JP2011124857A - Radio communication system, radio base station, radio terminal, and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system which suppresses an influence of interference that a radio base station receives from a radio terminal in an up link. <P>SOLUTION: The radio communication system includes the following steps: a large-cell base station 100 transmits by radio interference control information for controlling the influence of interference that the large-cell base station 100 receives in the up link (step S102); a radio terminal 300a connected to a small-cell base station 200a relays the received interference control information to the small-cell base station 200a, when receiving the interference control information from the large-cell base station 100 (step S103); and the small-cell base station 200a controls the radio communication of the radio terminal 300a in the up link, based on the interference control information relayed from the radio terminal 300a (step S104). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio communication system, a radio base station, a radio terminal, and a communication control method related to a radio communication environment in which a plurality of cells having different sizes are used in a mixed manner.

  LTE standardized by 3GPP, a standardization organization for wireless communication systems, as a next-generation wireless communication system that realizes higher-speed and larger-capacity communication than the currently used third-generation and 3.5-generation wireless communication systems There is. Technical specifications of LTE have been determined as 3GPP Release 8, and Release 9 which is an improved version of Release 8 and LTE Advanced which is an advanced version of LTE are currently being studied.

  LTE Release 9 is a small cell base station ("Home eNodeB") that is a small radio base station that can be installed indoors by forming a small cell (called "femtocell") that is a communication area with a radius of several meters. Is being standardized (for example, see Non-Patent Document 1). The small cell base station is a radio base station (referred to as “Macro eNodeB”) that forms a large cell (referred to as “macro cell”) that is a communication area with a radius of several hundred meters. It is possible to distribute traffic and cover dead zones in large cells.

3GPP TS 36.300 V9.1.0 (2009-09), “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2,“ 4.6 Support of HeNB ””

  However, in the uplink (in the direction from the radio terminal to the radio base station), the small cell terminal that is a radio terminal connected to the small cell base station has the same frequency as the large cell terminal that is a radio terminal connected to the large cell base station. When using the bandwidth for communication, there are the following problems. Specifically, there is a problem that the communication speed of the large cell terminal in the uplink decreases due to the large cell base station being affected by interference from the small cell terminal.

  Therefore, an object of the present invention is to provide a radio communication system, a radio base station, a radio terminal, and a communication control method that can suppress the influence of interference that the radio base station receives from radio terminals in the uplink.

  In order to solve the above-described problems, the present invention has the following features. First, a radio communication system (for example, radio communication system 1A) according to the present invention includes a first radio base station (for example, large cell base station 100), a second radio base station (for example, small cell base station 200a), Interference control information for controlling the influence of interference received by the first radio base station in the uplink, the radio terminal connecting to two radio base stations (for example, the radio terminal 300a). When the radio terminal receives the interference control information from the first radio base station, the radio terminal relays the received interference control information to the second radio base station, and the second radio base station The gist is to control radio communication of the radio terminal in the uplink based on the interference control information relayed from the radio terminal.

  According to such a feature, the radio terminal relays the interference control information transmitted by the first radio base station by radio to the second radio base station, and the second radio base station is uplinked based on the relayed interference control information. Control wireless communication of wireless terminals on the link. Thereby, the influence of the interference which a 1st wireless base station receives from a wireless terminal in an uplink can be suppressed.

  In the above feature, the first radio base station may broadcast the interference control information.

  In the above feature, the first radio base station may periodically broadcast the interference control information.

  In the above feature, the first radio base station may be a large cell base station that forms a large cell, and the second radio base station forms a small cell that is smaller than the large cell, and It may be a small cell base station that can be installed in a cell.

  In the above feature, the radio terminal may attempt to receive the interference control information when it is confirmed that the second radio base station is the small cell base station.

  In the above feature, the radio terminal may determine whether to receive the interference control information based on information received from the second radio base station.

  In the above feature, the radio terminal may determine whether to relay the interference control information to the second radio base station based on information received from the first radio base station.

  In the above feature, the second radio base station changes at least one of transmission power or a used frequency band of the radio terminal in the uplink based on the interference control information relayed from the radio terminal.

  In the above feature, when there are a plurality of the second radio base stations, the first radio base station includes a plurality of information elements addressed to the second radio base stations, respectively, and transmits the interference control information. Each of the second radio base stations selects an information element addressed to itself from the information elements included in the interference control information relayed from the radio terminal, and based on the selected information element, the uplink radio station The wireless communication of the wireless terminal may be controlled.

