Abstract:
A method and a device for managing resources of a base station in a wireless communication system is provided. The method comprises: calculating an average resource use of serving resources, which are used as downlinks from a serving base station to a plurality of communication terminals; selecting one of the communication terminals, which has a maximum interference from a neighbor base station, if the calculated average resource use exceeds a preset threshold; and making a reservation for at least one of neighbor resources used as downlinks from the neighbor base station, the at least one neighbor resource corresponding to the serving resource for the selected communication terminal, so that the neighbor base station may decrease transmission power in the at least one neighbor resource.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an operation method and apparatus of a base station in a wireless communication system and, in particular, to a resource management method and apparatus of the base station. 
     2. Description of the Related Art 
     Typically, a wireless communication system provides communication services with various service qualities at high data rate. An Orthogonal Frequency Division Multiplexing (OFDM) based wireless communication system is such a wireless communication system. OFDM is a multicarrier method for transmitting data on multiple subcarriers arranged at even intervals to guarantee orthogonality and advantageous in frequency utilization efficiency and robustness to multi-path fading. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     However, such a wireless communication system has a problem of Inter Cell Interference (ICI) caused when the adjacent base stations transmit signals on the same subcarrier. That is, the signals transmitted on the same subcarrier cause interferences to the adjacent base stations. The inter-cell interference degrades the channel utilization efficiency in the wireless communication system. As a consequence, the throughput of the wireless communication system is degraded. 
     The present invention aims to improve the throughput of the wireless communication system. In order to accomplish this, the present invention provides an Inter Cell Interference Coordination (ICIC) method for use in the wireless communication system. 
     Solution to Problem 
     In accordance with an aspect of the present invention, a resource management method of a base station in a wireless communication system includes calculating, at a serving base station, average resource use amount of serving resources for use in downlink in corresponding to multiple terminals, selecting, when the average resource use amount is greater than a predetermined threshold, one of terminals, the selected terminal undergoing highest interference from a neighbor base station, and reserving at least one of neighbor resources of the neighbor base station for use in downlink for reducing transmission power of selected neighbor resource, the selected neighbor resource corresponding to the serving resource for the selected terminal. 
     Preferably, the resource management method further includes recovering, when reservation of at least one of the neighbor resources fails, the reserved serving resource by increasing reduced transmission power in correspondence to the serving resource reserved for the neighbor base station. 
     In accordance with another aspect of the present invention, a resource management apparatus of a base station in a wireless communication system includes a resource use amount calculator which calculates average resource use amount of serving resources for use in downlink in corresponding to multiple terminals and a resource reservation processing unit which selects, when the average resource use amount is greater than a predetermined threshold, one of terminals, the selected terminal undergoing highest interference from a neighbor base station and reserves at least one of neighbor resources of the neighbor base station for use in downlink for reducing transmission power of selected neighbor resource, the selected neighbor resource corresponding to the serving resource for the selected terminal. 
     Preferably, the resource management apparatus further includes a resource recovery processing unit which recovers, when reservation of at least one of the neighbor resources fails, the reserved serving resource by increasing reduced transmission power in correspondence to the serving resource reserved for the neighbor base station. 
     Advantageous Effects 
     The resource management method and apparatus of the eNB in a wireless communication system according to the present invention is capable of suppressing interference from neighbor eNBs on the serving resource for one of UEs connected to the eNB by reserving one of the resources of the neighbor eNB for which transmission power is reduced. Also, the resource management method and apparatus of the eNB in a wireless communication system according to the present invention is capable of suppressing interference caused by an eNB on the neighbor resource for one of the UEs connected to the neighbor eNB by reducing the transmission power on one of the serving resources reserved for the neighbor eNB. Also, the resource management method and apparatus of the eNB in a wireless communication system according to the present invention is capable of releasing, when it fails to reserve neighbor resource at a neighbor eNB, reservation of the serving resource corresponding to the neighbor eNB to increase the transmission power on the corresponding serving resource and thus secure the serving resource for use. 
     In this way, the eNB is capable of managing the serving resources efficiently. Additionally, it is possible to manage the resource efficiently in the wireless communication system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention, 
         FIG. 2  is a block diagram illustrating the configuration of the eNB according to an embodiment of the present invention, 
         FIG. 3  is a flowchart illustrating the resource management procedure of the eNB according to an embodiment of the present invention, 
         FIG. 4  is a flowchart illustrating the resource reservation mode execution procedure of  FIG. 3 , 
         FIG. 5  is a flowchart illustrating the resource recovery mode execution procedure of  FIG. 3 , and 
         FIG. 6  is a flowchart illustrating the resource reservation support procedure of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the present invention are described with reference to the accompanying drawings in detail. The same reference numbers are used throughout the drawings to refer to the same or like parts. Detailed description of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. 
