Controller for RF-based sensing configuration

Abstract

The present invention is directed to a controller (100) for controlling a radio frequency based sensing arrangement (150) including at least a transmitter node (152) configured to provide a wireless communication signal (S) and a receiver node (152) configured to receive the provided wireless communication signal, where at least the transmitter node is operable in an active mode (AM) and a sleep mode (SM). The controller is configured to determine a preferred amount of transmit power (Pmin) and to control operation of at least the transmitter node according to a signal provision schedule (SP) alternating between active cycles during which the transmitter node is operated in the active mode and sleep cycles during which the transmitter node is operated in the sleep mode. In the active mode, the wireless communication signal is provided at the determined preferred amount of transmit power, thus enabling efficient use of power resources.

Description

[Technical field]

[0001] The present invention is directed to a controller suitable for controlling a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals. The present invention is also directed to a transmitter node, a radio frequency based sensing arrangement, a method for operating the controller, and a computer program product. [Background technology]

[0002] Document WO2021 / 243597A1 describes a method, apparatus, and computer-readable medium for wireless communication in a first wireless device, or node, where the first wireless device transmits a radio frequency (RF) sensing waveform in a frequency band during a first time period, and transmits or receives wireless communication with a second wireless device in the frequency band during a second time period. In one example, the wireless device or node may be in an idle mode or discontinuous reception mode, and the wireless device may periodically monitor for communications from another device and may enter a sleep mode or low power mode during periods between periodic monitoring / transmissions. Summary of the Invention [Problem to be solved by the invention]

[0003] It would be beneficial to enable more efficient use of power resources in wireless devices or nodes used in radio frequency based sensing configurations. [Means for solving the problem]

[0004] According to a first aspect of the invention, a controller is described. The controller is suitable for controlling a radiofrequency-based sensing arrangement configured to detect activity in a sensing volume using wireless communication signals. The radiofrequency-based sensing arrangement includes at least a transmitter node configured to provide wireless communication signals according to a wireless communication protocol, and a receiver node configured to receive the provided wireless communication signals. At least the transmitter node is operable in an active mode in which the wireless communication signals are provided, and in a sleep or low power mode in which the wireless communication signals are not provided. The controller of the first aspect of the invention is advantageously configured to control operation of the transmitter node and the receiver node to determine a preferred transmission power amount indicative of a minimum transmission power of the wireless communication signals provided by the transmitter node that results in a reliable communication link for wireless communication between the transmitter node and the receiver node. Thus, a preferred amount of transmission power is a transmission power equal to or slightly greater than a transmission power threshold that ensures a reliable communication link, i.e., a link between the transmitter node and the receiver node over which information can be communicated within a given quality, such as bit rate, error rate, signal-to-noise ratio, or any other parameter known to one skilled in the art for establishing the reliability of a communication link.

[0005] Further, the controller of the first aspect of the present invention is configured to control operation of at least the transmitter node in accordance with a signal provision schedule that alternates between active cycles, during which the transmitter node is operated in an active mode, and sleep cycles, during which the transmitter node is operated in a sleep mode, and in the active mode, the wireless communication signal is provided at the determined preferred amount of transmit power.

[0006] Determining a preferred amount of transmit power and controlling at least the transmitter node to provide communication signals only at the preferred amount of transmit power in an active mode enables better use of power resources in a radio frequency based sensing arrangement, particularly at the transmitter node.

[0007] In the following, an embodiment of the first aspect of the present invention will be described.

[0008] In particular, a transmitter node, a receiver node, or both a transmitter node and a receiver node are transceiver nodes configured to provide and receive wireless communication signals. In general, the terms transmitter and receiver are used in reference to a particular wireless communication signal that is provided by a node referred to as a transmitter node and received by a node referred to as a receiver node. This does not necessarily mean that a node referred to as a transmitter node is not configured to receive wireless communication signals, or that a node referred to as a receiver node is not configured to provide wireless communication signals.

[0009] The transmitter node, and in some embodiments also the receiver node, can operate in an active mode in which a wireless communication signal is provided, and in a sleep or low power mode in which a wireless communication signal is not provided. Thus, the active mode indicates a period during which a wireless communication signal, particularly a wireless communication signal used for determining activity in the sensing volume, can be provided as needed. The transmitter node may, for example, delay providing a wireless communication signal until it is operated in the active mode, or in certain embodiments, may even discard a wireless communication signal if the intended transmission time coincides with the sleep mode. During operation in the sleep mode, i.e., during any of the sleep cycles, no wireless communication signal is provided, or at least no wireless communication signal for activity determination is provided.

[0010] The radio frequency based sensing arrangement is configured to detect activity in a sensing volume using wireless communication signals. Activity in the sense of this disclosure includes presence and movement detection of a subject or object in the sensing volume. It may also include other activities related to the subject, such as breathing rate, heart rate, fall detection, gestures, facial expressions, etc. A sensing volume is a region of space in which variations in a particular signal or communication link parameter, such as a radio frequency signal strength indicator (RSSI) or channel state information (CSI), can be associated with a given activity, or in other words, a given activity can be correlated to variations in the particular signal or communication link parameter. Thus, the sensing volume depends on the relative locations of the transmitter and receiver nodes and the surroundings, which affect the multipath behavior of the provided wireless communication signals.

[0011] In a preferred embodiment, the predetermined wireless communication protocol is low energy Bluetooth (BLE). In alternative embodiments, the wireless communication protocol is Bluetooth, Wi-Fi, Thread, ZigBee, or any other suitable wireless communication protocol known to those of skill in the art.