  The radio base station (for example, the large cell base station 100) according to the present invention is information for controlling the influence of interference received by the own station in the uplink, and is transmitted to other radio base stations (for example, the small cell base station 200a). The gist is to include a generation unit (for example, the control unit 120) that generates interference control information to be transmitted and a transmission unit (for example, the wireless communication unit 110) that transmits the interference control information by radio.

  A radio terminal (for example, radio terminal 300a) according to the present invention is a radio terminal connected to a radio base station (for example, small cell base station 200a), and other radio base stations (for example, large cell base station 100) in the uplink. A receiving unit (for example, the radio communication unit 310) that receives interference control information for controlling the influence of interference received from the other radio base station, and when the receiving unit receives the interference control information, The gist of the present invention is to include a transmission unit (for example, a wireless communication unit 310) that transmits interference control information to the wireless base station.

  The radio base station (for example, the small cell base station 200a) according to the present invention is a radio base station to which a radio terminal (for example, the radio terminal 300a) is connected, and other radio base stations (for example, the large cell base station 100 in the uplink). ) For receiving the interference control information relayed by the wireless terminal from the wireless terminal (for example, the wireless communication unit 210) and the receiving unit from the wireless terminal. The gist of the present invention is to include a control unit (for example, the control unit 220) that controls radio communication of the radio terminal in the uplink based on the received interference control information.

  In the communication control method according to the present invention, the first radio base station wirelessly transmits interference control information for controlling the influence of interference received by the first radio base station in the uplink (for example, step S102). When the radio terminal connected to the second radio base station receives the interference control information from the first radio base station, the step of relaying the received interference control information to the second radio base station (step S103) And the second radio base station has a step (step S104) of controlling radio communication of the radio terminal in the uplink based on the interference control information relayed from the radio terminal (step S104). .

  According to the present invention, it is possible to provide a radio communication system, a radio base station, a radio terminal, and a communication control method that can suppress the influence of interference received by radio base stations from radio terminals in the uplink.

1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. It is a block diagram which shows the structure of the large cell base station which concerns on embodiment of this invention. It is a block diagram which shows the structure of the small cell base station which concerns on embodiment of this invention. It is a block diagram which shows the structure of the radio | wireless terminal which concerns on embodiment of this invention. It is a sequence diagram which shows the whole schematic operation | movement of the radio | wireless communications system which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the large cell base station which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radio | wireless terminal which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the small cell base station which concerns on embodiment of this invention. It is an operation | movement sequence diagram of the radio | wireless communications system which concerns on the example 1 of a change of embodiment of this invention. It is a schematic block diagram of the radio | wireless communications system which concerns on the modification 4 of embodiment of this invention. It is a schematic block diagram of the radio | wireless communications system which concerns on the modification 5 of embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of radio communication system, (2) detailed configuration of radio communication system, (3) operation of radio communication system, (4) effects of embodiment, (5) other embodiments explain. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Schematic Configuration of Radio Communication System FIG. 1 is a schematic configuration diagram of a radio communication system 1A according to this embodiment. The wireless communication system 1A is, for example, a configuration based on LTE Release 9, which is a 3.9th generation (3.9G) mobile phone system, or LTE-Advanced, which is positioned as a 4th generation (4G) mobile phone system. It has a configuration based on.

  In the radio communication system 1A, an OFDMA (Orthogonal Frequency Division Multiple Access) scheme is used as a downlink multiplexing scheme, and an SC-FDMA (Single-Carrier Frequency Division Multiple Access) scheme is used as an uplink multiplexing scheme. Further, an FDD (Frequency Division Duplex) method is used as a duplex method. However, the duplex method is not limited to FDD, and a TDD (Time Division Duplex) method may be used.

  As shown in FIG. 1, the radio communication system 1A includes a large cell base station 100 that forms a large cell LC and small cell base stations 200a and 200b that form small cells SC1 and SC2, respectively. However, since the small cell base stations are arbitrarily installed by the user, the number of small cell base stations of the large cell LC is not limited to the number shown in FIG. 1 and changes with the passage of time.

  The large cell LC is a communication area having a radius of about several hundred meters, for example, and is called a macro cell. Each of the small cells SC <b> 1 and SC <b> 2 is a communication area having a radius of, for example, about several meters to about several tens of meters, and is called a femto cell. In LTE and LTE-Advanced, the small cell base station is referred to as a home eNodeB (HeNB), and the large cell base station is referred to as a macro eNodeB (MeNB).

