JP2019022044A - Control device, radio communication device, and calibration method - Google Patents

Abstract

To prevent failures due to reception of a neighbor cell calibration signal in over power.SOLUTION: A method includes: an adjustment part for directing implementation of a calibration process to a master radio communication device, the process includes the master radio communication device which is one of radio communication devices in a first cell transmits a calibration signal, a slave radio communication device other than the master radio communication device within the first cell receives the calibration signal, and adjustment of transmission timing for a signal transmitted by the slave radio communication device based on the received calibration signal; an acquisition part for acquiring reception quality information regarding reception quality of the calibration signal in a radio communication device within a second cell when the radio communication device within the second cell receives the calibration signal transmitted from the master radio communication device with higher power than a first threshold value; and a control part for selecting a master radio communication device within radio communication devices within the first cell based on the acquired reception quality information.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a control device, a wireless communication device, and a calibration method.

  In a radio communication system, a plurality of radio base stations (RRH: Remote Radio Head) may constitute a cell, and a plurality of RRHs may perform cooperative transmission to improve radio communication quality. The plurality of RRHs realize cooperative transmission by transmitting radio waves intensively in the direction of the terminal device. In coordinated transmission, it is essential that the phase between the antennas in RRH matches, and calibration is performed as a method for matching the phase.

  In the calibration, for example, a plurality of RRHs are classified into RRHs that serve as phase references (hereinafter referred to as master RRHs) and RRHs that align phases with the master RRHs (hereinafter referred to as slave RRHs). Then, the slave RRH receives a calibration signal for adjusting the phase from the master RRH and corrects the phase.

  Techniques relating to calibration are described in Patent Documents 1 and 2 below.

JP-A-2015-053584 JP-T-2006-518093

  However, in calibration, for example, the calibration signal transmitted by the master RRH of the own cell may reach the RRH of the adjacent cell. When the RRH of an adjacent cell receives a calibration signal with power (overpower) exceeding the upper limit of received power that can be received, it causes a failure.

  Therefore, one disclosure is to provide a control device, a wireless communication device, and a calibration method for preventing a failure caused by receiving calibration signals in adjacent cells with overpower.

  In one aspect, a control device that controls a wireless communication device that constitutes a first cell, wherein a master wireless communication device that is one of the wireless communication devices in the first cell transmits a calibration signal, and Calibration in which a slave wireless communication device other than the master wireless communication device in the first cell receives the calibration signal and adjusts the transmission timing of a signal transmitted by the slave wireless communication device based on the received calibration signal When the adjustment unit that instructs the master wireless communication device to execute the process and the wireless communication device in the second cell receive the calibration signal transmitted by the master wireless communication device with power higher than the first threshold, Obtaining reception quality information regarding the reception quality of the calibration signal in the wireless communication device in the second cell It has a resulting portion, based on the obtained reception quality information, and a control unit for selecting a master wireless communication device from the wireless communication device in the first cell.

  One disclosure can prevent a failure caused by receiving calibration signals in adjacent cells with overpower.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 10. FIG. 2 is a diagram illustrating a configuration example of the RRH 200. FIG. 3 is a diagram illustrating a configuration example of the BBU 300. FIG. 4 is a diagram illustrating an example of a calibration process sequence. FIG. 5 is a diagram illustrating an example of a process flowchart of the calibration process S101. FIG. 6 is a diagram illustrating an example of a process flowchart of the master RRH process S103. FIG. 7 is a diagram illustrating an example of the format of the calibration signal and the calibration signal response. FIG. 8 is a diagram illustrating an example of a process flowchart of the calibration signal reception process S105. FIG. 9 is a diagram illustrating an example of the master RRH management table 324. FIG. 10 is a diagram illustrating an example of a sequence in which the BBU 300-1 receives a calibration signal reception notification during the execution of the calibration process. FIG. 11 shows an example of the format of the calibration signal reception notification. FIG. 12 is a diagram illustrating an example of a process flowchart of the calibration signal reception notification reception process S202. FIG. 13 is a diagram illustrating an example of the adjacent RRH management table 325. FIG. 14 is a diagram illustrating an example of a process flowchart of the master RRH reselection process S204. FIG. 15 is a diagram illustrating an example of the master RRH management table 324 that stores estimated values. FIG. 16 is a diagram illustrating an example of the adjacent RRH management table 325 that stores estimated values. FIG. 17 is a diagram illustrating an example of a sequence of the reception condition relaxation processing S301. FIG. 18 is a diagram illustrating an example of a process flowchart of the reception condition relaxation process S301. FIG. 19 is a diagram illustrating an example of the transition of the reception level of the calibration signal in the RRH 200 over time. FIG. 20 is a diagram illustrating a configuration example of the wireless communication system 10.

[First embodiment]
A first embodiment will be described.

<Configuration example of wireless communication system>
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 10. The radio communication system 10 includes RRHs 200-1 to 8 (hereinafter sometimes referred to as RRH200), BBUs (Base Band Unit) 300-1 and 2 (hereinafter sometimes referred to as BBU300), and MME (Mobility Management Entity). ) 400.

  The wireless communication system 10 is, for example, a local area network such as Wi-Fi (Wi-Fi) or a wireless communication network such as LTE (Long Term Evolution). The wireless communication system 10 is a communication system that provides communication to a terminal device in order for a terminal device (not shown) to receive services of an external network such as the Internet. The terminal device transmits / receives data packets to / from an external network via the RRH 200, the BBU 300, and the MME 400, thereby realizing communication.

  The RRH 200 is a wireless communication device that performs wireless communication with a terminal device. The RRH 200 is a device that performs a part of functions (for example, radio processing) of eNodeB (evolved Node B) in LTE, for example.

  Moreover, RRH200-1-4 comprise a cell. A cell is, for example, a collection of RRHs 200 that cooperatively transmit signals to terminal devices. The radio communication system 10 realizes multiple-input and multiple-output (MIMO) and multi-user MIMO (MU-MIMO) by cooperatively transmitting signals with a plurality of RRHs 200.

  The BBU 300 is a control device that controls the RRH 200 of the own cell (first cell) configured by the subordinate RRHs 200. The BBU 300 is a device that performs a part of functions of eNodeB in LTE (for example, baseband processing), for example. The RRH 200 and the BBU 300 are connected by an optical cable compliant with, for example, CPRI (Common Public Radio Interface).

