JP2013098586A - Relay device and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay device and a communication control method, capable of determining the use frequency band of a service node hard to receive interference in the communication environment of the service node, while maintaining a good communication environment of a donor node.SOLUTION: A relay device 101 includes: a base station side communication unit 123 for exchanging radio signals with a base station using a base station side frequency band; a mobile station side communication unit 117 for exchanging radio signals with a mobile station using one of a plurality of available frequency bands different from the base station side frequency band; a storage unit 119 for storing each communication quality value on receipt of the communication quality value of the mobile station when a radio signal is transmitted using each available frequency band; and when the communication quality value of a certain tentative frequency band among the available frequency bands is a communication quality threshold or greater, a control unit 121 for controlling the mobile station side communication unit 123 to exchange radio signals at the tentative frequency band.

Description

  The present invention relates to a relay device and a communication control method.

  In order for a mobile station to communicate with a base station, the mobile station needs to be located in a range (service area) where radio waves from the base station can reach. However, in urban areas where mountainous areas and high-rise buildings are lined up, there are areas where radio waves are difficult to reach due to many obstacles. In addition, there are many areas (for example, the inside of a building and the basement) where radio waves do not reach from base stations installed outdoors. In particular, in a high-speed wireless communication method such as WiMAX (Worldwide Interoperability for Microwave Access) (registered trademark) standardized based on the IEEE standard 802.16e, radio waves in a high frequency band of 2.5 GHz or more are used. Such radio waves are highly straight and have a weak property of going around obstacles. For this reason, WiMAX and the like are strongly affected by obstacles. In order to cover such a region where radio waves do not reach, a relay device (repeater) that relays radio signals between the base station and the mobile station is required.

  This relay device has the advantage that the service area can be expanded, but has the disadvantage that radio waves emitted by the relay device cause interference with other radio waves. One of the interferences caused by relay devices is between a donor node (MS (Mobile Station) unit) that communicates with a base station and a service node (BS (Base Station) unit) that communicates with a mobile station. Mutual interference (wraparound interference or self-interference) can be mentioned. For example, when the reception period of the donor node and the transmission period of the service node overlap, the transmission wave from the base station interferes with the transmission wave of the service node, and the donor node transmits the transmission wave from the base station with degraded quality. Will be received. Similarly, mutual interference also occurs when the transmission period of the donor node and the reception period of the service node overlap.

  Therefore, conventionally, a relay device that suppresses mutual interference has been proposed (see, for example, Patent Document 1). The relay apparatus includes a donor node that transmits and receives a first signal in the first frequency band with the base station, and a service node that transmits and receives the second signal in the second frequency band with the mobile station. Then, when the donor node receives the second signal from the service node, the donor node measures the signal level of the second signal in the first frequency band. And the 2nd frequency band of a donor node is changed so that the said signal level may fall. That is, the frequency band (used frequency band) used in the service node is changed so that the influence of mutual interference on the donor node side is reduced.

JP 2010-232921 A

  However, in the conventional relay apparatus, since the use frequency band in the service node is determined based on the communication environment of the donor node, there is no guarantee that the use frequency band is appropriate for the communication environment of the service node. For example, radio waves from other base stations that use the same frequency band as the determined use frequency band may reach the service node. In this case, radio waves from the service node interfere with radio waves from other base stations. Then, communication between the service node and the mobile station becomes difficult. The farther the donor node and the service node are located, the more easily the communication environment of the donor node and the communication environment of the service node are different. Therefore, it is difficult to evaluate the communication environment of the service node in the communication environment of the donor node. Therefore, the farther the donor node and the service node are located, the higher the possibility that the used frequency band determined based on the communication environment of the donor node is subject to interference in the communication environment of the service node.

  Accordingly, an object of the present invention made in view of the above-described problems is to perform relaying that can determine a use frequency band of a service node that maintains a good communication environment of the donor node and is less susceptible to interference in the communication environment of the service node. An apparatus and a communication control method are provided.