  A radio terminal 300a is connected to the small cell base station 200a, and a radio terminal 300b is connected to the small cell base station 200b. A radio terminal 400 is connected to the large cell base station 100.

  The small cell base station 200a controls the wireless communication of the wireless terminal 300a. For example, the small cell base station 200a determines radio resources (time and frequency band) to be allocated to the radio terminal 300a for each uplink and downlink, and controls transmission power of the radio terminal 300a in the uplink. Similarly, the small cell base station 200b controls the radio communication of the radio terminal 300b.

  Each of the small cell base stations 200a and 200b is configured to be small enough to be installed in an arbitrary place (specifically, indoors) by the user. The small cell base stations 200a and 200b can be installed in the large cell LC for the purpose of distributing the traffic of the large cell base station 100 and covering the dead zone in the large cell LC.

  In the example of FIG. 1, the small cell base station 200a is installed in the large cell LC, and the small cell base station 200b is installed outside the large cell LC. The radio terminal 300a connected to the small cell base station 200a installed in the large cell LC has a high possibility of affecting the large cell base station 100 in the uplink.

  Specifically, when the small cell base station 200a and the radio terminal 300a use the same frequency band as the large cell base station 100 and the radio terminal 400 for radio communication, the radio signal transmitted by the radio terminal 300a is transmitted to the large cell base station. 100 is affected by interference. As a result, the uplink communication speed between the radio terminal 400 and the large cell base station 100 decreases. In addition, the arrow of the broken line in FIG. 1 has shown the interference signal.

  On the other hand, the radio terminal 300b connected to the small cell base station 200b installed outside the large cell LC is less likely to affect the large cell base station 100 in the uplink.

  In the radio communication system 1A, the uplink communication between the radio terminal 400 and the large cell base station 100 is performed by performing interference control on the radio terminal 300a that is highly likely to affect the large cell base station 100 in the uplink. Suppresses the decrease in speed.

  Here, an outline of the interference control method according to the present embodiment will be described.

  First, the large cell base station 100 wirelessly transmits interference control information for controlling the influence of interference received by the large cell base station 100 in the uplink. Interference control information refers to Overload Indicator (OI) or High Interference Indicator (HII) already defined in LTE or LTE-Advanced, or newly defined interference control information (from a small cell terminal to large cell base station 100). The value of the interference power density that can be given is considered).

  In the present embodiment, the large cell base station 100 periodically transmits interference control information. Broadcast transmission means that interference control information is transmitted to an unspecified number of radio terminals in the large cell LC. Specifically, the large cell base station 100 transmits the interference control information using (predetermined) radio resources known to the radio terminal. In LTE and LTE-Advanced, radio resources are configured by a combination of time and frequency band.

  The radio terminal 300a attempts to receive interference control information. That is, the radio terminal 300a attempts to receive interference control information in a predetermined time, frequency band, and signal format while continuing radio communication with the small cell base station 200a. The radio terminal 300a located in the large cell LC can receive the interference control information from the large cell base station 100. On the other hand, the radio terminal 300b cannot receive the interference control information from the large cell base station 100 even if it tries to receive the interference control information.

  When receiving the interference control information from the large cell base station 100, the radio terminal 300a relays the received interference control information to the small cell base station 200a. The radio terminal 300a uses a predetermined time / frequency band / signal format or the time / frequency band / signal format notified from the small cell base station 200a for relaying.

  When the small cell base station 200a receives the interference control information from the radio terminal 300a, based on the received interference control information, the small cell base station 200a is configured to suppress the influence of interference on the large cell base station 100 in the uplink. The wireless communication of the wireless terminal 300a is controlled. For example, the small cell base station 200a changes at least one of the transmission power and the used frequency band of the radio terminal 300a by a predetermined method.

(2) Detailed Configuration of Radio Communication System Next, a detailed configuration of the radio communication system 1A will be described. Specifically, a description (2.1) Configuration of the large cell base station 100, (2.2) Configuration of the small cell base station 200a, (2.3) The configuration of the wireless terminal 300a.

(2.1) Configuration of Large Cell Base Station 100 FIG. 2 is a block diagram showing the configuration of the large cell base station 100. As shown in FIG. 2, the large cell base station 100, an antenna section 101, radio communication unit 110, the control unit 120, storage unit 130 and the wired communication unit 140.