  The BBU 300 controls one or more RRHs 200. And BBU300 comprises a cell by subordinate RRH200. The BBU 300-1 has a cell C300-1, and the BBU 300-2 has a cell C300-2. In FIG. 1, a part of cell C300-1 and cell C300-2 overlap. In a range where cells overlap, signals in a plurality of cells reach with a received power equal to or higher than a predetermined value.

  For example, the BBU 300-1 performs a calibration process for matching the phase of the radio wave transmitted by the RRHs 200-1 to 4 at the initial startup or periodically. In the calibration process, the BBU 300 classifies each of the RRHs 200-1 to 4 into a master RRH and a slave RRH. Then, the BBU 300-1 instructs the master RRH to transmit a calibration signal. The master RRH transmits a calibration signal (wireless signal) to the designated slave RRH in accordance with the instruction of the BBU 300. The slave RRH receives the calibration signal and transmits a calibration response signal indicating that the calibration signal has been received to the master RRH. In addition, the slave RRH adjusts the transmission timing and phase of the signal transmitted by the own apparatus based on the calibration signal pattern included in the received calibration signal. When the BBU 300 detects that the calibration response signals have been received from all the slave RRHs to be calibrated, the BBU 300 ends the calibration process.

  When the RRHs 200-5 to 5-8 under the BBU 300-2 adjacent to the cell of the BBU 300-1 receive the calibration signal transmitted by the master RRH of the BBU 300-1 with power equal to or higher than the first threshold, the calibration signal reception notification Is transmitted to the BBU 300-1. When the BBU 300-1 receives a calibration signal reception notification from the RRH 200 of the other cell (second cell) during the calibration process, the BBU 300-1 stops the calibration process and reselects the master RRH.

<Configuration example of RRH>
FIG. 2 is a diagram illustrating a configuration example of the RRH 200. The RRH 200 includes a CPU (Central Processing Unit) 210, a storage 220, a memory 230 such as a DRAM (Dynamic Random Access Memory), a NIC (Network Interface Card) 240, and an RF (Radio Frequency) circuit 250.

  The storage 220 is an auxiliary storage device such as a flash memory, an HDD (Hard Disk Drive), or an SSD (Solid State Drive) that stores programs and data. The storage 220 stores a wireless communication program 221, a master RRH program 222, and a calibration signal reception program 223.

  The memory 230 is an area for loading a program stored in the storage 220. The memory 230 is also used as an area where the program stores data.

  The NIC 240 is a network interface that connects to the BBU 300. The RRH 200 is controlled by the BBU 300 via the NIC 240.

  The RF circuit 250 is a device that wirelessly connects to a terminal device. For example, the RF circuit 250 includes an antenna 251. The RF circuit 250 receives a calibration signal from another RRH 200 or transmits a response signal to the other RRH 200 in the calibration process. For example, the RF circuit 250 stops or starts transmission / reception of radio waves (signals) by the CPU 210 controlling the switch of the antenna 251. When the reception of the RF circuit 250 is stopped, for example, power is not input to a device (for example, an amplifier, a digital / analog conversion device, a modulation / demodulation device) included in the RF circuit 250. That is, by stopping the reception of the RF circuit 250, the RRH 200 can stop the input of power due to reception of radio waves (signals), and can prevent a device failure due to overpower.

  The CPU 210 performs a wireless communication process by executing the wireless communication program 221. The wireless communication process is a process of wirelessly connecting to a terminal device and relaying communication performed by the terminal device. The wireless communication process is a process of transmitting a packet received from the terminal apparatus to the BBU 300 or transmitting a packet received from the BBU 300 to the terminal apparatus. The RRH 200 modulates and demodulates packets to be transmitted and received, and performs digital conversion and analog conversion in wireless communication processing.

  The CPU 210 executes the master RRH program 222 to construct a master processing unit and perform master RHH processing. The master RRH process is a process of transmitting a calibration signal using the own apparatus as a master RRH, and is a process of transmitting a calibration signal to a designated slave RRH in accordance with an instruction from the BBU 300 (for example, a calibration start notification). . Note that the RRH 200 increases, for example, the transmission power of the calibration signal in a stepwise manner in the master RRH process.

  The CPU 210 executes the calibration signal reception program 223 to construct a slave processing unit and another cell signal reception unit and perform a calibration signal reception process. The calibration signal reception process is a process when a calibration signal is received with a received power equal to or higher than a threshold (first threshold). In the calibration signal reception process, the RRH 200 adjusts the transmission timing and phase of the transmission signal when the calibration signal transmission source RRH belongs to the own cell. On the other hand, when the transmission source RRH belongs to another cell, the RRH 200 transmits a calibration signal reception notification indicating that the calibration signal has been received to the BBU 300 of the other cell.

<Example of BBU configuration>
FIG. 3 is a diagram illustrating a configuration example of the BBU 300. The BBU 300 includes a CPU 310, a storage 320, a memory 330 such as a DRAM, and NICs 340-1 to 340-n.

  The storage 320 is an auxiliary storage device such as a flash memory, an HDD, or an SSD that stores programs and data. The storage 320 stores a wireless communication control program 321, a calibration program 322, a calibration signal reception notification reception program 323, a master RRH management table 324, and an adjacent RRH management table 325.

  The master RRH management table 324 is a table that stores transmission power for each master RRH, SINR (signal-to-interference noise ratio) and propagation loss in the slave RRH. The master RRH management table 324 stores “signal level”, “SINR”, and “propagation loss” for each master RRH and slave RRH.

  “Signal level” is the transmission power of the calibration signal transmitted by the master RRH, and its unit is dBm. “SINR” is a noise level in the slave RRH, and its unit is dB. “Propagation loss” is the amount of power that attenuates in the radio section until the calibration signal transmitted by the master RRH is received by the slave RRH, and its unit is dB.

  The adjacent RRH management table 325 is a table that stores, for each master RRH, the reception quality of the calibration signal received by the RRH 200 of the adjacent cell (hereinafter may be referred to as the adjacent RRH). The adjacent RRH management table 325 stores “reception level”, “SINR”, and “propagation loss” for each master RRH and adjacent RRH.

  “Reception level” is the received power of the calibration signal received by the adjacent RRH, and its unit is dBm. “SINR” is the degree of signal interference in adjacent RRH, and its unit is dB. “Propagation loss” is the amount of power that attenuates in the radio section until the calibration signal transmitted by the master RRH is received by the adjacent RRH, and its unit is dB.

  The memory 330 is an area for loading a program stored in the storage 320. The memory 330 is also used as an area where the program stores data.

