allocated circuit-mode resource depending on a UL Persistent Allocation subburst IE included in the UL Persistent Allocation_IE. If it is determined that there are any de-allocated circuit-mode resources, the MS proceeds to step  915  where the MS changes the location of the circuit-mode resources allocated to the MS taking the location of the de-allocated circuit-mode resources into consideration. 
     With reference to  FIG. 10 , a description will now be made of an internal structure of a BS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
       FIG. 10  is a diagram illustrating an internal structure of a BS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 10 , a BS apparatus  1000  includes a controller  1010  and a transmitter  1020 . The controller  1010  allocates resources using the circuit-mode resource allocation scheme to prevent an creation of a hole, and generates resource allocation information for the allocated resources. A resource allocation operation of the controller  1010  has been described with reference to  FIGS. 4 ,  6 ,  7  and  8 . 
     The resource allocation information generated by the controller  1010  is provided to the transmitter  1020 , and the transmitter  1020  transmits the generated resource allocation information to MSs. The term ‘resource allocation information’ as used herein refers to, for example, a UL circuit-mode resource allocation message, and the resource allocation information has been described with reference to Table 1 and Table 2. 
     With reference to  FIG. 11 , a description will now be made of an internal structure of an MS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
       FIG. 11  is a diagram illustrating an internal structure of an MS apparatus in an IEEE 802.16 communication system according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 11 , an MS apparatus  1100  includes a controller  1110  and a receiver  1120 . The controller  1110  is allocated resources from a BS using the circuit-mode resource allocation scheme to prevent an creation of a hole. An operation in which the controller  1110  is allocated resources from the BS has been described with reference to  FIGS. 5 and 9 . 
     The receiver  1120  receives resource allocation information from the BS. The term ‘resource allocation information’ as used herein refers to, for example, a UL circuit-mode resource allocation message, and the resource allocation information has been described with reference to Table 1 and Table 2. 
     As is apparent from the foregoing description, according to exemplary embodiments of the present invention, the communication system can allocate resources using the circuit-mode resource allocation scheme to prevent creation of a hole, thereby contributing to an increase in the resource efficiency. 
     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.