  The wireless communication unit 110 is configured using, for example, a radio frequency (RF) circuit, a baseband (BB) circuit, or the like, and transmits and receives wireless signals to and from the wireless terminal 400 via the antenna unit 101. In addition, the wireless communication unit 110 performs encoding and modulation of a transmission signal and demodulation and decoding of a reception signal. The wireless communication unit 110 is controlled by the control unit 120.

  The control unit 120 is configured using, for example, a CPU, and controls various functions included in the large cell base station 100. The storage unit 130 is configured using a memory, for example, and stores various types of information used for controlling the large cell base station 100 and the like. The wired communication unit 140 communicates with a higher-level communication control node or another large cell base station via a core network (not shown) that is a wired communication network.

  In the present embodiment, the control unit 120 corresponds to a generation unit that generates interference control information for controlling the influence of interference received by the large cell base station 100 in the uplink. An example of generation of interference control information will be described later. The wireless communication unit 110 corresponds to a transmission unit that broadcasts the interference control information generated by the control unit 120 wirelessly.

(2.2) Configuration of Small Cell Base Station 200a FIG. 3 is a block diagram showing the configuration of the small cell base station 200a. As shown in FIG. 3, the small cell base station 200a includes an antenna unit 201, radio communication unit 210, the control unit 220, storage unit 230 and the wired communication unit 240.

  The wireless communication unit 210 is configured using, for example, an RF circuit, a BB circuit, or the like, and transmits and receives wireless signals to and from the wireless terminal 300a via the antenna unit 201. In addition, the wireless communication unit 210 performs encoding and modulation of a transmission signal and demodulation and decoding of a reception signal. The wireless communication unit 210 is controlled by the control unit 220.

  The control unit 220 is configured using a CPU, for example, and controls various functions provided in the small cell base station 200a. The storage unit 230 is configured using, for example, a memory, and stores various types of information used for controlling the small cell base station 200a. The wired communication unit 240 communicates with a higher-level communication control node via the core network.

  In the present embodiment, the wireless communication unit 210 corresponds to a reception unit that receives interference control information relayed by the wireless terminal 300a from the wireless terminal 300a. The control unit 220 corresponds to a control unit that controls the radio communication of the radio terminal 300a in the uplink based on the interference control information received by the radio communication unit 210 from the radio terminal 300a. A specific example of communication control for the wireless terminal 300a will be described later.

(2.3) Configuration of Radio Terminal 300a FIG. 4 is a block diagram showing the configuration of the radio terminal 300a. As illustrated in FIG. 4, the wireless terminal 300 a includes an antenna unit 301, a wireless communication unit 310, a control unit 320, a storage unit 330, and a battery 340.

  The wireless communication unit 310 is configured using, for example, an RF circuit, a BB circuit, or the like, and transmits and receives wireless signals to and from the small cell base station 200a via the antenna unit 301. In addition, the wireless communication unit 310 performs encoding and modulation of the transmission signal and demodulation and decoding of the reception signal. The wireless communication unit 310 is controlled by the control unit 320.

  The control unit 320 is configured using a CPU, for example, and controls various functions provided in the wireless terminal 300a. The storage unit 330 is configured using, for example, a memory, and stores various types of information used for controlling the wireless terminal 300a. The battery 340 stores electric power supplied to each block of the wireless terminal 300a.

  In the present embodiment, the wireless communication unit 310 corresponds to a receiving unit that receives interference control information from the large cell base station 100. Radio communication section 310 corresponds to a transmission section that transmits received interference control information to small cell base station 200a.

(3) Operation of Radio Communication System Next, the operation of the radio communication system 1A according to the present embodiment will be described. Specifically, (3.1) All outside outline operation, (3.2) Detailed operation of large cell base station 100, (3.3) Detailed operation of radio terminal 300a, (3.4) Small cell base station The detailed operation of 200a will be described.

(3.1) Overall Outside Operation FIG. 5 is a sequence diagram showing an overall outline operation of the wireless communication system 1A.

  In step S101, the radio terminal 300a connects to the small cell base station 200a. The radio terminal 300a performs uplink / downlink radio communication with the small cell base station 200a.

  In step S102, the large cell base station 100 transmits interference control information in a predetermined time, frequency band, and signal format. The radio terminal 300a receives the interference control information.