[0012] In a particular embodiment, the controller is or forms part of an access point, a router, or any other possible control device of the radio frequency based sensing arrangement. The controller includes a transceiver unit configured to provide and receive wireless communication signals according to, among other things, a predefined wireless communication protocol. The controller advantageously provides instructions wirelessly to the transmitter node and the receiver node via the transceiver unit. In another embodiment, the controller has a dedicated wired connection to the transmitter node, the receiver node, or both the transmitter node and the receiver node. Using the respective links (wired or wireless), the controller controls the operation of the transmitter node and the receiver node, for example sending operational instructions and receiving operational data from the receiver node that allows the determination of a preferred amount of transmission power. The controller is also configured to determine or ascertain a signal provision schedule, which may be predetermined and may also be updatable depending on the operating conditions of the radio frequency based sensing arrangement. Among other things, the controller includes a communication unit for communicating, either directly or via another device, with the transmitter node and the receiver node, and a processing unit for generating appropriate operating instructions to be provided to the transmitter node and, if necessary, the receiver node via the communication unit to ascertain or determine a signal providing schedule, determine a preferred amount of transmit power, and operate the transmitter node in accordance with the signal providing schedule.

[0013] The preferred amount of transmission power is a transmission power equal to or slightly greater than a transmission power threshold at which a reliable communication link is ensured. In one embodiment, the preferred transmission power is determined in a commissioning phase under known and controlled parameters, in particular with a known number of subjects (which may include no subjects) and known positions and / or movements within the sensing volume. Depending on these parameters and the surrounding environment, the metrics (e.g., RSSI, CSI, etc.) for determining the reliability of the communication link have different values. This is because activities performed by subjects (presence, movements, gestures, breathing, heart rate, etc.) may affect the way the wireless communication signal propagates and change the value of the selected metric. In some embodiments, in particular when the preferred transmission power is determined under parameters related to low occupancy of the sensing volume (e.g., no subjects), the transmission power threshold includes sufficient headroom to ensure reliable communication in the situation where subjects are present in the sensing volume. In other embodiments, the transmit power threshold may change over time, for example, differently, and preferably increased, when significant activity is detected in the sensing volume, to ensure reliable communication of the wireless communication signal.

[0014] In one embodiment, to determine the preferred amount of transmission power, the controller is configured to control the provision of the set of wireless communication signals at different transmission powers, preferably at different times, ascertain signal quality values ​​of each of the wireless communication signals received at the receiver node, and select as the preferred amount of transmission power the lowest transmission power from the transmission powers of the set of wireless communication signals that results in a signal quality value above a signal quality threshold. Examples of suitable signal quality parameters include received signal strength indicators (RSSIs) of the wireless communication signals received at the receiver node, channel state information regarding the communication link between the transmitter node and the receiver node, signal-to-noise ratios, or any other suitable parameters known to those skilled in the art. Channel state information refers to the channel characteristics of the communication link, which indicate how a signal propagates from the transmitter node to the receiver node and represents the combined effect of several parameters such as scattering, fading, power attenuation over distance, etc. Preferably, the transmission power is gradually lowered. The probability of determining a preferred amount of transmission power arbitrarily close to the minimum amount of transmission power required for a reliable communication link increases as the number of communication signals in the set of wireless communication signals increases.

[0015] In a particular embodiment, the transmitter node is configured to provide wireless communication signals in two or more frequency bands, and a respective preferred amount of transmit power is determined for the multiple communication channels, each communication channel associated with a respective frequency band in which the transmitter node is operable to provide wireless communication signals. In this embodiment, in an active mode, the transmitter node is operated to provide wireless communication signals using the communication channel for which the lowest preferred amount of transmit power has been determined and using the determined preferred amount of transmit power. The controller may review signal quality values ​​(e.g., RSSI) associated with each of the wireless communication signals received on each channel and limit communications between the transmitter node and the receiver node in the active mode to only the communication channel(s) having the lowest preferred amount of transmit power.

[0016] As mentioned above, the signal delivery schedule, i.e., the timely distribution of active and sleep cycles for the active and sleep modes, respectively, can be updated or modified with respect to the initial signal delivery schedule to match the current needs of the radio frequency based sensing configuration. In certain embodiments, the controller is further configured to check activity data indicative of detection of activity in the sensing volume, and vary the signal delivery schedule depending on the checked activity data. For example, the duration of the active cycle and / or the sleep cycle can be increased or decreased if no activity (e.g., presence or motion) is detected. After activity detection, the previous latency, i.e., the timely duration of the active and sleep cycles, can be restored by the controller, which controls the operation of the transmitter node according to the appropriate signal delivery schedule.

[0017] In yet another embodiment, the controller is additionally or alternatively configured to check power supply data indicative of the power supply status of the transmitter node or receiver node, and to vary the signal provision schedule depending on the checked power supply data. This is particularly suitable when using a transmitter node or receiver node that is battery powered, i.e. not connected to a mains power source or any other long-term power source. The power supply data in this particular example indicates the battery status, e.g. how much power the battery currently supplies, or how much power is left in the battery, or how long the battery can power the transmitter device assuming normal operation of the transmitter node or receiver node, etc. If the power supply data indicates that the available power is insufficient or below a predefined power threshold amount, the controller is configured to adapt the signal provision schedule accordingly, e.g. by reducing the duration of active cycles or by removing some of these active cycles. Additionally or alternatively, the controller can also control the operation of the transmitter node such that some wireless communication signals are not transmitted.

[0018] In another embodiment, the controller is additionally or alternatively configured to control the operation of at least the transmitter node to provide at least one keepalive signal as a wireless communication signal in each active cycle during operation in active mode according to the signal providing schedule. This is particularly advantageous in an embodiment using BLE as the wireless communication protocol. To maintain a communication link, the transmitter node needs to provide radio packets within a given time window. The signal providing schedule is adapted to this time window such that there is always an active cycle in this time window. Advantageously, when the transmitter node does not need to provide a wireless communication signal in a frame of normal operation, the controller causes the transmitter node to provide a keepalive signal to maintain the communication link. Thus, a keepalive signal is a communication signal sent by one device to another device to check that the communication link between the two devices is working or to prevent the communication link from being broken.

[0019] According to a second aspect of the invention, a transmitter node is disclosed, suitable for a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the transmitter node including a controller according to the first aspect of the invention and a transmitter coupled to the controller and configured to provide wireless communication signals according to a predetermined wireless communication protocol.

