A method for RF sensing with smart traffic management

Abstract

A method (500) for controlling a wireless system (100) comprising a group of nodes (200a, 200b, 200c, 200d) to perform radio frequency, RF, based motion detection; the method (500) comprising each node out of the group of nodes (200a, 200b, 200c, 200d): sending (S501) sensing messages on a regular basis; detecting (S502) sensing messages from one or more neighboring nodes (200a, 200b, 200c, 200d); monitoring (S503) at least one characteristic of detected sensing messages; the method (500) further comprising: detecting (S504) a motion by a first node (200a) out of the group of nodes (200a, 200b, 200c, 200d) based on a change of the at least one characteristic; sending (S505) a notification message by the first node (200a) upon detection of the motion; initializing (S506) a hold-off timer by each node out of the group of nodes (200a, 200b, 200c, 200d) upon sending or receiving the notification message; suspending (S507) sending sensing messages on a regular basis during the hold-off timer by each node out of the group of nodes (200a, 200b, 200c, 200d); resuming (S508) sending sensing messages on a regular basis by each node out of the group of nodes (200a, 200b, 200c, 200d) after the hold-off timer.

Description

[0001] A METHOD FOR RF SENSING WITH SMART TRAFFIC MANAGEMENT

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the field of a radio frequency based sensing system. More particularly, various methods, apparatus, and systems are disclosed herein related to traffic management for improved sensing and communication performance.

[0004] BACKGROUND OF THE INVENTION

[0005] Radio frequency (RF) based sensing is a technique widely used for motion detection, which involves one or more transmitters arranged for transmitting RF signals on a regular basis, such as according to a certain transmission frequency, and one or more receivers for receiving the RF signals. These RF signals, which may also be used for data communication, when passing through a sensing volume, are affected by presence / movement of a person within the sensing volume. By monitoring such variations of RF signals, it is possible to infer presence or motion of the person. RF based sensing may also be extended to other applications such as location detection, fall detection, gesture detection, or vital signs detection, which are also based on monitoring how RF signals are affected in the sensing volume.

[0006] The processing of the RF signals for presence or motion detection may be either performed locally e.g., at the receiving node, or it can be performed externally at an external device. For external processing, a collector node is generally used to collect RF signals and transmit it to the external device. With the external processing approach, it is necessary to commission different roles for the nodes in the system, which leads to additional commissioning work for an installer, and when the nodes for performing the various RF sensing functions are not selected properly some motions may even not be detected at all. Furthermore, the traffic resulted from collecting RF signals at the collector node and forwarding the RF signals from the collector node to the external device also adds to the traffic load of the network, especially when the network is used also for data communication. Therefore, it is considered to be beneficial to implement RF sensing in a distributed manner, such that each node in a particular sensing group sends RF sensing messages and itself listens to all RF messages coming from its own neighbor nodes in the same sensing group for presence or motion detection.

[0007] The RF sensing system may make use of existing wireless communication technologies. For example, ZigBee, Thread and Bluetooth Mesh are commonly used technologies targeted at loT applications such as lighting and building automation. They provide a low latency, low-rate service that enables messages to be passed between, for example, a light switch and one or more luminaires. To enable messages to be routed correctly, each node on the wireless network is assigned a local network unicast address and may be addressed either directly as an individual node or, via a group address, as a member of a group. Once configured, such networks are typically expected to operate autonomously.

[0008] US2014257572A1 relates to a controllable receptacle that comprises at least one switch, a motion sensor for sensing motion proximate to the controllable receptacle, a transceiver, and a controller operative to determine an association of the controllable receptacle with a motion group, wherein the motion group comprises a plurality of devices, wherein the controller communicates with at least one of the plurality of devices, determines that the controllable receptacle is to be activated based on the motion sensor sensing motion or a motion sensor of a device of the motion group sensing motion, and closes the at least one switch when determining the controllable receptacle is to be activated.

[0009] SUMMARY OF THE INVENTION

[0010] Since a RF sensing system may be overlayed with a wireless communication system, transmission RF sensing signals or RF sensing messages on a regular basis may result in contention or heavy traffic load to the wireless network. It is recognized by the inventor that it is beneficial to implement a smart traffic management mechanism in an RF sensing system to alleviate the impact of RF sensing messages on the traffic load. More particularly, the goal of this invention is achieved by a method as claimed in claim 1, by a node as claimed in claim 12, by a wireless system as claimed in claim 13, and by a computer program as claimed in claim 15.

