KR20060008217A - System and method for dynamically shifting of beacons in distributed wireless networks - Google Patents

Abstract

A system and method for dynamic beacon movement in a distributed wireless network is disclosed. According to the present invention, in a medium access control for Wireless Personal Area Networks based on wireless mobile ad-hoc networks, beacons are assigned to other leading free slots in order to reduce the size of the beacon section. Suggests ways to move around. Furthermore, we propose a method to detect collisions that may occur due to the movement of beacons and to prevent collisions. According to the present invention, by dynamically reducing the size of the beacon section without collision, it is possible to sufficiently secure the size of the data section to which data can be transmitted.

WPAN, wireless mobile ad-hawk network, beacon, beacon mobile, free lower slot

Description

System and method for dynamically shifting of beacons in distributed wireless networks

1 illustrates a personal wireless network in a conventional decentralized approach;

2 is a diagram illustrating an example of a structure of a conventional superframe;

3 is a diagram illustrating a network including a device for dynamic beacon movement in a distributed wireless network of the present invention;

4 is a view for explaining beacon section occupation information of the present invention;

5 is a flowchart provided to explain a beacon movement method of a system for dynamic beacon movement in a decentralized wireless network according to the present invention;

6 is a flowchart provided to explain a collision prevention method according to beacon movement of a system for dynamic beacon movement in a decentralized wireless network according to the present invention.

The present invention relates to devices in a network of media access control for wireless personal area networks based on wireless mobile ad-hoc networks. A system and method for dynamic beacon movement in a decentralized wireless network for effectively sending the data.

Personal wireless networks are defined as operating in private areas around 10 meters. The Institute of Electrical and Electronics Engineers (IEEE) has been involved in setting standards for such personal wireless networks. Ultra Wide Band (UWB) communications technology can provide transfer rates in excess of hundreds of Mbps in this private domain. In a personal wireless network, the medium is shared between all devices for communication with each other. This requires a media access control method for controlling the media access of the devices. This method of media access control can broadly identify how to access the network, how to transmit data to other devices at the desired transmission rate, how to best use the medium, and how to detect beacon collisions. Includes whether it can be resolved.

Media access control for personal wireless networks can be designed in two approaches: centralized and distributed. In a centralized approach, each device operates for the entire network to manage and coordinate media access for all devices. All devices require the assistance of a centralized coordinator for media access, such as joining the network or allocating channel time.

In the decentralized approach, the media access is evenly distributed to all devices in the network. And all devices share the burden of managing each other's media access. Although the IEEE standard is for centralized media access control methods, several decentralized media access control methods are being discussed for personal wireless networks. Such a method provides flexibility for the mobility of the devices.

1 is a diagram illustrating a personal wireless network in a conventional decentralized approach.

Referring to Figure 1, it includes several devices indicated by dots. The circle drawn around each device represents the range in which the beacon of the device is received. No device in the network is a dedicated coordinator.

Personal wireless networks based on a decentralized approach do not have any centralized coordinator. All devices in the network act as hard coordinators and do not include a separate dedicated coordinator. All devices cooperate with each other. In addition, each device shares information necessary to perform media access control, such as channel time allocation for data transmission to another device, access of new devices, and a synchronization method. This is a decentralized personal wireless network system formed in an ad-hoc type. Each device periodically broadcasts information about its peripheral devices and information about the channel time assigned to its peripheral devices.

Decentralized media access control relies on a timing concept called "superframe." Superframes have a fixed length of time and are divided into a number of time windows called 'time slots'. Some time slots are used by devices to send beacons, while others are used by devices to send data. Slots to which beacons are sent are called 'beacon slots' and slots to which data is sent are called 'data slots'.

The length of the beacon period (BP) consisting of beacon slots may be smaller than the length of the data period consisting of data slots. Beacon slots may be distributed over the entire slot of the superframe, or may appear together at the beginning of the superframe. In addition, the number of beacons may be fixed and may vary as connected to other configurations of distributed media access control.

2 is a diagram illustrating an example of a structure of a conventional superframe.