[0020] According to this second aspect, the controller is integrated within the transmitter node and the connection between the controller and the transmitter is established in a shared housing, preferably, but not necessarily, in a wired manner.

[0021] Thus, the transmitter node of the second aspect shares the advantages of the controller of the first aspect of the invention.

[0022] In the following, an embodiment of the transmitter node of the second aspect of the present invention will be described.

[0023] In one embodiment, the transmitter node includes a receiving unit and thus may be referred to as a transceiver node.

[0024] In another embodiment, the transmitter node further includes a battery unit for providing operating power. Operating a dedicated radio device on battery power has been widely considered impractical for current RF-based sensing applications because the drain of a continuously active radio quickly depletes the battery unit and thus results in insufficient life. However, the control of the operation of the transmitter node by a controller according to the first aspect of the invention, in particular a controller integrated within the transmitter node, allows for an increase in the life of the battery unit.

[0025] In a preferred embodiment, the transmitter node further comprises a battery control unit arranged and configured to ascertain power supply data indicative of a battery status of the battery unit and to provide said power supply data to the controller, which, inter alia, is advantageously configured to receive the power supply data and to vary the signal provision schedule in dependence on the received power supply data.

[0026] A third aspect of the invention is formed by a radio frequency based sensing arrangement configured to detect activity in a sensing volume using wireless communication signals. The radio frequency based sensing arrangement includes at least one transmitter node configured to provide wireless communication signals according to a wireless communication protocol, the at least one transmitter node being operable in an active mode in which a wireless communication signal is provided and in a sleep mode in which a wireless communication signal is not provided. The radio frequency based sensing arrangement also includes at least one receiver node configured to receive the transmitted wireless communication signals and at least one controller according to the first aspect of the invention. Notably, the controller may be integrated into the transmitter node, thus forming a transmitter node according to the second aspect of the invention. Additionally or alternatively, the controller may be integrated into the receiver node, thus forming an additional aspect of the invention.

[0027] The radio frequency based sensing arrangement also includes an activity determination unit configured to ascertain a signal quality value of a wireless communication signal received by the receiver node, the signal quality value being correlatable to activity within a sensing volume defined by a communication link between the transmitter node and the receiver node, and to determine activity within the sensing volume using the ascertained signal quality value.

[0028] Thus, the radio frequency based sensing arrangement of the third aspect of the present invention shares the advantages of the controller of the first aspect or the transmitter node of the second aspect.

[0029] In the following, an embodiment of the radio frequency based sensing arrangement of the third aspect is described.

[0030] In one embodiment, the activity determination unit is incorporated in the receiver node, which determines a signal quality value, e.g., RSSI or CSI, and determines the presence or absence of activity in the sensing volume. In another embodiment, particularly in an embodiment where the receiver node is a battery-powered node, the activity determination unit is not incorporated in the receiver node, and the receiver node determines the signal quality value and provides said value to the activity determination unit, e.g., via a wireless communication signal. In an exemplary embodiment, the activity determination unit is a unit of an access point, a router, or any other possible control device of a radio frequency based sensing arrangement. In another embodiment, both the transmitter node and the receiver node are controlled by a controller.

[0031] In one embodiment, the signal quality value is a received signal strength indicator (RSSI), which indicates the signal strength of a wireless communication signal received at a receiver node, or a channel state information (CSI), which indicates the channel conditions of a communication link between a transmitter node and a receiver node.

[0032] In one embodiment, the RF-based sensing arrangement is, or forms part of, a wirelessly controlled lighting arrangement including lighting devices and associated devices such as switches, sensors, etc., whose operation is controlled by wireless communication signals.

[0033] A fourth aspect of the present invention is formed by a method for operating a controller suitable for controlling a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the radio frequency based sensing arrangement including at least a transmitter node configured to provide wireless communication signals according to a wireless communication protocol, and a receiver node configured to receive the provided wireless communication signals, wherein at least the transmitter node is operable in an active mode in which a wireless communication signal is provided, and in a sleep mode in which no wireless communication signal is provided. The method of the fourth aspect of the present invention comprises: controlling operation of the transmitter node and the receiver node to determine a preferred transmit power amount indicating a minimum transmit power of a wireless communication signal provided by the transmitter node that provides a reliable communication link for wireless communication between the transmitter node and the receiver node; and controlling operation of at least the transmitter node in accordance with a signal provision schedule that alternates between active cycles, during which the transmitter node is operated in an active mode, and sleep cycles, during which the transmitter node is operated in a sleep mode, where in the active mode, the wireless communication signal is provided at the determined preferred amount of transmit power.

[0034] Thus, the method of the fourth aspect shares the advantages of the controller of the first aspect of the invention.

[0035] In the following, an embodiment of the method according to the fourth aspect of the invention is described.

[0036] In one embodiment, determining the preferred amount of transmit power includes controlling the provision of the set of wireless communication signals at different transmit powers, ascertaining signal quality values ​​for each of the wireless communication signals received at the receiver node, and selecting as the preferred amount of transmit power the lowest transmit power from the transmit powers of the set of wireless communication signals that results in a signal quality value above a signal quality threshold.

[0037] In another embodiment, the step of determining a preferred amount of transmit power is performed for a plurality of communication channels, each associated with a respective frequency band, and the method includes providing a wireless communication signal using the communication channel for which a lowest preferred amount of transmit power has been determined and using the determined preferred amount of transmit power.

[0038] In yet another embodiment, the method additionally or alternatively includes ascertaining activity data indicative of detection of activity in the sensing volume, and altering the signal delivery schedule dependent on the ascertained activity data.

[0039] In another embodiment, the method additionally or alternatively includes ascertaining power supply data indicative of a power supply state of the transmitter node or the receiver node, and altering the signal provision schedule in dependence on the ascertained power supply data.

