JP5351321B2 - Wireless device, wireless communication system, control method, and control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio device that can realize a DFS function taking the prevention of interference with radar into consideration in an ad-hoc mode in a multi-hop environment. <P>SOLUTION: A radio device having a DFS function carrying out the prevention of interference with radar controls, in the case it has received a beacon frame, such that it will change the quiet count of the radio device to the quite count included in the beacon if the value of the quiet count included in the beacon is smaller than the value of the quiet count of the radio device, and it will ignore the beacon frame if the value of the quiet count included in the beacon is larger than the value of the quiet count of the radio device. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a radio apparatus, a radio communication system, a control method, and a control program, and in particular, a radio apparatus, a radio communication system, a control method, and a control program that implement a DFS (Dynamic Frequency Selection) function in an Ad-Hoc mode in a multi-hop environment. It is about.

  IEEE802.11h exists in the wireless LAN standard standardized by IEEE802.11. This IEEE802.11h has two functions of TPC (Transmit Power Control) for transmission output regulation and DFS (Dynamic Frequency Selection) for spectrum regulation.

  The TPC function requires the wireless LAN system to implement a transmission output control function for reducing the influence of interference on satellite systems that use the same frequency band.

  In addition, the DFS function obligates the wireless LAN system side to implement a radar detection function and a channel movement function for avoiding operation on the same channel as a radar system that uses the same frequency band as the wireless LAN standard.

  For example, the DFS function defined in IEEE802.11h obligates the wireless LAN system to have a radar detection function so that the wireless LAN system does not operate in the same frequency band as the radar system. In addition, when a radar is detected at the start of wireless LAN system operation and during operation, it is obliged to shift to another channel.

  As described above, although the DFS function specified by IEEE802.11h is obliged to the wireless LAN system, the DFS function specified by IEEE802.11h is realized in the Ad-Hoc mode in a multi-hop environment. The current situation is that nothing has been done. For this reason, it is necessary to develop a system for realizing a DFS function that considers avoidance of interference with radar in Ad-Hoc mode in a multi-hop environment.

  In addition, as a technical document filed prior to the present invention, radar detection is realized in a state where there are few unnecessary waves, not only in its own BSS (Basic Service Set) but also in a non-communication section in which interference waves from adjacent BSS do not occur. There is a document that discloses a technique that enables the above (see, for example, Patent Document 1).

  In addition, even when an interference source such as a radar is used in the same communication band, a technique for performing high-speed wireless communication using a wide frequency band in which a plurality of channels are bundled together with the radar is disclosed. There are documents (see, for example, Patent Document 2).

  In addition, there is a document that discloses a technique for incorporating dynamic frequency selection into a basic service set (BSS) and an independent basic service set (IBSS) of an IEEE 802.11 wireless network (see, for example, Patent Document 3).

  In addition, there is a document that discloses a technique for performing multi-hop using a protocol whose metric is to improve frequency utilization efficiency in a communication environment in which each communication station performs communication operation in an autonomous and distributed manner (for example, Patent Document 4). reference).

  In addition, there is a document that discloses a technology in which all terminals simultaneously shift frequency channels in an ad hoc and multi-hop wireless network (see, for example, Patent Document 5).

  In addition, there are documents that disclose active scan and passive scan methods, and spectrum and spectrum mask technologies (see, for example, Non-Patent Document 1).

JP 2006-303695 A JP 2007-5897 A Special table 2004-534480 gazette JP 2006-33289 A JP 2005-16162 A

ISO / IEC 8802-11 IEEE Std 802.11 Second edition 2005-08-01 ISO / IEC 8802 11: 2005 (E) IEEE Std 802.11i-2003 Edition, Information technology- Telecommunications and information exchange between systems-Local and metropolitan area networks- Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications (Includes IEEE Std 802.11, 1999 Edition; IEEE Std 802.11a.-1999; IEEE Std 802.11b.-1999; IEEE Std 802.11b. -1999 / Cor 1-2001; and IEEE Std 802.11d.-2001)

  Note that Patent Document 1 describes that synchronization between adjacent BSSs is realized with an arbitrary Beacon Interval set for each BSS. However, the above-mentioned patent document 1 aims at enabling radar detection in a state where there are few unnecessary waves by synchronizing the no-communication state, and does not realize the DFS function itself in consideration of avoiding interference with the radar. Absent.

  Further, Patent Document 2 describes a technique for coexisting with the radar even when an interference source such as a radar uses the same communication band. However, the above Patent Document 2 is an invention that focuses on the Infrastructure mode, and does not realize a DFS function in consideration of avoiding interference with the radar in the Ad-Hoc mode.

  Patent Document 3 discloses that channel switch information is transmitted using Beacon created autonomously and distributedly. When radar is detected, the channel must be switched within the specified time (Channel Move Time), and the number of Beacon that can be transmitted within the specified time is limited, so the Ad-Hoc mode is used. In a conventional multi-hop environment, only some nodes are channel-switched, and communication between nodes may be interrupted. For this reason, with the technique of the above-mentioned patent document 3, it may be assumed that the DFS function in consideration of avoiding interference with the radar cannot be realized in the Ad-Hoc mode.

  Moreover, the said patent document 4 is describing the point which performs multihop in the communication environment which performs communication operation | movement autonomously distributed. In addition, Patent Document 5 describes that when a plurality of frequency channels can be used, all terminals shift frequency channels all at once in order to shift to another frequency channel (DFS). . However, Patent Documents 4 and 5 do not suggest any DFS function in consideration of avoiding interference with the radar.

  The present invention has been made in view of the above circumstances, and a radio apparatus, a radio communication system, and a control capable of realizing a DFS function considering interference avoidance with a radar in an Ad-Hoc mode in a multi-hop environment It is an object to provide a method and a control program.

  In order to achieve this object, the present invention has the following features.

<Wireless device>
A wireless device according to the present invention includes:
A wireless device having a DFS function for avoiding interference with a radar,
When radar is detected, the transmission interval of the Beacon frame is shorter than the preset transmission interval, and is transmitted.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
When the CSA frame is received, the CSA frame including the CSA element included in the CSA frame is transmitted.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner The comparison is performed, and control is performed so that DFS Owner is stopped according to the comparison result.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
When a plurality of CSA frames are received, a CSA frame to be taken into by the wireless device is determined from the plurality of CSA frames according to identification information included in the CSA frames.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
It is characterized by having means for notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.

In addition, the wireless device according to the present invention is
Means for measuring the received signal strength for each wireless channel, and predicting the interference area of the wireless channel in which channel interference occurs for each wireless channel based on the received signal strength for each wireless channel;
Means for creating the list based on an interference area of a wireless channel predicted for each wireless channel.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. When the quiet count included in the beacon frame is larger than the quiet count of the wireless device itself, control is performed so as to ignore the beacon frame.

In addition, the wireless device according to the present invention is
A wireless device having a DFS function for avoiding interference with a radar,
Have multiple wireless interfaces,
Management means for managing channel information when radar is detected by the first wireless interface;
Control means for controlling to preferentially switch to a channel other than the channel managed by the management means when switching the channel of the second radio interface;
It is characterized by having.

<Wireless communication system>
Moreover, the wireless communication system according to the present invention includes:
It is characterized by having a plurality of the wireless devices described above.

<Control method>
Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
When the radar is detected, the wireless device performs a step of transmitting the Beacon frame with a transmission interval shorter than a preset transmission interval.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
When the CSA frame is received, the wireless device performs the step of transmitting the CSA frame including the CSA element included in the CSA frame.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner The wireless device performs a process of comparing and controlling to stop DFS Owner according to the comparison result.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
When the plurality of CSA frames are received, the wireless device performs a step of determining a CSA frame to be taken in by the wireless device from the plurality of CSA frames according to identification information included in the CSA frame. Features.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device performs a step of notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself, the wireless device performs a process of controlling to ignore the Beacon frame.