       FIG. 1  is a schematic diagram illustrating a wireless communication system according to an embodiment of the present invention. Although the embodiment is directed to a Long Term Evolution (LTE) system as the wireless communication system, the present invention is not limited thereto. 
     Referring to  FIG. 1 , the wireless communication system according to this embodiment includes a User Equipment (UE)  110 , an evolved Node B (eNB)  120 , and a Core Network node  130 . 
     The UE  110  uses a communication service through wireless communication. Here, the communication service may be a voice services or a data service. Also, the UE  110  may be fixed or mobile. 
     The eNB  120  manages a cell and supports wireless communication of the UE  110  within the cell. Here, the cell may be the cell of a normal cellular system. The terms ‘eNB’ and ‘cell’ can be used interchangeably in the same meaning. The eNB  120  establishes a radio channel with the UE  110  and controls radio resource. For example, the eNB  120  is capable of generating system information to broadcast intra cell information and allocating radio resources for communicating packet data or control information with the UE  110 . Here, the system information may include operator information (PLMN ID; PLMN Indicator) of the wireless network Public Land Mobile Network (PLMN) accessible via the eNB  120 , eNB Cell Global ID (ECGI), and Tracking Area ID (TAI) of each cell. For this purpose, the eNB  120  is provided with a control protocol such as Radio Resource Control (RRC) protocol related to radio resource management. 
     At this time, the eNB  120  provides the multiple UEs  110  with communication service through multiple component carriers. That is, the eNB  120  provides the communication service with at least one of the component carriers. For example, if among at least three component carriers the first and third component carriers are assigned to the eNB  120 , the eNB provides the communication service using the first and third component carriers. Here, each component carrier includes at least one transmission resource. The transmission resource can be a Physical Resource Block (PRB). That is, the eNB  120  is capable of allocating at least one transmission resource to the UE  110  for use in communication service. The eNB  120  also control the transmission (Tx) power on the transmission resource. Here, the eNB  120  controls the Tx power in a Distributed Power Control scheme according to an embodiment of the present invention. 
     For a specific UE  110 , the eNB  120  can be a serving eNB  121  or a neighbor eNB  123 . The serving eNB  121  manages the serving cell in which the UE  110  connects to the eNB  121  substantially. The serving eNB  121  provides the communication service to the UE  110  within the serving cell. The neighbor eNB  123  manages a neighbor cell and is adjacent to the serving eNB  121 . Here, the serving eNB  121  and the neighbor eNB  123  are connected to each other through X2 interface. The eNB  120  is capable of receiving Channel State Information (CSI) of the serving and neighbor cells. With the CSI, the eNB  120  manages the transmission resources. That is, the eNB  120  is capable of reserving a transmission resource for the UE  110  in order to prevent the neighbor eNB  123  from using the reserved transmission resource. In addition, the eNB  120  is capable of making a handover decision for the UE  110  and commanding handover. 
     The core network node  130  manages the UE  110  and the eNB  120  and supports radio communication between the UE  110  and the eNB  120 . Here, the core network node  130  connects to the eNB  120  through S1 interface. At this time, the core network node  130  includes at least one of Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network Gateway (P-GW), and Home Subscriber Server (HSS). 
     The MME manages the UE  110  in idle mode and selects S-GW and P-GW for the UE  110 . The MME is responsible for the function related to the roaming and authentication of the UE  110 . The MME also processes the bearer signal generated by the UE  110 . For this purpose, the MME allocates identity information to the UE  110  and controls the connection of the UE  110  and manages the UE  110  based on the identity information. At this time, the MME communicates with the UE  110  using Non Access Stratum (NAS) messages. 
     The MME connects to the UE  110  via the eNB  120 . The MME also supports plural tracking areas and connects to plural eNBs  120  supporting respective tracking area informations. That is, the plural eNBs  120  supporting the same tracking area information can be connected to the same MME. The eNBs  120  supporting different tracking area informations can connect to the respective MMEs. Also, the eNB  120  supporting different tracking area informations may connect to the same MME  130 . 
     The S-GW connects to the eNB  120  and MME. The S-GW is responsible for controlling mobility of the UE  110 . That is, the S-GW works as a mobility anchor for the movement of the UE  110 . 
     The P-GW connects to the S-GW. The P-GW also connects to an Internet Protocol (IP) network. The P-GW is responsible for allocating IP address to the UE  110  and processing packet data. That is, the P-GW delivers the packet data from the IP network to the UE  110  and from the UE  110  to the IP network. The P-GW determines the bearer bandwidth for the UE  110  and performs packet data forwarding and routing function. In addition, the P-GW is capable of working as a mobility anchor for the movement of the UE  110 . 
     The HSS stores the subscription information of the UE  110 . The HSS is capable of providing the MME with the subscription information of the UE  110  for use in control of the UE  110 . 
     Assuming the above-structured wireless communication system, a description is made of the configuration and operations of the eNB  120  according to an embodiment of the present invention in detail hereinafter. In the wireless communication system, the eNB operates as the serving eNB  121  of the UE  110  for the corresponding cell and as a neighbor eNB  123  for the neighbor cell. In the following, the description is directed to the configuration and operations of the serving eNB  121  of the UE  110 , and this is applied to the eNB  120  of the wireless communication systems identically. In addition, the transmission resource used by the serving eNB  121  is referred to as serving resource, and the transmission resource used by the neighbor eNB  123  is referred to as neighbor resource. Here, the serving resource and the neighbor resource can be the same or different transmission resource(s). 
