Enhanced radio frequency sensing with automated node identity assignment

Abstract

The present invention relates to a method and apparatus for implementing radio frequency (RF) sensing in a distributed way among nodes of a wireless system, wherein every node in a particular node group sends RF sensing probing messages (e.g., in the form of a Zigbee Inter-PAN message) and listens itself to RF sensing probing messages coming from its own neighbor nodes in the same node group. Each node may calculate and keep track of a signal strength that it receives from each of the other nodes and compares this to a running average of the strength of preceding messages. If the difference exceeds a threshold value, the node will send out an RF sensing reporting message to the entire node group to indicate that presence has been detected. A unique node ID may be assigned to the nodes in an automated fashion (without requiring any commissioning effort), which determines the order in which the nodes send out their messages. To avoid that lots of nodes send their RF sensing reporting messages simultaneously, all nodes in a detection area that receive an RF sensing reporting message may start a hold-off timer for temporarily delaying own transmissions.

Description

[0001] ENHANCED RADIO FREQUENCY SENSING WITH AUTOMATED NODE IDENTITY

[0002] ASSIGNMENT

[0003] FIELD OF THE INVENTION

[0004] The invention relates to the field of radio frequency (RF) sensing in wireless networks, such as - but not limited to - Zigbee networks, for use in various different applications for home, office, retail, hospitality and industry.

[0005] BACKGROUND OF THE INVENTION

[0006] Due to rapid advancements in communication technology, multiple equipment and devices are now capable of communicating with one another inside a network, referred to as the Internet of Things (loT). While RF signals are transmitted, reflected, obstructed, and dispersed by things such as buildings, furnishings, automobiles, and living beings, it is possible to gather relevant data from received RF signals such as presence, position, moving directions, speed, and vitals. RF sensing, as opposed to traditional hardware sensors, provides consumers with low-cost and unobtrusive services. Furthermore, because RF signals are broadcast, they may be utilized not just to monitor multiple individuals but also to record changes in the environment across a vast region. With the use of RF technologies, end-users do not need to carry equipment or disrupt their daily routine. RF signals can be used to monitor macro and micro activity and to track objects.

[0007] Zigbee networks represent a type of a low-power / low-cost wireless networks which allow multi-hop communication among devices in a mesh topology. Zigbee devices offer reduced power consumption and cost, together with mesh networking capability, which make them suitable for use in large-scale deployments. Examples of application of Zigbee mesh networks include home automation, building automation, retail services, smart energy, and wireless indoor / outdoor lighting systems.

[0008] During initial setup, a new Zigbee device needs to perform a commissioning procedure that allows the new Zigbee device to join a Zigbee network. More specifically, the Zigbee device is configured into the network (e.g., obtains credentials (network key), unique ID, etc.), so that it can start communicating with other network nodes. If there is no network to join, the commissioning procedure may ensure that a new network is created. Conventional implementations of RF sensing (e.g., for presence sensing) in Zigbee networks employ small areas of e.g. two to five RF nodes which send messages to each other in a Round-Robin fashion where all elements in a group are equally chosen in some rational order (e.g., from the top to the bottom of a list and then starting again at the top of the list and so on). The receiving nodes keep track of the signal strength (e.g., received signal strength indicator (RS SI)) and expose that in their own next message. In a lighting system one of the nodes (e.g., a so-called collector node) may send all received signal strength information to a bridge device that runs an algorithm that calculates e.g. whether or not presence was detected.

[0009] However, such conventional implementations of RF sensing with more than two nodes per node group (e.g., lighting nodes per room) require commissioning of different roles of the nodes, which leads to additional commissioning work for an installer. Moreover, if the nodes for performing the various RF sensing functions are not selected properly, some motion or other sensing criteria may not be detected at all. Additionally, frequent (unicast) messages may be transmitted from each collector node to a gateway, which increases overall network load especially in larger Zigbee networks for office and / or industrial application. Finally, the above conventional implementation may restrict the size of an RF sensing area to a maximum of six nodes due to the size limit of a unicast message in Zigbee. In professional lighting applications for indoor or outdoor (e.g., parking garages), effective light group areas sizes may usually be (much) larger than six lights, which means that the installer is forced to decide which lighting nodes shall be selected to participate in the detection area. This may lead to an increase of detection errors or ‘dark spots’ in sensing coverage due to intricacies of a building space and / or installer errors.

[0010] For RF sensing in larger networks, it is therefore important to simplify the commissioning process (e.g., no additional commissioning beyond assigning of lights to the wireless network and optionally assigning lights to a light control group, which needs to be done anyway for illumination purposes). In addition, there should be no limitation to the number of nodes that can be part of an RF sensing detection area.

[0011] EP3925161B1 relates to a system for controlling message routing within a wireless network comprising a plurality of nodes.

[0012] WO2023083785A1 relates to an optical wireless communication (OWC) system configured to make use of observations of straylight reflections as generated by an OWC transmitter in order to support contention-based channel access. US2018026836A1 relates to a method for commissioning a wireless lighting control system for network connectivity does not require special device network configuration steps during manufacturing.