Further, the control method according to the present invention includes:
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device has a plurality of wireless interfaces,
A management process for managing channel information when radar is detected by the first wireless interface;
A control step of controlling to preferentially switch to a channel other than the channel managed in the management step when switching the channel of the second radio interface;
Is performed by the wireless device.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
When the radar is detected, the wireless device is caused to execute a process of transmitting the Beacon frame with a transmission interval shorter than a preset transmission interval.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
When the CSA frame is received, the wireless apparatus is caused to execute processing for transmitting the CSA frame including the CSA element included in the CSA frame.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner The wireless device is caused to execute a process of comparing and controlling to stop DFS Owner according to the comparison result.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
When receiving a plurality of CSA frames, causing the wireless device to execute a process of determining a CSA frame to be taken in by the wireless device from the plurality of CSA frames according to identification information included in the CSA frame. It is characterized by.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device is caused to execute a process of notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself, the wireless device is caused to execute a process of controlling to ignore the Beacon frame.

Further, the control program according to the present invention is:
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device has a plurality of wireless interfaces,
Management processing for managing channel information when radar is detected by the first wireless interface;
A control process for controlling to preferentially switch to a channel other than the channel managed in the management process when switching the channel of the second radio interface;
Is executed by the wireless device.

  According to the present invention, it is possible to realize a DFS function considering interference avoidance with a radar in an Ad-Hoc mode in a multi-hop environment.

It is a block diagram which shows the structure of the radio | wireless communications system of this embodiment. It is a figure which shows the structure of a Beacon / Probe Response frame. It is a figure which shows the structure of a Measurement Report frame. It is a figure which shows the structure of a Channel Switch Announcement frame. (A) shows the configuration of the IBSS DFS element, (b) shows the configuration of the Channel Switch Announcement element, and (c) shows the configuration of the Quiet element. is there. It is a figure for demonstrating the information contained in a frame, (a) is a figure for demonstrating the value of Action field contained in a frame, (b) is a subtype of the frame control contained in a frame. It is a figure for demonstrating. It is a figure for demonstrating the notification method of DFS Owner. It is a figure for demonstrating the case where a DFS Owner node detects a radar. It is the 1st figure for demonstrating the case where nodes other than a DFS Owner node detect a radar. It is the 2nd figure for demonstrating the case where nodes other than a DFS Owner node detect a radar. It is a figure for demonstrating the relationship of a quiet element. It is a figure for demonstrating the process outline | summary of a DFS function. It is a figure for demonstrating the subject to which communication cut | disconnects in a multihop environment. It is a figure for demonstrating the solution method of the subject which communication cuts off in a multihop environment. It is a figure for demonstrating the subject to which the trap of DFS Owner becomes slow. It is a figure for demonstrating the solution method of the problem which becomes slow in DFS Owner's trap. It is a figure which shows the structure of IBSS DFS element at the time of applying the solution method of the problem which becomes slow in DFS Owner's habit. It is a figure for demonstrating the subject which a some instruction | indication content generate | occur | produces. It is a figure for demonstrating the solution method of the subject which several instruction | indication content generate | occur | produces. It is a figure for demonstrating reception signal strength prediction function: f (x). It is a figure which shows the example of the radio | wireless apparatus used as the radio | wireless transmission source which exists in the periphery of a node. It is a figure which shows the measurement result when a node performs a channel scan process under the environmental conditions shown in FIG. It is a figure for demonstrating the subject from which a quiet period becomes asynchronous. It is a figure for demonstrating the solution method of the subject from which a quiet period becomes asynchronous. It is a figure for demonstrating the subject which MR (Measurement Report) frame and CSA (Channel Switch Announcement) frame collide. It is a figure for demonstrating the solution method of the subject which MR frame and CSA frame collide. It is a figure for demonstrating the subject in case the node carries several radio | wireless I / F, and its solution method.

  First, the system configuration of the wireless communication system of the present embodiment will be described with reference to FIG.

  The wireless communication system according to the present embodiment includes a plurality of nodes (N1 to N6). The nodes (N1 to N6) are devices that perform wireless communication, and examples thereof include a wireless base station: AP and a wireless terminal device: STA. In FIG. 1, six nodes (N1 to N6) are shown, but the number of nodes constituting the wireless communication system of the present embodiment is not particularly limited. The wireless communication system shown in FIG. 1 shows a multi-hop configuration, and the dotted line shows the topology. For this reason, the wireless communication system according to the present embodiment is capable of direct communication, for example, when the node N1 and the node N3 are in the same radio wave range, and when the node N1 and the node N4 are not in the same radio wave range. Will not be able to communicate directly.

  Next, the processing operation in the wireless communication system of this embodiment will be described.

  First, configurations of a Beacon / Probe Response frame, a Measurement Report frame, and a Channel Switch Announcement frame transmitted between the nodes will be described. 2 shows the configuration of the Beacon / Probe Response frame, FIG. 3 shows the configuration of the Measurement Report frame, and FIG. 4 shows the configuration of the Channel Switch Announcement frame. FIG. 5 shows the configuration of elements included in the frame, (a) shows the configuration of IBSS DFS element, (b) shows the configuration of Channel Switch Announcement element, and (c) shows Quiet element. The structure of is shown. FIG. 6 is a diagram for explaining information included in a frame, (a) is a diagram for explaining an action field value included in the frame, and (b) is included in the frame. It is a figure for demonstrating the subtype of frame control to be performed.

(DFS Owner notification method)
Next, a processing operation for notifying information on a DFS Owner when a node becomes the DFS Owner will be described with reference to FIG. DFS Owner means the person who adjusts the channel switch.

  First, it is assumed that the node (N1) starts IBSS (Independent Basic Service Set). As a result, the node (N1) becomes the DFS Owner (step S1).

  Next, the DFS Owner node (N1) transmits to the adjacent nodes (N2, N3) in the Beacon frame or Probe Response frame that it is a DFS Owner (step S2). At this time, the DFS Owner node (N1) includes the MAC address of the node (N1) itself in the DFS Owner of the IBSS DFS element included in Beacon.

  When a node (N2, N3) receives a Beacon frame or Probe Response frame, whether or not the BSSID included in the received frame matches the BSSID of the node (N2, N3) itself Judging. Then, when both BSSIDs match, the node (N2, N3) compares the Time Stamp included in the frame with the TSF timer value of the node (N2, N3) itself. If the time stamp included in the frame is delayed from the TSF timer value of the node (N2, N3) itself, the IBSS DFS element included in the frame starts with DFS Owner, DFS Recovery Interval, and other information. And a Beacon frame including the imported information is transmitted to an adjacent node (step S3). However, as described in Non-Patent Document 1, Beacon is transmitted in an autonomous distributed manner, and therefore cannot be transmitted until the transmission timing of Beacon reaches a node. Therefore, it should be noted that transmission is not always performed in this order.

  The nodes (N4 to N6) that have received the Beacon frame perform the same processing as in Step S3 described above, and transmit the Beacon frame including DFS Owner, DFS Recovery Interval, and other information to the adjacent nodes. (Steps S4 and S5). Thereby, each node (N2 to N6) grasps that the node (N1) is a DFS Owner.

(When DFS Owner node detects radar)
Next, a processing operation when the DFS Owner node detects a radar will be described with reference to FIG.

  First, when the DFS Owner node (N1) detects a radar (step A1), the DFS Owner node (N1) sends at least one CSA (Channel Switch Announcement) frame to the adjacent nodes (N2, N3). Transmit twice (broadcast) (step A2).