In order to solve the above-described problems, the invention of the relay device according to the first aspect is as follows:
A relay device that relays radio signals transmitted and received between a base station and a mobile station,
A base station side communication unit that transmits and receives radio signals to and from the base station in a base station side frequency band;
A mobile station side communication unit that transmits and receives radio signals to and from the mobile station in any of a plurality of usable frequency bands different from the base station side frequency band;
When the mobile station side communication unit receives a communication quality value of the mobile station when a radio signal is transmitted in each of the usable frequency bands, a storage unit that stores the communication quality value;
A control unit that controls the mobile station side communication unit to transmit and receive a radio signal in the provisional frequency band when a communication quality value of a provisional frequency band of the usable frequency band is equal to or greater than a communication quality threshold; It is a relay device provided.

The invention according to the second aspect is the relay device according to the first aspect.
The control unit measures the electric field strength of the base station side communication unit in each of the usable frequency bands, and preferentially sets the usable frequency band having a smaller electric field strength as the provisional frequency band. It is.

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included.

For example, a communication control method according to a third aspect that realizes the present invention as a method is:
In a communication control method in a relay apparatus that relays radio signals transmitted and received between a base station and a mobile station, the relay apparatus includes:
Transmitting and receiving radio signals to and from the base station in a base station side frequency band;
Receiving a communication quality value of the mobile station when a radio signal is transmitted in each of a plurality of usable frequency bands different from the base station side frequency band, and storing the communication quality value;
A step of transmitting and receiving a radio signal to and from the mobile station in the provisional frequency band when a communication quality value of a provisional frequency band in the usable frequency band is equal to or higher than a communication quality threshold value.

  According to the relay apparatus and the communication control method according to the present invention configured as described above, the use frequency band of the service node is determined that keeps the communication environment of the donor node favorable and is less susceptible to interference in the communication environment of the service node. can do.

FIG. 1 is a schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. FIG. 2 is a functional block diagram illustrating a schematic configuration of the relay device according to the embodiment of the present invention. FIG. 3 is a flowchart showing processing of the relay device according to the embodiment of the present invention. FIG. 4 is a flowchart showing processing of the relay device according to the embodiment of the present invention.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. The radio communication system 11 includes a base station BS (Base Station), a mobile station MS (Mobile Station), and a relay device 101. When the communication method of the wireless communication system 11 is WiMAX, for example, a time division duplex (TDD) method is adopted for the wireless communication system 11. The relay apparatus 101 relays a radio signal transmitted and received between the base station BS and the mobile station MS in a wireless communication method such as WiMAX. The mobile station MS can transmit and receive radio signals to and from the base station BS via the relay device 101 even if the mobile station MS is located outside the cell (communication area) of the base station BS.

  FIG. 2 is a functional block diagram illustrating a schematic configuration of the relay device according to the embodiment of the present invention.

  The relay apparatus 101 includes a donor node (MS (Mobile Station) unit) 111 that communicates with a base station BS and a service node (BS (Base Station) unit) 113 that communicates with a mobile station MS. The relay device 101 is an integral type, a separation type, or a vehicle type. The integrated relay apparatus 101 includes a donor node 111 and a service node 113 in one housing. In the separation-type or vehicle-type relay device 101, the donor node 111 and the service node 113 can be arranged independently of each other. The separate or vehicle-type donor node 111 and the service node 113 are connected by a signal cable such as a LAN (Local Area Network) cable.

  First, functional blocks of the donor node 111 will be described. The donor node 111 includes a base station side communication unit 117, a storage unit 119, and a control unit 121. The base station side communication unit 117 and the storage unit 119 are connected to the control unit 121.

  The base station side communication unit 117 transmits and receives radio signals to and from the base station BS in the base station side frequency band via an antenna. The base station side communication unit 117 generates a baseband signal by performing amplification and down-conversion with low noise on the received radio signal, and sends the baseband signal to the control unit 121. The base station side communication unit 117 generates a radio signal by performing up-conversion and amplification on the baseband signal, and transmits the radio signal to the base station BS via the antenna.

  When the time division duplex method is adopted in the radio communication system 11, the base station side communication unit 117 receives a radio signal from the base station BS in the downlink subframe period (first period) of the base station BS, for example. Then, the radio signal is transmitted to the base station BS in the uplink subframe period (second period) of the base station BS following the first period. And the base station side communication part 117 repeats reception and transmission by repetition of the continuous 1st period and 2nd period.

