JP2003018074A - Wireless base station and beam control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless base station that can suppress an interference waves from an interference wave generating source, such as other wireless system and an electronic oven to make communication with a wireless terminal. SOLUTION: A beam forming network 11 uses a plurality of antenna elements 10 to form M pieces of beams orthogonal to each other. Each RTS(request to send) monitor 12 corresponding to the M pieces of beams monitors the RTS from the wireless terminal. A comparator 13 compares the reception levels of each RTS monitor to select the best beam. A transmission signal generating circuit 16 generates a CTS(clear to send) in response to the RTS. A beam selection circuit 17 selects the same beam as that selected by the comparator 13 at the reception of the RTS as a beam used for the transmission of the CTS to the wireless, terminal to control the beam forming network 11. Even if there is a interference generating source, if the wireless terminal exists in a direction different in terms of a beam space, the interference wave can be suppressed by the beam pattern and the base station can communicate with the wireless terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station and a beam control method using an adaptive array.

[0002]

2. Description of the Related Art CSMA such as IEEE 802.11
In the / CA method, communication is possible between each wireless terminal and a wireless base station, but when the wireless terminals cannot receive each other's transmission signals (for example, a shielding object exists between wireless terminals). This is the case when you do)
In addition, there is a "hidden terminal problem" in which each wireless terminal cannot know whether another wireless terminal is transmitting by carrier sense. In order to solve such a problem, IEEE 802.11 has an RTS function. Here, the RTS function means RTS (transmission request; Request) before the wireless terminal transmits a data packet.
By transmitting a packet called an "est To Send" packet, the wireless base station sends C
TS (Confirmation request; Clear To Send)
Send a packet called a packet. Each wireless terminal can receive the CTS packet transmitted from the wireless base station, and the information contained in the CTS packet can prevent the packet from being transmitted to a desired wireless terminal for a certain period of time. It will be possible. Therefore, only the desired wireless terminal can transmit the packet, so that the packet collision can be avoided.

[0003]

A wireless LAN system using the 2.4 GHz frequency band is a direct spread system (DS).
/ SS method) IEEE 802.11b using Bluetooth or frequency hopping (FH / SS method) using Bluetooth
There are plural such as th. Therefore, it is conceivable that the mutual systems become interference sources. Further, some devices such as microwave ovens which are not intended for wireless communication may interfere with this frequency band.

In a place where there are interference wave sources such as a plurality of wireless systems and microwave ovens, IEEE802.
There is a problem in that the wireless base station 11b may be interfered with, causing a malfunction in the RTS function and being unable to receive communication with the wireless terminal.

The present invention has been made in consideration of the above circumstances, and a radio base station and a beam for suppressing an interfering wave from an interfering wave generating source such as another radio system or a microwave oven and enabling communication with a radio terminal. The purpose is to provide a control method.

[0006]

The present invention comprises a plurality of antenna elements, and beam forming means for forming a plurality of beams having maximum directivity in different directions by using the plurality of antenna elements. A transmission request detection unit that detects the reception level of a transmission request transmitted by a wireless terminal from the reception signals by the plurality of beams formed by the beam forming unit; and the transmission request detected by the transmission request detection unit. A comparison unit that compares reception levels and selects at least one of them, and a beam selection unit that selects the beam corresponding to the transmission request selected by the comparison unit as a beam to be formed by the beam forming unit. It is characterized by having and.

[0007] Preferably, the beam selecting means is a beam formed by the beam forming means by the comparing means when transmitting a confirmation request responding to the transmission request selected by the comparing means to the wireless terminal. You may make it select the said beam corresponding to the selected said transmission request.

[0008] Preferably, the comparing means may select the reception level of the transmission request detected by the transmission request detecting means, whichever has the highest reception level of the reception signal.

