Patent Abstract:
The present invention relates to a method for allocating a radio resource of a base station for controlling the power of a terminal in a mobile communication system including a plurality of femtocells in the service coverage of a macro base station, said method comprising: a radio resource-grouping step of dividing the radio resources shared by the macro base station and the femtocells into groups in accordance with a preset criterion; a radio resource-allocating step of randomly allocating each of the grouped radio resources to base stations such that the terminal uses maximum transmitting power in different resource areas for the plurality of base stations; and a transmitting step of transmitting the allocated radio resource information to the terminal. The method of the present invention effectively controls interferences between the terminal in communication with the macro base station and the terminal in communication with the femtocell.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a power control method and apparatus of a terminal in a wireless communication system including femto and macro base stations. In more detail, the present invention relates to a power control method and apparatus of a terminal for grouping the radio resource shared by femto and macro base station in predetermined segmentation unit and assigning priority to use maximum transmit power. 
     2. Description of the Related Art 
     Recently, the boundary between fixed and mobile services has increasingly become blurred due to the advance of communication technologies. For example, the fixed service providers are investing in the Internet Protocol telephony represented by Voice over Internet Protocol (VoIP) as part of broadband Internet access service based on the Wireless Local Area Network (WLAN) connection to compete against the wireless voice and data service provided by the wireless service providers, under the objective of fixed-mobile convergence (FMC). In contrast, the wireless service providers are driving Fixed Mobile Substitution (FMS) with the introduction of home network service such as homezone service to provide the user with fixed voice service in indoor environment. In such omnidirectional competition, a small cellular base station called “femto-cell” designed for use in a home or small business is introduced as an alternative way of the wireless service providers to deliver the benefits of the FMC. 
     Since the femto base station uses the same radio access technology as the cellular network having the nationwide service coverage, the user can enjoy the benefits of service coverage expansion (reduction of shadow area) without purchase of an additional handset, high speed data service, and cheap billing rate of public network use. 
     Meanwhile, the femto base station providing the service using the same technology and frequency band as the cellular network causes various problems. One of the representative examples is the interference with the macro base station and other femto base stations. 
     There is therefore a need to guarantee the service reception performance of the terminal in the area where the macro and femto base stations coexist. 
     SUMMARY OF THE INVENTION 
     Problem to be Solved 
     The present invention is conceived to solve this problem, and it is an object to provide a method for managing the resource in which the different types of base stations are interfering with each other, efficiently. 
     For this purpose, the present invention divides the radio resource shared by the macro and femto base station and classifies the divided resources into groups. One of the groups is assigned a macro base station-preferred priority, and the other is assigned a femto base station-preferred priority. 
     Means for Solving the Problem 
     In order to solve the above problems, a radio resource allocation method of a base station for controlling power of a terminal in a mobile communication system including a plurality of femto base stations in a service coverage of a macro base station according to the present invention includes dividing the radio resource shared by the macro and femto base stations into groups according to a predetermined rule, allocating the radio resource to each base station with the priority for use of maximum transmit power in specific radio resource group, and transmitting information on the allocated radio resource to the terminal. 
     Also, a power control method of a terminal in a mobile communication system including a plurality of femto base station in a service coverage of a macro base station according to the present invention includes receiving inform on radio resources allocated to use with maximum transmit power from one of the macro and femto base stations; transmitting at the maximum transmit power to the base station in communication with the terminal in a radio resource region configured to use the maximum transmit power; and transmitting at a transmit power below the maximum transmit power to the base station in communication with the terminal in a radio resource region excepted for the radio resource region configured to use the maximum transmit power. 
     Also, a base station allocating radio resource for power control of a terminal in a mobile communication system including a plurality of femto base station in a service coverage of a macro base station according to the present invention includes a scheduler which performs scheduling by dividing the radio resource shared by the macro and femto base stations into groups according to a predetermined rule and allocating the radio resource to each base station with the priority for use of maximum transmit power in specific radio resource group and a radio communication unit which transmits information on the allocated radio resource to the terminal. 
