Controller for an RF-based sensing arrangement

Abstract

The invention relates to a controller (100) for controlling a radio frequency based sensing arrangement (150) comprising 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, wherein 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 the operation of at least the transmitter node in accordance with a signal provision schedule (SP) which alternates active periods in which the transmitter node is operated in the active mode and sleep periods in which the transmitter node is operated in the sleep mode. In the active mode, the wireless communication signal is provided with the determined preferred amount of transmit power, thereby enabling an efficient use of power resources.

Description

TECHNICAL FIELD

[0001] The present invention relates to a controller adapted to control a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals. The invention further relates to a transmitter node, a radio frequency based sensing arrangement, a method for operating a controller and a computer program product. BACKGROUND

[0002] Document WO 2021 / 243597 A1 describes a method, apparatus, and computer readable medium for wireless communication at 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 duration and transmits or receives wireless communications with a second wireless device in the frequency band during a second time duration. In one example, the wireless device or node can be in an idle mode or a discontinuous reception mode, where the wireless device can periodically monitor for communications from another device and can enter a sleep mode or low power mode for a duration between the periodic monitoring / transmissions. SUMMARY

[0003] It would be beneficial to enable more efficient use of power resources in wireless devices or nodes for use on a radio frequency based sensing arrangement.

[0004] According to a first aspect of the invention, a controller is described. The controller is adapted to control a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals. The radio frequency based sensing arrangement comprises 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 of providing wireless communication signals and a sleep mode or low power mode of not providing wireless communication signals. The controller of the first aspect of the invention is advantageously configured to control the operation of the transmitter node and the receiver node to determine a preferred amount of transmission power indicative of a minimum transmission power of the wireless communication signals provided by the transmitter node that results in a reliable communication link of the wireless communication between the transmitter node and the receiver node. The preferred amount of transmission power is thus a transmission power equal to or slightly greater than a transmission power threshold above which a reliable communication link is ensured, i.e. a link between the transmitter node and the receiver node in which information can be communicated between them within a predetermined quality, e.g. a bit rate, a bit error rate, a signal to noise ratio, or any other parameter known to the person of ordinary skill in the art for establishing reliability of a communication link.

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

[0006] The determination of the preferred amount of transmit power and the control of at least the transmitter node to provide the communication signal in the active mode only and with the preferred amount of transmit power enables a better use of the power resources in the radio frequency based sensing arrangement, in particular the power resources in the transmitter node.

[0007] In the following, embodiments of the first aspect of the invention will be disclosed.

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

[0009] The transmitter node and in some embodiments the receiver node can operate in an active mode in which wireless communication signals are provided and in a sleep mode or low power mode in which no wireless communication signals are provided. Thus, the active mode represents those time periods in which, if necessary, wireless communication signals can be provided, in particular wireless communication signals for determining activity in the sensing volume. For example, the transmitter node can delay the provision of wireless communication signals until it is operated in the active mode or even discard wireless communication signals if the expected transmission time coincides with the sleep mode in particular embodiments. During operation in the sleep mode, i.e. during any sleep period, no wireless communication signals are provided or at least no wireless communication signals for activity determination.

[0010] A radio frequency based sensing arrangement is configured to use wireless communication signals for detecting activity within a sensing volume. In the sense of the present disclosure, activity includes presence and movement detection of objects or bodies within the sensing volume. It can also include other object related activities such as respiration rate, heart rate, fall detection, hand gestures, facial expressions, etc. The sensing volume is a spatial region where changes in a certain signal or communication link parameter, e.g. a radio frequency signal strength indicator (RSSI) or channel state information (CSI), can be associated with a given activity or, in other words, a spatial region where a given activity can be associated with changes in a certain signal or communication link parameter. The sensing volume thus depends on the relative position of the transmitter node and the receiver node as well as the surrounding environment, which influences the multipath behavior of the provided wireless communication signals.

