WO2010087416A1

WO2010087416A1 - Radio base station and communication control method

Info

Publication number: WO2010087416A1
Application number: PCT/JP2010/051171
Authority: WO
Inventors: 琢中山
Original assignee: 京セラ株式会社
Priority date: 2009-01-28
Filing date: 2010-01-28
Publication date: 2010-08-05
Also published as: JP2010177913A

Abstract

A radio base station (1) receives from a radio terminal an SB-CQI that is the highest one of the CQIs of the SBs in each of a plurality of BPs. The radio base station (1) then sets the CQI of a missing SB, which is between the SBs corresponding to the SB-CQIs in the respective adjacent BPs, to be equal to or less than the lower SB-CQI for the BP to which the SB corresponding to the SB-CQI lower in level belongs or to be equal to or less than the higher SB-CQI for the BP to which the SB corresponding to the SB-CQI higher in level belongs.

Description

Radio base station and communication control method

The present invention relates to a radio base station that assigns a channel to the radio terminal based on CQI fed back from the radio terminal, and a communication control method in the radio base station.

In a wireless communication system using frequency division duplex (FDD: Frequency Division Duplex), a wireless base station performs scheduling for assigning a frequency (channel) with good communication quality to a wireless terminal. At this time, the radio base station assigns a downlink channel to the radio terminal based on a downlink CQI (Channel QualityIndicator) fed back from the radio terminal, and further determines a modulation scheme.

In LTE (Long Term Evolution), which is a 3.9G communication system, the frequency band of the system is divided into units called BP (Bandwidth Part), and BP is further divided into units called SB (Sub Band). The In this LTE, in the Periodic Feedback mode, in order to use the uplink channel efficiently by reducing the amount of feedback, the wireless terminal can only use the CQI of the SB for the SB having the highest CQI in one BP. SB-CQI) is fed back to the radio base station. Further, the wireless terminal feeds back an average CQI (WB-CQI) in the frequency band of the system.

However, in such a radio communication system, the radio base station can acquire only SB-CQIs for some SBs among SBs in one BP. For this reason, when the SB-CQI between wireless terminals competes in the scheduler assignment determination process, the wireless base station must assign a channel corresponding to an SB whose SB-CQI is unknown to a certain wireless terminal. Occurs.

In this case, when the SB-CQI for the downlink SB allocated to the wireless terminal is so low that communication is impossible, the downlink communication becomes difficult.

In addition, the wireless terminal actually has a CQI that can select a high modulation scheme. However, since such a CQI is unknown at the wireless base station, it is necessary to select the lowest-ranking modulation scheme. I don't get it. For this reason, the transmission capacity of the entire system is impaired.

Therefore, an object of the present invention is to provide a radio base station and a communication control method capable of appropriately estimating the communication quality level.

In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a downstream band is divided into a plurality of first frequency bands (BP), and each of the first frequency bands is divided into a plurality of second frequency bands (SB). A radio base station (radio base station 1) configured in a radio communication system, wherein the highest communication among the communication qualities of the plurality of second frequency bands in the first frequency band for each first frequency band The reception unit (CQI information reception unit 120) that receives the first quality level (SB-CQI) indicating the quality from the wireless terminals (wireless terminals 2A to 2C) and the first frequency band in each of the adjacent first frequency bands An interpolation unit (missing CQI interpolation unit 140) that interpolates a second quality level indicating communication quality in a frequency band (missing SB) between the second frequency bands corresponding to the quality level, and the interpolating unit is adjacent to the second quality level. The first frequency band Of the frequency bands between the second frequency bands corresponding to the first quality level in each of the first frequency bands to which the second frequency band corresponding to the first quality level of the lower level belongs The portion is set to the second quality level that is lower than the first quality level of the lower level, and the first frequency band to which the second frequency band corresponding to the first quality level of the higher level belongs About this part, it makes it a summary to set it as the said 2nd quality level below the said 1st quality level of the said higher level.

Such a radio base station receives, for each first frequency band, a first quality level indicating the highest communication quality from among a plurality of second frequency bands in the first frequency band from the radio terminal, and When interpolating the second quality level indicating the communication quality of the frequency band between the second frequency bands corresponding to the first quality level in each of the matching first frequency bands, in each of the adjacent first frequency bands Of the frequency bands between the second frequency bands corresponding to the first quality level, the lower one of the levels of the first frequency band to which the second frequency band corresponding to the lower first quality level belongs. For the portion of the first frequency band to which the second frequency band corresponding to the first quality level of the higher level belongs, the first quality of the higher level level The second quality level which is below.

