WO2010055741A1

WO2010055741A1 - Radio base station, communication method and program

Info

Publication number: WO2010055741A1
Application number: PCT/JP2009/067648
Authority: WO
Inventors: 正司平部
Original assignee: 日本電気株式会社
Priority date: 2008-11-12
Filing date: 2009-10-09
Publication date: 2010-05-20
Also published as: TW201108648A

Abstract

A radio base station (100), which uses OFDMA to communicate with a plurality of terminals (200-1 to 200-n) each having a wireless communication function, has a plurality of antennas. The radio base station (100) selects one of the plurality of antennas for transmitting signals to the terminals (200-1 to 200-n). The radio base station (100) switches an antenna that is to be selected, based on reception quality information received from the terminals (200-1 to 200-n), from the first antenna, which is currently selected, to a second antenna of the plurality of antennas, which is different from the first antenna.

Description

Wireless base station, communication method and program

The present invention relates to a radio base station, a communication method, and a program that transmit and receive signals using subcarriers, and in particular, orthogonal frequency division multiple access (OFDMA) that performs user separation in two dimensions of time and frequency in divided subcarriers. The present invention relates to a radio base station, communication method, and program using Orthogonal Frequency Division Multiplexing Access).

In recent years, a WiMAX (Worldwide Interoperability for Microwave Access) system has attracted attention as one of wireless communication systems. In this WiMAX system, a transmission method of adjacent subcarrier arrangement called Band-AMC (Adaptive Modulation and Coding) is used to improve the reception quality of radio signals.

This Band-AMC selects a subcarrier in a band having a good SNR (Signal to Noise Ratio) under frequency selective fading, and performs communication using the selected subcarrier. This improves the quality of the received signal.

Further, in order to improve the quality of the received signal, as another technique, a technique in which a single communication device is provided with a plurality of antennas has been considered (for example, see Patent Document 1).

For example, in the technique described in Patent Document 1, the transfer function between the antenna of the other station and each antenna of the own station is obtained, and the absolute value of the transfer function for the antenna used by the other station for packet transmission Alternatively, an antenna having a large addition value obtained by calculating and adding a power value of the absolute value is selected. In addition, this technique is applied to an orthogonal frequency division multiplexing (OFDM) system.

JP 2007-13547 A

However, when Band-AMC is used, since each user selects a subcarrier, the selected subcarriers may overlap (collision) with each other.

Also, in order to prevent the collision, there is a problem that complicated scheduling processing must be performed in the radio base station.

FIG. 1 is a diagram showing an example of subcarriers assigned to two users and fading characteristics.

User 1 selects a subcarrier that user 1 uses for communication based on the fading characteristics of user 1 indicated by a solid line. Further, the user 2 selects a subcarrier that the user 2 uses for communication based on the fading characteristic of the user 2 indicated by a broken line.

At this time, as shown in FIG. 1, there is a possibility that the subcarrier of the frequency where the fading characteristic of user 1 and the fading characteristic of user 2 overlap is selected by user 1 and user 2, in which case user 1 uses And the subcarrier used by the user 2 collide with each other.

FIG. 2 is a diagram schematically showing an example of scheduling processing in the radio base station when a subcarrier collision occurs as shown in FIG.

When a collision of subcarriers to be used occurs between users, the users are rearranged as shown in FIG.

This rearrangement is performed so that subcarriers used by a plurality of users do not collide with each other and the SNR characteristics of each user are good, and complicated scheduling processing is required. End up.

The technique described in Patent Document 1 relates to an OFDM system in which all subcarriers are allocated to one user, and OFDMA is used by a plurality of users by dividing subcarriers as in the WiMAX system. It is not applicable to the system.

An object of the present invention is to provide a communication device, a communication method, and a program that solve the above-described problems.

In order to achieve the above object, the present invention provides:
A wireless base station that communicates with a plurality of terminals having a wireless communication function using OFDMA (Orthogonal Frequency Division Multiplexing Access),
A plurality of antennas for transmitting and receiving radio signals to and from the terminal;
For each of the plurality of terminals, an antenna selection unit that selects one of the plurality of antennas for transmitting a signal to the terminal;
Based on the reception quality information transmitted from the terminal, the first antenna among the plurality of antennas from the first antenna selected by the antenna selection unit is selected by the antenna selection unit. A CQI decoder that instructs the antenna selection unit to switch to a second antenna other than
When the CQI decoder instructs the antenna selection unit to switch the antenna selected by the antenna selection unit from the first antenna to the second antenna, the antenna selection unit switches to the second antenna.

