JP2004235710A - Wireless frequency selecting method, wireless communication system, wireless terminal station apparatus, and wireless base station apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless frequency selection method whereby a frequency with a low congestion degree can easily be selected in a short time as a frequency used by a wireless terminal station for communication with a wireless base station, and to provide a wireless communication system, the wireless terminal station, and the wireless base station. <P>SOLUTION: The wireless frequency selecting method disclosed herein includes: a step (1) wherein the wireless terminal station ST<SB>M</SB>searches a base station identification signal while sequentially switching a plurality of frequencies assigned to the wireless communication system; a step (2) wherein the wireless terminal station ST<SB>M</SB>extracts identification information from the base station identification signal detected by searching and records the identification information in cross-reference with a frequency at which the base station identification signal is detected; a step (3) wherein the wireless terminal station ST<SB>M</SB>respectively obtains the number of the wireless base stations A<SB>N</SB>using each frequency from the identification information recorded in cross-reference with each frequency; a step (4) wherein the wireless terminal station ST<SB>M</SB>selects a frequency on the basis of the number of the wireless base stations A<SB>N</SB>using each frequency. Since the wireless terminal station selects the frequency on the basis of the number of the wireless base stations using each frequency when selecting the frequency used for communication with the wireless base station, the wireless terminal station grasps a state of each frequency in a short time and selects a proper frequency to start the communication. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication system and apparatus such as a wireless LAN (Local Area Network) and a frequency selection method thereof.
[0002]
[Prior art]
In many companies, a large number of LAN cables are installed in an office, which causes problems in terms of space and appearance. Further, the line connection of the corporate LAN is changed due to various factors such as a change in organization, a layout change in an office, and a rearrangement of OA equipment. In general, communication devices and LAN cables are arranged in an inconspicuous place, such as under the floor of a free access floor or between desks, so that workability is poor when a connection is changed. Therefore, changing the connection of the LAN cable requires a large amount of labor.
[0003]
If a LAN spreads in the home, a similar problem would occur there. That is, a great deal of labor is required to change the arrangement of the personal computer, the OA equipment, the home electric appliances, and the like in accordance with the change of the room.
[0004]
As a means for solving this problem, a wireless LAN, which eliminates a communication cable from an office or home by reducing the number of lines and reduces the labor for changing the connection, has attracted attention. If a wireless LAN is used, the number of communication cables in the office is reduced, and the degree of freedom of arrangement and movement of the OA equipment is improved.
[0005]
As an example of a wireless LAN system, an OA device can be connected to a LAN by wirelessly connecting a wireless base station connected to a wired LAN and a wireless terminal station mounted on an OA device such as a personal computer or a printer. There is something.
[0006]
In this type of wireless LAN system, a plurality of wireless base stations may be provided adjacent to each other to cover an office as a service area. In that case, it is preferable that adjacent radio base stations use different frequencies from each other in order to avoid radio wave interference.
[0007]
A wireless terminal station located at a position where it can receive a plurality of radio waves having different frequencies transmitted from a plurality of wireless base stations, respectively, selects any one of these frequencies for communication. As a selection method, there is a method of selecting a signal having the best reception quality from a plurality of frequencies. Then, the quality of the reception quality is determined by, for example, the reception electric field strength (for example, see Patent Document 1). The received electric field strength is usually measured for each frequency used in the radio base station.
[0008]
However, since the frequencies that can be used in the wireless LAN system are limited, there may be cases where a plurality of base stations have to use the same frequency. The reach of the radio wave of the wireless LAN system varies depending on the surrounding conditions such as the height of a ceiling, the position of a wall or an obstacle, and the like. Therefore, it is sufficiently conceivable that signals from a plurality of wireless base stations using the same frequency can be received by one wireless terminal station, and that transmission signals interfere with each other between the wireless base stations. Each wireless base station using the same frequency has a different distance from the wireless terminal station, and also has different installation conditions. Therefore, it is difficult to determine the reception quality by measuring the reception electric field strength for each frequency.
[0009]
On the other hand, as another method of selecting one of the frequencies, there is a method of selecting a line having the lowest congestion degree from radio waves transmitted from a plurality of wireless base stations. Then, in order to select the line with the lowest congestion degree, for example, the time during which the medium of the line is used is measured. As a result, if the line with the lowest congestion degree can be selected, the wireless terminal station can perform effective high-speed communication.