     Furthermore, a power control apparatus for controlling transmit power on radio resource for transmission to a base station in a mobile communication system including a plurality of femto base stations in a service coverage of a macro base station according to the present invention includes an RF communication unit which transmits subframes to the base station by adjusting transmit power level, a priority determiner which determines a radio resource group corresponding to a subframe using an number of the subframe to be transmitted to the base station and determines whether the radio resource group is the group in which the base stations is assigned usage priority of maximum transit power; and a power control unit which controls the RF communication unit to set the transmit power to the maximum transmit power for the radio resource group in which the base station is assigned usage priority of maximum transit power and to a restricted transmit power, below the maximum transmit power, for the radio resource group in which the base station is not assigned the usage priority of the maximum transmit power. 
     Advantageous Effects 
     In the present invention, the radio resource shared by the base stations is divided into groups in time or frequency domain that are used at different transmit powers so as to control the interferences between the terminal communicating with a macro cell and the terminal communication with a femto cell efficiently. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of a typical femto cell system. 
         FIG. 2  is a diagram illustrating interference problem occurring in forward or reverse channels of macro base station and femto base station in the conventional femto cell system. 
         FIG. 3  is a diagram illustrating variation of the service coverage by dividing the radio resource shared by the macro base station  210  and the femto cell base station  120  into groups and assigning priority for use of maximum transmit power. 
         FIG. 4  is a block diagram illustrating a configuration of the base station according to an embodiment of the present invention. 
         FIG. 5  is a block diagram illustrating a configuration of the terminal  110  according to an embodiment of the present invention. 
         FIG. 6  is a diagram illustrating a method for dividing the reverse radio resource into groups in unit of interlace and assigning priority to a base station for use of the resource groups. 
         FIG. 7  is a flowchart illustrating a power control procedure of the terminal  110  according to the first embodiment of the present invention. 
         FIG. 8  is a diagram illustrating a procedure for grouping the reverse radio resources into ordered pairs of multiplexes. 
         FIG. 9  is a diagram illustrating a resource allocation state in which the reverse radio resource is divided into ordered multiplex pairs and assigned to a specific base station with priority. 
         FIG. 10  is a flowchart illustrating a power control procedure of the terminal  110  according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following, the micro base station means the indoor base station such as the pico cell base station or the femto cell base station that can be installed in a building or home and the description is made under the assumption that the micro base station is the femto cell. However, it is not necessary to limit the micro base station appeared in the present invention to the femto cell base station. 
     Although the description is directed to a mobile communication based on CDMA HRPD (Code Division Multiple Access High Rate Packet Data), i.e., 1×EVDO (1× Evolution-Data Only), the technical configuration of the present invention is not limited thereto. Since the reverse radio resource is divided into subframes in time domain, the terms radio resource and subframes can be interchangeably used with each other in the following description. 
     The power control method of the present invention is described with the first and second embodiments discriminated based on the resource grouping scheme. 
     In this case, the first embodiment describes a method for controlling power by dividing the reverse radio resource shared by the base stations into groups in unit of interlace. And, the second embodiment describes a method for controlling power by dividing the reverse radio resource shared by the base stations into groups in unit of interface and regrouping the groups into multiplex as plural time units. 
     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 diagram illustrating a configuration of a mobile communication system including a typical femto cell base station. The femto cell system includes a terminal  110 , a femto cell base station  120 , a modem  130 , the Internet  140 , a gateway  150 , and a macro network  160 . 
     The terminal  110  connects to the femto cell base station  120  via radio access. The terminal  110  can be any of a portable terminal such as Personal Digital Assistant (PDA) and Smart Phone, Personal Computer (PC), and laptop computer, as well as mobile communication terminal. 
     The femto cell base station  120  means a micro base station for use in indoor environment such as home and office, and it is assumed to be installed at any place where the user want. The femto cell base station  20  connects to the Internet  140  through the modem  130  installed at an indoor place and then to the macro network  160  via the gateway  150 . That is, the femto cell base station  120  connects to the core network (macro network in drawing) via the Internet so as to provide the terminal  110  with the mobile communication service. 