       FIG. 2  is a block diagram illustrating the configuration of the eNB according to an embodiment of the present invention. In this embodiment, the eNB includes macro eNB, pico eNB, and femto eNB. 
     Referring to  FIG. 2 , the eNB  120  according to this embodiment includes a Radio Frequency (RF) unit  210 , a core interface unit  220 , a memory unit  230 , and a control unit  240 . 
     The RF unit  210  is responsible for radio communication function of the eNB  120 . The RF unit  210  is capable of including a radio interface for communicating signals with the UE  110  and X2 interface for communicating signals with another eNB  120 . 
     The core interface unit  220  is responsible for communication of the eNB  120  with the core network node  130 . The core network interface  220  is capable of including a S1 interface for communicating signals with the core network node  130 . Here, the core network interface unit  220  is capable of communicating signals with the core network node  130  through wired link. 
     The memory  230  is provided with program and data memories. The program memory stores programs for controlling general operations of the eNB  120 . At this time, the program memory stores the programs for managing the transmission resource according to an embodiment of the present invention. The data memory stores the data generated by the execution of the programs. 
     The control unit  240  is responsible for controlling overall operations of the eNB  120 . The control unit  240  manages transmission resource according to an embodiment of the present invention. The control unit  240  is capable of reserving a neighbor resource at the neighbor eNB  123 . That is, the control unit  240  is capable of requesting the neighbor eNB  123  to reduce transmission power on at least one of the neighbor resources. The control unit  240  is also capable of configuring transmission power per serving resource and adjusting transmission power depending on the serving resource. That is, the control unit  240  is capable of supporting reservation of the neighbor eNB  123  for at least one of serving resources and reducing the transmission power of the corresponding serving resource to a predetermined level. The control unit  240  is also capable of releasing the reservation of the serving resource and increasing the transmission power for the corresponding transmission resource to a predetermined level. The control unit  240  includes a resource information exchanging unit  241 , a resource reservation processing unit  243 , a resource recovery processing unit  245 , and a resource reservation supporting unit  247 . 
     The resource information exchanging unit  241  exchanges the resource information, which includes the resource indices and predetermined transmission power levels corresponding to the transmission resources, with the neighbor eNB  123 . The resource information exchanging unit  241  is capable of exchanging the resource information with the neighbor eNB  123  at a predetermined period. The resource information exchanging unit  241  also controls storing the resource information. The resource information exchanging unit  241  is provided with a resource use amount calculator. The resource use amount calculator calculates average resource use amount of the eNB  120  for the UEs  110 . The resource use amount calculator determines whether the average resource use amount is greater than a predetermined threshold. 
     The resource reservation processing unit  243  reserves the neighbor resource of the neighbor eNB  123 . At this time, if the average resource use amount is greater than the threshold, the resource reservation processing unit  243  selects one of the UEs  110  connected to the eNB  120  which experiences highest interference from the neighbor  123 . The resource reservation processing unit  243  reserves the neighbor resource of the neighbor eNB  123  for the corresponding UE  110 . At this time, the resource reservation processing unit  243  reserves the neighbor resource having the same index with the reserving resource allocated for the corresponding UE  110 . That is, the resource reservation processing unit  243  is capable of requesting the neighbor eNB  123  to reduce the transmission power for the corresponding neighbor resource. 
     The resource recovery processing unit  245  recovers the serving resource for the neighbor eNB  123 . At this time, if it fails to reserve the neighbor resource at the neighbor eNB  123 , the resource recovery processing unit  245  determines whether the serving resource is reserved for the neighbor eNB  123 . If the serving resource is reserved, the resource recovery processing unit  245  releases the reservation on the corresponding serving resource and increases the transmission power for the corresponding serving resource to a predetermined level. 
     The resource reservation supporting unit  247  reserves the serving resource for the neighbor eNB  123 . That is, if the neighbor eNB  123  requests for the reservation on the serving resource, the resource reservation supporting unit  247  reduces the transmission power for the corresponding serving resource to a predetermined level. In addition, the resource reservation supporting unit  247  is capable of controlling to allocate other serving resource to the UE  110  in correspondence to the corresponding serving resource. 
       FIG. 3  is a flowchart illustrating the resource management procedure of the eNB according to an embodiment of the present invention. 
     Referring to  FIG. 3 , the resource management procedure of the eNB  120  according to this embodiment starts at the state where the control unit  240  retains the resource information at step  311 . At this time, the resource information includes serving resource information on the serving resource of the corresponding eNB  120 , neighbor resource information on the neighbor resource of the neighbor eNB  123 , and reserved resource information indicating the reservation state of the serving resource of the corresponding eNB  120  corresponding to the neighbor resource. Here, the serving resource information is configured as shown in table 1, the neighbor resource information is configured as shown in table 2, and the reserved resource information is configured as shown in table 3. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Serving resource 
                 Serving resource Tx 
                 Serving resource 
               