  NICs 340-1 to n (hereinafter may be referred to as NIC 340) are network interfaces connected to the subordinate RRH 200 and MME 400. The BBU 300 transmits / receives a message to / from the RRH 200 via the NIC 340.

  The CPU 310 performs a wireless communication control process by executing the wireless communication control program 321. The wireless communication control process is a process for relaying the communication of the terminal device by controlling the RRH 200. The BBU 300 performs, for example, baseband processing of a received signal in the wireless communication control processing.

  The CPU 310 executes the calibration program 322 to construct an adjustment unit and a control unit and perform a calibration process. The calibration process is a process for instructing the master RRH to transmit a calibration signal to the slave RRH to be calibrated. In the calibration process, the BBU 300 adjusts the transmission timing and phase of the signal transmitted by the subordinate RRH 200 to realize communication by MIMO or MU-MIMO.

  The CPU 310 executes the calibration signal reception notification reception program 323 to construct an acquisition unit and a control unit, and performs calibration signal reception notification reception processing. The calibration signal reception notification reception process is a process of receiving a calibration signal reception notification from the adjacent RRH. In receiving the calibration signal reception notification, the BBU 300 stops the calibration process being executed, reselects the master RRH, and performs the calibration process again.

<Calibration process>
FIG. 4 is a diagram illustrating an example of a calibration process sequence. When the BBU 300-1 detects the start timing of the calibration process, the BBU 300-1 performs the calibration process (S101). The trigger for starting calibration is, for example, the expiration of the interval timer or the establishment of a new cell (for example, C300-2) in the wireless communication system 10. Moreover, the calibration start trigger may be that the radio quality is deteriorated or that the phase of the signal transmitted between the RRHs 200 in the cell is shifted by more than the reference value.

  FIG. 5 is a diagram illustrating an example of a process flowchart of the calibration process S101. The BBU 300 selects the slave RRH to be calibrated from the slave RRHs 200 that have not been calibrated (S101-1). For example, the BBU 300 selects RRHs to be calibrated from the slave RRHs 200 that have not been calibrated, in ascending order of distance from the master RRH.

  The BBU 300 transmits a calibration start notification to the master RRH so as to transmit a calibration signal to the calibration target RRH (S101-2). The calibration start notification includes, for example, the identifier of the RRH 200 to be calibrated and the transmission output of the calibration signal. Further, for example, when the master RRH increases the transmission output in stages and transmits the calibration signal, the calibration start notification may include the initial value of the transmission output and the increase range of the transmission output.

  The BBU 300 waits to receive a calibration completion notification of the calibration target slave RRH (No in S101-3). When the BBU 300 receives a calibration completion notification indicating that the calibration processing of the calibration target slave RRH has been completed (Yes in S101-3), the BBU 300 updates the master RRH management table 324 (S101-4).

  Then, the BBU 300 confirms whether there is a slave RRH that has not been calibrated (S101-5). When there is a slave RRH that has not been calibrated (Yes in S101-5), the BBU 300 selects a slave RRH to be calibrated from the RRH 200 that has not been calibrated (S101-1). Then, if there is no slave RRH that has not been calibrated (No in S101-5), the BBU 300 ends the process.

  Returning to the sequence of FIG. 4, in the calibration process S101, the BBU 300-1 transmits a calibration start notification of the RRH 200-2 to be calibrated to the RRH 200-1 that is the master RRH (S102, S101- of FIG. 5). 2). Note that the master RRH at the time of the first execution of the calibration process is, for example, the RRH 200 closest to the BBU 300, the RRH 200 that can transmit a signal with the largest transmission power, or the RRH 200 stored in advance.

  Upon receiving the calibration start notification, the RRH 200-1 performs master RRH processing (S103).

  FIG. 6 is a diagram illustrating an example of a process flowchart of the master RRH process S103. The RRH 200 waits to receive a calibration start notification (No in S103-1). When the RRH 200 receives the calibration start notification (Yes in S103-1), the RRH 200 detects that the RRH 200 is the master RRH, and transmits a calibration signal to the slave RRH specified by the calibration start notification (S103-). 2).

  The RRH 200 waits to receive a calibration response signal from the slave RRH (No in S103-3). When the RRH 200 receives the calibration response signal (Yes in S103-3), the calibration is completed including the information elements (transmission source RRH identifier, reception calibration signal information, and reception power information) included in the received calibration response signal. The notification is transmitted to the BBU 300 of the own cell (S103-4).

  FIG. 7 is a diagram illustrating an example of the format of the calibration signal and the calibration signal response. 7A shows the calibration signal, and FIG. 7B shows the format of the calibration signal response.

  The calibration signal shown in FIG. 7A includes a CAL signal identifier, a transmission source RRH identifier, a CAL signal pattern, and transmission power.

  The CAL signal identifier is an identifier indicating that it is a calibration signal, and is 0x01, for example.

  The transmission source RRH identifier is an identifier of the RRH 200 that is the transmission source of the calibration signal.

  The CAL signal pattern is a signal pattern used for performing calibration, and is, for example, a fixed value (0xFF).

  The transmission power is output power when the RRH 200 transmits a calibration signal.

  Further, the calibration response signal shown in FIG. 7B includes a CAL signal identifier, a transmission source RRH identifier, reception calibration signal information, and reception quality information.

  The CAL signal identifier is an identifier indicating that it is a calibration response signal, and is 0x02, for example.

  The transmission source RRH identifier is an identifier of the RRH 200 that is the transmission source of the calibration response signal.

  The reception calibration signal information is information related to the calibration signal received by the RRH 200, and includes, for example, transmission power and a transmission source RRH identifier. The transmission power is the transmission power included in the received calibration signal. The transmission source RRH identifier is a transmission source RRH identifier included in the received calibration signal.

  The reception quality information is information regarding the reception quality of the received calibration signal, and includes, for example, reception power and SINR. The received power is the received power of the calibration signal in the RRH 200. The SINR is the SINR when the calibration signal is received in the RRH 200. The reception quality information may include propagation loss instead of reception power. The propagation loss is a value indicating the amount of power of a signal that is attenuated in the radio section, and is, for example, a numerical value obtained by subtracting received power from transmission power of a calibration signal.

  Returning to the sequence of FIG. 4, the RRH 200-1 transmits a calibration signal to the slave RRH 200-2 designated by the calibration start notification in the master RRH calibration process S103 (S104, S103-2 of FIG. 6). . When the RRH 200-2 receives the calibration signal transmitted from the master RRH, the RRH 200-2 performs a calibration signal reception process (S105).