The radio base station according to the present invention utilizes a plurality of antenna elements and the plurality of antenna elements,
At least, an omnidirectional beam and a beam forming means capable of selectively forming a beam that directs a directional null in a predetermined interference wave arrival direction, and a signal from a wireless terminal targeted by the own station. Filter means for passing a signal having a frequency component other than the frequency component having, a received power intensity detection means for detecting arrival of an interference wave based on the signal output passed through the filter means, and the received power intensity And a control unit that selects the beam to be formed by the beam forming unit based on whether or not the detection unit detects that the interference wave has arrived.

[0010] Preferably, the control means selects the omnidirectional beam when the arrival of the interference wave is not detected by the reception power intensity detection means,
When the reception power intensity detection means detects that the interference wave has arrived, a beam pattern that directs nulls of directivity in the predetermined arrival direction of the interference wave may be selected.

It should be noted that the present invention relating to the apparatus also holds as the invention relating to the method, and the present invention relating to the method also holds as the invention relating to the apparatus. According to the present invention, even in a situation where an interference wave from an interference wave source such as another wireless system or a microwave oven arrives, the interference wave can be easily detected, and the interference wave can be suppressed by the beam pattern. It becomes possible to communicate with.

Further, according to the present invention, the arrival timing of the packet is not known, and the beam pattern can be formed so as to suppress the interference wave without calculating the beam pattern in real time. The wireless base station can perform good communication.

Further, according to the present invention, when the direction of the fixed interference wave generation source is known, the influence of the interference wave can be avoided with a simpler configuration. Also,
When the interference wave is stopped, communication with the wireless terminal in the direction of the interference wave generation source is also possible.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2 shows a configuration example of a wireless communication system according to the embodiment of FIG. The wireless base station 1 and the wireless terminal 2 are, for example, IEEE80
It communicates by the CSMA / CA system in conformity with 2.11b. Further, in the present embodiment, it is assumed that there may be an interference wave generation source 5 (a device of another wireless communication system, a microwave oven, etc.) whose direction viewed from the wireless base station 1 is unknown. There may be a plurality of interference wave generation sources 5.

FIG. 2 shows a configuration example of the radio base station of this embodiment.

As shown in FIG. 2, the radio base station 1 is
L (L is a plurality) system antenna elements 10-1 to 10-
L, beamforming network 11, M (M is plural) RTS monitors 12-1 to 12-M, and comparator 1
3, a detection circuit 14, a communication processing unit 15, a transmission signal generation circuit 16, and a beam selection circuit 17. Note that FIG.
Then, the part relating to the RTS function is mainly shown.

The antenna elements 10-1 to 10-L and the beam forming network 11 are for realizing a beam space adaptive array. That is, in the beam-forming network 11, each received signal output incident from a plurality of predetermined antenna elements is weighted and combined (each received signal output is multiplied by a predetermined weight value by a weighted combiner and then combined). ) By controlling the beam pattern of the antenna element (for example, forming one beam having the maximum directivity or null in a specific direction), a plurality of weighting combiners are provided, and the weight corresponding to each antenna element is provided. By using a plurality of different values (weighting vectors) in parallel, M beams having maximum directivity in different directions (or mutually beam patterns are orthogonal to each other) are simultaneously formed. As a result, signals coming from different directions can be separated according to the directions of arrival. In addition, normally, it is configured by M = L or M <L.

The range of the direction served by the radio base station 1 may be any angle such as 90 °, 120 °, 180 ° or 360 °, and is not particularly limited. Further, each beam pattern may be uniform or non-uniform (in addition, there may be an overlapping portion between the beam patterns).

The signal received by the antenna element (all or part of 10-1 to 10-L) is generated by using the beam pattern generated by the beam forming network 11,
It is divided into multiple signals. At this time, the beam forming network 11 can generate different M orthogonal beam patterns, and can receive a signal coming from a range served by the radio base station 1. The signals received in each beam pattern are M RT
It is received by one of the S monitors 12-1 to 12-M corresponding to the beam pattern.

The RTS monitors 12-1 to 12-M obtain the reception level of the RTS packet by monitoring the RTS packet transmitted by the wireless terminal 2. Note that, for example, in IEEE802.11b, since the direct spreading method is used as the wireless communication method, the reception level at this time is
The received signal strength of the RTS packet after despreading or the received signal before despreading may be used.