  The storage unit 119 stores various information such as a communication quality value and a communication quality threshold value of the mobile station MS, and also functions as a work memory.

  The communication quality value of the mobile station MS is the reception quality value of the radio signal from the service node 113 in the mobile station MS, for example, CINR (Carrier to Interference and Noise Ratio) or SINR (Signal to Signal). Interference and Noise Ratio). When a radio signal from the service node 113 to the mobile station MS interferes with other radio waves (for example, radio waves from a base station other than the base station BS), the communication quality value becomes small. Hereinafter, in this embodiment, it is assumed that the communication quality value is CINR.

  The communication quality threshold is a standard for determining whether or not the mobile station MS can communicate with the service node 113 with stable quality, and is, for example, a value related to CINR or SINR. The stable quality is, for example, a quality that can correctly demodulate a radio signal from the service node 113 or a quality that can realize a desired throughput rate. When the communication quality value of the mobile station MS is equal to or higher than the communication quality threshold value, it means that the mobile station MS can receive a radio signal from the service node 113 with stable quality. Further, if the communication quality value of the mobile station MS is less than the communication quality threshold value, it means that the mobile station MS cannot receive a radio signal from the service node 113 with stable quality. Hereinafter, in this embodiment, it is assumed that the communication quality threshold is a value related to CINR.

  In the present embodiment, only the donor node 111 has the storage unit 119, but the present invention is not limited to this configuration. For example, only the service node 113 may have a storage unit, and the storage unit may store various information of the donor node 111 and the service node 113. Moreover, both the donor node 111 and the service node 113 have a storage unit, and each storage unit can store information on each unit associated with the storage unit.

  The control unit 121 controls and manages the entire donor node 111 and service node 113 as well as the functional blocks of the donor node 111 and service node 113. Here, the control unit 121 is configured as software executed on any suitable processor such as a CPU (Central Processing Unit), or a dedicated processor specialized for each process (for example, DSP (Digital Signal Processor)). Can also be configured. In the present embodiment, only the donor node 111 has the control unit 121, but the present invention is not limited to this configuration. For example, only the service node 113 has a control unit, and the control unit can control and manage the donor node 111 and the service node 113 as a whole. Further, both the donor node 111 and the service node 113 have a control unit, and each control unit can control and manage each unit related to the control unit. The processing performed by the control unit 121 will be described in detail with reference to FIGS. 3 and 4 to be described later.

  Next, functional blocks of the service node 113 will be described. The service node 113 includes a mobile station side communication unit 123. The mobile station side communication unit 123 is connected to the control unit 121.

  The mobile station side communication unit 123 transmits and receives radio signals to and from the mobile station MS via the antenna. The mobile station side communication unit 123 generates a baseband signal by performing amplification and down-conversion with low noise on the received radio signal, and sends the baseband signal to the control unit 121. Also, the mobile station side communication unit 123 generates a radio signal by performing up-conversion and amplification on the baseband signal, and transmits the radio signal to the mobile station MS via the antenna.

  The mobile station side communication unit 123 uses a frequency band different from the base station side frequency band when transmitting and receiving radio signals. There are a plurality of frequency bands (usable frequency bands) that can be used by the mobile station side communication unit 123. The mobile station side communication unit 123 transmits / receives a radio signal to / from the mobile station MS using any one of the usable frequency bands (used frequency band). For example, when the WiMAX system is adopted in the communication system 11, there are three frequency bands corresponding to the relay apparatus 101. Since any one of the three frequencies is used as a base station side frequency band by the base station side communication unit 117, the usable frequency band of the mobile station side communication unit 123 is two. Note that the frequency band corresponding to the relay apparatus 101 is a frequency band that can be used by the base station side communication unit 117 and the mobile station side communication unit 123 to transmit and receive radio signals.

  When the time division duplex method is employed in the wireless communication system 11, the mobile station side communication unit 123 receives, for example, a wireless signal from the mobile station MS within the first period, and transmits the wireless signal to the mobile station MS. Transmit within a second period following the first period. And the mobile station side communication part 123 repeats reception and transmission by repetition of the continuous 1st period and 2nd period. Mutual interference in the relay apparatus 101 is suppressed by the transmission period between the mobile station side communication unit 123 and the base station side communication unit 117 and the reception period between the mobile station side communication unit 123 and the base station side communication unit 117 being aligned. The

  Next, a method for determining the frequency band used by the relay apparatus 101 for communication with the mobile station MS will be described with reference to FIG. 3 and FIG. 3 and 4 are flowcharts showing processing of the relay device according to the embodiment of the present invention.