               
                 index 
                 power 
                 Reservation state 
               
               
                   
               
             
             
               
                 XXXX.0 
                 level 3 
                 0(free) 
               
               
                 XXXX.1 
                 level 1 
                 1(reserved) 
               
               
                 XXXX.2 
                 level 2 
                 0(free) 
               
               
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                 Average 
                   
               
               
                   
                 Average 
                   
                 Neighbor 
                 processing 
                   
               
               
                   
                 resource 
                 Neighbor 
                 resource 
                 amount of 
                   
               
               
                 Neighbor 
                 use 
                 resource Index 
                 reservation 
                 Neighbor 
                 M 
               
               
                 eNB ID 
                 amount 
                 and Tx power 
                 state 
                 resource 
                 value 
               
               
                   
               
             
             
               
                 AAAAA 
                 70% 
                 {XXXX.0, level 
                 0(free) 
                 aa Mbps 
                 0.8 
               
               
                   
                   
                 3} 
                   
                   
                   
               
               
                   
                   
                 {XXXX.1, level 
                 0(free) 
                   
                   
               
               
                   
                   
                 3} 
                   
                   
                   
               
               
                 BBBBB 
                 40% 
                 {XXXX.0, level 
                 0(free) 
                 bb Mbps 
                 0.7 
               
               
                   
                   
                 2} 
                   
                   
                   
               
               
                   
                   
                 {XXXX.1, level 
                 0(free) 
                   
                   
               
               
                   
                   
                 3} 
                   
                   
                   
               
               
                   
                   
                 {XXXX.2, level 
                 1(reserved) 
                   
                   
               
               
                   
                   
                 0} 
                   
                   
                   
               
               
                 CCCCC 
                 80% 
                 {XXXX.3, level 
                 1(reserved) 
                 cc Mbps 
                 0.6 
               
               
                   
                   
                 0} 
                   
                   
                   
               
               
                   
                   
                 {XXXX.4, level 
                 0(free) 
                   
                   
               
               
                   
                   
                 3} 
                   
                   
                   
               
               
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Neighbor eNB ID 
                 Serving resource Index 
               
               
                   
               
             
             
               
                   
                 AAAAA 
                 XXXX.1 
               
               
                   
                 — 
                 — 
               
               
                   
               
             
          
         
       
     