[0040] In a preferred embodiment, the method additionally or alternatively includes controlling operation of at least the transmitter node to provide at least one keep-alive signal as a wireless communication signal in each active cycle during operation in an active mode according to the signal providing schedule, in particular when an active cycle is about to end and no wireless communication signal is being provided, the method controls the providing of the keep-alive signal to maintain a communication link between the transmitter node and the receiver node.

[0041] The method of the third aspect can be implemented by an access point, a router, or any other possible control device of a radio frequency based sensing arrangement, including a controller, or by a transmitter node of a radio frequency based sensing arrangement, including a controller. In the former case, the control of the transmitter node and the receiver node is preferably performed wirelessly, using a predefined wireless communication protocol. Alternatively, the control of the transmitter node and the receiver node can be performed via a dedicated wired connection.

[0042] A fifth aspect of the invention is formed by a computer program comprising instructions which, when executed by a controller, cause the controller to carry out the steps of the method according to the fourth aspect. It is to be understood that the controller according to claim 1, the transmitter node according to claim 7, the radio frequency based sensing arrangement according to claim 10, the method for operating the controller according to claim 13 and the computer program according to claim 15 have similar and / or identical preferred embodiments, in particular as defined in the dependent claims.

[0043] It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or the above embodiments with the respective independent claim.

[0044] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 shows a schematic block diagram of one embodiment of a radio frequency (RF) based sensing arrangement in accordance with the present invention. [Diagram 2] 2 shows a first time diagram illustrating signal exchange between a transmitter node and a receiver node of an RF-based sensing arrangement according to the present invention; [Diagram 3] FIG. 2 shows a second time diagram illustrating signal exchange between a transmitter node and a receiver node of an RF-based sensing arrangement according to the present invention. [Figure 4] FIG. 1 shows a schematic block diagram of one embodiment of a transmitter node that may be advantageously used in a radio frequency based sensing arrangement according to the present invention. [Diagram 5] FIG. 1 illustrates a flow diagram of one embodiment of a method for operating a controller suitable for controlling a radio frequency based sensing arrangement in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] 1 shows a schematic block diagram of one embodiment of a radio frequency (RF) based sensing arrangement 150 in accordance with the present invention. In this particular example, the RF based sensing arrangement is implemented as part of a lighting arrangement that includes a lighting device and associated devices such as a switch, a sensor, etc. Typically, a control signal from the switch or sensor is provided wirelessly to the lighting device (directly or via a control device such as a router, access point, bridge, etc.) to control the operation of the lighting device, e.g., turning the lighting unit on or off, changing the light color or light intensity of the lighting unit, etc.

[0047] The professional and commercial lighting market is moving toward wirelessly connected lighting systems that enable all kinds of new capabilities such as remote scheduling, energy monitoring, sensor-based lighting control, indoor location services and asset management.

[0048] The use of presence sensors makes it possible to reduce the power consumption of the lighting system by turning on the lights only when people are present and dimming or even turning off sections where no people are present. Typically, dedicated sensors are used for presence detection, using methods such as passive infrared PIR, ultrasonic or radar. More recently, it has been found possible to detect people by analyzing the time evolution of signal quality values, such as the strength of the received signal, from wireless communication between radios in a wireless control network of LightPoints using the Zigbee mesh protocol, or bidirectional communication between a Wi-Fi router and a Wi-Fi light. RF-based presence sensing can also be performed using Wi-Fi communication between devices, such as lighting devices, where a first device provides a communication signal, which can be a beacon signal, and the other device monitors or "sniffs" how the signal behaves during propagation. This has the advantage that no additional hardware components are required and therefore the presence sensing functionality can be provided at a lower cost than using conventional sensors.

[0049] The RF-based sensing arrangement 150 is configured to detect activity in a sensing volume V using a wireless communication signal S. In this example, the activity is limited to the presence or movement of a subject or object in the sensing volume V. However, activity in the sense of this disclosure is not limited to the presence and movement detection of a subject or object in the sensing volume. It may also include other activities related to a subject, such as breathing rate, heart rate, fall detection, gestures, facial expressions, etc. The sensing volume V is a region of space in which the fluctuations of a certain wireless signal or communication link parameter, such as a radio frequency signal strength indicator or channel state information, can be associated with a given activity, or in other words, a given activity is correlable to the fluctuations of the certain signal or communication link parameter. Thus, the sensing volume V depends on the relative locations of the nodes involved in the communication and the surrounding environment, which affects the multipath behavior of the provided wireless communication signal. The RF-based sensing arrangement 150 includes a transmitter node 152, such as a sensor or a switch or a lighting device, configured to provide a wireless communication signal S according to a wireless communication protocol, such as BLE. The transmitter node is operable in an active mode in which a wireless communication signal S is provided and in a sleep mode in which no wireless communication signal is provided. The RF-based sensing arrangement 150 also includes one receiver node 154, e.g., a lighting device having a wirelessly controllable lighting unit 155, configured to receive the transmitted wireless communication signal S. Furthermore, the RF-based sensing arrangement includes a controller 100 configured to control the operation of the transmitter node 152 and the receiver node 154 to determine a preferred amount of transmission power Pmin indicative of a minimum transmission power of the wireless communication signal S provided by the transmitter node 152 that results in a reliable communication link CL for wireless communication between the transmitter node 152 and the receiver node 154.The controller 100 is further configured to control the operation of the transmitter node 152, and optionally also the receiver node, in accordance with a signal providing schedule AM, SM that alternates between active cycles, during which the transmitter node 152 is operated in an active mode AM, and sleep cycles, during which the transmitter node 152 is operated in a sleep mode SM, and in the active mode, the wireless communication signal is provided at the determined preferred transmission power amount Pmin.

[0050] Among other things, the controller 100 includes a communication unit 101 for communicating with the transmitter node 152, and optionally with the receiver node 154, either directly or via another device such as a router, an access point, a gateway or any other device. The controller also includes a processing unit 103 for generating appropriate operating instructions to be provided to the transmitter node 152 and, if necessary, the receiver node 154, via the communication unit 101, for ascertaining or determining a signal provisioning schedule, for determining a preferred transmit power budget Pmin, and for operating the transmitter nodes in accordance with the signal provisioning schedule AM, SM.