[0011] In a preferred embodiment, the predetermined wireless communication protocol is Bluetooth Low Energy (BLE). In alternative embodiments, the wireless communication protocol is Bluetooth, Wi-Fi, Thread, ZigBee or any other suitable wireless communication protocol known to the person of ordinary 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 comprises a transceiver unit configured to provide and receive wireless communication signals, in particular according to the predetermined wireless communication protocol. The controller advantageously wirelessly provides instructions 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, to the receiver node or to both the transmitter node and the receiver node. Using the respective link (wired or wireless), the controller controls the operation of the transmitter node and the receiver node, e.g. sending operation instructions from and receiving operation data to the receiver node, which enables determining the preferred amount of transmit power. The controller is further configured to determine or ascertain a signal provision schedule depending on the operating conditions of the radio frequency based sensing arrangement, which can be predetermined and can be updateable. In particular, the controller comprises a communication unit for communicating with the transmitter node and the receiver node, directly or via another device, and a processing unit for ascertaining or determining the signal provision schedule and generating suitable operation instructions to provide to the transmitter node and, if necessary, to the receiver node via the communication unit, for determining the preferred amount of transmit power and operating the transmitter node according to the signal provision schedule.

[0013] The preferred amount of transmit power is a transmit power equal to or slightly greater than a transmit power threshold above which a reliable communication link is ensured. In one embodiment, the preferred transmit power is determined during the commissioning phase, under known and controlled parameters, in particular with a known number of objects, which can not include the object, and a known position and / or movement within the sensing volume. Depending on these parameters and the surrounding environment, a metric for determining the reliability of the communication link (e.g. RSSI, CSI, etc.) has different values, as the activities performed by the object (presence, movement, gestures, breathing, heartbeat, etc.) can affect the wireless communication signal when it propagates, thus changing the value of the selected metric. In some embodiments, in particular in case the preferred transmit power is determined from parameters associated with a low occupancy of the sensing volume (e.g. where no object is present), the transmit power threshold comprises a sufficient headroom to ensure reliable communication in case an object is present in the sensing volume. In other embodiments, the transmit power threshold can vary over time, for example, in case significant activity is detected in the sensing volume, the transmit power threshold is different, preferably, the transmit power threshold is increased in order to ensure reliable communication of the wireless communication signal.

[0014] In one embodiment, to determine the preferred amount of transmit power, the controller is configured to control, preferably at different points in time, the provision of a set of wireless communication signals with different transmit powers, to ascertain respective signal quality values of the wireless communication signals received at the receiver node, and to select, from the transmit powers of the set of wireless communication signals, the lowest transmit power that results in a signal quality value above a signal quality threshold as the preferred amount of transmit power. Examples of suitable signal quality parameters include a received signal strength indicator (RSSI) of the wireless communication signal received at the receiver node, channel state information related to the communication link between the transmitter node and the receiver node, signal-to-noise ratio, or any other suitable parameter known to the person of ordinary skill in the art. Channel state information refers to the channel properties of the communication link and indicates how the signal propagates from the transmitter node to the receiver node and represents the combined effect of several parameters such as scattering, fading, and power decay with distance. Preferably, the transmit power is decreased gradually. The probability of determining the preferred amount of transmit power, which is the minimum amount of transmit power necessary for an arbitrarily close reliable communication link, increases with the number of communication signals in the set of wireless communication signals.

[0015] In a particular embodiment, in which the transmitter node is configured to provide wireless communication signals in two or more frequency bands, a respective preferred transmit power amount is determined for a plurality of communication channels, each communication channel being associated with a respective frequency band in which the transmitter node is operable to provide wireless communication signals. In this embodiment, in the active mode, the transmitter node is operated to provide wireless communication signals using the communication channel for which the lowest preferred transmit power amount has been determined and using the determined preferred transmit power amount. The controller can ascertain a signal quality value (e.g. RSSI) associated with each wireless communication signal received in each channel and then limit the communication between the transmitter node and the receiver node in the active mode to that or those communication channel(s) having the lowest preferred transmit power amount.

[0016] As mentioned above, the signal provision schedule, i.e. the temporal distribution of the active and sleep periods, respectively, can be updated or modified with respect to the initial signal provision schedule to match the current needs of the radio frequency-based sensing arrangement. In a particular embodiment, the controller is further configured to ascertain activity data indicative of detections of activity in the sensing volume and to change the signal provision schedule depending on the ascertained activity data. For example, when no activity (e.g. presence or movement) is detected, the duration of the active and / or sleep periods can be increased or decreased. After activity detection, the previous delay, i.e. the temporal duration of the active and sleep periods, can be restored by the controller, which controls the operation of the transmitter node according to the appropriate signal provision schedule.