  When the relay apparatus 101 is activated for the first time, the relay apparatus 101 does not have the CINR information of the mobile station MS regarding the usable frequency band, and thus needs to acquire the information. Therefore, the relay apparatus 101 performs the process shown in FIG.

  First, based on the communication environment between the base station BS and the donor node 111, the base station side frequency band used by the base station side communication unit 117 is determined. For example, the base station BS performs carrier sense (observation of radio wave conditions around the base station BS), and assigns the frequency band with the lowest electric field strength to the relay apparatus 101. Thus, the control unit 121 sets the assigned frequency band as the base station side frequency band, and controls the base station side communication unit 117 to transmit and receive the synchronization signal in the base station side frequency band. Thereby, the communication connection between the base station BS and the donor node 111 is established.

  After establishing a communication connection between the base station BS and the donor node 111, the control unit 121 attempts to establish a communication connection between the mobile station MS and the service node 113. First, the control unit 121 acquires a base station side frequency band used by the base station side communication unit 117 for communication with the base station BS (step S101). Then, the control unit 117 sets a plurality of frequency bands excluding the base station side frequency band from the frequency band corresponding to the relay apparatus 101 as usable frequency bands (step S102).

  Subsequently, the control unit 121 performs, for example, carrier sense using the base station side communication unit 117, and measures the communication quality of the base station side communication unit 117 in each usable frequency band (step S103). The communication quality is, for example, RSSI (Received Signal Strength Indicator) representing electric field strength or CINR representing the influence of interference. In the present embodiment, the communication quality is assumed to be electric field strength. Thereby, the control part 121 can grasp | ascertain the electric field strength in the position of the donor node 111 of the electromagnetic wave which exists in a usable frequency band.

  Since the installation positions of the donor node 111 and the service node 113 may be close to each other, the frequency band where the electric field strength of the radio wave is small at the position of the donor node 111 is also the electric field strength of the radio wave in the frequency band at the position of the service node 113 Small possibility is high. Therefore, the control unit 121 identifies the frequency band having the lowest electric field strength among the usable frequency bands, and assigns the frequency band to the mobile station side communication unit 123 (step S104). Therefore, the mobile station side communication unit 123 transmits / receives a synchronization signal to / from the mobile station MS in the assigned frequency band, and establishes a communication connection with the mobile station MS.

  After establishing the communication connection with the service node 113, the mobile station MS calculates the CINR of the radio signal from the mobile station side communication unit 123. Then, the mobile station MS transmits a signal including the calculated CINR information to the service node 113. Then, the mobile station side communication unit 123 receives a signal including CINR information of the mobile station MS and sends it to the control unit 121. The control unit 121 acquires the CINR of the mobile station MS from the signal (step S105). Then, the control unit 121 stores the CINR in the storage unit 119 in association with the frequency band used by the mobile station side communication unit 123 (step S106).

  After starting relay between the base station BS and the mobile station MS, the relay apparatus 101 can change the frequency band used by the mobile station-side communication unit 123 as the communication environment changes. For example, with the change in the communication environment, in step S103, the frequency band with the lowest electric field strength among the usable frequency bands may change. In this case, the control unit 121 can assign the frequency band in which the electric field strength is the smallest to the mobile station side communication unit 123. Note that the control unit 121 can also assign the base station side frequency band to the mobile station side communication unit 123 in order to obtain the CINR of the mobile station MS.

  Assume that it is necessary to change the frequency band used by the mobile station side communication unit 123 after the relay apparatus 101 acquires the CINR of the mobile station MS regarding all usable frequency bands and base station side frequency bands. In this case, the relay apparatus 101 performs the following process of FIG. The case where the frequency band used by the mobile station side communication unit 123 needs to be changed is, for example, when the relay apparatus 101 is restarted or when the donor node 111 changes the connection destination by handover. is there.