  The nodes (N2, N3) that have received the CSA frame transmit the CSA element included in the CSA frame to adjacent nodes in the Beacon frame when they can transmit the Beacon (step A3).

  The node (N4) that has received the Beacon frame transmits the CSA element included in the Beacon frame to an adjacent node in the Beacon frame when it can transmit the Beacon (Step A4). In addition, the node (N5, N6) that has received the Beacon frame transmits the CSA element included in the Beacon frame to the adjacent node in the Beacon frame when it can transmit the Beacon similarly to Step A4 described above. (Step A5).

(When a node other than the DFS Owner node detects radar: Part 1)
Next, a first processing operation when a node other than the DFS Owner node detects a radar will be described with reference to FIG. The following processing will be described when the node (N3) within the same radio wave range as the DFS Owner node (N1) detects the radar.

  First, when the node (N3) detects a radar (step B1), the node (N3) transmits an MR (Measurement Report) frame to the adjacent nodes (N1, N2, N4) at least once. (Unicast, or, broadcast) (step B2).

  The DFS Owner node (N1) that has received the MR frame transmits the CSA element included in the MR frame to the adjacent node in the CSA frame at least once (broadcast) (step B3).

  The nodes (N2, N3) that have received the CSA frame transmit the CSA element included in the CSA frame to adjacent nodes in the Beacon frame when they can transmit the Beacon (step B4).

  The node (N4) that has received the Beacon frame transmits the CSA element included in the Beacon frame to an adjacent node in the Beacon frame when it can transmit the Beacon (step B5). In addition, the node (N5, N6) that has received the Beacon frame transmits the CSA element included in the Beacon frame to the adjacent node in the Beacon frame when it can transmit the Beacon, as in Step B5 described above. (Step B6).

(When a node other than the DFS Owner node detects radar: Part 2)
Next, a second processing operation when a node other than the DFS Owner node detects a radar will be described with reference to FIG. The following processing will be described when a node (N4) within a radio wave range different from that of the DFS Owner node (N1) detects a radar.

  First, when the node (N4) detects a radar (step C1), the node (N4) transmits an MR (Measurement Report) frame to the adjacent nodes (N3, N5, N6) at least once. (Unicast, or, broadcast) (step C2).

  When the node (N4) cannot receive CSA even after the DFS Owner Recovery Interval has elapsed, the node (N4) shifts to the DFS Owner Recovery mode and becomes equivalent to the DFS Owner. However, if the node (N4) can receive CSA during the period of DFS Owner Recovery mode, it exits DFS Owner Recovery mode and returns to DFS Client. The DFS Client means a node that is not a DFS Owner and a node that is not in the DFS Owner Recovery mode.

  When the node (N4) becomes a DFS Owner (step C3), the node (N4) transmits a CSA frame to the adjacent nodes (N3, N5, N6) at least once (broadcast) (step C4). .

  The nodes (N3, N5, N6) that have received the CSA frame transmit the CSA element included in the CSA frame to adjacent nodes in the Beacon frame when they can transmit the Beacon (step C5). The nodes (N1, N2) that have received the Beacon frame transmit the CSA element included in the Beacon frame to an adjacent node in the Beacon frame when they can transmit the Beacon (Step C6).

  The node (N4) that has become the DFS Owner becomes a DFS Client by the IBSS DFS Element included in the Beacon frame received from the adjacent node after a while after the channel switch (step C7).

(Quiet mode)
Next, the quiet mode will be described.

  Each node schedules the Quiet interval with the Quiet element {Quiet Count, Quiet Period, Quiet Duration, Quiet Offset} in the Beacon / Probe Response frame to reduce the interference from other nodes and inspect the presence of the radar. It will be.

Here, Quiet element is shown below.
Quiet Count is a parameter indicating the number of Beacon frame transmission timings that occur until the no-communication section is started.

  Quiet Period is a parameter indicating the number of Beacon Intervals that occur during the start of consecutive no-communication intervals.

  Quiet Duration is a parameter indicating the time during which there is no communication period.

  Quiet Offset is a parameter indicating the offset time from the Beacon frame transmission timing with Quiet Count = 0 to the start of the no-communication section.

  The relationship between the above-described quiet elements is shown in FIG.

  Next, the problem in this embodiment and the solution method are demonstrated below.

(Issue: Each node cannot switch to the same channel during Channel Move Time in a multi-hop environment)
First, the problem that each node cannot switch to the same channel during Channel Move Time in a multi-hop environment will be described.

  The DFS function specified in ITU-R Recommendation M.1652 avoids the use of the same frequency as the radar operating in the same frequency band, so that the radio communication system and the radar system share the same frequency band. It consists of the following three basic functions.

1: Channel availability check function (CAC: Channel Availability Check)
Before the network is established, the radar detection function must perform radar detection for 60s to ensure that no radar is operating on that channel. During this time, no transmission should be performed. Further, when changing the operation channel, it is necessary to perform CAC even when the presence or absence of a radar signal in the change destination channel is not known.

2: In-service monitoring (ISM: In-Service Monitoring) and channel move time (Channel Move Time)
To ensure that no radar is operating on that channel during normal operation, the channel must continue to be monitored by the radar detection function (In-Service Monitoring).

  When a radar signal is detected, the operation channel becomes unusable. The node that has detected the radar signal must instruct all belonging nodes (communication partner nodes) to stop transmission on that channel within Channel Move Time (= 10 s).

  Note that all transmissions during Channel Move Time are limited to Channel Closing Transmission Time (= 260 ms).

3: Non-Occupancy Period
A channel in which a radar signal is detected shall not resume any transmission for 30 minutes (Non-Occupancy Period) after detecting the signal. The radar detection threshold (Interference Detection Threshold) is defined so that the radio communication system detects the radar at an interference level 20 to 35 dB lower than the minimum reception sensitivity of the weather radar and avoids the interference.

FIG. 12 shows the processing of the DFS function described above.
As shown in FIG. 12, when the power is turned on, the radar is monitored for 60 seconds by pre-operation monitoring (Channel Availability Check). When the radar is not detected by the pre-operation monitoring, the operation (transmission) is started. However, even during operation (transmission), radar on the channel being used is monitored by in-service monitoring (In-Service Monitoring). When a radar is detected during operation monitoring, the channel is handed over within Channel Move Time (= 10 s). And the channel which detected the radar becomes unusable for more than 30 minutes (Non-Occupancy Period).

  It should be noted that how many times the Beacon can be transmitted in the Channel Move Time (= 10 s) is examined based on the DFS function defined in the ITU-R recommendation M.1652.

Channel Move Time is 10 seconds and Channel Closing Transmission Time is 260 ms.
The Beacon Message is 200 bytes, the wireless standard is 11a, the wireless transmission rate is 6 Mbps, and the Beacon interval is 100 ms.

First, (1) the maximum number of transmissions is obtained from the bandwidth occupation time.
PLCP + (PLCP (service) + MAC + LLC + DATA + FCS + tail) byte / 6Mbps + SIFS + DIFS + BackOff
= 20us + (16bit + 24byte + 8byte + 160byte + 4byte + 6byte) / 6Mbps + 10us + 56us + average 150us = 285us + 10us + 56us + 150us = 501us
Channel Closing Transmission Time is 260ms
260ms / 501us ≒ 518 times

Next, (2) the maximum number of transmissions is obtained from the Beacon transmission interval.
10000ms / 100ms = 100 times

  (3) The number of transmissions required to reach N hops is obtained. In the present embodiment, approximation is performed using a simple model.

  Beacon assumes that all the nodes transmit once and repeat that as one cycle.

  The number of Beacon transmission cycles necessary for information to reach from one end node to the other end node: c is as follows.

  c = (N + 1) / 2

  The number of Beacon transmissions: m is as follows.

  m = cN = N (N + 1) / 2

  Assuming that there is no collision, since the maximum number of transmissions: m = 100, substituting m = 100 into the above equation and obtaining the number of hops: N allows up to N≈13 hops.