The communication quality of the portion of the first frequency band to which the second frequency band corresponding to the first quality level of the lower level belongs cannot exceed the first quality level of the lower level. Similarly, the communication quality of the portion of the first frequency band to which the second frequency band corresponding to the higher first quality level belongs cannot exceed the higher first quality level.

Therefore, the second communication level for the portion of the first frequency band to which the second frequency band corresponding to the first quality level of the lower level belongs is set to be equal to or lower than the first quality level of the lower level, By setting the second communication level for the portion of the first frequency band to which the second frequency band corresponding to the higher first quality level belongs to be equal to or lower than the higher first quality level, the communication quality is appropriately set. Can be estimated.

A second feature of the present invention relates to the first feature, wherein the interpolating unit includes a frequency band between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands. Of the first frequency band to which the second frequency band corresponding to the first quality level of the higher level belongs, the second corresponding to the first quality level of the higher level. The gist of the second quality level is that the level becomes higher as the frequency band is closer.

A third feature of the present invention relates to the first feature or the second feature, wherein the reception unit receives a first quality level indicating an average communication quality in the downlink band, and the interpolation unit receives the downlink The second frequency band corresponding to the first quality level in the first frequency band including the band edge that is one of the start end and the end of the band does not include the band end; and When the first quality level corresponding to the first frequency band including the band edge is higher than the third quality level indicating the average communication quality in the downlink band, the band edge corresponds to the first quality level. The gist is that the fourth quality level indicating the communication quality of the frequency band between the second frequency band is a level between the first quality level and the third quality level.

A fourth feature of the present invention relates to any one of the first feature to the third feature, and is based on the first quality level and the second quality level, with respect to the radio base station. The gist of the present invention is to provide an allocation unit that allocates a frequency band in the downlink direction.

A fifth feature of the present invention relates to any one of the first feature to the fourth feature, wherein the interpolating unit is an elapsed time after receiving the first quality level from the radio base station. Accordingly, the gist is to reduce the first quality level.

According to a sixth aspect of the present invention, a radio configured in a radio communication system in which a downlink band is divided into a plurality of first frequency bands, and each of the first frequency bands is divided into a plurality of second frequency bands. A communication control method in a base station, wherein the radio base station has a third quality level indicating an average communication quality in the downlink band, and the plurality of second frequencies in the first frequency band for each of the first frequency bands. Receiving a first quality level indicating the highest communication quality among the communication qualities of the frequency band from the radio terminal; and the first quality level in each of the first frequency bands adjacent to the radio base station. Interpolating a second quality level indicating communication quality in a frequency band between the second frequency bands corresponding to the first frequency band, and the interpolating step in each of the adjacent first frequency bands. Among the frequency bands between the second frequency bands corresponding to the first quality level, the portion of the first frequency band to which the second frequency band corresponding to the lower first quality level belongs. Is a portion of the first frequency band to which the second frequency band corresponding to the first quality level of the higher level belongs to the second quality level which is lower than the first quality level of the lower level The gist is that the second quality level is lower than the first quality level of the higher level.

According to the present invention, it is possible to provide a radio base station and a communication control method capable of appropriately estimating the communication quality level.

FIG. 1 is an overall schematic configuration diagram of a radio communication system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a downlink frequency band according to the embodiment of the present invention. FIG. 3 is a schematic configuration diagram of a radio base station according to the embodiment of the present invention. FIG. 4 is a functional block configuration diagram of a control unit, a reception unit, and a transmission unit in the radio base station according to the embodiment of the present invention. FIG. 5 is a functional block diagram of the missing CQI interpolation unit according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of SB-CQI received by the radio base station according to the embodiment of the present invention. FIG. 7 is a diagram illustrating an example of interpolation by the missing CQI interpolation unit according to the embodiment of the present invention. FIG. 8 is a schematic configuration diagram of a radio terminal according to the embodiment of the present invention. FIG. 9 is a functional block configuration diagram of the wireless terminal according to the embodiment of the present invention. FIG. 10 is a flowchart showing an operation of the radio base station according to the embodiment of the present invention.

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

(1) Configuration of Radio Communication System First, regarding the configuration of the radio communication system according to the embodiment of the present invention, (1.1) overall schematic configuration of radio communication system, (1.2) configuration of radio base station, (1 .3) The configuration of the wireless terminals will be described in the order.