In addition, a connection method for connecting a plurality of terminals communicating with a radio base station using OFDMA (Orthogonal Frequency Division Multiplexing Access),
For each of the plurality of terminals, a process of selecting one antenna for transmitting a signal to the terminal among the plurality of antennas of the radio base station;
Based on reception quality information transmitted from the terminal, the antenna to be selected is switched from the currently selected first antenna to a second antenna other than the first antenna among the plurality of antennas. Processing.

In addition, a program to be executed by a radio base station that communicates with a plurality of terminals having a radio communication function using OFDMA (Orthogonal Frequency Division Multiplexing Access),
For each of the plurality of terminals, a procedure for selecting one antenna for transmitting a signal to the terminal from among a plurality of antennas of the radio base station;
Based on reception quality information transmitted from the terminal, the antenna to be selected is switched from the currently selected first antenna to a second antenna other than the first antenna among the plurality of antennas. And execute the procedure.

As described above, in the present invention, for each of a plurality of terminals having a wireless communication function, a plurality of antennas included in a wireless base station that communicates with the terminals using OFDMA (Orthogonal Frequency Division Multiplexing Access). Among them, one antenna for transmitting a signal to the terminal is selected, and based on the reception quality information transmitted from the terminal, the antenna to be selected is selected from the currently selected first antenna to a plurality of antennas. Since it is configured to switch to the second antenna other than the first antenna, collision of subcarriers used by a plurality of users can be avoided without performing complicated scheduling processing.

It is a figure which shows an example of the subcarrier allocated to two users, and a fading characteristic. FIG. 2 is a diagram schematically illustrating an example of scheduling processing in a radio base station when a subcarrier collision occurs as illustrated in FIG. 1. It is a figure which shows one Embodiment of the wireless base station of this invention. It is a figure which shows an example of an internal structure of the wireless base station shown in FIG. 5 is a flowchart for explaining a communication method for a terminal in the radio base station shown in FIG. It is a figure which shows typically the subcarrier which distributed the signal transmitted to a user to several antennas. It is a figure which shows the other example of an internal structure of the wireless base station shown in FIG. It is a flowchart for demonstrating the communication method with respect to the terminal in the wireless base station shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the radio base station of the present invention.

In the present embodiment, as shown in FIG. 3, the radio base station 100 of the present invention and a plurality of terminals 200-1 to 200-n (n is a natural number) are connected so as to be capable of radio communication. Between the radio base station 100 and the terminals 200-1 to 200-n, radio communication is performed using orthogonal frequency division multiple access (OFDMA) (Orthogonal Frequency Division Multiplexing Access).

Terminals 200-1 to 200-n are wireless communication terminals having a general wireless communication function.

The radio base station 100 is a base station that performs radio communication with the terminals 200-1 to 200-n.

FIG. 4 is a diagram illustrating an example of an internal configuration of the radio base station 100 illustrated in FIG.

As shown in FIG. 4, the radio base station 100 shown in FIG. 3 includes antennas 101-1 to 101-2, transmission / reception switching units 102-1 to 102-2, FFTs 103-1 to 103-2, and antennas. Selection sections 104-1 to 104-n, inverse FFTs 105-1 to 105-2, CQI decoder 106, CINR measurement section 107, frequency scheduler 108, and frequency selection section 109 are provided. Further, users 1 to n shown in FIG. 4 are signals (data) transmitted to terminals 200-1 to 200-n, respectively.

Antennas 101-1 to 101-2 transmit and receive radio signals to and from terminals 200-1 to 200-n. The antenna 101-1 and the antenna 101-2 have low correlation with each other.

The transmission / reception switching units 102-1 to 102-2 are connected to the antennas 101-1 to 101-2, and are switches for switching between transmission and reception according to time. When switching to transmission, signals output from FFTs 103-1 to 103-2 are transmitted to terminals 200-1 to 200-n via antennas 101-1 to 101-2, respectively. When switching to reception, signals received by antennas 101-1 to 101-2 are output to inverse FFTs 105-1 to 105-2, respectively.