  Therefore, it is necessary to increase the number of hops: N in order to realize the DFS function defined by the above-mentioned ITU-R recommendation M.1652 in a multi-hop environment.

  For this reason, in this embodiment, the problem mentioned above is solved by applying the following methods.

(Solution method)
When radar is detected, the Beacon transmission interval is shortened.

The node that detects the radar performs an operation with a smaller Beacon interval.
Note that Beacon (200 bytes) can be transmitted 518 times during the Channel Move Time from the result of obtaining the maximum number of transmissions from the band occupation time.

  Assuming that there is no collision, since the maximum number of transmissions: m = 518, substituting m = 518 into the above equation and obtaining the number of hops: N allows up to N≈31 hops.

  For this reason, when the node in this embodiment detects a radar, it can increase the number of hops: N by performing an operation with a smaller Beacon interval. This makes it possible to implement the DFS function defined by the above-mentioned ITU-R recommendation M.1652 in a multi-hop environment.

(Issue: Communication is cut off in a multi-hop environment)
Next, a problem that communication is disconnected in a multi-hop environment will be described with reference to FIG.

  First, when the DFS Owner node (N1) detects a radar, the DFS Owner node (N1) transmits a CSA frame to the adjacent node (N2) at least once (broadcast) (step D1).

  The node (N2) that has received the CSA frame transmits the CSA element included in the CSA frame to an adjacent node in the Beacon frame when it can transmit the Beacon (step D2).

  The node (N3) that has received the Beacon frame transmits the CSA element included in the Beacon frame to an adjacent node in the Beacon frame when it can transmit the Beacon (Step D3). Since Beacon transmits autonomously and decentrally, it takes time. By convention, when a radar is detected, the channel must be surrendered within Channel Move Time (= 10s), but in a multi-hop environment, Channel Move Time (= 10s) and Channel Closing Transmission Time (= 260ms) By definition, the reach of the Beacon frame is limited. That is, the reach of the CSA element is limited. For this reason, there may occur a case where all the nodes (N1 to N6) cannot be changed to the same channel during Channel Move Time (= 10 s).

  When the Beacon frame has reached the node (N4) (step D4) and the channel move time (= 10s) has elapsed and the channel is to be changed, the node (N4), the node (N5), Will be cut off (step D5).

  Therefore, in order to realize the DFS function defined in the above-mentioned ITU-R recommendation M.1652 in a multi-hop environment, it is necessary to expand the reach of the CSA element when radar is detected.

  For this reason, in this embodiment, the following problem is solved by applying the following method shown in FIG. Hereinafter, a description will be given with reference to FIG.

(Solution method)
First, when the DFS Owner node (N1) detects a radar, the DFS Owner node (N1) transmits a CSA frame to the adjacent node (N2) at least once (broadcast) (step E1).

  The node (N2) that has received the CSA frame transmits the CSA element included in the CSA frame to the adjacent node using the CSA frame (step E2). Each node (N3, N4, N5) that has received the CSA frame transmits the CSA element included in the CSA frame to an adjacent node in the CSA frame (steps E3 to E5). Since the CSA frame is not transmitted in an autonomous distributed manner like Beacon, the CSA frame can be transmitted to the node (N6). Thereby, each node (N1-N6) can change a channel during Channel Move Time (= 10s) (step E6).

  As described above, when a node according to the present embodiment receives a CSA frame, the node detects the radar by detecting the radar by transmitting the CSA element included in the CSA frame to an adjacent node in the CSA frame. It is possible to expand the reach of the. As a result, each node (N1 to N6) can change the channel during the Channel Move Time (= 10s), and the DFS specified in the above-mentioned ITU-R recommendation M.1652 in a multi-hop environment. Functions can be realized.

  Note that the CSA frame can be transmitted by unicast, multicast, broadcast, or the like. When the CSA frame is transmitted by unicast or multicast, the existing routing function is used. Moreover, when transmitting by broadcast, it is preferable to use flooding.

  In the above-described embodiment, when each node receives a CSA frame, the node transmits a CSA element included in the CSA frame to an adjacent node using the CSA frame. It can also be constructed to transmit. In this case, as in the above-described embodiment, it is possible to construct the transmission so that the transmission interval (Beacon interval) of the Beacon frame is shortened.

(Issue: Slowness of DFS Owner)
Next, with reference to FIG. 15, the problem that the DFS Owner's habit is delayed will be described.

  First, the DFS Owner node (N1) leaves the IBSS (step F1).

  Next, it is assumed that each node (N2 to N6) has detected a radar (step F2). In this case, each node (N2 to N6) transmits an MR frame to an adjacent node (step F3). In this case, since each node (N2 to N6) does not respond to the MR frame, each node (N2 to N6) shifts to the DFS Owner Recovery mode and corresponds to the DFS Owner. Then, the DFS Owner node (N2 to N6) transmits the CSA frame to the adjacent node (step F4). When each DFS Owner node (N2 to N6) receives the CSA frame, the DFS Owner node exits the DFS Recovery mode, incorporates the CSA, and switches the channel (step F5).

  However, when each DFS Owner node (N2 to N6) transmits a CSA frame, a frame collision may occur. If all CSA frames collide by transmitting CSA frames at the same time, each DFS Owner node (N2 to N6) cannot receive the CSA frame and maintains the DFS Owner. Also, if some CSA frames collide, some nodes will maintain DFS Owner. Thereafter, the DFS Owner nodes (N2 to N6) receive the Beacon frame from the adjacent nodes, and control to stop the DFS Owner and shift to the DFS Client by the DFS element included in the received Beacon frame. This tricks DFS Owner. However, since the TSF timer values of the nodes (N2 to N6) are already synchronized, they are not easily overlooked. If the Time Stamp included in the Beacon frame is behind the TSF timer value of its own node, the information of the IBSS DFS element (DFS Owner, DFS Recovery Interval) included in the Beacon frame is taken in, and the DFS Owner is set. Because it will be controlled to shift to DFS Client, if the TSF timer value of each node (N2-N6) is synchronized, the information of DFS element will not be taken in. As a result, DFS Owner will be stopped, This is because it does not control to migrate to DFS Client.

  For this reason, in this embodiment, the problem mentioned above is solved by applying the following methods. Hereinafter, the method will be described with reference to FIGS. 16 and 17.

(Solution method)
First, when each node (N2 to N6) transitions to DFS Owner or DFS Owner Recovery mode and becomes equivalent to DFS Owner, the TSF timer when it becomes equivalent to DFS Owner or DFS Owner Store the value (OCT: Owner Create Time) in memory. Then, the DFS Owner or the DFS Owner node (N2 to N6) corresponding to the DFS Owner transmits the OCT together with the DFS Owner information to the adjacent node in the Beacon frame (step G1). Note that “OCT” is included in the IBSS DFS element and transmitted in a Beacon frame, as shown in FIG.

  Next, when a DFS Owner node (N2 to N6) receives a Beacon frame from another node, it refers to the DFS Owner included in the IBSS DFS element of the received Beacon frame, and the MAC included in the DSF Owner. Check if the address is a different MAC address from the DFS Owner node itself. If the MAC address included in the DSF Owner is a different MAC address from the DFS Owner node itself, the DFS Owner node (N2 to N6) and the OCT (received OCT) included in the IBSS DFS element and the DFS Owner node Compare your own OCT with your own OCT. If the OCT (receiving OCT) included in the IBSS DFS element is more advanced than the own OCT (own OCT) of the DFS Owner node (receiving OCT <own OCT), the DFS Owner node Control to move to DFS Client.