(1.1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 10 according to an embodiment of the present invention.

As shown in FIG. 1, the radio communication system 10 is an LTE (Long Term Evolution) radio communication system which is a 3.9G communication system. The radio communication system 10 includes a radio base station 1, a radio terminal 2A, a radio terminal 2B, and a radio terminal 2C. In FIG. 1, radio terminals 2A to 2C are located in a cell 3 provided by the radio base station 1.

As shown in FIG. 2, the downlink frequency band (downlink band) in the wireless communication system 10 is divided into units called BP (Bandwidth-Part). BP is divided into units called SB (Sub Band), and SB is further divided into RB (Resouce Block).

(1.2) Configuration of Radio Base Station Next, regarding the configuration of the radio base station 1, (1.2.1) schematic configuration of the radio base station, (1.2.2) detailed configuration of the radio base station. explain.

(1.2.1) Schematic Configuration of Radio Base Station FIG. 3 is a schematic configuration diagram of the radio base station 1. As illustrated in FIG. 3, the radio base station 1 includes a control unit 102, a storage unit 103, a wired communication unit 104, a reception unit 105, a transmission unit 106, and an antenna 107.

The control unit 102 is constituted by a CPU, for example, and controls various functions provided in the radio base station 1. The storage unit 103 is configured by a memory, for example, and stores various types of information used for control and the like in the radio base station 1. The wired communication unit 104 is connected to an access gateway or the like existing in the upper network via a router or the like (not shown).

The receiving unit 105 receives wireless signals from the wireless terminals 2A to 2C via the antenna 107. The transmitting unit 106 transmits a radio signal to the radio terminals 2A to 2C via the antenna 107.

(1.2.2) Detailed Configuration of Radio Base Station Next, a detailed configuration of the radio base station 1, specifically, functional block configurations of the control unit 102, the reception unit 105, and the transmission unit 106 will be described. FIG. 4 is a functional block configuration diagram of the control unit 102, the reception unit 105, and the transmission unit 106. In FIG. 4, the control unit 102 includes a missing SB recognition unit 130, a missing CQI interpolation unit 140, and a scheduler 150. The receiving unit 105 includes a CQI information receiving unit 120, and the transmitting unit 106 includes a transmission signal generating unit 160.

In the following description, it is assumed that the radio base station 1 communicates with the radio terminal 2A. However, the same applies when the radio base station 1 communicates with the radio terminal 2B and the radio terminal 2C.

The CQI information receiving unit 120 receives the CQI notification transmitted from the wireless terminal 2A. The CQI notification includes a CQI (hereinafter referred to as SB-CQI) for an SB having the highest CQI (Channel Quality Indicator) in each BP, and an SB ID (SB-ID) corresponding to the SB-CQI. The CQI information receiving unit 120 outputs the CQI notification to the missing SB recognition unit 130.

The missing SB recognition unit 130 determines whether there is an SB for which CQI is not notified, based on the SB ID included in the CQI notification input from the CQI information receiving unit 120. When there is an SB for which CQI is not notified, the SB is recognized as a missing SB. Specifically, the missing SB recognition unit 130 recognizes SBs having SB-IDs between SB-IDs corresponding to SB-CQIs in adjacent BPs included in the CQI notification as missing SBs.

If there is a missing SB, the missing SB recognition unit 130 outputs a CQI notification to the missing CQI interpolation unit 140.

The missing CQI interpolation unit 140 uses the SB-CQI included in the CQI notification input from the missing CQI interpolation unit 140 to interpolate the CQI of the missing SB.

FIG. 5 is a functional block diagram of the missing CQI interpolation unit 140. The missing CQI interpolation unit 140 includes a CQI comparison unit 142 and a CQI interpolation unit 144.

The CQI comparison unit 142 inputs the SB-CQI for each BP from the missing SB recognition unit 130. Next, CQI comparison section 142 compares SB-CQIs in each of adjacent BPs. Further, CQI comparison section 142 outputs the result of comparing SB-CQI in each of adjacent BPs to CQI interpolation section 144.

The CQI interpolation unit 144 uses the comparison result input from the CQI comparison unit 142 and the SB-CQI in each of the adjacent BPs to be compared, and the frequency band between SBs corresponding to these SB-CQIs (hereinafter referred to as SB-CQI). , CQI of missing SB existing in the interpolation frequency band) is interpolated.