[0011] In accordance with a first aspect of the invention a method is provided. A method for controlling a wireless system comprising a group of nodes to perform radio frequency, RF, based motion detection; the method comprising each node out of the group of nodes: sending sensing messages on a regular basis; detecting sensing messages from one or more neighboring nodes; monitoring at least one characteristic of detected sensing messages; the method further comprising: detecting a motion by a first node out of the group of nodes based on a change of the at least one characteristic; sending a notification message by the first node upon detection of the motion; initializing a hold-off timer by each node out of the group of nodes upon sending and upon receiving the notification message; suspending sending sensing messages on a regular basis during the hold-off timer by each node out of the group of nodes; resuming sending sensing messages on a regular basis by each node out of the group of nodes after the hold-off timer.

[0012] The group of nodes may belong to a same sensing group, while there is another group of nodes belong to a different sensing group located in the proximity. The division of different sensing groups may be based on locations, such as different groups for nodes located in different rooms or on different floors, different control functions, or different capabilities of nodes. Each node of the group may ignore sensing messages received from nodes belong to a different sensing group. The motion detection may be used for building automation to control sensors and actuators integrated in or co-located with the one or more nodes.

[0013] The sensing messages may be transmitted by each node via broadcasting. Alternatively, the sensing messages may also be transmitted by each node of the group via multicasting to other nodes in the same group, such that the sensing messages comprise a group address for a particular sensing group.

[0014] To detect the presence or motion in the sensing area timely, the sensing messages are transmitted by each node on a regular basis. The group of nodes belonging to a same sensing group may use a same duty cycle or transmission frequency for sending sensing messages repeatedly. It may also be an option that each node in the same sensing group also adopts a different duty cycle or transmission frequency for sending sensing messages.

[0015] Motion detection may be related to a binary presence indication, or a more advance detection regarding a type of the motion, such as gesture detection, activity detection, vital sign detection, etc. The type of the motion may be detected by classification, or a pattern recognition based on a comparison against an established baseline.

[0016] The motion or presence detection, such as communicated via the notification message, may be used to trigger a control command to one or more electronic devices connected to or controlled by each node of the group of nodes. It may also be possible that each node out of the group is integrated in an electronic device. The electronic device may be a lighting device, a wall switch, a bridge, a speaker, a television, a thermostat, a wireless sensor, a power outlet plug, a doorbell, a smart home assistant device, and / or a smart home appliance. For example, the control command may be related to a turn on or power on command to the one or more electronic devices. The control command may be related to changing a setting or an operation mode of the one or more electronic devices.

[0017] The motion according to the present invention may comprise major motions, such as movement of a person, arms, legs, but also micro motions, such as fine movements of fingers. The motion detection be related to presence sensing of a people in the detection area, which may also be used to identify and classify the motion, such as for gesture detection, fall detection, sleep monitoring, vital sign detection by means of heart rate detection, breathing detection etc.

[0018] The group of nodes may follow a wireless communication standard for transmitting the sensing messages. The wireless communication standard may be related to a standard of Zigbee, Thread, or Bluetooth Low Energy. For example, the sensing messages may be Interpan messages according to a Zigbee standard. Alternatively, the sensing messages may be related to Bluetooth beacons according to a Bluetooth Low Energy standard.

[0019] The group of nodes may be used to carry out another functionality in addition to RF sensing. For example, the wireless system may also be used for data communication, such as following the same wireless communication standard for transmitting the sensing messages, and then the traffic for data communication and the traffic for RF sensing contend for the same wireless medium. It is thus proposed in the present invention to apply a smart traffic management strategy on the transmission of sensing messages based on a detection status to reduce the impact of the traffic resulted from RF sensing on data communication. It is further disclosed that for the first node upon detection of the motion or transmission of the notification message and for other nodes in the group upon receiving the notification message, a hold-off timer is initialized by each node individually.

[0020] Since the group of nodes are informed about the motion or presence detection by the notification message, the control, derived from the motion or presence detection, on one or more electronic devices connected to or controlled by each node of the group of nodes will take effect for a certain period of time. It is not necessary to continue the regular transmission of sensing messages right after the communication of the notification message. Hence, it is proposed that the regular transmission of RF sensing messages is suspended for each node during the hold-off timer and is resumed after the expiration of the hold-off timer. The duration of the hold-off timer may be the same or different for the nodes belong to the same group.