  FIG. 8 is a diagram illustrating an example of a process flowchart of the calibration signal reception process S105. The RRH 200 determines whether or not the received calibration signal is a signal transmitted from the RRH 200 of the own cell (S105-1). When determining that the RRH 200 is the RRH of the own cell (Yes in S105-1), the RRH 200 confirms whether or not the received power of the calibration signal is greater than or equal to the CAL threshold (S105-2). The CAL threshold is a power threshold indicating whether to perform calibration (for example, adjustment of transmission timing or phase) based on the calibration signal received by the slave RRH. The slave RRH discards the calibration signal received with the power less than the CAL threshold value, because the reception quality is low and is not used for calibration.

  When the received power is greater than or equal to the CAL threshold (Yes in S105-2), the RRH 200 adjusts the transmission timing of the transmission signal based on the received calibration signal (S105-3). Note that the process S105-4 is a calibration process, and the RRH 200 adjusts the transmission timing by adjusting the phase of the transmission signal. Then, the RRH 200 transmits a calibration response signal to the calibration signal transmission source RRH 200 (S105-4).

  On the other hand, when the received power is less than the CAL threshold (No in S105-2), the RRH 200 ends the process without performing calibration.

  Further, when the RRH 200 determines that the received calibration signal is not the RRH 200 of the own cell (No in S105-1), the RRH 200 confirms whether or not the received power of the calibration signal is greater than or equal to the first threshold (S105-5). ). The first threshold is reception power indicating whether the RRH 200 transmits a calibration signal reception notification to the BBU 300. The first threshold is, for example, sufficiently lower power than the received power at which the RRH 200 fails due to reception (hereinafter sometimes referred to as a device destruction level).

  When the received power of the calibration signal is equal to or higher than the first threshold (Yes in S105-5), the RRH 200 transmits a calibration signal reception notification to the BBU 300 to which the calibration signal transmission source RRH 200 belongs (S105-6). The calibration signal reception notification may be transmitted to the transmission destination BBU 300 via the BBU 300 of the own cell, or may be transmitted to the transmission destination BBU 300 via the transmission source RRH 200. The calibration signal reception notification will be described later.

  On the other hand, when the received power of the calibration signal is less than the first threshold (No in S105-5), the RRH 200 ends the process without transmitting the calibration signal reception notification.

  Returning to the sequence of FIG. 4, the RRH 200-2 transmits a calibration response signal to the RRH 200-1 in the calibration signal reception process S105 (S106, S105-4 of FIG. 8).

  In the master RRH process S103, the RRH 200-1 receives the calibration response signal (Yes in S103-3 in FIG. 6), and transmits a calibration completion notification to the BBU 300-1 (S107, S103-4 in FIG. 6). . The calibration completion notification includes the identifier of RRH 200 for which calibration has been completed (identifier of RRH 200-2).

  In the calibration process S101, the BBU 300-1 receives the calibration completion notification (Yes in S101-3 in FIG. 5), and updates the master RRH management table 324 (S101-4 in FIG. 5). Then, the BBU 300-1 calibrates the RRH 200-3 that has not been calibrated. Processes S108 to S111 are calibrations for the RRH 200-3, and are the same processes as processes S102 to S107. The BBU 300-1 also performs calibration for the RRH 200-4, and performs the same processing as the processing from S102 to S107 on the RRH 200-4.

  FIG. 9 is a diagram illustrating an example of the master RRH management table 324. The BBU 300 updates the master RRH management table 324 based on the information of the calibration response signal included in the calibration completion notification received in the calibration process S101.

  The signal level of the master RRH management table 324 is, for example, transmission power included in the calibration response signal. The SINR of the master RRH management table 324 is, for example, the SINR included in the calibration response signal. Furthermore, the propagation loss in the master RRH management table 324 is a numerical value obtained by subtracting the reception power from the transmission power included in the calibration response signal, for example. Alternatively, the propagation loss of the master RRH management table 324 may be a propagation loss included in the calibration response signal when the propagation loss is included in the calibration response signal, for example.

  FIG. 9 is an example of the master RRH management table 324 when the calibration process in which the master RRH is the RRH 200-1 is completed. The master RRH management table 324 stores the signal level, SINR, and propagation loss of each of the slave RRHs 200-2 to 4-4.

  As shown in the sequence of FIG. 4, the BBU 300 selects one master RRH from the subordinate RRH 200. Then, the BBU 300 adjusts the transmission timing (the phase of the transmission signal) of signals transmitted from the other slave RRHs and the master RRH by transmitting a calibration start notification to the master RRH and transmitting a calibration signal.

<Processing upon receipt of calibration signal reception notification>
When the BBU 300 receives a calibration signal reception notification from the RRH 200 of another cell during the execution of the calibration process, for example, the BBU 300 stops the calibration process and performs the master RRH reselection process. Receiving the calibration signal reception notification from the RRH 200 of the other cell indicates that the RRH 200 of the other cell receives the calibration signal transmitted by the master RRH 200 of the own cell with the power equal to or higher than the first threshold. .

  FIG. 10 is a diagram illustrating an example of a sequence in which the BBU 300-1 receives a calibration signal reception notification during the execution of the calibration process. Processing S101 to processing S104 illustrated in FIG. 10 is the same as processing S101 to processing S104 illustrated in FIG.

  RRH200-6 is not the RRH200 under the control of the BBU300-1, but the RRH200 under the control of the adjacent BBU300-2. For this reason, when receiving the calibration signal transmitted by the RRH 200-1, the RRH 200-6 transmits a calibration signal reception notification to the BBU 300-1 in the calibration signal reception process S105 (S201, S105-6 in FIG. 8). . In FIG. 10, the calibration signal reception notification S201 is transmitted to the BBU 300-1 via the RRH 200-1.

  FIG. 11 shows an example of the format of the calibration signal reception notification. The calibration signal reception notification includes a CAL signal identifier, a transmission source RRH identifier, reception calibration signal information, and reception information.

  The CAL signal identifier is an identifier indicating that it is a calibration signal reception notification, and is 0x03, for example.

  The transmission source RRH identifier is an identifier of the RRH 200 that is the transmission source of the calibration signal reception notification.

  The reception calibration signal information is information related to the calibration signal received by the RRH 200, and includes, for example, transmission power and a transmission source RRH identifier. The transmission power is the transmission power included in the received calibration signal. The transmission source RRH identifier is a transmission source RRH identifier included in the received calibration signal.