Specifically, the CQI interpolation unit 144 sets the CQI of the missing SB existing in the interpolation frequency band in the BP to which the SB corresponding to the SB-CQI having the lower level belongs to be equal to or lower than the SB-CQI having the lower level. To do. Further, the CQI interpolation unit 144 sets the CQI of the missing SB present in the interpolation frequency band in the BP to which the SB corresponding to the SB-CQI having the higher level is equal to or lower than the SB-CQI having the higher level, and The higher the level is, the closer to the SB corresponding to the SB-CQI of the higher level.

Then, the CQI interpolation unit 144 outputs the CQI notification and the CQI of the missing SB to the scheduler 150.

FIG. 6 is a diagram illustrating an example of the SB-CQI received by the wireless base station 1 from the wireless terminal 2A. FIG. 7 is a diagram illustrating an example of the CQI interpolation of the missing SB by the missing CQI interpolation unit 140 in the case of FIG.

6, the downstream frequency band in the wireless communication system 10 is divided into BP1, BP2, and BP3. Further, BP1 is divided into SB11, SB12 and SB13, BP2 is divided into SB21, SB22 and SB23, and BP3 is divided into SB31, SB32 and SB33.

The radio base station 1 receives the CQI of SB12 in BP1, the CQI of SB21 in BP2, and the CQI of SB33 in BP3 as SB-CQI corresponding to each BP. At this time, the missing SB recognition unit 130 recognizes SB13, SB22, SB23, SB31, and SB32 corresponding to the CQI not received as missing SB.

In FIG. 6, BP1 and BP2 are adjacent to each other. Furthermore, the CQI of SB-12 that is SB-CQI is higher than the CQI of SB-21 that is SB-CQI. Therefore, the CQI comparison unit 142 outputs a comparison result indicating that the SB-12 CQI is higher for the adjacent BP1 and BP2 to the CQI interpolation unit 144.

In this case, as shown in FIG. 7, the CQI interpolation unit 144 linearly interpolates between SB12 and SB21 based on the comparison result, thereby eliminating SB13 that is a missing SB present in the interpolation frequency band belonging to BP1. Regarding the CQI, the CQI is made higher as it is lower than the SB-12 corresponding to the SB-CQI corresponding to the BP1 and closer to the SB12 corresponding to the higher SB-CQI (FIG. 7). Interpolation SB-CQI1).

In FIG. 6, BP2 and BP3 are adjacent to each other. Furthermore, the CQI of SB-21 that is SB-CQI corresponding to BP2 is higher than the CQI of SB-33 that is SB-CQI corresponding to BP3. Therefore, the CQI comparison unit 142 outputs a comparison result indicating that the SB-CQI corresponding to BP3 is higher for the adjacent BP2 and BP3 to the CQI interpolation unit 144.

In this case, as shown in FIG. 7, based on the comparison result, the CQI interpolation unit 144 converts the CQIs of SB13 and SB14, which are missing SBs in the interpolation frequency band belonging to BP2, to the SB-CQI corresponding to BP2. It is the same as the CQI of a certain SB-21 (interpolation SB-CQI2 in FIG. 7). Further, the CQI interpolation unit 144 performs linear interpolation between SB23 and SB33 based on the comparison result, so that the CQI of SB31 and SB32 that are missing SBs in the interpolation frequency band belonging to BP3 corresponds to BP3. The SB-CQI of SB-33 that is equal to or less than the SB-CQI to be performed (SBI-CQI3 in FIG. 7).

Then, the CQI interpolation unit 144 outputs the CQI notification and the interpolated CQIs of SB13, SB22, SB23, SB31, and SB32 to the scheduler 150.

Returning to FIG. 4 again, functional block configurations of the control unit 102, the reception unit 105, and the transmission unit 106 will be described.

The scheduler 150 allocates a channel to the wireless terminal 2A using the CQI notification input from the CQI interpolation unit 144 and the CQI of the determined missing SB.

The transmission signal generation unit 160 generates a transmission signal for notifying the channel information assigned by the scheduler 150 to the wireless terminal 2A. The transmission signal generation unit 160 transmits the generated transmission signal to the wireless terminal 2A.

(1.3) Configuration of Wireless Terminal Next, the configuration of the wireless terminal 2A will be described in the order of (1.3.1) Schematic configuration of the wireless terminal and (1.3.2) Detailed configuration of the wireless terminal.

