JP2012114861A - Base station and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve service quality of a mobile communication system.SOLUTION: A base station 1A according to an embodiment comprises: a radio communication unit 100 configured to perform radio communication; a network communication unit 240 that receives control information about a communication state with a neighboring base station from a neighboring base station 1B by communication between base stations using an X2 interface; a measurement unit 210 that measures a radio signal received in the radio communication unit 100 from the neighboring base station 1B; and a control unit 220 that controls its own transmission parameter using the control information received in the network communication unit 240 by the communication between base stations in combination with the measurement result of the measurement unit 210.

Description

  The present invention relates to a base station and a communication control method capable of performing inter-base station communication with other base stations.

  In LTE (Long Term Evolution), the specifications of which are established by 3GPP (3rd Generation Partnership Project), a standardization organization for mobile communication systems, a connection called an X2 interface is set between adjacent base stations, and the X2 interface It is possible to perform inter-base station communication via By using the X2 interface, control information regarding the communication state of the base station can be transmitted and received between the base stations, and the radio communication parameters of the base station can be controlled, so that the service quality of the mobile communication system can be improved. .

  As an example of using the X2 interface, interference information is transmitted / received via the X2 interface, and scheduling of time-frequency resources (referred to as resource blocks) and transmission power control are performed based on the interference information. There is a way to control the interference. Such a method is called ICIC (Inter-Cell Interference Coordination). As shown in Non-Patent Document 1, interference information includes RNTP (Relative Narrowband Tx Power) indicating whether the downlink transmission power level is higher or lower than a threshold for each resource block, and the uplink interference level as a resource. An OI (Overload Indicator) or the like shown for each block is included.

  As another example of using the X2 interface, load information is transmitted / received via the X2 interface, and the communication area range (ie, coverage) of the base station is adjusted based on the load information. There is a way to try. Such a method is called MLB (Mobility Load Balancing), and is one of SON (Self Organizing Network) techniques for autonomous parameter adjustment. As shown in Non-Patent Document 1, the load information includes Radio Resource Status indicating the number of resource blocks used, Hardware Load Indicator indicating the hardware load of the base station, and the like.

3GPP TS36.423 “X2 application protocol (X2AP)”

  The communication control method using the X2 interface has the following problems. Specifically, control information (interference information and load information) received by one base station from another base station via the X2 interface is a set value or a measured value at the other base station. An error may be included in the control information due to a failure of another base station or the propagation environment in the vicinity of the one base station may not be sufficiently reflected.

  Therefore, as a result of the one base station controlling its own wireless communication parameters based on such control information, there is a possibility that interference between base stations will be further worsened, and the load between base stations may be further biased. is there. As described above, in the communication control method using the X2 interface, the service quality of the mobile communication system may be deteriorated.

  Therefore, an object of the present invention is to provide a base station and a communication control method that can improve the service quality of a mobile communication system.

  In order to solve the above-described problems, the present invention has the following features. First, the feature of the base station according to the present invention is that the control information regarding the communication state of the wireless communication unit (wireless communication unit 100) configured to perform wireless communication and the other base station (adjacent base station 1B) A network communication unit (network communication unit 240) that receives from the other base station by inter-base station communication, and a measurement unit (measurement unit 210) that measures the radio signal received from the other base station by the wireless communication unit And a control unit (control unit 220) for controlling the parameters of the radio communication unit by using the control information received by the network communication unit through the inter-base station communication and the result of the measurement by the measurement unit. And a gist of the above.

  According to such a feature, the base station uses not only the control information received from another base station by inter-base station communication but also the result of measurement on the radio signal received from the other base station, Controls the parameters of the unit (wireless communication parameters). By using the measurement result for such a radio signal, it is possible to perform better parameter control than parameter control based only on control information, and improve the service quality of the mobile communication system.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the network communication unit receives information indicating a transmission power level set in the other base station as the control information, The measurement unit measures a reception power level and a reception quality level of a radio signal received by the radio communication unit from the other base station, and the control unit determines the other power level from the reception power level measured by the measurement unit. Estimating the transmission power level of the base station, and controlling the parameter based on the reception quality level measured by the measurement unit, the estimated transmission power level, and the transmission power level indicated by the control information. The gist.

  Another feature of the base station according to the present invention is that, in the base station according to the feature described above, the control unit has a transmission power level indicated by the control information higher than the estimated transmission power level, and the measurement unit The gist is to control the parameter so as to expand the communication area range of the own station when the measured reception quality level is deteriorated below a predetermined level.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the network communication unit receives information indicating a transmission power level set in the other base station as the control information, The measurement unit measures a reception power level of a radio signal received from the other base station by the radio communication unit, and the control unit transmits the other base station from the reception power level measured by the measurement unit. The gist is to estimate a power level and control the transmission power level as the parameter according to a result of comparing the estimated transmission power level and the transmission power level indicated by the control information.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the control unit is configured such that the estimated transmission power level is lower than a transmission power level indicated by the control information, and the estimated transmission The gist is to control the radio communication unit so as to increase the transmission power level as the parameter when the difference between the power level and the transmission power level indicated by the control information exceeds a threshold value.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the network communication unit receives information indicating a downlink interference level of the other base station as the control information, and performs the measurement. The unit measures the reception quality level of the radio signal received from the other base station by the radio communication unit, and the control unit is based on the control information and the reception quality level measured by the measurement unit. The gist is to control the antenna tilt angle as the parameter.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the control unit has an interference level indicated by the control information exceeding a predetermined level, and the reception quality level measured by the measurement unit The gist of the invention is to control the wireless communication unit so as to increase the antenna tilt angle as the parameter when is degraded below a threshold value.

  Another feature of the base station according to the present invention is that, in the base station according to the feature described above, the control unit increases the antenna tilt angle as the parameter, and then the network communication unit receives from the other base station. The gist is to control the radio communication unit so as to reduce the transmission power level as the parameter when the interference level indicated by the new control information does not fall below a predetermined level.

  In another aspect of the base station according to the present invention, in the base station according to the above feature, the network communication unit receives information indicating a load level of the other base station as the control information, and the measurement unit includes: The wireless communication unit measures a reception power level of a radio signal received from the other base station, and the control unit estimates a transmission power level of the other base station from the reception power level measured by the measurement unit. The gist is to control the transmission power level as the parameter based on the load information and the estimated transmission power level.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the control unit has a load level indicated by the load information exceeding a predetermined level, and the estimated transmission power level is a predetermined level. The gist of the invention is to control the wireless communication unit so as to increase the transmission power level as the parameter when the value is lower than.

  Another feature of the base station according to the present invention is that, in the base station according to the feature described above, the control unit is configured such that the load level indicated by the load information exceeds a predetermined level and the transmission power indicated by the transmission power information. When both the level and the estimated transmission power level exceed a predetermined level, the network communication unit is controlled to request the other base station to lower the transmission power level, and the other base station The gist is to control the wireless communication unit so as to increase the transmission power level as the parameter after requesting the transmission power level to decrease.