[0013] US2020403866A1 relates to a control device configured to form a network at a unique coordinated startup time. The control device identifies a role assigned to the control device in a previously formed network that the control device was attached to, and determines a unique coordinated startup time for the control device based on the role assigned to the control device in the previously-formed network.

[0014] SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide RF sensing with simplified commissioning and without node limitation in the detection area.

[0016] This object is achieved by an apparatus as claimed in claim 1, by a network node as claimed in claim 6, by a network system as claimed in claim 7, by a method as claimed in claim 13, and by a computer program product as claimed in claim 14.

[0017] According to a first aspect, an apparatus for controlling transmission of RF sensing messages from a network node in a wireless network is provided, wherein the apparatus is configured to: obtain a unique node identity of the network node; add the unique node identity to an own RF sensing probing message generated at the network node; monitor at the network node reception of RF sensing messages from other network nodes; and decide about transmission of the own RF sensing probing message to other network nodes of the detection area in dependence on a delay time that determines a time for the transmission of the own RF sensing probing message and that is controlled by a detected reception of an RF sensing probing message from other nodes in the detection area; wherein the apparatus is configured to set the delay time based on a comparison between the unique node identity of the network node itself and another unique node identify comprised in a received RF sensing probing message.

[0018] According to a second aspect, a network node (e.g., a luminaire and / or smart lamp and / or sensor), particularly a light node, is provided, that comprises an apparatus of the first aspect. According to a third aspect, a network system, particularly a lighting network system, is provided, that comprises the network node of the second aspect and a gateway configured to control a node group of the detection area, wherein the node group comprises the network node of the second aspect and the other network nodes.

[0019] According to a fourth aspect, a method of controlling transmission of an RF sensing message from a network node in a wireless network is provided, wherein the method comprises: obtaining a unique node identity of the network node; adding the unique node identity to an own RF sensing probing message of the network node; monitoring at the network node reception of an RF sensing probing and reporting messages from other network nodes; and deciding about transmission of the own RF sensing probing messages to other network nodes of the detection area in dependence on a delay time that determines the transmission of the own RF sensing probing message and that is controlled by a detected reception of an RF sensing probing message. deciding about transmission of the own RF sensing reporting message to other network nodes of the detection area in dependence on a hold-off delay time that holds off the transmission of the own RF sensing reporting message and that is controlled by a detected reception of an RF sensing reporting message; wherein the delay time is set based on a comparison between the unique node identity of the network node itself and another unique node identify comprised in a received RF sensing probing message.

[0020] Finally, according to a fifth aspect, a computer program product comprising code means for producing the steps of the method of the fourth aspect when run on a computer device.

[0021] Accordingly, a distributed decision-making process for transmission of RF sensing messages is proposed, which does not need any upfront commissioning of nodes that form the detection area. RF sensing can thus be implemented in a distributed way where every network node in a particular node group sends RF sensing probing messages and listens itself to all RF sensing probing messages received from its own neighbor nodes in the same node group. To avoid lots of network nodes sending their RF sensing probing message simultaneously, network nodes in the detection area that receive an RF sensing probing message are configured to start a delay timer which inhibits them from sending an RF sensing probing message themselves.

[0022] According to a first option that can be combined with any one of the above first to fifth aspects, transmission of a subsequent own RF sensing reporting message to other network nodes of the detection area may be decided in dependence on a hold-off delay time that holds off the transmission of the own RF sensing reporting message for a pre-defined time, and that is started by the reception of an RF sensing reporting message from another node.

[0023] According to a second option which may be combined with the first option or any one of the above first to fifth aspects, a first type of RF sensing probing and reporting messages, particularly Bluetooth Low Energy and / or WiFi messages, may be transmitted in a first frequency range and a second type of RF sensing probing and reporting messages, particularly Zigbee messages, may be transmitted in a second frequency range.

[0024] According to a third option which may be combined with the first or second option or any one of the above first to fifth aspects, the probing message delay time may be based on the following equations:

[0025] . (NodeIDt -NodeID7.trvriP„

[0026] At = - - - -1 cycleif NodelDl>NodelD2 n or

[0027] . (n+NodelD-i -NodeID7.trvrip„

[0028] At = - - - -1 cycleif NodelDl<NodelD2 n wherein At designates the delay time, n designates the number of nodes in a node group of the detection area, NodelDi designates the unique node identity of the network node (10) and NodelD designates a unique node identity of one of the other network nodes (10), from which an RF sensing probing message has been received. If several RF sensing probing messages have been received, NodelD may be the largest node ID value of the received messages or the node ID value of the message that has most recently been received.

[0029] According to a fourth option which may be combined with any one of the first to third options or any one of the above first to fifth aspects, the delay time may be set based on the following equation:

[0030] With ^min =tCy^lS> where tcyde designates the predetermined cycle time, Afytter designates a random time between 0 and the cycle time tcyde, and Atpriority designates an additional delay time that is based on the last time the network node sent the own RF sensing probing message.