The comparator 13 includes M RTS monitors 12-
The respective reception levels received at 1-12-M are compared and the one beam pattern that gives the best reception level is selected. Here, the best reception level is a reception state in which the reception power or the signal-to-noise power ratio is maximized, for example.

The comparator 13 may select one beam pattern from those whose reception level (for example, reception power or signal-to-noise power ratio) has reached a predetermined reference level. .

Further, the comparator 13 compares one beam pattern or a combination of a plurality of beam patterns and selects one beam pattern or a plurality of beam pattern groups that gives the best reception level. It is also possible to adopt such a configuration (in that case, an upper limit may be set for the number of selectable beam patterns). For example, the direction of a certain wireless terminal is, for example, 1 / of the maximum directivity of the beam pattern a.
In the case where the intensity direction is 2 and the intensity direction is, for example, 1/2 of the maximum directivity of the beam pattern b, the beam pattern a and the beam pattern b are selected, and a combination thereof is obtained. It is processed thereafter.

The signal received by the beam pattern selected by the comparator 13 is input to the detection circuit 14 and processed by the communication processing unit 15.

After that, the communication processing unit 15 causes the transmission signal generation circuit 16 to generate a CTS packet in response to the RTS packet of the wireless terminal 2.

C generated by the transmission signal generation circuit 16
The TS packet is the beam selection circuit 1 based on the result of the comparator 13 at the time of receiving the corresponding RTS packet.
The beam pattern selected by 7 (for example, the comparator 13
Using the same beam pattern as the beam pattern selected by, the antenna element (corresponding one of 10-1 to 10-L) transmits to the wireless section.

After that, the radio base station 1 can communicate with the radio terminal 2 using the selected beam pattern.

With such a configuration, even if there is an interference wave generation source 5 that interferes with a desired wave, if the wireless terminal 2 is in a direction different from the interference wave generation source 5 in terms of beam space as seen from the wireless base station 1, The interference wave can be suppressed by the beam pattern, and the packet from the wireless terminal 2 can be received. Further, even when transmitting a packet from the wireless base station 1 to the wireless terminal 2, the wireless terminal 2 can receive a signal with a high gain beam by using the beam pattern selected by the beam selection circuit 17. In addition, good communication can be performed. Further, even in a system in which the transmission power is restricted, by directing the beam pattern of the high-gain antenna element to the wireless terminal 2, it becomes possible to expand the serviceable range of the wireless base station 1.

FIG. 3 shows an example of the operation procedure of the radio base station 1 of this embodiment.

The wireless base station 1 forms an orthogonal beam so as to cover the entire wireless service range and stands by (S).
1).

It is determined whether or not there is a beam pattern receiving the RTS packet from the wireless terminal 2 at a predetermined level (S2).

If there is no beam pattern receiving the RTS packet from the wireless terminal 2 at a predetermined level (S2), the CTS packet is not transmitted (S3).

If there is a beam pattern that is receiving the RTS packet from the wireless terminal 2 at a predetermined level (S
2) Using the beam pattern, a CTS packet is transmitted to the wireless terminal 2 (S4), and then communication is performed with the wireless terminal 2 (S5).

Since the radio base station 1 transmits a packet to the radio terminal 2 by using a beam pattern having a high gain, the radio terminal 2 can perform good reception.
Further, since the wireless base station 1 narrows the beam to the wireless terminal 2 and transmits the beam, there is an advantage that interference given to other systems is suppressed.

FIG. 4 shows an example of the operation procedure of the wireless terminal 2 of this embodiment.

When the wireless terminal 2 needs to communicate communication information as a result of, for example, a predetermined internal process (S1).
1) First, carrier sense in a wireless space, which is a medium, is performed (S12).

If the wireless base station 1 or a wireless terminal other than the wireless terminal 2 is transmitting a signal and the RTS packet cannot be transmitted (S13), a predetermined time (for example, a random waiting time) is not elapsed. Wait (or change to another channel) (S14). Then, the process starts from the carrier sense in S12.