[0010]
[Patent Document 1]
JP-A-11-205342
[0011]
[Problems to be solved by the invention]
It is desirable to select a line in a short time. Therefore, in the method of measuring the usage time of the medium, it is necessary to determine the congestion degree of the line in a short time. However, it is difficult to judge the average congestion degree of the line by short-time measurement, and an error increases. Further, in a system in which a wireless base station performs access control by polling a wireless terminal station, a difference in the usage time of a medium does not appear at a certain degree of congestion or more, and thus the congestion degree cannot be determined by this method. .
[0012]
An object of the present invention is to provide a radio frequency selection method, a radio communication system, a radio terminal station, and a radio base station that can easily select a low-congestion frequency in a short time.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the radio frequency selection method of the present invention is that a plurality of radio base stations transmit a base station identification signal including their own identification information using a frequency determined for each, In a wireless communication system in which a plurality of wireless terminal stations identify each wireless base station by its base station identification signal, select any one of the frequencies, and connect to and communicate with a wireless base station using that frequency, A radio frequency selection method for a radio terminal station to select any frequency, the first step of searching for a base station identification signal while sequentially switching a plurality of frequencies assigned to a radio communication system, A second step of extracting identification information from the base station identification signal detected by the search and recording the identification information in association with the detected frequency of the base station identification signal; A third step of calculating the number of radio base stations using each frequency from the identification information recorded in the third step, and a fourth step of selecting a frequency based on the number of radio base stations using each frequency. Steps.
[0014]
Therefore, according to the present invention, when selecting a frequency to be used for communication with a wireless base station, the wireless terminal station selects a frequency based on the number of wireless base stations using each frequency.
[0015]
In the fourth step, a frequency that is used by at least one radio base station and that uses the least number of radio base stations may be selected.
[0016]
Therefore, the wireless terminal station selects a frequency that is used by at least one wireless base station and uses the least number of wireless base stations, and starts communication using that frequency.
[0017]
In addition, the existing wireless base station transmits a base station identification signal including its own identification information using a frequency determined for each of them, and the new wireless base station uses the base station identification signal to transmit the surrounding wireless base station. In a wireless communication system that identifies a wireless base station, selects one of the frequencies, and uses that frequency for communication with a wireless terminal station, a new wireless base station selects a wireless frequency to select one of the frequencies. A first step of searching for a base station identification signal while sequentially switching a plurality of frequencies assigned to a wireless communication system, and extracting identification information from the base station identification signal detected by the search; The second step of recording in association with the detected frequency of the base station identification signal and the identification information recorded in association with each frequency determine whether each frequency is used. A third step of determining the number of base stations, respectively, and a fourth step of selecting a frequency based on the number of radio base stations using the respective frequencies.
[0018]
Therefore, according to the present invention, when a radio base station selects a frequency to be used at the time of new establishment, the radio base station selects a frequency based on the number of existing radio base stations using each frequency.
[0019]
In the fourth step, a frequency that uses the least number of radio base stations may be selected.
[0020]
Therefore, the radio base station selects a frequency that uses the least number of existing radio base stations and starts communication using that frequency.
[0021]
The wireless communication system of the present invention transmits a base station identification signal including identification information of each of the plurality of frequencies assigned to the wireless communication system, using a frequency determined for each of the plurality of frequencies. To search for a base station identification signal while sequentially switching a plurality of frequencies with a plurality of wireless base stations connected to and communicating with a wireless terminal station, and extracting identification information from the base station identification signal detected by the search. The mobile station has at least one wireless terminal station that identifies a wireless base station from the identification information and selects a frequency based on the number of wireless base stations using each frequency.
[0022]
In addition, the radio terminal station may select a frequency used by at least one radio base station and using the least number of radio base stations among them.