[0031] According to a fifth option which may be combined with any one of the first to fourth options or any one of the above first to fifth aspects, a source address of a received messages may be used to assign a unique node ID to other network nodes.

[0032] According to a sixth option which may be combined with any one of the first to fifth options or any one of the above first to fifth aspects, a length of the predetermined cycle time may be selected such that each network node of the node group is enabled to send its own RF sensing probing message during the predetermined cycle time.

[0033] According to a seventh option which may be combined with any one of the first to sixth options or any one of the above first to fifth aspects, the unique node identity may be incrementally assigned to each network node of the node group and may define an order in which each network node is allowed to send its own RF sensing probing message.

[0034] According to an eighth option which may be combined with any one of the first to seventh options or any one of the above first to fifth aspects, a specific detection area identity may additionally be assigned to each network node of the node group, wherein the additional detection area identity may be used to decide if the network node needs to act on a received message comprising the additional detection area identity.

[0035] According to a ninth option which may be combined with any one of the first to eighth options or any one of the above first to fifth aspects, commissioning information may be used (e.g., by the gateway) to assign the unique node identity to the network node.

[0036] According to a tenth option which may be combined with any one of the first to ninth options or any one of the above first to fifth aspects, a configuration command message may be sent to the node group (e.g., by the gateway), wherein network nodes of the node group may be configured to send return messages with randomized delay after receiving the configuration message from the gateway, and wherein an order in which the return messages are received (e.g., at the gateway) may be used to determine and assign respective unique node identities to the network nodes of the node group. It is noted that the above apparatus may be implemented based on discrete hardware circuitries with discrete hardware components, integrated chips, or arrangements of chip modules, or based on signal processing devices or chips controlled by software routines or programs stored in memories, written on a computer readable media, or downloaded from a network, such as the Internet.

[0037] It shall be understood that the apparatus of claim 1, the network node of claim 7, the network system of claim 8, the method of claim 14, and the computer program product of claim 15 may have similar and / or identical preferred embodiments, in particular, as defined in the dependent claims.

[0038] It shall further be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

[0039] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following drawings:

[0042] Fig. 1 shows a schematic system architecture of a wireless lighting network in which various embodiments can be implemented;

[0043] Fig. 2 shows a flow diagram of an RF sensing procedure according to various embodiments;

[0044] Fig. 3 shows a schematic processing and signaling diagram of an automated identity assignment process according to a first embodiment;

[0045] Fig. 4 shows a schematic processing and signaling diagram of an automated identity assignment process according to a second embodiment; and

[0046] Fig. 5 shows a schematic processing and signaling diagram of an automated identity assignment process according to a third embodiment.

[0047] DETAILED DESCRIPTION OF EMBODIMENTS

[0048] Embodiments of the present invention are now described based on a Zigbee lighting network.

[0049] Fig. 1 shows a schematic architecture of a Zigbee lighting network in which embodiments of the present invention can be implemented. The network comprises connected luminaires (e.g., light emitting diode (LED) luminaires) (L) 10, smart (LED) lamps (SL) 12, separate (S) or integrated (L+S) sensors 14, and other connected devices with established networking and cloud architectures to enable data gathering and sharing, adding intelligence to all illuminated spaces.

[0050] The smart lamps 12 may be light emitting diode (LED) based lamps, gasdischarge lamp or filament bulb, plus any associated support, casing or other such housing, arranged to emit illumination in into an environment. The environment may be an indoor space such as one or more rooms and / or corridors of a building, or an outdoor space such as a park, garden, road, or outdoor parking area, or a partially covered space such as a stadium, structured parking facility or gazebo, or any other space such as an interior of a ship, train or other vehicle, or any combination of such possibilities.

[0051] The luminaires 10 may take any suitable form such as a ceiling or wall mounted luminaire, a free-standing luminaire, a wall washer, a chandelier, or a less conventional form such as embedded lighting built into an item of furniture, a building material such as glass or concrete, or any other surface.

[0052] The smart lamps 12 and / or the luminaires 10 may be equipped with a wireless communication interface allowing them to be controlled remotely by lighting control commands received from a user device (not shown) such as a smartphone, tablet, laptop or desktop computer, or by a wireless switch device (e.g., a wall switch) and / or based on sensor readings received from one or more of the (hardware) sensors 14.

[0053] The (hardware) sensors 14 may be configured to collect data about an illuminated environment, including motion, light levels, occupancy, people counting, temperature, humidity, air quality, and more. Positioning and density of sensors may depend on ceiling height, configuration of space, and other factors. In examples, at least some of the hardware sensors 14 (e.g., using passive infrared (PIR) or microwave) may also report occupancy by sending out a broadcast / multicast (either directly or via a Zigbee parent node).

[0054] Wireless gateways (WG) 20, e.g., deployed within a company’s standard information technology (IT) infrastructure 30 (e.g., routers, switch accessories etc.), are configured to communicate with connected devices via Zigbee.