     That is, the serving resource information includes at least one of downlink resource use amount at the eNB  120 , i.e. number of serving resources, average resource amount for the UEs connected to the eNB  120 , index and transmission power per serving resource, and reservation state per serving resource. The neighbor resource information includes cell identity information per neighbor eNB  123 , average resource amount corresponding to the downlink neighbor resource per neighbor eNB  123 , number of UEs  110  connected to each neighbor eNB  123 , index and transmission power per neighbor resource, reservation state per neighbor resource, average processing amount of neighbor resource at UEs  110 , and M value per UE  110 . Here, the M value denotes the maximum Modulation and coding level as compared to average Modulation and Coding Scheme (MSC). 
     At this time, the control unit  240  is capable of exchanging the resource information with the neighbor eNB  123  at a predetermined period to share the resource information. That is, the control unit  240  is capable of transmitting to the neighbor eNB  123  at least one of the serving resource information and reserved resource information when a predetermined period arrives. The control unit  240  is also capable of controlling to store the neighbor resource information in the memory  230  when the neighbor resource information is received from the neighbor eNB  123 . The control unit  240  is also capable of updating the resource information in the memory unit  230  when the resource reservation mode or resource recovery mode execution or the resource reservation is supported. 
     If a predetermined calculation period arrives, the control unit  240  detects this at step  313  and calculates the average resource use amount at step  315 . That is, the control unit  240  calculates the average resource use amount of the UEs  100  according to the number of UEs  110  connected to the corresponding eNB  120  and the number of serving resources. Next, the control unit  240  compares the average resource use amount with a predetermined threshold at step  317 . At this time, the control unit  240  determines whether the average resource amount is greater than the threshold. 
     If it is determined that the average resource amount is greater than the threshold at step  317 , the control unit  240  executes resource reservation mode at step  319 . At this time, the control unit  240  reserves the neighbor resource of the neighbor eNB  123 . That is, the control unit  240  is capable of requesting the neighbor eNB  123  to reduce the transmission power on the corresponding neighbor resource. In this way, the control unit  240  is capable of mitigating interference from the neighbor eNB  123  on the serving resource for one of the UEs  110 . The resource reservation mode execution procedure of the eNB is described in detail hereinafter. 
       FIG. 4  is a flowchart illustrating the resource reservation mode execution procedure of  FIG. 3 . 
     Referring to  FIG. 4 , the resource reservation mode execution procedure of the eNB according to this embodiment starts with selecting one of the multiple UEs connected to the eNB  120  at step  411 . At this time, the control unit  240  selects one of the UEs  110  connected to the eNB  120  which experiences highest interference from the neighbor  123 . For example, the control unit  240  is capable of selecting the UE  110  fulfilling the condition of equation (1). That is, the control unit  240  is capable of selecting the UE having the least M value among the UEs  110 . 
     
       
         
           
             
               
                 
                   
                     k 
                     = 
                     
                       
                         arg 
                         k 
                       
                       ⁢ 
                       min 
                       ⁢ 
                       
                         { 
                         
                           M 
                           k 
                         
                         } 
                       
                     
                   
                   , 
                   
                     
 
                   
                   ⁢ 
                   
                     
                       M 
                       k 
                     
                     = 
                     
                       
                         X 
                         k 
                       
                       
                         X 
                         k 
                         ′ 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     Here, k denotes ID of the UE  110 , X k  denotes the substantial average modulation and coding level of the UE, and X′ k  denotes the maximum modulation and coding level available without interference from the neighbor eNB  123 . 
     Next, the control unit  240  checks the neighbor eNB  123  through the UE  110  at step  413 . At this time, the control unit  240  analyzes the channel state information of the UE  110  to check the neighbor eNB  123 . Here, the control unit  240  is capable of acquiring Reference Signal Received Power (RSRP) per neighbor eNB  123  at the UE  110 . 
     Next, the control unit  240  determines the interference combination to the neighbor eNB  123  at step  415 . That is, the control unit  240  is capable of comparing the RSRP per eNB  123  with predetermined RSRP threshold. If the RSRP of the neighbor eNB  123  is greater than the RSRP threshold, the control unit  240  extracts the corresponding neighbor eNB  123  as an element of an interference set. At this time, each element can be RSRP corresponding to each neighbor eNB  123 . The control unit  240  is capable of determining a subset of the interference set as the interference combination. At this time, the control unit  240  is capable of determining a power set of the interference set as the interference combination. For example, if the interference set S is {S 1 , S 2 }, the control unit  240  is capable of determining {S 1 }, {S 2 }, or {S 1 , S 2 } as the interference combination. 
     Next, the control unit  240  predicts the effective throughput per serving resource at the UE  110  that is capable of being acquired through reservation of the neighbor resource in correspondence to the interference combination at step  417 . At this time, the control unit  240  predicts Signal to Noise Ratio (SNR) of the UE  110  that can be acquired through reservation of neighbor resource in correspondence to the respective interference combination. That is, the control unit  240  predicts the sum of the RSRPs per neighbor eNB  123  as interference and calculates the SNR based on interference to the RSRP corresponding to the eNB  120 . For example, the control unit  240  is capable of calculating the SNR of the UE  110  corresponding to each interference combination as equation (2). 
                     S   ⁢           ⁢   N   ⁢           ⁢     R   X       =       R   ⁢           ⁢   S   ⁢           ⁢   R   ⁢           ⁢     P   serving           ∑     k   ∈     A   ⁢           ⁢   and   ⁢           ⁢   not   ⁢           ⁢   k     ∈   X       ⁢     R   ⁢           ⁢   S   ⁢           ⁢   R   ⁢           ⁢     P   k                   Equation   ⁢           ⁢     (   2   )                 
Here, X denotes the identity data of the interference combination, RSRP serving  denotes RSRP from the eNB  120 , and RSRP k  denotes RSRP from the neighbor eNB  123 .
 
