JP2004166104A - Wireless lan system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of communication in a wireless LAN system that uses a multifunctional access point provided with a plurality of access point modules. <P>SOLUTION: This multifunctional access point is provided with a station module for wireless connecting to a trunk LAN. The station module monitors the ambient radio wave environment when the multifunctional access point is started. As a result of this, the access point modules in the multifunctional access point operate by using a frequency channel with little interference. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless local area network (wireless LAN) system including a plurality of mobile terminals that communicate using a wireless transmission path, and an access point serving as a base station for controlling connection of the mobile terminals. More particularly, the present invention relates to a wireless LAN system using a multifunctional access point having a plurality of access point modules in a single housing.
[0002]
[Prior art]
Conventionally, a wireless LAN system has been used as a highly portable network system that is not restricted by a communication cable. In recent years, in particular, an improvement in transmission speed in a wireless communication section, spread of a notebook computer, and applications suitable for mobile communication have been made. With the emergence of, etc., it is showing a dramatic spread. Particularly, as a wireless LAN system using radio waves in the 2.4 GHz and 5 GHz bands, a wireless LAN system defined by the IEEE 802.11 standard group has been widely used.
[0003]
Advantages of such a wireless LAN system include not only a feature that a cable connection is unnecessary and a free layout of equipment in a living room is possible, but also considering a portability as a mobile terminal, the wireless LAN system may be close to a connection point. For example, it is a very convenient system that can be freely connected to the in-house main LAN even in different places such as a living room and a meeting room in a company, and can perform the same work as one's desk at any place. Further, in recent years, it has become possible to connect to the Internet from a connection point outdoors by a connection service provider, commonly called a hot spot, using a terminal owned by the user.
[0004]
FIG. 6 shows a system configuration diagram of a general wireless LAN system. The wireless LAN system includes a plurality of mobile terminals called stations 101 and a base station called an access point 102. In the wireless LAN system, all stations share and use a single wireless channel allocated to the cell. Therefore, in order to avoid packet collision, the packet transmission timing of each station is set according to the Media Access Control (MAC) protocol. Controlled. In a wireless LAN system, a method called CSMA / CA is used as a MAC protocol. In this CSMA / CA method, each station performs carrier sense on a wireless medium for a predetermined period before transmitting a packet, and After confirming that is not occupied, the packet transmission is started.
[0005]
Also, depending on the location where each terminal is located, each station may not be able to receive signals transmitted by all stations with each other. In order to avoid packet collision due to a so-called hidden terminal problem, each station is used in a wireless LAN. Some MAC protocols use a distribution coordination function (DCF) using RTS / CTS frames based on CSMA / CA, and a point coordination function (PCF) that performs control by polling from an access point. By doing so, a multiple access function is realized.
[0006]
Such a form of the wireless LAN operated under the control of the access point is called an infrastructure mode, and managing the operation mode is the first role of the access point.
[0007]
Another role of the access point is to bridge data packets between a wireless section and a wired LAN that is generally connected to a main LAN. In the figure, the access point 102 has a wired LAN interface, and is thereby connected to the wired LAN 103.
[0008]
At this time, the access point must have at least a function as a wired-to-wireless bridge capable of absorbing the difference between the wireless LAN protocol and the wired LAN protocol, and additionally have other network functions such as packet routing and a DHCP server. It is also possible to implement.
[0009]
The operation of an access point is indispensable for operating a wireless LAN system in this way, but the number of mobile terminals that can be accommodated per access point is limited, especially in an environment with a large number of mobile terminals. In some cases, a plurality of access points are installed at the same point in order to increase the total number of mobile terminals accommodated.
[0010]
In recent years, not only 2.4 GHz band systems but also 5 GHz band radio waves have been used as wireless LANs. In response to demands such as bridging between modulation and demodulation systems such as a Bluetooth system and a system having different access protocols such as a Bluetooth system, a multifunctional access point having a plurality of access point modules in a single housing has been devised.