  The relay apparatus 101 performs steps S111 to S113, which are the same processes as steps S101 to S103 in FIG. Then, the control unit 121 sets one of the usable frequency bands as a provisional frequency band (step S114). At this time, the control unit 121 can preferentially set the usable frequency band having a smaller electric field strength as the provisional frequency band. That is, the control unit 121 first sets the usable frequency band with the lowest electric field strength as the provisional frequency band.

  Then, the control unit 121 reads and compares the CINR of the mobile station MS and the communication quality threshold related to the provisional frequency band stored in the storage unit 119 (Step S115).

  When the CINR of the provisional frequency band is equal to or greater than the communication quality threshold (Yes in Step S115), the control unit 121 assigns the provisional frequency band to the mobile station side communication unit 123 as the use frequency band (Step S116). And the control part 121 controls the mobile station side communication part 123 so that a radio signal may be transmitted / received in a provisional frequency band. The mobile station side communication unit 123 uses the provisional frequency to transmit and receive a synchronization signal with the mobile station MS, thereby establishing a communication connection.

  After establishing the communication connection with the service node 113, the mobile station MS calculates the CINR of the radio signal from the mobile station side communication unit 123. Then, the mobile station MS transmits a signal including the calculated CINR information to the service node 113. Then, the mobile station side communication unit 123 receives a signal including CINR information of the mobile station MS and sends it to the control unit 121. The control unit 121 acquires the CINR of the mobile station MS from the signal, similarly to steps S105 and S106 in FIG. 3 (step S117). And the control part 121 updates the value of CINR relevant to the use frequency band of the mobile station side communication part 123 by making the memory | storage part 119 memorize | store the acquired CINR (step S118).

  In step S115, when the CINR of the provisional frequency band is less than the communication quality threshold (No in step S115), the control unit 121 determines whether or not there is a provisional frequency band candidate among the plurality of usable frequency bands. Judgment is made (step S119). The provisional frequency band candidate means a frequency band in which the CINR of the mobile station MS related to its own band and the communication quality threshold are not compared among the usable frequency bands.

  When there is a candidate for the provisional frequency band (Yes in step S119), the control unit 121 identifies a new provisional frequency band from the usable frequency band and changes the provisional frequency band (step S114). When the control unit 121 preferentially sets the usable frequency band having a smaller electric field strength as the provisional frequency band, the usable frequency band having the smallest electric field strength is changed to the new provisional frequency after the provisional frequency band before the change. It can be a band.

  Then, the control unit 121 compares the CINR of the mobile station MS related to the newly specified provisional frequency band and the communication quality threshold, and if the CINR of the provisional frequency band is equal to or greater than the communication quality threshold (Yes in step S115), The relay device 101 performs the processes of steps S116 to S118.

  When the CINR of the provisional frequency band is less than the communication quality threshold (No in step S115), the relay apparatus 101 performs the process of step S119 again.

  When there is no provisional frequency band candidate (No in step S119), the control unit 121 assigns the usable frequency band with the lowest electric field strength to the mobile station side communication unit 123 as the communication frequency band (step S120). Then, the mobile station side communication unit 123 establishes a communication connection by transmitting and receiving a synchronization signal to and from the mobile station MS using an available frequency band with the lowest electric field strength. Thereafter, the relay device 101 performs the processes of steps S117 and S118.

  As described above, in the present embodiment, when the CINR of a provisional frequency band in the usable frequency band is equal to or higher than the communication quality threshold, the control unit 121 of the relay apparatus 101 transmits and receives a radio signal in the provisional frequency band. The mobile station side communication unit 123 is controlled. The usable frequency band that may be used by the mobile station side communication unit 123 is different from the base station side frequency band that the base station side communication unit 117 uses for communication with the base station BS. Therefore, as long as the mobile station side communication unit 123 transmits a radio signal in one of the usable frequency bands, the signal from the mobile station side communication unit 123 interferes with the signal from the base station side communication unit 117, and the donor node 111 The communication environment will not be deteriorated. The mobile station side communication unit 123 is assigned a frequency band in which the CINR of the mobile station MS is equal to or higher than the communication quality threshold among the usable frequency bands. That is, the use frequency band of the mobile station side communication unit 123 is determined based on the CINR of the mobile station MS, that is, the communication environment of the service node 113. Therefore, the frequency band assigned by the control unit 121 to the mobile station side communication unit 123 is less susceptible to interference in the communication environment of the service node 113.