[0023]
Another wireless communication system according to the present invention is a wireless communication system to which a plurality of frequencies used for communication using wireless signals are assigned, and which includes a base station including identification information of a wireless base station while sequentially switching a plurality of frequencies when newly installed. A search is made for a station identification signal, identification information is extracted from the base station identification signal detected by the search, a wireless base station is identified from the identification information, and the number of existing wireless base stations using each frequency is determined. A plurality of radio base stations that select a frequency to be used based on the base station and transmit a base station identification signal including their own identification information using the frequency,
At least one wireless terminal station that identifies each wireless base station by identification information extracted from base station identification signals transmitted from a plurality of wireless base stations and communicates with any one of the wireless base stations .
[0024]
Further, the radio base station may select a frequency that uses the least number of radio base stations.
[0025]
In the wireless terminal station according to the present invention, at least one wireless base station transmits a base station identification signal including identification information of each of the base stations using a frequency determined for the base station. In a wireless communication system that identifies each wireless base station by a station identification signal, selects one of the frequencies, and connects to and communicates with the wireless base station using the frequency, the wireless communication system selects one of the frequencies. A terminal station, a wireless transmitting and receiving circuit capable of transmitting and receiving wireless signals by switching a plurality of frequencies assigned to the wireless communication system, a frequency switching control circuit for controlling switching of the frequency of the wireless transmitting and receiving circuit, and a plurality of frequencies Instruct the frequency switching control circuit to sequentially switch, search for the base station identification signal at each frequency, and extract from the base station identification signal detected by the search The identified identification information is recorded in association with the detected frequency of the base station identification signal, and the number of radio base stations using each frequency is calculated from the identification information recorded in association with each frequency. It has a control unit for selecting a frequency based on the frequency.
[0026]
Further, the control unit may select a frequency used by at least one radio base station and among which the number of radio base stations used is the smallest.
[0027]
According to the radio base station of the present invention, an existing radio base station transmits a base station identification signal including its own identification information using a frequency determined for each base station. A wireless base station that identifies surrounding radio base stations by an identification signal, selects one of the frequencies, and uses that frequency for communication with a wireless terminal station. A radio transmitting and receiving circuit that can transmit and receive a radio signal by switching a plurality of frequencies assigned to the radio communication system, a frequency switching control circuit that controls switching of the frequency of the radio transmitting and receiving circuit, It instructs the frequency switching control circuit to sequentially switch the frequency, searches for the base station identification signal at each frequency, and extracts from the base station identification signal detected by the search. The identified identification information is recorded in association with the detected frequency of the base station identification signal, and the number of wireless base stations using each frequency is determined from the identification information recorded in association with each frequency. It has a control unit for selecting a frequency based on the frequency.
[0028]
Also, the control unit may select a frequency that uses the least number of wireless base stations.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described in detail with reference to the drawings.
[0030]
FIG. 1 is a diagram illustrating a configuration of a wireless LAN system according to the present embodiment. Referring to FIG. 1, a wireless LAN system according to this embodiment includes a wireless terminal station ST. _M (Where M = 1 to 8) and the radio base station A _N (Here, N = 1 to 4).
[0031]
Wireless terminal station ST _M Is mounted or built in OA equipment such as a personal computer or a printer, and any of the wireless base stations A _N To send and receive data by connecting with a wireless line. For example, the wireless terminal station ST _M Is a radio base station A transmitting a radio wave that ensures a predetermined reception quality. _N Connect with
[0032]
Wireless base station A _N Is one of the wired networks NM _L (Where L = 1 to 3), and is connected to the wireless terminal station ST by a wireless line of any frequency usable in the wireless LAN system. _M To send and receive data. The wireless LAN system is assigned wireless lines of a plurality of frequencies.
[0033]
Wireless base station A _N Is a wireless terminal station ST in a range where a predetermined reception quality is ensured. _M And the wireless terminal station ST _M Provides a service that enables data communication. The range in which the predetermined reception quality is secured is defined as the radio base station A _N Service area. A service provided within one service area by one radio base station AN is referred to as a basic service unit BSS. _N And That is, one radio base station A _N One basic service unit BSS _N Is configured. And one basic service unit BSS _N By a plurality of wireless terminal stations ST _M Can receive data communication services.
[0034]
Wired network NW _L Is a network connected by a wired line, for example, Ethernet.
[0035]
In the example of FIG. ₁ Is a wired network NW ₁ It is connected to the. Wireless base station A ₂ , A ₃ Is a wired network NW ₂ It is connected to the. Wireless base station A ₄ Is a wired network NW ₃ It is connected to the.