(1.3.1) Schematic Configuration of Radio Terminal FIG. 8 is a schematic configuration diagram of the radio terminal 2A. The radio base station 2B and the radio base station 2C have the same configuration. As illustrated in FIG. 8, the wireless terminal 2A is, for example, a voice terminal, and includes an RF unit 201, a control unit 203, a microphone 205, a speaker 207, and an antenna 209.

The RF unit 201 includes an RF circuit, a baseband circuit, and the like, performs modulation and demodulation, encoding and decoding, and transmits and receives a radio signal via the antenna 209.

The control unit 203 is configured by a CPU, for example, and controls various functions provided in the wireless terminal 2.

The microphone 205 collects sound and outputs sound data based on the collected sound to the control unit 203. The speaker 207 outputs sound based on the sound data acquired from the control unit 203.

(1.3.2) Detailed Configuration of Wireless Terminal Next, a detailed configuration of the wireless terminal 2A, specifically, a functional block configuration of the control unit 203 will be described. FIG. 9 is a functional block configuration diagram of the control unit 203. In FIG. 9, the control unit 203 includes a CQI calculation unit 230 and an SB-CQI selection unit 232.

The CQI calculation unit 230 calculates the CQI in each SB based on the radio signal received by the RF unit 201 via the antenna 209. In addition, CQI calculation section 230 calculates WB-CQI based on the received radio signal. The CQI calculation unit 230 outputs the CQI and WB-CQI of each SB to the SB-CQI selection unit 232.

The SB-CQI selection unit 232 inputs from the CQI calculation unit 230. Further, for each BP, the SB-CQI selection unit 232 selects the highest CQI among the SB CQIs in the BP as the SB-CQI. The SB-CQI selection unit 232 generates a CQI notification including the SB-CQI and the WB-CQI in each BP. The SB-CQI selection unit 232 outputs the generated CQI notification to the RF unit 201.

The RF unit 201 transmits a CQI notification to the radio base station 1.

(2) Operation of Radio Base Station FIG. 10 is a flowchart showing the operation of the radio base station 1 in the radio communication system 10.

In step S101, the CQI information receiving unit 120 of the radio base station 1 receives a CQI notification from the radio terminal 2A.

In step S102, the missing SB recognition unit 130 of the radio base station 1 determines whether there is an SB (missing SB) from which CQI is missing.

If there is a missing SB (YES in step S102), in step S103, the missing CQI interpolation unit 140 of the radio base station 1 interpolates a missing SB between SBs corresponding to SB-CQI in each of the adjacent BPs.

If there is no missing SB (NO in step S102), the process proceeds to step S104.

In step S104, the scheduler 150 of the radio base station 1 performs scheduling based on the CQI of all SBs of the radio terminal 2A. Specifically, a channel determined based on the CQI of all SBs is allocated to the wireless terminal 2A.

(3) Actions / Effects As described above, according to the present embodiment, the missing CQI interpolation unit 140 has the lower level of the interpolation frequency bands between SBs corresponding to SB-CQIs in each of adjacent BPs. The CQI of the missing SB existing in the interpolation frequency band in the BP to which the SB corresponding to the SB-CQI belongs is set to be equal to or lower than the SB-CQI having the lower level. Also, the CQI interpolation unit 144 sets the CQI of the missing SB existing in the interpolation frequency band in the BP to which the SB corresponding to the higher level SB-CQI belongs to be equal to or lower than the higher level SB-CQI.

The CQI of the interpolation frequency band in the BP to which the SB corresponding to the SB-CQI having the lower level belongs cannot exceed the SB-CQI having the lower level. Similarly, the CQI of the interpolation frequency band in the BP to which the SB corresponding to the higher level SB-CQI belongs cannot exceed the higher level SB-CQI.

Therefore, the radio base station 1 sets the CQI of the interpolation frequency band in the BP to which the SB corresponding to the SB-CQI having the lower level belongs to be equal to or lower than the SB-CQI having the lower level. Also, the radio base station 1 has the CQI of the interpolation frequency band in the BP to which the SB corresponding to the higher level SB-CQI belongs is equal to or lower than the higher level SB-CQI and has a higher level. The closer to SB12 corresponding to the other SB-CQI, the higher the CQI. Thereby, communication quality can be estimated appropriately.

Further, according to the present embodiment, the radio base station 1 allocates a channel to a radio terminal using the interpolated missing SB CQI and the CQI notification. For this reason, the radio base station 1 can appropriately perform scheduling even when the missing SB exists and the missing SB must be assigned to the wireless terminal.