If the radio base station 1 is not transmitting any signal and the RTS packet can be transmitted (S13), R
The TS packet is transmitted (S15).

After that, if the CTS packet is not returned from the wireless base station 1 (S16), communication with the wireless base station 1 cannot be started, and a predetermined time elapses (or another Change to a channel) (or move to a direction where there is no interference wave generation source), and start again from carrier sensing in S12.

When the CTS packet is returned from the wireless base station 1 (S16), transmission / reception is performed with the wireless base station 1 (S17).

FIG. 5 shows an example of the overall sequence of this embodiment.

(1) Case in which Carrier Sense Fails The wireless terminal 2 first performs carrier sense (S2
1) If it is assumed that the wireless base station 1 is communicating with another wireless terminal at this time, an RTS packet cannot be transmitted, so that a predetermined time elapses (S2).
2).

(2) The carrier sense was successful, but CT
In the case where the reception of the S packet fails, the wireless terminal 2 performs carrier sensing again (S2
3) Here, if it is assumed that the communication between the wireless base station 1 and another wireless terminal is completed and the wireless base station 1 is in the standby state (S33), it is possible to transmit the RTS packet. Since I understand, I send an RTS packet (S2
4). At this time, if the reception state of the RTS packet is not good due to the interference wave from the interference wave generation source 5 as shown in FIG. 6, the wireless base station 1 cannot respond to this (S34). As a result, the wireless terminal 2 receives the CT
Since S packets cannot be received (S25),
It waits for a predetermined time to elapse (S26). here,
It is assumed that the wireless terminal 2 has moved its place.

(3) Case of Successful Reception of CTS Packet The wireless terminal 2 performs carrier sensing again (S2
7), for example, the RTS packet is transmitted as shown in FIG. 7 (S28). Here, it is assumed that the reception state of the RTS packet is improved due to the movement of the wireless terminal 2 (S35), and the wireless base station 1 responds to this by the CTS.
The packet is returned (S30). As a result, for example, FIG.
As described above, the wireless terminal 2 can receive the CTS packet (S29, S30). And the wireless base station 1
And the wireless terminal 2 communicate as shown in FIG. 9 (S3
1).

In the above (3), for example, FIG.
Even when the reception state of the RTS packet is improved by stopping the interference wave as in 0, the CTS packet is similarly returned from the wireless base station 1 to the wireless terminal 2 and communication between them is performed. It will be possible.

In the above, the radio base station 1 uses the RTS
The CTS packet is transmitted and the subsequent communication with the wireless terminal 2 is performed according to the beam pattern selected based on the reception level of the radio beam. CTS packet transmission using one or more beam patterns (including the case of using all beam patterns) and transmission to the wireless terminal 2 in the subsequent communication with the wireless terminal 2. Is also possible. It is also possible to make the range of the beam pattern, which is directionally adjacent to the selected beam pattern, to be the same between the transmission of the CTS packet and the subsequent communication with the wireless terminal 2. , It is possible to make them different.

(Second Embodiment) A configuration example of a wireless communication system is the same as that shown in FIG. However, here, it is assumed that the direction of the interference wave generation source 5 (devices of other wireless communication systems, microwave ovens, etc.) viewed from the radio base station 1 is known (there are a plurality of interference wave generation sources 5). It doesn't matter).

The operation procedure of the wireless terminal 2 is the same as that of the first embodiment (see FIGS. 4 and 5).

FIG. 11 shows a configuration example of the radio base station of this embodiment.

As shown in FIG. 11, the radio base station 1 has L
(L is a plurality) system antenna elements 30-1 to 30-L,
Beam forming network 32, wireless circuit 33,
Received power intensity (RSSI) detection circuit 34, control circuit 3
5, the filter 36 is provided. Note that in FIG. 2, RT
The part relating to the S function is mainly shown.