The FFTs 103-1 to 103-2 perform fast Fourier transform (FFT) on the signals output from the antenna selection units 104-1 to 104-n and send the signals to the transmission / reception switching units 102-1 to 102-2. Output each.

Antenna selection sections 104-1 to 104-n transmit antennas 101-1 to 101-2 for transmitting signals output from frequency selection section 109 to terminals 200-1 to 200-n, from CQI decoder 106. Each is selected based on the output selection signal. Further, antenna selection sections 104-1 to 104-n output the signal output from frequency selection section 109 to the FFT connected to the selected antenna (transmission / reception switching section). That is, when the antenna 101-1 is selected, the signal output from the frequency selection unit 109 is output to the FFT 103-1 connected to the transmission / reception switching unit 102-1. When the antenna 101-2 is selected, the signal output from the frequency selection unit 109 is output to the FFT 103-2 connected to the transmission / reception switching unit 102-2. The antenna selection units 104-1 to 104-n are provided for each user (terminal).

The inverse FFTs 105-1 to 105-2 perform inverse fast Fourier transform on the signals output from the transmission / reception switching units 102-1 to 102-2, and output the signals to the CQI decoder 106 and the CINR measurement unit 107.

CQI decoder 106 decodes CQICH (Channel Quality Indication Channel) in the signals output from inverse FFTs 105-1 to 105-2, and the reception quality notified from terminals 200-1 to 200-n therein Is output to the antenna selectors 104-1 to 104-n and the frequency scheduler 108. The carrier power-to-interference + noise power ratio (CINR: Carrier to Interference and Noise power Ratio) is received. At this time, selection signals indicating whether or not to switch antennas for transmitting signals to terminals 200-1 to 200-n are output to antenna selection sections 104-1 to 104-n. Whether the antenna is switched is determined depending on whether CINR is a positive (+) value or a negative (-) value. When CINR is a positive (+) value, it is determined that the antenna is not switched from the currently used antenna. When CINR is a negative (−) value, it is determined that the antenna is switched to another antenna.

Further, the determination is not based on whether CINR is positive or negative, but may be based on whether CINR is equal to or greater than a preset threshold value. That is, when CINR is equal to or greater than a preset threshold value, it is determined that the antenna is not switched from the currently used antenna. If CINR is less than a preset threshold value, it is determined that the antenna is switched to another antenna.

Further, only when it is determined that the antenna is switched to another antenna, a selection signal may be output to the antenna selection units 104-1 to 104-n.

CINR measurement unit 107 measures CINR of signals output from inverse FFTs 105-1 to 105-2. Also, the CINR measurement unit 107 outputs the measured CINR to the frequency scheduler 108.

Based on the CINR output from the CQI decoder 106 and the CINR output from the CINR measurement unit 107, the frequency scheduler 108 uses adjacent subcarrier groups (for each of the terminals 200-1 to 200-n used for communication) (Hereinafter referred to as frequency). The adjacent subcarrier group is a unit composed of a plurality of adjacent subcarriers used in OFDMA and used for transmission and reception. After performing this scheduling, the frequency scheduler 108 outputs frequency information indicating which frequency each of the terminals 200-1 to 200-n uses to the frequency selection unit 109.

The frequency selection unit 109 associates the frequency information output from the frequency scheduler 108 with the signals to be transmitted to the corresponding terminals 200-1 to 200-n to the antenna selection units 104-1 to 104-n. Output. Alternatively, a signal to be transmitted to each of terminals 200-1 to 200-n may be output at an output timing corresponding to the frequency indicated by the frequency information output from frequency scheduler 108. At this time, the signal transmitted to terminal 200-1 is output to antenna selection section 104-1. Further, the signal transmitted to terminal 200-2 is output to antenna selection section 104-2. Further, a signal to be transmitted to terminal 200-n is output to antenna selection section 104-n. In this way, signals are output to antenna selection sections 104-1 to 104-n corresponding to terminals 200-1 to 200-n that transmit the signals.

FIG. 4 shows only the components according to the present invention among the components of the radio base station 100 shown in FIG.

The communication method in the form shown in FIG. 4 will be described below.

FIG. 5 is a flowchart for explaining a communication method for terminals 200-1 to 200-n in radio base station 100 shown in FIG.