[0021] Beneficially, the method further comprising the steps of: initializing a hold timer by the first node upon detection of the motion; releasing the hold timer by the first node when the first node receives a further notification message from another node out of the group of nodes during the hold timer; restarting the hold timer by the first node upon detection of a further motion by the first node during the hold timer; sending a clearance message by the first node upon expiration of the hold timer with no further notification message received by the first node during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0022] The hold timer may be related to the duration for which a control command that is triggered either by the motion detection or the notification message will take effect.

[0023] During the hold timer, if there is a new motion event detected or a further notification message generated, the new motion event or the further notification message will restart the hold timer.

[0024] In a first setup, the hold timer may be maintained by the first node alone. If there is no new motion event detected by the first node and no further notification message received form another node during the hold timer, upon expiration of the hold timer the first node is then responsible to send a clearance message to the other nodes of the group. The clearance message is used to inform the group of nodes about the expiry of the motion or presence detection, such that any control command or control action triggered by the notification message will be released.

[0025] If the first node detects a further motion during the hold timer, it will restart the hold timer, such that the control related to the motion detection will be extended. If the first node receives a further notification message from another node of the group, the first node will simply release the hold timer, and then the hold timer will be maintained by the other node that sent the further notification message.

[0026] Since the hold timer represents the valid duration of a motion or presence detection, the hold timer is longer than the hold-off timer. In practice, the hold-off timer may be significantly smaller than the hold timer to ensure a timely update of the motion or presence detection. Advantageously, the method further comprising the steps of: initializing a hold timer by each node out of the group of nodes upon sending or receiving the notification message; restarting the hold timer by each node out of the group of nodes upon sending or receiving a further notification message; releasing the hold timer by each node out of the group of nodes upon expiration of the hold timer without sending or receiving any further notification message during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0027] The hold timer may be related to the duration for which a control command that is triggered either by the motion detection or the notification message will take effect. In the second setup, a hold timer is maintained by each node locally, such that for the first node upon sending the notification message and for the other nodes of the same group upon receiving the notification message, a hold timer will be initialized by each node individually.

[0028] If there is no further notification message received during the hold timer, each node will release the hold timer individually upon expiration of the hold timer. In contrast, if there is a further notification message received during the hold timer, each node will release the on-going hold timer and initialize a new hold timer. If there is a further motion detected during the hold timer, such as by a node detected by itself or upon receiving a further notification message, the hold timer will be restarted, and thus the hold timer is extended.

[0029] For example, if continuous presence or motion detection is confirmed in the sensing or detection area by at least one of the node out of the group of nodes, the hold timer will be re-initialized every time upon a new notification message, and hence the control action will be extended accordingly.

[0030] Preferably, the duration of the hold timer is either a predetermined value defined for the group of nodes, or a configurable value to be determined for the group of nodes according to one or more parameters out of a type of the motion detected, a user input, a location of the motion detected, a time of the day, an occupancy level of the room, and a characteristic or type of electronic devices controlled by the group of nodes based on motion detection.

[0031] A type of the motion may be related to a classification of the motion, such as gesture, respiration, heartbeat, minor motion of fingers. A type of the motion may also be related to an activity of the person, such as computer work or sports. For computer work, during which the person hardly moves, a longer-duration hold timer may be used. On the other hand, if the room is used for workout or yoga, a shorter hold timer may be employed.

[0032] The location of the motion detected may also be relevant to the determination of the hold time. For instance, in a hallway it is preferable to adopt a shorter hold timer as people move through this space fast and typically with large body movement. On the other hand, for a location where concentrated computer work is performed (e.g. the CAD workplaces), a long hold timer may be used as the user may stay static for a while. Similarly, in a parking garage a longer hold time may be employed, as switching off the light while someone is still present may result in an unfriendly user experience.

[0033] The hold time may also vary depending on the time of the day. For example, when it is dark outside, it may be beneficial to extend the hold time, while during day when daylight shines through the window, a shorter hold time may be used.

[0034] An occupancy level of the room may indicate the number of people in the room. If multiple people are detected in the same room, the hold time may be increased accordingly to avoid the impact of a miss detection (detecting the room as empty while it is occupied) on multiple people.

