Wireless communication system, communication channel selection method, and radio base station

Abstract

A wireless communication system comprising a wireless base station for performing communication with one or a plurality of wireless terminals, and a first spectrum analyzer provided in the vicinity of the wireless base station. The first spectrum analyzer is configured so as to receive a first request from the wireless base station and execute a monitoring process for monitoring a first use state of a surrounding frequency channel. The wireless base station is configured so as to execute: a process for transmitting the first request to the first spectrum analyzer on a prescribed occasion; a process for acquiring the first use state from the first spectrum analyzer; and a process for selecting a communication channel on which to perform communication, in accordance with the first use state.

Description

Technical Field

[0001] The present disclosure relates to a technique for selecting a frequency channel to avoid interference in communication in other types of wireless communication systems.

Background Art

[0002] In a wireless communication system, generally, a communication channel for communication is selected from a plurality of candidate frequency channels. On the other hand, it is assumed that the frequency band used for communication by one wireless communication system is shared with other types of wireless communication systems. Here, in order to avoid interference in communication in other types of wireless communication systems, it is required not to select a frequency channel that is in use or has a high usage frequency in other types of wireless communication systems as the communication channel. For this reason, it is necessary to grasp the usage status of surrounding frequency channels. For example, in a wireless LAN (IEEE 802.11), a scan of the frequencies of surrounding wireless signals is performed, and a communication channel is selected in consideration of the availability (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, in a device included in a wireless communication system, the implementation of frequency scanning is limited to the time when transmission and reception are not performed by communication. Therefore, during the implementation of frequency scanning, transmission and reception by communication in the wireless communication system will stop. Particularly when coexisting with a narrowband wireless communication system, a long time is required for frequency scanning.

[0005] One object of the present disclosure is to provide a technology capable of selecting a communication channel that avoids interference with communication in another type of wireless communication system without stopping transmission and reception by communication.

Means for Solving the Problems

[0006] The first disclosure relates to a wireless communication system. The wireless communication system according to the first disclosure includes a wireless base station that communicates with one or more wireless terminals, and a first spectrum analyzer provided in the vicinity of the wireless base station. The first spectrum analyzer is configured to execute a monitoring process of monitoring the first usage status of surrounding frequency channels upon receiving a first request from the wireless base station. The wireless base station is configured to execute a process of transmitting the first request to the first spectrum analyzer on a predetermined occasion, a process of acquiring the first usage status from the first spectrum analyzer, and a channel selection process of selecting a communication channel for communication according to the first usage status.

[0007] The second disclosure relates to a wireless communication system that further has the following features with respect to the wireless communication system according to the first disclosure. The first usage status includes the reception level for each frequency channel or frequency of surrounding wireless signals. The wireless base station is further configured to execute a process of transmitting calibration information for designating a reference frequency band with the reception level set to zero for the reception level at a predetermined time to the first spectrum analyzer. The first spectrum analyzer is further configured to execute a process of setting, as a reference error, the reception level of the reference frequency band observed at the predetermined time in response to the calibration information. The monitoring process includes subtracting the reference error from the reception level observed in the reference frequency band.

[0008] A third disclosure relates to a wireless communication system having the following further features with respect to the wireless communication system according to the first or second disclosure. The wireless communication system according to the third disclosure further includes one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals. Each of the one or more second spectrum analyzers is configured to execute a process of monitoring the second usage status of surrounding frequency channels. Each of the one or more wireless terminals is configured to execute a process of acquiring the second usage status from the second spectrum analyzer provided in the vicinity and a process of notifying the wireless base station of the second usage status. The channel selection process includes selecting the communication channel according to the second usage status.

[0009] A fourth disclosure relates to a wireless communication system having the following further features with respect to the wireless communication system according to the first or second disclosure. The wireless communication system according to the fourth disclosure further includes one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals. Each of the one or more second spectrum analyzers is configured to execute a process of monitoring the second usage status of surrounding frequency channels in response to a second request received from a nearby wireless terminal. Each of the one or more wireless terminals is configured to execute a process of transmitting the second request to the second spectrum analyzer provided in the vicinity upon receiving a third request from the wireless base station, a process of obtaining the second usage status from the second spectrum analyzer provided in the vicinity, and a process of notifying the wireless base station of the second usage status. The wireless base station is further configured to execute a process of transmitting the third request to the one or more wireless terminals at the predetermined timing. And the channel selection process includes selecting the communication channel according to the second usage status.

[0010] A fifth disclosure relates to a wireless communication system further having the following features with respect to the wireless communication system according to any one of the first to fourth disclosures. The wireless base station is further configured to execute a process of storing the first usage status during a predetermined period in a storage device, and a process of determining a priority channel to be preferentially used based on the first usage status during the predetermined period. And the channel selection process includes preferentially selecting the priority channel as the communication channel.

[0011] A sixth disclosure relates to a wireless communication system further having the following features with respect to the wireless communication system according to any one of the first, second, or fifth disclosures. The wireless communication system according to the sixth disclosure further includes one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals. Each of the one or more second spectrum analyzers is configured to execute a process of monitoring the second usage status of surrounding frequency channels. Each of the one or more wireless terminals is configured to execute a process of obtaining the second usage status from the second spectrum analyzer provided in the vicinity, and a process of determining the wireless base station that performs communication according to the second usage status.

[0012] The seventh disclosure relates to a method for selecting a communication channel of a radio base station that communicates with one or more radio terminals. Here, a spectrum analyzer is provided in the vicinity of the radio base station, and the spectrum analyzer is configured to execute a process of monitoring the usage status of surrounding frequency channels upon receiving a request. The communication channel selection method according to the seventh disclosure includes transmitting the request to the spectrum analyzer at a predetermined timing, obtaining the usage status from the spectrum analyzer, and selecting a communication channel through which the radio base station communicates according to the usage status.

[0013] The eighth disclosure relates to a radio base station that communicates with one or more radio terminals. Here, a spectrum analyzer is provided in the vicinity of the radio base station, and the spectrum analyzer is configured to execute a process of monitoring the usage status of surrounding frequency channels upon receiving a request from the radio base station. The radio base station is configured to execute a process of transmitting the request to the spectrum analyzer at a predetermined timing, a process of obtaining the usage status from the spectrum analyzer, and a process of selecting a communication channel through which communication is performed according to the usage status.

Advantages of the Invention

[0014] According to the present disclosure, a radio base station transmits a first request to a spectrum analyzer at a predetermined timing. The first spectrum analyzer executes a monitoring process of monitoring a first usage status upon receiving the first request. Then, the radio base station obtains the first usage status from the first spectrum analyzer and selects a communication channel according to the first usage status. As a result, the radio base station does not need to perform a scan to grasp the usage status of surrounding frequency channels. Subsequently, it is possible to select a communication channel that avoids interference with communication in other systems without stopping transmission and reception by communication in the wireless communication system.

Brief Description of the Drawings

[0015]

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Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, when referring to numbers such as the number, quantity, amount, range, etc. of each element in the following embodiments, unless otherwise specified or unless the number is clearly specified in principle, the idea according to the present disclosure is not limited to the mentioned number. Also, the configurations and the like described in the following embodiments are not necessarily essential to the idea according to the present disclosure, unless otherwise specified or unless clearly specified thereto in principle. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description is appropriately simplified or omitted.

[0017] 1. First Embodiment 1-1. Outline FIG. 1 is a conceptual diagram for explaining the outline of the wireless communication system 10. The wireless communication system 10 includes a radio base station 100 that communicates with one or more wireless terminals 200 (for example, mobile communication terminals such as smartphones). The radio base station 100 communicates with one or more wireless terminals 200 using a communication channel selected from a plurality of frequency channels. For example, in the 2.4 GHz band of IEEE 802.11, a communication channel is selected from 14 frequency channels with a bandwidth of 22 MHz.

[0018] Here, it is assumed that the frequency band in which the wireless communication system 10 communicates is shared with another wireless communication system 20 (hereinafter, also simply referred to as "other system 20"). For this reason, there is a possibility that communication in the other system 20 interferes with communication in the wireless communication system 10.

[0019] In order to avoid interference from communication in the other system 20, it is required not to select a frequency channel that is in use or has a high usage frequency in the other system as a communication channel. For this, it is necessary to grasp the usage status of the surrounding frequency channels.

[0020] When the radio base station 100 performs a frequency scan, it will receive and observe surrounding radio signals, so communication with one or more radio terminals 200 will be stopped. FIG. 2 is a conceptual diagram showing the operation of the radio base station 100 when the radio base station 100 performs a frequency scan. FIG. 2 shows the time points of the operation (circles) of the radio base station 100 and the communication status (arrows) with one or more radio terminals 200 along the time axis.