  The reception quality information is information regarding the reception quality of the received calibration signal, and includes, for example, reception power and SINR. The received power is the received power of the calibration signal in the RRH 200. The SINR is the SINR when the calibration signal is received in the RRH 200. The reception quality information may include propagation loss instead of reception power.

  Returning to the sequence of FIG. 10, when the BBU 300-1 receives a calibration signal reception notification during execution of the calibration process, the BBU 300-1 performs a calibration signal reception notification reception process (S202).

  FIG. 12 is a diagram illustrating an example of a process flowchart of the calibration signal reception notification reception process S202. The BBU 300 waits for reception of a calibration signal reception notification (No in S202-1). When the BBU 300 receives the calibration signal reception notification (Yes in S202-1), the BBU 300 updates the adjacent RRH management table 325 (S202-2). Then, the BBU 300 stops the calibration process being executed (S202-3), and transmits a calibration stop to the master RRH (S202-4). Further, the BBU 300 performs a master RRH reselection process (S204).

  FIG. 13 is a diagram illustrating an example of the adjacent RRH management table 325. The reception level of the adjacent RRH management table 325 is the reception power of the calibration signal in the RRH 200 and is the reception power included in the calibration signal reception notification. The SINR in the adjacent RRH management table 325 is the SINR in the RRH 200 and is the SINR included in the calibration signal reception notification. The propagation loss in the adjacent RRH management table 325 is a numerical value obtained by subtracting the reception power from the transmission power included in the calibration signal reception notification.

  FIG. 14 is a diagram illustrating an example of a process flowchart of the master RRH reselection process S204. The BBU 300 stores the estimated value in the master RRH management table 324 and the adjacent RRH management table 325 (S204-1).

  FIG. 15 is a diagram illustrating an example of the master RRH management table 324 that stores estimated values. The numerical values shaded in FIG. 15 indicate estimated values.

  The BBU 300 assumes that the slave RRH other than the master RRH is the master RRH, and calculates an estimated value when the assumed master RRH transmits a calibration signal.

  In calculating the estimated value of the propagation loss, the BBU 300 calculates the estimated value according to, for example, the Okumura-Kashiwa model. The estimated value of the propagation loss is calculated using, for example, the frequency of the radio wave, the antenna height of the master RRH, the antenna height of the slave RRH, the distance between the master RRH and the slave RRH, and the correction value indicated by the Okumura-Kashiwa model. The BBU 300 may store the frequency of the radio wave, the antenna height of the master RRH, the antenna height of the slave RRH, and the distance between the master RRH and the slave RRH in advance in the internal memory. Further, the BBU 300 may acquire the antenna height of the slave RRH from the slave RRH. Further, the BBU 300 may acquire the distance between the master RRH and the slave RRH based on the acquired position information and the position information of the own device (master RRH). For example, according to FIG. 15, when the RRH 200-2 is the master RRH, the estimated value of the propagation loss in the RRH 200-4 is 50 dB.

  In calculating the estimated value of the signal level, the BBU 300 uses the estimated value of the propagation loss. The signal level is, for example, a numerical value obtained by adding a propagation loss to power (CAL threshold value) that determines that the slave RRH has received the calibration signal. For example, according to FIG. 15, when the power for determining that the calibration signal is received is −80 dBm, −80 + 50 (estimated propagation loss) = − 30 dBm, and RRH 200 when RRH 200-2 is the master RRH. -4 is an estimated value of the signal level of the calibration signal transmitted to -4.

  The SINR is regarded as being equivalent to the case where the RRH 200-1 is the master RRH, and the actually measured value when the master RRH is the RRH 200-1 is used as the estimated value. For example, according to FIG. 15, the actual SINR value (20 dB) in the RRH 200-4 when the master RRH is the RRH 200-1 is the estimated SINR value in the RRH 200-4 when the master RRH is the RRH 200-2. .

  As described above, the BBU 300 calculates an estimated value and stores it in the master RRH management table 324 for the information element that does not store the actual measurement value in the process S204-1 of FIG. Note that the BBU 300 uses the Okumura-Kashiwa model for estimation of propagation loss, but other methods for estimating propagation characteristics may be used.

  FIG. 16 is a diagram illustrating an example of the adjacent RRH management table 325 that stores estimated values. The numerical values shaded in FIG. 16 indicate estimated values.

  In calculating the propagation loss, the BBU 300 calculates an estimated value, for example, according to the Okumura-Kashiwa model, similarly to the calculation of the estimated value in the master RRH management table 324. For example, according to FIG. 16, when the RRH 200-2 is the master RRH, the propagation loss in the RRH 200-6 is 90 dB.

  In calculating the estimated value of the reception level, the BBU 300 uses the estimated value of propagation loss. The reception level is, for example, a numerical value obtained by subtracting the propagation loss from the maximum signal level of the master RRH. The maximum value of the signal level is the maximum power of the calibration signal transmitted by the master RRH, and the reception power when the adjacent RRH receives the calibration signal transmitted at the maximum power is the maximum of the calibration signal in the adjacent RRH. It can be regarded as received power. According to FIG. 14, the maximum value of the signal level when the master RRH is RRH 200-2 is the signal level of −30 dBm with respect to RRH 200-4. Therefore, according to FIG. 15, when the master RRH is RRH 200-2, the estimated value of the reception level of RRH 200-6 is −120 dBm obtained by subtracting the estimated value 90 dB of propagation loss from −30 dBm.

  SINR calculates an estimated value using an estimated value of the reception level. The estimated value of SINR is, for example, a numerical value obtained by subtracting the noise difference with respect to the reception level from the estimation value of the reception level. The noise difference with respect to the reception level is, for example, a numerical value obtained by subtracting the SINR of the actual measurement value from the reception level of the actual measurement value. According to FIG. 16, the noise difference with respect to the reception level can be calculated as −35 (reception level) −10 (SINR) = − 45 using an actual measurement value when the master RRH is RRH200-1. According to FIG. 16, the estimated value of SINR in RRH 200-6 when master RRH is RRH 200-2 is −120 (reception level) − (− 45) = − 75 dB.

  As described above, the BBU 300 calculates the estimated value of the information element that does not store the actual measurement value for the RRH 200 of the other cell that has received the calibration signal in the process S204-1 of FIG. 14, and stores the estimated value in the adjacent RRH management table 325. To do.