[0035] The duration of the hold timer may be the same or different for the nodes of the same group. The duration of the hold timer may be predefined or preconfigured, which may also be configurable or adjusted adaptively (e.g., based on the motion detection).

[0036] In one example, the method further comprising the step of: refraining each of the group of nodes from sending another notification message during the hold-off timer.

[0037] In one setup, the notification message is sent as a multicast message to the group of nodes.

[0038] The group of nodes may be within a direct communication range of each other.

[0039] Advantageously, the duration of the hold-off timer is either a predetermined value defined for the group of nodes, or a configurable value to be determined for the group of nodes or by each node of the group of nodes individually according to one or more parameters out of real-time data traffic load, a latency requirement, a type of the motion detected, a user input, a location of the detection, a time of the day.

[0040] The duration of the hold-off timer may be predefined or preconfigured, which may be the same or different for the nodes belonging to the same sensing group. The duration of the hold-off timer may also be configurable or adjusted adaptively. For example, when the traffic load for data communication is heavy, it may be advantageous to extend the hold-off timer to further suppress the sensing traffic. In another example, the hold-off timer may be extended when a slow motion is detected, whereas when a fast motion is detected, it may be better to maintain or even reduce the duration of the hold-off timer.

[0041] In one example, the at least one characteristic is related to a Received Signal Strength Indication, RSSI, a Channel Impulse Response, CIR, a Channel State Information, CSI, parameter of detected sensing messages, a miss message rate, or another received signal quality parameter.

[0042] The group of nodes may be configured to keep track of the at least one characteristic by observing a moving average of the RSSI, CIR, or CSI of the detected sensing messages.

[0043] Motion detection may be represented by a binary presence indication. In a more advance version, motion detection may also derive a type of the motion detected, such as according to gesture detection, activity detection, or vital sign detection such as breathing or heartbeat, etc. The type of the motion may be detected by classification, or a pattern recognition based on a comparison against an established baseline. For example, a pattern may be recognized by monitoring and tracking a change of the at least one characteristic of the received sensing messages.

[0044] Beneficially, the method comprising each node out of the group of nodes monitoring the at least one characteristic of detected sensing messages for each sending node of the sensing messages individually.

[0045] Each pair of a sending node and a receiving node distinguishes a signal propagation path for the sensing messages from the sending node to the receiving node. By monitoring the received sensing messages from each sending node individually, the receiving node may derive more detailed location information regarding a motion or presence detection.

[0046] In one example, the motion is detected by the first node when a variance as compared to a running average of the at least one characteristic is larger than a predetermined threshold.

[0047] As an example, each node may calculate and keep track of a running mean and variance value for the RSSI strengths of sensing messages that it receives from each of the other nodes in the group and compares this to a threshold value. If one of the variance values exceeds the threshold value, the receiving node will send out a notification message to announce the motion detection to the entire group. Advantageously, the notification message comprising one or more parameters related to a type of the motion detected, a confidence level of the detection, an address information of a source node of a RF sensing message that triggers the notification message, a location of the source node.

[0048] The one or more parameters comprised in the notification message may be used by each node to further customize the control command resulted from the motion or presence detection.

[0049] For example, if the source node of a RF sensing message that triggers the notification message is located next to an HVAC device, which possibly creates EMI disturbance to RF sensing, a lower confidence level may be derived for the detection.

[0050] In accordance with a second aspect of the invention a node is provided. A node out of a group of nodes comprised in a wireless system for radio frequency, RF, based motion detection; the node comprising: a transmitter configured to send sensing messages on a regular basis; a receiver configured to detect sensing messages from one or more neighboring nodes; and a controller configured to: monitor at least one characteristic of detected sensing messages; detect a motion based on a change of the at least one characteristic; control the transmitter to send a notification message upon detection of the motion; initialize a hold-off timer upon sending the notification message and upon receiving a notification message from another node out of the group of nodes; control the transmitter to suspend sending sensing messages on a regular basis during the hold-off timer; control the transmitter to resume sending sensing messages on a regular basis after the hold- off timer.

[0051] The motion detection may be used for building automation to control sensors and actuators integrated in or co-located with the one or more nodes.

[0052] The node may be integrated in an electronic device, and the electronic device is controlled via RF based motion or presence detection. It may also be possible that the node is connected to or attached to an electronic device to control the electronic device via motion or presence detection. The electronic device may be a lighting device, a wall switch, a bridge, a speaker, a television, a thermostat, a wireless sensor, a power outlet plug, a doorbell, a smart home assistant device, and / or a smart home appliance. The node may be further configured to carry out data communication in addition to RF sensing.