[0021] In FIG. 2, the radio base station 100 checks a predetermined trigger at time t1 and starts a frequency scan for a plurality of frequency channel candidates. Here, the predetermined trigger is detecting deterioration in the communication quality of the current communication channel or the timer activating (for example, every predetermined period or after a predetermined time has elapsed). When the radio base station 100 starts the frequency scan, communication with one or more radio terminals 200 is stopped. After that, the radio base station 100 ends the frequency scan at time t2 and checks the usage status of the surrounding frequency channels from the scan results. Then, the radio base station 100 switches the communication channel according to the usage status of the surrounding frequency channels and resumes communication with one or more radio terminals 200.

[0022] Note that the usage status is, for example, the reception level for each frequency channel or frequency of the surrounding radio signals.

[0023] Thus, while the frequency scan is being performed, the radio base station 100 will stop communicating with one or more radio terminals 200. Consequently, transmission and reception by communication in the radio communication system 10 will stop.

[0024] Therefore, in the radio communication system 10 according to the first embodiment, a spectrum analyzer (first spectrum analyzer) is provided near the radio base station 100. FIG. 3 is a conceptual diagram for explaining the outline of the radio communication system 10 according to the first embodiment. As shown in FIG. 3, in the radio communication system 10 according to the first embodiment, a spectrum analyzer 110 is provided near the radio base station 100.

[0025] The spectrum analyzer 110 is configured to execute a monitoring process of receiving a request (hereinafter, also referred to as "first request") from the radio base station 100 and performing a frequency scan of surrounding radio signals to monitor the usage status of surrounding frequency channels (hereinafter, also referred to as "first usage status"). Here, the first request includes a specification of the frequency range for performing the scan. Then, the spectrum analyzer 110 performs a scan for the frequency range specified in the first request. Further, the first request may include a specification of the resolution bandwidth (RBW). Note that the spectrum analyzer 110 may be a simple spectrum analyzer.

[0026] When the radio base station 100 according to the first embodiment confirms a predetermined opportunity, it transmits a first request to the spectrum analyzer 110. On the other hand, in the radio base station 100, a frequency scan is not performed.

[0027] FIG. 4 is a conceptual diagram showing the operations of the radio base station 100 and the spectrum analyzer 110 according to the first embodiment. FIG. 4 shows a diagram similar to FIG. 2. In FIG. 4, the radio base station 100 checks a predetermined opportunity at time t1 and transmits a first request to the spectrum analyzer 110. Here, since the radio base station 100 does not perform frequency scanning, the radio base station 100 continues communication with one or more radio terminals 200.

[0028] On the other hand, upon receiving the first request from the radio base station 100, the spectrum analyzer 110 starts frequency scanning. Thereafter, the spectrum analyzer 110 ends the frequency scanning at time t2 and notifies the radio base station 100 of the first usage status as a response to the first request. Here, the first usage status includes information on the time when the scan was performed. Further, the first usage status may include usage statuses for a plurality of times. In this case, the spectrum analyzer 110 performs frequency scanning at a plurality of times.

[0029] The radio base station 100 acquires the first usage status from the spectrum analyzer 110 and executes a process of selecting and switching a communication channel according to the first usage status (hereinafter, also referred to as "channel selection process"). However, in the channel selection process, if the current communication channel is the most appropriate from the first usage status, switching may not be performed. Switching of the communication channel can also be described as "frequency switching" of the communication channel. Here, the radio base station 100 is configured not to consider the information of the radio signals transmitted and received by the radio base station 100 itself appearing in the first usage status. For example, when switching the communication channel according to the first usage status, the radio base station 100 is configured to cancel the reception level of the frequency band of the radio signals transmitted and received by the radio base station 100 itself from the reception level given in the first usage status. Thereby, the radio base station 100 can extract the usage status of the frequency channel due to the communication of the other system 20 from the first usage status acquired from the spectrum analyzer 110.

[0030] Thus, the radio base station 100 according to the first embodiment does not need to perform a scan to grasp the usage status of surrounding frequency channels. That is, the radio base station 100 according to the first embodiment does not need to stop communication with one or more radio terminals 200. Consequently, in the radio communication system 10, transmission and reception by communication do not stop.

[0031] Note that the spectrum analyzer 110 may be configured to perform a scan periodically and notify the radio base station 100 of the first usage status periodically after receiving the first request from the radio base station 100.

[0032] 1-2. Configuration Hereinafter, the configurations of the radio base station 100 and the spectrum analyzer 110 according to the first embodiment will be described. FIG. 5 is a block diagram showing the schematic configurations of the radio base station 100 and the spectrum analyzer 110 according to the first embodiment.

[0033] The radio base station 100 includes an information storage unit 101, a control unit 102, a radio unit 103, and an interface unit 104. The control unit 102 is configured to be able to transmit and receive information with the information storage unit 101, the radio unit 103, and the interface unit 104. For example, they are electrically connected via a cable.

[0034] The information storage unit 101 is a storage device that stores a control program executable by the control unit 102 and control information necessary for the processing executed by the control unit 102. The information storage unit 101 is, for example, a volatile memory, a non-volatile memory, an HDD, an SSD, or the like. Information acquired by the radio base station 100 is stored in the information storage unit 101 as control information.

[0035] The control program stored in the information storage unit 101 includes a program related to the process of transmitting and receiving wireless signals via the wireless unit 103. It also includes programs related to the process of transmitting the first request and programs related to channel selection processing, etc. Examples of the control information stored in the information storage unit 101 include the information on the first usage status obtained from the spectrum analyzer 110 and parameter information related to the control program.

[0036] The control unit 102 reads out the control program and the control information from the information storage unit 101, and executes the process according to the control program based on the control information. Thereby, the transmission and reception of wireless signals via the wireless unit 103 are realized. For example, the control unit 102 transmits the data to be transmitted as a transmission signal according to a predetermined communication protocol to the wireless unit 103. Further, data is extracted from the received signal received by the wireless unit 103 according to a predetermined communication protocol. The control unit 102 is typically a processor.

[0037] Also, by the control unit 102 executing the process according to the control program, the process of transmitting the first request and the channel selection process are realized.

[0038] The wireless unit 103 transmits and receives wireless signals according to the process by the control unit 102. For example, it transmits the transmission signal obtained from the control unit 102 as a wireless signal. Further, it detects the surrounding wireless signals and obtains them as received signals. The wireless unit 103 is configured to transmit, for example, a modulated signal modulated by the transmission signal as a radio wave by an antenna, and demodulate the radio wave received by the antenna to obtain a received signal.

[0039] The interface unit 104 transmits and receives information with an external device according to the process by the control unit 102. In particular, the interface unit 104 transmits and receives information with the spectrum analyzer 110. The transmission of the first request and the acquisition of the first usage status are performed via the interface unit 104.

[0040] The spectrum analyzer 110 includes an information storage unit 111, a control unit 112, a wireless unit 113, and an interface unit 114. The control unit 112 is configured to be able to transmit and receive information with the information storage unit 111, the wireless unit 113, and the interface unit 114.

[0041] The information storage unit 111 is a storage device that stores a control program executable by the control unit 112 and control information necessary for the processing executed by the control unit 112. The information acquired by the spectrum analyzer 110 is stored in the information storage unit 111 as control information.

[0042] The control program stored in the information storage unit 111 includes a program related to the monitoring process. Examples of the control information stored in the information storage unit 111 include information on the first request acquired from the radio base station 100 and parameter information related to the control program.

[0043] The control unit 112 reads the control program and control information from the information storage unit 111 and executes the processing according to the control program based on the control information. Thereby, the monitoring process is realized. The control unit 112 is typically a processor.

[0044] The wireless unit 113 detects surrounding wireless signals and acquires them as received signals. The control unit 112 detects the reception level of the surrounding wireless signals from the received signals acquired by the wireless unit 113 by executing the monitoring process.

[0045] The interface unit 114 transmits and receives information with an external device according to the processing by the control unit 112. In particular, the interface unit 114 transmits and receives information with the radio base station 100. The transmission of the first usage status and the acquisition of the first request are performed via the interface unit 114.

[0046] 1-3. Communication Channel Selection Method Hereinafter, with reference to FIG. 6, a communication channel selection method for the radio base station 100 realized by the radio communication system 10 according to the first embodiment will be described. The flowchart shown in FIG. 6 is started, for example, by the activation of the radio base station 100. Also, each process of the flowchart is executed at every predetermined processing cycle.

[0047] In step S100, the radio base station 100 determines whether a predetermined trigger has been confirmed. The predetermined trigger may be preferably determined according to the environment to which the radio communication system 10 according to the first embodiment is applied.