  Further, if the received OCT is not advanced from the own OCT (received OCT ≧ own OCT), the DFS Owner node maintains the DFS Owner as it is and ends the process.

  The DFS Owner node ends the process when the MAC address included in the DSF Owner is the same MAC address as the DFS Owner node itself.

  In this way, in this embodiment, when each node shifts to DFS Owner or DFS Owner Recovery mode and becomes equivalent to DFS Owner, the start time (which corresponds to DFS Owner or DFS Owner ( OCT). Then, the DFS Owner node notifies the neighboring node of the DFS Owner information and the OCT information thereof using a Beacon frame. Then, the DFS Owner node compares the DFS Owner information contained in the Beacon frame received from the other nodes with the DFS Owner information of the node itself. The OCT (reception OCT) included in the Beacon frame is compared with the OCT of the node itself (own OCT). Then, if the receiving OCT is ahead of its own OCT, control is performed so as to stop the DFS Owner and shift to the DFS Client.

  As a result, even if there is a situation where there are multiple DFS Owners or DFS Owner equivalents, the DFS Owner or the DFS Owner will be stopped according to the start time when the DFS Owner equivalents, and transition to DFS Client. Since it becomes possible to control, it becomes possible to speed up the DSF Owner's habit.

  In the above embodiment, when the OCT (reception OCT) included in the Beacon frame is more advanced than the OCT (self OCT) of the DFS Owner node itself (reception OCT <own OCT), the DFS Owner is changed. Stop and control to switch to DFS Client, and if the receiving OCT is not ahead of its own OCT (receiving OCT ≥ own OCT), the DFS Owner is maintained as it is and the processing is terminated. However, the determination method can be reversed. That is, if the OCT (Receive OCT) included in the Beacon frame is later than the OCT of the DFS Owner node itself (Receive OCT> OCT), the DFS Owner is stopped and the DFS Client is If the reception OCT is not delayed from the own OCT (reception OCT ≦ self OCT), the DFS Owner can be maintained as it is and the processing can be terminated.

  Normally, the person who became DFS Owner first takes precedence, so the OCT (received OCT) included in the Beacon frame is ahead of the OCT (self OCT) of the DFS Owner node itself. In this case (Receive OCT <Own OCT), control to stop DFS Owner and shift to DFS Client, and if the received OCT is not ahead of its own OCT (Receive OCT ≧ Own OCT), It is preferable to maintain the DFS Owner as it is and finish the process.

  In the above embodiment, the TSF timer value is used. However, each node is equipped with a timer count function, and the timer value counted by the timer count function can be used as the OCT.

In the above embodiment, it is determined whether or not the MAC address included in the DSF Owner is a MAC address different from that of the DFS Owner node itself, but each node can be identified like the MAC address. Any identification information can be applied as long as it is unique identification information.

(Problem: When multiple instructions occur)
Next, a problem in which a plurality of instruction contents occur will be described with reference to FIG.

  First, when the node (N4) detects a radar (step H1), the node (N4) transmits the MR frame to the adjacent nodes (N3, N5, N6) at least once (unicast, or broadcast) (step H2).

  In this case, since the node (N4) cannot receive CSA even after the DFS Owner Recovery Interval has elapsed, the node (N4) shifts to the DFS Owner Recovery mode and corresponds to the DFS Owner (step H3).

  When the node (N4) becomes the DFS Owner, the node (N4) transmits the CSA frame to the adjacent nodes (N3, N5, N6) at least once (broadcast) (step H4).

  At this time, if the node (N1) has also detected the radar, the node (N1) transmits the CSA frame at least once to the adjacent nodes (N2, N3) (step H5). ). In this case, the node (N3) receives the CSA frame from both the node (N4) and the node (N1). If the contents of the CSA frame are the same between the node (N4) and the node (N1), there is no problem even if the contents of the CSA frame are different. (N3) has a problem in that it cannot be determined whether to follow the contents of the CSA frame received from the node (N4) or the node (N1).

  For this reason, in this embodiment, the following problem is solved by applying the following method shown in FIG. Hereinafter, a description will be given with reference to FIG.

  First, when the node (N4) detects the radar (step I1), the node (N4) transmits the MR frame to the adjacent nodes (N3, N5, N6) at least once (unicast, or broadcast) (step I2).

  In this case, since the node (N4) cannot receive CSA even after the DFS Owner Recovery Interval has elapsed, the node (N4) shifts to the DFS Owner Recovery mode and corresponds to the DFS Owner (step I3).

  When the node (N4) becomes the DFS Owner, the node (N4) transmits the CSA frame to the adjacent nodes (N3, N5, N6) at least once (broadcast) (step I4).

  At this time, if the node (N1) has also detected the radar, the node (N1) transmits the CSA frame at least once to the adjacent nodes (N2, N3) (step I5). ). In this case, the node (N3) receives the CSA frame from both the node (N4) and the node (N1).

  Note that the node (N3) in the present embodiment compares the source address included in the CSA frame and controls to incorporate the CSA frame having the smaller (or larger) source address (step I6). FIG. 19 shows a case where the CSA frame of the node (N4) is taken. As a result, even if both of the CSA frames of the node (N4) and the node (N1) are different, the node (N3) depends on the source address included in the CSA frame. Can be incorporated. Note that the setting of whether to incorporate the CSA frame having the smaller or larger source address is set in advance in the node (N3) itself.

  In the above embodiment, it is determined which CSA frame is to be taken in based on the source address included in the CSA frame. However, the unique identification information set in each node (for example, the enclosure) It is also possible to construct such that a body number or the like) is included in a CSA frame and which CSA frame is to be incorporated is determined based on the unique identification information included in the CSA frame. Since the MAC address is already included in the CSA frame, it is possible to use the MAC address included in the CSA frame.

  In addition, a list of channels used as an index for channel switching when radar is detected is shared among the nodes (N1 to N6) so that the contents of the CSA frame do not differ between the nodes (N1 to N6). Is also possible. As a result, even if the node (N3) receives both the CSA frames of the node (N4) and the node (N1), the contents of both CSA frames are the same. However, no problem will occur. The list can be constructed so that the list is shared between the nodes by notifying each node of the list created by the user or setting the list in each node. It is also possible to construct so that each node can share the list by generating each node autonomously and notifying each node of the generated list. A list creation method will be described below.

<How to create a list>
First, the node performs channel scan processing and measures the radio channel conditions around the node. As a result, the node can measure the received signal strength for each radio channel. Next, the node generates channel scan information for each radio channel based on the received signal strength measured by the above processing.

  In the present embodiment, by using the received signal strength prediction function: f (x), the channel scan information: Sm of the radio channel: m is calculated by the following (Equation 1).

  Where N: total number of received signal strengths, Rn: value of received signal strength, f (x): received signal strength prediction function, m: range of radio channel, Cn: radio channel number.

  The received signal strength prediction function: f (x) is, for example, a quadratic function as shown in FIG. 20, and a function obtained from the spread spectrum of the frequency arrangement can be applied. A function considering the rate can also be applied. Further, since the maximum range of the radio channel number: M varies depending on the radio system and country, it goes without saying that the radio channel range: m can be configured to be arbitrarily changed.

  Note that the received signal strength prediction function: f (x) assumes a radio wave transmission spectrum, and therefore, as shown in FIG.

  However, in practice, an analysis process, which will be described later, is performed from the radio signal sequence received by the node, power spectrum density: P (f) is obtained, and the peak value of the obtained power spectrum ram density: P (f) is obtained. The function: f (x) becomes the received signal strength prediction function: f (x).

  In the analysis process, the power spectrum density: P (f) can be obtained by directly Fourier-transforming the radio signal sequence received by the node. For example, the case where the power spectral density of a certain time waveform: x (t) is P (f) gives power: Pt for a frequency component in a certain minute interval (f, f + df). (Expression 2) is established.