       FIG. 2  is a diagram illustrating a situation incurring interference on the forward or reverse channel between the macro base station  210  and the femto cell base station  120  in the conventional mobile communication system. 
     First of all, it is assumed that the macro base station  210  and a plurality of femto cell base stations  120 A,  120 B, and  120 C are located within the coverage of the macro cell  220 . Simultaneously, it is assumed that the terminal  110  communicating with the macro base station  210  moves along the line connecting the first to third positions to pass by the femto cell base stations. 
     In case that the terminal  110  communicates with the macro base station  210  at a location out of the coverage of the femto cell base stations  120 A,  120 B, and  120 C, no interference occurs between the macro base station  210  and the femto cell base stations  120 A,  120 B, and  120 C. 
     However, when passing the first position, the terminal  110  is located near the communication radius of the femto cell base station  120 A so as to be likely to experience interference to the communication with the macro base station  210 . Also, when passing the second position, the terminal  110  is located near the communication radius of the femto cell base station  120 B so as to be likely to experience interference to the communication with the macro base station  210 , and similarly, when passing the third position, located near the communication radius of the femto cell base station  120 C to experience interference to the communication with the macro base station  210 . 
     Although the description is directed to the interference problem to the terminal  110  communicating with the macro base station  210  moves, this can be applied to the terminal communicating with a femto cell base station. 
     In order to solve this problem, the present invention divides the forward or reverse radio resource shared by the macro base station  210  and the femto cell base station  120  into groups in unit of segmentation unit and assigns priority to a specific base station for use of maximum transmission power in group. 
       FIG. 3  is a diagram illustrating variation of the service coverage by dividing the radio resource shared by the macro base station  210  and the femto cell base station  120  into groups and assigning priority for use of maximum transmit power. 
     Part [a] of  FIG. 3  shows the service coverage of the macro base station  210  and the femto cell base station  120  when not priority is assigned to the radio resource. In part [a] of  FIG. 3 , the service coverage boundary between the macro base stations is referred to as the first boundary and the service coverage boundary between the macro base station  210  and the femto base station  120  is referred to as the second boundary. 
     In this case, if the terminal  100  approaches the second boundary formed between the macro base station  210  and the femto cell base station  120 , the interference occurs on the radio resource shared by them. Accordingly, the present invention proposes a method for dividing the radio resource shared by the macro base station  210  and the femto cell base station  120  into groups and assigning the maximum transmit power usage priority of one group to the macro base station  210  and the maximum transmit power usage priority of the other group to the femto cell base station  120 . 
     According to the proposed method, the service coverages of the macro base station  210  and the femto cell base station  120  are changed as shown in part [b] of  FIG. 3 . 
     The macro base station  210  and the femto cell base station  120  can transmit data to the terminal  100  at the maximum transmit power on the radio resource groups to which they are assigned priorities, respectively. Similarly, the terminal  110  can transmit data to the macro base station  210  and the femto cell base station on the respective radio resource groups at the maximum transmit powers, respectively. 
     Meanwhile, the macro base station  210  and the femto base station  120  can use the limited transmit power in the radio resource groups for which no maximum transmit power usage priority is assigned. Similarly, the user terminal can use only the limited transmit power in the radio resource groups for which no maximum transmit power usage priority is assigned to the corresponding macro base station  210  and the femto cell base station  120 . Here, if the user can use the limited transmit power, this mean using the power corresponding to a specific value below the predetermined maximum transmit power or the power corresponding to a specific percentage of the maximum transmit power. 
     The above operations are described in association with part [b] of  FIG. 3 . In the radio resource group for which the macro base station  210  has priority, the macro base station  210  and the terminal  110  connected to the macro base station  210  can us the maximum transmit power. Accordingly, the service coverage of the macro base station  210  is expanded from the previous second boundary to the third boundary. Oppositely, in the radio resource group for which the macro base station has the priority, the service coverage of the femto cell base station shrinks from the second boundary to the third boundary. 