[0051] 2 shows a time diagram illustrating signal exchanges between a transmitter node and a receiver node of an RF-based sensing configuration, such as the transmitter node 152 and the receiver node 154 of the RF-based sensing configuration 150 of FIG. 1. The diagram illustrates a transmission power measure PTx of a wireless communication signal S provided by the transmitter node 152 and a corresponding signal quality value SQRx of a received wireless communication signal at the receiver node 154. For example, the signal quality values ​​SQ1, SQ2, and SQ3 are received signal strength indicators RSSI, which are indications of the amount of power associated with the respective wireless communication signals S1, S2, S3 arriving at the receiver node 154. To determine the preferred amount of transmission power Pmin, the controller is configured to control the transmitter node to provide a set of wireless communication signals S1, S2, S3 with different, in this particular case decreasing, transmission powers P1, P2, P3, to ascertain the signal quality values ​​SQ1, SQ2, SQ3 of the wireless communication signals received at the receiver node 154, and to select as the preferred amount of transmission power Pmin the lowest transmission power from the transmission powers P1, P2 of the set of wireless communication signals S1, S2, S3 that results in a signal quality value SQ1, SQ2 above the signal quality threshold SQth. In the example shown in Fig. 2, the determination of the preferred amount of transmission power Pmin is performed in a commissioning phase CP, which is typically performed before the operation of the RF-based sensing arrangement. The controller instructs the transmitter node to provide a set of three wireless communication signals S1, S2, S3, each having a respective transmission power amount P1, P2, P3. The fact that in this example three signals S1, S2, S3 are provided should not be understood as a limitation. The number of signals is arbitrary, and the more signals there are with different (especially decreasing) transmission powers, the higher the chance of determining a preferred amount of transmission power equal to the theoretical minimum for a reliable communication link. Signal S1 is received at receiver node 154, and the RSSI value of SQ1 that exceeds a threshold SQth is determined.S2 is received at the receiver node 154 and an RSSI value of SQ2 is determined, which is lower than SQ1 but above a threshold SQth. Finally, S3 is received at the receiver node 154 and an RSSI value of SQ3 is determined, which is lower than both SQ1 and SQ2 and lower than a threshold SQth. The values ​​SQ1, SQ2 and SQ3 are sent to a controller, which determines, based on the thresholds, that the transmit power P2 at which the signal S2 is provided is the preferred amount of transmit power Pmin for the communication link, i.e., the link between the transmitter node 152 and the receiver node 154. The preferred transmit power can be determined in a commissioning phase under known and controlled parameters, especially for a known number of subjects (which may include no subjects) and known positions and / or movements within the sensing volume. Depending on these parameters and the surrounding environment, the metrics (e.g., RSSI, CSI, etc.) for determining the reliability of the communication link have different values. This is because activities performed by the subject (presence, movement, gestures, breathing, heartbeat, etc.) may affect the wireless communication signal as it propagates, changing the value of the selected metric. In some exemplary RF-based sensing configurations, particularly when the preferred transmit power is determined using a threshold associated with low occupancy of the sensing volume (e.g., absence of a subject), the preferred amount of transmit power includes sufficient headroom above the threshold to ensure reliable communication in situations where the subject is present in the sensing volume. In other examples, the threshold SQth may change over time, for example, may be different, preferably increased, to ensure reliable communication of the wireless communication signal when significant activity is detected in the sensing volume.

[0052] In an RF-based sensing configuration with more than one transmitter node and / or receiver node, this procedure can be performed for each communication link. The controller 100 then controls the operation of the transmitter node 152 according to a signal provision schedule SP that alternates between active cycles, during which the transmitter node is operated in an active mode AM, and sleep cycles, during which the transmitter node is operated in a sleep mode SP, in which the wireless communication signals Sa, Sb, Sc, KA are provided at the determined preferred transmission power amount Pmin. Sa, Sb, Sc are, for example, wireless communication signals for controlling the operation of the lighting units 155 of the lighting devices 154. The signal quality values ​​SQa, SQb, SQc, SQKA associated with the wireless communication signals Sa, Sb, Sc, KA provided by the transmitter node 152 are used by the activity determination unit 105. The activity determination unit 105 is configured to ascertain signal quality values ​​of wireless communication signals received by the receiver node 154 and to use the ascertained signal quality values ​​of the received signals to determine activity within the sensing volume V, typically by comparing the received signal quality, either directly or via a predefined function, to a threshold value for activity determination. The signal quality values ​​used are correlable to activity within the sensing volume V.

[0053] The activity determination unit 105, in this particular example, is incorporated into the controller 100. In another example, the activity determination unit is incorporated into a receiver node, the receiver node being configured to provide an activity signal indicative of the detection or non-detection of activity within the sensing volume.

[0054] The controller 100 is further configured to control the operation of the transmitter node to provide at least one keep-alive signal KA as a wireless communication signal in each active cycle during operation in the active mode according to the signal providing schedule. This is illustrated in FIG. 2. During a first active cycle AM1 of the active mode AM, a signal Sa is provided, which includes a payload indicating the operation or state of the transmitter node. During a second active cycle AM2 of the active mode AM, signals Sb and Sc are provided, each having a respective payload. However, during a third active cycle AM3, the transmitter node does not need to transmit a wireless communication signal, in which case the transmitter node is instructed by the controller to provide a keep-alive signal KA in order to keep the communication link between the transmitter node and the receiver node. Thus, a keep-alive signal is a communication signal sent by one device to another device to check that the communication link between the two devices is working or to prevent the communication link from being broken.