  However, t2 and t1 indicate arbitrary times, and the definition of P (f) is as follows (Formula 3).

  Since the above-described analysis process is difficult only from existing information, it is preferable to calculate a pseudo function f (x) from a typical spectrum.

  Moreover, it is preferable to apply the following (Equation 4) as the pseudo function f (x) indicating the spectrum described above.

  Further, in the case of the wireless standard 11g, it is preferable to apply the following (Equation 5) as the pseudo function f (x) indicating the spectrum mask described above. Thereby, the processing can be simplified as compared with the case where the function: f (x) shown in (Expression 4) is applied. In the case of the wireless standard 11a, it is preferable to apply the following (Formula 5.1).

  It is assumed that a wireless device serving as a wireless transmission source as shown in FIG. 21 exists around the node. When the node performs a channel scan process under the environmental conditions shown in FIG. 21 and the radio channel conditions around the node are measured for each radio channel, a measurement result as shown in FIG. 22 is obtained.

  The measurement result shown in FIG. 22 shows the measurement result obtained when the node performs channel scan processing and the received signal strength is measured for each of the wireless channels x to 100 to 140. Note that “x” in FIG. 22 indicates the measurement result of the received signal strength.

  FIG. 22 shows that there is a wireless device (G) that uses the wireless channel 100ch, and its received signal strength is 90. Similarly, there is a wireless device (B) that uses 108 ch, and the received signal strength is 30. Further, there is a wireless device (F) using 120 ch, and the received signal strength is 41. Also, there is a wireless device (A) that uses 120 ch, and the received signal strength is 65. Also, there is a wireless device (E) that uses 124ch, and the received signal strength is 41. Further, it is indicated that there is a wireless device (D) using 136 ch and the received signal strength is 12. Further, it is indicated that there is a wireless device (C) using 140 ch and the received signal strength is 28.

  Note that the received signal strength described above can be measured by applying a known channel scan method. For example, it is possible to measure the received signal intensity by applying the scan method disclosed in Non-Patent Document 1, and active scan, passive scan, etc. can be applied. The active scan is a method for searching a network by exchanging Probe Request / Response frames. Passive scan is a method for searching a network by monitoring beacon.

  Further, the channel scan information Si indicated by the “solid line” in FIG. 22 indicates the calculation result of the received signal strength prediction function: f (x) according to the above-described (Equation 5). It shows that interference occurs. That is, the interference area corresponding to the received signal strength (90) of the radio channel 100 ch is a range up to 104 ch.

  As described above, the node in the present embodiment calculates the received signal strength prediction function: f (x) based on the received signal strength measured by applying a known channel scan method, and the radio channel in which channel interference occurs. Will be predicted for each radio channel. Then, the node calculates channel scan information Si based on the radio channel interference area predicted for each radio channel, and an index for channel switching when radar is detected based on the calculated channel scan information Si. A list of channels will be created. Note that it is preferable to create a list so that channels that do not interfere are preferentially used as channels that are channel-switched when radar is detected. As a result, each node (N1 to N6) notifies the peripheral node of the created channel list, and the channel list is shared among the nodes so that the content of the CSA frame does not differ between the nodes. It becomes possible to. In FIG. 22, the value of the received signal strength is applied, but a logarithmic value can also be applied. The list creation method described above is a suitable method in the present embodiment, but the list creation method in the present embodiment is not limited to the method described above, and the list described above by applying any method. It is possible to build to create

(Issue: Quiet period is asynchronous)
Next, a problem in which the quiet period is asynchronous will be described with reference to FIG.

  First, a plurality of DFS Owner nodes (N1, N4) include a Quiet Element in a Beacon frame or Probe Response frame and transmit the frame to an adjacent node. Only the DFS Owner node will incorporate the Quiet Element into the frame (step J1).

  Due to the Quiet Element instruction of the DFS Owner node (N1), Quiet Count = 0 and the nodes (N1, N2, N3) perform a Quiet operation (Step J2).

  In addition, the Quiet Count of the DFS Owner node (N4) is also decreased by 1, and Quiet Count = 1 (Step J3).

  Next, Quiet Count = 0 by the Quiet Element instruction of the DFS Owner node (N4), and the nodes (N3, N4, N5, N6) perform a Quiet operation (Step J4).

  In the above process, the node (N3) performs the quiet operation twice. Since the transmission process cannot be performed during the quiet operation, the communication efficiency decreases.

  For this reason, in the present embodiment, the above-described problem is solved by applying the following method shown in FIG. Hereinafter, a description will be given with reference to FIG.

(Solution method)
First, each node compares the Quiet count (reception Quiet Count) included in the Quiet Element of the Beacon frame with its own Quiet Count (self Quiet Count). When the reception Quiet Count is smaller than its own Quiet Count (reception Quiet Count <self Quiet Count), each node changes the value to the reception Quiet Count. Further, each node ignores the value of the received quiet count without changing the value of the received quiet count if the received quiet count is not smaller than the own quiet count (reception quiet count ≧ self quiet count).

  For example, referring to FIG. 24, when the DFS Owner node (N1) has passed the time for transition to Quiet mode (Quiet mode transition timer time-up), the DFS Owner node (N1) = Beacon frame including Quiet Element of 4 is transmitted (Beacon transmission: Quiet Count = 4). The DFS Owner node (N1) decreases the Quiet Count by one and transmits a Beacon frame including a Quiet Element including the value of the Quiet Count. Then, the DFS Owner node (N1) starts the transmission stop timer when Quiet Count = 0.

  The DFS Client node (N3) is synchronized with the DFS Owner node (N1) (Quiet Count = 4). After that, the Quiet Count is decremented by 1 and includes a Quiet Element including the Quiet Count value. A Beacon frame will be transmitted. Then, when Quiet Count = 0, the transmission stop timer is started.

  Also, the DFS Owner node (N4), like the DFS Owner node (N1) described above, after shifting to the Quiet mode (Quiet mode transition timer time-up), the Beacon frame including the Quiet Element with Quiet Count = 4 Transmission (Beacon transmission: Quiet Count = 4), and thereafter, the Quiet Count is decreased by one and a Beacon frame including a Quiet Element including the value of the Quiet Count is transmitted. Then, when Quiet Count = 0, the transmission stop timer is started.

  When the DFS Client node (N3) in this embodiment receives a Beacon frame including a Quiet Element with Quiet Count = 4 from the DFS Owner node (N4), the node receives a Quiet Count = 4 of the received frame. (N3) Compares its own Quiet Count = 3, and determines that the Quiet Count = 4 of the frame is larger than the Quiet Count = 3 of the node (N3) itself. In this case, the DFS Client node (N3) ignores the frame's Quiet Count = 4 (step K1).

  In addition, when the DFS Owner node (N4) receives a Beacon frame including a Quiet Element with Quiet Count = 2 from the DFS Client node (N3), the node (N4) itself receives the Quiet Count = 2 of the received frame. Thus, it is determined that the Quiet Count = 2 of the frame is smaller than the Quiet Count = 4 of the node (N4) itself. In this case, the DFS Owner node (N4) changes its own Quiet Count to Quiet Count = 2 based on the Quiet Count = 2 of the frame (Step K2).

  Thus, when a node in this embodiment receives a Beacon frame, it compares the Quiet Count included in the Beacon frame with the Quiet Count of the node itself, and the Quiet Count included in the Beacon frame is the node itself. If the value is smaller than the current Quiet Count, the Quiet Count of the node itself is changed to the Quiet Count included in the Beacon frame. Further, when the quiet count included in the beacon frame is larger than the quiet count of the node itself, the beacon frame is ignored. Thereby, it is possible to reduce overlapping quiet operations.