[0048] When a predetermined trigger is confirmed (step S100; Yes), the process proceeds to step S110. When a predetermined trigger is not confirmed (step S100; No), the current communication channel is maintained in the current process, and step S100 is executed again at the next process execution.

[0049] In step S110, the radio base station 100 transmits a first request to the spectrum analyzer 110.

[0050] After step S110, the process proceeds to step S120.

[0051] In step S120, the radio base station 100 receives, from the spectrum analyzer 110, a response to the first request transmitted in step S110. Here, the radio base station 100 receives a first usage status as the response.

[0052] After step S120, the process proceeds to step S130.

[0053] In step S130, the radio base station 100 determines whether it is necessary to switch the communication channel based on the first usage status obtained in step S120. For example, the radio base station 100 estimates the level of interference from other systems 20 from the reception levels of candidate frequency channels (however, the reception level of the radio signal transmitted and received by the radio base station 100 itself is canceled). Then, when there is a frequency channel with a lower interference level than the current communication channel, it is determined that it is necessary to switch the communication channel.

[0054] When it is determined that it is necessary to switch the communication channel (step S130; Yes), the process proceeds to step S140. When it is determined that it is not necessary to switch the communication channel (step S130; No), the current communication channel is maintained in this processing, and step S100 is executed again when the next processing is executed.

[0055] In step S140 (channel selection process), the radio base station 100 selects and switches the communication channel according to the first usage status obtained in step S120.

[0056] After step S140, this processing ends, and step S100 is executed again when the next processing is executed.

[0057] 1-4. Effects As described above, according to the first embodiment, the radio base station 100 transmits a first request to the spectrum analyzer 110 at a predetermined opportunity. The spectrum analyzer 110 executes a monitoring process of monitoring the first usage status in response to the first request. Then, the radio base station 100 obtains the first usage status from the spectrum analyzer 110 and selects a communication channel according to the first usage status. Thereby, the radio base station 100 does not need to perform a scan to grasp the usage status of surrounding frequency channels. Subsequently, it is possible to select a communication channel that avoids interference with communication in other systems 20 without stopping transmission and reception by communication in the radio communication system 10.

[0058] Note that, in the above description, one radio base station 100 has been described, but the same applies to the case where the radio communication system 10 includes a plurality of radio base stations 100. In this case, the above-described configuration and processing may be applied to each of the plurality of radio base stations 100.

[0059] 2. Second Embodiment Hereinafter, the second embodiment will be described. However, in the following description, differences from the first embodiment will be described, and content overlapping with the above-described matters will be omitted as appropriate.

[0060] 2-1. Overview The configuration of the radio communication system 10 according to the second embodiment is the same as that of the first embodiment shown in FIG. 3. However, the second embodiment has the following features with respect to the first embodiment. The radio base station 100 is configured to further execute a process of transmitting information (hereinafter also referred to as "calibration information") for designating a reference frequency band with a reception level of zero with respect to the reception level at a predetermined time to the spectrum analyzer 110. Further, the spectrum analyzer 110 is configured to further execute a process of setting, as a reference error, the reception level of the reference frequency band observed at a predetermined time in response to the calibration information acquired from the radio base station 100. And the monitoring process executed by the spectrum analyzer 110 includes subtracting the set reference error from the reception level observed in the reference frequency band.

[0061] FIG. 7 is a conceptual diagram showing characteristic operations of the radio base station 100 and the spectrum analyzer 110 according to the second embodiment. FIG. 7 shows the same figure as FIG. 2. In FIG. 7, it is assumed that the radio base station 100 measures the reception level with respect to the frequency as shown in the figure at time t1. Also, it is assumed that a frequency scan by the spectrum analyzer 110 is being performed at time t1. Here, in the example shown in FIG. 7, the reception level measured by the radio base station 100 at time t1 is zero in the frequency band from f1 to f2.

[0062] Next, at time t2, the radio base station 100 transmits calibration information to the spectrum analyzer 110. In the example shown in FIG. 7, the calibration information designates, as a reference frequency band, a frequency band from f1 to f2 or higher with respect to the reception level measured by the radio base station 100 at time t1.

[0063] Next, upon receiving the calibration information acquired from the radio base station 100, the spectrum analyzer 110 sets a reference error. In setting the reference error, the spectrum analyzer 110 refers to the scan history performed at time t1. Then, the reception level in the reference frequency band in the scan history is set as the reference error. In the example shown in FIG. 7, Se, which is the reception level in the frequency band from f1 to f2 or higher in the scan history, is set as the reception error. Thereafter, at time t3, the spectrum analyzer 110 responds to the radio base station 100 that the setting of the reference error has been performed.

[0064] When the reference error is set, in the monitoring process, the spectrum analyzer 110 operates to subtract the reference error from the reception level observed in the reference frequency band. That is, the radio base station 100 acquires, as the first usage status, the reception level after subtracting the reference error as an answer to the first request. In the example shown in FIG. 7, at time t4, the spectrum analyzer 110 notifies the radio base station 100 of the first usage status as an answer to the first request. Here, in the first usage status notified by the spectrum analyzer 110, the reception level in the frequency band from f1 to f2 or higher becomes Rv obtained by subtracting the reference error Se.

[0065] As described above, in the second embodiment, calibration is performed on the first usage status monitored by the spectrum analyzer 110 according to the calibration information transmitted by the radio base station 100. Note that the radio base station 100 may be configured to transmit calibration information under specific conditions. For example, the radio base station 100 is configured to transmit calibration information upon detecting a frequency band where the reception level becomes zero. Alternatively, a reference frequency band is stored as control information, and the radio base station 100 is configured to transmit calibration information upon detecting that the reception level of the reference frequency band becomes zero. Also, the calibration may be performed in parallel with the normal operation.

[0066] 2-2. Configuration The configurations of the radio base station 100 and the spectrum analyzer 110 according to the second embodiment may be the same as those of the first embodiment shown in FIG. 5. However, the control programs stored in the information storage unit 101 and the information storage unit 111 include programs related to calibration. Also, the control information stored in the information storage unit 111 includes the history of frequency scans. Then, each of the control unit 102 and the control unit 112 reads the control program and the control information from the information storage unit 101 and the information storage unit 111 respectively, and executes the processing according to the control program based on the control information, thereby realizing the processing related to calibration.

[0067] 2-3. Calibration Hereinafter, with reference to FIGS. 8 and 9, the processing related to calibration executed in the wireless communication system 10 according to the second embodiment will be described. Here, FIG. 8 shows the processing executed in the radio base station 100, and FIG. 9 shows the processing executed in the spectrum analyzer 110.

[0068] First, the processing executed in the radio base station 100 will be described with reference to FIG. 8. The flowchart shown in FIG. 8 starts, for example, when the radio base station 100 is activated. Also, each process in the flowchart is executed at every predetermined processing cycle.

[0069] In step S200, the radio base station 100 determines the reference frequency and timing with a reception level of zero. This is performed, for example, by detecting that the reception level has become zero in a specific frequency band.

[0070] If there is a determination of the reference frequency and timing (step S200; Yes), the process proceeds to step S201. If there is no determination of the reference frequency and timing (step S200; No), calibration is not performed in this process, and step S200 is executed again when the next process is executed.

[0071] In step S201, the radio base station 100 notifies the spectrum analyzer 110 by specifying the frequency and timing determined in step S200. This is performed by the radio base station 100 transmitting calibration information to the spectrum analyzer 110. That is, the calibration information includes the specification of the frequency (reference frequency band) and timing (predetermined time) determined in step S200.

[0072] After step S201, the process proceeds to step S202.

[0073] In step S202, the radio base station 100 receives a response to the notification in step S201. Thereby, the radio base station 100 confirms that the calibration has been completed in the spectrum analyzer 110.

[0074] After step S202, this process ends, and step S200 is executed again when the next process is executed.

[0075] Next, the process executed in the spectrum analyzer 110 will be described with reference to FIG. 9. The flowchart shown in FIG. 9 starts, for example, by starting the spectrum analyzer 110. Each process of the flowchart is executed at each predetermined processing cycle.

[0076] In step S210, the spectrum analyzer 110 determines whether there is a notification of reference frequency and timing with a reception level of zero from the radio base station 100 (the notification in step S201 shown in FIG. 8). This is determined based on whether the spectrum analyzer 110 has acquired calibration information from the radio base station 100.

[0077] If the spectrum analyzer 110 has acquired calibration information (step S210; Yes), the process proceeds to step S211. If the spectrum analyzer 110 has not acquired calibration information (step S210; No), calibration is not performed in this process, and step S210 is executed again when the next process is executed.