     The control unit  240  determines the processing amount per serving resource according to the MCS level corresponding to the SNR of the UE in correspondence to each interference combination. That is, the control unit  240  predicts the bit error rate in the case of determining the transmission power according to the SNR of the UE  110  and calculates the processing amount of the serving resource according to the MCS level of the UE. Afterward, the control unit  240  predicts the processing amount per serving resource corresponding to each interference combination using the processing amount of the serving resource according to the MCS level of the UE  110 . For example, the control unit  240  is capable of calculating the processing amount per serving resource at the UE  110  in correspondence to each interference combination as equation (3). Furthermore, in the case that multiple interference combinations exist, the control unit  240  is capable of arrange the interference combinations in a descending order of processing amount per serving resource corresponding to each interference combination. 
     
       
         
           
             
               
                 
                   
                     Average 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Processing 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Amount 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     of 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Serving 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Resource 
                   
                   = 
                   
                     
                       
                           
                       
                       ⁢ 
                       
                         
                           Processing 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           Amount 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           of 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           Serving 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           Resource 
                         
                         ⁢ 
                         
                            
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           according 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           to 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           MCS 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           Level 
                         
                       
                       ⁢ 
                       
                           
                       
                     
                     
                       
                          
                         X 
                          
                       
                       + 
                       1 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     Here, |X| denotes a number of neighbor eNBs  123  in the interference combination. 
     For example, if one of the interference combinations includes one neighbor eNB  123  and the processing amount of the serving resource corresponding thereto is 8 Mbps, the control unit  240  is capable of predicting the processing amount per serving resource of 4 Mbps. If one of the interference combinations includes two neighbor eNBs  123  and the processing amount of the serving resource corresponding thereto is 9 Mbps, the control unit  240  is capable of predicting the processing amount per serving resource of 3 Mbps. 
     Next, the control unit  240  determines whether neighbor resource reservation per interference combination is possible at step  419 . That is, the control unit  240  determines whether there is neighbor resource available for reservation at the neighbor eNB  123  within the interference combination. At this time, the control unit  240  determines whether there is the neighbor resource corresponding to the transmission resource with the same index as the serving resource for the UE  110 . That is, the control unit  240  determines whether the neighbor resource not reserved at the neighbor eNB  123  of the interference combination based on the neighbor resource information of table 2. If it is determined that there is the neighbor resource available for reservation at the eNB  123  of the interference combination, the control unit  240  determines that the neighbor resource reservation is available at the neighbor eNB  123  in the interference combination. Otherwise, if it is determined that there is no neighbor resource available for reservation at the neighbor eNB  123  of the interference combination, the control unit  240  determines that the neighbor resource reservation is not available at the neighbor eNB  123  in the interference combination. The control unit  240  is also capable of selecting one of interference combinations according to the arrangement order of the interference combinations to determine whether the resource reservation is available. If it is determined that the resource reservation is not available, the control unit  240  selects another one according to the arrangement order of the interference combinations to determine the resource reservation is available. 
     If it is determined that the resource reservation per interference combination is not available at step  419 , the control unit  240  returns the procedure to  FIG. 3 . Otherwise, if it is determined that the resource reservation per interference combination is available at step  419 , the control unit  240  requests the neighbor eNB  123  in the interference combination for reservation of neighbor resource at step  421 . At this time, the control unit  240  selects at least one of the neighbor resources of the neighbor eNB  123  and requests the neighbor eNBs  123  to reserve the corresponding neighbor resource. That is, the control unit  240  requests for the reservation of the neighbor resource corresponding to the transmission resource with the same index as the serving resource. In order to accomplish this, the control unit  240  is capable of transmitting a resource reservation request message to the neighbor eNB  123 . At this time, the resource reservation request message is capable of including a request bitmap indicating the reservation state per neighbor resource. Here, the control unit  240  is capable of generating the request bitmap correspond to the neighbor eNB  123  according to the neighbor resource information of table 2 and transmitting the request bitmap having target neighbor resource bit is set to 1. 