(Issue: Collision between MR frame and CSA frame)
Next, a problem that MR frames and CSA frames collide will be described with reference to FIG.

  First, the DFS Owner node (N1) leaves the IBSS (step L1).

  Then, it is assumed that each node (N2 to N6) has detected a radar (step L2). In this case, each node (N2 to N6) transmits the MR frame to an adjacent node (unicast, or, broadcast) (step L3).

  Note that there is a possibility of frame collision when an MR frame is transmitted. In particular, when an MR frame is transmitted by broadcast, the probability that a frame collision will occur increases. Therefore, useless frame transmission is performed.

  Since the DFS Client nodes (N2 to N6) do not respond to the MR frame, the DFS Client node (N2 to N6) is equivalent to the DFS Owner. Then, the DFS Owner node (N2 to N6) transmits the CSA frame to the adjacent node (step L4).

  Note that when a CSA frame is transmitted, there is a possibility that a frame collision occurs as in the MR frame. When all the CSA frames collide, the DFS Owner nodes (N2 to N6) cannot receive the CSA frame, and the state where there are a plurality of DFS Owners continues. When some CSA frames collide with each other, some nodes continue to exist as DFS Owners.

  For this reason, in the present embodiment, the above-described problem is solved by applying the following method shown in FIG. Hereinafter, a description will be given with reference to FIG.

(Solution method)
First, the DFS Owner node (N1) leaves the IBSS (step M1).

  Then, it is assumed that each node (N2 to N6) has detected a radar (step M2). In this case, each node (N2 to N6) transmits the MR frame to an adjacent node (unicast, or, broadcast) (step M3).

  In this embodiment, in step M3, each node (N2 to N6) controls to transmit an MR frame after waiting for an arbitrary time (random time). Thereby, it is possible to reduce frame collision of MR frames. Note that the calculation method of the waiting time is not particularly limited, and any calculation method can be applied to calculate the random time. For example, it is possible to apply a random number or calculate the time based on the MAC address.

  Next, since the DFS Client node (N2 to N6) does not respond to the MR frame, it shifts to DFS Owner Recovery mode, and the DFS Client node (N2 to N6) waits for an arbitrary time (random time) Later, it became DFS Owner equivalent. Then, the DFS Owner node (N2 to N6) transmits the CSA frame to the adjacent node (unicast, broadcast, multicast). In this embodiment, each node (N2 to N6) controls to transmit a CSA frame after waiting for an arbitrary time (random time). Thereby, it becomes possible to reduce the frame collision of the CSA frame. In the present embodiment, it is assumed that the node (N3) first transmits a CSA frame (step M4).

  In this case, the node (N4) receives the CSA frame and switches the channel in the same manner as in the sequence when the DFS Owner detects the channel (step M5).

  As described above, the node in this embodiment can avoid the frame collision by transmitting the MR frame or the CSA frame after waiting for an arbitrary time (random time).

(Issue: When a node has multiple wireless I / Fs)
Next, a problem when a node is equipped with a plurality of wireless I / Fs will be described with reference to FIG.

  When a node is equipped with a plurality of wireless I / Fs, a radar is detected by one wireless I / F (for example, the first wireless I / F: 100) and then another wireless I / F. When the radar is detected even (for example, the second wireless I / F: 200), the second wireless I / F (200) is the radar already detected by the first wireless I / F (100). It is assumed that the channel is switched to the channel.

  For example, it is assumed that the node (N3) uses the channel 100ch in the first radio I / F (100) and uses the channel 124ch in the second radio I / F (200). In this state, when the first wireless I / F (100) detects a radar of channel 100ch, the first wireless I / F (100) performs channel switching. When the radar of the channel 124ch is detected also in the second wireless I / F (200), the second wireless I / F (200) performs channel switching. At this time, when the second radio I / F (200) is channel-switched to the channel 100ch, the radar of the channel 100ch already detected by the first radio I / F (100) is detected. Since 100ch once detected radar often detects radar again, the channel is switched again. For this reason, a wasteful channel switch occurs in a node equipped with a plurality of wireless I / Fs (100, 200).

  For this reason, in this embodiment, the problem mentioned above is solved by applying the following methods. Hereinafter, a description will be given with reference to FIG.

(Solution method)
First, it is assumed that the node (N3) uses the channel 100ch in the first radio I / F (100) and uses the channel 124ch in the second radio I / F (200). In this state, when the radar is detected by the first wireless I / F (100), the node (N3) manages channel information (channel 100ch) when the radar is detected by the node (N3). Next, the node (N3) transmits a CSA frame to the adjacent nodes (N1, N2) to perform channel switching.

  Next, the node (N3) performs a channel switch when the radar is detected even in the second wireless I / F (200). In this case, the node (N3) preferentially switches the channel of the second wireless I / F (200) to a channel (for example, 136ch) other than the channel information (channel 100ch) managed by the node (N3). Control to do. Thus, the node (N3) does not switch the channel to the radar channel 100ch detected by the first wireless I / F (100) when performing the channel switch of the second wireless I / F (200). It becomes possible to control. As a result, it is possible to reduce the situation in which the second wireless I / F (200) detects radar and to prevent useless channel switches from occurring.

  The node (N3) uses the radar channel information detected by the first radio I / F (100) and the other node (N4) sharing the channel of the second radio I / F (200). It is also possible to notify. As a result, the node (N4) can manage the radar channel information detected by the other node (N3). For this reason, when the node (N4) itself performs channel switching, it can be controlled to switch to a channel other than the channel when the other node (N3) detects the radar based on the channel information. It becomes possible.

  In the above description, the case where a plurality of wireless I / Fs (100, 200) mounted on the node (N3) use different channels has been described as an example, but a plurality of wireless I / Fs (100, 200) are used. ) Is also applicable when using the same channel. In this case, the node (N3) can also be controlled to perform the channel switch of the second radio I / F (200) when the radar is detected by the first radio I / F (100). is there. If the second wireless I / F (200) and the first wireless I / F (100) are not communicating, the second wireless I / F is the same as described above. When (200) detects a radar, it is also possible to perform control so as to perform channel switching.

  Thus, the node in this embodiment manages channel information when the radar is detected by the first wireless I / F (100). Then, when channel switching of the second wireless I / F (200) is performed, control is performed so that channel switching is preferentially performed on channels other than the channel managed by the node itself. Thereby, when the second wireless I / F (200) performs channel switching, the node can reduce the switching to the radar channel detected by the first wireless I / F (100). Therefore, useless channel switching can be prevented. Also, channel interference with the radar can be reduced.

  In addition, the node notifies the other nodes sharing the channel with the second wireless I / F (200) of the channel information managed by the node itself, and manages the channel information in the other nodes. . As a result, when another channel uses a channel of channel information in another wireless I / F, control is performed so that the channel is switched to another channel, or when channel switching is performed next time, It is possible to perform control so that channels other than the channel information are preferentially channel-switched.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone. Those skilled in the art will not be able to deviate from the gist of the present invention. It is possible to construct a form in which various changes are made by making corrections and substitutions.

  For example, in the above-described wireless communication system according to the present embodiment, the processing operation for realizing the DFS function defined by ITU-R recommendation M.1652 in a multi-hop environment has been described. If the DFS function considering interference avoidance with the radar can be realized like the DFS function defined in 652, it can be applied to various DFS functions.

  Further, in the above-described embodiment, the problem and the solution technique are associated with each other and described independently. However, a configuration for realizing each solution technique may be provided independently, and a plurality of configurations may be provided. It is possible to construct such that they are provided in combination.

  In addition, the control operation in each node configuring the wireless communication system in the present embodiment described above can be executed using hardware, software, or a combined configuration of both.