[0036]
Also, the radio base station A ₁ To the wireless terminal station ST ₂ , ST ₃ Is connected. Wireless base station A ₂ Is the wireless terminal station ST ₄ , ST ₅ Is connected. Wireless base station A ₃ Is the wireless terminal station ST ₆ , ST ₇ Is connected. Wireless base station A ₄ Is the wireless terminal station ST ₈ Is connected. Wireless terminal station ST ₁ Has not yet connected to any radio base stations.
[0037]
Also, the radio base station A ₁ Is the frequency F ₁ Basic service unit BSS using ₁ Is provided. Wireless base station A ₂ Is the frequency F ₁ Basic service unit BSS using ₂ Has provided. Wireless base station A ₃ Is the frequency F ₂ Basic service unit BSS using ₃ Is provided. Wireless base station A ₄ Is the frequency F ₃ Basic service unit BSS using ₄ Is provided. Normally, in a wireless LAN system, adjacent wireless base stations use different frequencies, and a place where radio waves transmitted from a plurality of wireless base stations using the same frequency can be received is minimized. However, since the frequency that can be used in the wireless LAN system is usually as small as 3 to 4, there must be a place where radio waves transmitted from a plurality of wireless base stations using the same frequency can be received, as in the present embodiment. There is.
[0038]
Wired network NW ₁ ~ NW ₃ May be interconnected by a wired communication device (not shown), for example, a router.
[0039]
Here, the wireless terminal ST ₁ Is one of the basic service BSS _N Suppose you are about to join and start communication. In FIG. 1, the wireless terminal station ST ₁ Is the wireless base station A ₁ , A ₂ , A ₃ You are in a position where you can receive the radio waves transmitted from. Wireless base station A ₁ And wireless base station A ₂ Is the same frequency F ₁ Is used.
[0040]
FIG. 2 is a block diagram showing a configuration of the wireless base station shown in FIG. Referring to FIG. 2, the radio base station A _N Has a wireless transmission / reception circuit 1, a medium access control circuit 2, a transmission / reception data buffer 3, a wired interface circuit 4, a base station control unit 5, and a frequency switching control circuit 6. From wireless line to wired network NW _L In the meantime, the wireless transmission / reception circuit 1, the medium access control circuit 2, the transmission / reception data buffer 3, and the wired interface circuit 4 are connected in this order. The medium access control circuit 2, the transmission / reception data buffer 3, the wired interface circuit 4, and the frequency switching control circuit 6 are controlled by the base station control unit 5. The wireless transmission / reception circuit 1 is controlled by the frequency switching control circuit 6.
[0041]
The wireless transmission / reception circuit 1 transmits / receives a signal via a wireless line of a frequency designated by the frequency switching control circuit 6, and further modulates / demodulates the signal.
[0042]
The medium access control circuit 2 controls access to a wireless line as a communication medium. Here, it is assumed that the medium access control circuit 2 performs medium access control conforming to IEEE 802.11 which is one of the standard protocols of the wireless LAN.
[0043]
The transmission / reception data buffer 3 buffers transmission / reception data.
[0044]
The wired interface circuit 4 is connected to a wired network NW _L Interface circuit.
[0045]
The base station control unit 5 is controlled by a microprocessor, performs setting and control on each unit, and operates them in cooperation.
[0046]
The frequency switching control circuit 6 selects a frequency to be used in the basic service unit according to the control of the base station control unit 5 and instructs the radio transmission / reception circuit 7. This selection is not changed frequently, and usually the same frequency is used continuously.
[0047]
FIG. 3 is a diagram showing a frame format of a beacon signal transmitted from the wireless base station shown in FIG. This frame format is specified in IEEE 802.11.
[0048]
The beacon signal is transmitted from the radio base station A transmitting a receivable radio wave. _N Includes the identification information. The beacon signal is transmitted to each radio base station A _N From that radio base station A _N Is transmitted at a constant cycle according to the signal of the frequency used in. Wireless terminal station ST _M Is a radio base station A transmitting a receivable radio wave by a beacon signal. _N And recognize its frequency.