[0053] The node may follow a wireless communication standard for sending the sensing messages. The wireless communication standard may be related to a standard of Zigbee, Thread, or Bluetooth Low Energy. For example, the sensing messages may be Interpan messages according to a Zigbee standard. Alternatively, the sensing messages may be related to Bluetooth beacons according to a Bluetooth Low Energy standard.

[0054] The controller of the node may be further configured to: initialize a hold timer upon detection of the motion; release the hold timer when the node receives a further notification message from another node out of the group of nodes during the hold timer; restart the hold timer upon detection of a further motion during the hold timer; control the transmitter to send a clearance message upon expiration of the hold timer with no further notification message received during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0055] In this option, the hold timer is maintained by the node that detected the motion or presence. Alternatively, it is also possible that each node of the group maintains the hold timer locally. And then, in the alternative option, the controller of the node may be further configured to: initialize a hold timer upon sending the notification message or receiving another notification message from another node of the group; restart the hold timer by each node out of the group of nodes upon sending or receiving a further notification message; releasing the hold timer by each node out of the group of nodes upon expiration of the hold timer without sending or receiving any further notification message during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0056] The hold timer is related to the duration for which a control command that is triggered either by the motion detection or the notification message will take effect. The duration of the hold timer may be predefined or preconfigured, which may be the same or different for the nodes belonging to the same sensing group. The duration of the hold timer may also be configurable or adjusted adaptively for each node or for the group of nodes, such as according to one or more parameters out of a type of the motion detected, a user input, and a characteristic or type of electronic devices controlled by the group of nodes based on motion detection.

[0057] In accordance with a third aspect of the invention a wireless system is provided. A wireless system configured to perform radio frequency, RF, based motion detection; the wireless system comprising a group of nodes according to claim 12; wherein each node out of the group of nodes are further configured to: initialize a hold-off timer upon receiving a notification message from another node out of the group of nodes; suspend sending sensing messages on a regular basis during the hold-off timer; resuming sending sensing messages on a regular basis after the hold-off timer. Beneficially, each node out of the group of nodes are integrated in or attached to a luminaire.

[0058] The wireless system is used for both RF sensing and lighting control. The communication within the wireless system is based on a Zigbee network, which is widely adopted in home automation and lighting control applications.

[0059] Beneficially, a control command generated from the motion detection is used for lighting control, such as to switch on / off a lamp or to change colour temperature of the lamp, etc.

[0060] The notification message may be used as a power-on control command. When the hold timer is maintained by a single node, such as the first node or the node that generates the latest motion detection, the clearance message may be used as a dim-down message in the lighting control scenario. In another smart home application, the clearance message may be used as a power-off control command. When the hold timer is maintained locally by each node individually, each lamp may dim down itself upon the expiration of this local hold timer.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In the drawings, like reference characters generally refer to the same parts throughout the different figures. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0063] Fig. 1 illustrates a wireless system comprising a group of nodes according to the present invention;

[0064] Fig. 2 illustrates a basic block diagram of a node; and

[0065] Fig. 3 shows a flow chart of a method according to the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0066] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0067] FIG. 1 illustrates a wireless system 100 comprising a group of nodes 200a, 200b, 200c, 200d according to the present invention. The wireless system 100 is configured to perform radio frequency, RF, based motion detection with the group of nodes. The group of nodes may belong to a same sensing group, while there is another group of nodes belong to a different sensing group located in the proximity. Hence, the wireless system 100 may comprise a plurality of sensing groups (not shown in the figure) with each sensing group carry out the motion detection either independently or collaboratively, and the division of different sensing groups may be based on locations, such as different groups for nodes located in different rooms or on different floors, different control functions, or different capabilities of nodes. Each node of the group may ignore sensing messages received from nodes belong to a different sensing group. The motion detection may be used for building automation to control sensors and actuators integrated in or co-located with the one or more nodes.

[0068] Each node out of the group may be integrated in, attached to, or connected to an electronic device to be controlled mainly or partially via motion detection. The electronic device may be a lighting device, a wall switch, a bridge, a speaker, a television, a thermostat, a wireless sensor, a power outlet plug, a doorbell, a smart home assistant device, and / or a smart home appliance. For example, the control command may be related to a turn on or power on command to the one or more electronic devices. The control command may be related to changing a setting or an operation mode of the one or more electronic devices.