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

For example, the CQI notification may further include the average (hereinafter referred to as WB-CQI) of the downlink CQI in the wireless communication system 10. In this case, when the SB corresponding to the SB-CQI in the BP including the band edge that is the start edge of the downlink band does not include the band edge, and when the SB-CQI is higher than the WB-CQI, The CQI of the frequency band (interpolation frequency band) between the band edge and the SB corresponding to the SB-CQI cannot be higher than the SB-CQI. Therefore, the CQI interpolation unit 144 sets the CQI of the interpolation frequency band to a level between SB-CQI and WB-CQI.

Further, the CQI interpolation unit 144 may measure an elapsed time after the CQI notification is received. Further, the CQI interpolation unit 144 may decrease the SB-CQI included in the CQI notification as the elapsed time is longer.

As the elapsed time from the reception of the CQI notification becomes longer, the SB-CQI included in the CQI notification is more likely to deviate from the current SB-CQI. Specifically, the current SB-CQI is likely to be lower than the SB-CQI included in the CQI notification as the elapsed time from the reception of the CQI notification becomes longer.

For this reason, the CQI interpolation unit 144 reduces the SB-CQI included in the CQI notification as the elapsed time from the reception of the CQI becomes longer, so that an appropriate difference considering the current SB-CQI is taken into account. SB-CQI can be set.

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

Note that the entire content of Japanese Patent Application No. 2009-017010 (filed on Jan. 28, 2009) is incorporated herein by reference.

As described above, the radio base station and the communication control method according to the present invention can appropriately estimate the level of communication quality, and are useful as the radio base station and the communication control method.

Claims

A wireless base station configured in a wireless communication system in which a downlink band is divided into a plurality of first frequency bands, and each of the first frequency bands is divided into a plurality of second frequency bands,
A receiving unit that receives, from a wireless terminal, a first quality level indicating the highest communication quality among the communication qualities of the plurality of second frequency bands in the first frequency band for each first frequency band;
An interpolation unit that interpolates a second quality level indicating communication quality in a frequency band between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands, and
The interpolation unit corresponds to the first quality level of the lower level among the frequency bands between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands. The portion of the first frequency band to which the second frequency band belongs is set to the second quality level that is lower than the first quality level of the lower level, and corresponds to the first quality level of the higher level. The radio base station having the second quality level that is equal to or lower than the first quality level of the higher level for the portion of the first frequency band to which the second frequency band belongs.
The interpolation unit corresponds to the higher first quality level among the frequency bands between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands. The portion of the first frequency band to which the second frequency band belongs is set to the second quality level in which the level becomes higher as the frequency band is closer to the second frequency band corresponding to the higher first quality level. The radio base station according to claim 1.
The receiving unit receives a third quality level indicating an average communication quality in the downlink band;
The interpolator does not include the band edge in the second frequency band corresponding to the first quality level in the first frequency band including a band edge that is one of a start edge and a terminal edge of the downlink band. And when the first quality level corresponding to the first frequency band including the band edge is higher than a third quality level indicating an average communication quality in the downlink band, the band edge, The fourth quality level indicating communication quality in a frequency band between the second frequency band corresponding to the first quality level is a level between the first quality level and the third quality level. Or the radio base station of 2.
The radio base station according to claim 1 or 2, further comprising an assigning unit that assigns a downlink frequency band to the radio base station based on the first quality level and the second quality level.
The radio base station according to claim 1 or 2, wherein the interpolation unit lowers the first quality level according to an elapsed time after receiving the first quality level from the radio base station.
A communication control method in a radio base station configured in a radio communication system in which a downlink band is divided into a plurality of first frequency bands, and each of the first frequency bands is divided into a plurality of second frequency bands. ,
The radio base station receives, from a radio terminal, a first quality level indicating the highest communication quality among the communication qualities of the plurality of second frequency bands in the first frequency band for each first frequency band. Steps,
The radio base station interpolating a second quality level indicating a communication quality of a frequency band between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands; Prepared,
The step of interpolating corresponds to the first quality level having a lower level among frequency bands between the second frequency bands corresponding to the first quality level in each of the adjacent first frequency bands. The portion of the first frequency band to which the second frequency band belongs is the second quality level that is lower than the first quality level of the lower level, and corresponds to the first quality level of the higher level. In the communication control method, the portion of the first frequency band to which the second frequency band belongs is set to the second quality level which is lower than the first quality level of the higher level.