     Meanwhile, in the radio resource group for which the femto cell base station has the priority, the femto cell base station  120  and the terminal  110  connected to the femto cell base station  120  can use the maximum transmit power. Accordingly, the service coverage of the femto cell base station expanded from the second boundary to the fourth boundary. Oppositely, in the radio resource group for which the femto cell base station  120  has the priority, the service coverage of the macro base station decreases from the second boundary to the fourth boundary. 
       FIG. 4  is a block diagram illustrating a configuration of the base station according to an embodiment of the present invention. Here, the block diagram can be applied to both the macro base station  210  and femto cell base station  120 . The base station can include an RF communication unit  410 , a storage unit  420 , and a control unit  430  having a scheduler  430 A. 
     The RF communication unit  410  includes an RF transceiver and a duplexer and is responsible for the typical base station function such as RF transmission/reception process. The RF communication unit  410  transmits the data signal selected under the control of the control unit  430  to the terminal  110 . The storage unit  420  can stores programs and data necessary for the overall operations of the base station according to an embodiment of the present invention. Particularly, the storage unit  420  can store the data received from a higher network node per terminal or service. 
     The control unit  430  controls the overall operations of the base station according to an embodiment of the present invention. In this case, the control unit  430  can assign the radio resources to the respective base station so as to use the maximum transmit power in different resource regions. The control unit  430  also can assign the radio resource such that the terminal  110  can use the maximum transmit power in the resource region for which a certain base station has the usage priority. 
     Particularly, the control unit  430  according to an embodiment of the present invention can include a scheduler  430 A. The scheduler  430 A controls the data stored in the storage unit  420  selectively in consideration of the resource division information proposed in the present invention, transmit power information per resource, forward channel status information transmitted by the terminal  110 , service characteristic, and fairness. That is, the scheduler  430  can control the RF communication unit  410  to transmit the data to the terminal  110  at the maximum transmit power in the radio resource group for which the base station has the usage priority. In more detail, the scheduler  430 A according to an embodiment of the present invention divides the radio resource shared by macro base station and the femto cell base station into groups according to a predetermined rule. Next, the scheduler  430 A can perform scheduling by allocating the radio resource groups such that the terminal  110  uses the maximum transmit power in the respective resource groups for plural base stations. 
       FIG. 5  is a block diagram illustrating a configuration of the terminal  110  according to an embodiment of the present invention. The terminal  110  can include an RF communication unit  510 , a data processing unit  520 , a storage unit  530 , and a control unit  540 . The control unit  540  can include a priority determiner  540 A and a power controller  540 B. 
     The RF communication unit  510  includes an RF transceiver and a duplexer and is responsible for performing the general functions of the terminal  110  such as RF transmission/reception process. Particularly, the RF communication unit  510  adjusts the transmit power level to transmit the radio resource to the base station (macro base station or femto cell base station) under the control of the power controller  550 B. 
     The data processing unit  520  can include a transmit data processor and a receive data processor (not shown). The transmit data processor can include a coder for encoding transmission signal, a modulator for modulating the coded signal, and a digital-analog converter for converting the modulated signal to an analog signal. Here, the coder can include a data coder for processing packet data and an audio coder for processing audio signal including voice. 
     The receive data processor can include an analog-digital converter for converting the analog signal output by the RF communication unit  510  to a digital signal, a demodulator for demodulating the modulated signal, and a decoder for decoding the modulated signal. Here, the decoder can includes a data decoder for processing packet data and an audio decoder for processing audio signal including voice. 
     The storage unit  530  can store the programs and data necessary for the operations of the terminal  110  according to an embodiment of the present invention. 
     The control unit  540  controls the overall operations of the terminal  110  according to an embodiment of the present invention. Particularly, the control unit  540  can includes a priority determiner  540 A and a power controller  540 B. 
     The priority determiner  540 A determines the radio resource group corresponding to the radio resource based on the number of the subframe as the time unit of reverse radio resource. Here, the segmentation unit for dividing the radio resource can be interlace or order pair of interlace and multiplex (interlace and multiplex are described later). The priority determiner  540 A determines whether the determined radio resource group is the group assigned the priority to use the maximum transmit power for the base station communicating with the terminal  110 . 