[0049]
Referring to FIG. 3, the beacon signal is a signal having a frame configuration. Here, the frame is called a beacon frame. The beacon frame includes a preamble 101, a medium access control header 102, BSS control information 103, and an FCS (frame check sequence) 104. The medium access control header 102 includes a frame identifier 105, a destination address 106, a BSSID 107, and other access control information 108.
[0050]
The preamble 101 is a bit pattern indicating the head of a frame. The medium access control header 102 is various types of header information used for medium access control. The BSS control information 103 includes a basic service unit BSS. _N Wireless terminal station ST for controlling _M Is the information sent to FCS is the wireless terminal station ST _M , A CRC calculation result used for detecting a bit error of a frame is inserted.
[0051]
The frame identifier 105 is identification information indicating the type of the frame, and identification information indicating that is inserted in the beacon frame. The destination address 106 is information indicating the destination of the frame, and information indicating broadcast is inserted in the beacon frame. Therefore, the beacon frame is transmitted to its radio base station A _N All radio terminal stations ST that can receive radio waves transmitted from ^M Is obtained by BSSID 107 is a radio base station A that is a frame transmission source. _N Basic service unit BSS _N Is information indicating Here, the radio base station A _N The same value as the MAC address is used, and is a unique value for each wireless base station.
[0052]
FIG. 4 is a block diagram showing a configuration of the wireless terminal station shown in FIG. Referring to FIG. 4, the wireless terminal station ST _M Has a wireless transmission / reception circuit 7, a medium access control circuit 8, a transmission / reception data buffer 9, an internal interface circuit 10, a terminal station control unit 11, and a frequency switching control circuit 12. A wireless transmission / reception circuit 7, a medium access control circuit 8, a transmission / reception data buffer 9, and an internal interface circuit 10 are connected in this order from the wireless line to the OA equipment. The medium access control circuit 8, transmission / reception data buffer 9, internal interface circuit 10, and frequency switching control circuit 12 are controlled by the terminal station control unit 11. The wireless transmission / reception circuit 7 is controlled by the frequency switching control circuit 12.
[0053]
The wireless transmission / reception circuit 7 transmits / receives a signal via a wireless line of the frequency specified by the frequency switching control circuit 12, and further modulates / demodulates the signal.
[0054]
The medium access control circuit 8 controls access to a wireless line as a communication medium. Here, it is assumed that the medium access control circuit 8 performs medium access control conforming to IEEE 802.11 which is one of the standard protocols of the wireless LAN.
[0055]
The transmission / reception data buffer 9 buffers transmission / reception data.
[0056]
The internal interface circuit 10 is an interface circuit that is connected to OA equipment such as a personal computer and a printer, and a home appliance that can be connected to a LAN.
[0057]
The terminal station control unit 11 is controlled by a microprocessor, performs setting and control for each unit, and causes them to operate in cooperation. For example, when participating in one of the basic service units, first, the terminal station control unit 11 controls the medium access control circuit 8 while controlling the frequency switching control circuit 12 to switch the frequency used in the radio transmitting and receiving circuit 7. Wireless base station A using each frequency _N Recognize. Next, at least one radio base station A _N Used by the radio base station A _N Is selected and the frequency switching control circuit 12 is controlled to switch the frequency of the wireless transmission / reception circuit 7 to that frequency. Then, the radio base station A using the frequency _N , The transmission / reception of data using the transmission / reception data buffer 9 and the internal interface circuit 10 is started.
[0058]
The frequency switching control circuit 12 selects a frequency to be used for transmitting and receiving data to and from the base station according to the control of the terminal station control unit 11 and instructs the wireless transmitting and receiving circuit 7.
[0059]
FIG. 5 is a sequence diagram showing an operation of the wireless LAN system when the wireless terminal station selects a frequency used for data transmission and reception. Here, a new wireless terminal station ST ₁ Is trying to join one of the basic service units.
[0060]
Wireless terminal station ST ₁ Is located as shown in FIG. ₁ , A ₂ , A ₃ Can receive the radio wave transmitted from. Also, the radio base station A ₁ And wireless base station A ₂ Is the same frequency F ₁ You are using Wireless base station A ₃ Is a different frequency F ₂ You are using
[0061]
Referring to FIG. 5, the radio base station A ₁ Represents all frequencies F used in the wireless LAN system. ₁ , F ₂ , F ₃ Search for beacon frames received in step (1). The search for the beacon frame is performed for a period sufficiently long with respect to the transmission cycle of the beacon frame.