[0069] With one or more nodes out of the group of nodes integrated in or attached to a luminaire, the wireless system may also be a lighting control system and is configured to carry out data communication in addition to RF sensing.

[0070] FIG. 2 illustrates a basic block diagram of a node 200. A node 200 out of a group of nodes 200a, 200b, 200c, 200d comprised in a wireless system 100 for radio frequency, RF, based motion detection. As a basic setup, the node comprises a transmitter 201, a receiver 202, and a controller 203. The transmitter 201 is configured to send sensing messages on a regular basis. The receiver 202 is configured to detect sensing messages from one or more neighboring nodes 200a, 200b, 200c, 200d. The controller 203 is configured to: monitor at least one characteristic of detected sensing messages; detect a motion based on a change of the at least one characteristic; control the transmitter 201 to send a notification message upon detection of the motion; initialize a hold-off timer upon sending the notification message; control the transmitter to suspend sending sensing messages on a regular basis during the hold-off timer; control the transmitter 201 to resume sending sensing messages on a regular basis after the hold-off timer.

[0071] In a busy environment with frequent motion detection, the smart traffic management interrupts the regular transmission of sensing messages by adopting the hold-off timer mechanism. This means that the sensing messages will only be present for a brief moment after the RF sensing is resumed, and if there is still activity the traffic stops as soon as one of the nodes detects that there is presence again (i.e., starting up a new hold-off timer again). In busy periods this means that a large fraction of the time the network becomes available again for other types of traffics, such as data collection, over-the-air updates, etc.

[0072] The controller 203 of the node 200 may be further configured to: initialize a hold timer upon detection of the motion; release the hold timer when the node 200 receives a further notification message from another node out of the group of nodes 200a, 200b, 200c, 200d during the hold timer; restart the hold timer upon detection of a further motion during the hold timer; control the transmitter 201 to send a clearance message upon expiration of the hold timer with no further notification message received during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0073] In this option, the hold timer is maintained by the node 200 that detected the motion or presence. Alternatively, it is also possible that each node 200a, 200b, 200c, 200d of the group maintains the hold timer locally. And then, in the alternative option, the controller 203 of the node 200 may be further configured to: initialize a hold timer upon sending the notification message or receiving another notification message from another node of the group; restart the hold timer by each node out of the group of nodes upon sending or receiving a further notification message; releasing the hold timer by each node out of the group of nodes upon expiration of the hold timer without sending or receiving any further notification message during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0074] The hold timer is related to the duration for which a control command that is triggered either by the motion detection or the notification message will take effect. The duration of the hold timer may be predefined or preconfigured, which may be the same or different for the nodes belonging to the same sensing group. The duration of the hold timer may also be configurable or adjusted adaptively for each node or for the group of nodes, such as according to one or more parameters out of a type of the motion detected, a user input, and a characteristic or type of electronic devices controlled by the group of nodes based on motion detection.

[0075] The duration of the hold timer is either a predetermined value defined for the group of nodes 200a, 200b, 200c, 200d, or a configurable value to be determined for the group of nodes 200a, 200b, 200c, 200d according to one or more parameters out of a type of the motion detected, a user input, and a characteristic or type of electronic devices controlled by the group of nodes 200a, 200b, 200c, 200d based on motion detection.

[0076] The duration of the hold-off timer is either a predetermined value defined for the group of nodes 200a, 200b, 200c, 200d, or a configurable value to be determined for the group of nodes 200a, 200b, 200c, 200d or by each node of the group of nodes 200a, 200b, 200c, 200d individually according to one or more parameters out of real-time data traffic load, a latency requirement, a type of the motion detected, a user input.

[0077] The at least one characteristic is related to a Received Signal Strength Indication, RSSI, a Channel Impulse Response, CIR, or a Channel State Information, CSI, parameter of detected sensing messages.

[0078] Preferably, each node out of the group of nodes 200a, 200b, 200c, 200d are configured to monitor the at least one characteristic of detected sensing messages for each sending node of the sensing messages individually.

[0079] As on example, the motion is detected by the first node 200a when a variance as compared to a running average of the at least one characteristic is larger than a predetermined threshold. The notification message may comprise one or more parameters related to a type of the motion detected, a confidence level of the detection, an address information of a source node of a RF sensing message that triggers the notification message.