  In step S103, the radio terminal 300a relays the interference control information received from the large cell base station 100 to the small cell base station 200a. The small cell base station 200a receives the interference control information.

  In step S104, the small cell base station 200a controls radio communication of the radio terminal 300a in the uplink based on the interference control information received from the radio terminal 300a.

(3.2) Detailed Operation of Large Cell Base Station 100 Next, the operation of the large cell base station 100 will be described. FIG. 6 is a flowchart showing the operation of the large cell base station 100.

  In step S111, the control unit 120 of the large cell base station 100 generates interference control information. Here, an example of generation of interference control information will be described.

  First, when the interference control information is OI, the control unit 120 measures the level (high / medium / low) of interference received in each frequency band based on the radio signal received by the radio communication unit 110. The information of the measurement result is generated as OI.

  Secondly, when the interference control information is HII, the control unit 120 is information on a frequency band scheduled to be allocated to a radio terminal connected to the large cell base station 100 that is vulnerable to interference (for example, a radio terminal at the cell edge). As HII.

  Third, when the interference control information is newly defined information (for example, a value of interference power density that a small cell terminal may provide to a large cell base station), the control unit 120 generates the information. Perform the necessary processing.

  In step S112, the radio communication unit 110 of the large cell base station 100 transmits the interference control information generated by the control unit 120 in a predetermined time, frequency band, and signal format.

(3.3) Detailed Operation of Wireless Terminal 300a Next, the operation of the wireless terminal 300a will be described. FIG. 7 is a flowchart showing the operation of the wireless terminal 300a.

  When it is confirmed that the connection destination is the small cell base station 200a (step S121; YES), in step S122, the control unit 320 of the wireless terminal 300a sets the wireless communication unit 310 to try to receive interference control information. Control. Specifically, the control unit 320 controls the wireless communication unit 310 to perform reception using a predetermined time, frequency band, and signal format. The wireless communication unit 310 attempts to receive interference control information.

  When the radio communication unit 310 receives interference control information from the large cell base station 100 (step S123; YES), in step S124, the control unit 320 performs radio communication so as to transmit the received interference control information to the small cell base station 200a. The unit 310 is controlled. The radio communication unit 310 transmits interference control information to the small cell base station 200a. When transmitting interference control information to the small cell base station 200a, a predetermined time / frequency band / signal format or a time / frequency band / signal format notified from the small cell base station 200a is used. .

(3.4) Detailed Operation of Small Cell Base Station 200a Next, the operation of the small cell base station 200a will be described. FIG. 8 is a flowchart showing the operation of the small cell base station 200a.

  When the radio terminal 300a is connected (step S131; YES), in step S132, the control unit 220 of the small cell base station 200a controls the radio communication unit 210 so as to try to receive interference control information. Specifically, the control unit 220 controls the wireless communication unit 210 so as to perform reception in a predetermined or predetermined time / frequency band / signal format. The wireless communication unit 210 attempts to receive interference control information from the wireless terminal 300a.

  When the radio communication unit 210 receives interference control information from the radio terminal 300a (step S133; YES), in step S134, the control unit 220 causes the radio terminal 300a to communicate with the large cell base station 100 based on the received interference control information. The radio communication of the radio terminal 300a in the uplink is controlled so as to suppress the influence of the applied interference. Here, a specific example of communication control will be described.

  First, when the interference control information is OI, the control unit 220 uses, for example, a frequency band with a high interference level of the large cell base station 100 for uplink wireless communication with the wireless terminal 300a. If confirmed, control is performed to reduce the transmission power in the frequency band. Alternatively, the control unit 220 controls to change the frequency band used for uplink wireless communication with the wireless terminal 300a.

  Second, when the interference control information is HII, the control unit 220 does not use a frequency band scheduled to be allocated to, for example, a wireless terminal connected to the large cell base station 100 that is vulnerable to interference. The frequency band used for uplink wireless communication with 300a is determined.

  Third, when the interference control information is newly defined information (for example, a value of interference power density that a small cell terminal may give to a large cell base station), the control unit 220 performs communication using the information. Take control.

(4) Effect of Embodiment As described above, in the radio communication system 1A, the radio terminal 300a relays the interference control information transmitted by the large cell base station 100 by radio to the small cell base station 200a and is relayed. Based on the interference control information, the small cell base station 200a controls the radio communication of the radio terminal 300a in the uplink. Thereby, the influence of the interference which the large cell base station 100 receives from the radio | wireless terminal 300a in an uplink can be suppressed.