  Another feature of the base station according to the present invention is that, in the base station according to the feature, the network communication unit receives information indicating the number of antennas used by the other base station as the control information, and the measurement unit The wireless communication unit measures the transmission speed of data included in the wireless signal received from the other base station, and the control unit measures the number of antennas indicated by the control information and the transmission measured by the measurement unit. The gist is to control the transmission power level as the parameter based on the speed.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the control unit has a transmission rate measured by the measurement unit, and the number of antennas indicated by the control information exceeds a predetermined number. The gist of the invention is to control the wireless communication unit so as to increase the transmission power level as the parameter when the speed is lower than a predetermined speed.

  Another feature of the base station according to the present invention is that, in the base station according to the above feature, the control unit increases the transmission power level as the parameter and increases the number of antennas used as the parameter. The gist is to control the wireless communication unit.

  A feature of the communication control method according to the present invention is that, in the base station according to the above feature, the first base station (base station 1A) transmits control information related to the communication state of the second base station (base station 1B) to the base station. Receiving from the second base station by inter-station communication, the first base station measuring a radio signal received from the second base station, and the first base station, The present invention includes the step of controlling the wireless communication parameters of the own station by using the control information received in the receiving step and the measurement result in the measuring step together.

  ADVANTAGE OF THE INVENTION According to this invention, the base station and communication control method which can improve the service quality of a mobile communication system can be provided.

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 base station which concerns on embodiment of this invention. It is a figure for demonstrating EVM. It is a block diagram which shows the structure of the frequency conversion part which concerns on embodiment of this invention. It is a block diagram which shows the structure of the acquisition part which concerns on embodiment of this invention. It is a figure for comparing and explaining each signal processing of an OFDMA system and an SC-FDMA system. It is a flowchart which shows the example of control of the base station which concerns on embodiment of this invention. It is a figure which shows a propagation loss model. It is a schematic system block diagram for demonstrating the communication control method which concerns on Examples 1-3 of this invention. It is a figure for demonstrating an antenna tilt angle. It is a flowchart for demonstrating the communication control method which concerns on Example 1 of this invention. It is a flowchart for demonstrating the communication control method which concerns on Example 2 of this invention. It is a flowchart for demonstrating the communication control method which concerns on Example 3 of this invention. It is a block diagram which shows the structure of the frequency conversion part which concerns on the modification 1 of embodiment of this invention. It is a block diagram which shows the structure of the acquisition part which concerns on the modification 2 of embodiment of this invention. It is a block diagram which shows the structure of the base station which concerns on the modification 3 of embodiment of this invention. It is a block diagram which shows the structure of the base station which concerns on the modification 4 of embodiment of this invention.

  An embodiment of a base station of the present invention will be described with reference to the drawings. Specifically, (1) Overview of wireless communication system, (2) Configuration of base station, (3) Control example of base station, (4) Action / effect of embodiment, (5) Example, (6) Other embodiments will be described. In the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Overview of Radio Communication System FIG. 1 is a schematic configuration diagram of a radio communication system 10 according to the present embodiment. The radio communication system 10 is configured 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, for example. It has a configuration based on.

  As shown in FIG. 1, in the radio communication system 10, the SC-FDMA scheme is applied to the uplink (hereinafter referred to as UL), and the OFDMA scheme is applied to the downlink (hereinafter referred to as DL). OFDMA is highly resistant to multipath interference and can flexibly handle a wide range of frequency bandwidths by changing the number of subcarriers. SC-FDMA can achieve low power consumption by reducing the peak power to average power ratio (PAPR) of the wireless terminal 2, and can reduce interference by orthogonalizing signals between users.

  In the radio communication system 10, the FDD scheme is applied as a duplex scheme. That is, the frequency band differs between UL and DL. A frequency band usable in the uplink is referred to as an “uplink frequency band”, and a frequency band usable in the downlink is referred to as a “downlink frequency band”. The upstream frequency band and the downstream frequency band are provided with a certain frequency interval.

  SON is applied to the wireless communication system 10. In the present embodiment, each base station 1 implements SON by measuring a radio signal from another base station 1.

  Each base station 1 is connected to a core network that is a wired communication network. The core network is provided by a telecommunications carrier and includes a router and the like. Each base station 1 can perform base station communication directly via the X2 interface which is a connection set in the core network.

(2) Configuration of Base Station Next, the configuration of the base station 1 will be described. FIG. 2 is a block diagram showing the configuration of the base station 1.

  As illustrated in FIG. 2, the base station 1 includes a wireless communication unit 100, a measurement unit 210, a control unit 220, a storage unit 230, and a network communication unit 240.

  The reception system of the base station 1 includes an antenna 110, a frequency converter 120 to which the output of the antenna 110 is input, a duplexer 130 to which the output of the frequency converter 120 is input, and a receiver to which the output of the duplexer 130 is input. 140, an OFDM demodulator 150 to which the output of the receiver 140 is input, an acquisition unit 160 to which the output of the OFDM demodulator 150 is input, and a frame processing unit 170 to which the output of the acquisition unit 160 is input.

  The transmission system of the base station 1 receives the transmission unit 180, the duplexer 130 to which the output of the transmission unit 180 is input, the frequency conversion unit 120 to which the output of the duplexer 130 is input, and the output of the frequency conversion unit 120. An antenna 110.

  The control system of the base station 1 stores information that is input / output between the measurement unit 210 to which the output of the acquisition unit 160 is input, the control unit 220 to which the output of the measurement unit 210 is input, and the control unit 220. A network communication unit 240 that inputs and outputs information between the control unit 220 and the control unit 220. The output of the control unit 220 is input to the frequency conversion unit 120 and the acquisition unit 160.

  First, the configuration of the receiving system will be described.

  The antenna 110 is for receiving and transmitting a radio signal. The radio signal received by the antenna 110 includes a signal component corresponding to an uplink radio signal (SC-FDMA signal transmitted by the radio terminal 2) and a downlink radio signal (OFDMA signal transmitted by another base station 1). And a signal component corresponding to.

  The frequency converter 120 is provided on the signal path between the antenna 110 and the duplexer 130. The frequency conversion unit 120 converts the signal component of the downlink frequency band (downlink carrier wave) included in the radio signal received by the antenna 110 into the signal component of the uplink frequency band (uplink carrier wave) according to the control signal from the control unit 220. Perform frequency conversion. The detailed configuration of the frequency conversion unit 120 will be described later.

  The duplexer 130 extracts an upstream frequency band signal component from the radio signal received by the antenna 110. When the frequency conversion unit 120 performs frequency conversion, the duplexer 130 eventually extracts a signal component in the downlink frequency band included in the radio signal received by the antenna 110. On the other hand, when the frequency conversion unit 120 does not perform frequency conversion, the duplexer 130 removes the signal component of the downlink frequency band included in the radio signal received by the antenna 110.