The structure of the superframe shown in FIG. 2 is based on what is defined by Multiband Orthogonal Frequency Division Modulation (OFDM) Alliance draft v0.5. This includes several Medium Access Slots (MAS) (a, c). Some medium access slots (including a) consist of a beacon period b which consists of matching beacon slots in a plurality of devices. The remaining media access slots (including c) form a data interval d consisting of media access slots that can be used by other devices in the network to deliver data to other devices in the network. One superframe is 65,536 ms and each media access slot is 256 ms.

The beacon interval (b) of the superframe has a variable length, i.e., when the number of beacons is larger, the beacon interval becomes longer, and conversely, when the number of beaconing devices is smaller, the length of the beacon interval decreases. Means that. It is useful for the aspect of power saving, as well as securing a larger data section d for superframe data communication when there are few devices to communicate.

The information on the superframe is broadcast through the beacon broadcast by each device in the beacon section (b). So the neighboring devices of the device can use the information for subsequent processing. The start time of a superframe is determined by the start of a beacon period, which is defined as a beacon period start time (BPST).

Devices can use the same beacon start time for superframes. Media access slots are numbered with respect to this start time. All devices will hear the beacon at the start of the superframe and be time synchronized.

Beacons broadcast by devices include Beacon Period Occupancy Information Element (BPOIE). The beacon section occupation information includes beacon information of neighboring devices identified in the beacon section b by the corresponding device. Upon receiving the beacon, the device stores the sender's device identifier (DEVID) along with the slot number from which the beacon was received. In the next superframe, the device includes the stored information in the beacon section occupation information of the beacons that it broadcasts. The information of the beacons received during one superframe is included in the beacon section occupation information sent in the next superframe. Note that the beacon section occupancy information is a method of indicating the occupation of a beacon slot by a device in a two hop region and it is independent of the beaconing procedure.

If the DEVID of a device is not visible in the beacon section occupancy information of the neighboring device beacon for a predetermined successive superframe, it means that the device will change the beacon slot to the idle slot in the next superframe.

However, the conventional technique is to allow devices to move beacon slots that send beacons so that the overall size of the beacon sections is dynamically reduced, allowing more of the superframe to be used for data transmission or power savings. none.

In an environment where many devices are used, large beacon sections can be established and the beacon slots they use can be freed as the devices leave the area or power off. That is, these free slots may occur in the middle of the beacon section. However, even when there are free slots in the beacon section, the size of the beacon section is maintained as it is, so that the use of the channel time of the superframe becomes inefficient.

Furthermore, because of the large beacon intervals with fewer beacons, devices must operate for many hours, which conflicts with the need for power savings.

Accordingly, an object of the present invention is to move a beacon into a beacon slot by moving a beacon to another beacon slot in a wideband (UWB) personal wireless network based on a wireless ad-hoc network in a decentralized network topology. It is to provide a system and method for dynamic beacon movement in a distributed wireless network that can reduce the size and secure a large data interval.

A method for dynamic beacon movement in a decentralized wireless network based on wireless mobile ad-hoc networks according to the present invention for achieving the above object is, among the beacon section of the superframe (superframe) Selecting any one of the preceding free slots that are not used and the preceding beacon slot, making a protection request of the selected preceding free slot in a beacon group, and receiving a response to the protection request. And according to the response, the device moves and broadcasts a beacon to the selected preceding free slot.

Preferably, the network is a Wide Wide Band Wireless Personal Area Networks.

Advantageously, said response is made by a neighboring device in said beacon group that received said protection request.

Preferably, the step of selecting the slot, the step of selecting the slot, receiving the beacons of the neighboring devices, receiving beacon section occupancy information included in the beacon and confirming the beacon section occupancy information Checking the occupation state of the beacon interval slot by the neighboring devices and selecting the arbitrary preceding free slot.

Preferably, the beacon section occupancy information is beacon section occupancy information provided by a neighboring device that broadcasts the beacon, and is a slot number that is beaconed with a device currently beaconed in a beacon group of the neighboring device. It includes.

Preferably, the selection of any of the preceding free slots may select the most preceding slot in the beacon section among the preceding free slots.

Preferably, the protection request is made by broadcasting the beacon interval occupation information further including its information and the number of the selected free slot to the neighboring devices through the beacon.

Preferably, the response includes beacon interval occupancy information including its own information, the number of the current beacon slot and the number of the selected preceding free slot.