[0011]
FIG. 7 is a diagram showing a configuration of a conventional wireless LAN system using multifunctional access points. In the figure, it is assumed that a multi-function access point 104 supports three systems of a 2.4 GHz band wireless LAN, a 5 GHz band wireless LAN, and Bluetooth. Now, a group of wireless LAN mobile terminals 105 in the 2.4 GHz band form the first cell 201 according to the frequency band in the 2.4 GHz band and the access protocol of IEEE 802.11.
[0012]
Further, the 5 GHz band wireless LAN mobile terminals 106 form a second cell 202 according to the 5 GHz band frequency band and the IEEE 802.11 access protocol, and the Bluetooth mobile terminals 107 form a third cell 203 similarly. ing. These mobile terminals perform wireless communication with each other in each cell, and at the same time, data transfer between cells is performed by the multi-function access point 104. Furthermore, since the multi-function access point is connected to the wired LAN 103, it is possible to exchange data packets communicated in the cells 201, 202, and 203 in the wireless section with the wired backbone LAN.
[0013]
FIG. 8 is a diagram showing an example of the internal configuration of the multifunction access point shown in the conventional example. The multi-function access point 501 incorporates a plurality of access point modules in a single housing, that is, a 2.4 GHz band wireless LAN access point module 11, a 5 GHz band wireless LAN access point module 12, and a Bluetooth access point module 13. These are connected to the system bus 10. Further, the multi-function access point 104 is provided with a wired LAN transceiver 17 together with a microprocessor 14 for controlling, a RAM 15 as a work memory, a ROM 16 as a program storage memory, and the like, and is connected to a wired LAN network 18. ing. In this conventional example, the multi-function access point 104 is connected to the main LAN by the wired LAN transceiver 17, but a configuration in which this portion is replaced with wireless communication is also conceivable.
[0014]
FIG. 9 is a configuration diagram of a wireless LAN system using a multi-function access point in a form of wirelessly connecting to the main LAN, and FIG. 10 shows an internal configuration example of the multi-function access point. In FIG. 10, the multi-function access point includes a 2.4 GHz band wireless LAN station module 21, and the access point module includes two 2.4 GHz band wireless LAN access points 11 and a Bluetooth access point 13. ing.
[0015]
The multifunctional access point wirelessly communicates with the access point 102 connected to the main LAN as shown in FIG. At this time, the station module 21 mounted on the multi-function access point 501 operates as a station for the access point 102.
[0016]
In view of such an operation state, in this wireless LAN system in FIG. 9, the cell 201-b generated by the access point 102 connected to the main LAN and the access point modules # 1 and # 2 in the multifunction access point are provided. There are three wireless LAN cells in total, including the cell 201-a generated by.
[0017]
When a plurality of wireless LAN cells exist in the same geographical area, a problem of mutual radio wave interference occurs. Furthermore, since there are Bluetooth terminals using the same 2.4 GHz band radio wave in this system, mutual communication may collide unless proper access control on the time axis or appropriate frequency channel assignment is performed. This may result in a significant decrease in communication efficiency.
[0018]
Japanese Patent Application Laid-Open No. 2000-358059 is known as a conventional technique for avoiding a failure caused by a plurality of access points operating in the same area.
[0019]
In this conventional example, a plurality of installed access points form a synchronization frame on the condition that no synchronization frame has arrived from another access point after a delay time set by the probability of uniform distribution independent of each other. A transmitting means is employed to prevent collision of synchronization frames between access points, and to provide a method in which a plurality of access points coexist.
[0020]
However, in this conventional example, although a plurality of access points can coexist, the plurality of access points use the same frequency channel in a time-division manner, and further control access to the channel based on probability. Therefore, the usage efficiency is significantly reduced as compared to a situation where only a single access point is operated.