[0055] The wireless gateway 20 may be configured to provide a commissioning process during initial installation and later expansions. Multiple gateways 20 may be connected over a backbone network (e.g., Ethernet). Wireless communication between the gateway 20 and network nodes (e.g., the luminaires 10, the lamps 12 and / or the sensors 14) may comply with the ZigBee Pro standard (IEEE 802.15.4, WPAN) in the 2.4 GHz frequency band within a predefined range (e.g., 10 m) from one or more of the ZigBee nodes to form a mesh network. The wireless communication between the nodes and the gateway 20 may be encrypted, as well as the communication between the gateway 20 and the IT infrastructure 30. Established wireless connections between the gateway 20 and nodes may allow for bidirectional control and sensor data exchange between the nodes and the IT infrastructure 30.

[0056] Furthermore, the network may use a building connectivity bridge (BGB) 40 to connect e.g. with an loT platform in a cloud 100 and provide secure remote connection between the lighting network and cloud services. This may comprise gateway services between the wireless gateways 20 and the cloud 100, enabling secure online access e.g. to a network toolbox e.g. for commissioning and management of the complete lighting system. More specifically, the bridge 40 may be configured to support port security and / or encrypted communication and / or secure firmware upgrade from the cloud 100, and to implement trusted device policy and / or secure firmware upgrade.

[0057] Software applications may offer web-based system management, operations, and control. Open, secure application programming interfaces (APIs) accessible e.g. through a web-based developer portal may allow system integrators and application developers to extend the lighting network with new capabilities, and to integrate network data and commands with other connected systems.

[0058] In the following embodiments, RF sensing probing signals / messages (e.g., Zigbee Inter-PAN messages, CSI-based messages, RF sensor signals, etc.) are to be understood as signals / messages used to detect presence, position, moving directions, speed, and / or vitals in a predetermined detection area. Furthermore, RF sensing reporting signals / messages (e.g., Zigbee multicast / groupcast / unicast messages, WiFi messages etc.) are to be understood as signals / messages used to report detection results to other nodes.

[0059] According to embodiments, it is proposed to implement RF sensing in the above lighting or other loT networks in a distributed way, which means that every node (e.g., luminaire 10, smart lamp 12 and / or sensor 14) in a particular node group (e.g., light group) may be configured to send RF sensing probing messages (e.g., in the form of a Zigbee Inter- PAN message, where Zigbee defines inter-personal area network (Inter-PAN) communication as a mechanism whereby Zigbee devices can perform exchanges of information with devices in their local area without having to form or join the same ZigBee network) and to listen itself to all RF sensing probing messages coming from its own neighbor nodes in the same node group. To achieve this, each node may calculate and keep track of signal strength (e.g., a running mean and variance value for the RSSI strengths) that it obtains based on its received RF sensing probing messages and / or RF sensing reporting messages and compares this to a threshold value. If the difference of the determined signal strength and the running mean average surpasses the threshold value, the node may send out an RF sensing reporting message (e.g., groupcast message) to the entire node group in a detection area, indicating that presence of a node has been detected.

[0060] Fig. 2 shows a flow diagram of an RF sensing procedure according to various embodiments.

[0061] The flow diagram of Fig. 2 may be implemented in each node of the lighting system, that shall be used as a part of the RF sensing process.

[0062] In an initial step S200, a unique node ID (UID) is assigned (ASS) to the node, e.g., during the node commissioning process or according to one of the automated assignment processes describe below in connection with Figs. 3 to 5.

[0063] Then, in step S201, a cycle time (CT) for RF sensing reporting messages (presence messages) is set e.g. during commissioning or by a communication from the network (e.g., the gateway 20 of Fig. 1).

[0064] When a triggering sensing start message (SSM) has been received e.g. from the network (e.g., the gateway 20 of Fig. 1) in step S202, a delay time (DT) is calculated and set for a hold-off timer (HOT) in step S203, e.g., to thereby reset the delay time.

[0065] In step S204, it is checked whether an RF sensing probing message (PM) has been received from another node. If so, the procedure branches off to step S205 and the delay time is recalculated (RECAL DT) and presence is determined / calculated in step S206 (CP) based on a comparison of the difference of the latest received signal strength information and the running mean value of this, with a predetermined threshold value. Then, the procedure branches back to step S207 where receipt of an RF sensing reporting message (RM) is monitored. If no RF sensing probing message has been received in step S204, the procedure proceeds directly to step S207.

[0066] If an RF sensing reporting message has been received in step S207, the procedure branches off to step S208 where the hold-off timer is started / reset and the light is dimmed up (DU) in step S209. Furthermore, a hold timer (HT) is reset in step S210, which counts a hold-time period, and the procedure branches back to step S211 where expiry (EXP) of the delay time is checked. If no RF sensing reporting message has been received in step S207, the procedure proceeds directly to step S211. If the delay time has not yet expired, the procedure continues with step S219.

[0067] If it is determined in step S211 that the delay time has expired, the procedure branches off to step S212 and an RF sensing probing message is sent (Tx PM). Then, in step S213 it is detected whether a presence has been detected (DP) in the previous cycle based on all the received probing messages in this cycle. If not, the procedure branches back and continues with step S219.

