JP5557270B2 - Radio base station, sounding control method in radio base station, and sounding control program in radio base station - Google Patents

Description

  The present invention relates to a radio base station, a sounding control method in a radio base station, and a sounding control program in a radio base station, and in particular, a radio base station and a radio base station that perform downlink beamforming based on sounding information from a radio terminal. And a sounding control program in a radio base station.

  In wireless communication such as PHS (Personal Handy-phone System) or WiMAX (Worldwide Interoperability for Microwave Access), the wireless base station performs smart antenna processing, thereby improving communication quality and communication throughput. Beamforming transmission, which is one of the smart antenna technologies, is achieved by a radio base station that obtains prior information from a terminal and concentrates and transmits radio waves in the direction in which the terminal is located based on the prior information. It is a technology that aims to improve.

  In WiMAX, in order to realize this, in the uplink period, the wireless terminal transmits sounding information as prior information to the wireless base station, and the wireless base station performs beamforming based on the received sounding information. (For example, see Non-Patent Document 1).

Takashi Shono, WiMAX textbook, July 21, 2008, Impress R & D Inc.

  However, in WiMAX, sounding information is arranged and transmitted in a data area for transmitting user data. As a result, the amount of user data that can be transmitted decreases, and the communication throughput of user data may decrease.

  Therefore, an object of the present invention is to provide a radio base station that can normally receive sounding information while suppressing a decrease in communication throughput of user data, a sounding control method in the radio base station, and a sounding control program in the radio base station. Is to provide.

  In order to solve the above-described problem, a radio base station according to the present invention provides a setting unit that sets a transmission frequency of sounding information based on a traffic amount and / or communication quality with a radio terminal, and a radio terminal A control unit for instructing to transmit sounding information at a set frequency, and a beam forming unit for imparting directivity to user data transmitted to the wireless terminal based on the sounding information received from the wireless terminal.

  Preferably, the setting unit sets the sounding information to be transmitted in every frame from all wireless terminals using the sounding information when the traffic amount of the uplink subframe is less than the first predetermined value.

  Preferably, the setting unit uses the sounding information when the traffic volume of the uplink subframe is equal to or greater than the first predetermined value and the traffic volume of the downlink subframe is less than the second predetermined value. It is set so that sounding information is transmitted from every wireless terminal every predetermined number of frames.

  Preferably, the setting unit wirelessly uses sounding information when an uplink subframe traffic volume is equal to or greater than a first predetermined value and a downlink subframe traffic volume is equal to or greater than a second predetermined value. When the signal-to-interference and noise ratio of user data from the terminal is less than the third predetermined value, the wireless terminal is set to transmit sounding information every frame.

  Preferably, the setting unit uses the sounding information when the traffic volume of the uplink subframe is equal to or greater than a first predetermined value and the traffic volume of the downlink subframe is equal to or greater than a second predetermined value. When the QoS of user data from the wireless terminal is greater than or equal to the fourth predetermined value, the sounding information is set to be transmitted from the wireless terminal every frame.

  Preferably, the setting unit wirelessly uses sounding information when an uplink subframe traffic volume is equal to or greater than a first predetermined value and a downlink subframe traffic volume is equal to or greater than a second predetermined value. The signal-to-interference noise ratio of user data from the terminal is greater than or equal to a third predetermined value and less than a fifth predetermined value, or the QoS of user data from the wireless terminal is less than a fourth predetermined value and a sixth predetermined value If the value is greater than or equal to the value, the wireless terminal is set to transmit sounding information every predetermined number of frames.

  Preferably, the setting unit wirelessly uses sounding information when an uplink subframe traffic volume is equal to or greater than a first predetermined value and a downlink subframe traffic volume is equal to or greater than a second predetermined value. When the signal-to-interference noise ratio of user data from the terminal is equal to or higher than the fifth predetermined value and the QoS of user data from the wireless terminal is less than the sixth predetermined value, no sounding information is transmitted from the wireless terminal. The control unit transmits the user data in the uplink subframe at the same frequency as the user data in the downlink subframe to the wireless terminal that is set so that no sounding information is transmitted. The beamforming unit will not send any sounding information. Using the reference signal included in the received user data, to have a directivity to the user data to be transmitted to the wireless terminal.

  In addition, the sounding control method in the radio base station of the present invention is configured to set the frequency of transmitting sounding information based on the traffic volume and / or communication quality with the radio terminal and the radio terminal. Instructing to transmit sounding information at a frequency, and providing directivity to user data transmitted to the wireless terminal based on the sounding information received from the wireless terminal.