[0062]
Wireless terminal station ST _M When detecting a beacon frame, the radio base station A that has transmitted the beacon frame from the BSSID contained in the beacon frame, that is, the MAC address. _N Can be recognized.
[0063]
First, the frequency F ₁ Search for the beacon frame of the wireless terminal station ST ₁ Is the wireless base station A ₁ , A ₂ From the beacon frame. Next, the frequency F ₂ Search for the beacon frame of the wireless terminal station ST ₁ Is the wireless base station A ₃ From the beacon frame. Next, the frequency F ₃ Search for the beacon frame of the wireless terminal station ST ₁ Does not detect beacon frames.
[0064]
Then, the MAC address included in these beacon frames is extracted by the medium access control circuit 8 and notified to the terminal station control unit 11. Then, the terminal station control unit 11 records the MAC address in association with the detected frequency of the beacon frame.
[0065]
And the wireless terminal station ST ₁ Is at least one radio base station A _N Used by the radio base station A _N And the one of the radio base stations A using the frequency _N Select Here, the frequency F is selected. ₂ And wireless base station A ₃ It is.
[0066]
Note that the wireless base station A _N Radio base station A using the frequency with the smallest number of _N If there are a plurality of _M Is the radio base station A having the best reception quality among them. _N You just have to select Also, the radio base station A _N If there are a plurality of frequencies having the smallest number of _M May be selected as the frequency with the lowest line usage rate.
[0067]
Next, the wireless terminal station ST ₁ Sets the frequency of the wireless transmitting / receiving circuit 7 to the frequency F ₂ Switch to the wireless base station A ₃ Make a request for authentication and a request for membership. Wireless terminal station ST ₁ Is successfully performed, and the wireless base station A ₃ Is the wireless terminal station ST ₁ , The wireless terminal station ST ₁ Is the frequency F ₂ Using the radio base station A ₃ And start transmitting and receiving data.
[0068]
Radio base station A used _N Are the radio terminal stations ST that can be accommodated therein. _M It is considered that the degree of congestion is high because the number of However, as described above, according to the present embodiment, the wireless terminal station ST _M When newly joining one of the basic service units, at least one radio base station A _N Used and used by the radio base station A _N Is selected and the data communication is started using the radio base station using that frequency. Therefore, the wireless terminal station ST _M Is the radio base station A _N And the frequency of low congestion can be selected in a short time.
[0069]
Further, according to the present embodiment, the radio base station A _N The beacon frame transmitted from the wireless base station A includes only information elements included in a frame format conforming to IEEE 802.11 and does not include special information for the present embodiment. _N Can be used as it is, and development is easy.
[0070]
In this embodiment, the wireless terminal station ST _M Is at least one radio base station A _N Used by the radio base station A _N By selecting the frequency with the smallest number of _M Is used, but the present invention is not limited to this. The present invention relates to a wireless terminal station ST using each frequency. _M Any frequency may be used as long as it determines which frequency is to be selected. For example, the radio base station A having a low congestion degree and the same frequency _N Radio terminal station ST so that handover between _M Is at least two radio base stations A _N Used by the radio base station A _N May be selected.
[0071]
Further, in the present embodiment, the wireless LAN system has been described as an example of the wireless communication system in which the wireless terminal station performs communication via any one of the wireless base stations using different frequencies. The present invention is applicable to a wireless communication system having a similar configuration.
[0072]
In this embodiment, the wireless terminal station ST _M Is a new basic service unit BSS _N Radio base station A used when participating in _N Radio base station A using the selected frequency _N Basic service unit BSS _N Has been described as an example, but the present invention is not limited thereto.
[0073]
As another example, a radio base station A that is to open a new basic service unit _N When automatically determining the optimum frequency to be used by itself from the surrounding conditions, the radio base station A _N And select a frequency with few basic services, and use that frequency to provide the basic service unit BSS. _N May be established. However, the radio base station A _N In the establishment of the radio base station A _N Wireless terminal station ST in that it is possible to select a frequency where there is no _M Is different from the example.