[0068] If it is determined in step S213 that a presence has been detected, the procedure continues with step S214 where it is checked whether the hold-off timer has expired. If not, the procedure branches back and continues with step S219.

[0069] If the hold-off timer has expired in step S214, the procedure continues with step S215 (Tx RM) and an RF sensing reporting message is broadcast (e.g., groupcast or multicast). Thereafter, the hold timer is reset in step S216, the hold-off timer is reset in step S217, and the light is dimmed up (DU) in step S218. Then, the procedure branches back to step S219 where it is checked whether the hold timer has expired (HT EXP). If so, the procedure branches off to step S220 and the light is dimmed down (DD) and the procedure returns to step S204 where receipt of an RF sensing probing message is monitored again.

[0070] If it is determined in step S219 that the hold timer has not yet expired, the procedure returns directly to step S204 where receipt of an RF sensing probing message is monitored again.

[0071] In embodiments, to avoid that many nodes send such an RF sensing reporting message simultaneously, all nodes in a detection area (e.g., an area covered by each gateway 20 of Fig. 1) that receive this RF sensing reporting message may start the hold-off timer which prevents them from sending an RF sensing reporting message themselves. In the meantime, they may keep updating their signal strength values (and, derived from that, the running mean values) based on RF sensing reporting messages they are receiving from their peer nodes.

[0072] Thus, when the hold-off timer expires and another node in the detection area (e.g., room) receives or measures a signal strength above the threshold, the other node may send another RF sensing reporting message which prompts other nodes to reset their hold-off timer again.

[0073] In a practical example, the hold-off time period may be selected to be significantly smaller (e.g., 1-20%) than the hold-time period to ensure a timely update of the presence detection if presence is still given in the observed detection area. However, a substantial number of RF sensing reporting messages may still be exchanged, especially in a large commercial installation. To avoid packet collisions, the following additional measures are proposed, that effectively lead to an adaptive synchronization of the message flow.

[0074] The overall cycle time set in step S201 (before a node sends an RF sensing message again) may be selected such that the number of RF sensing probing messages per cycle (a full cycle means that each of the nodes in the light group has been able to send its RF sensing probing message) fits well inside this cycle time. Therefore, for larger network groups (as may be observed in lighting systems for commercial offices, industry applications, parking garages etc.) the cycle time may be increased. While such an increased cycle time leads to a larger latency of presence detection, such a cycle-timed related latency penalty is more than compensated by the large set of transmitting nodes creating redundancy of detection. The redundancies can be exploited to quicker decide whether a room is occupied or not.

[0075] Furthermore, to reduce or limit the length of the RF sensing messages, information regarding previous cycles may be skipped, as this would severely limit the size of the detection area given the maximum size of an RF sensing reporting message. Instead, only the unique node ID of the node or another unique identifier (e.g., a device address) may be used by the other nodes to correlate the signal strength information of an RF sensing probing message with previously received RF sensing probing messages. This enables shorter messages, less chance of packet collisions and hence more messages per cycle.

[0076] During commissioning in step S201, each node may be (automatically) assigned a node ID incrementally (e.g., from 0 to n-1, with n being the total number of nodes within the light group), which defines the order in which each node is allowed to send RF sensing probing messages. This means that after sending out the first (broadcast / groupcast / multicast) message that triggers the start of the RF sensing process, each node may set a (different) delay timer in step S202 that determines when it should send its respective RF sensing probing message (e.g., in a direct relation to the RF sensing node ID of then node). In case the delay time for the node with the lowest node ID is the smallest, this node will first send out its RF sensing probing message. Upon receiving an RF sensing probing message, the other nodes may then recalibrate their respective delays based on the difference between their own node ID and the node ID of the received RF sensing probing message (S204). Such an adaptive time-slotting procedure ensures that even if packets get delayed due to contention, no follow-up collisions are caused by messages from the same detection area.

[0077] In case a node misses receiving one of the RF sensing probing messages (e.g., packets), it may maintain the last known delay time which should still be sufficient. Any subsequent RF sensing probing message that is received by the node may then correct the delay in most cases.

[0078] In a first example, the delay time (At) may be calculated as follows:

[0079] . (NodeIDt -NodeID7.trvriP„

[0080] At = - - - -1 cycleif NodelDl>NodelD2 n or

[0081] , ( N + Nodel -Nodel D7).trvrip „ , ,

[0082] At = - - -1 cycleif NodelDl<NodelD2) where n designates the number of nodes in the light group, NodelDl the receiving node and NodeID2 the transmitting node (e.g., if several RF sensing probing messages have been received, NodeID2 may be the largest node ID value of the received messages or the node ID value of the message that has most recently been received).

[0083] Alternatively, in a second example, the delay times between RF sensing probing messages may be determined as follows: with ^min =tCy^lS> where Afytter designates a random time between 0 and the cycle time tcycle-, and Atpriority designates an additional delay time that is based on the last time this specific node sent its Rf sensing probing message. The value of Atpriority should be larger when the last time is closer. This ensures that nodes which have not sent recently automatically get a higher chance to be the first in line.