[0017] In yet another embodiment, the controller is additionally or alternatively configured to ascertain power supply data indicative of a power supply state of the transmitter node or the receiver node and to change the signal provision schedule depending on the ascertained power supply data. This is particularly applicable in case of using a battery-powered transmitter node or receiver node, i.e. not connected to a mains or any other long-term power supply. In this particular example, the power supply data is indicative of a battery state, 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. If the power supply data is indicative of the available power being depleted or being below a predetermined amount of power threshold, the controller is configured to adjust the signal provision schedule accordingly, e.g. by reducing the duration of the active periods or even by eliminating some of these active periods. Additionally or alternatively, it can also control the operation of the transmitter node in a way that some of the wireless communication signals are not transmitted.

[0018] In another embodiment, the controller is additionally or alternatively configured to control operation of at least the transmitter node such that it provides at least one keep-alive signal as a wireless communication signal in each active period during operation in the active mode according to the signal-provision schedule. This is particularly advantageous in embodiments where BLE is used as the wireless communication protocol. In order to maintain the communication link, the transmitter node needs to provide a radio packet within a given time window. The signal-provision schedule is adapted to this time window such that there is always an active period in the given time window. Advantageously, the controller ensures that the transmitter node provides a keep-alive signal, thereby maintaining the communication link, if the transmitter node does not have to provide a wireless communication signal in the frame of its normal operation. The keep-alive signal is thus a communication signal sent by one device to another device to check whether the communication link between the two devices is operating or to prevent the communication link from breaking.

[0019] According to a second aspect of the present application, a transmitter node is disclosed. The transmitter node is adapted for a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals. The transmitter node comprises a controller according to the first aspect of the present application and a transmitter connected 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 such that the connection between the controller and the transmitter is established within a shared housing and, preferably but not necessarily, in a wired manner.

[0021] The transmitter node of the second aspect thus shares the advantages of the controller of the first aspect of the present application.

[0022] In the following, embodiments of the transmitter node of the second aspect of the present application will be described.

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

[0024] In another embodiment, the transmitter node further comprises a battery unit for providing operational power. It has been generally accepted that running a dedicated radio on battery power is not practical for current RF based sensing applications as the consumption of a continuously active radio would quickly deplete the battery unit, resulting in insufficient lifetime. However, by means of the controller according to the first aspect of the present application, in particular the controller integrated within the transmitter node, the control of the operation of the transmitter node enables an increased lifetime 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 state of the battery unit and to provide said power supply data to the controller. In particular, the controller is advantageously configured to receive the power supply data and to change the signal provision schedule in dependence on the received power supply data.

[0026] A third aspect of the present application is formed by a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals. The radio frequency based sensing arrangement comprises at least one transmitter node configured to provide wireless communication signals according to a wireless communication protocol, wherein the at least one transmitter node is operable in an active mode of providing wireless communication signals and in a sleep mode of not providing wireless communication signals. The radio frequency based sensing arrangement further comprises 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 present application. In particular, the controller can be integrated in the transmitter node, thereby forming a transmitter node according to the second aspect of the present application. Additionally or alternatively, the controller can be integrated in the receiver node, thereby forming an additional aspect of the present application.

[0027] The radio frequency based sensing arrangement further comprises an activity determination unit configured to ascertain a signal quality value of the wireless communication signals received by the receiver node, which signal quality value can be related 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] Hence, the radio frequency based sensing arrangement of the third aspect of the present application shares the advantages of the controller of the first aspect or the transmitter node of the second aspect.

[0029] In the following, embodiments of the radio frequency based sensing arrangement of the third aspect will be described.

[0030] In one embodiment, the activity determination unit is integrated in the receiver node, such that the receiver node determines the signal quality value, e.g. RSSI or CSI, and also determines the presence or absence of activity in the sensing volume. In another embodiment, in particular in embodiments in which the receiver node is a battery powered node, the activity determination unit is not integrated 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 the wireless communication signals. In an exemplary embodiment, the activity determination unit is a unit of an access point, a router or any other possible control device of the radio frequency based sensing arrangement. In another embodiment, both the transmitter node and the receiver node are controlled by the controller.