[0074]
In that case, the radio base station A in FIG. _N First, the base station control unit 5 controls the medium access control circuit 2 to detect a beacon frame while controlling the frequency switching control circuit 6 to switch the frequency used in the wireless transmission / reception circuit 1, and is included in the beacon frame. Radio base station A using each frequency from the MAC address _N Recognize. Next, the radio base station A used _N Is selected and the frequency switching control circuit 6 is controlled to switch the frequency of the wireless transmission / reception circuit 1 to that frequency. Then, a basic service unit is established using the frequency.
[0075]
As a result, the radio base station A that newly establishes a basic service unit _N Can open a basic service unit by selecting a frequency with low congestion, and can distribute traffic to each frequency.
[0076]
【The invention's effect】
According to the present invention, when selecting a frequency to be used for communication with the radio base station, the radio terminal station selects a frequency based on the number of radio base stations using each frequency. It is possible to grasp the frequency status, select an appropriate frequency, and start communication.
[0077]
Also, the radio terminal station selects a frequency used by at least one radio base station and uses the least number of radio base stations and starts communication using that frequency. And the frequency of low congestion can be selected in a short time.
[0078]
Further, according to the present invention, when selecting a frequency to be used by itself when newly establishing a radio base station, the radio base station selects a frequency based on the number of existing radio base stations using each frequency. It is possible to grasp the status of each frequency and select an appropriate frequency to start communication.
[0079]
Also, the radio base station selects the frequency with the least number of existing radio base stations in use and starts communication using that frequency, so the number of radio base stations is small, interference is small, A frequency with low congestion can be selected in a short time.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a wireless LAN system according to an embodiment.
FIG. 2 is a block diagram showing a configuration of a wireless base station shown in FIG.
FIG. 3 is a diagram showing a frame format of a beacon signal transmitted from the wireless base station shown in FIG.
FIG. 4 is a block diagram showing a configuration of a wireless terminal station shown in FIG.
FIG. 5 is a sequence diagram showing an operation of the wireless LAN system when a wireless terminal station selects a frequency used for data transmission / reception.
[Explanation of symbols]
1 Wireless transceiver circuit
2 Medium access control circuit
3 Transmit / receive data buffer
4 Wired interface circuit
5 Base station controller
6. Frequency switching control circuit
7 Wireless transceiver circuit
8 Medium access control circuit
9 Transmission / reception data buffer
10 Internal interface circuit
11 Terminal station control unit
12. Frequency switching control circuit
101 preamble
102 Medium access control header
103 BSS control information
104 FCS (Frame Check Sequence)
105 Frame identifier
106 Destination address
107 BSSID
108 Access control information
A _N Wireless base station
BSS _N Basic service unit
NW _L Wired network
ST _M Wireless terminal station

Claims (12)

A plurality of wireless base stations transmit base station identification signals including their own identification information using a frequency determined for each, and a plurality of wireless terminal stations identify each wireless base station by the base station identification signals. A radio frequency selection method for a radio terminal station to select any frequency in a radio communication system for identifying and selecting any one of the frequencies and connecting to and communicating with a radio base station using the frequency And
A first step of searching for the base station identification signal while sequentially switching a plurality of frequencies assigned to the wireless communication system;
A second step of extracting the identification information from the base station identification signal detected by the search and recording the identification information in association with the detected frequency of the base station identification signal;
A third step of determining the number of radio base stations using each of the frequencies from the identification information recorded in association with each of the frequencies,
And a fourth step of selecting a frequency based on the number of radio base stations using the respective frequencies. 2. The radio frequency selection method according to claim 1, wherein in the fourth step, a frequency used by at least one radio base station and in which the number of radio base stations used is the smallest is selected. The existing wireless base station transmits a base station identification signal including its own identification information using a frequency determined for each of the base stations, and the new wireless base station uses each base station identification signal to transmit the base station identification signal. In a wireless communication system in which a station is identified and any one of the frequencies is selected and the frequency is used for communication with a wireless terminal station, a new wireless base station uses a radio frequency selection method for selecting any one of the frequencies. So,
A first step of searching for the base station identification signal while sequentially switching a plurality of frequencies assigned to the wireless communication system;
A second step of extracting the identification information from the base station identification signal detected by the search and recording the identification information in association with the detected frequency of the base station identification signal;
A third step of determining the number of radio base stations using each of the frequencies from the identification information recorded in association with each of the frequencies,