[0084] The minimum delay Atmin can be calculated after commissioning (where n is known) by a commissioning app or a system backend. The minimum delay may be configured for every node in a light group, e.g., via a broadcast or multicast message. The node that has the smallest minimum delay time may send out its status (e.g., either occupancy-on or occupancy-off) first.

[0085] In embodiments, all other nodes may reset their delay timers and may select again another waiting time which may be the minimum delay time plus a new random jitter time. As an overall result, no more than n messages are sent within a cycle period, which ensures that the overall traffic load allocated by the building owner for the RF sensing function is not exceeded, while the RF sensing nodes act independently from each other without any configuration required by the installer other than the minimum delay time and a range for random jitter. Note that in principle the random jitter may be derived from the minimum delay time provided by the installer.

[0086] The adaptive time-slotting procedure described above may be used in cases where non-RF-sensing -related messages (such as network maintenance messages, e.g. route requests etc.) are being sent around. By actively delaying RF sensing probing messages upon reception of other messages from other nodes, network crowding can be prevented effectively.

[0087] Moreover, network crowding may also be avoided by selecting the overall cycle time tcycie of a large multi-node RF sensing system to avoid that RF sensing probing messages are sent too close to each other. At configuration time, the cycle time may be selected such that it scales the number of nodes in the light group with the total number in the lighting control network (e.g., a first lighting network with just 50 nodes vs. a second lighting network with 250 nodes in a single network).

[0088] In the above embodiments, a need for commissioning of nodes involved in RF sensing can be prevented by providing an automated assignment of node identifiers.

[0089] In the following, different automated node identity assignment procedures are described with reference to different processing and signaling diagrams of Figs. 3 to 5. The diagrams indicate involved network entities (i.e., a gateway 20 and nodes 10) at the top, wherein arrows indicate successive message flows in time-dependent order and wherein blocks indicate processing steps with time passing from the top to the bottom. The gateway 20 can be either a physical gateway (e.g., gateway 20 in Fig. 1) which is permanently connected to the network, or a temporary gateway in the form of a smart mobile device (e.g., phone or tablet) which can set up an ad hoc connection to the network.

[0090] Fig. 3 shows a schematic processing and signaling diagram of an automated identity assignment process according to a first embodiment, where the gateway 20 is configured to use commissioning information to assign unique node IDs to n nodes 10 (N1 to Nn).

[0091] In the first embodiment, the gateway 20 is configured to assign the unique node IDs by sending respective unicast messages to each of the nodes 10.

[0092] Prior to assigning the unique node IDs, the gateway 20 queries the nodes 10 of the light group for their network parameters NP1 to NPn (e.g., short addresses) in steps S401- 1 to S401-n. The gateway 20 then assigns in step S402 a unique node ID UIDi to each short address SAi in a table. After this, the gateway sends in steps S403-1 to S403-n respective unicast or broadcast messages to deploy the node ID numbers UIDI to UIDn to each of the nodes (e.g., lights) in the node group (e.g., light group).

[0093] In case of multiple node groups within a single larger network, a specific detection area ID may additionally be assigned to each of the nodes 10 in a node group. The nodes 10 may then use the additional detection area ID to decide if they need to act on a specific message that they receive, while they use the node ID to synchronize their own sending time as described in the embodiments above.

[0094] Fig. 4 shows a schematic processing and signaling diagram of an automated identity assignment process according to a second embodiment, wherein the nodes N1 to Nn 10 are configured to send return messages RET1 to RETn with randomized delay after receiving a broadcast message from the gateway 20.

[0095] In the second embodiment, the gateway 20 is configured to send (unicast, broadcast, groupcast or multicast) in steps S501-1 to S501-n a special configuration command (CC) to the nodes 10, that triggers all receiving nodes to send back their respective return message RET1 to RETn, e.g., by unicast or broadcast transmission, in steps S502-1 to S502-n. After sending out the trigger message (configuration command), the gateway 20 then listens in step S503 for a specified time-period for return messages and uses the order in which the return messages RET1 to RETn are received to determine and assign respective unique node IDs UIDi to the nodes N1 to Nn 10. In an example, the unique node IDs UIDi may be determined based on a measured reception time tRXRETi (e.g., as counted by a timer that has been triggered by the trigger message). After all return messages RET1 to RETn have been received, the gateway 20 starts sending out information about the assigned unique node IDs UIDI to UIDn (e.g., by a series of unicast or broadcast messages) in steps S504-1 to S504-n. In an example, the return messages RET1 to RETn may also comprise information about a prescribed random delay factor used by the respective node 10 in case the delay factors of two nodes are very close. If the number of nodes 10 in the detection area becomes too large, the correspondingly increased cycle time may become too long to guarantee a maximum latency time provided by the installer of the lighting control system. In this case, the gateway 20 may decide to skip nodes randomly or regularly (e.g., every Nth node, N=2, 3. . .) during the assignment of unique node IDs and detection area IDs, when automatically setting up the RF sensing system. This effectively reduces the number of nodes participating in RF sensing, while still maintaining a sufficiently large population to guarantee reliable presence detection.