Preferably, the response is that if the neighbor device receives a protection request for the same slot as the selected predecessor free slot together from another device, the device with the higher slot number that the protection requesting device is currently beaconing. Protection requests are made.

Further, the response includes beacon section occupancy information including information of the device making the protection request determined to respond, the number of the selected preceding free slot, and the number of the current beacon slot of the device making the protection request determined to respond. It is desirable to do through.

Advantageously, the response is a device having the highest ID among a series of identifiers of the protected device request if the neighboring device together received a protection request for the same slot as the selected preceding free slot from another device. And a protection request of any of the devices with the lowest ID.

Advantageously, the step of broadcasting moves to the selected preceding free slot only when the response is received from all neighboring devices that have received the protection request.

Also, a system including at least one device and capable of dynamic beacon movement in a decentralized wireless network based on a wireless mobile ad hoc network, is a slot of any preceding free slot that is not used among the beacon sections of a superframe and is a preceding beacon slot. Select to include in the beacon group of the protection request of the selected predecessor free slot to move to the selected predecessor free slot and includes at least one response device for responding to the protection request of the device.

Preferably, the network is a broadband personal wireless network.

Advantageously, the requesting device receives the beacons of the response devices and receives the beacon section occupancy information included in the beacon to confirm the occupation state of the beacon section slot by the response devices. Select the slot.

Preferably, the beacon section occupancy information is beacon section occupancy information provided by a response device broadcasting the beacon, and is a slot number that is beaconed with a device currently beaconed in the beacon group of the response device. It includes.

Advantageously, the requesting device selects the first slot in the beacon section among the preceding free slots in the selection of the arbitrary free slots.

In addition, the protection request, the requesting device is preferably made by broadcasting the beacon section occupancy information further including its information and the number of the selected free slot to the at least one response device via the beacon.

Furthermore, the response may be performed through beacon section occupancy information including the information of the request device, the number of the selected preceding free slots, and the request device including the current beacon slot number.

Preferably, if the response device receives a protection request for the same slot as the selected predecessor free slot from another device besides the request device, the slot number of the protection request device that is currently beaconed is high. Determine to respond to the protection request of the device.

Further, the response includes beacon section occupancy information including information of the device making the protection request determined to respond, the number of the selected preceding free slot, and the number of the current beacon slot of the device making the protection request determined to respond. It is desirable to do through.

Preferably, the response device has the highest ID among a series of identifiers of the requested devices if the protection device has received a protection request for the same slot as the selected preceding free slot from another device besides the request device. It may respond to the protection request of either the device or the device with the lowest ID.

Preferably, the requesting device can move to the selected preceding free slot only when receiving the response from all of the at least one response device receiving the protection request.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating a network including a system for dynamic beacon movement in a distributed wireless network of the present invention.

The wireless network of FIG. 3 is a non-centralized Personal Area Network (WPAN) based on wireless mobile ad-hoc networks and without any central coordinator.

The network of FIG. 3 is preferably a wideband (UWB) personal wireless network.

Referring to FIG. 3, device A, device B, device C and device D are included in a network. The circle drawn around each device represents the range in which the beacon of the device is received.

Device A is a 'request device' to move the beacon according to the beacon movement method of the present invention, device B and device C is a 'response device' which is a neighbor device of the device A, beacons that can receive the beacon of the device A Belongs to the group. Device D forms another beacon group containing device C. Unlike device C, device D cannot receive the beacon of device A.

Devices B to D may move beacons similarly to device A. However, hereinafter, the description will be focused on the beacon movement in the device A for convenience of description.

Device A of the present invention performs a new media access control. The new media access control includes a method for protecting a beacon slot where device A wants to move the beacon, a method for detecting a collision that may occur in the newly selected beacon slot for the beacon movement, and improved beacon segment occupancy information (BPOIE). It includes the use of the Beacon Period Occupancy Information Element.

The movement of the beacon is to reduce the size of the beacon period (BP) and to thereby secure a larger data interval necessary for data transmission, and moves the beacon to an unused slot without a collision caused by the movement by the device A. It is possible. This is possible by the device A of the present invention protecting the slot to which the beacon is to move.

Preferably, the beacon moves to a free lower slot having a preceding position in time, even among unused beacon slots. Therefore, it is preferable that the leading free slot has a small slot number.