[0078] In step S211, the spectrum analyzer 110 confirms the reception level of the frequency and timing notified in step S210 by searching the scan history and sets a reference error. This is done by searching the scan history stored as control information according to the time and reference frequency band specified in the calibration information.

[0079] After step S211, the process proceeds to step S212.

[0080] In step S212, the spectrum analyzer 110 transmits a response indicating that the calibration of the radio base station 100 has been completed.

[0081] After step S212, this process ends, and step S210 is executed again when the next process is executed.

[0082] 2-4. Effects As described above, according to the second embodiment, calibration is performed on the first usage situation monitored by the spectrum analyzer 110 in accordance with the calibration information transmitted by the radio base station 100. Thereby, the deviation related to the measurement between the radio base station 100 and the spectrum analyzer 110 can be adjusted. Subsequently, it is possible to suppress the radio base station 100 from selecting an inappropriate communication channel due to the measurement deviation.

[0083] 3. Third Embodiment Hereinafter, the third embodiment will be described. However, in the following description, the differences from the first embodiment will be described, and the contents overlapping with the above-described matters will be omitted as appropriate.

[0084] 3-1. Overview The wireless communication system 10 according to the third embodiment further includes one or more spectrum analyzers (second spectrum analyzers) provided in the vicinity of each of one or more wireless terminals 200 with respect to the wireless communication system 10 according to the first embodiment. FIG. 10 is a conceptual diagram for explaining the overview of the wireless communication system 10 according to the third embodiment. In the example shown in FIG. 10, the wireless communication system 10 includes two wireless terminals 200 (#1 and #2). And spectrum analyzers 210 (#1 and #2) are provided in the vicinity of each of the two wireless terminals 200.

[0085] Each of the spectrum analyzers 210 is configured to perform a frequency scan and execute a process of monitoring the usage situation of surrounding frequency channels (hereinafter, also referred to as "second usage situation"). Each of the wireless terminals 200 acquires the second usage situation from the spectrum analyzer 210 provided in the vicinity and notifies the radio base station 100 of the second usage situation. Note that each of the spectrum analyzers 210 may be a simple spectrum analyzer.

[0086] In the third embodiment, the channel selection process executed by the radio base station 100 includes selecting a communication channel according to the second usage status. Thereby, when selecting a communication channel, the radio base station 100 can consider the usage status (the first usage status) of the frequency channels around the radio base station 100 and the usage status (the second usage status) of the frequency channels around each of one or more radio terminals 200. That is, it is possible to avoid interference in communication not only in another system 20 (#1) close to the radio base station 100 but also in another system 20 (#2) close to one or more radio terminals 200.

[0087] FIG. 11 is a conceptual diagram showing the operations of the radio base station 100, the spectrum analyzer 110, the radio terminal 200, and the spectrum analyzer 210 according to the third embodiment. FIG. 11 shows a diagram similar to FIG. 2. In FIG. 11, the spectrum analyzer 110 receives a first request from the radio base station 100 and continuously performs a frequency scan, and shows a case where the first usage status is periodically notified to the radio base station 100 as a response to the first request.

[0088] As shown in FIG. 11, each of the radio terminals 200 periodically acquires the second usage status from a spectrum analyzer 210 provided in the vicinity. Further, the acquired second usage status is notified to the radio base station 100. Then, the radio base station 100 selects and switches a communication channel according to the first usage status and the second usage status in the channel selection process.

[0089] Note that the third embodiment can also be applied to the second embodiment.

[0090] 3-2. Configuration The configurations of the wireless base station 100 and the spectrum analyzer 110 according to the third embodiment may be the same as those of the first embodiment shown in FIG. 5. However, the control information stored in the information storage unit 101 includes the second usage status acquired from one or more wireless terminals 200. Hereinafter, the configurations of the wireless terminal 200 and the spectrum analyzer 210 according to the third embodiment will be described. FIG. 12 is a block diagram showing a schematic configuration of the wireless terminal 200 and the spectrum analyzer 210 according to the third embodiment.

[0091] The wireless terminal 200 includes an information storage unit 201, a control unit 202, a wireless unit 203, and an interface unit 204. The control unit 202 is configured to be able to transmit and receive information to and from the information storage unit 201, the wireless unit 203, and the interface unit 204.

[0092] The information storage unit 201 is a storage device that stores a control program executable by the control unit 202 and control information necessary for the processing executed by the control unit 202. The information acquired by the wireless terminal 200 is stored in the information storage unit 201 as control information.

[0093] The control program stored in the information storage unit 201 includes a program related to the process of transmitting and receiving wireless signals via the wireless unit 203. Examples of the control information stored in the information storage unit 201 include parameter information related to the control program.

[0094] The control unit 202 reads the control program and control information from the information storage unit 201, and executes the processing according to the control program based on the control information. Thereby, the transmission and reception of wireless signals via the wireless unit 203 are realized. In particular, the notification of the second usage status acquired from the spectrum analyzer 210 is realized. The control unit 202 is typically a processor.

[0095] The wireless unit 203 transmits and receives wireless signals according to the processing by the control unit 202.

[0096] The interface unit 204 transmits and receives information with an external device according to the processing by the control unit 202. In particular, the interface unit 204 transmits and receives information with the spectrum analyzer 210. The acquisition of the second usage status is performed via the interface unit 204.

[0097] The spectrum analyzer 210 includes an information storage unit 211, a control unit 212, a wireless unit 213, and an interface unit 214. The control unit 212 is configured to be able to transmit and receive information with the information storage unit 211, the wireless unit 213, and the interface unit 214.

[0098] The information storage unit 211 is a storage device that stores a control program executable by the control unit 212 and control information necessary for the processing executed by the control unit 212. The information acquired by the spectrum analyzer 210 is stored in the information storage unit 211 as control information.

[0099] The program stored in the information storage unit 211 includes a program related to the process of monitoring the second usage status. Examples of the control information stored in the information storage unit 211 include parameter information related to the control program.

[0100] The control unit 212 reads the control program and control information from the information storage unit 211, and executes the process according to the control program based on the control information. Thereby, the process of monitoring the second usage status is realized. The control unit 212 is typically a processor.

[0101] The wireless unit 213 detects surrounding wireless signals and acquires them as received signals. The control unit 212 detects the reception level of the surrounding wireless signals from the received signals acquired by the wireless unit 213 by executing the process of monitoring the second usage status.

[0102] The interface unit 214 transmits and receives information to and from an external device according to the processing by the control unit 212. In particular, the interface unit 214 transmits and receives information to and from the wireless terminal 200. The transmission of the second usage status is performed via the interface unit 214.

[0103] 3-3. Communication Channel Selection Method Hereinafter, with reference to FIGS. 13 and 14, a communication channel selection method of the radio base station 100 realized by the radio communication system 10 according to the third embodiment will be described.

[0104] First, with reference to FIG. 13, the processing executed in the radio base station 100 will be described. The flowchart shown in FIG. 8 starts, for example, when the radio base station 100 is activated. Each process of the flowchart is executed at every predetermined processing cycle.

[0105] In step S300, the radio base station 100 determines whether it has received a notification regarding the second usage status from the subordinate wireless terminal 200 (the wireless terminal 200 performing communication).

[0106] If a notification is received from the subordinate wireless terminal 200 (step S300; Yes), the process proceeds to step S302. If a notification has not been received from the subordinate wireless terminal 200 (step S300; No), the process proceeds to step S301.

[0107] In step S301, the radio base station 100 determines whether it has received a notification regarding the first usage status from the spectrum analyzer 110.

[0108] If a notification is received from the spectrum analyzer 110 (step S301; Yes), the process proceeds to step S302. If a notification has not been received from the spectrum analyzer 110 (step S301; No), the current communication channel is maintained in the current process, and step S300 is executed again at the next process execution.

[0109] In step S302, the radio base station 100 determines whether it is necessary to switch the communication channel. Here, when receiving a notification from the subordinate radio terminal 200 (step S300; Yes), it determines whether it is necessary to switch the communication channel based on the second usage status. On the other hand, when receiving a notification from the spectrum analyzer 110 (step S301; Yes), it determines whether it is necessary to switch the communication channel based on the first usage status.

[0110] When it is determined that the communication channel needs to be switched (step S302; Yes), the process proceeds to step S303. When it is determined that the communication channel does not need to be switched (step S302; No), the current communication channel is maintained in this process, and step S300 is executed again when the next process is executed.

[0111] In step S303 (channel selection process), the radio base station 100 selects and switches the communication channel according to the second usage status obtained in step S300 or the first usage status obtained in step S301.

[0112] After step S303, this process ends, and step S300 is executed again when the next process is executed.