     The power controller  540 B controls such that the transmit power of the RF communication  510  is set to maximum value for the radio resource group assigned the priority according to the determination result of the priority determiner  540 A. Meanwhile, the power controller  540 B controls such that the transmit power of the RF communication unit  510  is set to a value in a restricted range for the radio resource group to which priority is not assigned. 
     The power control methods according to the first and second embodiments of the present invention are described hereinafter. Although the description is directed to the case of the power control method of the terminal for reverse radio resource, the present invention can be applied to the power control of the base station for forward radio resource in the same principle. 
     First Embodiment 
     The first embodiment relates to a method for dividing the reverse radio resource shared by the base stations (i.e., macro and femto cell base stations) in unit of interlace and assigning priority to a specific base station for use of a radio resource group in the interlace. That is, according to the first embodiment of the present invention, the unit of the dividing the radio resource into groups is interlace. 
     In HRPD system, the reverse radio resource is divided into subframes in time domain. One or more terminals  110  transmit data to the macro base station  210  or the femto cell base station  220  which is in communication with. The description is made under the assumption that the radio resource is subframe. 
     In HRPD system, the terminal  110  can retransmit the physical layer packet transmitted previously at an interval of four subframes. According to the interval at which synchronized HARQ occurs, the subframes as the radio resource are discriminated as 4 radio resource groups. Here, the radio resource groups generated by dividing the radio resource in a retransmission period can be referred to as interlaces. 
     In more detail, assuming the subframes numbered 0, 1, 2, 3, 4, 5, 6, . . . , n in the HARQ system, the 0 th  subframe constitutes the first radio resource group (interlace  0 ) along with the 4 th , 8 th , . . . , (4n) th  subframes in which its retransmission occurs. Likewise, the 1 st , 5 th , 9 th , . . . , (4n+1) th  subframes constitute the second resource group (interlace  1 ), the 2 nd , 6 th , 10 th , . . . , (4+2) th  subframes constitute the third resource group (interlace  2 ), and the 3 rd , 7 th , 11 th , and (4n+3) th  subframes constitute the fourth resource group (interlace  3 ). 
       FIG. 6  is a diagram illustrating a method for dividing the reverse radio resource into groups in unit of interlace and assigning priority to a base station for use of the resource groups. 
     First of all, part [a] of  FIG. 6  shows the resource allocation state in which the macro base station  210  is assigned the priority for use of the radio resource groups corresponding to the interlaces  0  to  2  in the reverse radio resource shared by the macro base station  210  and the femto cell base station  120 . 
     According to part [a] of  FIG. 6 , when assigning the reverse resource to the terminal  110  in communication with the macro base station  210 , the macro base station  210  can configure such that the terminal  110  can use the maximum transmit power for the radio resource groups corresponding to the interlaces  0  to  2 . Meanwhile, the macro base station  210  can configure such that the terminal  110  can use the restricted transmit power for the radio resource group corresponding to the interlace  3 . 
     Part [b] of  FIG. 6  shows the resource allocation state in which the femto cell base station  120  is assigned the priority for use of the radio resource group corresponding to the interlace  3 . 
     According to [b] of  FIG. 6 , when assigning the reverse resource to the terminal  110  in communication with the femto cell base station  210 , the femto cell base station  120  can configure such that the terminal  110  can use the maximum transmit power for the radio resource group corresponding to the interlace  3 . Meanwhile, the femto cell base station  120  can configure such that the terminal  100  can use the restricted transmit power for the radio resource groups corresponding to the interlaces  0  to  2 . 
     As shown in parts [a] and [b] of  FIG. 6 , the macro base station  210  secures the service coverage expanded as compared to the conventional system coverage in the radio resource groups corresponding to the interlaces  0  to  2 . Accordingly, the terminal  110  in communication with the macro base station  210  can maintain the communication with the macro base station  210  stably in the resource region of the radio resource groups corresponding to the interlaces  0  to  2  even inside of the coverage boundary of the femto cell base station  120 . 