And a fourth step of selecting a frequency based on the number of radio base stations using the respective frequencies. The radio frequency selection method according to claim 3, wherein in the fourth step, a frequency that uses the least number of radio base stations is selected. The base station transmits a base station identification signal including its own identification information using a frequency determined for each of a plurality of frequencies assigned to the wireless communication system, and connects to a wireless terminal station using the frequency. And a plurality of wireless base stations for communication,
Searching for the base station identification signal while sequentially switching the plurality of frequencies, extracting the identification information from the base station identification signal detected by the search, identifying the wireless base station from the identification information, A wireless communication system having at least one wireless terminal station that selects a frequency based on the number of wireless base stations using the wireless communication system. 6. The wireless communication system according to claim 5, wherein the wireless terminal station selects a frequency used by at least one wireless base station and having the least number of wireless base stations used therein. A wireless communication system assigned a plurality of frequencies used for communication by wireless signals,
At the time of new establishment, while sequentially switching the plurality of frequencies, a search for a base station identification signal including identification information of a wireless base station is performed, and the identification information is extracted from the base station identification signal detected by the search, and the identification information is extracted. To identify a radio base station, select a frequency used by itself based on the number of existing radio base stations using each of the frequencies, and use the frequencies to generate a base station identification signal including identification information of each of them. A plurality of radio base stations to transmit,
A wireless terminal having at least one wireless terminal station that identifies each wireless base station based on identification information extracted from the base station identification signals transmitted from the plurality of wireless base stations and communicates with any one of the wireless base stations; Communications system. The wireless communication system according to claim 7, wherein the wireless base station selects a frequency that uses the least number of wireless base stations. At least one wireless base station transmits a base station identification signal including its own identification information using a frequency determined for each of the wireless base stations, and a plurality of wireless terminal stations transmit each base station identification signal using the base station identification signal. In the wireless communication system that performs communication by connecting to and communicating with a wireless base station using the frequency, a wireless terminal station that selects any frequency,
A wireless transmitting and receiving circuit capable of transmitting and receiving a wireless signal by switching a plurality of frequencies assigned to the wireless communication system,
A frequency switching control circuit that controls switching of the frequency of the wireless transmitting and receiving circuit,
Instruct the frequency switching control circuit to sequentially switch the plurality of frequencies, perform a search for the base station identification signal at each frequency, the identification information extracted from the base station identification signal detected by the search, The base station identification signal is recorded in association with the detected frequency, and the frequency is determined based on the identification information recorded in association with each of the frequencies, based on the number of radio base stations using each of the frequencies. Wireless terminal station apparatus having a control unit for selecting a wireless terminal. 9. The wireless terminal station device according to claim 8, wherein the control unit selects a frequency used by at least one wireless base station and using the least number of wireless base stations among them. The existing wireless base station transmits a base station identification signal including its own identification information using a frequency determined for each of the base stations, and the new wireless base station uses each base station identification signal to transmit the base station identification signal. Identify the station, select any one of the frequencies, in a wireless communication system using the frequency for communication with the wireless terminal station, at the time of new installation, a wireless base station to select any frequency,
A wireless transmitting and receiving circuit capable of transmitting and receiving a wireless signal by switching a plurality of frequencies assigned to the wireless communication system,
A frequency switching control circuit that controls switching of the frequency of the wireless transmitting and receiving circuit,
At the time of new installation, the frequency switching control circuit is instructed to sequentially switch the plurality of frequencies, a search for the base station identification signal is performed at each frequency, and the identification extracted from the base station identification signal detected by the search is performed. The information is recorded in association with the detected frequency of the base station identification signal, obtained from the identification information recorded in association with each frequency, the number of radio base stations using each frequency A wireless base station device having a control unit for selecting a frequency based on the base station. The radio base station apparatus according to claim 11, wherein the control unit selects a frequency that uses the least number of radio base stations.

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