[0055] 3 illustrates a time diagram showing signal exchanges between a transmitter node and a receiver node of an RF-based sensing configuration, such as the transmitter node 152 and the receiver node 154 of the RF-based sensing configuration 150 of FIG. 1. The diagram illustrates a transmit power amount PTx of a wireless communication signal S provided by the transmitter node 152 and a corresponding signal quality value SQRx of a received wireless communication signal at the receiver node 154. In this example, the transmitter node is configured to provide wireless communication signals using multiple communication channels Ch1, Ch2, each associated with a respective frequency band f1, f2. In an active mode, the transmitter node 152 is operated to provide wireless communication signals Sa, Sb, Sc using the communication channel Ch2 with the lowest preferred transmit power amount determined and using the determined preferred transmit power amount Pmin. Thus, during the commissioning phase, the controller 100 controls the transmitter node 153 to provide one or more wireless communication signals at a corresponding transmit power amount for each of the communication channels Ch1, Ch2 available to the transmitter node. For example, the transmitter node is controlled to provide wireless communication signals S11, S21, S31 having respective power amounts P1, P2, P3 using a first channel Ch1. The signal quality values ​​of these signals received by the receiver node 154 are SQ11, SQ21, and SQ31. Thus, the preferred amount of transmit power associated with channel 1 is P1 because only the associated signal quality value SQ11 is above the threshold SQth. The transmitter node 152 is instructed to provide wireless communication signals S12, S22, S32 using communication channel Ch2. These providings are shown to occur after the providings of S11, S21, S31. However, the providings of S12, S22, and S32 may occur simultaneously. Also, the amount of transmit power of signals S12, S22, and S32 are shown to be equal to the amount of transmit power of signals S11, S21, and S31. However, in other examples, the amount of transmit power used for different channels may be different.The receiver node 154 receives wireless communication signals S12, S22 and S32 having associated signal quality values ​​of SQ12, SQ22 and SQ32, respectively. For channel 2, the preferred amount of transmission power is P2, which is lower than the preferred transmission value P1 of channel 1. Therefore, the controller 100 is configured to control the operation of the transmitter node 154 in an operation phase OP according to a signal provision schedule SP that alternates between active cycles AM1, AM2, during which the transmitter node 152 is operated in an active mode AM, and sleep cycles SM, during which the transmitter node is operated in a sleep mode, and in which the wireless communication signals Sa, Sb, Sc are provided with the determined preferred amount of transmission power P2.

[0056] To improve the use of power resources, signal communication in an RF-based sensing configuration is performed in a wireless communication protocol that allows the transmitter node 152 (e.g., a sensor or a switch) to operate in a sleep mode SM for part of the time using a time synchronization protocol. The transmitter node wakes up only at agreed moments to send / receive radio packets, operates in an active mode AM, and then goes to sleep again. An example of such an RF protocol is Bluetooth Low Energy (BLE). A BLE device can connect to another BLE device and maintain this connection by sending very short ("empty") packets, also called keep-alive signals, between the transmitter node and the receiver node. When setting up the initial connection, the devices agree on which time intervals to use to communicate and on which set of frequencies to communicate. In-between these connection intervals, the transmitter node, and optionally also the receiver node, sleeps and wakes up only immediately before the next connection interval. Preferably, the sleep cycle is at least 50% of the operating time, preferably at least 90%, more preferably at least 99%, even more preferably at least 99.9%, and most preferably at least 99.99%. In other words, when a full cycle is considered as the sum of an active cycle and consecutive sleep cycles, the sleep constitutes at least 50% of the full cycle, preferably at least 90%, more preferably at least 99%, even more preferably at least 99.9%, and most preferably at least 99.99%. As a result, there is a reduced demand for using power resources.

[0057] However, currently known RF-based sensing configurations implemented as lighting configurations have one disadvantage with respect to conventional sensors, namely that the sensor (i.e., radio) is necessarily co-located with the light point due to the fact that the radio must be always on to perform activity sensing while maintaining the wireless link used to control the lighting device. This limits the freedom of placement of the sensor and therefore can lead to sub-optimal detection of activity.

[0058] Operating a dedicated radio device on battery power is impractical for current RF sensing systems because the drain of a continuously active radio would quickly deplete the battery, resulting in inadequate battery life.

[0059] Providing suitable conditions, particularly a preferred duration of an active cycle compared to a full cycle, along with the use of a preferred amount of transmit power for transmitting wireless communication signals during the operating phase, the RF-based sensing configuration 150 enables the transmitter node to operate from a battery with sufficient life.

[0060] Notably, some implementations of RF-based sensing configurations can be made in this manner using a single battery-powered device as the transmitter node in combination with a mains-powered device as the receiver node, or using two or more battery-powered devices as transmitter and receiver nodes.

[0061] In the RF-based sensing configuration of Fig. 1, the transmitter node 152 is exemplarily represented as a battery-powered transmitter node, in particular a battery-powered switch or sensor, and can be located at any desired location suitable for performing RF-based activity sensing, substantially independent of the location of the lighting units (provided that a communication link between them is possible). The transmitter node 152 includes a battery unit 156 for providing operating power for operating the transmitter node. As a battery-powered node, the transmitter node is advantageously configured to use an ad-hoc connection between itself and the receiver node, which is a mains-powered device. This means that the battery-powered node is controlled by the controller to send out advertisements at regular intervals during active mode and to enter a sleep mode in the time between two active cycles. These advertisements or wireless communication signals are received by the mains-powered device, which can be configured to scan for a part of the time or all the time. In an exemplary RF-based sensing configuration, the mains powered device is also part of the mesh network, either as a sleepy end device or as a router. If the mains powered device is not functioning as a router device and is only an end device (sleepy or not), it can scan for BLE advertisements all the time. If the mains powered device is also selected to be a mesh router, it can only scan part of the time, which wastes some of the advertisements and makes the battery consumption of the battery powered device higher than it would otherwise be.

[0062] The fact that battery-powered nodes can be placed at any desired location means that they may be placed in cleverly chosen positions for RF-based activity sensing applications, such as on either side of a corridor (to detect people walking "through a signal path or multipath"), or between lamp posts in roadway lighting applications (to detect cars / cyclists / pedestrians walking "through a signal path or multipath"), or on either side of an entrance.