[0113] Next, referring to FIG. 14, the process executed in each of one or more radio terminals 200 will be described. The flowchart shown in FIG. 14 starts, for example, when the radio terminal 200 is activated. Also, each process of the flowchart is executed for each processing cycle.

[0114] In step S310, the radio terminal 200 determines whether it is a timing to periodically transmit the second usage status to the radio base station 100. Here, the timing of periodic transmission is, for example, that a timer notifying a predetermined period has activated. Note that the radio terminal 200 periodically acquires the second usage status from the spectrum analyzer 210 provided in the vicinity.

[0115] When it is a timing for periodic transmission (step S310; Yes), the process proceeds to step S311. When it is not a timing for periodic transmission (step S310; No), step S310 is executed again at the time of the next process execution without notifying the radio base station 100 of the second usage status in the current process.

[0116] In step S311, the wireless terminal 200 notifies the radio base station 100 of the second usage status.

[0117] After step S311, the current process ends, and step S310 is executed again at the time of the next process execution.

[0118] 3-4. Effects As described above, according to the third embodiment, the radio base station 100 acquires the second usage status for each of one or more wireless terminals 200. And the channel selection process executed by the radio base station 100 includes selecting a communication channel according to the second usage status. Thereby, interference of communication in another system 20 close to one or more wireless terminals 200 can be avoided. Consequently, the quality of communication from the radio base station 100 to the wireless terminal 200 can be ensured.

[0119] 4. Fourth Embodiment Hereinafter, the fourth embodiment will be described. However, in the following description, the differences from the third embodiment will be described, and the contents overlapping with the matters described above are omitted as appropriate.

[0120] 4-1. Overview The configuration of the wireless communication system 10 according to the fourth embodiment is the same as that of the third embodiment shown in FIG. 10. However, the spectrum analyzer 210 according to the fourth embodiment is configured to receive a request (hereinafter, also referred to as "second request") from a nearby wireless terminal 200, perform a scan of the frequencies of surrounding wireless signals, and execute a process of monitoring the second usage status. Further, the wireless terminal 200 according to the fourth embodiment is configured to receive a request (hereinafter, also referred to as "third request") from the wireless base station 100 and execute a process of transmitting the second request to the spectrum analyzer 210 provided in the vicinity. Furthermore, the wireless base station 100 according to the fourth embodiment is configured to execute a process of transmitting the third request to one or more wireless terminals 200 on a predetermined occasion.

[0121] FIG. 15 is a conceptual diagram showing the operations of the wireless base station 100, the spectrum analyzer 110, the wireless terminal 200, and the spectrum analyzer 210 according to the fourth embodiment. FIG. 15 shows a diagram similar to FIG. 2.

[0122] In FIG. 15, the wireless base station 100 detects deterioration of communication quality (confirms a predetermined occasion) at time t1 and transmits a notification signal (third request) to each of the wireless terminals 200. Also, similar to the first embodiment, a first request is transmitted to the spectrum analyzer 110. Each of the wireless terminals 200 receives the third request from the wireless base station 100, transmits the second request to the spectrum analyzer 210 provided in the vicinity, and acquires the second usage status as a response to the second request. Thereafter, each of the wireless terminals 200 notifies the wireless base station 100 of the second usage status. As a result, the wireless base station 100 acquires the second usage status from each of the wireless terminals 200. Also, similar to the first embodiment, the wireless base station 100 acquires the first usage status from the spectrum analyzer 110. Then, the wireless base station 100 selects and switches the communication channel according to the first usage status and the second usage status.

[0123] 4-2. Configuration The configurations of the radio base station 100 and the spectrum analyzer 110 according to the fourth embodiment may be the same as those of the first embodiment shown in FIG. 5. However, the control program stored in the information storage unit 101 includes a program related to the process of transmitting the third request. Then, the control unit 102 reads the control program and control information from the information storage unit 101, and executes the process according to the control program based on the control information, thereby realizing the process of transmitting the third request. Note that the third request is transmitted via the radio unit 103. The radio terminal 200 receives the third request via the radio unit 203.

[0124] Furthermore, the configurations of the radio terminal 200 and the spectrum analyzer 210 according to the fourth embodiment may be the same as those of the third embodiment shown in FIG. 12. However, the control program stored in the information storage unit 201 includes a program related to the process of transmitting the second request. Then, the control unit 202 reads the control program and control information from the information storage unit 201, and executes the process according to the control program based on the control information, thereby realizing the process of transmitting the second request. Note that the second request is transmitted via the interface unit 204. The spectrum analyzer 210 receives the second request via the interface unit 214.

[0125] 4-3. Communication Channel Selection Method Hereinafter, with reference to FIG. 16, a communication channel selection method of the radio base station 100 realized by the radio communication system 10 according to the fourth embodiment will be described. The flowchart shown in FIG. 16 starts, for example, when the radio base station 100 is activated. Each process of the flowchart is executed at every predetermined processing cycle.

[0126] In step S400, the radio base station 100 determines whether it is an opportunity to inquire of the radio terminal 200. That is, it determines whether a predetermined opportunity (such as detection of deterioration in communication quality or operation of a timer) has been confirmed.

[0127] If it is a trigger for an inquiry (step S400; Yes), the process proceeds to step S401. If it is not a trigger for an inquiry (step S400; No), the current communication channel is maintained in this processing, and step S400 is executed again at the next processing execution.

[0128] In step S401, the radio base station 100 transmits a notification signal (third request) to the subordinate radio terminal 200. Also, the radio base station 100 makes an inquiry about the first usage status (transmission of the first request) to the spectrum analyzer 110 provided in the vicinity.

[0129] After step S401, the process proceeds to step S402.

[0130] In step S402, the radio base station 100 receives the notification signal and the response to the inquiry from the radio terminal 200 and the spectrum analyzer 110. Thereby, the radio base station 100 acquires the second usage status and the first usage status.

[0131] After step S402, the process proceeds to step S403.

[0132] In step S403, the radio base station 100 determines whether it is necessary to switch the communication channel based on the first usage status and the second usage status.

[0133] When it is determined that communication channel switching is necessary (step S403; Yes), the process proceeds to step S404. When it is determined that communication channel switching is not necessary (step S403; No), the current communication channel is maintained in this processing, and step S400 is executed again at the next processing execution.

[0134] In step S404 (channel selection process), the radio base station 100 selects and switches the communication channel according to the first usage status and the second usage status acquired in step S402.

[0135] After step S404, the current process ends, and step S400 is executed again when the next process is executed.

[0136] 4-4. Effect As described above, according to the fourth embodiment, each of the one or more spectrum analyzers 210 executes a process of monitoring the second usage status by receiving a second request from a nearby wireless terminal. Also, each of the one or more wireless terminals 200 transmits a second request to the spectrum analyzer 210 provided in the vicinity after receiving a third request from the wireless base station 100. Further, the wireless base station 100 transmits a third request to the one or more wireless terminals 200 when confirming a predetermined opportunity. Thereby, a frequency scan can be performed only when necessary, such as when detecting a deterioration in communication quality. Subsequently, it is possible to improve the efficiency of information collection and save power.

[0137] 5. Fifth Embodiment Hereinafter, the fifth embodiment will be described. However, in the following description, differences from the first embodiment will be described, and contents overlapping with those described above will be omitted as appropriate.

[0138] 5-1. Outline The configuration of the wireless communication system 10 according to the fifth embodiment is the same as that of the first embodiment shown in FIG. 3. However, the fifth embodiment has the following features with respect to the first embodiment. The wireless base station 100 stores the first usage status during a predetermined period in the information storage unit 101. Also, the wireless base station 100 executes a process of determining a frequency channel to be preferentially used (hereinafter, also referred to as "priority channel") based on the first usage status during a predetermined period. The priority channel can also be referred to as "priority frequency".

[0139] The determination of the priority channel is performed, for example, based on the usage rate of other system 20 for each communication channel. In this case, the radio base station 100 executes a process of estimating the usage rate of each frequency channel by other system 20 based on the first usage situation during a predetermined period (hereinafter, also referred to as "usage rate estimation process"). The usage rate is given, for example, by the temporal ratio during which a reception level equal to or higher than a predetermined value is observed. The usage rate can also be referred to as the "transmission time rate". FIG. 17 is a graph showing the usage rate of each frequency channel by other system 20. For example, when the usage rate shown in FIG. 17 is estimated by executing the usage rate estimation process, the radio base station 100 sets the frequency channel CH1 with the lowest usage rate as the priority channel. Further, the radio base station 100 may switch the priority channel according to the time zone. For example, based on the first usage situation during a day, the priority channel is determined for each time zone with a cycle of 24 hours, and the priority channel is switched according to the time zone within a day.