[0080] FIG. 3 shows a flow chart of a method 500 according to the present invention.

[0081] A method 500 for controlling a wireless system 100 comprising a group of nodes 200a, 200b, 200c, 200d to perform radio frequency, RF, based motion detection; the method 500 comprising each node out of the group of nodes 200a, 200b, 200c, 200d: sending, in step S501, sensing messages on a regular basis; detecting, in step S502, sensing messages from one or more neighboring nodes 200a, 200b, 200c, 200d; monitoring, in step S503, at least one characteristic of detected sensing messages; the method 500 further comprising: detecting, in step S504, a motion by a first node 200a out of the group of nodes 200a, 200b, 200c, 200d based on a change of the at least one characteristic; sending, in step S505, a notification message by the first node 200a upon detection of the motion; initializing, in step S506, a hold-off timer by each node out of the group of nodes 200a, 200b, 200c, 200d upon sending or receiving the notification message; suspending, in step S507, sending sensing messages on a regular basis during the hold-off timer by each node out of the group of nodes 200a, 200b, 200c, 200d; resuming, in step S508, sending sensing messages on a regular basis by each node out of the group of nodes 200a, 200b, 200c, 200d after the hold-off timer.

[0082] The method 500 may further comprise the following steps when a hold timer is maintained by the first node alone: initializing a hold timer by the first node 200a upon detection of the motion; releasing the hold timer by the first node 200a when the first node 200a receives a further notification message from another node 200b, 200c, 200d out of the group of nodes 200a, 200b, 200c, 200d during the hold timer; restarting the hold timer by the first node 200a upon detection of a further motion by the first node 200a during the hold timer; sending a clearance message by the first node 200a upon expiration of the hold timer with no further notification message received by the first node 200a during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0083] The method 500 may further comprise the following steps when each node is arranged to maintain a hold timer locally: initializing a hold timer by each node out of the group of nodes 200a, 200b, 200c, 200d upon sending or receiving the notification message; restarting the hold timer by each node out of the group of nodes 200a, 200b, 200c, 200d upon sending or receiving a further notification message; releasing the hold timer by each node out of the group of nodes 200a, 200b, 200c, 200d upon expiration of the hold timer without sending or receiving any further notification message during the hold timer; wherein the hold timer is longer than the hold-off timer.

[0084] The method according to the present invention may be implemented on a computer as a computer implemented method, or in dedicated hardware, or in a combination of both.

Claims

CLAIMS:

1. A method (500) for controlling a wireless system (100) comprising a group of nodes (200a, 200b, 200c, 200d) to perform radio frequency, RF, based motion detection; the method (500) comprising each node out of the group of nodes (200a, 200b, 200c, 200d):- sending (S501) sensing messages on a regular basis;- detecting (S502) sensing messages from one or more neighboring nodes (200a, 200b, 200c, 200d);- monitoring (S503) at least one characteristic of detected sensing messages; the method (500) further comprising:- detecting (S504) a motion by a first node (200a) out of the group of nodes (200a, 200b, 200c, 200d) based on a change of the at least one characteristic;- sending (S505) a notification message by the first node (200a) upon detection of the motion;- initializing (S506) a hold-off timer by each node out of the group of nodes (200a, 200b, 200c, 200d) upon sending and upon receiving the notification message;- suspending (S507) sending sensing messages on a regular basis during the hold-off timer by each node out of the group of nodes (200a, 200b, 200c, 200d);- resuming (S508) sending sensing messages on a regular basis by each node out of the group of nodes (200a, 200b, 200c, 200d) after the hold-off timer.

2. The method (500) of claim 1 further comprising the steps of:- initializing a hold timer by the first node (200a) upon detection of the motion;- releasing the hold timer by the first node (200a) when the first node (200a) receives a further notification message from another node (200b, 200c, 200d) out of the group of nodes (200a, 200b, 200c, 200d) during the hold timer;- restarting the hold timer by the first node (200a) upon detection of a further motion by the first node (200a) during the hold timer;- sending a clearance message by the first node (200a) upon expiration of the hold timer with no further notification message received by the first node (200a) during the hold timer; wherein the hold timer is longer than the hold-off timer, and the hold timer defines the duration for which a control command that is triggered by the motion detection will take effect.