[0063] 4 shows a schematic block diagram of an embodiment of a transmitter node 200 that may be advantageously used in a radio frequency based sensing arrangement configured to detect activity in a sensing volume using wireless communication signals. The transmitter node includes a controller 100 and a transmitter 202 connected to the controller 100 and configured to provide wireless communication signals according to a predetermined wireless communication protocol, for example BLE. The transmitter node 200 may also be a transceiver node having both transmission and reception capabilities. The same is true for the transmitter node 152 and receiver node 154 of FIG. 1. Thus, the terms transmitter node and receiver node should be understood with respect to the origin and destination of a given wireless communication signal, and do not limit the capabilities of the respective nodes.

[0064] The controller 100 is configured to control the operation of the transmitter node and the receiver node to determine a preferred transmission power amount Pmin indicating a minimum transmission power of the wireless communication signal provided by the transmitter node that results in a reliable communication link for wireless communication between the transmitter node and the receiver node. For example, the controller 100 is configured to instruct the transmitter to provide the wireless communication signal at different transmission power amounts P1, P2, P3 and to wait for receipt of signal quality data SQ1, SQ2, SQ3 for the determination of the preferred transmission power amount. Furthermore, the controller 100 is configured to control the operation of the transmitter node according to a signal providing schedule SP alternating between active cycles during which the transmitter node is operated in an active mode AM and sleep cycles during which the transmitter node is operated in a sleep mode SM, and in the active mode the wireless communication signal is provided at the determined preferred transmission power amount Pmin.

[0065] Preferably, the transmitter node 200 is a battery-powered node further including a battery unit 156 for providing operating power. Furthermore, the transmitter node 200 optionally includes a battery control unit 158 ​​arranged and configured to ascertain power supply data PD indicative of a battery status of the battery unit 156 and to provide said power supply data PD to the controller 100.

[0066] Advantageously, whether or not the controller is incorporated in the transmitter node 200 (such as is the case for the transmitter node 152 of FIG. 1 ), the controller 100 is preferably further configured to ascertain (e.g., receive directly) power supply data indicative of the power supply status of the transmitter node or receiver node, and to vary the signal provision schedule depending on the ascertained power supply data.

[0067] If the battery control unit indicates via the power supply data that the transmitter device is beginning to drain its battery, the controller can be advantageously configured to skip some of the wireless communication signals, in particular some of the keep-alive signals provided to the receiver device, in order to stay alive as long as possible, allowing that device with a low battery to react with normal latency, while other devices will suffer longer latency.

[0068] In examples where both the transmitter and receiver nodes are battery powered nodes, the controller may be advantageously configured to control the alternating skipping of some of the keep-alive messages to conserve battery power. This is preferably agreed between both devices via the controller so that there is always at least one device sending out keep-alive packets every connection interval. Again, the length of the "shifts" may be negotiated based on which device's battery is best.

[0069] Whether incorporated into the transmitter node 200 of FIG. 4 or not (such as in FIG. 1), the controller 100 can be further configured to ascertain (e.g., receive or determine) activity data AD indicative of detection of activity in the sensing volume V, and to vary the signal provision schedule AM, SM depending on the ascertained activity data AD.

[0070] For example, the controller 100 may adapt the duration of the active and sleep cycles depending on whether activity (e.g., presence or movement of a subject in the sensing volume) is detected. The connection interval can be temporarily increased if presence is detected (by a short exchange between the controller and the transmitter node after the detection of activity) and restored to the original connection interval after a prescribed time.

[0071] Additionally or alternatively, the controller 100 may adapt the duration of the active and sleep cycles such that if no activity is detected for a predefined (long) time, the connection interval can be increased (accepting a somewhat longer latency in this case). After the first detection, the duration of the active and sleep cycles can be restored again.

[0072] 5 illustrates a flow diagram of an embodiment of a method 500 for operating a controller suitable for controlling a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the radio frequency based sensing arrangement including at least a transmitter node configured to provide wireless communication signals according to a wireless communication protocol and a receiver node configured to receive the provided wireless communication signals, where at least the transmitter node is operable in an active mode in which a wireless communication signal is provided and a sleep mode in which a wireless communication signal is not provided. The method includes controlling operation of the transmitter node and the receiver node in step 502 to determine a preferred transmission power amount Pmin indicating a minimum transmission power of a wireless communication signal provided by the transmitter node that provides a reliable communication link for wireless communication between the transmitter node and the receiver node, and controlling operation of at least the transmitter node in step 504 according to a signal providing schedule that alternates between active cycles in which the transmitter node is operated in an active mode and sleep cycles in which the transmitter node is operated in a sleep mode, where in the active mode the wireless communication signal is provided at the determined preferred transmission power amount. In one embodiment, controlling operation of at least the transmitter node 504 includes controlling operation of at least the transmitter node 504.1 to provide at least one keep-alive signal as a wireless communication signal in each active cycle during operation in an active mode according to the signal providing schedule.

[0073] In another embodiment, determining the preferred amount of transmit power 502 comprises the steps of: controlling 502.1 providing a set of wireless communication signals at different transmit powers; ascertaining 502.2 a signal quality value for each of the wireless communication signals received at the receiver node; and selecting 502.3 the lowest transmit power from the transmit powers of the set of wireless communication signals that results in a signal quality value above a signal quality threshold as the preferred amount of transmit power.

[0074] In another embodiment (not shown), the step of determining a preferred amount of transmit power is performed for a plurality of communication channels, each associated with a respective frequency band, and the method includes providing a wireless communication signal using the communication channel for which a lowest preferred amount of transmit power has been determined and using the determined preferred amount of transmit power.

[0075] In yet another embodiment, the method 500 additionally or alternatively includes step 506 of ascertaining activity data indicative of detection of activity in the sensing volume, and step 508 of altering the signal delivery schedule depending on the ascertained activity data.