  The receiving unit 140 receives and processes the upstream frequency band signal component extracted by the duplexer 130. Here, the reception process means an amplification process, a down-conversion process to the baseband, and the like. Hereinafter, the signal component after reception processing is referred to as a reception signal.

  The OFDM demodulator 150 converts the received signal obtained by the receiver 140 from the time domain to the frequency domain and performs primary demodulation. For the conversion from the time domain to the frequency domain, fast Fourier transform (FFT) is used in the present embodiment, but discrete Fourier transform (DFT) or the like may be used. The time domain signal is converted into a plurality of subcarrier signals (frequency domain signals) by FFT. Primary demodulation is a process of demapping data symbols mapped to each subcarrier signal.

  The acquisition unit 160 acquires a data symbol that is being input from the OFDM demodulation unit 150 to the frame processing unit 170 in accordance with a control signal from the control unit 220. The detailed configuration of the frequency conversion unit 120 will be described later.

  The frame processing unit 170 is for performing signal processing dedicated to SC-FDMA. When the acquisition unit 160 does not acquire a data symbol being input from the OFDM demodulation unit 150 to the frame processing unit 170, the frame processing unit 170 performs OFDM processing. The data symbol obtained by the demodulator 150 is converted from the frequency domain to the time domain and the secondary demodulation is performed. The transform from the time domain to the frequency domain uses inverse discrete Fourier transform (IDFT) in this embodiment, but may use inverse fast Fourier transform (IFFT) or the like. IDFT converts the frequency domain signal into a time domain signal. Secondary demodulation is a process of generating a constellation and demapping the original data. For details of SC-FDMA signal processing, refer to, for example, 3GPP TS 36.211. The reception data output from the frame processing unit 170 is input to an error correction decoding unit (not shown).

  Next, the configuration of the transmission system will be described.

  Transmission data subjected to error correction coding is input to an OFDM modulation unit (not shown), mapped (modulated) to a plurality of subcarrier signals, converted to a time domain signal by IFFT, and a transmission signal (OFDMA signal) Generated. The transmission unit 180 performs amplification processing of the generated transmission signal and up-conversion processing to a high frequency band (RF band) to generate a radio signal. The generated radio signal is transmitted via the duplexer 130.

  Next, the configuration of the control system will be described.

  The network communication unit 240 receives information related to a radio signal transmitted from another base station 1 (adjacent base station) using inter-base station communication using the X2 interface. In the present embodiment, the network communication unit 240 reduces the ID of another base station 1, transmission power information indicating the transmission power level of a radio signal transmitted by the other base station 1, and inter-base station interference. Is received from the other base station 1 via the X2 interface. The interference information includes OI (Overload indication) that is information indicating the degree of interference that the other base station 1 receives in the uplink, and RNTP (Relative Narrowband Tx Power) that is information for regulating the downlink transmission power level. ).

  Storage unit 230 accumulates interference information received by network communication unit 240. The storage unit 230 stores various types of information used for control by the control unit 220.

  The measurement unit 210 performs measurement on the data symbols acquired by the acquisition unit 160. The measurement includes measurement of signal quality indicating the degree of signal quality, measurement of a transmission source ID included in the signal, and the like. In the present embodiment, the measurement unit 210 measures RSSI (Received Signal Strength Indicator) or RSRP (Received Signal Received Power) indicating the received power level. Here, RSRP is measured for each resource block. RSSI is measured collectively for all resource blocks. In the following embodiments, RSSI will be described as an example of received power measurement. Further, as shown in FIG. 3, the measurement unit 210 measures EVM (Error Vector Magnitude) indicating the magnitude of the amplitude error and the phase error between the data symbol and the reference point of the data symbol. Moreover, in this embodiment, the measurement part 210 performs the measurement in the resource block unit comprised using a some subcarrier.

  The EVM is determined by the following calculation formula, for example.

  Here, Z (k) is a demodulated signal (complex number having I and Q components), R (k) is a known ideal signal (complex number having I and Q components), and M is the number of subcarriers. .

  The control unit 220 controls the entire base station 1. For example, the control unit 220 outputs a control signal for operating the frequency conversion unit 120 and the acquisition unit 160 when the base station 1 does not need to perform wireless communication with the wireless terminal 2. The case where the base station 1 does not need to perform wireless communication with the wireless terminal 2 is, for example, the timing from the installation of the base station 1 to the start of full-scale operation, or midnight.

  Based on the RSSI obtained by the measurement unit 210 and the transmission power information received by the network communication unit 240, the control unit 220 determines transmission parameters when the transmission unit 180 performs transmission processing of the radio signal. In addition, the control unit 220 determines transmission parameters when the transmission unit 180 performs transmission processing of the radio signal based on the EVM obtained by the measurement unit 210 and the interference information received by the network communication unit 240. The transmission parameter means, for example, a transmission power level for each resource block. A specific example of control by the control unit 220 will be described later.

(2.1) Configuration of Frequency Conversion Unit Next, the configuration of the frequency conversion unit 120 will be described. FIG. 4 is a block diagram illustrating a configuration of the frequency conversion unit 120.

  As shown in FIG. 4, the frequency converter 120 has two signal paths P1 and P2. The frequency converter 120 is provided in the signal path P2 and the switch 121 provided at the branch point of the signal path P1 and the signal path P2, the switch 122 provided at the junction of the signal path P1 and the signal path P2. A filter 123 and a mixer 124, and a PLL circuit 125 connected to the mixer 124.

  The filter 123 extracts a downlink frequency band signal component from the radio signal received by the antenna 110. The PLL circuit 125 generates a conversion signal having a predetermined frequency. The mixer 124 converts the downstream frequency band signal component extracted by the filter 123 into the upstream frequency band signal component by mixing it with the conversion signal.

  The switch 121 and the switch 122 constitute a switching unit that switches whether the radio signal received by the antenna 110 passes through the filter 123 and the mixer 124 or bypasses. The control unit 220 controls the switch 121 and the switch 122 so that the radio signal received by the antenna 110 passes through the filter 123 and the mixer 124 at a timing when the base station 1 does not perform radio communication with the radio terminal 2. That is, control is performed so that the switch 121 and the switch 122 are switched to the signal path P2 side.

(2.2) Configuration of Acquisition Unit Next, the configuration of the acquisition unit 160 will be described. FIG. 5 is a block diagram illustrating a configuration of the acquisition unit 160.

  As illustrated in FIG. 5, the acquisition unit 160 includes a switch 161 and a switch 162 provided in each of two signal paths between the OFDM demodulation unit 150 and the frame processing unit 170, and each of the switch 161 and the switch 162. And a P / S converter 163 to which an output is input.