  Also, the sounding control method program in the radio base station of the present invention is a step of setting the sounding information transmission frequency in a computer operating the radio base station based on the traffic volume and / or communication quality with the radio terminal. And instructing the wireless terminal to transmit sounding information at a set frequency, and imparting directivity to user data transmitted to the wireless terminal based on the sounding information received from the wireless terminal; Is executed.

  ADVANTAGE OF THE INVENTION According to this invention, sounding information can be received normally, suppressing the fall of the communication throughput of user data.

It is a block diagram showing the structure of the wireless base station of embodiment of this invention. It is a block diagram showing the structure of the radio | wireless terminal of embodiment of this invention. It is a figure showing the structure of the flame | frame transmitted in all the users normal sounding mode. It is a figure showing the structure of the flame | frame transmitted in all the user thinning sounding modes. It is a figure showing the structure of the flame | frame transmitted in the normal sounding mode classified by user and the thinning sounding mode classified by user. It is a figure showing the structure of the flame | frame transmitted in the sounding non-execution mode classified by user. It is a flowchart showing the operation | movement procedure of the radio base station of embodiment of this invention. It is a figure showing another structure of the flame | frame transmitted in the sounding non-execution mode classified by user.

Embodiments of the present invention will be described below with reference to the drawings.
(Configuration of radio base station)
FIG. 1 is a block diagram showing a configuration of a radio base station according to the embodiment of the present invention.

  Referring to FIG. 1, this radio base station 1 includes a first antenna 2, a second antenna 3, a first transmission control unit 4, a second transmission control unit 5, and a first reception. A control unit 6, a second reception control unit 7, a downlink beamforming unit 8, a modulation unit 10, an uplink beamforming unit 9, and a demodulation unit 11 are provided.

  The modulation unit 10 modulates a transmission signal using a modulation scheme such as QPSK (Quadrature Phase Shift Keying) or 16QAM (Quadrature Amplitude Modulation).

  The downlink beamforming unit 8 provides directivity to user data transmitted from the first and second antennas to the wireless terminal based on the sounding information received from the wireless terminal. More specifically, the downlink beamforming unit 8 uses the sounding information to calculate a transmission weight for adaptive array computation, and performs weighted addition using the user data output from the modulation unit and the transmission weight. Run.

The first antenna 2 is connected to the first transmission control unit 4 and the first reception control unit 6.
The second antenna 3 is connected to the first transmission control unit 5 and the first reception control unit 7.

  The first transmission control unit 4 includes a subcarrier arrangement unit 19, an IFFT (Inverse First Fourier Transform) unit 18, a DAC (Digital-Analog Conversion) 17, an amplifier 16, and an RF unit 15. The second transmission control unit 5 has the same configuration as the first transmission control unit 4. However, in the second transmission control unit 5, the output of the RF unit 20 is sent to the second antenna 3.

  The subcarrier arrangement unit 19 performs a subcarrier allocation process for allocating the uplink signal to each subcarrier to generate a multicarrier signal. The subcarrier arrangement unit 19 performs subchannel (subcarrier) allocation processing according to an adjacent subcarrier arrangement method (Adaptive Modulation and Coding: AMC).

  The IFFT unit 18 converts the frequency domain signal into the time domain by IFFT to generate a time domain multi-carrier signal.

  The DAC 17 performs digital-analog conversion on the multi-carrier signal in the time domain to generate a multi-carrier signal as an analog signal.

The amplifier 16 amplifies the multicarrier signal.
The RF unit 15 performs frequency conversion on the amplified baseband multicarrier signal, generates a radiofrequency multicarrier signal, and outputs the multicarrier signal to the first antenna 2.

  The first reception control unit 6 includes an RF unit 25, an amplifier 26, an ADC (Analog-Digital Conversion) 27, an FFT (Fast Fourier Transform) unit 28, and a subcarrier arrangement unit 29. The second reception control unit 7 has the same configuration as the first reception control unit 6. However, in the second reception control unit 7, the RF unit 30 receives a signal from the second antenna 3.

  The RF unit 25 performs frequency conversion on the radio frequency multicarrier signal received from the first antenna 2 to generate a baseband multicarrier signal.

The amplifier 26 amplifies the baseband multi-carrier signal.
The ADC 27 performs analog-digital conversion on the amplified multicarrier signal.