[0021]
Therefore, when multiple access points are installed in the same area, or in a system such as a multi-function access point in which multiple access points are provided in the same housing, each access point uses a different frequency channel. In this case, efficient communication can be performed by an appropriate method of selecting the frequency channel.
[0022]
Next, as a conventional example of a wireless LAN system using a plurality of frequency channels, there is JP-A-2001-11575. This conventional example is a technology as a wireless repeater, and has a configuration in which a data packet transmitted from an access point or a station is frequency-converted by an analog circuit and retransmitted on another frequency channel.
[0023]
The purpose is to expand the geographical area that one access point can control, but the same data packet will be transmitted on multiple frequency channels at the same time, resulting in reduced efficiency of frequency utilization. Since the analog signal is frequency-converted, the signal-to-noise ratio of the original signal is not improved.
[0024]
[Problems to be solved by the invention]
As described above, in a multi-function access point including a plurality of access point modules, when a frequency channel used by each access point module cannot be appropriately assigned from among a plurality of available frequency channels, the There is a problem that communication efficiency is reduced.
[0025]
In view of these circumstances, the present invention allows a built-in access point module to select an optimal frequency channel in a multi-function access point having a station module as a means for connecting to a main LAN, thereby improving communication efficiency compared to the related art. To provide a wireless LAN system with high security.
[0026]
[Means for Solving the Problems]
In order to achieve the above object, a feature of the multi-function access point used in the invention according to the present application is that, immediately after activation, a station module provided in the access point sequentially receives all of the frequency channels in the radio space. Means for storing the use state of each frequency channel detected as a result of this, and a step of transmitting an unused and low-interference frequency channel to an access point module provided in the multifunctional access point. It is in.
[0027]
These means and steps have an effect of effectively assigning a frequency to an access point module provided in the multi-function access point.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example)
The operation of the multi-function access point of the wireless LAN system according to the embodiment of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 is a diagram showing an internal configuration of a multi-function access point according to the present invention. In the present embodiment, the mobile terminal is accommodated by two access point modules of the 5 GHz band wireless LAN, and the main LAN is connected by the same 5 GHz band wireless LAN station module. In the figure, a multi-function access point 501 includes a first access point module 12-a, a second access point module 12-b, and a station module 21, which are connected to the microprocessor 13 by the system bus 10. It is connected.
[0030]
In this embodiment, the processor 13 holds as many flags as tables used in the 5 GHz band wireless LAN system. In this example, this flag is provided in a register in the processor. However, the flag may be implemented in a memory such as the RAM 14. The frequency channels that can be used in the wireless LAN are defined by standards and laws for each country and region. For example, in Japan, 5.17 GHz, 5.19 GHz, 5.21 GHz, and 5.10 GHz as shown in FIG. Four channels of 23 GHz are available. Here, in this example, the number of frequency channels is set to four. However, there may be cases where more frequency channels can be used in other countries and regions. In this case, the present invention can be applied similarly. Now, as shown in FIG. 2, these four frequency channels are referred to as ch1, ch2, ch3, and ch4, respectively.
[0031]
FIG. 3 is a flowchart illustrating an initial operation of the multi-function access point according to the present invention. First, when the multi-function access point is started, it clears all the contents of the held flags after various initializations. Then, the multi-function access point attempts to receive a beacon frame from another access point considered to be present in the vicinity by using the provided station module.
[0032]
At this time, scanning is sequentially performed on all the frequency channels from ch1 to ch4. However, now, there are two other access points connected to the wired backbone LAN near the multi-function access point. It is assumed that the points constitute a cell using ch3 and ch4, and the access point using ch3 has the same SS-ID as the station module in the multifunctional access point. Suppose
[0033]
At this time, the multi-function access point sequentially scans from ch1, but since only the ch3 and ch4 receive signals from other access points connected to the main LAN, the flag is set only in this case.
[0034]
When the scanning of all the frequency channels is completed, the multi-function access point informs the beacon frame from the beacon frame that the access point constituting the cell using ch3 in the vicinity has the same ID as its own SS-ID. Since it can be recognized, the multifunctional access point makes a connection request to this access point using the station module provided. From here on, the multi-function access point establishes a data path to the backbone LAN via the other access point according to the normal connection / authentication procedure between the station and the access point specified in IEEE 802.11.
[0035]
Next, the multi-function access point shifts to activation of the plurality of access point modules provided. At this time, by referring to the flag table, ch3 and ch4 can recognize that another access point is already in use. Therefore, the frequency channels for which no flag is set, that is, the currently unused frequency channels are sequentially transmitted to the access point module. Notify and start each access point module.
[0036]
In this embodiment, the multi-function access point allocates ch1 to the first access point module 12-a and ch2 to the second access point module 12-b.
[0037]
According to the above procedure, the multi-function access point according to the present invention can operate the provided access point module using a channel other than the frequency channel already occupied at the time of start-up, so that the same frequency channel Can be avoided from being used by a plurality of access points or multi-function access points, and efficient communication can be realized.
[0038]
Also, in this embodiment, the station module of the multi-function access point performed a connection process to the main LAN because another access point having the same SS-ID was found, but there is an access point to be temporarily connected. Otherwise, the multi-function access point simply cannot obtain a connection path to the backbone LAN, and the optimal allocation method of the frequency channel of the present invention functions similarly.
[0039]
(Other embodiments)
In the first embodiment, the effects of the present invention in the wireless LAN system having the same frequency band, modulation / demodulation method, and access method of 5 GHz band wireless LAN have been described.
[0040]
However, for example, a system in which all frequency channels are not completely separated and overlap is allowed, such as a 2.4 GHz band wireless LAN, or an access method completely different from the wireless LAN. In the case where Bluetooth systems or the like coexist in the same frequency band, the multi-function access point according to the second aspect of the present invention is effective. Therefore, a wireless LAN system according to another embodiment of the present invention will be described with reference to the drawings.
[0041]
FIG. 4 is a diagram showing another example of the internal configuration of the multi-function access point according to the present invention. In the present embodiment, the mobile terminal is accommodated by two 2.4 GHz band wireless LAN access point modules, and connected to the main LAN by the same 2.4 GHz band wireless LAN station module. In the figure, a multi-function access point 501 includes a first access point module 11-a, a second access point module 11-b, and a 2.4 GHz band wireless LAN station module 21. 10 is connected to the microprocessor 13.
[0042]
In this embodiment, the processor 13 holds as many tables of interference level fields as used in the 2.4 GHz band wireless LAN system. In this example, this field is provided in a register in the processor. However, the field may be implemented in a memory such as the RAM 14, for example.
[0043]
FIG. 5 is a flowchart illustrating an initial operation of the multi-function access point according to the present invention. First, when the multi-function access point 501 is started up, it clears all the contents of the held interference level field after various initializations. Then, the multi-function access point 501 measures the interference level of each frequency channel using the receiving unit of the wireless LAN station module 21 provided. For example, assuming that 14 channels can be used as wireless LAN frequency channels, scanning is sequentially performed on all frequency channels from ch1 to ch14. Then, the measured interference level values are recorded in the interference level field.
[0044]
When the scanning of all the frequency channels is completed, the multi-function access point starts to activate a plurality of access point modules provided. At this time, the lowest frequency channel is selected from all the values in the interference level field, and the selected channel is notified to the access point module. This operation is repeated by the number of access point modules provided. In order to avoid re-assigning the already assigned channel, the multi-function access point 501 rewrites the interference level field corresponding to the assigned frequency channel to the maximum value each time.
In this embodiment, ch4 is assigned to the first access point module and ch11 is assigned to the second access point module among the frequency channels with low interference levels.
[0045]
According to the above procedure, the multi-function access point according to the present invention measures the external interference level of each frequency channel at the time of startup, and operates the access point module provided using the frequency channel with relatively small interference. Therefore, the number of data packet collisions / retransmissions can be reduced and efficient communication can be realized.
[0046]
【The invention's effect】
As described above with reference to the drawings, according to the invention of the present application, the multi-function access point monitors the frequency channel in the wireless space by the station module at the time of startup, thereby making the multifunction access point optimal for the built-in access point module. A frequency channel can be selected, and an effect of increasing communication efficiency in a wireless LAN system in which a plurality of access point modules operate is obtained. Further, the first claim according to the present invention is to receive a frame of a wireless LAN system as a means for channel selection, and the second claim is to measure an interference level. This method is also included in the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram showing the internal configuration of a multi-function access point according to a first embodiment of the present invention; FIG. 2 is a diagram showing a frequency channel of a 5 GHz band wireless LAN in Japan; FIG. FIG. 4 is an operation flow diagram of a multi-function access point in an embodiment. FIG. 4 is an internal configuration diagram of a multi-function access point in another embodiment of the present invention. FIG. 5 is an operation flow of a multi-function access point in another embodiment of the present invention. FIG. 6: System configuration of wireless LAN system FIG. 7: System configuration of wireless LAN system using multi-function access point FIG. 8: Internal configuration of conventional multi-function access point FIG. 9: Multi-function System configuration diagram of wireless LAN system using access point [FIG. 10] Internal configuration diagram of conventional multi-function access point [Description of symbols]
101 mobile terminal 102 access point 103 wired backbone LAN
104 multi-functional access point 105 2.4 GHz band wireless LAN mobile terminal 106 5 GHz band wireless LAN mobile terminal 107 Bluetooth terminal 201 5 GHz band wireless LAN cell 202 ... 2.4 GHz band wireless LAN cell 203 ... Bluetooth Cell 501 Multifunctional access point 10 System bus 11 2.4 GHz band wireless LAN access point module 12 5 GHz band wireless LAN access point module 13 Bluetooth access point module 14 Microprocessor 15 RAM
16 ... ROM
17 Wired LAN transceiver 18 Wired LAN
21 station module 14 microprocessor 15 RAM

Claims (2)

In a wireless LAN system for performing wireless communication using a plurality of radio frequency channels by a collision avoidance type carrier sense multiple access,
The wireless LAN system includes a plurality of terminal stations and a multi-function access point that transmit packets to each other,
The multi-function access point includes a plurality of access point modules for performing access control of the plurality of terminal stations and a station module for wirelessly connecting to a main LAN.
The multi-function access point exchanges data packets between the plurality of access point modules and station modules;
The multi-function access point has flags for the number of frequency channels available to the wireless LAN system,
The multi-function access point performs reception for each of the plurality of frequency channels by the station module at startup,
As a result of receiving the plurality of frequency channels, the multi-function access point sets a flag for the frequency channel when receiving a frame from another wireless LAN system,
The wireless LAN system, wherein the multi-function access point allocates a frequency channel with no flag among the frequency channel flags to the plurality of access point modules. In a wireless LAN system for performing wireless communication using a plurality of radio frequency channels by a collision avoidance type carrier sense multiple access,
The wireless LAN system includes a plurality of terminal stations and a multi-function access point that transmit packets to each other,
The multi-function access point includes a plurality of access point modules for performing access control of the plurality of terminal stations and a station module for wirelessly connecting to a main LAN.
The multi-function access point exchanges data packets between the plurality of access point modules and station modules;
The multi-function access point holds, as a memory, interference level data fields for the number of frequency channels available to the wireless LAN system,
The multi-function access point measures an interference level for each of the plurality of frequency channels by the station module at startup,
The multi-function access point stores a result of measuring the interference level of the plurality of frequency channels in the interference level data field,
The wireless LAN system, wherein the multi-function access point preferentially allocates a frequency channel having a small value of the interference level data field to the plurality of access point modules.

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