First, a signal is transmitted from the radio base station 100 to an arbitrary antenna (for example, the antenna 101-1: first antenna) to the terminals 200-1 to 200-n, and from the terminals 200-1 to 200-n. When a signal is transmitted, the CINR of the transmitted signal is measured by the CINR measurement unit 107 in step 1.

The CINR measured by the CINR measurement unit 107 is output from the CINR measurement unit 107 to the frequency scheduler 108.

Then, the adjacent subcarrier group that maximizes the CINR of each user (terminal) is allocated in Step 2 from the adjacent subcarrier groups based on the CINR by the frequency scheduler 108. The allocated adjacent subcarrier group is output from the frequency scheduler 108 to the frequency selection unit 109 as frequency information.

Then, signals transmitted to terminals 200-1 to 200-n at frequency selection section 109 are sent to antenna selection sections 104-1 to 104-n at a timing according to the frequency information output from frequency scheduler 108. Is output.

In antenna selection sections 104-1 to 104-n, the current transmission antenna is antenna 101-1, so that the signal is output to FFT 103-1, so that the signal is transmitted from antenna 101-1. In step 3, the data is transmitted from the antenna 101-1 to the terminals 200-1 to 200-n.

Thereafter, the subsequent processing will be described by taking as an example a case where a signal is transmitted from the terminal 200-1 among the terminals 200-1 to 200-n. When the signal transmitted from the terminal 200-1 is received by the antenna 101-1, and is input from the transmission / reception switching unit 102-1 to the CQI decoder 106 via the inverse FFT 105-1, the signal is received in step 4. Is determined as CQICH by the CQI decoder 106. If the CQICH is determined to be CQICH, the CQICH is decoded by the CQI decoder 106, and whether the CINR reported therein is a positive (+) value or a negative (-) value is a step. 5 is discriminated by the CQI decoder 106.

Then, based on whether CINR is a positive (+) value or a negative (−) value, a selection signal for instructing whether to switch antennas is sent from the CQI decoder 106 to the antenna selection unit 104-1. Is output.

When the selection signal output from the CQI decoder 106 is an instruction to switch antennas, in step 6, the antenna selection unit 104-1 selects the antenna (antenna 101-1) that is currently selected from the antenna (antenna 101-1). -2: second antenna). That is, the signal transmitted from the frequency selection unit 109 and transmitted to the terminal 200-1 is output to the FFT 103-2 so as to be transmitted from the antenna 101-2. Then, a signal is transmitted from FFT 103-2 to terminal 200-1 via transmission / reception switching section 102-2 and antenna 101-2.

The same applies when signals are transmitted from other terminals 200-2 to 200-n. That is, the antennas are individually switched based on the CINR transmitted from each of the terminals 200-1 to 200-n.

FIG. 6 is a diagram schematically showing subcarriers in which a signal to be transmitted to a user is distributed to a plurality of antennas.

As shown in FIG. 6, when a signal is transmitted to all users 1 to n using only the antenna 101-1, subcarriers assigned to transmit the signal collide with each other. However, by assigning antennas to antennas 101-1 to 101-2 based on CINRs notified from terminals 200-1 to 200-n, subcarriers can be prevented from colliding with each other without performing complicated scheduling processing. be able to.

FIG. 7 is a diagram showing another example of the internal configuration of the radio base station 100 shown in FIG.

In this example, the radio base station 100 shown in FIG. 3 includes beam selection units 110-1 to 110-n and beam forming units instead of the antenna selection units 104-1 to 104-n shown in FIG. 111-1 to 111-m (m is a natural number).

The beam forming units 111-1 to 111-m impart directivity to the radio signals transmitted from the antennas 101-1 to 101-2 so that the radio signals reach only in a predetermined direction. The beam forming units 111-1 to 111-m form beams on the signals output from the beam selecting units 110-1 to 110-n and output them to the FFTs 103-1 to 103-2.

Beam selection sections 110-1 to 110-n correspond to terminals 200-1 to 200-n, respectively, and are based on selection signals output from CQI decoder 106, to terminals 200-1 to 200-n. Beam forming units 111-1 to 111-m that form beams of signals to be transmitted are selected. Further, the signal is output to the selected beam forming units 111-1 to 111-m.