[0096] In case a (series of) non-RF-sensing-related high-priority message(s) need to be sent through the network (e.g., in case of an over-the-air update), the gateway 20 may decide to either temporarily stop / interrupt RF sensing (e.g., and switch on the lights in the meantime).

[0097] Alternatively, the system may temporarily increase the RF sensing cycle time (used within the nodes 10) by a sufficiently large factor (e.g., by a sending a first configuration message), so that the network capacity is increased to allow for accommodating the high-priority messages. After the non-RF-sensing related high-priority action is completed, the normal cycle time may then be again restored (e.g., by sending a second configuration message).

[0098] Fig. 5 shows a schematic processing and signaling diagram of an automated identity assignment process according to a third embodiment, wherein the nodes N1 to Nn 10 are configured to use the source address of received messages to create an internal table of other nodes in the light group and internally assign an internal unique node ID UIDi to each of the other nodes. The assignment of the third embodiment only needs a short period of ‘learning’ as to which other nodes are located in the detection area.

[0099] Note that the sequence of steps S601-1 to S60n-n of Fig. 5 may vary depending on which of the nodes N1 to Nn receives which message first and correspondingly allocates its internal unique node IDs UIDi.

[0100] In steps S601-1 to S601-n-l, the first node N1 receives messages with respective source addresses SM2 to SMn from the other nodes N2 to Nn and assigns respective internal unique node IDs UID2 to UIDn to the other nodes N2 to Nn in step S602.

[0101] In steps S603-1 to S603-n-l, the second node N2 receives messages with respective source addresses SMI and SM3 to SMn from the other nodes N1 and N3 to Nn and assigns respective internal unique node IDs UIDI and UDI2 to UIDn to the other nodes N1 and N3 to Nn in step S604, and so on for nodes N3 to Nn-1. Finally, in steps S60n-l to S60n-n-l, the n-th node Nn receives messages with respective source addresses SMI to SMn-1 from the other nodes N1 to Nn-1 and assigns respective internal unique node IDs UID1 to UIDn-1 to the other nodes N1 to Nn-1 in step S60n-n.

[0102] If the above automated identity assignment of the third embodiment is combined with the random delay time Afytter described above, no commissioning action needs to be implemented since the nodes 10 can figure out by themselves individually which unique node ID belongs to which incoming message.

[0103] It is noted that, in all the above embodiments, CSI-based RF sensing (e.g., WiFi sensing) can be used as well, where a channel state information (CSI) describes how a signal propagates from a transmitter to a receiver and represents the combined effect of, for example, scattering, fading, and power decay with distance. Thus, CSI captures how wireless signals travel through the surrounding environment and can thus be used for wireless sensing purposes.

[0104] Moreover, in a further embodiment, nodes may be configured to use dualradios for RF sensing (i.e., the same radio can either communicate via Bluetooth Low Energy (BLE) or Zigbee messages). These radios may communicate semi -concurrently or in a halfduplex mode (i.e., when the BLE radio is actively sensing or receiving, the Zigbee radio is blocked).

[0105] In a modification, one radio may be configured to use BLE sensing and also WiFi sensing, e.g., utilizing a single chip WiFi+BLE radio. Thus, in such a modification, two different sensing token rings may be provided, wherein a first ring is configured to use WiFi sensing messages implemented as described in the above embodiments, and a second ring is configured to use BLE sensing messages as described in the above embodiments.

[0106] To summarize, methods and apparatus for implementing RF sensing in a distributed way among nodes of a wireless system have been described, wherein every node in a particular node group sends RF sensing probing messages (e.g., in the form of a Zigbee Inter-PAN message or a WiFi message or the like) and listens itself to all RF sensing probing messages coming from its own neighbor nodes in the same node group. Each node may calculate and keep track of a signal strength of messages that it receives from each of the other nodes and calculate the difference of this actual signal strength value with respect to a running average strength of a predefined number of previous messages. This difference is compared to a threshold value. If the threshold value is surpassed, the node will send out an RF sensing reporting message to the entire node group to indicate that a presence has been detected. A unique node ID may be assigned to the nodes in an automated fashion (without requiring any commissioning effort), which determines the order in which the nodes send out their RF sensing probing messages. To avoid that lots of nodes send their RF sensing reporting messages simultaneously, all nodes in a detection area that receive an RF sensing reporting message may start a hold-off timer for temporarily delaying own transmissions. Furthermore, a hold timer may be used that determines how long the lights should stay on after the last received presence detection.

[0107] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments.

[0108] The invention can be implemented in various types of connected lighting systems (professional) in offices, healthcare, industry, retail, hospitality, homes, as well as applications for agriculture and outdoor applications (e.g., parking lots / garages, standalone networks in outdoor) or other wireless networks where RF sensing is implemented. The proposed RF sensing and / or automated node identity assignment procedures can be applied to and possibly standardized in other types of multi-hop networks and with other types of messages. Moreover, the invention can be applied in any product that implements a wireless network (e.g., Zigbee, WiFi or others). The present invention is equally applicable to (low-power) network devices of any other wireless technology (e.g., BLE, Infrared (IR), near field communication (NFC), wireless local area communication (Wi-Fi)) with a second wireless (e.g. multi-hop) technology (e.g. Zigbee PRO, Thread, WirelessHART, SmartRF, CityTouch, IP500, and any other mesh or tree-based technology).