Antenna elements 30-1 to 30 of this embodiment
In the -L and beamforming network 32, at least a beam pattern that suppresses the interference wave input from the antenna elements 30-1 to 30-L and an omnidirectional beam pattern are formed. The wireless base station 1
For the range of directions served by 90 °, 120
It may be any angle such as °, 180 ° or 360 ° and is not particularly limited.

As the filter 36, a filter which does not pass the desired wave component is used, and the interference wave component is passed (it is considered that an interference wave having a larger bandwidth than the desired wave arrives). For example, FIG. 12A shows the band of the interference wave, and FIG.
12C is a band of radio waves used for communication with the wireless terminal 2, a filter having a characteristic as shown in FIG.

When the interference wave passes through the filter 36, the reception power intensity detector 34 detects the interference wave, and the reception power intensity detector 34 transmits the arrival of the interference wave to the control circuit 35.

If the interference wave has not arrived, the control circuit 35 receives the desired wave using, for example, an omnidirectional beam pattern as shown in FIG.

When the interference wave arrives, the control circuit 35 receives the desired wave by using a beam pattern formed to suppress the interference wave as shown in FIG. 14, for example.

The radio circuit 33 processes the received signal from the beamforming network 32 according to the beam pattern selected by the control circuit 35.

FIG. 15 shows C of the radio base station 1 of this embodiment.
An example of an operation procedure of a part related to SMA / CA will be shown. The radio base station 1 waits until receiving the RTS packet (S41). It is determined whether or not an RTS packet has been received from the wireless terminal 2 (S42). RT from wireless terminal 2
If the S packet is not received (S42), the CTS packet is not transmitted (S43). RT from wireless terminal 2
When the S packet is received (S42), the wireless terminal 2
The CTS packet is transmitted to the wireless terminal 2 (S44), and then communication is performed with the wireless terminal 2 (S5).

FIG. 16 shows an example of an operation procedure of a part related to beam control of the radio base station 1 of this embodiment. The interference wave is monitored (S51), and if the interference wave has not arrived (S5)
2), using an omnidirectional beam pattern (S53),
If the interfering wave has arrived (S52), the beam pattern formed so as to suppress the interfering wave is used (S54).

With such a configuration, it is possible to suppress the interference wave from the fixedly arranged interference wave generation source and switch the beam pattern with a simple structure to perform good communication.

Here, the occupied bandwidth of the interference wave component is effective when it is larger than the bandwidth of the desired wave. If the frequency of the desired wave uses a certain bandwidth and the interference wave radiates over a sufficiently large frequency bandwidth including the bandwidth used by the desired wave, the desired wave uses By looking at the power value of the band used by the interference wave other than the existing bandwidth, the radio base station can know that the interference wave has arrived.

For example, when a wireless terminal is communicating with a wireless base station at a frequency corresponding to ch1 in IEEE802.11b, interference waves from a microwave oven or the like have frequencies of ch1 to ch14 of IEEE802.11b. If interference is given to all of them, it is possible to know that the interference wave has arrived at the wireless base station by detecting the received power at the frequency corresponding to ch10 other than ch1 used by the wireless terminal.

For this reason, when an interference wave is arriving, a beam pattern for suppressing the interference wave is formed,
When the interference wave does not arrive, it is possible to form an omnidirectional beam pattern and receive the desired wave.
In this way, by switching the beam pattern,
By using the beam pattern that suppresses the interference wave, when the wireless terminal is in the interference wave direction and the interference wave from the interference wave source is not output, the wireless base station forms the beam pattern to generate the desired wave. It has the advantage of being able to suppress and avoid the inability to communicate.

Since the "beam pattern formed to suppress the interference wave" corresponding to the new direction is assumed, assuming that the interference wave generation source may be moved and fixed in another direction. The function of calculating and setting the weighting vector may be added. An example of the procedure in this case is shown in FIG.
Shown in. That is, after the interference wave generation source is moved, the direction of the interference wave is measured (S61), and a weighting vector for forming a beam pattern for directing a directivity null to the direction is calculated (S62), and is calculated. The weighted vector is set in the weighted combiner (S63). It is also possible to prepare a weighting vector for each direction of the interference wave source in advance and set a corresponding weighting vector by inputting information indicating the direction of the interference wave source from the outside. Is.