3. The method (500) of claim 1 further comprising the steps of- initializing a hold timer by each node out of the group of nodes (200a, 200b, 200c, 200d) upon sending or receiving the notification message;- restarting the hold timer by each node out of the group of nodes (200a, 200b, 200c, 200d) upon sending or receiving a further notification message;- releasing the hold timer by each node out of the group of nodes (200a, 200b, 200c, 200d) upon expiration of the hold timer without sending or receiving any further notification message during the hold timer; wherein the hold timer is longer than the hold-off timer, and the hold timer defines the duration for which a control command that is triggered by the notification message or the further notification message will take effect.

4. The method (500) of claim 2 or 3, wherein the duration of the hold timer is either a predetermined value defined for the group of nodes (200a, 200b, 200c, 200d), or a configurable value to be determined for the group of nodes (200a, 200b, 200c, 200d) according to one or more parameters out of a type of the motion detected, a user input, a location of the motion detected, a time of the day, an occupancy level of the room, and a characteristic or type of electronic devices controlled by the group of nodes (200a, 200b, 200c, 200d) based on motion detection.

5. The method (500) of any one of previous claims further comprising the step of- refraining each of the group of nodes (200a, 200b, 200c, 200d) from sending another notification message during the hold-off timer.

6. The method (500) of any one of previous claims, wherein the notification message is sent as a multicast message to the group of nodes (200a, 200b, 200c, 200d).

7. The method (500) of any one of previous claims, wherein the duration of the hold-off timer is either a predetermined value defined for the group of nodes (200a, 200b, 200c, 200d), or a configurable value to be determined for the group of nodes (200a, 200b, 200c, 200d) or by each node of the group of nodes (200a, 200b, 200c, 200d) individually according to one or more parameters out of real-time data traffic load, a latency requirement, a type of the motion detected, a user input, a location, a time of the day.

8. The method (500) of any one of previous claims, wherein the at least one characteristic is related to a Received Signal Strength Indication, RSSI, a Channel Impulse Response, CIR, a Channel State Information, CSI, parameter of detected sensing messages, a miss message rate, or another received signal quality parameter.

9. The method (500) of any one of previous claims comprising each node out of the group of nodes (200a, 200b, 200c, 200d) monitoring the at least one characteristic of detected sensing messages for each sending node of the sensing messages individually.

10. The method (500) of any one of previous claims, wherein the motion is detected by the first node (200a) when a variance as compared to a running average of the at least one characteristic is larger than a predetermined threshold.

11. The method (500) of any one of previous claims, wherein the notification message comprising one or more parameters related to a type of the motion detected, a confidence level of the detection, an address information of a source node of a RF sensing message that triggers the notification message, a location of the source node.

12. A node (200) out of a group of nodes (200a, 200b, 200c, 200d) comprised in a wireless system (100) for radio frequency, RF, based motion detection; the node comprising:- a transmitter (201) configured to send sensing messages on a regular basis;- a receiver (202) configured to detect sensing messages from one or more neighboring nodes (200a, 200b, 200c, 200d); and- a controller (203) configured to: o monitor at least one characteristic of detected sensing messages; o detect a motion based on a change of the at least one characteristic;o control the transmitter (201) to send a notification message upon detection of the motion; o initialize a hold-off timer upon sending the notification message and upon receiving a notification message from another node out of the group of nodes (200a, 200b, 200c, 200d); o control the transmitter to suspend sending sensing messages on a regular basis during the hold-off timer; o control the transmitter (201) to resume sending sensing messages on a regular basis after the hold-off timer.

13. A wireless system (100) configured to perform radio frequency, RF, based motion detection; the wireless system (100) comprising a group of nodes (200a, 200b, 200c, 200d) according to claim 12; wherein each node out of the group of nodes (200a, 200b, 200c, 200d) are further configured to:- initialize a hold-off timer upon receiving a notification message from another node out of the group of nodes (200a, 200b, 200c, 200d);- suspend sending sensing messages on a regular basis during the hold-off timer;- resuming sending sensing messages on a regular basis after the hold-off timer.

14. The wireless system (100) of claim 13, wherein each node out of the group of nodes (200a, 200b, 200c, 200d) are integrated in or attached to a luminaire.

15. A computer program product comprising instructions which, when the program is executed by a controller, cause the controller (203) to control a node according to claim 12 to carry out the steps of the method (500) of any one of claims 1-11.

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