[0109] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in the text, the invention may be practiced in many ways, and is therefore not limited to the embodiments disclosed. It should be noted that the use of particular terminology when de-scribing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated. Additionally, the expression “at least one of A, B, and C” is to be understood as disjunctive, i.e., as “A and / or B and / or C”. A single unit or device may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0110] The described operations like those indicated in Figs. 2 to 5 can be implemented as program code means of a computer program and / or as dedicated hardware of gateway or luminaire devices, respectively. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

CLAIMS:

1. An apparatus for controlling transmission of radio frequency, RF, sensing messages from a network node (10) in a wireless network, wherein the apparatus is configured to: obtain a unique node identity of the network node (10); add the unique node identity to an own RF sensing probing message generated at the network node (10); monitor at the network node (10) reception of RF sensing probing and reporting messages from other network nodes (10); decide about transmission of the own RF sensing probing message to other network nodes (10) of the detection area in dependence on a delay time that determines a time for the transmission of the own RF sensing probing message and that is controlled by a detected reception of RF sensing probing message from other nodes in the detection area; wherein the apparatus is configured to set the delay time based on a comparison between the unique node identity of the network node itself and another unique node identify comprised in a received RF sensing probing message.

2. The apparatus of claim 1, configured to decide about transmission of a subsequent RF sensing reporting message to other network nodes (10) of the detection area in dependence on a hold-off delay time that holds off the transmission of the own RF sensing reporting message and that is controlled by a detected reception of an RF sensing reporting message and / or absence of reception of an RF sensing reporting message.

3. The apparatus of claim 1 or 2, wherein the apparatus is configured to control transmission of a first type of RF sensing probing and reporting messages, particularly Bluetooth Low Energy and / or WiFi messages, in a first frequency range and a second type of RF sensing probing and reporting messages, particularly Zigbee messages, in a second frequency range.

4. The apparatus of any one of the preceding claims, configured to set the delay time based on the following equations:. (Nodel D-, -Nodel D7.trvri„ „At = - - - -1 cycleif NodelDl>NodelD2 n or. (n+NodeIDt -NodeID7.trvriP„At = - - - -1 cycleif NodelDl<NodelD2 n wherein A t designates the delay time, n designates the number of nodes in a node group of the detection area, NodelDj designates the unique node identity of the network node (10) and NodeID2designates a unique node identity of one of the other network nodes (10) , from which an RF sensing probing message has been received.

5. The apparatus of any one of the preceding claims, configured to use a source address of a received messages to assign a unique node ID to other network nodes (10).

6. A network node (10, 12), particularly a light node, comprising an apparatus as claimed in any one of the preceding claims.

7. A network system, particularly a lighting network system, comprising the network node (10) of claim 6 and a gateway (20) configured to control a node group of the detection area, wherein the node group comprises the network node (10) of claim 6 and the other network nodes (10).

8. The network system of claim 7, wherein a length of the predetermined cycle time is selected such that each network node (10) of the node group is enabled to send its own RF sensing probing message during the predetermined cycle time.

9. The network system of claim 7 or 8, wherein the unique node identity is incrementally assigned to each network node (10) of the node group and defines an order in which each network node (10) is allowed to send its own RF sensing probing message.

10. The network system of any one of claims 7 to 9, wherein a specific detection area identity is additionally assigned to each network node (10) of the node group, and wherein the network node (10) is configured to use the additional detection area identity to decide if it needs to act on a received message comprising the additional detection area identity.

11. The network system of any one of claims 7 to 10, wherein the gateway (20) is configured to use commissioning information to assign the unique node identity to the network node (10).

12. The network system of any one of claims 7 to 11, wherein the gateway (20) is configured to send a configuration command message to the node group, wherein network nodes (10) of the node group are configured to send return messages with randomized delay after receiving the configuration message from the gateway (20), and wherein the gateway (20) is configured to use an order in which the return messages are received to determine and assign respective unique node identities to the network nodes (10) of the node group.

13. A method of controlling transmission of radio frequency, RF, sensing messages from a network node (10) in a wireless network, wherein the method comprises: obtaining a unique node identity of the network node (10); adding the unique node identity to an own RF sensing probing message of the network node (10); monitoring at the network node (10) reception of RF sensing probing and reporting messages from other network nodes (10); and deciding about transmission of the own RF sensing probing message to other network nodes (10) of the detection area in dependence on a delay time that determines a time of the transmission of the own RF sensing probing message and that is controlled by a detected reception of an RF sensing probing message;wherein the delay time is set based on a comparison between the unique node identity of the network node itself and another unique node identify comprised in a received RF sensing probing message.

14. A computer program product comprising code means for producing the steps of claim 13 when run on a computer device.

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