In addition, the CQI decoder 106 in this example, with respect to the beam selection units 110-1 to 110-n, beam forming units 111-1 to 111- for transmitting signals to the terminals 200-1 to 200-n. A selection signal indicating whether to switch m is output. Whether or not to switch the beam forming units 111-1 to 111-m is determined depending on whether CINR is a positive (+) value or a negative (−) value. When CINR is a positive (+) value, it is determined that the beam forming unit is not switched from the currently used beam forming unit. If CINR is a negative (-) value, it is determined that the beam forming unit is switched to another beam forming unit. Further, only when it is determined that the beam forming unit is switched to another beam forming unit, a selection signal may be output to the beam selecting units 110-1 to 110-n.

Hereinafter, the communication method in the form shown in FIG. 7 will be described.

FIG. 8 is a flowchart for explaining a communication method for terminals 200-1 to 200-n in radio base station 100 shown in FIG.

First, a signal is transmitted from an arbitrary antenna (for example, antenna 101-1) to terminals 200-1 to 200-n from radio base station 100, while signals are transmitted from terminals 200-1 to 200-n. Then, the CINR of the transmitted signal is measured by the CINR measurement unit 107 in step 11. The beam forming unit used at this time is arbitrary (for example, the beam forming unit 111-1).

Then, an adjacent subcarrier group that maximizes the CINR of each user (terminal) is allocated in step 12 from the adjacent subcarrier groups based on CINR in frequency scheduler 108. The allocated adjacent subcarrier group is output from the frequency scheduler 108 to the frequency selection unit 109 as frequency information.

Then, signals transmitted to terminals 200-1 to 200-n at frequency selection section 109 are sent to beam selection sections 110-1 to 110-n at a timing corresponding to the frequency information output from frequency scheduler 108. Is output.

In the beam selectors 110-1 to 110-n, the current transmitting antenna is the antenna 101-1, and the beam forming unit is the beam forming unit 111-1. The signal is output to the FFT 103-1 via the beam forming unit 111-1 so that the signal is transmitted from the antenna 101-1, and in step 13 from the antenna 101-1 to the terminals 200-1 to 200 -n. Sent.

Thereafter, the subsequent processing will be described by taking as an example a case where a signal is transmitted from the terminal 200-1 among the terminals 200-1 to 200-n. When a signal transmitted from the terminal 200-1 is received by the antenna 101-1, and input from the transmission / reception switching unit 102-1 to the CQI decoder 106 via the inverse FFT 105-1, the signal is received in step 14. Is determined as CQICH by the CQI decoder 106. If the CQICH is determined to be CQICH, the CQICH is decoded by the CQI decoder 106, and whether the CINR reported therein is a positive (+) value or a negative (-) value is a step. At 15, the determination is made by the CQI decoder 106.

Then, based on whether CINR is a positive (+) value or a negative (−) value, a selection signal instructing whether or not to switch the beam forming unit is sent from the CQI decoder 106 to the beam selecting unit 110. To -1.

When the selection signal output from the CQI decoder 106 is an instruction to switch the beam forming unit, in step 16, the beam selecting unit 110-1 currently selected by the beam selecting unit 110-1 (the beam forming unit 111-1). The beam forming unit is switched to another beam forming unit (one of the beam forming units 111-2 to 111-m). That is, the signal transmitted from frequency selection section 109 and transmitted to terminal 200-1 is output from beam selection section 110-1 to one of beam forming sections 111-2 to 111-m. Then, signals formed by the beam forming units 111-2 to 111-m are transmitted from the FFT 103-1 to the terminal 200-1 via the transmission / reception switching unit 102-1 and the antenna 101-1.

The same applies when signals are transmitted from other terminals 200-2 to 200-n. That is, the beam forming unit is individually switched based on the CINR transmitted from each of the terminals 200-1 to 200-n.

In addition, although the case where the number of antennas is two has been described as an example, the same processing is performed even when there are three or more antennas without being limited to two.

Further, the above-described processing of the radio base station 100 may be performed by a logic circuit manufactured according to the purpose. Further, a program in which processing contents are described as a procedure is recorded on a recording medium readable by the radio base station 100, and the program recorded on the recording medium is read by the radio base station 100 and executed. good. The recording medium readable by the wireless base station 100 includes a removable recording medium such as a floppy disk (registered trademark), a magneto-optical disk, a DVD, and a CD, a ROM, a RAM, and the like built in the wireless base station 100. Memory, HDD, etc. The program recorded on the recording medium is read by a CPU (not shown) in the radio base station 100, and the same processing as described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes a program read from a recording medium on which the program is recorded.