[0140] Then, the channel selection process executed by the radio base station 100 includes preferentially selecting the priority channel as the communication channel. For example, when it is determined that a communication channel needs to be switched, if there are a plurality of candidate frequency channels for the switching destination that include the priority channel, the priority channel is selected as the communication channel. Alternatively, when the level of interference with the current communication channel by other system 20 becomes greater than the level of interference with the priority channel, the priority channel is selected as the communication channel.

[0141] By determining the priority channel in this way, it is possible to grasp the long-term usage situation of the frequency channel and execute the communication channel selection process.

[0142] Note that the fifth embodiment can also be applied to the second to fourth embodiments. Here, when applying to the third or fourth embodiment, the radio base station 100 may be configured to store the second usage status during a predetermined period in the information storage unit 101. Further, the radio base station 100 may determine a priority channel based on the second usage status during a predetermined period. Note that when applying to the third or fourth embodiment, the configurations of the wireless terminal 200 and the spectrum analyzer 210 may be the same as those in the third or fourth embodiment.

[0143] 5-2. Configuration The configurations of the radio base station 100 and the spectrum analyzer 110 according to the fifth embodiment may be the same as those of the first embodiment shown in FIG. 5. However, the control program stored in the information storage unit 101 includes a program related to the determination of the priority channel. Further, the control information stored in the information storage unit 101 includes the first usage status during a predetermined period. Then, the control unit 102 reads the control program and the control information from the information storage unit 101, and executes the process according to the control program based on the control information, thereby realizing the process related to the determination of the priority channel.

[0144] 5-3. Communication Channel Selection Method Hereinafter, with reference to FIG. 18, the communication channel selection method of the radio base station 100 realized by the wireless communication system 10 according to the fifth embodiment will be described. The flowchart shown in FIG. 18 starts, for example, when the radio base station 100 is activated. Each process of the flowchart is executed at every predetermined processing cycle.

[0145] In step S500, the radio base station 100 determines whether there is a notification of the usage status (first usage status or second usage status) of the surrounding frequency channels from the spectrum analyzer 110 or the wireless terminal 200.

[0146] If there is a notification of the usage status of surrounding frequency channels (step S500; Yes), the process proceeds to step S501. If there is no notification of the usage status of surrounding frequency channels (step S500; No), the current communication channel is maintained in this process, and step S500 is executed again when the next process is executed.

[0147] In step S501, the radio base station 100 updates the estimation of the usage time ratio for each frequency channel by the other system 20. As a result, the usage status of the surrounding frequency channels acquired in step S500 is reflected in the estimation of the usage time ratio.

[0148] After step S501, the process proceeds to step S502.

[0149] In step S502, the radio base station 100 determines whether it is necessary to switch the communication channel. Here, the radio base station 100 may determine whether it is necessary to switch the communication channel based on the long-term usage status of the frequency channel by the other system 20. For example, upon receiving that the usage time ratio by the other system 20 for the current communication channel exceeds a predetermined threshold, it is determined that it is necessary to switch the communication channel.

[0150] When it is determined that it is necessary to switch the communication channel (step S502; Yes), the process proceeds to step S503. When it is determined that it is not necessary to switch the communication channel (step S502; No), the current communication channel is maintained in this process, and step S500 is executed again when the next process is executed.

[0151] In step S503 (channel selection process), the radio base station 100 selects and switches the communication channel according to the usage status of the frequency channel acquired in step S500. Here, the radio base station 100 determines the priority channel based on the usage time ratio updated in step S501, and preferentially selects the priority channel as the communication channel.

[0152] After step S503, the current process ends, and step S500 is executed again when the next process is executed.

[0153] 5-4. Effects As described above, according to the fifth embodiment, the radio base station 100 stores the first usage status during a predetermined period in the information storage unit 101. Further, a priority channel is determined based on the first usage status during a predetermined period. Then, the channel selection process executed by the radio base station 100 includes preferentially selecting the priority channel as a communication channel. Thereby, it is possible to grasp the long-term usage status of the frequency channel by the other system 20 and select a communication channel. Subsequently, it is possible to select an appropriate communication channel in accordance with the long-term usage status of the frequency channel.

[0154] Although the above description has been made for one radio base station 100, the same applies when the wireless communication system 10 includes a plurality of radio base stations 100. In this case, the priority channels may be configured so as not to overlap with each other among the plurality of radio base stations 100. FIG. 19 shows an example of determining a priority channel when the wireless communication system 10 includes two radio base stations 100 (#1 and #2). FIG. 19 shows the same graph as FIG. 17. In the example of FIG. 19, CH1 and CH2 with a small usage time ratio are determined as the priority channels of the radio base station 100 #1 and the radio base station 100 #2 so as not to overlap.

[0155] 5-5. Modification The wireless communication system 10 according to the fifth embodiment may adopt the following modified aspect.

[0156] The wireless communication system 10 according to the fifth embodiment may include an aggregation server, and the aggregation server may be configured to aggregate the location information and the first usage status during a predetermined period from each of the plurality of radio base stations 100. Then, the aggregation server may execute a process of determining the priority channel of each of the plurality of radio base stations 100. Here, the location information is, for example, coordinates indicating a location on a map.

[0157] FIG. 20 is a conceptual diagram for explaining the outline of the wireless communication system 10 according to the modified example. The wireless communication system 10 according to the modified example includes an aggregation server 300. The wireless communication system 10 according to the modified example also includes a plurality of radio base stations 100. In FIG. 20, two radio base stations 100, #1 and #2, are shown as the plurality of radio base stations 100.

[0158] Each of the plurality of radio base stations 100 and the aggregation server 300 are connected to a communication network 1 and transmit information to each other via the communication network 1. The communication network 1 is, for example, the Internet.

[0159] Each of the radio base stations 100 sequentially transmits the first usage status obtained from the spectrum analyzer 110 to the aggregation server 300 via the communication network 1. Each of the radio base stations 100 also transmits the location information to the aggregation server 300 via the communication network 1.

[0160] The aggregation server 300 sequentially acquires the first usage status from each of the radio base stations 100 via the communication network 1. The aggregation server 300 also acquires the location information from each of the radio base stations 100 via the communication network 1. Here, in the aggregation server 300, the location information and the first usage status are associated for each of the radio base stations 100. That is, it is managed so that the first usage status can be referred to with respect to the location information. Thereby, it is possible to grasp the usage status of frequency channels by other systems 20 over a wide range and for a long period.

[0161] Then, the aggregation server 300 executes a process of determining a priority channel for each of the plurality of radio base stations 100 based on the aggregated first usage status. Here, the aggregation server 300 transmits the determined priority channel to each of the plurality of radio base stations 100 via the communication network 1.

[0162] In the wireless communication system 10 according to the modification example as described above, the priority channel of each of the plurality of radio base stations 100 is specified by the aggregation server 300. Note that the aggregation server 300 may be configured to acquire the second usage status from the radio base station 100. Further, the aggregation server 300 may be configured to acquire the location information of the wireless terminal 200 for which the second usage status has been acquired, and associate the location information of the wireless terminal 200 with the second usage status. Then, the aggregation server 300 may determine the priority channel based on the second usage status during a predetermined period.

[0163] FIG. 21 is a block diagram showing a schematic configuration of the radio base station 100 and the spectrum analyzer 110 according to the modification example. The radio base station 100 according to the modification example further includes an NW interface unit 105. The control unit 102 is configured to be able to transmit and receive information to and from the NW interface unit 105.

[0164] The NW interface unit 105 transmits and receives information via the communication network 1 according to the processing by the control unit 102. In particular, information is transmitted and received to and from the aggregation server 300 via the NW interface unit 105.

[0165] The control program stored in the information storage unit 101 includes a process of transmitting the location information and the first usage status to the aggregation server 300 via the NW interface unit 105. The control information stored in the information storage unit 101 includes the location information of the radio base station 100. Then, the control unit 102 reads the control program and the control information from the information storage unit 101, and executes the process according to the control program based on the control information, thereby realizing the process of transmitting the location information and the first usage status to the aggregation server 300 via the NW interface unit 105.

[0166] FIG. 22 is a block diagram showing a schematic configuration of an aggregation server 300 according to a modified example. The aggregation server 300 includes an information storage unit 301, a control unit 302, and a NW interface unit 305. The control unit 302 is configured to be able to transmit and receive information to and from the information storage unit 301 and the NW interface unit 305.

[0167] The information storage unit 301 is a storage device that stores a control program executable by the control unit 302 and control information necessary for the processing executed by the control unit 302. Information acquired by the aggregation server 300 is stored in the information storage unit 301 as control information.