In the above, the radio base station 1 uses the beam pattern formed so as to suppress the interference wave when the interference wave arrives, and transmits the CTS packet.
After that, the communication with the wireless terminal 2 was performed.
Transmission of CTS packet and / or wireless terminal 2 thereafter
A method using an omnidirectional beam pattern is also possible for transmission to the wireless terminal 2 in communication with the wireless terminal.

The part of the configuration of the present embodiment that performs processing such as calculation is for causing a computer to execute a predetermined means (or for causing the computer to function as a predetermined means, or for a computer to perform a predetermined function). Can be implemented as a program, or can be implemented as a computer-readable recording medium recording the program.

Note that the configurations illustrated in the embodiments of the present invention are examples, and the present invention is not intended to exclude other configurations, and some of the illustrated configurations may be replaced with other configurations or illustrated. Other configurations that are obtained by omitting a part of the configuration, adding another function or element to the exemplified configuration, or combining them are possible. Also, another configuration logically equivalent to the exemplified configuration,
Other configurations including a portion logically equivalent to the exemplified configuration, another configuration logically equivalent to the main part of the exemplified configuration, and the like are possible. Further, another configuration that achieves the same or similar purpose as the exemplified configuration, another configuration that achieves the same or similar effect as the exemplified configuration, and the like are possible. Further, various variations of the various constituent parts illustrated in the embodiments of the present invention can be implemented in an appropriate combination. Further, the embodiments of the present invention include an invention as an individual device, an invention as to two or more related devices, an invention as an entire system, an invention as to a component inside an individual device, or a method corresponding thereto. It is intended to encompass and include inventions related to various viewpoints, stages, concepts or categories such as inventions. Therefore, the invention disclosed in the embodiments of the present invention can be extracted without being limited to the exemplified configurations.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the technical scope thereof. For example, RTS may be replaced with a data packet and CTS with an ACK packet.

[0069]

According to the present invention, even in the situation where an interference wave arrives, the interference wave can be suppressed by the beam pattern and communication with the wireless terminal becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a wireless communication system according to first and second embodiments of the present invention.

FIG. 2 is a diagram showing a configuration example of a radio base station according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing an example of an operation procedure of the wireless base station according to the embodiment.

FIG. 4 is a flowchart showing an example of an operation procedure of the wireless terminal according to the embodiment.

FIG. 5 is a diagram showing an example of an overall sequence according to the same embodiment.

FIG. 6 is a diagram for explaining the relationship between a wireless base station, a wireless terminal, and an interference wave generation source.

FIG. 7 is a diagram for explaining the relationship between a wireless base station, a wireless terminal, and an interference wave generation source.

FIG. 8 is a diagram for explaining a relationship between a wireless base station, a wireless terminal, and an interference wave generation source.

FIG. 9 is a diagram for explaining the relationship between a wireless base station, a wireless terminal, and an interference wave generation source.

FIG. 10 is a diagram for explaining the relationship between a wireless base station, a wireless terminal, and an interference wave generation source.

FIG. 11 is a diagram showing a configuration example of a radio base station according to the second embodiment of the present invention.

FIG. 12 is a diagram for explaining a relationship between a band of a desired wave, a band of an interference wave, and identification of a filter of a radio base station

FIG. 13 is a diagram for explaining a relationship between a radio base station and an interference wave generation source.

FIG. 14 is a diagram for explaining the relationship between a radio base station and an interference wave generation source.

FIG. 15 is a CSMA / C of the radio base station according to the embodiment.
The flowchart which shows an example of the operation procedure related to A.

FIG. 16 is a flowchart showing an example of an operation procedure related to beam control of the wireless base station according to the embodiment.

FIG. 17 is a flowchart showing an example of an operation procedure related to weighting vector calculation of the radio base station according to the embodiment.