Hereinafter, first, the beacon section occupation information BPOIE is demonstrated.

4 is a view for explaining the beacon section occupation information of the present invention.

In FIG. 4, (a) shows a beacon section of a superframe of a beacon group of device A, and (a-1) and (a-2) are beacon section occupation information broadcasted by device A. FIG.

3 and 4 (a), in the beacon group centering on device A, device C occupies slot 0 of the beacon section, device B is slot 2, and device A is slot 5 Occupies. At this time, the device A wants to move to slot 1 of the preceding free slots 1, 3, and 4.

The beacon interval occupation information has a form of a beacon slot number that the device is beaconing and a DEVID (Device Identifier) of the device, and includes information about a state where the beacon slot is occupied in the beacon period.

The general beacon interval occupation information includes beacon slot occupation information of a neighboring device of a device sending a beacon. Therefore, if the device A does not move the beacon, the beacon section occupation information sent by the device A is as shown in (a-1). That is, it includes the DEVID of device C (here 'C') and the slot number 0, and includes the DEVID and slot number 2 of the device B.

However, the device to move the beacon includes the information about the movement of the beacon using the improved beacon section occupancy information. The beacon segment occupation information includes a DEVID of the device A to which the beacon is to be moved, and a slot number selected for movement. Therefore, when the device A intends to move the beacon to the slot 1, the beacon section occupancy information sent by the device A includes the DEVID of the device A (here 'A') and the slot number 1 to be moved.

The improved beacon interval occupation information has an entry for device A which sends the special beacon interval occupation information. The beacon segment occupation information is a device A protection request for all neighboring devices which have confirmed this beacon segment occupation information.

The neighboring devices B to F receiving the beacon may distinguish general beacon interval occupation information and improved beacon interval occupation information. This is because the improved beacon interval occupation information includes the DEVID of the device A sent. As mentioned earlier, this improved beacon occupancy information is considered a protection request by a device wishing to protect that beacon slot.

The beacon interval occupation information broadcast in the next superframe by the neighbor device includes the DEVID of the device A to which the beacon is to be moved twice. The first is for the slot number that device A is currently beaconing, and the second is for the slot number to which device A wants to move the beacon with.

4B illustrates a beacon period of the superframe of the beacon group of the device C. FIG. If device A does not move the beacon, device C will send general beacon section occupancy information (b-1). However, if device A will move the beacon, and device C receives the improved beacon interval occupation information from device A, device C sends the improved beacon interval occupation information (b-2). Therefore, it includes the DEVID of device A twice. The device D receives the beacon interval occupation information broadcast by the device C, and the device D knows that the device A has occupied slot 1 for the beacon movement.

5 is a flowchart provided to explain a beacon movement method of a system for dynamic beacon movement in a decentralized wireless network according to the present invention. Hereinafter, the beacon movement method of the device of the present invention will be described with reference to FIGS.

In order to protect the selected beacon slot 1 for the beacon movement, the device A provides additional information of the selected beacon slot 1 through the beacon section occupancy information a-2. By protecting the selected slot, the selected slot is protected by the neighboring devices B, C of the device A.

Furthermore, the slots must be protected from devices belonging to the beacon groups of neighbor devices B and C that are not in the beacon group of device A. This is also referred to as the 'neighbourhood of two hops' and device D.

Device A receives beacons from the neighboring devices in the beacon section (S501). Then, by checking the occupation information of the neighboring devices through their beacon interval occupation information, it is determined whether there is a preceding free slot available to the device A in the beacon interval (S503). Then, select one leading free slot among the available free slots for beacon movement. Device A may move the beacon to any other preceding free slot. In FIG. 4A, device A is selected to move to slot 1 from among available free slots 1, 3, and 4 (S505).

In step S505, after selecting one leading free slot and before moving the beacon to the selected slot, the device A is a beacon interval occupancy information (a- including the slot number of the selected free slot and additional information of its own DEVID) Through 1), the protection request for the selected slot is made by advertising the selected preceding free slot (S507).

When the neighboring devices B and C receive the improved beacon interval occupying information having the DEVID of the device A and the information of the selected leading free slot from the device A, it is determined that the device A is in the protection request of the selected leading free slot.