  The switch 161 and the switch 162 switch whether to input the data symbol output from the OFDM demodulator 150 to the P / S converter 163. The controller 220 switches the switch 161 and the switch 162 so that the data symbol output from the OFDM demodulator 150 is input to the P / S converter 163 at the timing when the base station 1 does not perform wireless communication with the wireless terminal 2. Control. P / S converter 163 converts the data symbol output from OFDM demodulator 150 from parallel to serial. The data symbol converted into serial is input to the measurement unit 210.

  Note that the OFDM demodulator 150 includes an FFT unit 151 and a primary demodulator 152 to which the output of the FFT unit 151 is input. The frame processing unit 170 includes an IDFT unit 171 to which the outputs of the switch 121 and the switch 122 are input, and a secondary demodulation unit 172 to which the output of the IDFT unit 171 is input.

  Here, the signal processing of the OFDMA system and the SC-FDMA system will be described in comparison with FIG.

  As shown in FIG. 6, in the OFDMA scheme, the transmission side performs S / P conversion on a data symbol generated by QPSK or the like, then modulates each subcarrier and performs IFFT to convert it into a time domain signal. Thereafter, at each symbol time, a cyclic prefix (CP) longer than the multipath delay time is inserted and transmitted. The receiving side can recover the data by removing the CP, applying FFT for each symbol length to convert it to a subcarrier signal, demodulating the data symbol from each subcarrier, and performing parallel-serial conversion.

  In SC-FDMA, after performing precoding processing (primary demodulation) in which a data symbol generated by QPSK or the like is converted into a frequency domain signal by DFT, the transmission side generates a transmission signal by processing similar to OFDMA. The receiving side generates data symbols from the received signal by the same process as OFDMA, and performs secondary demodulation (frame processing) to convert the frequency domain signal to a time domain signal by IDFT.

  Thus, it can be seen that SC-FDMA is obtained by adding frame processing to OFDM. Therefore, as illustrated in FIG. 5, the acquisition unit 160 performs P / S conversion on a signal demodulated after FFT (specifically, a signal demodulated after FFT and phase compensation), and transmits the result to the measurement unit 210. Here, it is assumed that the length of the wiring (Line A) from the switch 121 to the P / S converter 163 is equal to the length of the wiring (Line B) from the switch 122 to the P / S converter 163.

(3) Control Example of Base Station Next, a control example of the base station 1 will be described.

  When the base station 1 is installed for the purpose of expanding the service area, the base station 1 accumulates the ID and interference information of the adjacent base station received via the X2 interface. Then, after receiving the radio signal emitted by the adjacent base station and comparing it with the transmission power information obtained from the X2 interface, the transmission parameter capable of covering the cell edge of the service area of the own station is determined.

  In addition, for the purpose of maintenance by the installed base station 1, the neighboring base station parameters periodically obtained from the X2 interface are compared with the RSSI and EVM received by the own base station 1, and the surrounding environment changes. (For example, the construction of a high-rise building or the failure of a high-frequency amplifier of an adjacent base station) is detected, and the transmission parameter of the own station is changed. This enables call connection with a wireless terminal in a dead zone generated at the cell edge of an adjacent base station.

  FIG. 7 is a flowchart illustrating a control example of the base station 1.

  In step S <b> 11, the control unit 220 acquires transmission power information received by the network communication unit 240 and stored in the storage unit 230.

  In step S12, the control unit 220 operates the frequency conversion unit 120 and the acquisition unit 160, and controls the measurement unit 210 to measure RSSI. The RSSI measured by the measurement unit 210 is input to the control unit 220.

  The controller 220 corrects the measured RSSI distance. The distance correction will be described below with reference to the propagation loss model shown in FIG.

  Radio waves attenuate in free space in inverse proportion to the square of the distance from the source. Since the distance d between the adjacent base station and the own station can be obtained from the adjacent list stored in the storage unit 230 in advance, if Pr = RSSI, transmission of the adjacent base station from the Friis' transmission equation The power level Pt can be obtained.

P _r / P _t = G _t G _r (4πd / λ) ² (2)

  Here, Pr: reception power level [dBm], Pt: transmission power level [dBm], Gt: transmission antenna gain [dB], Gr: reception antenna gain [dB], λ: wavelength [m], d: between transmission and reception Is the distance [m].

  In this embodiment, obtaining the transmission power level at the antenna end of the adjacent base station from RSSI is defined as RSSI distance correction, and considering the influence of the structure on the ground surface (attenuation in inverse proportion to the 3.5th power of the distance) The transmission power level of the adjacent base station is calculated from the following formula.

 Pr = Pt + Gt-20log4π + 35log (λ / d) + Gr (3)

  In step S13, the control unit 220 compares the transmission power information acquired from the storage unit 230 with the RSSI after distance correction. When the transmission power information is larger than the RSSI after the distance correction, it means that there is a problem with the power amplifier of the adjacent base station or that there is a building or the like between the adjacent base station. If the transmission power information is larger than the RSSI after distance correction, the process proceeds to step S14.

  In step S14, the control unit 220 keeps the frequency conversion unit 120 and the acquisition unit 160 operated, and controls the measurement unit 210 to measure EVM. The EVM measured by the measurement unit 210 is input to the control unit 220.

  In step S <b> 15, the control unit 220 acquires the EVM threshold value from the storage unit 230.

  In step S <b> 16, the control unit 220 compares the EVM measured by the measurement unit 210 with the threshold acquired from the storage unit 230. If the EVM measured by the measurement unit 210 is larger than the threshold acquired from the storage unit 230, the process proceeds to step S17.

  In step S17, the control unit 220 performs SON control, that is, determination of transmission parameters. For example, the control unit 220 determines transmission parameters that can cover the cell edge of the service area of the local station. Or the control part 220 determines the transmission parameter which can cover the dead zone which arose in the cell edge of an adjacent base station.

(4) Operation / Effect of Embodiment As described above, the base station 1 according to this embodiment transmits the signal component of the downlink frequency band included in the radio signal received by the antenna 110 (that is, the adjacent base station transmits). The wireless signal component) is converted into an upstream frequency band signal component and input to the duplexer 130. Thereby, the component of the radio signal transmitted by the adjacent base station can pass through the duplexer 130, and the measurement of the component of the radio signal transmitted by the adjacent base station can be performed. Therefore, in the wireless communication system 10 to which the FDD scheme is applied, the own base station 1 can perform measurement on the wireless signal transmitted by the adjacent base station.

  Further, according to the present embodiment, paying attention to the fact that the signal processing in the SC-FDMA system is obtained by adding frame processing to the signal processing in the OFDMA system, the OFDM demodulator 150 to the frame processor 170 Measurement is performed on data symbols that are being input to the. As a result, it is possible to perform measurement on data symbols corresponding to OFDMA radio signals (that is, radio signals transmitted by adjacent base stations). Therefore, in the radio communication system 10 in which the SC-FDMA scheme is applied to the UL and the OFDMA scheme is applied to the DL, the own base station 1 can perform measurement on the radio signal transmitted by the adjacent base station. In addition, by performing measurement on the state converted to the frequency domain, measurement in subcarrier units or resource block units is possible.