     If a response is received from the neighbor eNB  123  in reply to the neighbor resource reservation request, the control unit  240  detects this at step  423  and determines whether the neighbor eNB  123  accepts the reservation of the neighbor resource at step  425 . That is, when a resource reservation response message is received from the neighbor eNB  123 , the control unit  240  analyzes the resource reservation response message to determine whether the neighbor resource reservation is accepted. At this time, the resource reservation response message is capable of including a response bitmap indicating the reservation state per neighbor resource of the neighbor eNB  123 . The control unit  240  is capable of checking whether the target resource bit is set to 1 or 0 in the response bitmap. If the target resource bit is set to 1 in the response bitmap, the control unit  240  determines that the neighbor resource reservation is accepted by the neighbor eNB  123 . Otherwise, if the target resource bit is set to 0 in the response bitmap, the control unit  240  determines that the neighbor resource reservation is rejected by the neighbor eNB  123 . 
     If it is determined that the neighbor eNB  123  rejects the neighbor resource reservation at step  425 , the control unit  204  returns the procedure to  FIG. 3 . Otherwise, if it is determined that the neighbor eNB  123  accepts the neighbor resource reservation, the control unit  240  checks the reservation of the neighbor resource at the neighbor eNB  123  at step  427  and returns the procedure to  FIG. 3 . At this time, the control unit  240  requests the neighbor eNB  123  to reduce the transmission power on the corresponding neighbor resource to a predetermined level. For this purpose, the control unit  240  is capable of transmitting a resource reservation confirmation message to the neighbor eNB  123 . The control unit  240  is also capable of updating the neighbor resource information of table 2. That is, the control unit  240  is capable of changing the reservation state of the corresponding neighbor resource in the neighbor resource information. 
     Finally, if the neighbor resource reservation is successful at the neighbor eNB  234  in the resource reservation mode at step  319 , the control unit  240  terminates the resource management procedure. That is, after checking the reservation of the neighbor resource at the neighbor eNB  123 , the control unit  240  ends the resource management procedure. 
     If it fails to reserve the neighbor resource of the neighbor eNB  123  in the resource reservation mode at step  319 , the control unit  240  detects this at step  321 , executes the resource recovery mode, and then terminates the resource management procedure. That is, if it is determined that the per-interference combination resource reservation is not available at step  419 , no response is received from the neighbor eNB  123  in response to the neighbor resource reservation request at step  423 , or the neighbor resource reservation is rejected by the neighbor eNB  123  at step  425 , the control unit  240  determines regards this as the neighbor resource reservation failure. At this time, the control unit  240  determines whether the serving resource corresponding to the neighbor resource of the neighbor eNB  123  is reserved. If the serving resource is reserved, the control unit  240  releases the reservation on the corresponding serving resource. That is, the control unit  240  is capable of increasing the transmission power on the corresponding serving resource to a predetermined level. In this way, the control unit  240  is capable of securing the serving resource for use in downlink. Hereinafter, a description is made of the resource recovery mode execution procedure of the eNB  120  in detail. 
       FIG. 5  is a flowchart illustrating the resource recovery mode execution procedure of  FIG. 3 . 
     Referring to  FIG. 5 , the resource recovery mode execution procedure of the eNB  120  according to this embodiment starts with determining a candidate eNB at step  511 . That is, the control unit  240  compares the average processing amount of neighbor resource at the neighbor eNB  123  with the processing amount per serving resource at the eNB  120 . At this time, the control unit  240  determines whether the average processing amount of the neighbor resource at the neighbor eNB  123  is greater than the processing amount per serving resource at the eNB  120 . If the average processing amount of the neighbor resource at the neighbor eNB  123  is greater than the processing amount per serving resource at the eNB  120 , the control unit  240  determines the corresponding neighbor eNB  123  as a candidate eNB. Next, the control unit  240  determines whether a candidate eNB exists at step  513 . 
     If it is determined that no candidate eNB exists at step  513 , the control unit  240  returns the procedure to  FIG. 3 . Otherwise, if it is determined that a candidate eNB exists at step  513 , the control unit  240  determines whether the corresponding serving resource is reserved in correspondence to the candidate eNB at step  515 . At this time, the control unit  240  determines whether there is any reserved serving resource corresponding to the candidate eNB based on at least one of serving resource information of table 1 and reservation resource information of table 3. If there are multiple candidate eNBs, the control unit  240  is capable of arranging the candidate eNBs in a descending order of M values corresponding to the respective candidate eNBs. The control unit  240  is capable of selecting one of the candidate eNBs in the arrangement order to determine whether the serving resource is reserved. If no serving resource is reserved, the control unit  240  selects another candidate eNB to determine whether the serving resource is reserved. 