If there is a protection request, the neighboring devices B and C of the device A must protect the selected slots and the slots can be protected by neighboring devices in the 2-hop region.

If neighbor devices B and C may receive protection requests for some slots from more than one device. In this case, the neighbor device may protect the corresponding slot only for one of the devices (S509).

If a device receives a protection request to protect a free slot for device A wishing to move the beacon, the device responds to device A by adding the selected slot number and the received DEVID entry to its beacon section occupancy information. Should be sent (S511).

In the next superframe, device A checks if there is a response from all neighboring devices. Therefore, the device A determines whether there is an entry having the beacon slot selected by the user and the DEVID in the beacon section occupancy information of the beacons received from the neighbor devices B and C during the next superframe (S513).

In step S513, when the device A wishing to move the beacon receives the entry of the slot requested to be protected in the beacon section occupancy information of all neighbor devices B and C, the device A accepts the beacon movement to the selected slot. I judge it. Device A may broadcast its beacon through the selected beacon slot from the next superframe. The original slot will remain as a free slot (S515).

In step S513, if the device A to move the beacon does not receive the entry of the protected slot as expected in the beacon section occupancy information from all neighboring devices, devices B and C, the device A to the protected slot It will not move and will continue beaconing in the original slot. This situation may occur when another device D or the like is using or intends to use the selected slot (S517).

Furthermore, device A removes the protection of the corresponding slot to be moved. The next beacon interval occupancy information sent by device A does not include its DEVID for the same leading free slot. However, device A may select a new leading free slot and perform the procedure again (S519).

The present invention provides the following method for detecting an expected collision in a selected slot for the movement of a beacon slot.

In case two or more devices select the same predecessor free slot for their beacon movement, a device capable of identifying all of those devices can detect possible collisions by checking the beacon interval occupancy information.

6 is a flowchart provided to explain a collision prevention method according to beacon movement of a system for dynamic beacon movement in a decentralized wireless network according to the present invention.

In step S509 of FIG. 5, if the neighbor device C receives a protection request for some slot from two or more devices, the device may protect the slot only for one of those devices.

The neighbor device may receive two or more protection requests (S601).

In this case, the neighboring device must select one of two or more protection requests. Preferably, the neighbor device protects the device with the higher slot number that the device requesting protection is currently beaconing. This is because it is more effective to reduce the length of the dynamic beacon section.

For example, in the case of FIG. 4B, consider the case where device C receives the protection request of slot 1 from device A and device D. FIG. Since device A is currently beaconing in slot 5 and device D is currently beaconing in slot 6, device C will protect the beacon movement of device D, which has a higher number of slots.

Furthermore, a device with a lower or higher DEVID may be selected for protection (S603).

If the neighbor device receives only one protection request, it is acceptable to the protection request (S605).

According to an embodiment of the present invention, it is possible for a device to move a beacon to select and protect at least one free slot.

According to the present invention, devices can move their slots into leading free slots and reduce the size of the beacon section.

In addition, collisions can be prevented by detecting collisions that may occur while devices move their beacons and avoiding the movement of the beacons.                     

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (23)