  The FFT unit 28 converts the time domain signal into the frequency domain by FFT to generate a frequency domain multicarrier signal.

The subcarrier arrangement unit 29 extracts the downlink signal assigned to each subcarrier.
The uplink beamforming unit 9 gives directivity to user data received from the first and second antennas 2 and 3 using a reference signal included in the received signal. Uplink beamforming section 9 calculates a receiving weight for adaptive array calculation using the reference signal, and performs weighted addition using the user data and receiving weight output from subcarrier arrangement sections 29 and 34 To do.

  The demodulator 11 demodulates a signal modulated using a modulation scheme such as QPSK (Quadrature Phase Shift Keying) or 16QAM (Quadrature Amplitude Modulation).

  Further, the radio base station 1 includes a control data management unit 13, a user data management unit 14, a sounding information extraction unit 36, and a mode setting unit 35.

  The mode setting unit 35 performs sounding for every wireless terminal (user) that uses sounding information from every wireless terminal that uses sounding information in every frame based on the traffic volume and / or communication quality with the wireless terminal. Sounding mode for all users where information is transmitted, Sounding mode for all users where sounding information is transmitted for every specified number of frames from all wireless terminals that use sounding information, and every frame from a specific wireless terminal that uses sounding information Normal sounding mode for each user for which sounding information is transmitted by the user, Thinning sound mode for each user for which sounding information is transmitted for each predetermined number of frames from a specific wireless terminal using sounding information, and sounding information Sounding information from a particular wireless terminal sets one of the user-specific sounding non-execution mode that is not sent to.

  The mode setting unit 35 includes an SINR (Signal to Interface and Noise and Ratio) calculation unit 37 and a QoS (Quality of Service) management unit 38.

  An SINR (Signal to Interface and Noise and Ratio) calculation unit 37 calculates a signal-to-interference and noise ratio (SINR) of user data of a downlink (DL) subframe as communication quality.

  The QoS (Quality of Service) management unit 38 holds QoS (Quality of Service) of user data of downlink (DL) subframes as communication quality. Here, QoS is set in the first to fifth stages, and the fifth stage requires the highest service quality.

  The control data management unit 13 creates control data and manages transmission and reception of control data. The control data management unit 13 outputs the control data to the modulation unit 10 and extracts the control data from the data output from the demodulation unit 11. The control data management unit 13 includes a sounding control unit 12 and a channel control unit 92.

  The sounding control unit 12 outputs information instructing the wireless terminal to transmit sounding information in the mode set by the mode setting unit 35 to the modulation unit.

  The channel control unit 92 transmits the user data in the uplink subframe to the radio terminal set in the user-specific sounding non-execution mode at the same frequency as the user data in the downlink subframe. Information to be instructed is output to the modulation unit 10.

  The user data management unit 14 manages user data and manages transmission and reception of user data. The user data management unit 14 outputs user data to the modulation unit 10 and extracts user data from the data output from the demodulation unit 11.

  The sounding information extraction unit 36 extracts sounding information from data transmitted from the wireless terminal and output from the demodulation unit 11.

Subcarrier arrangement units 19, 24, 29 and 34, downlink beamforming unit 8, uplink beamforming unit 9, modulation unit 10, demodulation unit 11, control data management unit 13, user data management unit 14, mode in radio base station 1 The functions of the setting unit 35 and the sounding information extraction unit 36 are realized by a computer.
(Configuration of wireless terminal)
FIG. 2 is a block diagram showing the configuration of the wireless terminal according to the embodiment of the present invention.

  Referring to FIG. 2, the wireless terminal 41 includes a first antenna 42, a second antenna 43, a first transmission control unit 44, a first reception control unit 45, and a second reception control. Unit 46, uplink beamforming unit 67, modulation unit 47, demodulation unit 48, user data management unit 83, control data management unit 82, and sounding information generation unit 81.

  A first antenna 42, a second antenna 43, a first transmission control unit 44, a first reception control unit 45, a second reception control unit 46, an uplink beamforming unit 67, a modulation unit 47, a demodulation unit 48, The user data management unit 83 is the same as that of FIG.

  The control data management unit 82 creates control data and manages transmission and reception of control data. The control data management unit 82 outputs the control data to the modulation unit 47 and extracts control data from the data output from the demodulation unit 48.

The sounding information generation unit 81 outputs sounding information transmitted from the first antenna 42.
(Frames transmitted in each mode)
Next, the structure of the frame transmitted in each mode will be described.

  FIG. 3 is a diagram illustrating a configuration of a frame transmitted in the all-user normal sounding mode.