  In the present embodiment, since the measurement by the measurement unit 210 is performed at a timing at which the base station 1 does not perform wireless communication with the wireless terminal 2, the operation of the adjacent base station is prevented without interfering with wireless communication with the wireless terminal 2. The situation can be grasped. In addition, it is possible to grasp the operation status of adjacent base stations even during a period from when the base station 1 is installed until full operation.

  As described above, this embodiment detects changes in the surrounding environment when a large change occurs in the surrounding buildings or when an abnormality occurs in the high-frequency amplifier (PA) of an adjacent base station. The operation state of the adjacent base station can be detected only by the base station 1.

(5) Example In the above-described embodiment, the base station 1 receives transmission power information indicating the transmission power level set in the adjacent base station by inter-base station communication, and the radio signal received from the adjacent base station. The received power level (for example, RSSI) and the received quality level (for example, EVM) are measured, the transmission power level of the adjacent base station is estimated from the measured received power level, and the measured received quality level and the estimated The transmission parameter of the own station is controlled based on the transmission power level and the transmission power level indicated by the transmission power information. Specifically, the base station 1 determines that the transmission power level indicated by the transmission power information is higher than the estimated transmission power level and the measured reception quality level is deteriorated below a predetermined level (threshold). The transmission parameters were controlled to expand the communication area range of the local station.

  Hereinafter, Examples 1 to 3 of the communication control method different from the communication control method according to the above-described embodiment will be described.

  FIG. 9 is a schematic system configuration diagram for explaining a communication control method according to the first to third embodiments.

  As shown in FIG. 9, the base station 1A communicates control information related to the communication state of the adjacent base station 1B with the wireless communication unit 100 configured to perform wireless communication by inter-base station communication using the X2 interface. A network communication unit 240 received from the base station 1B, a measurement unit 210 that measures the radio signal received by the wireless communication unit 100 from the adjacent base station 1B, and control information received by the network communication unit 240 through inter-base station communication; It has the control part 220 which controls the transmission parameter of a self-station together using the measurement result by the measurement part 210, and the memory | storage part 230 which memorize | stores the information used for control by the control part 220. FIG.

  As described above, in the communication control method according to the first to third embodiments, the base station 1A not only controls the control information received from the adjacent base station 1B by inter-base station communication but also the radio signal received from the adjacent base station 1B. The transmission parameter of the own station is controlled using the measurement result. By using the result of the measurement for the radio signal, it is possible to perform parameter control better than the radio communication parameter control of the own station based only on the control information.

(5.1) Example 1
Hereinafter, for Example 1, (5.1.1) Outline of Example 1, (5.1.2) Transmission power control flow 1, (5.1.3) Antenna tilt angle control flow, (5.1) .4) Transmission power control flow 2, (5.1.5) Specific example of parameter control, (5.1.6) The effects of the first embodiment will be described in this order.

(5.1.1) Overview of First Embodiment In the base station 1A according to the first embodiment, the network communication unit 240 receives and measures transmission power information indicating the transmission power level set in the adjacent base station 1B. Unit 210 measures the RSSI of the radio signal received by radio communication unit 100 from adjacent base station 1B, and control unit 220 estimates the transmission power level of adjacent base station 1B from the RSSI measured by measurement unit 210, and The transmission power level as a transmission parameter of the own station is controlled according to the result of comparing the estimated transmission power level and the transmission power level indicated by the transmission power information. Here, transmission power information corresponds to control information, and RSSI corresponds to a received power level. Note that the same method as the above-described embodiment can be used as a method of estimating the transmission power level of the adjacent base station 1B. As the transmission power information, RNTP (see 3GPP TS36.423) may be used, or a new message or information element (IE) may be used.

  Further, in the base station 1A according to the first embodiment, the network communication unit 240 receives interference information indicating the DL interference level of the adjacent base station 1B, and the measurement unit 210 receives the wireless communication unit 100 from the adjacent base station 1B. The EVM of the received radio signal is measured, and the control unit 220 controls the antenna tilt angle as a transmission parameter of the own station based on the interference information and the EVM measured by the measurement unit 210. Interference information corresponds to control information, and EVM corresponds to a reception quality level. As interference information indicating the DL interference level, a new message or information element (IE) is used.

  Here, as shown in FIG. 10, the antenna tilt angle is an angle of the directivity direction of the antenna in the vertical plane with respect to the horizontal direction. The larger the antenna tilt angle, the narrower the radio wave reachable range of the antenna. Accordingly, the smaller the antenna tilt angle, the wider the radio wave reachable range of the antenna. The initial values of the antenna tilt angles of the base station 1A and the adjacent base station 1B are the distance d between the base station 1A and the adjacent base station 1B, the respective antenna heights h of the base station 1A and the adjacent base station 1B, and It is set based on. The antenna tilt angle can be changed by adjusting the feeding phase for a plurality of antenna elements constituting the antenna 110 (see FIG. 2) of the base station 1A.

(5.1.2) Transmission power control flow 1
FIG. 11A is a flowchart illustrating the transmission power control flow 1 of the base station 1A according to the first embodiment.

  As illustrated in FIG. 11A, in step S101, the control unit 220 acquires the transmission power level indicated by the transmission power information received from the adjacent base station 1B by the network communication unit 240 via the X2 interface.

  In step S102, the control unit 220 acquires the RSSI measured by the measurement unit 210 for the radio signal received by the radio communication unit 100 from the adjacent base station 1B.

  In step S103, the control unit 220 estimates the transmission power level of the adjacent base station 1B from the RSSI acquired in step S102.

  In step S104, the control unit 220 compares the result of subtracting the transmission power level estimated in step S103 from the transmission power level acquired in step S101 with a threshold (for example, 6 dB). When the result of subtracting the transmission power level estimated in step S103 from the transmission power level acquired in step S101 is higher than a threshold (for example, 6 dB), the control unit 220 advances the process to step S105.

  In step S105, the control unit 220 controls the wireless communication unit 100 so as to increase the transmission power level of the local station.

(5.1.3) Antenna Tilt Angle Control Flow FIG. 11B is a flowchart illustrating the antenna tilt angle control flow of the base station 1A according to the first embodiment.

  As illustrated in FIG. 11B, in step S201, the control unit 220 acquires the interference level indicated by the interference information received by the network communication unit 240 from the adjacent base station 1B via the X2 interface.

  In step S202, the control unit 220 acquires the EVM measured by the measurement unit 210 with respect to the radio signal received by the radio communication unit 100 from the adjacent base station 1B.

  In step S203, the control unit 220 compares the interference level acquired in step S201 with a predetermined level, and compares the EVM acquired in step S202 with a predetermined level (threshold). When the interference level acquired in step S201 exceeds the predetermined level and the EVM acquired in step S202 exceeds the predetermined level (threshold), the control unit 220 advances the process to step S204. EVM means that the larger the value, the worse the reception quality.