In the method for dynamic beacon movement in a wireless network, Selecting any slot among the preceding free slots that is not used among the beacon sections of the superframe and is a preceding beacon slot; Making a protection request of the selected preceding free slot in a beacon group; And Receiving a response to the protection request, and according to the response, the device moving and broadcasting a beacon to the selected predecessor free slot; and a method for dynamic beacon movement in a decentralized wireless network, comprising: . The method of claim 1, The wireless network is a wide-band ad-hoc-based distributed wireless Personal Area Networks (Wideband), characterized in that for dynamic beacon movement in a distributed wireless network. The method of claim 1, And wherein the response is made by a neighboring device in the beacon group that received the protection request. The method of claim 3, wherein Selecting the slots, Receiving beacons of the neighboring devices and receiving beacon section occupation information included in the beacons; And Confirming the occupation status of the beacon interval slot by the neighboring devices by checking the beacon interval occupation information and selecting the arbitrary free slot; dynamic beacon movement in a decentralized wireless network, comprising: Way for you. The method of claim 4, wherein The beacon section occupancy information is beacon section occupancy information provided by a neighboring device that broadcasts the beacon and includes a slot number that is beaconed with a device currently beaconed in the beacon group of the neighboring device. A method for dynamic beacon movement in a distributed wireless network characterized by the above-mentioned. The method of claim 4, wherein And wherein the selection of any preceding free slot selects the most preceding slot within the beacon section among the preceding free slots. The method of claim 3, wherein The protection request is a dynamic beacon movement in a decentralized wireless network, characterized in that the beacon interval occupancy information further comprising its information and the number of the selected free slot to be broadcast to the neighboring devices via a beacon. Way. The method of claim 7, wherein And the response includes beacon interval occupancy information including its information, the number of the current beacon slot and the number of the selected leading free slot. The method of claim 3, wherein The response is that if the neighbor device receives a protection request for the same slot as the selected preceding free slot from another device, the protection request of the device with the higher slot number that the device which is requested to be protected among the protection requests is currently beaconed. And a method for dynamic beacon movement in a distributed wireless network. The method of claim 9, The response includes beacon interval occupancy information including information of the device requesting the protection request determined to respond, the number of the selected preceding free slot, and the number of the current beacon slot of the device requesting the protection request determined to respond. A method for dynamic beacon movement in a distributed wireless network, characterized in that. The method of claim 3, wherein The response is that the device having the highest ID and the lowest ID among a series of identifiers of the requested devices if the neighboring device together received a protection request for the same slot as the selected preceding free slot from another device. And responding to a protection request of any one of the devices having a network. The method of claim 3, wherein And the broadcasting step moves to the selected predecessor free slot only when the response is received from all neighboring devices that have received the protection request. A system including at least one device and capable of dynamic beacon movement in a distributed wireless network based on a wireless mobile ad hoc network, the system comprising: Selecting any slot among the preceding free slots, which are not used among the beacon sections of the superframe, makes a request for protection of the selected preceding free slots in its beacon group, and moves to and broadcasts the selected preceding free slots. Request device; And And at least one response device responsive to the protection request of the device. The method of claim 13, The network is a dynamic beacon mobile system in a distributed wireless network, characterized in that the broadband personal wireless network. The method of claim 13, The requesting device receives the beacons of the response devices and receives the beacon section occupancy information included in the beacon to check the occupation status of the beacon section slot by the response devices to select the arbitrary free slot. A system capable of dynamic beacon movement in a distributed wireless network, characterized in that. The method of claim 15, The beacon section occupancy information is beacon section occupancy information provided by the response device broadcasting the beacon and includes a slot number that is beaconed with a device currently beaconed in the beacon group of the response device. A system capable of moving dynamic beacons in a distributed wireless network. The method of claim 15, The requesting device is a dynamic beacon mobile system in a decentralized wireless network, characterized in that in the selection of any of the preceding free slots, selects the leading slot in the beacon section of the preceding free slots. The method of claim 13, The protection request is a distributed wireless network, characterized in that the requesting device broadcasts the beacon section occupancy information, which further includes its information and the number of the selected free slot, to the at least one response device via a beacon. System capable of dynamic beacon movement in. The method of claim 18, The response may include dynamic beacon movement in a decentralized wireless network, wherein the request device includes information on the requesting device, the number of the selected preceding free slots, and the requesting device including beacon interval occupying information including a number of a current beacon slot. System available. The method of claim 13, If the response device receives a protection request for the same slot as the selected predecessor free slot from another device other than the request device, the protection request of the device with the higher slot number that is currently beaconed by the device requesting protection among the protection requests. A system capable of dynamic beacon movement in a distributed wireless network, characterized in that it determines to respond to. The method of claim 20, The response includes beacon interval occupancy information including information of the device requesting the protection request determined to respond, the number of the selected preceding free slot, and the number of the current beacon slot of the device requesting the protection request determined to respond. A system capable of dynamic beacon movement in a distributed wireless network, characterized in that. The method of claim 13, If the response device receives a protection request for the same slot as the selected predecessor free slot from another device besides the request device, the device having the highest ID and the lowest ID among a series of IDs of the devices for which protection has been requested. A system capable of dynamic beacon mobility in a distributed wireless network, characterized in that it responds to a protection request from any one of the devices. The method of claim 13, And the requesting device moves to the selected predecessor free slot only when receiving the response from all of the at least one response device that has received the protection request.

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