  In the present embodiment, the large cell base station 100 periodically transmits interference control information. By broadcast transmission, it is possible to simultaneously transmit interference control information to a plurality of small cell terminals in the same frequency band, and it is possible to reduce the frequency band consumption accompanying the transmission of interference control information.

  In the present embodiment, the radio terminal 300a attempts to receive interference control information when it is confirmed that the small cell base station 200a is a small cell base station. That is, reception of interference control information is omitted for a large cell base station (not shown) adjacent to the large cell base station 100. This is because interference control information can be transmitted between large cell base stations by communication between base stations using a high-speed wired line (core network).

(5) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

(5.1) Modification 1
In this modification, as shown in FIG. 9, the received information is transmitted from the small cell base station 200a to the radio terminal 300a according to the reception of the interference control information (step S202). The radio terminal 300a attempts to receive the interference control information only when the reception information indicates a reception instruction for the interference control information (step S203). Other processes are the same as those in the above-described embodiment.

  Thus, in this modification, the small cell base station 200a has the right to determine whether or not the radio terminal 300a receives the interference control information. The small cell base station 200a determines whether to allow the radio terminal 300a to receive the interference control information based on the following criteria.

  First, when the small cell base station 200a can receive the interference control information from the large cell base station 100 by inter-base station communication using a high-speed wired line (core network), the small cell base station 200a It is determined that the terminal 300a does not receive the interference control information. On the other hand, when the small cell base station 200a cannot receive the interference control information from the large cell base station 100 by communication between base stations using a high-speed wired line, the small cell base station 200a sends the interference control information to the radio terminal 300a. Is determined to be received.

  Second, when the path loss between the large cell base station 100 and the small cell base station 200a or the path loss between the large cell base station 100 and the radio terminal 300a is large, the small cell base station 200a It is determined that the interference control information is not received by 300a. This is because, when the path loss is large, it can be considered that the influence of interference exerted on the large cell base station 100 by the radio terminal 300a is small. On the other hand, when the path loss between the large cell base station 100 and the small cell base station 200a or the path loss between the large cell base station 100 and the radio terminal 300a is small, the small cell base station 200a transmits to the radio terminal 300a. It is determined that the interference control information is received. This is because when the path loss is small, it can be considered that the influence of interference exerted on the large cell base station 100 by the radio terminal 300a is large. The path loss can be calculated based on a report from the wireless terminal 300a.

(5.2) Modification 2
In this modification, the large cell base station 100, a list of identification information of the small cell base station repeater is required interference control information, and transmits included in the interference control information. Wireless terminal 300a, based on the list contained in the interference control information received from the large cell base station 100, to determine whether to relay to the small-cell base station 200a. According to this modified example, it is possible to specify a small cell base station to which interference control information should be transmitted from the large cell base station 100.

(5.3) Modification 3
In the embodiment described above, the case where the large cell base station 100 periodically transmits interference control information has been described. However, when the uplink interference level received by the large cell base station 100 is zero or low, transmission of interference control information may be omitted. For example, when the uplink interference level received by the large cell base station 100 exceeds a threshold, the interference control information is broadcast. Thereby, transmission of interference control information can be omitted, and the amount of consumption of the frequency band accompanying transmission of interference control information can be further reduced.

(5.4) Modification 4
In the embodiment described above, it has been described a radio communication system 1A relays wireless terminal 300a interference control information from the large cell base station 100 to the small-cell base station 200a. However, as shown in FIG. 10, the radio terminal 500 may relay the interference control information between the large cell base stations 100a and 100b. The radio terminal 500 is connected to the large cell base station 100b, receives the interference control information broadcast from the large cell base station 100a, and relays it to the large cell base station 100b. The wireless communication system 1B shown in FIG. 10 is effective when communication between base stations using a high-speed wired line is temporarily interrupted or when congestion occurs.

(5.5) Modification 5
In the above-described embodiment, the case where there is one small cell base station installed in the large cell LC has been described. However, as shown in FIG. 11, when there are a plurality of small cell base stations installed in the large cell LC, the above-described embodiment may be modified as follows. Large cell base station 100 transmits, including the information element addressed to the small cell base station 200a, and information elements addressed to the small cell base station 200b to the interference control information. Here, the information element is, for example, OI, HII, or newly defined information.