  In the case of executing processing using software, it is possible to install and execute a program in which a processing sequence is recorded in a memory in a computer incorporated in dedicated hardware. Alternatively, the program can be installed and executed on a general-purpose computer capable of executing various processes.

  For example, the program can be recorded in advance on a hard disk or ROM (Read Only Memory) as a recording medium. Alternatively, the program can be stored (recorded) temporarily or permanently in a removable recording medium. Such a removable recording medium can be provided as so-called package software. Examples of the removable recording medium include a floppy (registered trademark) disk, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto optical) disk, a DVD (Digital Versatile Disc), a magnetic disk, and a semiconductor memory.

  The program is installed in the computer from the removable recording medium as described above. In addition, it is wirelessly transferred from the download site to the computer. In addition, it is transferred to the computer via a network by wire.

  In addition, the wireless communication system in the present embodiment is not only executed in time series according to the processing operations described in the above embodiment, but also the processing capability of the apparatus that executes the processing, or in parallel or individually as required. It is also possible to build to run on

  In addition, the wireless communication system in the present embodiment can also be constructed so as to have a logical set configuration of a plurality of devices.

The present invention can be applied to an apparatus that performs DFS (Dynamic Frequency Selection) in an Ad-Hoc mode in a multi-hop environment.
(Appendix 1)
A wireless device having a DFS function for avoiding interference with a radar,
A radio apparatus that transmits a Beacon frame with a transmission interval shorter than a preset transmission interval when radar is detected.
(Appendix 2)
A wireless device having a DFS function for avoiding interference with a radar,
A wireless device that transmits a CSA frame including a CSA element included in the CSA frame when the CSA frame is received.
(Appendix 3)
The wireless apparatus according to appendix 2, wherein the CSA frame is transmitted after waiting for a random time.
(Appendix 4)
A wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner A wireless device characterized by comparing and controlling to stop DFS Owner according to the comparison result.
(Appendix 5)
Means for transmitting the start time in a Beacon frame;
When a Beacon frame is received, a control unit that compares the start time of other wireless devices included in the Beacon frame with the management time, and controls to stop DFS Owner according to the comparison result;
The wireless apparatus according to appendix 4, characterized by comprising:
(Appendix 6)
A wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
A wireless device, wherein when a plurality of CSA frames are received, a CSA frame to be taken in by the wireless device is determined from among the plurality of CSA frames according to identification information included in the CSA frame.
(Appendix 7)
A wireless device having a DFS function for avoiding interference with a radar,
A wireless device comprising means for notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.
(Appendix 8)
Means for measuring the received signal strength for each wireless channel, and predicting the interference area of the wireless channel in which channel interference occurs for each wireless channel based on the received signal strength for each wireless channel;
Means for creating the list based on a radio channel interference area predicted for each radio channel;
The wireless device according to appendix 7, characterized by comprising:
(Appendix 9)
A wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. The wireless device is characterized in that, when the Quiet Count included in the Beacon frame has a value larger than the Quiet Count of the wireless device itself, control is performed so as to ignore the Beacon frame.
(Appendix 10)
A wireless device having a DFS function for avoiding interference with a radar,
Have multiple wireless interfaces,
Management means for managing channel information when radar is detected by the first wireless interface;
Control means for controlling to preferentially switch to a channel other than the channel managed by the management means when switching the channel of the second radio interface;
A wireless device comprising:
(Appendix 11)
11. The wireless apparatus according to appendix 10, further comprising a notification means for notifying other wireless apparatuses sharing a channel with the second wireless interface, information on a channel managed by the management means.
(Appendix 12)
A wireless communication system comprising a plurality of wireless devices according to any one of appendices 1 to 11.
(Appendix 13)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
A control method characterized in that, when a radar is detected, the radio apparatus performs a step of transmitting a transmission interval of a Beacon frame shorter than a preset transmission interval.
(Appendix 14)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
A control method, wherein when a CSA frame is received, the wireless apparatus performs a step of transmitting a CSA frame including a CSA element included in the CSA frame.
(Appendix 15)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner A control method, wherein the wireless device performs a process of comparing and controlling to stop DFS Owner according to the comparison result.
(Appendix 16)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
When the plurality of CSA frames are received, the wireless device performs a step of determining a CSA frame to be taken in by the wireless device from the plurality of CSA frames according to identification information included in the CSA frame. Characteristic control method.
(Appendix 17)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
A control method, characterized in that the wireless device performs a step of notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.
(Appendix 18)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself, the wireless device performs a step of controlling to ignore the Beacon frame.
(Appendix 19)
A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device has a plurality of wireless interfaces,
A management process for managing channel information when radar is detected by the first wireless interface;
A control step of controlling to preferentially switch to a channel other than the channel managed in the management step when switching the channel of the second radio interface;
The control method characterized in that the wireless device performs.
(Appendix 20)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
A control program that causes the wireless device to execute processing for transmitting a Beacon frame with a transmission interval shorter than a preset transmission interval when radar is detected.
(Appendix 21)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
A control program that causes the wireless device to execute processing for transmitting a CSA frame including a CSA element included in the CSA frame when the CSA frame is received.
(Appendix 22)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
Start time at which DFS Owner is entered, or shift to DFS Owner Recovery mode to manage the start time at which DFS Owner is equivalent, and the management time and the start time at which other wireless devices become DFS Owner A control program that causes the wireless device to execute a process of comparing and controlling to stop DFS Owner according to the comparison result.
(Appendix 23)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
The CSA frame contains identification information for uniquely identifying each device,
When receiving a plurality of CSA frames, causing the wireless device to execute a process of determining a CSA frame to be taken in by the wireless device from the plurality of CSA frames according to identification information included in the CSA frame. A control program characterized by
(Appendix 24)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
A control program for causing a wireless device to execute processing for notifying a peripheral wireless device of a list of channels serving as an index for channel switching when a radar is detected.
(Appendix 25)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
When the Beacon frame is received and the Quiet Count included in the Beacon frame is smaller than the wireless device's own Quiet Count, the wireless device's own Quiet Count is changed to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame has a value larger than the Quiet Count of the wireless device itself, the control program causes the wireless device to execute a process of controlling to ignore the Beacon frame.
(Appendix 26)
A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
The wireless device has a plurality of wireless interfaces,
Management processing for managing channel information when radar is detected by the first wireless interface;
A control process for controlling to preferentially switch to a channel other than the channel managed in the management process when switching the channel of the second radio interface;
Is executed by the wireless device.

N1 to N6 nodes (wireless devices)
100, 200 wireless I / F

Claims (4)

A wireless device having a DFS function for avoiding interference with a radar,
When a Beacon frame is received, if the Quiet Count included in the Beacon frame is smaller than the Quiet Count of the wireless device itself, the Quiet Count of the wireless device itself is set to the Quiet Count included in the Beacon frame. The wireless device is controlled to ignore the Beacon frame when the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself.   A wireless communication system comprising a plurality of wireless devices according to claim 1. A control method performed by a wireless device having a DFS function for avoiding interference with a radar,
When a Beacon frame is received, if the Quiet Count included in the Beacon frame is smaller than the Quiet Count of the wireless device itself, the Quiet Count of the wireless device itself is set to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself, the wireless device performs a step of controlling to ignore the Beacon frame. Control method. A control program to be executed by a wireless device having a DFS function for avoiding interference with a radar,
When a Beacon frame is received, if the Quiet Count included in the Beacon frame is smaller than the Quiet Count of the wireless device itself, the Quiet Count of the wireless device itself is set to the Quiet Count included in the Beacon frame. When the Quiet Count included in the Beacon frame is larger than the Quiet Count of the wireless device itself, the wireless device is caused to execute a process of controlling to ignore the Beacon frame. A characteristic control program.

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