  Referring to FIG. 3, user data of the first to sixth users is transmitted in this frame. Sounding information S1 to S6 of the first to sixth users using sounding information is transmitted in the uplink subframe.

  FIG. 4 is a diagram illustrating a configuration of a frame transmitted in the all-user thinning-out sounding mode.

  FIG. 4A shows a frame included in one period (N frame). Here, N is a natural number of 2 or more.

  Referring to FIG. 4A, user data of the first to sixth users is transmitted in this frame. Sounding information S1 to S6 of the first to sixth users using sounding information is transmitted in the uplink subframe.

FIG. 4B shows (N−1) frames included in one period (N frame).
Referring to FIG. 4B, user data of the first to sixth users is transmitted in this frame. No sounding information of any user is transmitted in the uplink subframe.

  FIG. 5 is a diagram illustrating a configuration of a frame transmitted in the normal sounding mode for each user and the thinning sounding mode for each user. FIG. 5 shows a case where the first, third, fifth, and sixth users are set to the user-specific normal sounding mode, and the second user and the fourth user are set to the user-specific thinning sounding mode. ing.

  FIG. 5A shows a frame included in one period (M frame). Here, M is a natural number of 2 or more.

  Referring to FIG. 5A, user data of the first to sixth users is transmitted in this frame. Sounding information S1 to S6 of the first to sixth users using sounding information is transmitted in the uplink subframe.

FIG. 5B shows (M−1) frames included in one period (M frame).
Referring to FIG. 5B, user data of the first to sixth users is transmitted in this frame. Of the first to sixth users using sounding information, the first, third, fifth, and sixth user sounding information S1, S3, S5, and S6 are transmitted in the uplink subframe, and the second, The sounding information S2 and S4 of the fourth user is not transmitted.

  FIG. 6 is a diagram illustrating a configuration of a frame transmitted in the user-specific sounding non-execution mode. FIG. 6 shows a case where the first to sixth users are set to the user-specific sounding non-execution mode.

  Referring to FIG. 6, user data of the first to sixth users is transmitted in this frame. No sounding information of any user is transmitted in the uplink subframe. The user data of the first to sixth users uses the same subchannel (frequency) in the uplink subframe and the downlink subframe.

(Operation)
FIG. 7 is a flowchart showing the operation procedure of the portable radio base station embodying the present invention. These processes are performed by a computer having a memory and a CPU (Central Processing Unit) executing a sounding control program.

  Referring to FIG. 7, mode setting unit 35 checks whether or not the uplink (UL) subframe usage rate is equal to or greater than Y1% for X frames consecutively (step S101).

  When the usage rate of the uplink (UL) subframe is not equal to or more than Y1% (first predetermined value) for X frames continuously (NO in step S101), the mode setting unit 35 uses all sounding information. Sets all users normal sounding mode for the user. The sounding control unit 12 transmits information instructing transmission of sounding information to each user's wireless terminals that use sounding information in each UL frame. The sounding information extraction unit 36 receives sounding information included in each UL frame transmitted from the wireless terminals of all users. The downlink beam forming unit 8 uses the latest received sounding information to provide directivity to the user data to the communication partner wireless terminal (step S102).

  The mode setting unit 35 determines that the usage rate of the UL subframe is Y1% or more for X frames continuously (YES in step S101), and the usage rate of the DL subframe is Y2% for X frames continuously ( If it is not equal to or greater than (second predetermined value) (NO in step S103), all users using sounding information are set to the all-user thinning sounding mode. The sounding control unit 12 transmits information instructing transmission of sounding information to the wireless terminals of all users who use sounding information at a rate of one UL N frame (N is a natural number of 2 or more). The sounding information extraction unit 36 receives the sounding information included in the UL N frame at a rate of one transmitted from the wireless terminals of all users. The downlink beam forming unit 8 uses the latest received sounding information to provide directivity to the user data to the communication partner wireless terminal (step S104).

Next, the mode setting unit 35 sets the user number K to 1 (step S105).
Next, the mode setting unit 35 checks whether the signal-to-interference noise ratio (SINR) of the user data of the Kth user in the DL subframe is equal to or greater than a third predetermined value (α1).