  In step S204, the control unit 220 controls the wireless communication unit 100 so as to increase the antenna tilt angle of the local station.

  In step S205, the control unit 220 acquires the interference level indicated by the new interference information received by the network communication unit 240 from the adjacent base station 1B via the X2 interface.

  In step S206, the control unit 220 compares the interference level acquired in step S205 with a predetermined level. When the interference level acquired in step S205 exceeds the predetermined level, the control unit 220 advances the process to the transmission power control flow 2.

(5.1.4) Transmission power control flow 2
FIG. 11C is a flowchart illustrating the transmission power control flow 1 of the base station 1A according to the first embodiment.

  As shown in FIG.11 (c), in step S301, the control part 220 controls the radio | wireless communication part 100 so that the transmission power level of an own station may be reduced.

(5.1.5) Specific Example of Parameter Control Next, a specific example of parameter control according to the first embodiment will be described. Tables 1 and 2 are tables for explaining specific examples of parameter control according to the first embodiment.

  As shown in Table 1, the transmission power level and the antenna tilt angle of the base station 1A are respectively controlled by the transmission power control flow 1 and the antenna tilt angle control flow described above. In Table 1, since the adjacent base stations eNB1 and eNB2 have interference information (that is, the interference level is high) and EVM is high (that is, the reception quality level is low), the base station 1A has its own antenna tilt angle. Increase Regarding the adjacent base stations eNB1 and eNB2, since the estimated transmission power level is significantly lower than the transmission power level indicated by the transmission power information, the base station 1A increases its transmission power level.

  As shown in Table 2, according to the transmission power control flow 2 described above, the transmission power level of the base station 1A is controlled after increasing the antenna tilt angle of the base station 1A. In Table 2, for the adjacent base stations eNB1 and eNB2, there is interference information (that is, the interference level is high) even after the antenna tilt angle of the base station 1A is increased. Reduce the level.

(5.1.6) Effects of First Embodiment As described above, according to the first embodiment, the control unit 220 of the base station 1A determines the transmission power level at which the estimated transmission power level is indicated by the transmission power information. When the difference between the estimated transmission power level and the transmission power level indicated by the transmission power information exceeds the threshold, the radio communication unit 100 is controlled to increase the transmission power level of the own station. If the estimated transmission power level is significantly lower than the transmission power level indicated by the transmission power information, it means that the actual transmission power level is lower than the set value of the transmission power level in the adjacent base station 1B. Therefore, it can be considered that a failure or the like has occurred in the wireless transmission function of the adjacent base station 1B. Accordingly, in such a case, by increasing the transmission power level of the own station, the communication area range of the adjacent base station 1B can be supplemented, and the service quality of the mobile communication system can be improved.

  In addition, the control unit 220 of the base station 1A determines that the antenna tilt as a transmission parameter of the own station when the interference level indicated by the interference information exceeds a predetermined level and the EVM measured by the measurement unit 210 is degraded. The wireless communication unit 100 is controlled to increase the angle. When the interference level indicated by the interference information exceeds a predetermined level and the EVM measured by the measurement unit 210 is deteriorated, interference between base stations occurs between the own station and the adjacent base station 1B. Can be considered. Therefore, in such a case, by increasing the antenna tilt angle of the own station, the interference level given to the adjacent base station 1B can be reduced, so that the service quality of the mobile communication system can be improved.

  After the control unit 220 of the base station 1A increases the antenna tilt angle as a transmission parameter of the own station, the interference level indicated by the new interference information received by the network communication unit 240 from the adjacent base station 1B falls below a predetermined level. If not, the wireless communication unit 100 is controlled to reduce the transmission power level of the local station. If the interference level applied to the adjacent base station 1B does not sufficiently decrease even after the antenna tilt angle is increased, the interference level applied to the adjacent base station 1B is further reduced by reducing the transmission power level of the own station. Therefore, the service quality of the mobile communication system can be improved.

(5.2) Example 2
Hereinafter, with regard to the second embodiment, (5.2.1) Overview of the second embodiment, (5.2.2) Transmission power control flow, (5.2.3) Specific example of parameter control, (5.2. 4) Description will be given in the order of the effects of the second embodiment.

(5.2.1) Overview of Second Embodiment In the base station 1A according to the second embodiment, the network communication unit 240 receives load information indicating the load level of the adjacent base station 1B, and the measurement unit 210 performs wireless communication. Unit 100 measures the RSSI of the radio signal received from adjacent base station 1B, and control unit 220 estimates the transmission power level of adjacent base station 1B from the RSSI measured by measurement unit 210, and estimates the load information and the estimated value. Based on the transmission power level, the transmission power level as a transmission parameter of the own station is controlled. Here, the interference information corresponds to control information, and the RSSI corresponds to the received power level. As the load information, the above-described Radio Resource Status, Hardware Load Indicator, etc. (see 3GPP TS36.423) can be used.

(5.2.2) Transmission Power Control Flow FIG. 12 is a flowchart illustrating a transmission power control flow of the base station 1A according to the second embodiment.

  As shown in FIG. 12, in step S401, the control unit 220 acquires the load level indicated by the load information received by the network communication unit 240 from the adjacent base station 1B via the X2 interface.

  In step S402, the control unit 220 compares the load level acquired in step S401 with a predetermined level. When the load level acquired in step S401 exceeds the predetermined level, the control unit 220 advances the process to step S403.

  In step S403, the control unit 220 acquires the transmission power level indicated by the transmission power information received by the network communication unit 240 from the adjacent base station 1B via the X2 interface. Moreover, the control part 220 acquires RSSI which the measurement part 210 measured with respect to the radio signal which the radio | wireless communication part 100 received from the adjacent base station 1B.

  In step S404, the control unit 220 estimates the transmission power level of the adjacent base station 1B from the RSSI acquired in step S403.

  In step S405, the control unit 220 compares each of the transmission power level acquired in step S403 and the transmission power level estimated in step S404 with a predetermined level (threshold). If each of the transmission power level acquired in step S403 and the transmission power level estimated in step S404 is below a predetermined level (threshold), the control unit 220 advances the process to step S407. On the other hand, when at least one of the transmission power level acquired in step S403 and the transmission power level estimated in step S404 exceeds a predetermined level (threshold), the control unit 220 advances the process to step S406.

  In step S406, the control unit 220 controls the network communication unit 240 to transmit a transmission power level reduction request to the adjacent base station 1B. When the network communication unit 240 receives an affirmative response to the decrease request, the control unit 220 advances the process to step S407.

  In step S407, the control unit 220 controls the wireless communication unit 100 so as to increase the transmission power level of the local station.

(5.2.3) Specific Example of Parameter Control Next, a specific example of parameter control according to the second embodiment will be described. Table 3 is a table for explaining a specific example of parameter control according to the second embodiment.