  Returning to FIG. 14, the BBU 300 evaluates each RRH 200 (S204-2). The RRH evaluation is, for example, higher for RRH 200 having a lower reception level in the adjacent RRH management table. In FIG. 16, RRH200-3 has the highest evaluation, and RRH200-1 has the lowest evaluation.

  The RRH evaluation may be performed using, for example, the reception level of the adjacent RRH management table 325 and the SINR of the master RRH management table 324. In FIG. 16, for example, the RRH 200-3 having the lowest reception level in the adjacent RRH management table 325 and the RRH 200-2 having a difference of only 10 dBm from the RRH 200-3 are evaluated as high. Then, the SINRs are compared when the RRH 200-2 and the RRH 200-3 in the master RRH management table 324 are set as the master RRH. According to FIG. 15, when the RRH 200-2 is the master RRH, the SINR in the slave RRH is −10 dB. On the other hand, according to FIG. 15, when the RRH 200-3 is the master RRH, the SINR in the slave RRH is 0 dB. Therefore, since the SINR is lower when the RRH 200-2 is the master RRH than when the RRH 200-3 is the master RRH, the RRH 200-2 is rated higher. That is, according to FIG.15 and FIG.16, RRH200-2 becomes the highest evaluation.

  The BBU 300 selects the RRH 200 having the highest evaluation other than the selected RRH as the master RRH (S204-3). The selected RRH is information storing the RRH 200 that the BBU 300 has been selected as the master RRH in the past. The BBU 300 excludes the RRH 200 selected in the past from the new master RRH candidates. Note that the selected RRH is cleared when, for example, a predetermined time elapses. For example, the selected RRH may be cleared when the calibration process is completed without receiving a calibration signal reception notification from the RRH 200 of the adjacent cell.

  The BBU 300 confirms whether or not the master RRH cannot be selected (S204-4). The case where the master RRH cannot be selected indicates a case where there is no RRH 200 other than the selected RRH, or a case where there is no RRH 200 with an evaluation equal to or higher than the threshold.

  When the master RRH 200 can be selected (No in S204-4), the BBU 300 stores the selected RRH 200 as the selected RRH (S204-7), and performs the calibration process S101 with the selected RRH as the master RRH.

  On the other hand, when the BBU 300 cannot select the master RRH 200 (Yes in S204-4), the BBU 300 determines whether the reception condition relaxation count is equal to or greater than a threshold (S204-5). The reception condition relaxation count indicates the number of times the reception condition relaxation processing described later is executed. That the reception condition relaxation count is equal to or greater than the threshold value indicates that no further relaxation of the reception condition is performed.

  If the reception condition relaxation count is equal to or greater than the threshold (Yes in S204-5), the BBU 300 reports to the system administrator without performing the reception condition relaxation process (S204-8), and ends the process. The system administrator changes the system configuration so as not to cause device destruction due to the calibration signal, for example, by changing the position of the RRH 200.

  On the other hand, if the reception condition relaxation count is not equal to or greater than the threshold (No in S204-5), the BBU 300 performs reception condition relaxation processing (S301). The reception condition relaxation process S301 will be described later.

  Then, the BBU 300 selects the RRH having the highest evaluation as the master RRH (S204-6). Note that the RRH selected in step S204-6 may be a selected RRH. This is because the selected RRH is the RRH selected as the master RRH before the reception condition is relaxed, and therefore it is not appropriate to exclude it as a master RRH candidate after the reception condition is relaxed. Note that the selected RRH may be cleared before performing the reception condition relaxation processing S301. Similar to the case where the master RRH is selected, the BBU 300 stores the selected RRH 200 as the selected RRH (S204-7), and performs the calibration process S101 using the selected RRH 200 as the master RRH.

  In the first embodiment, when the calibration signal transmitted by the master RRH of the own cell is received by the RRH 200 of the adjacent cell, the BBU 300 changes the master RRH to another RRH 200. Thereby, in the calibration process, the BBU 300 can suppress the arrival of a calibration signal having strong power to the adjacent RRH, and can suppress the occurrence of a failure due to the adjacent RRH receiving a signal with excessive power.

<Reception condition relaxation processing>
FIG. 17 is a diagram illustrating an example of a sequence of the reception condition relaxation processing S301. In the master RRH reselection process S204, for example, when the unselected RRH 200 cannot be selected as the master RRH (Yes in S204-4 in FIG. 14), the BBU 300 has a reception condition relaxation count less than the threshold (S204- in FIG. 14). 5 No), the reception condition relaxation processing S301 is performed.

  FIG. 18 is a diagram illustrating an example of a process flowchart of the reception condition relaxation process S301. The BBU 300 transmits a reception condition notification to the target RRH 200 (S301-1). The target RRH 200 is, for example, the RRH 200 that has transmitted a calibration signal reception notification to the BBU 300. The reception condition notification includes, for example, a threshold value (first threshold value after change) for determining that the RRH 200 has received a calibration signal of another cell. When the RRH 200 receives a calibration signal from another cell with power equal to or higher than the first threshold value, the RRH 200 transmits a calibration signal reception notification. Note that the BBU 300 may transmit a message to the target RRH 200 via the BBU 300 of the cell to which the target RRH 200 belongs.

  The BBU 300 waits for reception of a reception condition notification response (No in S301-2). Then, the BBU 300 receives the reception condition notification response (Yes in S301-2) and ends the process.

  Returning to the sequence of FIG. 17, the BBU 300-1 transmits a reception condition notification to the RRH 200-6 via the BBU 300-2 in the reception condition relaxation process S <b> 301 (S <b> 302). When receiving the reception condition notification response (S303), the BBU 300-1 performs the calibration process S101 again and transmits a calibration start notification to the RRH 200-1. The RRH 200-1 transmits a calibration signal as the master RRH (S305).

  FIG. 19 is a diagram illustrating an example of the transition of the reception level of the calibration signal in the RRH 200 over time. For example, the master RRH gradually increases the transmission output of the calibration signal.

  The reception level LB is a reception level at which the RRH 200 fails, for example, a device destruction level. When the RRH 200 receives a signal with power equal to or higher than the reception level LB, the RRH 200 fails due to overpower.

  The threshold value LT1 is the first threshold power value (first power value) before the reception condition relaxation processing S301 is performed. The threshold LT1 is, for example, reception power that is sufficiently lower than the reception level LB.