[0076] In another embodiment, the method additionally or alternatively includes a step 510 of checking power supply data indicative of a power supply state of the transmitter node or the receiver node, and a step 512 of altering the signal provision schedule depending on the checked power supply data.

[0077] In summary, the present invention is directed to a controller for controlling a radio frequency based sensing arrangement including at least a transmitter node configured to provide a wireless communication signal and a receiver node configured to receive the provided wireless communication signal, where at least the transmitter node is operable in an active mode and a sleep mode. The controller is configured to determine a preferred amount of transmit power and to control operation of at least the transmitter node according to a signal providing schedule that alternates between active cycles during which the transmitter node is operated in an active mode and sleep cycles during which the transmitter node is operated in a sleep mode. In the active mode, the wireless communication signal is provided at the determined preferred amount of transmit power, thus enabling efficient use of power resources.

[0078] Other variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be effected in practicing the claimed invention.

[0079] In the claims, the word "comprise" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0080] A single unit or device may fulfill 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.

[0081] The computer program may be stored / distributed in 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 telecommunications systems.

[0082] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A controller for controlling a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the radio frequency based sensing arrangement including at least a transmitter node configured to provide the wireless communication signals according to a wireless communication protocol, and a receiver node configured to receive the provided wireless communication signals, at least the transmitter node being operable in an active mode in which the wireless communication signals are provided and in a sleep mode in which no wireless communication signals are provided, the controller comprising: controlling operation of the transmitter node and the receiver node to determine a preferred transmit power amount indicating a minimum transmit power of a wireless communication signal provided by the transmitter node that results in a reliable communication link for wireless communication between the transmitter node and the receiver node; and controlling operation of at least the transmitter node according to a signal provision schedule that alternates between active cycles, during which the transmitter node is operated in the active mode, and sleep cycles, during which the transmitter node is operated in the sleep mode, and in the active mode, the wireless communication signal is provided at the determined preferred transmit power amount. The controller is configured as follows:

2. 2. The controller of claim 1, wherein to determine the preferred amount of transmit power, the controller is configured to control providing a set of wireless communication signals at different transmit powers, ascertain signal quality values ​​for each of the wireless communication signals received at the receiver node, and select as the preferred amount of transmit power a lowest transmit power from among the transmit powers of the set of wireless communication signals that results in a signal quality value above a signal quality threshold.

3. 3. The controller of claim 1 or 2, wherein for a plurality of communication channels, each associated with a respective frequency band, a respective preferred amount of transmit power is determined, and in the active mode, the transmitter node is operated to provide the wireless communication signal using the communication channel for which a lowest preferred amount of transmit power has been determined and using the determined preferred amount of transmit power.

4. 4. The controller of claim 1, wherein the controller is configured to ascertain activity data indicative of detection of activity in the sensing volume, and to vary the signal provision schedule in dependence on the ascertained activity data.

5. 5. A controller as claimed in claim 1, wherein the controller is configured to check power supply data indicative of a power supply state of the transmitter node or the receiver node, and to vary the signal provision schedule in dependence on the checked power supply data.

6. 6. The controller of claim 1 , wherein the controller is configured to control operation of at least the transmitter node to provide at least one keep-alive signal as the wireless communication signal in each active cycle during operation in the active mode in accordance with the signal providing schedule.

7. 1. A transmitter node for a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the transmitter node comprising: A controller according to any one of claims 1 to 6; a transmitter coupled to the controller and configured to provide a wireless communication signal according to a predetermined wireless communication protocol; , the transmitter node.

8. The transmitter node of claim 7 , wherein the transmitter node includes a battery unit for providing operating power.

9. 9. The transmitter node of claim 8, comprising a battery control unit arranged and configured to ascertain power supply data indicative of a battery status of the battery unit and to provide the power supply data to the controller.

10. at least one transmitter node configured to provide a wireless communication signal according to a wireless communication protocol, the at least one transmitter node operable in an active mode in which the wireless communication signal is provided and in a sleep mode in which the wireless communication signal is not provided; at least one receiver node configured to receive the transmitted wireless communication signals; At least one controller according to any one of claims 1 to 6; an activity determination unit configured to ascertain a signal quality value of the wireless communication signal received by the receiver node, the signal quality value being correlable to activity within a sensing volume defined by a communication link between the transmitter node and the receiver node, and to determine activity within the sensing volume using the ascertained signal quality value; A radio frequency based sensing configuration comprising:

11. The radio frequency based sensing arrangement of claim 10 , wherein the activity determining unit is integrated into the receiver node.

12. 12. The radio frequency based sensing arrangement of claim 10 or 11, wherein the signal quality value is a received signal strength indicator indicative of a signal strength of the wireless communication signal received at the receiver node, or channel condition information indicative of a channel condition of a communication link between the transmitter node and the receiver node.

13. 1. A method for operating a controller suitable for controlling a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, the radio frequency based sensing arrangement including at least a transmitter node configured to provide the wireless communication signals according to a wireless communication protocol, and a receiver node configured to receive the provided wireless communication signals, wherein at least the transmitter node is operable in an active mode in which the wireless communication signals are provided, and in a sleep mode in which no wireless communication signals are provided, the method comprising: controlling operation of the transmitter node and the receiver node to determine a preferred transmit power amount indicating a minimum transmit power of a wireless communication signal provided by the transmitter node that provides a reliable communication link for wireless communication between the transmitter node and the receiver node; controlling operation of at least the transmitter node according to a signal provision schedule that alternates between active cycles, during which the transmitter node is operated in the active mode, and sleep cycles, during which the transmitter node is operated in the sleep mode, wherein in the active mode, the wireless communications signal is provided at the determined preferred amount of transmit power; A method comprising:

14. 14. The method of claim 13, wherein the step of controlling operation of at least the transmitter node comprises controlling operation of at least the transmitter node to provide at least one keep-alive signal as the wireless communication signal in each active cycle during operation in the active mode according to the signal providing schedule.

15. A computer program comprising instructions which, when executed by a controller, cause said controller to carry out the steps of the method according to claim 13 or 14.

Images