     If it is determined that no serving resource is reserved in correspondence to the candidate eNB at step  515 , the control unit  240  returns the procedure to  FIG. 3 . Otherwise, if it is determined that the serving resource is reserved in correspondence to the candidate eNB, the control unit  240  increases the transmission power on the serving resource reserved in correspondence to the candidate eNB to a predetermined level at step  517  and returns the procedure to  FIG. 3 . That is, the control unit  240  is capable of updating the serving resource information of table 1 and the reserved resource information of table 3. That is, the control unit  240  is capable of changing the reservation state of the corresponding serving resource in the serving resource information and the reserved resource information. 
     Meanwhile, if the calculation period arrival is not detected at step  313 , the control unit  240  supports resource reservation at step  325  and terminates the resource management procedure. At this time, the control unit  240  reserves the serving resource in response to the neighbor eNB  123 . That is, if the neighbor eNB  123  requests for reservation of the serving resource, the control unit  240  is capable of reducing the transmission power on the serving resource to a predetermined level. In addition, the control unit  240  is capable of allocating other serving resource for the UE  110  in correspondence to the serving resource. In this way, the control unit  240  is capable of managing the serving resource efficiently. Hereinafter, a description is made of the resource reservation support procedure of the eNB  120  in detail. 
       FIG. 6  is a flowchart illustrating the resource reservation support procedure of  FIG. 3 . 
     Referring to  FIG. 6 , the resource reservation support procedure of eNB  120  starts with detecting the request for reserving the serving resource from the neighbor eNB  123  at step  611 . That is, when the resource reservation request message is received from the neighbor eNB  123 , the control unit  240  detects this. At this time, the resource reservation request message is capable of including a request bitmap indicating the reservation state per serving resource at the serving eNB  120 . In the request bitmap, the bit corresponding to the serving resource requested by the neighbor eNB  123  is bit is set to 1. 
     Next, the control unit  240  replies the serving resource reservation request of the neighbor eNB  123  at step  613 . That is, the control unit  240  notifies the neighbor eNB  123  whether the serving resource reservation is accepted. At this time, the control unit  240  sends the resource reservation response message to the neighbor eNB  123 . Here, the resource reservation response message is capable of including a response bitmap indicating the reservation states of the serving resources of the eNB  120 . That is, it is intended to accept the reservation of the serving resource for the neighbor eNB  123 , the control unit  240  is capable of setting the bit corresponding to the serving resource requested by the neighbor eNB  123  to 1 in the response map. If it is intended to reject the reservation of the serving resource for the neighbor eNB  123 , the control unit  240  is capable of setting the bit corresponding to the serving resource requested by the neighbor eNB to 0 in the response bitmap. 
     If it is determined that the reservation of the serving resource at the neighbor eNB  123 , the control unit  240  detects this at step  615  and provides the neighbor eNB  123  with the substantial reservation of the serving resource at step  617 . That is, the control unit  240  reduces the transmission power on the corresponding serving resource to a predetermined level and returns the procedure to  FIG. 3 . At this time, it is accepted to reserve the serving resource for the neighbor eNB  123 , the neighbor eNB  123  may check the reservation of the serving resource. When the resource reservation confirm message is received from the neighbor eNB  123 , the control unit  123  confirms the reservation of the serving cell correspondently. The control unit  240  is capable of updating the serving resource information of table 1 and the reservation resource information of table 3. That is, the control unit  240  is capable of changing the reservation state of the corresponding serving resource in the serving resource information and the reserved resource information. 
     According to the present invention, the eNB  120  reserves at least one of neighbor resources of the neighbor eNB  123  for reducing transmission power thereat so as to suppress the interference from the neighbor eNB  123  on the serving resource for one of the UEs  110  connected to the eNB  120 . The eNB  120  is also capable of suppressing the interference from the eNB  120  on the neighbor resource for one of the UEs connected to the neighbor eNB  120  by reducing the transmission power on at least one of the serving resources for the neighbor eNB  123 . Also, when the reservation of specific neighbor resource of the neighbor eNB  123  fails, the eNB  120  releases the reservation on the serving resource corresponding to that of the neighbor eNB  123  to increase the transmission power on the corresponding serving resource and thus secure the serving resource for use in downlink. 
     In this way, the eNB  120  is capable of managing the serving resource efficiently. In addition, it is possible to manage the resource efficiently in the wireless communication system. 
     INDUSTRIAL APPLICABILITY 
     The specification and drawings are to be regarded in an illustrative rather than a restrictive sense in order to help understand the present invention. It is obvious to those skilled in the art that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention.