JP7478519B2 - Wireless relay device, wireless LAN system using the same, and wireless relay method - Google Patents

Description

The present invention relates to a wireless relay device and a wireless LAN system and wireless relay method using the same, and in particular to a wireless LAN system that is configured with the above-mentioned wireless relay device that serves as a wireless relay master device and in which multiple devices are operated together, one or more wireless relay slave devices that are wirelessly connected to the wireless relay master device, and preferably a large number of wired or wireless communication terminals that are connected to the wireless relay slave devices.

In order to avoid congestion and enable faster data transfer, the frequencies used by wireless LAN systems are expanding to the 5 GHz band in addition to the original 2.4 GHz band. However, the 5 GHz band has already been used for other purposes, such as weather radar.

For this reason, for example, in the IEEE 802.11a standard for wireless LAN, when using frequency bands (channels) called W53 or W56, a control called DFS (Dynamic Frequency Selection) is performed to prevent interference with other uses such as the weather radar. The DFS control avoids interference by switching channels when radio waves for the other uses are detected, and also performs a CAC (Channel Availability Check) to monitor the channel to which the channel has been switched for a specified period of time to determine whether radio waves for the other uses are being detected. Therefore, wireless LAN communication is not possible during this time. Furthermore, if radio waves for the other uses are detected again after CAC has been performed, the task of searching for another channel will be repeated, and communication will continue to be impossible during that time.

Patent Document 1 proposes a wireless LAN access point that is equipped with multiple wireless interfaces, each with a different SSID, and when a channel used by one wireless interface becomes unusable due to weather radar, another wireless interface uses a multi-SSID function that allows one wireless interface to handle multiple SSIDs to provide the SSID of the unusable wireless interface, thereby preventing sessions of subordinate communication terminals from being interrupted.

JP 2009-100210 A

However, in the above-mentioned conventional technology, even though the communication terminal connects to the same SSID, it is necessary to scan frequencies to search for that same SSID, which results in a problem that reconnection takes time.

The object of the present invention is to provide a wireless relay device, a wireless LAN system using the same, and a wireless relay method that, when a wireless relay slave is connected to a wireless relay master, enables communication with a communication terminal on the wireless relay slave side even if the channel currently being used by the wireless relay master becomes unavailable due to DFS or CAC, making wireless LAN communication impossible.

The wireless relay device of the present invention is a wireless relay device used as a wireless relay master in a wireless LAN system comprising a plurality of wireless relay masters operated together and configured to be able to communicate information with each other, and one or more wireless relay slaves wirelessly connected to each of the wireless relay masters, the wireless relay device including: a determination unit which determines a channel transition depending on radio wave conditions; a switching unit which, when the determination unit determines the channel transition, provides information of the other wireless relay devices operated together to the wireless relay slave connected to the wireless relay device, thereby switching the connection destination of the wireless relay slave; a completion transmitting unit which, when the channel transition is completed, transmits the completion of the transition to the other wireless relay devices operated together; and a completion receiving unit which, when notified of the completion of the channel transition, provides information of the original wireless relay device operated together from the switching unit only to the wireless relay slave devices connected to the wireless relay device, the connection destination of which has been switched by the switching unit of the original wireless relay device operated together, thereby switching the connection destination of the wireless relay slave device back to the original wireless relay device operated together.

Furthermore, the wireless relay method of the present invention is a wireless relay method in a wireless relay device used as a wireless relay master in a wireless LAN system comprising a plurality of wireless relay masters operated as a unit and configured to be able to communicate information with each other, and one or more wireless relay slaves wirelessly connected to each of the wireless relay masters, the wireless relay method including the steps of: determining a channel transition in accordance with radio wave conditions; a switching step, when the channel transition is determined in the determining step, providing information of the other wireless relay devices operated as a unit to the wireless relay slave connected to the wireless relay device itself, thereby switching the connection destination of the wireless relay slave device; a completion sending step, when the channel transition is completed, transmitting the completion of the transition to the other wireless relay devices operated as a unit; and a completion receiving step, when notified of the completion of the channel transition , causing the switching unit to provide information of the original wireless relay device operated as a unit only to the wireless relay slave devices connected to the wireless relay device itself, the wireless relay slave devices whose connection destination has been switched by the switching unit of the original wireless relay device operated as a unit connected to the wireless relay device itself, thereby switching the connection destination of the wireless relay slave device back to the original wireless relay device operated as a unit.

According to the above configuration, in a wireless LAN system comprising a wireless relay master, one or more wireless relay slaves wirelessly connected to the wireless relay master, and preferably a large number of communication terminals connected to the wireless relay slaves, a wireless relay device used as the wireless relay master and a wireless relay method thereof, for example, when using the frequency bands (channels) W53 and W56 in the IEEE802.11a standard for wireless LAN and performing DFS (Dynamic Frequency Selection) control to prevent interference with weather radar, when the wireless relay master tries to change channels depending on the radio wave conditions, the wireless relay slaves and the communication terminals under the wireless relay slaves cannot communicate during CAC (Channel Availability Check), which determines whether radio waves for other purposes are detected on that channel. Also, if radio waves for other purposes are detected again when CAC is performed, the task of searching for another channel will be repeated, and communication will be disabled during that time.

In this invention, therefore, multiple wireless relay master units are operated as one unit and are configured to be able to communicate information with each other, and are usually adjusted to select channels as far apart as possible from each other to avoid interference. Preferably, the wireless relay master units operated as one unit exchange information such as the traffic volume, radio wave strength, and communication error status of each communication terminal without a special controller, autonomously distributing the load and optimizing the communication state.

In the determination step, when the determination unit determines that a channel should be changed based on the radio wave conditions, the wireless relay slave unit normally searches for a wireless relay master unit that will become a master station by scanning. In the present invention, however, in the switching step, the switching unit provides the wireless relay slave unit with information about the other wireless relay master units that are operated in unison, i.e., introduces the wireless relay slave unit, and switches (roams) the wireless relay master unit to which the wireless relay slave unit is connected.

Therefore, even if the wireless relay master unit is unable to communicate with the wireless relay slave unit over the wireless LAN due to DFS or CAC, the wireless relay slave unit can connect to another wireless relay master unit without searching, allowing it and the numerous communication terminals under its control to connect to the network continuously (without interruption).

Furthermore, according to the above configuration, when the channel transfer of the original wireless relay master device is completed, in the completion transmitting step, the completion transmitting unit transmits the transfer completion to the other wireless relay master device, and when the completion receiving unit of the other wireless relay device receives the communication, in the completion receiving step, the switching unit provides the wireless relay slave device with information about the original wireless relay master device, and switches the wireless relay master device to which the wireless relay slave device is connected back to the original wireless relay master device.

Therefore, even if the connection destination is once shifted to another wireless relay base station, when the original wireless relay base station becomes available for relaying, the wireless relay slave station is prompted to connect to the original wireless relay base station, and a so-called switchback operation is performed, so that there is no problem of excessive traffic on the other wireless relay base station remaining.

The wireless relay device of the present invention is also characterized in that the wireless relay master and the wireless relay slave constitute an inter-building communication unit.

With the above configuration, the inter-building communication unit constitutes an in-house network, etc., so it is effective and desirable to prevent connection failures.

Furthermore, the wireless LAN system of the present invention is characterized in that the wireless relay device is used as the wireless relay master, and the wireless relay slave is equipped with a connection master determination control unit that switches the wireless relay master to which it is connected in accordance with information from the other wireless relay device.

The above configuration makes it possible to realize a system in a wireless LAN system that can transfer packets without interruption when the connection destination of a wireless relay slave device is changed due to channel switching of the wireless relay master device by DFS or CAC.

As described above, in the wireless relay device and wireless relay method of the present invention, when a channel is changed in response to radio wave conditions in a wireless relay device that serves as a wireless relay master, information about other wireless relay devices that are operated in unison is provided to the wireless relay slave device, allowing the wireless relay slave device to switch the connection destination without having to search.

This allows the wireless relay device itself and the communication terminals under it to be connected to the network continuously (without interruption).

1 is a block diagram showing a configuration of a wireless LAN system using a wireless relay master unit which is a wireless relay device according to an embodiment of the present invention; 10A and 10B are diagrams for explaining a switching operation of the wireless relay slave device by the wireless relay master device; 3 is a flow chart of FIG. 2. 10 is a flowchart for explaining a master unit switching operation of a wireless relay slave unit under DFS control of a wireless relay master unit, showing a conventional operation. 5 is a flowchart for explaining a master device switching operation of a wireless relay slave device under DFS control of the wireless relay master device, showing the operation of this embodiment.

Figure 1 is a block diagram of a wireless LAN system 10 according to an embodiment of the present invention. This wireless LAN system 10 is configured with wireless relay masters 1 and 2, which are wireless relay devices according to an embodiment of the present invention, and a wireless relay slave 3. This wireless LAN system 10 is preferably used, for example, for wireless communication between buildings to build an in-house LAN, etc.

The wireless relay master units 1 and 2 are configured to be able to communicate with each other via a wired LAN 6, and are connected from the wired LAN 6 to an external network 7. The wireless relay master unit 2 has a similar configuration to the wireless relay master unit 1, and they are installed so that their wireless communication areas overlap each other to form a redundant configuration, and are operated together, and three or more units may be installed in the same area.

Although omitted in FIG. 1 for simplicity, there are one or more wireless relay slaves 3 subordinate to the wireless relay masters 1 and 2, and the wireless relay slaves 3 are connected to a wired and wireless network 8 via one or more stages of switching hubs 5. A large number of communication terminals (not shown) are connected to the network 8. The wireless relay slave 3 may have the same configuration as the wireless relay masters 1 and 2, in which case it can be switched between acting as a master or slave depending on the settings.

Therefore, the communication terminal connected to the network 8 is connected to the network 7 from the switching hub 5 and the wireless relay slave 3 via the wireless relay master 1 or 2, and is capable of sending and receiving packets. The connection between the wireless relay slave 3 and the wireless relay masters 1 and 2 is by a wireless LAN such as the IEEE802.11 standard. The connection between the network 8 and the communication terminal may also be by a wireless LAN such as the IEEE802.11 standard, or a wired LAN.

The wireless relay master 1 will be described below, and the wireless relay master 2 is configured in the same way. In the wireless relay master 1, data is transferred between the wired LAN communication unit 11 on the wired LAN 6 side and the wireless communication unit 12 on the wireless relay slave 3 side, enabling bidirectional transmission and reception of packets between the wired LAN 6 and the wireless relay slave 3. The wireless relay masters 1 and 2 are operated in pairs, and the pair master communication units 13 are configured to be able to communicate information to each other from the wired LAN communication unit 11 via the wired LAN 6. As a result, the pair of wireless relay masters 1 and 2 are adjusted to select channels as far apart as possible from each other without a special controller, usually to avoid interference, and can exchange traffic volume, radio wave strength, communication error status, etc. of each communication terminal, autonomously distribute the load, and optimize the communication state.

The 2.45 GHz band and the 5 GHz band may be used for communication by the wireless communication unit 12, and the radio wave conditions of the wireless communication unit 12 are monitored by the radar detection unit 15. When the radar detection unit 15 detects weather radar waves while using the frequency bands (channels) W53 and W56 in the IEEE802.11a standard, the parent unit channel determination control unit 16 performs a channel transition to achieve DFS control to prevent interference.

When making this transition, CAC must be performed for a predetermined period of time, for example one minute, to determine whether weather radar waves are detected on the new channel. If radar waves are detected again during CAC, the radar detection unit 15 and the parent channel determination control unit 16 will repeat the process of searching for yet another channel. As a result, the wireless relay slave unit 3 itself and its subordinate communication terminals will be unable to communicate during that time.

It should be noted that the wireless relay master 1 of this embodiment is provided with a slave switching destination channel notification transmission unit 17 that constitutes a switching unit together with the master channel determination control unit 16 in association with the wireless communication unit 12. When radar waves are detected in the judgment step of the radar detection unit 15, which serves as the judgment unit, the master channel determination control unit 16 reads out information (MAC address and channel used) of the other wireless relay master 2 pre-stored in the pair master communication unit 13 during the grace period, for example 10 seconds, until communication is stopped by DFS control in the switching step, provides it to the slave switching destination channel notification transmission unit 17, and transmits it from the wireless communication unit 12 to the wireless relay slave 3. In other words, the wireless relay slave 3 is introduced to the next destination to be connected to, and the connection destination is switched. This allows the wireless relay slave 3 and its subordinate communication terminals to be connected to the network 7 continuously (without interruption).

As described above, the wireless relay slave 3 can also be configured to become the wireless relay masters 1 and 2, so the basic configuration is similar, and includes a wired LAN communication unit 31 connected to the network 8 from the switching hub 5, a wireless communication unit 32 on the wireless relay masters 1 and 2 side, and a channel notification receiving unit 37 that receives the connection destination notification described above.

Normally, as described in detail below, the scan control unit 35 in the wireless communication unit 32 scans for beacon signals from wireless relay masters at a predetermined cycle, and depending on the results of the scan, the connection master determination control unit 36 determines the wireless relay master with the best radio wave conditions as the connection destination. On the other hand, as described above, when the channel notification receiving unit 37 receives information (MAC address and channel used) of a new wireless relay master 2 from the currently connected wireless relay master 1 via the wireless communication unit 32, the connection master determination control unit 36 switches the connection destination wireless relay master from reference number 1 to 2 in accordance with the information.

The state will be described using Fig. 2 and Fig. 3 in addition to Fig. 1. Fig. 2 is a diagram for explaining the switching operation of the wireless relay slave 3 by the wireless relay masters 1 and 2, and Fig. 3 is a flowchart thereof. The wireless relay masters 1 and 2 are operated in pairs, and the pair master communication unit 13 is configured to be able to communicate information with each other via the wired LAN 6. Therefore, when the pair of wireless relay masters 1 and 2 start communication (relay) in step S11 without a special controller, as shown in Fig. 2(a), they are usually adjusted to select channels as far away from each other as possible by the master channel determination control unit 16 to avoid interference, and they exchange the traffic volume, radio wave strength, communication error status, etc. of each communication terminal, autonomously distribute the load, and optimize the communication state. In FIG. 2(a), four wireless relay slaves 3A, 3B, 3C, and 3D are shown as wireless relay slaves 3 (hereinafter, when collectively referred to, they are indicated by the above-mentioned reference number 3). Wireless relay slaves 3A and 3B are subordinate to wireless relay master 1, and wireless relay slaves 3C and 3D are subordinate to wireless relay master 2.

Then, in step S12, as shown by reference character F1 in FIG. 2(b), when the radar detection unit 15 detects radar waves and the master channel determination control unit 16 determines channel transition, the subordinate wireless relay slave units 3A and 3B usually lose communication and search for the wireless relay master unit 2 that will become the master station by scanning. In contrast, in this embodiment, as shown by step S13, the slave switching destination channel notification transmission unit 17 causes the wireless communication unit 12 to transmit a beacon signal carrying information on the other paired wireless relay master unit 2, and the wireless communication unit 32 of the wireless relay slave units 3A and 3B introduces it to the channel notification reception unit 37. As a result, when the wireless relay slave units 3A and 3B receive it in step S21, they switch the wireless relay master unit to be used from reference character 1 to reference character 2 in step S22 as shown by reference character F2.

Then, in step S14, in the original wireless relay master 1, the master channel determination control unit 16 performs a channel transition (DFS), and in step S15, the radar detection unit 15 finishes determining an available channel (CAC), and when the master channel determination control unit 16 completes the channel transition, in step S16, the pair master communication unit 13, which serves as the completion transmission unit, transmits the completion of the transition to the other paired wireless relay master 2 from the wired LAN communication unit 11 via the wired LAN 6, as shown by reference symbol F3.

When the other wireless relay master 2 receives this communication from the wired LAN 6 via the wired LAN communication unit 11 to the pair master communication unit 13, which serves as the completion receiving unit, in step S31, the master channel determination control unit 16 provides information about the original paired wireless relay master 1 to each of the previously switched wireless relay slaves 3A and 3B via the wireless communication unit 12, and in step S23, as shown by reference symbol F4, switches the connection destination used by those wireless relay slaves 3A and 3B back to the original wireless relay master 1, returning to the state shown in FIG. 2(a).

In this way, many communication terminals under each of the wireless relay slaves 3A, 3B, 3C, and 3D can be connected to the external network 7 continuously (without interruption). Even if the connection destination is once shifted to another wireless relay master (2 in the above example), once the original wireless relay master (1 in the above example) becomes capable of relaying, the wireless relay slaves (3A and 3B in the above example) are prompted to connect to the original wireless relay master (1 in the above example) and a so-called switchback operation is performed, so that the traffic of the other wireless relay master (2 in the above example) does not remain excessive as shown in FIG. 2(b).

Now, referring to Figures 4 and 5, the host switching operation of the wireless relay slave 3 by the DFS control of the wireless relay masters 1 and 2 in Figure 2 will be compared. In the conventional switching operation shown in Figure 4, when the wireless relay master 1 connected to the wireless relay slave 3 changes channels due to radar detection and the connection to the external network 7 is cut off, in step S51, the wireless relay slave 3 starts scanning for beacon signals from other wireless relay masters, in step S52 changes channels, and in step S53, when it receives a beacon signal on that channel, in step S54, it transmits a probe request requesting connection. In step S55, it receives a probe response in response to that from the other wireless relay master, and in step S56, it determines whether scanning has been completed for all channels other than the channel of the original wireless relay master 1, and if not, it returns to step S52 and continues scanning.

If scanning of all channels is completed in step S56, the process proceeds to step S57, where the wireless relay master unit with the best conditions, such as radio wave strength and traffic, is selected from among the channels on which the probe response was received, and in step S58, a connection is made to that wireless relay master unit. If a beacon signal is not received in step S53, a determination is made in step S59 as to whether or not a predetermined time has passed since the channel change in step S52, and if so, the process returns to step S53 to continue reception, and if a timeout has occurred, a determination is made as to whether scanning of all channels is completed in step S56.

On the other hand, in the switching operation of this embodiment shown in Figure 5, before the wireless relay master 1 changes channels by DFS control, in step S61 the wireless relay slave 3 receives information about the destination wireless relay master 2, and in step S62 moves the channel according to that information. In steps S63 and S69, similar to steps S53 and S59, it waits until it receives a beacon signal on that channel, and when it does, in step S64 it starts connecting to that wireless relay master 2. In contrast, if a timeout occurs in step S59, it is determined that the connection to that wireless relay master 2 has failed, and the normal connection procedure of steps S51 to S59 in Figure 4 is performed.

Comparing Figures 4 and 5, the conventional switching operation requires scanning beacon signals on all channels other than the channel used by the wireless relay master unit 1 where communication is interrupted, whereas the switching operation of this embodiment requires receiving beacon signals only on the channel from which information was received, making it possible to greatly reduce the time during which communication is interrupted.

In this way, the wireless LAN system 10 of this embodiment uses the wireless relay masters 1 and 2 as described above as wireless relay devices, and can seamlessly transfer packets to a communication terminal when the connection destination of the wireless relay slave 3 is changed due to channel switching of the wireless relay masters 1 and 2 by DFS or the like. In other words, the wireless LAN system 10 described above uses the wireless relay masters 1 and 2 operated as a pair as the connection destination of the wireless relay slave 3, and can realize a redundant configuration in which, for example, one is used normally and the other is used in an emergency. In cases such as when increasing redundancy, three or more wireless relay masters may be operated together.

Alternatively, the wireless relay master units 1 and 2 may be operated in pairs to distribute the load (communication terminals) at all times. This makes it possible to realize a system that can handle an increase in the load (communication terminals) while still allowing communication to continue uninterrupted in an emergency.

In addition, the wireless relay devices 1 and 2 may be wireless relay devices installed indoors, such as wireless LAN access points, or may be wireless relay devices installed outdoors to enable communication between buildings, particularly when two devices are operated as a pair as described above.

Although the present invention has been described based on the embodiments, the present invention is not limited to these embodiments and can be implemented in various forms without departing from the spirit of the present invention. For example, in the embodiments, the wireless relay devices are wireless relay masters 1 and 2, and a wireless relay slave 3, which is a wireless relay device, is connected to a communication terminal in a multi-stage configuration, but the communication terminal may be wirelessly connected directly to the wireless relay device. In that case, during DFS control, the wireless relay device provides the communication terminal with information about other wireless relay devices, and the communication terminal that receives this performs an operation to switch the connection, as with the wireless relay slave 3 described above.

1, 2 Wireless relay base station (wireless relay device)
10 Wireless LAN system 11 Wired LAN communication unit 12 Wireless communication unit 13 Pair parent communication unit 15 Radar detection unit 16 Parent channel determination control unit 17 Child switching channel notification transmission unit 3 Wireless relay child 31 Wired LAN communication unit 32 Wireless communication unit 35 Scan control unit 36 Connection parent determination control unit 37 Channel notification reception unit 5 Switching hub 6 Wired LAN
7 External network 8 Network

Claims (4)

A wireless LAN system including a plurality of wireless relay master units that are operated together and capable of communicating information with each other, and one or more wireless relay slave units that are wirelessly connected to each of the wireless relay master units, comprising: a wireless relay device that is used as the wireless relay master unit;
A determination unit that determines a channel change according to radio wave conditions;
a switching unit that, when the determining unit determines that the channel has been changed, provides information on the other wireless relay device that is operated in unison with the wireless relay device to the wireless relay slave unit connected to the switching unit, thereby switching a connection destination of the wireless relay slave unit;
a completion transmission unit that transmits the completion of the channel transition to the other wireless relay device that is operated integrally when the channel transition is completed;
and a completion receiving unit which, upon receiving notification of the completion of the channel transfer, causes the switching unit to provide information about the original wireless relay device connected to the wireless relay device itself only to those wireless relay devices whose connection destination has been switched by the switching unit of the original wireless relay device connected to the wireless relay device itself, thereby switching the connection destination of the wireless relay device back to the original wireless relay device connected to the wireless relay device. The wireless relay device according to claim 1, characterized in that the wireless relay master and the wireless relay slave constitute an inter-building communication unit. A wireless LAN system using the wireless relay device according to claim 1 as the wireless relay master, and the wireless relay slave having a connection master determination control unit that switches the wireless relay master to which it is connected in accordance with information on the other wireless relay devices. A wireless LAN system including a plurality of wireless relay master units that are operated together and capable of communicating information with each other, and one or more wireless relay slave units that are wirelessly connected to each of the wireless relay master units, comprising: a wireless relay method in a wireless relay device used as the wireless relay master unit, the wireless relay method comprising:
A determination step for determining a channel change according to radio wave conditions;
When the channel transition is determined in the determining step, information of the other wireless relay device operated integrally is
a switching step of providing the signal to the wireless relay slave device connected to the wireless relay slave device to switch the connection destination of the wireless relay slave device;
a completion transmission step of transmitting the completion of the channel transition to the other wireless relay devices operated integrally when the channel transition is completed;
a completion receiving step of, upon receiving notification of the completion of the channel transfer, causing the switching unit to provide information of the original wireless relay device that is operated integrally to only those of the wireless relay slave devices connected to the wireless relay slave device itself that have had their connection destination switched by the switching unit of the original wireless relay device that is operated integrally, thereby switching the connection destination of the wireless relay slave device back to the original wireless relay device that is operated integrally.

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