  When the signal-to-interference and noise ratio (SINR) of the user data of the Kth user in the DL subframe is less than the third predetermined value (α1) (NO in step S106), the mode setting unit 35 is the Kth user. The normal sounding mode for each user is set. The sounding control unit 12 transmits, to the wireless terminal of the Kth user, information instructing transmission of sounding information in each UL frame. The sounding information extraction unit 36 receives sounding information included in each UL frame transmitted from the wireless terminal of the Kth user. The downlink beamforming unit 8 uses the latest received sounding information to provide directivity to the user data to the wireless terminal of the Kth user (step S107).

  The mode setting unit 35 has a signal-to-interference and noise ratio (SINR) of user data of the Kth user in the DL subframe that is equal to or greater than a third predetermined value (α1) (YES in step S106), and the DL subframe. If the QoS (quality of service) of the user data of the Kth user is equal to or greater than the fourth predetermined value (β1) (NO in step S108), the user-specific normal sounding mode is set for the Kth user. Set. The sounding control unit 12 transmits, to the wireless terminal of the Kth user, information instructing transmission of sounding information in each UL frame. The sounding information extraction unit 36 receives sounding information included in each UL frame transmitted from the wireless terminal of the Kth user. The downlink beamforming unit 8 uses the latest received sounding information to provide directivity to the user data to the wireless terminal of the Kth user (step S109).

  The mode setting unit 35 has a signal-to-interference and noise ratio (SINR) of user data of the Kth user in the DL subframe that is equal to or greater than a fifth predetermined value (α2) (α2> α1), and the DL subframe If the QoS of the user data of the Kth user is less than the sixth predetermined value (β2) (β2 <β1) (YES in step S110), the user-specific sounding non-execution mode is set for the Kth user. The sounding control unit 12 transmits information instructing not to transmit any sounding information to the wireless terminal of the Kth user.

  Further, the channel control unit 92 transmits information instructing the wireless terminal of the Kth user to transmit the user data in the uplink frame at the same frequency as the user data in the downlink frame. The downlink beamforming unit 8 uses the reference signal included in the received user data of the Kth user to give directivity to the user data to the wireless terminal of the Kth user (step S111).

  The mode setting unit 35 has a signal-to-interference and noise ratio (SINR) of user data of the Kth user in the DL subframe that is less than a fifth predetermined value (α2) or the user data of the Kth user in the DL subframe. If QoS is equal to or greater than the sixth predetermined value (β2) (NO in step S110), the user-specific thinning sounding mode is set for the Kth user. The sounding control unit 12 transmits information instructing transmission of sounding information to the wireless terminal of the Kth user at a rate of one UL N frame (N is a natural number of 2 or more). The sounding control unit 12 receives the sounding information included in the UL N frame at a rate of one transmitted from the wireless terminal of the Kth user. The downlink beam forming unit 8 uses the latest received sounding information to provide directivity to the user data to the wireless terminal of the Kth user (step S112).

  If the user number K is equal to the number of users (YES in step S113), the mode setting unit 35 terminates. If the user number K is not equal (NO in step S113), the mode setting unit 35 increments the user number K and proceeds to step S106. Return.

As described above, according to the radio base station of the embodiment of the present invention, since the sounding information transmission frequency is changed based on the traffic volume and / or communication quality with the radio terminal, the communication throughput of the user data is reduced. Sounding information can be received normally while suppressing a decrease.
(Modification)
The present invention is not limited to the above embodiment. For example, the following modifications are also included.

(1) User-specific sounding non-execution mode FIG. 8 is a diagram illustrating another configuration of a frame transmitted in the user-specific sounding non-execution mode. FIG. 8 shows a case where the first to sixth users are set to the user-specific sounding non-execution mode.

  Referring to FIG. 8, user data of the first to sixth users is transmitted in this frame. No sounding information of any user is transmitted in the uplink subframe. User data of the first to sixth users uses all subchannels (all frequencies) in the uplink subframe and the downlink subframe. In this case, the subcarrier allocation method may be FUSC (Full Usage of Subchannels) or PUSC (Partial Usage of Subchannels), which are distributed subcarrier allocation methods.

(2) Period of Thinning Mode The N frame and M frame, which are periods in the thinning mode, may be variable according to the traffic amount and communication quality.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2, 42 1st antenna, 3, 43 2nd antenna, 4 1st transmission control unit, 5 2nd transmission control unit, 6 1st reception control unit, 7 2nd reception control unit, 67 Downlink beamforming unit, 9 Uplink beamforming unit, 10, 47 Modulation unit, 11, 48 Demodulation unit, 12 Sounding control unit, 13, 82 Control data management unit, 14, 83 User data management unit, 15, 20, 25 , 30, 52, 57, 62 RF section, 16, 21, 26, 31, 53, 58, 63 amplifier, 17, 22, 54 DAC, 27, 32, 59, 64 ADC, 18, 23, 55 IFFT section, 28, 33, 60, 65 FFT unit, 19, 24, 29, 34, 56, 61, 66 Subcarrier arrangement unit, 35 mode setting unit, 36 sounding information extraction unit, 37 SIN R calculation unit, 38 QoS management unit, 81 sounding information generation unit, 92 channel control unit.