  In the present embodiment, the control unit 121 measures the electric field strength of the base station side communication unit 117 in each usable frequency band, and preferentially sets the usable frequency band having a smaller electric field strength as the provisional frequency band. be able to. As a result, the control unit 121 compares the CINR of the usable frequency band with the communication quality threshold in order from the usable frequency band having the lowest electric field strength. The measured electric field strength is the electric field strength at the position of the donor node 111 of the radio wave existing in the usable frequency band. The closer the communication donor node 111 and the service node 113 are, the closer the electric field strength of the service node 113 is. A value close to. Therefore, the CINR in the usable frequency band having a smaller electric field strength is more likely to be equal to or higher than the communication quality threshold. Therefore, the processing until the control unit 121 determines the frequency band to be allocated to the mobile station side communication unit 123 can be minimized.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

  For example, functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. Is possible.

  In the above-described embodiment of the present invention, the relay apparatus 101 has been described as acquiring the CINR of the mobile station MS related to the usable frequency band in advance, but the present invention is not limited to this aspect. For example, when the provisional frequency band is specified, the control unit can temporarily allocate the provisional frequency band to the mobile station side communication unit and perform communication with the mobile station. Then, the CINR of the radio signal transmitted from the mobile station in the provisional frequency band can be measured, and the value can be transmitted to the service node. The control unit compares the acquired CINR with the communication quality threshold, and can continue communication in the provisional frequency band between the mobile station side communication unit and the mobile station if the communication quality threshold is exceeded. In addition, when the acquired CINR is less than the communication quality threshold, the control unit can disconnect the communication connection between the mobile station side communication unit and the mobile station. That is, the relay apparatus can acquire the CINR related to the provisional frequency band immediately before comparing the CINR related to the provisional frequency band with the communication quality threshold.

  In the description of the embodiment of the present invention described above, for example, the meaning of the technical idea of the expression such as the threshold “more than” or the threshold “less than” is not necessarily a strict meaning, and depending on the specifications of the relay device, The meaning of including or not including the reference value is included. For example, the threshold “above” may imply not only the case where the value to be compared with the threshold reaches the threshold but also the case where the threshold is exceeded. Further, for example, “less than the threshold value” can imply not only when the value to be compared with the threshold value is below the threshold value but also when the threshold value is reached, that is, when the threshold value is below the threshold value.

DESCRIPTION OF SYMBOLS 11 Wireless communication system 101 Relay apparatus 111 Donor node 113 Service node 117 Base station side communication part 119 Storage part 121 Control part 123 Mobile station side communication part BS Base station MS Mobile station

Claims (3)

A relay device that relays radio signals transmitted and received between a base station and a mobile station,
A base station side communication unit that transmits and receives radio signals to and from the base station in a base station side frequency band;
A mobile station side communication unit that transmits and receives radio signals to and from the mobile station in any of a plurality of usable frequency bands different from the base station side frequency band;
When the mobile station side communication unit receives a communication quality value of the mobile station when a radio signal is transmitted in each of the usable frequency bands, a storage unit that stores the communication quality value;
A control unit that controls the mobile station side communication unit to transmit and receive a radio signal in the provisional frequency band when a communication quality value of a provisional frequency band of the usable frequency band is equal to or greater than a communication quality threshold; A relay device provided. The relay device according to claim 1,
The control unit measures the electric field strength of the base station side communication unit in each of the usable frequency bands, and preferentially sets the usable frequency band having a smaller electric field strength as the provisional frequency band. apparatus. In a communication control method in a relay apparatus that relays radio signals transmitted and received between a base station and a mobile station, the relay apparatus includes:
Transmitting and receiving radio signals to and from the base station in a base station side frequency band;
Receiving a communication quality value of the mobile station when a radio signal is transmitted in each of a plurality of usable frequency bands different from the base station side frequency band, and storing the communication quality value;
A communication control method including a step of transmitting and receiving a radio signal to and from the mobile station in the provisional frequency band when a communication quality value of a provisional frequency band in the usable frequency band is equal to or greater than a communication quality threshold value.

Images