  As shown in Table 3, the transmission power level of the base station 1A is controlled by the transmission power control flow according to the present embodiment. In Table 3, since the load level is high and the transmission power level is low for the adjacent base station eNB4, the base station 1A increases the transmission power level. In Table 3, the number of radio terminals (UEs) accommodated by adjacent base stations is used as load information.

(5.2.4) Effects of Second Embodiment As described above, according to the second embodiment, the control unit 220 determines that the load level indicated by the load information exceeds a predetermined level and the estimated transmission power level. Is less than a predetermined level, the wireless communication unit 100 is controlled to increase the transmission power level of the local station. In this way, when the load level of the adjacent base station 1B is high and the transmission power level of the adjacent base station 1B is low, by increasing the transmission power level of the own station, the communication area range of the own station is expanded, The load level of the adjacent base station 1B can be reduced. Here, in a state where the transmission power level of the adjacent base station 1B is high, if the transmission power level of the own station is increased, interference between base stations is caused, so it is confirmed that the transmission power level of the adjacent base station 1B is low Then, increase the transmission power level of your station. As a result, it is possible to reduce the load level of the adjacent base station 1B while suppressing the occurrence of inter-base station interference.

  Further, the control unit 220 determines that the adjacent base station when the load level indicated by the load information exceeds a predetermined level and both the transmission power level indicated by the transmission power information and the estimated transmission power level exceed the predetermined level. After controlling the network communication unit 240 to request the transmission power level to be lowered from 1B and requesting the neighboring base station 1B to lower the transmission power level, the transmission power level as a transmission parameter of the own station is set. The wireless communication unit 100 is controlled to be raised. Thereby, when the load level of the adjacent base station 1B is high and the transmission power level of the adjacent base station 1B is high, the transmission power level of the own base station is increased after the transmission power level of the adjacent base station 1B is decreased. Thus, the load level of the adjacent base station 1B can be reduced while suppressing the occurrence of inter-base station interference.

(5.3) Example 3
Hereinafter, the third embodiment will be described in the order of (5.3.1) Outline of the third embodiment, (5.3.2) Transmission power control flow, and (5.3.3) Effects of the third embodiment.

(5.3.1) Overview of Embodiment 3 In the base station 1A according to Embodiment 2, the network communication unit 240 receives the antenna number information indicating the number of used antennas (number of used antenna ports) of the adjacent base station 1B. The measurement unit 210 measures the transmission rate of data included in the radio signal received by the radio communication unit 100 from the adjacent base station 1B, and the control unit 220 determines the number of antennas indicated by the antenna number information and the measurement unit 210. Based on the measured data transmission rate, the transmission power level as a transmission parameter of the own station is controlled. In the second embodiment, it is assumed that each base station performs MIMO transmission, and the higher the number of antennas used, the higher the data transmission rate can be realized.

(5.3.2) Transmission Power Control Flow FIG. 13 is a flowchart illustrating a transmission power control flow of the base station 1A according to the third embodiment.

  As illustrated in FIG. 13, in step S501, the control unit 220 acquires the number of antennas indicated by the number-of-antenna information received by the network communication unit 240 from the adjacent base station 1B via the X2 interface.

  In step S502, the control unit 220 acquires the data transmission rate measured by the measurement unit 210 with respect to the radio signal received by the radio communication unit 100 from the adjacent base station 1B.

  In step S503, the control unit 220 compares the number of antennas acquired in step S501 with a predetermined number (threshold), and compares the data transmission rate acquired in step S502 with a predetermined speed (threshold). When the number of antennas acquired in step S501 exceeds a predetermined number (threshold) and the data transmission rate acquired in step S502 is lower than the predetermined speed (threshold), the control unit 220 advances the process to step S504.

  In step S504, the control unit 220 controls the wireless communication unit 100 so as to increase the transmission power level of the local station. In addition, when there is a margin in the number of used antennas of the own station, that is, when there are unused antennas, the control unit 220 controls the radio communication unit 100 so as to increase the number of used antennas of the own station.

(5.3.3) Effect of Embodiment 3 As described above, according to Embodiment 3, the control unit 220 has the number of antennas indicated by the control information exceeding a predetermined number, and is measured by the measurement unit 210. When the transmitted data transmission rate is lower than the predetermined rate, the wireless communication unit 100 is controlled to increase the transmission power level of the own station. If the adjacent base station 1B does not realize a high transmission rate despite the large number of antennas used by the adjacent base station 1B, it may be considered that a failure or the like has occurred in the wireless transmission function of the adjacent base station 1B. it can. Accordingly, in such a case, by increasing the transmission power level of the own station, the communication area range of the adjacent base station 1B can be supplemented, and the service quality of the mobile communication system can be improved.

  In addition, the control unit 220 controls the wireless communication unit 100 so as to increase the transmission power level of the own station and to increase the number of antennas used by the own station. Thereby, while complementing the communication area range of the adjacent base station 1B, the transmission rate can be improved so as to cover the complemented portion, and the service quality of the mobile communication system can be improved.

(6) Other Embodiments Although the present invention has been described with reference to embodiments and examples, 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.

(6.1) Modification 1
In the above-described embodiments and examples, the base station 1 has one antenna 110. However, the base station 1 may be configured to support a multi-antenna technique such as MIMO (Multiple Input Multiple Output). FIG. 14 shows a configuration corresponding to 2 × 2 MIMO in which each of the transmission side and the reception side uses two antennas.

  As shown in FIG. 14, the base station 1 has two antennas 110a and 110b and two duplexers 130a and 130b, and a frequency conversion unit is provided on the signal path between the antennas 110a and 110b and the duplexers 130a and 130b. 120 is provided. The frequency conversion unit 120 has the same circuit configuration as that of the above-described embodiment for each antenna, but can share the PLL circuit 125.

(6.2) Modification 2
In the embodiment and the example described above, the acquisition unit 160 acquires the signal (data symbol) after the primary demodulation by the OFDM demodulation unit 150, but may be configured to acquire the signal before the primary demodulation.

  FIG. 15 is a block diagram illustrating a configuration of the acquisition unit 160 according to the present modification. As illustrated in FIG. 15, the acquisition unit 160 includes a switch 165 provided in a signal path between the FFT unit 151 and the primary demodulation unit 152 of the OFDM demodulation unit 150. The switch 165 switches whether to input a frequency domain signal output from the FFT unit 151 (specifically, a signal subjected to P / S conversion after conversion to the frequency domain) to the measurement unit 210. The control unit 220 controls the switch 165 so that the frequency domain signal output from the FFT unit 151 is input to the measurement unit 210 at a timing when the base station 1 does not perform wireless communication with the wireless terminal 2.

  According to such a configuration, it is possible to measure the received power level in units of subcarriers with a simple circuit configuration.