  The threshold LT2 is the first threshold power value (second power value) included in the reception condition notification in the reception condition relaxation process S301. The threshold value LT2 is, for example, a numerical value obtained by adding a predetermined value (for example, a predetermined setting value) to the threshold value LT1. The threshold LT2 may be the maximum received power that can be received by the RRH 200 based on the maximum transmission power in the specifications of the master RRH and the propagation loss between the master RRH and the RRH 200. When the maximum received power that can be received by the RRH 200 is equal to or higher than the reception level LB, the post-change threshold value TL2 is not the maximum received power that can be received by the RRH 200 but is a numerical value lower than the reception level LB.

  In the first embodiment, even if the master RRH is reselected, when the RRH 200 of the adjacent cell receives a calibration signal with power equal to or higher than the initial threshold, the BBU 300 reduces the reception power condition from the initial threshold. The threshold value is changed to a threshold value that indicates a large received power that does not cause a failure in the RRH 200. By performing calibration again after changing the threshold value, the BBU 300 is more likely to select a master RRH that does not reach the RRH 200 of the adjacent cell with reception power at which the calibration signal fails.

[Second Embodiment]
Next, a second embodiment will be described. The radio communication system 10 according to the second embodiment further includes a cell C300-3 in the cell C300-1 and the cell C300-2. The cell C300-3 is newly installed in the radio communication system 10.

<Configuration example of wireless communication system>
FIG. 20 is a diagram illustrating a configuration example of the wireless communication system 10. The wireless communication system 10 further includes a BBU 300-3 and RRHs 200-9 to 12 (hereinafter may be referred to as RRH 200). The RRHs 200-9 to 12 configure the cell C300-3. In addition, BBU300-3 and RRH200-9-12 shall be newly installed in the radio | wireless communications system 10. FIG.

<Master RRH selection process>
When performing the calibration process, the BBU 300-1 selects the master RRH so that the RRH 200 of the newly installed cell C300-3 does not receive the calibration signal due to overpower. In the first embodiment, the BBU 300-1 determines the initial master RRH when executing the calibration process for the first time regardless of the reception quality. However, in the second embodiment, the BBU 300-1 selects the initial master RRH based on the actual measurement value and the estimated value.

  For example, the BBU 300-1 performs the same evaluation as the evaluation in the master RRH reselection process S204, and selects the RRH 200 having the highest evaluation as the master RRH. As a result, the BBU 300-1 can select an appropriate master RRH for at least the RRH 200 of the cell C300-1 and the cell C300-2. When the RRH 200 of the cell C300-3 receives the calibration signal transmitted by the selected master RRH with the power equal to or higher than the first threshold, the BBU 300-1 may reselect the master RRH in the evaluation order evaluated in advance. Alternatively, the master RRH may be reselected in consideration of the reception power in the RRH 200 of the cell C300-3.

[Other embodiments]
When the RRH 200 receives a calibration signal with a reception power equal to or higher than a predetermined value, the RRH 200 may stop receiving the signal. When the transmission power of the calibration signal increases step by step, the RRH 200 can stop receiving the calibration signal at a higher value by stopping reception at a predetermined value, and can prevent a failure due to overpower. When the RRH 200 detects that the calibration process is completed or completed (for example, reception of a notification from the BBU 300 or the master RRH), the RRH 200 resumes signal reception.

  Moreover, RRH200 may perform radio | wireless communication with a terminal device by a TDD (Time Division Duplex) system, for example. In this case, the RRH 200 is a signal transmission / reception switching period, and transmits a calibration signal during a period (TTP: Transmitter transient period) in which signal transmission / reception is not performed with a communication partner apparatus (for example, a terminal apparatus). At the TTP timing, the RRH 200 performs, for example, switching of antenna settings, and does not transmit / receive signals. As a result, the calibration signal can maintain the quality of the wireless communication without interfering with the signal transmitted and received by the wireless communication performed between the RRH 200 and the terminal device.

  As described above, the following additional notes are further disclosed with respect to the embodiments including the first, second, and other embodiments.

(Appendix 1)
A control device for controlling a wireless communication device constituting the first cell,
A master wireless communication device that is one of the wireless communication devices in the first cell transmits a calibration signal, and a slave wireless communication device other than the master wireless communication device in the first cell receives the calibration signal. An adjustment unit that instructs the master wireless communication device to perform a calibration process for adjusting a transmission timing of a signal transmitted by the slave wireless communication device based on the received calibration signal;
When the wireless communication device in the second cell receives the calibration signal transmitted from the master wireless communication device at a power higher than the first threshold, the reception quality of the calibration signal in the wireless communication device in the second cell An acquisition unit for acquiring reception quality information;
A control unit configured to select a master radio communication device from radio communication devices in the first cell based on the acquired reception quality information.

(Appendix 2)
The control device according to claim 1, wherein the adjustment unit causes the master wireless communication device to gradually increase a transmission output and transmit the calibration signal.

(Appendix 3)
The control unit assumes that a wireless communication device other than the master wireless communication device in the first cell is a master wireless communication device, and a calibration signal transmitted by the assumed master wireless communication device in the second cell. The control device according to claim 1, wherein an estimated value of received power in the wireless communication device is calculated, and a master wireless communication device is selected based on the estimated value of received power.

(Appendix 4)
The control device according to claim 3, wherein the control unit selects the assumed master wireless communication device having the lowest estimated value of received power in the wireless communication device in the second cell as a master wireless communication device.

(Appendix 5)
The control unit further calculates an estimated value of the degree of interference when the calibration signal transmitted by the assumed wireless communication device is received by the wireless communication device in the first cell, and the wireless signal in the second cell is calculated. The assumed master wireless communication device having the lowest estimated value of the interference degree is selected as a master wireless communication device among the assumed master wireless communication devices in which the estimated value of received power in the communication device is lower than a predetermined value. 3. The control device according to 3.

(Appendix 6)
The control device according to claim 5, wherein the degree of interference includes a signal-to-interference noise ratio (SINR).

(Appendix 7)
When the wireless communication device in the second cell receives a calibration signal transmitted from the selected master wireless communication device at a power higher than the first threshold, the control unit sets the first threshold to the first power. The control device according to claim 1, wherein the control device instructs the wireless communication device in the second cell to change from a value to a second power value higher than the first power value.

(Appendix 8)
The control device according to claim 7, wherein the control unit performs the instruction via the control device of the other cell.