[Explanation of symbols]

10-1 to 10-L, 30-1 to 30-L ... Antenna elements 11, 32 ... Beam forming networks 12-1 to 12-M ... RTS monitor 13 ... Comparator 14 ... Detection circuit 15 ... Communication processing unit 16 ... Transmission signal generation circuit 17 ... Beam selection circuit 33 ... Radio circuit 34 ... Reception power intensity detection circuit 35 ... Control circuit 36 ... Filter

Continued front page    (72) Inventor Shuichi Obayashi             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center F-term (reference) 5J021 AA05 DB01 EA04 GA02 GA06                       GA07 GA08 HA05                 5K067 AA03 BB21 CC10 EE02 EE10                       KK02 KK03

Claims (11)

[Claims] 1. A plurality of antenna elements, beam forming means for forming a plurality of beams having maximum directivity in different directions using the plurality of antenna elements, and the beam forming means. From the received signals by the plurality of beams, the transmission request detection means for detecting the reception level of the transmission request transmitted by the wireless terminal, and the reception level of the transmission request detected by the transmission request detection means is compared, And a beam selection unit that selects the beam corresponding to the transmission request selected by the comparison unit as a beam to be formed by the beam forming unit. Wireless base station. 2. The beam selecting means selects by the comparing means as a beam to be formed by the beam forming means when transmitting a confirmation request in response to the transmission request selected by the comparing means to the wireless terminal. The radio base station according to claim 1, wherein the beam corresponding to the transmitted transmission request is selected. 3. The beam selecting means corresponds to the transmission request selected by the comparing means as a beam to be formed by the beam forming means when transmitting and receiving with the wireless terminal that has transmitted the confirmation request. The radio base station according to claim 1, wherein a beam is selected. 4. The radio base station according to claim 1, wherein the plurality of beams are beams orthogonal to each other. 5. The comparing means selects one of the reception levels of the transmission request detected by the transmission request detecting means, which has the highest reception level of the reception signal. The radio base station according to. 6. The comparison means selects, from among the transmission requests whose reception level has reached a predetermined reference level, the one having the highest reception level of the reception signal. The radio base station according to claim 5. 7. The radio base station according to claim 6, wherein the reception level is reception power or a signal-to-noise power ratio. 8. A plurality of antenna elements, and using the plurality of antenna elements, at least an omnidirectional beam and a beam for directing a directional null in a predetermined arrival direction of an interference wave are selected. Based on the signal output passed through the filter means, a beam forming means that can be formed selectively, a filter means that passes a signal having a frequency component other than the frequency component of the signal from the wireless terminal targeted by the local station, and A received power intensity detecting means for detecting arrival of an interference wave, and the beam forming means for causing the beam forming means to form the received power intensity detecting means based on whether or not the arrival of the interference wave is detected. And a control unit for selecting the radio base station. 9. The control means selects the omnidirectional beam when the arrival of the interference wave is not detected by the reception power intensity detection means, and the reception power intensity detection means selects the omnidirectional beam. 9. The radio base station according to claim 8, wherein when the arrival of an interference wave is detected, a beam pattern for directing a directivity null in the predetermined arrival direction of the interference wave is selected. 10. A beam control method in a radio base station, comprising a beam forming means for forming a plurality of beams having maximum directivity in different directions by using a plurality of antenna elements. Means for detecting the transmission request transmitted by the wireless terminal from the received signals by the plurality of beams formed by the means, comparing the detected transmission requests, and selecting at least one of them; The beam control method characterized in that the beam corresponding to the selected transmission request is selected as the beam to be formed by the beam control method. 11. Beam forming capable of selectively forming at least an omnidirectional beam and a beam directing a directional null in a predetermined arrival direction of an interference wave by using a plurality of antenna elements. A beam control method in a radio base station comprising means, wherein the filter allows a signal having a frequency component other than the frequency component of the signal from the wireless terminal of interest to the station to pass, and the signal passed through the filter. A beam control method characterized by detecting whether or not an interference wave has arrived based on an output, and selecting the beam to be formed by the beam forming means based on a detection result regarding arrival of the interference wave. .