     Likewise, the femto cell base station  120  secures the service coverage expanded as compared to the conventional system coverage in the radio resource group corresponding to the interlace  3 . Accordingly, the terminal  110  in communication with the femto cell base station  120  can maintain the communication with the femto cell base station  120  stably in the resource region of the radio resource group corresponding to the interlace  3  even inside of the coverage boundary of the macro base station  210 . 
     A description is made of the method for notifying the terminal  110  of the radio resource allocation information with base station-specific priorities hereinafter. First of all, when the terminal  110  is assigned physical layer resource from a specific base station or adds the specific base station to its Active Set, the resource allocation information can be transferred to the terminal  110  in the form of a message (hereinafter, ‘resource allocation message’). Also, the base station can transmit the radio resource allocation information to the terminal by means of the Configuration Attribute used when negotiating the data transmission scheme with the terminal. 
       FIG. 7  is a flowchart illustrating a power control procedure of the terminal  110  according to the first embodiment of the present invention. 
     First of all, the terminal  110  checks the sequence number of the reverse radio resource (i.e., subframe number) for transmission to the macro base station  210  of the femto base station  20  at step S 710 . Next, the terminal  110  calculates the interlace for determining the radio resource group of the subframe at step S 720 . 
     In this case, the terminal  110  calculates the interlace (i) using the value obtained by dividing the reverse subframe number (n) by the total number of interlaces (t). In an exemplary case that the total number of the interlaces per subframe is 4 (t=4) and the current subframe number is 7 (n=7), the interlace (i) is 3 (n/t). 
     The terminal  110  determines whether the radio resource corresponding to the calculated interlace belongs to the resource group for which the base station in communication with the terminal  110  is assigned the priority of maximum transmit power use. 
     In this case, the terminal  110  can check the radio resource group for which the base station in communication with the terminal  110  is assigned the priority of maximum transmit power usage by referencing the resource allocation message received from the base station as described above. Here, the resource allocation message can include the information on the resources that are allocated to the macro and femto cell base stations with maximum transmit power. 
     According to another embodiment of the present invention, the terminal  110  can check the radio resource group for which the base station in communication with the terminal  110  is assigned the maximum transmission power use priority based on the Configuration Attribute used in data transmission scheme negotiation with the base station. 
     If the priority is assigned, the terminal  110  sets the transmit power of the reverse subframe to the maximum transmit power at step S 740 . Next, the terminal  110  performs scheduling and data transmission in the current subframe using the maximum transmit power at step S 760 . 
     Otherwise, if the priority is not assigned, the terminal  110  sets the transmit power of the reverse subframe to a restricted transmit power at step S 750 . Here, the restricted transmit power can be a value equal to a specific percentage of the maximum transmit power or a value obtained by subtracting a predetermined offset value from the maximum transmit power. The terminal performs scheduling and data transmission operation in the current subframe using the transmit power value at step S 760 . 
     Second Embodiment 
     The second embodiment relates to a method for dividing the reverse radio resource shared by base stations into groups in unit of interlace and then regrouping the resource into multiplexes to control power. According to the second embodiment of the present invention, the division unit for grouping the radio resource is a ordered pair consisted of the interlace and multiplex. 
       FIG. 8  is a diagram illustrating a procedure for grouping the reverse radio resources into ordered pairs of multiplexes. 
     In part [a] of  FIG. 8 , a specific interlace, i.e. interlace  2  is depicted, among a plurality of interlaces (interlaces  0  to  3 ). The interlace  2  depicted in part [a] of  FIG. 8  is divided into a plurality of multiplexes in time domain. According to an embodiment of the present invention, the interlace is divided into 4 multiplexes (multiplexes  0  to  3 ). 