Claims (8)

A setting unit configured to set the transmission frequency of the sounding information based on the traffic volume with the wireless terminal;
A control unit that instructs the wireless terminal to transmit sounding information at the set frequency;
A beam forming unit for imparting directivity to user data transmitted to the wireless terminal based on sounding information received from the wireless terminal;
The setting unit is configured to set so that sounding information is transmitted in every frame from all wireless terminals using sounding information when the traffic amount of the uplink subframe is less than a first predetermined value. . When the traffic volume of the uplink subframe is greater than or equal to the first predetermined value and the traffic volume of the downlink subframe is less than the second predetermined value, the setting unit uses all sounding information. from the wireless terminal, sounding information for each predetermined number of frames is set to be transmitted, the radio base station of claim 1, wherein. The setting unit sets the transmission frequency of sounding information based on the traffic volume and communication quality with the wireless terminal, the uplink subframe traffic volume is equal to or more than the first predetermined value, and the downlink When the traffic amount of the subframe of the link is equal to or greater than the second predetermined value, and the signal-to-interference and noise ratio of user data from the wireless terminal using sounding information is less than the third predetermined value, the radio The radio base station according to claim 2 , wherein the base station is configured to transmit sounding information every frame from the terminal. The setting unit uses sounding information when the traffic volume of the uplink subframe is equal to or greater than the first predetermined value and the traffic volume of the downlink subframe is equal to or greater than the second predetermined value. The radio base station according to claim 2 , wherein when the QoS of user data from the radio terminal is equal to or greater than a fourth predetermined value, the radio terminal is set to transmit sounding information in every frame. The setting unit sets the transmission frequency of sounding information based on the traffic volume and communication quality with the wireless terminal, the uplink subframe traffic volume is equal to or more than the first predetermined value, and the downlink When the traffic volume of the link subframe is greater than or equal to the second predetermined value, the signal-to-interference and noise ratio of user data from the wireless terminal using sounding information is greater than or equal to the third predetermined value and less than the fifth predetermined value. If the QoS of user data from the wireless terminal is less than a fourth predetermined value and greater than or equal to a sixth predetermined value, sounding information is transmitted from the wireless terminal for each predetermined number of frames. The radio base station according to claim 2 , configured as follows. The setting unit wirelessly uses sounding information when an uplink subframe traffic volume is equal to or greater than the first predetermined value and a downlink subframe traffic volume is equal to or greater than the second predetermined value. When the signal-to-interference noise ratio of user data from the terminal is equal to or higher than the fifth predetermined value and the QoS of user data from the wireless terminal is less than the sixth predetermined value, the sounding information is received from the wireless terminal. Is set to never be sent,
The control unit is configured so that user data in an uplink subframe is transmitted at the same frequency as user data in a downlink subframe to the wireless terminal configured not to transmit any sounding information. Instruct
6. The radio according to claim 5 , wherein, when no sounding information is transmitted, the beam forming unit gives directivity to user data to be transmitted to the radio terminal using a reference signal included in the received user data. base station. Setting the sounding information transmission frequency based on the traffic volume with the wireless terminal;
Instructing the wireless terminal to transmit sounding information at the set frequency;
Providing user data to be transmitted to the wireless terminal based on sounding information received from the wireless terminal ;
In the setting step, when the traffic amount of the uplink subframe is less than the first predetermined value, the radio base is set so that the sounding information is transmitted in every frame from all the radio terminals using the sounding information. Sounding control method in the station. To the computer that operates the radio base station,
Setting the sounding information transmission frequency based on the traffic volume with the wireless terminal;
Instructing the wireless terminal to transmit sounding information at the set frequency;
Based on sounding information received from the wireless terminal, causing the user data to be transmitted to the wireless terminal to have directivity ,
In the setting step, when the traffic amount of the uplink subframe is less than the first predetermined value, the radio base is set so that the sounding information is transmitted in every frame from all the radio terminals using the sounding information. Sounding control program in the station.

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