(6.3) Modification 3
In the above-described embodiments and examples, the radio communication system 10 in which the SC-FDMA scheme is applied to the UL and the OFDMA scheme is applied to the DL has been described. However, the frequency conversion unit 120 is an FDD radio communication system. If present, the present invention can be applied to a wireless communication system employing another wireless access method.

  FIG. 16 is a configuration example of the base station 1 used in an FDD wireless communication system that employs an arbitrary wireless access method. As illustrated in FIG. 16, the base station 1 according to the present modification is different from the above-described embodiment in that the measurement unit 210 performs measurement on a signal received and processed by the reception unit 140. For example, since RSSI can be measured at the stage of the receiver 140, such a configuration can also be employed.

(6.4) Modification 4
In the above-described embodiments and examples, the FDD mode LTE system has been described. However, the present invention can be applied to a TDD mode LTE system. In the LTE system in TDD mode, the SC-FDMA scheme is applied to the UL and the OFDMA scheme is applied to the DL, but the duplex scheme is TDD.

  FIG. 17 is a block diagram showing the configuration of the base station 1 according to this modification. As illustrated in FIG. 17, the base station 1 according to this modification does not include the frequency conversion unit 120 according to the above-described embodiment. Further, in place of the duplexer 130, a switch circuit 130 'for switching between transmission and reception in a time division manner is provided.

(6.5) Modification 5
In the embodiments and examples described above, the base station 1 is assumed to be a macro cell base station that forms a large cell. However, the base station 1 is not limited to a macro cell base station, and a femto cell base station or pico cell base that forms a small cell. The present invention can be applied to a station.

  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 1,1A ... Base station, 1B ... Neighboring base station, 2 ... Wireless terminal, 10 ... Wireless communication system, 100 ... Wireless communication part, 110, 110a, 110b ... Antenna, 120 ... Frequency conversion part, 121, 122 ... Switch, DESCRIPTION OF SYMBOLS 123 ... Filter, 124 ... Mixer, 125 ... PLL circuit, 130 ... Switch circuit, 130, 130a, 130b ... Duplexer, 140 ... Reception part, 150 ... OFDM demodulation part, 151 ... FFT part, 152 ... Primary demodulation part, 160 ... Acquiring unit 161 ... switch 162 ... switch 163 ... P / S converter 165 ... switch 170 ... frame processing unit 171 ... IDFT unit 172 ... secondary demodulation unit 180 ... transmission unit 210 ... measurement unit , 220 ... control unit, 230 ... storage unit, 240 ... network communication unit

Claims (15)

A wireless communication unit configured to perform wireless communication;
A network communication unit that receives control information related to the communication state of another base station from the other base station by inter-base station communication; and
A measurement unit for measuring the radio signal received from the other base station by the radio communication unit;
The control unit that controls the parameters of the wireless communication unit by using the control information received by the network communication unit through the communication between the base stations and the measurement result by the measurement unit;
A base station comprising: The network communication unit receives information indicating a transmission power level set in the other base station as the control information,
The measurement unit measures a reception power level and a reception quality level of a radio signal received from the other base station by the radio communication unit;
The controller is
Estimating the transmission power level of the other base station from the reception power level measured by the measurement unit,
The base station according to claim 1, wherein the parameter is controlled based on a reception quality level measured by the measurement unit, the estimated transmission power level, and a transmission power level indicated by the control information.   When the transmission power level indicated by the control information exceeds the estimated transmission power level and the reception quality level measured by the measurement unit is deteriorated below a predetermined level, the control unit The base station according to claim 2, wherein the parameter is controlled to expand a communication area range. The network communication unit receives information indicating a transmission power level set in the other base station as the control information,
The measurement unit measures the reception power level of a radio signal received from the other base station by the radio communication unit,
The controller is
Estimating the transmission power level of the other base station from the reception power level measured by the measurement unit,
The base station according to claim 1, wherein the transmission power level as the parameter is controlled according to a result of comparing the estimated transmission power level with a transmission power level indicated by the control information.   When the estimated transmission power level is lower than the transmission power level indicated by the control information, and the difference between the estimated transmission power level and the transmission power level indicated by the control information exceeds a threshold value The base station according to claim 4, wherein the wireless communication unit is controlled to increase a transmission power level as the parameter. The network communication unit receives information indicating a downlink interference level of the other base station as the control information,
The measurement unit measures a reception quality level of a radio signal received from the other base station by the radio communication unit;
The base station according to claim 1, wherein the control unit controls an antenna tilt angle as the parameter based on the control information and a reception quality level measured by the measurement unit.   The control unit increases the antenna tilt angle as the parameter when the interference level indicated by the control information exceeds a predetermined level and the reception quality level measured by the measurement unit is deteriorated below a threshold value. The base station according to claim 6, wherein the radio communication unit is controlled to do so.   The control unit, after increasing the antenna tilt angle as the parameter, when the interference level indicated by new control information received by the network communication unit from the other base station does not fall below a predetermined level, the parameter The base station according to claim 7, wherein the radio communication unit is controlled so as to reduce a transmission power level. The network communication unit receives information indicating the load level of the other base station as the control information,
The measurement unit measures the reception power level of a radio signal received from the other base station by the radio communication unit,
The controller is
Estimating the transmission power level of the other base station from the reception power level measured by the measurement unit,
The base station according to claim 1, wherein a transmission power level as the parameter is controlled based on the load information and the estimated transmission power level.   The control unit is configured to increase the transmission power level as the parameter when a load level indicated by the load information exceeds a predetermined level and the estimated transmission power level is lower than a predetermined level. The base station according to claim 9 which controls a unit. The controller is
When the load level indicated by the load information exceeds a predetermined level, and both the transmission power level indicated by the transmission power information and the estimated transmission power level exceed the predetermined level, the other base station Controlling the network communication unit to request a decrease in the transmission power level,
The base station according to claim 9 or 10, wherein the wireless communication unit is controlled to increase the transmission power level as the parameter after requesting the other base station to decrease the transmission power level. The network communication unit receives information indicating the number of antennas used by the other base station as the control information,
The measurement unit measures a transmission rate of data included in a radio signal received from the other base station by the radio communication unit;
The base station according to claim 1, wherein the control unit controls the transmission power level as the parameter based on the number of antennas indicated by the control information and the transmission rate measured by the measurement unit.   The control unit increases the transmission power level as the parameter when the number of antennas indicated by the control information exceeds a predetermined number and the transmission rate measured by the measurement unit is lower than the predetermined rate. The base station according to claim 12, which controls the radio communication unit.   The base station according to claim 13, wherein the control unit controls the radio communication unit to increase a transmission power level as the parameter and to increase the number of antennas used as the parameter. A first base station receiving control information relating to a communication state of a second base station from the second base station by inter-base station communication;
The first base station performing measurements on a radio signal received from the second base station;
The first base station uses the control information received in the receiving step and the result of the measurement in the step of performing the measurement to control radio communication parameters of the own station;
Including a communication control method.

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