  The radio terminal 300a connected to the small cell base station 200a receives the interference control information broadcast from the large cell base station 100 and relays it to the small cell base station 200a. The radio terminal 300b connected to the small cell base station 200b receives the interference control information broadcast from the large cell base station 100 and relays it to the small cell base station 200b.

  The small cell base station 200a selects an information element addressed to the small cell base station 200a from the information elements included in the interference control information relayed from the radio terminal 300a, and based on the selected information element, the radio in the uplink The wireless communication of the terminal 300a is controlled. Similarly, the small cell base station 200b selects an information element addressed to the small cell base station 200b from the information elements included in the interference control information relayed from the radio terminal 300b, and based on the selected information element, It controls radio communication of the radio terminal 300b in the uplink.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  DESCRIPTION OF SYMBOLS 1A, 1B ... Wireless communication system, 100, 100a, 100b ... Large cell base station, 101 ... Antenna part, 110 ... Wireless communication part, 120 ... Control part, 130 ... Memory | storage part, 140 ... Wired communication part, 200a, 200b ... Small cell base station, 201 ... antenna unit, 210 ... wireless communication unit, 220 ... control unit, 230 ... storage unit, 240 ... wired communication unit, 300a ... wireless terminal, 300b ... wireless terminal, 301 ... antenna unit, 310 ... wireless Communication unit 320... Control unit 330 330 Storage unit 340 Battery 400 Wireless terminal 500 Wireless terminal

Claims (13)

A first radio base station, a second radio base station, and a radio terminal connected to the second radio base station;
The first radio base station wirelessly transmits interference control information for controlling the influence of interference received by the first radio base station in the uplink,
The wireless terminal, when receiving the interference control information from the first radio base station, and relays the interference control information received in the second radio base station,
The second radio base station is a radio communication system that controls radio communication of the radio terminal in an uplink based on the interference control information relayed from the radio terminal.   The radio communication system according to claim 1, wherein the first radio base station broadcasts the interference control information.   The radio communication system according to claim 2, wherein the first radio base station periodically broadcasts the interference control information. The first radio base station is a large cell base station forming a large cell;
The radio communication system according to any one of claims 1 to 3, wherein the second radio base station is a small cell base station that forms a small cell smaller than the large cell and can be installed in the large cell. .   The radio communication system according to claim 4, wherein the radio terminal attempts to receive the interference control information when it is confirmed that the second radio base station is the small cell base station.   The radio communication system according to any one of claims 1 to 4, wherein the radio terminal determines whether to receive the interference control information based on information received from the second radio base station.   5. The radio terminal according to claim 1, wherein the radio terminal determines whether to relay the interference control information to the second radio base station based on information received from the first radio base station. 6. The wireless communication system described.   The second radio base station changes at least one of transmission power or a used frequency band of the radio terminal in the uplink based on the interference control information relayed from the radio terminal. The wireless communication system according to one item. When there are a plurality of the second radio base stations, the first radio base station transmits a plurality of information elements addressed to each of the second radio base stations included in the interference control information,
Each of the second radio base stations selects an information element addressed to itself from the information elements included in the interference control information relayed from the radio terminal, and based on the selected information element, in the uplink The radio | wireless communications system as described in any one of Claims 1-8 which controls the radio | wireless communication of the said radio | wireless terminal. A generating unit that generates an interference control information is information for controlling the effect of interference by the own station receives to be transmitted to another radio base station in the uplink,
A radio base station comprising: a transmitter that wirelessly transmits the interference control information. A wireless terminal connected to a wireless base station,
A receiver that receives interference control information for controlling the influence of interference received by another radio base station in the uplink from the other radio base station;
A radio terminal comprising: a transmitter that transmits the received interference control information to the radio base station when the receiver receives the interference control information. A wireless base station to which a wireless terminal is connected,
A receiver for receiving the interference control information which the wireless terminal is relayed from the wireless terminal is information for controlling the effect of interference by other radio base station receives the uplink,
Based on the reception unit the interference control information received from the radio terminal, the radio base station and a control unit for controlling the radio communication of the wireless terminal in the uplink. A step in which a first radio base station wirelessly transmits interference control information for controlling an influence of interference received by the first radio base station in an uplink;
When a radio terminal connected to the second radio base station receives the interference control information from the first radio base station, relaying the received interference control information to the second radio base station;
A communication control method comprising: a step in which the second radio base station controls radio communication of the radio terminal in an uplink based on the interference control information relayed from the radio terminal.

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