(Appendix 9)
A master that transmits a calibration signal to a slave wireless communication device, which is another wireless communication device in the first cell, when selected as a master wireless communication device by a control device that controls the wireless communication device that configures the first cell. A processing unit;
A slave processor that receives the calibration signal and adjusts the transmission timing of the signal to be transmitted based on the received calibration signal when the control device is selected as the slave wireless communication device;
When a calibration signal transmitted by the wireless communication device in the second cell is received with power equal to or higher than the first threshold, a calibration signal including the received power of the calibration signal transmitted by the wireless communication device in the first cell is received. Another cell signal receiver for transmitting the notification to the control device of the second cell,
When the control device of the second cell receives the calibration signal reception notification, wireless communication in the second cell is performed based on the received power of the calibration signal transmitted by the wireless communication device in the first cell. A wireless communication device that selects a master wireless communication device from a device.

(Appendix 10)
The wireless communication device according to claim 9, wherein the other cell signal reception unit stops receiving a signal when receiving a calibration signal transmitted by the wireless communication device in the second cell with power equal to or higher than the first threshold.

(Appendix 11)
The wireless communication device according to claim 9, wherein the master processing unit transmits the calibration signal at a timing at which the wireless communication device does not transmit / receive a signal to / from a communication partner device.

(Appendix 12)
The wireless communication device according to claim 11, wherein the timing at which the wireless communication device does not transmit / receive a signal to / from a communication partner device includes TTP (Transmitter transient period).

(Appendix 13)
A calibration method in a control device for controlling a wireless communication device constituting a first cell,
A master wireless communication device that is one of the wireless communication devices in the first cell transmits a calibration signal, and a slave wireless communication device other than the master wireless communication device in the first cell receives the calibration signal. And instructing the master wireless communication device to perform a calibration process for adjusting the transmission timing of the signal transmitted by the slave wireless communication device based on the received calibration signal,
When the wireless communication device in another cell receives the calibration signal transmitted from the master wireless communication device with power higher than the first threshold, the reception quality related to the reception quality of the calibration signal in the wireless communication device in the other cell Get information,
A calibration method for selecting a master wireless communication device from the wireless communication devices based on the acquired reception quality information.

10: Wireless communication system,
200 ... RRH,
210 ... CPU,
220 ... Storage,
221: Wireless communication program,
222: Master RRH program,
223 ... Calibration signal reception program,
230 ... Memory,
240 ... NIC,
250 ... RF circuit,
251 ... Antenna,
300 ... BBU,
300 ... RRH,
310 ... CPU,
320 ... Storage,
321 ... Wireless communication control program,
322 ... Calibration program,
323 ... Calibration signal reception notification reception program,
324 ... Master RRH management table,
325 ... Adjacent RRH management table,
330 ... Memory,
340 ... NIC,
400 ... MME

Claims (10)

A control device for controlling a wireless communication device constituting the first cell,
A master wireless communication device that is one of the wireless communication devices in the first cell transmits a calibration signal, and a slave wireless communication device other than the master wireless communication device in the first cell receives the calibration signal. An adjustment unit that instructs the master wireless communication device to perform a calibration process for adjusting a transmission timing of a signal transmitted by the slave wireless communication device based on the received calibration signal;
When the wireless communication device in the second cell receives the calibration signal transmitted from the master wireless communication device at a power higher than the first threshold, the reception quality of the calibration signal in the wireless communication device in the second cell An acquisition unit for acquiring reception quality information;
A control unit configured to select a master radio communication device from radio communication devices in the first cell based on the acquired reception quality information. The control device according to claim 1, wherein the adjustment unit causes the master wireless communication device to gradually increase a transmission output and transmit the calibration signal. The control unit assumes that a wireless communication device other than the master wireless communication device in the first cell is a master wireless communication device, and a calibration signal transmitted by the assumed master wireless communication device in the second cell. The control device according to claim 1, wherein an estimated value of received power in the wireless communication device is calculated, and a master wireless communication device is selected based on the estimated value of received power. The control device according to claim 3, wherein the control unit selects the assumed master wireless communication device having the lowest estimated value of received power in the wireless communication device in the second cell as a master wireless communication device. The control unit further calculates an estimated value of the degree of interference when the calibration signal transmitted by the assumed wireless communication device is received by the wireless communication device in the first cell, and the wireless signal in the second cell is calculated. The assumed master wireless communication device having the lowest estimated interference degree is selected as a master wireless communication device among the assumed master wireless communication devices having an estimated value of received power lower than a predetermined value in the communication device. Item 4. The control device according to Item 3. When the wireless communication device in the second cell receives a calibration signal transmitted from the selected master wireless communication device at a power higher than the first threshold, the control unit sets the first threshold to the first power. The control device according to claim 1, wherein the control device instructs the wireless communication device in the second cell to change from a value to a second power value higher than the first power value. A master that transmits a calibration signal to a slave wireless communication device, which is another wireless communication device in the first cell, when selected as a master wireless communication device by a control device that controls the wireless communication device that configures the first cell. A processing unit;
A slave processor that receives the calibration signal and adjusts the transmission timing of the signal to be transmitted based on the received calibration signal when the control device is selected as the slave wireless communication device;
When a calibration signal transmitted by the wireless communication device in the second cell is received with power equal to or higher than the first threshold, a calibration signal including the received power of the calibration signal transmitted by the wireless communication device in the first cell is received. Another cell signal receiver for transmitting the notification to the control device of the second cell,
When the control device of the second cell receives the calibration signal reception notification, wireless communication in the second cell is performed based on the received power of the calibration signal transmitted by the wireless communication device in the first cell. A wireless communication device that selects a master wireless communication device from a device. The radio communication device according to claim 7, wherein the other cell signal reception unit stops receiving a signal when a calibration signal transmitted by the radio communication device in the second cell is received with power equal to or higher than the first threshold. . The wireless communication device according to claim 7, wherein the master processing unit transmits the calibration signal at a timing at which the wireless communication device does not transmit / receive a signal to / from a communication partner device. A calibration method in a control device for controlling a wireless communication device constituting a first cell,
A master wireless communication device that is one of the wireless communication devices in the first cell transmits a calibration signal, and a slave wireless communication device other than the master wireless communication device in the first cell receives the calibration signal. And instructing the master wireless communication device to perform a calibration process for adjusting the transmission timing of the signal transmitted by the slave wireless communication device based on the received calibration signal,
When the wireless communication device in another cell receives the calibration signal transmitted from the master wireless communication device with power higher than the first threshold, the reception quality related to the reception quality of the calibration signal in the wireless communication device in the other cell Get information,
A calibration method for selecting a master wireless communication device from the wireless communication devices based on the acquired reception quality information.

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