[0168] The control program stored in the information storage unit 301 includes a program related to transmission and reception of information via the NW interface unit and a program related to determination of a priority channel. Examples of the control information stored in the information storage unit 301 include position information and first usage status information acquired from each of the plurality of radio base stations 100 and parameter information related to the control program.

[0169] The control unit 302 reads the control program and control information from the information storage unit 301 and executes processing according to the control program based on the control information. Thereby, transmission and reception of information via the NW interface unit 305 are realized. In particular, the control unit 302 acquires the position information and the first usage status via the NW interface and stores the first usage status in the information storage unit 301 in association with the position information. Also, by the control unit 302 executing processing according to the control program, processing for determining a priority channel is realized. Note that the control unit 302 is typically a processor.

[0170] The NW interface unit 305 transmits and receives information via the communication network 1 according to the processing by the control unit 302. In particular, transmission and reception of information with the radio base station 100 are performed via the NW interface unit 305.

[0171] Note that the aggregation server 300 can also be implemented by a computer and a program, and the program can be recorded on a recording medium or provided through a network.

[0172] Hereinafter, with reference to FIGS. 23 and 24, the processing related to the communication between the radio base station 100 and the aggregation server 300 will be described.

[0173] First, with reference to FIG. 23, the processing executed in the radio base station 100 will be described. Each process in the flowchart shown in FIG. 23 is executed for each processing cycle.

[0174] In step S510, the radio base station 100 determines whether it is a timing to transmit the usage status (first usage status or second usage status) of the surrounding frequency channels to the aggregation server 300. This is determined, for example, by the activation of a timer that notifies a predetermined period.

[0175] When it is a timing to transmit to the aggregation server 300 (step S510; Yes), the process proceeds to step S511. When it is not a timing to transmit to the aggregation server (step S510; No), without transmitting the usage status of the surrounding frequency channels to the aggregation server 300 in this processing, step S510 is executed again at the next processing execution.

[0176] In step S511, the radio base station 100 transmits the usage status of the surrounding frequency channels to the aggregation server 300.

[0177] After step S511, this processing ends, and step S511 is executed again at the next processing execution.

[0178] Next, with reference to FIG. 24, the processing executed in the aggregation server 300 will be described. Each process in the flowchart shown in FIG. 24 is executed for each processing cycle.

[0179] In step S520, the aggregation server 300 determines whether it has received the usage status of the frequency channel (the first usage status or the second usage status) from the radio base station 100, or whether it is an opportunity to update the priority channel. That the opportunity to update the priority channel is determined, for example, by the activation of a timer that notifies a predetermined period.

[0180] When it is determined that the usage status of the frequency channel has been received from the radio base station 100, or when it is determined that it is an opportunity to update the priority channel (step S520; Yes), the process proceeds to step S521. When any of the determinations is negative (step S520; No), the priority channel is not updated in this processing, and step S520 is executed again at the next processing execution.

[0181] In step S521, the aggregation server 300 updates the priority channel for each of the plurality of radio base stations 100 based on the aggregated usage status of the frequency channels. Then, it is determined whether there is a radio base station 100 whose priority channel has been changed by the update of the priority channel.

[0182] If there is a radio base station 100 whose priority channel has been changed (step S521; Yes), the process proceeds to step S522. If there is no radio base station 100 whose priority channel has been changed (step S521; No), the notification of the priority channel is not performed, and step S522 is executed again at the next processing execution.

[0183] In step S522, the aggregation server 300 notifies the target radio base station 100 (the radio base station 100 whose priority channel has been changed) of the changed priority channel.

[0184] After step S522, this processing ends, and step S520 is executed again at the next processing execution.

[0185] Hereinafter, with reference to FIG. 25, a communication channel selection method of the radio base station 100 realized by the radio communication system 10 according to the modification example will be described. Each process in the flowchart shown in FIG. 25 is executed for each processing cycle.

[0186] In step S530, the radio base station 100 determines whether there is a notification of the usage status (first usage status or second usage status) of the surrounding frequency channels from the spectrum analyzer 110 or the radio terminal 200.

[0187] If there is a notification of the usage status of the surrounding frequency channels (step S530; Yes), the process proceeds to step S531. If there is no notification of the usage status of the surrounding frequency channels (step S530; No), the process proceeds to step S532.

[0188] In step S531, the radio base station 100 updates the estimation of the usage time rate for each frequency channel by the other system 20.

[0189] After step S531, the process proceeds to step S532.

[0190] In step S532, the radio base station 100 determines whether there is a notification of a change in the priority channel from the aggregation server 300.

[0191] If there is a notification of a change in the priority channel (step S532; Yes), the process proceeds to step S533. If there is no notification of a change in the priority channel (step S532; No), the current communication channel is maintained in this processing, and step S530 is executed again at the next processing execution.

[0192] In step S533, the radio base station 100 changes the priority channel according to the priority channel notified from the aggregation server 300.

[0193] After step S533, the process proceeds to step S534.

[0194] In step S534, the radio base station 100 determines whether it is necessary to switch the communication channel. Here, the radio base station 100 may determine whether it is necessary to switch the communication channel based on the long-term usage status of the frequency channel by the other system 20. Alternatively, it may determine the communication channel switch according to the instruction of the aggregation server 300. In this case, the aggregation server 300 is configured to execute a process of instructing each of a plurality of radio base stations to switch the communication channel according to the usage status of the aggregated frequency channel.

[0195] When it is determined that the communication channel needs to be switched (step S534; Yes), the process proceeds to step S535. When it is determined that the communication channel does not need to be switched (step S534; No), the current communication channel is maintained in the current process, and step S530 is executed again when the next process is executed.

[0196] In step S535 (channel selection process), the radio base station 100 selects and switches the communication channel according to the usage status of the frequency channel acquired in step S530. Here, the radio base station 100 preferentially selects the priority channel as the communication channel.

[0197] After step S535, the current process ends, and step S530 is executed again when the next process is executed.

[0198] By adopting the modified mode in this way, the same effects as those of the fifth embodiment can be achieved. Further, by managing the usage status of the frequency channel during a predetermined period in the aggregation server 300 in association with the location information, the usage status of the frequency channel by the other system 20 over a wide range and for a long term can be grasped.

[0199] 6. Sixth Embodiment Hereinafter, the sixth embodiment will be described. However, in the following description, the contents overlapping with the above-described matters are omitted as appropriate.

[0200] 6-1. Overview FIG. 26 is a conceptual diagram for explaining the overview of the wireless communication system 10 according to the sixth embodiment. The sixth embodiment is characterized by the operation of the wireless terminal 200.

[0201] The wireless terminal 200 according to the sixth embodiment executes a process of determining and switching the connection destination of the wireless base station 100 based on the usage status of the frequency channels acquired from the spectrum analyzer 210. In the example shown in FIG. 26, two wireless base stations 100, #1 and #2, are shown as candidates for the connection destination of the wireless terminal 200. Here, the communication channel of the wireless base station 100 of #1 is CH1, and the communication channel of the wireless base station 100 of #2 is CH2. Also, the frequency channel interfered with by the other system 20 is CH1.

[0202] Now, assume that the wireless terminal 200 is connected to the wireless base station 100 of #1. The wireless terminal 200 grasps the frequency channels interfered with by the other system 20 from the usage status of the frequency channels acquired from the spectrum analyzer 210. Then, upon receiving that the frequency channel interfered with by the other system 20 is CH1, the wireless terminal 200 operates to switch the connection destination to the wireless base station 100 of #2. Thereby, it is possible to set the wireless base station 100 having a communication channel that does not overlap with the other system 20 as the connection destination.

[0203] FIG. 27 is a conceptual diagram showing the operations of the wireless terminal 200 and the spectrum analyzer 210 according to the sixth embodiment. FIG. 27 shows the same figure as FIG. 2. In FIG. 27, the wireless terminal 200 starts communication with the wireless base station 100 of #1 as the connection destination at time t1. Thereafter, at time t2, a deterioration in communication quality is detected, and at time t3, the wireless terminal 200 inquires of the spectrum analyzer 210 about the usage status of the surrounding frequency channels. Here, since the wireless terminal 200 does not perform a frequency scan, the wireless terminal 200 continues communication with the wireless base station 100 of #1.

[0204] On the one hand, the spectrum analyzer 210 receives an inquiry from the wireless terminal 200 and starts a frequency scan. Thereafter, the spectrum analyzer 210 ends the frequency scan at time t4 and notifies the wireless terminal 200 of the usage status of the surrounding frequency channels as a response to the inquiry.

[0205] The wireless terminal 200 obtains the usage status of the surrounding frequency channels from the spectrum analyzer 210 and determines the destination wireless base station 100 according to the usage status. In the example shown in FIG. 27, the #2 wireless base station 100 is determined as the connection destination. Then, at time t5, the wireless terminal 200 switches the connection destination to the #2 wireless base station 100 and communicates.