     In part [b] of  FIG. 8 , the ordered pair of multiplexes in the interlace divided into multiplexes. As shown in part [b] of  FIG. 8 , when the interlace  2  is divided into 4 multiplexes, the ordered multiplex pairs can be composed of the first radio resource group (ordered multiplex pair ( 2 , 0 )), the second radio resource group (ordered multiplex pair ( 2 , 1 )), the third radio resource group (ordered multiplex pair ( 2 , 2 ), and the fourth radio resource group (ordered multiplex pair ( 2 , 3 ). In the second embodiment of the present invention, the radio resource is divided into groups in unit of ordered multiplex pair, and a specific base station is assign the priority for the radio resource group of the ordered multiplex pair. 
       FIG. 9  is a diagram illustrating a resource allocation state in which the reverse radio resource is divided into ordered multiplex pairs and assigned to a specific base station with priority. 
     First of all, part [a] of  FIG. 9  shows a state in which the radio resource group corresponding to the ordered multiplex pairs ( 2 , 0 ) and ( 2 , 1 ) is assigned to the femto cell base station A  120 A with priority. 
     In case of assigning reverse resource to the terminal  110  in communication with the femto cell base station A  120 A, the femto cell base station A  120 A configures such that the terminal  110  uses the maximum transmit power for the ordered multiplex pair. However, the femto cell base station A  120 A configures such that the terminal  110  uses a restricted transmit power for the reset resource. 
     Part [b] of  FIG. 9  shows a state in which the radio resource group corresponding to specific multiplex pairs ( 2 , 2 ) and ( 2 , 3 ) are assigned to the femto base station B  120 B with priority. 
     In case of assigning reverse resource to the terminal  110  in communication with the femto cell base station B  120 B, the femto cell base station B  120 B configures such that the terminal  110  uses the maximum transmit power for the ordered multiplex pairs. However, the femto call base station B  120 B configures such that the terminal  110  uses a restricted transmit power for the rest resource. 
     Although the description is directed to the case where the ordered multiplex pairs are assigned to the femto base station A  120 A and the femto base station B  120 B, it is not limited thereto. That is, certain radio resource groups can be assigned to a macro base station and other femto base stations other than the femto cell base stations A and B. 
       FIG. 10  is a flowchart illustrating a power control procedure of the terminal  110  according to the second embodiment of the present invention. 
     First of all, the terminal  110  checks the sequence number of the current reverse radio resource, i.e. the subframe number, for the transmission to the macro base station  210  or femto cell base station  120  in communication with at step S 1010 . Next, the terminal  110  calculates the interlace and multiplex for determining the radio resource group in the subframe at steps S 1020  and S 1030 . 
     In detail, the terminal  110  calculates the interlace (i) using the value obtained by dividing the reverse subframe number (n) by the total number of interlaces (t 1 ) at step S 1020 . Next, the terminal  110  floors the value obtained by dividing the reverse subframe number (n) by the total number of interlaces (t 1 ) and then calculates the multiplex (m) using the remainder of the value obtained by dividing the result by the total number of multiplexes (t 2 ). In this manner, the terminal  110  can acquire the ordered multiplex pair (i, m). 
     Next, the terminal  110  determines the radio resource group using the ordered multiplex pair calculated as above and judges whether the determined radio resource group is the group assigned to the base station in the current communication with the priority at step S 1040 . As described above, the terminal  110  can identify the ordered multiplex pair for which the base station in communication with the terminal is assigned the priority by means of the resource allocation message or Configuration Attribute received from the base station. 
     If the priority is assigned, the terminal  110  set the transmit power of the reverse subframe to the maximum transmit power at step S 1050 . Next, the terminal  110  performs scheduling and data transmission in the current subframe using the maximum transmission power value at step S 1070 . 
     Otherwise, if the priority is not assigned, the terminal  110  sets the transmit power of the reverse subframe to a restricted transmit power at step S 1060 . Herein, the restricted transmit power can be a value equal to a specific percentage of the maximum transmit power or a value obtained by subtracting a predetermined offset value from the maximum transmit power. Next, the terminal  110  performs scheduling and data transmission operation in the current subframe using the transmit power value at step S 1070 . 
     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.

Technology Classification (CPC): 7