Thus, since the antenna to be used is switched according to the CINR transmitted from the terminals 200-1 to 200-n, the frequency of starting the scheduler for assigning the frequency is reduced, and the scheduler load is reduced. Therefore, the signal processing time is shortened, and it is possible to cope with the high-speed movement of the terminals 200-1 to 200-n.

Note that the present invention is widely applicable to communication using OFDMA, and can be applied to, for example, LTE (Long Term Evolution) in addition to the WiMAX system.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2008-289951 filed on November 12, 2008, the entire disclosure of which is incorporated herein.

Claims

A wireless base station that communicates with a plurality of terminals having a wireless communication function using OFDMA (Orthogonal Frequency Division Multiplexing Access),
A plurality of antennas for transmitting and receiving radio signals to and from the terminal;
For each of the plurality of terminals, an antenna selection unit that selects one of the plurality of antennas for transmitting a signal to the terminal;
Based on the reception quality information transmitted from the terminal, the first antenna among the plurality of antennas from the first antenna selected by the antenna selection unit is selected by the antenna selection unit. A CQI decoder that instructs the antenna selection unit to switch to a second antenna other than
The antenna selection unit, when instructed by the CQI decoder to switch the antenna selected by the antenna selection unit from the first antenna to the second antenna, a radio base station that switches to the second antenna .
In the radio base station according to claim 1,
The CQI decoder instructs the antenna selection unit to switch the antenna selected by the antenna selection unit from the first antenna to the second antenna when the reception quality information is less than a predetermined threshold. A wireless base station characterized by that.
In the radio base station according to claim 1,
The CQI decoder switches the antenna selected by the antenna selection unit from the first antenna to the second antenna based on CINR (Carrier to Interference and Noise power Ratio) transmitted from the terminal. And instructing the antenna selector to a radio base station.
In the radio base station according to claim 3,
When the CINR is a negative value, the CQI decoder instructs the antenna selection unit to switch the antenna selected by the antenna selection unit from the first antenna to the second antenna. A wireless base station.
In the radio base station according to any one of claims 1 to 4,
A wireless base station used for a WiMAX (Worldwide Interoperability for Microwave Access) system.
A connection method for connecting a plurality of terminals communicating with a radio base station using OFDMA (Orthogonal Frequency Division Multiplexing Access),
For each of the plurality of terminals, a process of selecting one antenna for transmitting a signal to the terminal among the plurality of antennas of the radio base station;
Based on reception quality information transmitted from the terminal, the antenna to be selected is switched from the currently selected first antenna to a second antenna other than the first antenna among the plurality of antennas. And a connection method.
The connection method according to claim 6, wherein
A connection method comprising: switching the antenna to be selected from the first antenna to the second antenna when the reception quality information is less than a predetermined threshold.
The connection method according to claim 6, wherein
A connection method comprising a process of switching the antenna to be selected from the first antenna to the second antenna based on CINR (Carrier to Interference and Noise power Ratio) transmitted from the terminal .
The connection method according to claim 8,
When the CINR is a negative value, the connection method includes a process of switching the antenna to be selected from the first antenna to the second antenna.
To a radio base station that communicates with a plurality of terminals having a radio communication function using OFDMA (Orthogonal Frequency Division Multiplexing Access),
For each of the plurality of terminals, a procedure for selecting one antenna for transmitting a signal to the terminal from among a plurality of antennas of the radio base station;
Based on reception quality information transmitted from the terminal, the antenna to be selected is switched from the currently selected first antenna to a second antenna other than the first antenna among the plurality of antennas. A program that executes procedures.
The program according to claim 10, wherein
When the reception quality information is less than a predetermined threshold, a program for executing a procedure for switching the antenna to be selected from the first antenna to the second antenna.
The program according to claim 10, wherein
A program for executing a procedure of switching the antenna to be selected from the first antenna to the second antenna based on CINR (Carrier to Interference and Noise power Ratio) transmitted from the terminal .
The program according to claim 12,
When the CINR is a negative value, a program for executing a procedure of switching the antenna to be selected from the first antenna to the second antenna.