[0206] 6-2. Configuration The configurations of the wireless base station 100 and the spectrum analyzer 110 according to the sixth embodiment may be the same as the configurations shown in FIG. 5. Also, the configurations of the wireless terminal 200 and the spectrum analyzer 210 according to the sixth embodiment may be the same as the configurations shown in FIG. 12. However, the control program stored in the information storage unit 201 includes a program related to the process of switching the destination wireless base station 100 according to the usage status of the surrounding frequency channels. Then, the control unit 202 reads the control program and control information from the information storage unit 201 and executes the process according to the control program based on the control information, thereby realizing the process of switching the destination wireless base station 100 according to the usage status of the surrounding frequency channels. Note that the inquiry to the spectrum analyzer 210 and the acquisition of the usage status of the surrounding frequency channels are performed via the interface unit 204.

[0207] 6-3. Switching of the Destination Wireless Base Station Hereinafter, with reference to FIG. 28, a method for switching the destination wireless base station 100 of the wireless terminal 200 realized by the wireless communication system 10 according to the sixth embodiment will be described. The flowchart shown in FIG. 28 starts, for example, when the wireless terminal 200 is activated. Also, each process of the flowchart is executed at every predetermined processing cycle.

[0208] In step S600, the wireless terminal 200 determines whether a predetermined trigger such as deterioration of communication quality has occurred.

[0209] If a predetermined trigger such as deterioration of communication quality has occurred (step S600; Yes), the process proceeds to step S601. If a predetermined trigger such as deterioration of communication quality has not occurred (step S600; No), the wireless base station 100 of the connection destination is not switched in this process, and step S600 is executed again when the next process is executed.

[0210] In step S601, the wireless terminal 200 inquires of the spectrum analyzer 210 provided in the vicinity about the usage status of surrounding frequency channels. Then, the wireless terminal 200 receives a response to the inquiry and acquires the usage status of the surrounding frequency channels.

[0211] In step S602, the wireless terminal 200 determines whether it is necessary to switch the connection destination wireless base station 100 based on the usage status of the surrounding frequency channels acquired in step S601. For example, the wireless terminal 200 estimates the level of interference from other systems 20 from the reception level of the communication channel of the candidate wireless base station 100 (however, the reception level of the wireless signal transmitted and received by the wireless terminal 200 itself is canceled). Then, when there is a wireless base station 100 with a smaller interference level than the interference level with respect to the communication channel of the currently connected wireless base station 100, it is determined that it is necessary to switch the connection destination wireless base station 100.

[0212] When it is determined that it is necessary to switch the connection destination wireless base station 100 (step S602; Yes), the process proceeds to step S603. When it is determined that it is not necessary to switch the connection destination wireless base station 100 (step S602; No), the wireless base station 100 of the connection destination is not switched in this process, and step S600 is executed again when the next process is executed.

[0213] In step S603, the wireless terminal 200 switches the destination radio base station 100 according to the usage status of the surrounding frequency channels acquired in step S601.

[0214] After step S603, the current process ends, and step S600 is executed again when the next process is executed.

[0215] 6-4. Effect As described above, according to the sixth embodiment, the wireless terminal 200 inquires of the spectrum analyzer 210 provided in the vicinity about the usage status of the surrounding frequency channels at a predetermined timing. The spectrum analyzer 210 performs a frequency scan in response to the inquiry and notifies the wireless terminal 200 of the usage status of the surrounding frequency channels. Then, the wireless terminal 200 acquires the usage status of the surrounding frequency channels from the spectrum analyzer 210 and switches the destination radio base station 100 according to the acquired usage status. Thereby, it is possible to set the radio base station 100 having a communication channel that does not overlap with the other system 20 as the connection destination. In particular, when the wireless terminal 200 grasps the usage status of the surrounding frequency channels, it is not necessary to stop the communication with the radio base station 100. Consequently, the transmission and reception by communication do not stop in the wireless communication system 10.

Explanation of Signs

[0216] 1 Communication network 10 Wireless communication system 10 Wireless communication system 20 Other system 100 Radio base station 110 First spectrum analyzer 200 Wireless terminal 210 Second spectrum analyzer 300 Aggregation server

Claims

1. A radio base station that communicates with one or more wireless terminals, A first spectrum analyzer provided in the vicinity of the radio base station, comprising: The first spectrum analyzer is configured to execute a monitoring process of receiving a first request from the radio base station and monitoring a first usage status of surrounding frequency channels. The radio base station A process of transmitting the first request to the first spectrum analyzer at a predetermined timing, A process of acquiring the first usage status from the first spectrum analyzer, From the first usage status, a channel selection process of selecting a communication channel for communication according to the usage status obtained by canceling information on radio signals transmitted and received by the radio base station, is configured to execute A wireless communication system characterized by this.

2. The wireless communication system according to claim 1, The first usage status includes a reception level for each frequency channel or frequency for surrounding radio signals, The radio base station is further configured to execute a process of transmitting calibration information for designating a reference frequency band in which the reception level is set to zero for the reception level at a predetermined time to the first spectrum analyzer. The first spectrum analyzer is further configured to execute a process of setting the reception level of the reference frequency band observed at the predetermined time as a reference error upon receiving the calibration information. The monitoring process includes subtracting the reference error from the reception level observed in the reference frequency band. A wireless communication system characterized by this.

3. The wireless communication system according to claim 1 or claim 2, Further comprising one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals, Each of the one or more second spectrum analyzers is configured to execute a process of monitoring a second usage status of surrounding frequency channels, Each of the one or more wireless terminals, executes a process of acquiring the second usage status from the second spectrum analyzer provided in the vicinity, and a process of notifying the wireless base station of the second usage status, and is configured to execute the above, The channel selection process includes selecting the communication channel according to the second usage status A wireless communication system characterized by the above.

4. The wireless communication system according to claim 1 or claim 2, further comprising one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals, Each of the one or more second spectrum analyzers is configured to execute a process of monitoring a second usage status of surrounding frequency channels upon receiving a second request from the nearby wireless terminal, Each of the one or more wireless terminals, executes a process of transmitting the second request to the second spectrum analyzer provided in the vicinity upon receiving a third request from the wireless base station, a process of acquiring the second usage status from the second spectrum analyzer provided in the vicinity, and a process of notifying the wireless base station of the second usage status, and is configured to execute the above, The wireless base station is further configured to execute a process of transmitting the third request to the one or more wireless terminals at the predetermined opportunity, The channel selection process includes selecting the communication channel according to the second usage status A wireless communication system characterized by the above. ​

5. A wireless communication system according to any one of Claims 1 to 4, wherein the wireless base station performs a process of storing the first usage status during a predetermined period in a storage device, performs a process of determining a priority channel to be preferentially used based on the first usage status during a predetermined period, and is further configured to execute, wherein the channel selection process includes preferentially selecting the priority channel as the communication channel A wireless communication system characterized by the above.

6. A wireless communication system according to any one of Claims 1, 2, or 5, further comprising one or more second spectrum analyzers provided in the vicinity of each of the one or more wireless terminals, each of the one or more second spectrum analyzers being configured to execute a process of monitoring a second usage status of surrounding frequency channels, each of the one or more wireless terminals performs a process of acquiring the second usage status from the second spectrum analyzer provided in the vicinity, and performs a process of determining the wireless base station that performs communication according to the second usage status, and is configured to execute A wireless communication system characterized by the above.

7. A method for selecting a communication channel of a wireless base station that communicates with one or more wireless terminals, wherein a spectrum analyzer is provided in the vicinity of the wireless base station, the spectrum analyzer being configured to execute a process of monitoring the usage status of surrounding frequency channels in response to a request, wherein the communication channel selection method includes transmitting the request to the spectrum analyzer at a predetermined timing, Obtaining the usage status from the spectrum analyzer; Selecting a communication channel through which the radio base station communicates according to the usage status obtained by canceling information on radio signals transmitted and received by the radio base station from the usage status; including A communication channel selection method characterized by the above.

8. A radio base station that communicates with one or more radio terminals, A spectrum analyzer is provided in the vicinity of the radio base station, The spectrum analyzer is configured to execute a process of monitoring the usage status of surrounding frequency channels upon receiving a request from the radio base station, The radio base station A process of transmitting the request to the spectrum analyzer at a predetermined opportunity; A process of obtaining the usage status from the spectrum analyzer; A process of selecting a communication channel for communication according to the usage status obtained by canceling information on radio signals transmitted and received by the radio base station from the usage status; is configured to execute A radio base station characterized by the above.

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