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

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

[0033] A fourth aspect of the invention is formed by a method for operating a controller, the controller being adapted to control a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals, and comprising at least a transmitter node configured to provide wireless communication signals in accordance with 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 of providing wireless communication signals and a sleep mode of not providing wireless communication signals. The method of the fourth aspect of the invention comprises the steps of:

[0034] controlling the operation of the transmitter node and the receiver node to determine a preferred amount of transmit power indicative of a minimum transmit power of the wireless communication signals provided by the transmitter node resulting in a reliable communication link of the wireless communication between the transmitter node and the receiver node; and

[0035] controlling the operation of at least the transmitter node in accordance with a signal provision schedule, the signal provision schedule alternating active periods in which the transmitter node is operated in the active mode and sleep periods in which the transmitter node is operated in the sleep mode, and wherein in the active mode the wireless communication signals are provided with the determined preferred amount of transmit power.

[0036] Hence, the method of the fourth aspect shares the advantages of the controller of the first aspect of the invention.

[0037] In the following, embodiments of the method according to the fourth aspect of the invention will be described.

[0038] In one embodiment, the step of determining the preferred amount of transmit power comprises the steps of controlling the provision of a set of wireless communication signals having different transmit powers, ascertaining respective signal quality values of the wireless communication signals received at the receiver node, and selecting from the transmit powers of the set of wireless communication signals the lowest transmit power resulting in a signal quality value above a signal quality threshold as the preferred amount of transmit power.

[0039] In another embodiment, the step of determining a preferred amount of transmit power is performed for a plurality of communication channels, each communication channel being associated with a respective frequency band, and wherein the method comprises providing the wireless communication signal 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.

[0040] In yet another embodiment, the method additionally or alternatively comprises ascertaining activity data indicative of detection of activity in the sensing volume, and changing the signal provision schedule in dependence on the ascertained activity data.

[0041] In yet another embodiment, the method additionally or alternatively comprises ascertaining power supply data indicative of a power supply state of the transmitter node or the receiver node, and changing the signal provision schedule in dependence on the ascertained power supply data.

[0042] In a preferred embodiment, the method additionally or alternatively comprises controlling operation of at least the transmitter node such that it provides at least one keep-alive signal as the wireless communication signal in each activity period during operation in the active mode according to the signal provision schedule. In particular, if an activity period is about to end and no wireless communication signal is provided, the method controls provision of the keep-alive signal in order to maintain a communication link between the transmitter node and the receiver node.

[0043] The method of the third aspect can be implemented by an access point, a router or any other possible control device comprising a controller of the radio frequency-based sensing arrangement, or by the transmitter node comprising the controller of the radio frequency-based sensing arrangement. In the former case, control of the transmitter node and the receiver node is performed wirelessly, preferably using a predetermined wireless communication protocol. Alternatively, control of the transmitter node and the receiver node can be done via a dedicated wired connection.

[0044] A fifth aspect of the present application is formed by a computer program product comprising instructions which, when the program is executed by the controller, cause the controller to carry out the steps of the method according to the fourth aspect.

[0045] It is to be understood that the controller of claim 1, the transmitter node of claim 7, the radio frequency-based sensing arrangement of claim 10, the method for operating a controller of claim 13 and the computer program of claim 15 have similar and / or identical preferred embodiments, in particular as defined in the dependent claims.

[0046] It is to be understood that preferred embodiments of the present application can also be any combination of the above described embodiments with corresponding independent claims.

[0047] These and other aspects of the present application will be apparent from and elucidated with reference to the embodiments described hereinafter. Attached Figure Description

[0048] In the following figures:

[0049] Figure 1 A schematic block diagram of an embodiment of a radio frequency (RF) based sensing arrangement according to the present invention is shown.

[0050] Figure 2 A first time-mapping diagram illustrating the signal exchange between a transmitter node and a receiver node in an RF-based sensing arrangement according to the present invention is shown.

[0051] Figure 3 A second timeline illustrating the signal exchange between a transmitter node and a receiver node in an RF-based sensing arrangement according to the present invention is shown.

[0052] Figure 4 A schematic block diagram is shown of an embodiment that can be advantageously used in a transmitter node in a radio frequency-based sensing arrangement according to the invention, and

[0053] Figure 5 A flowchart illustrating an embodiment of a method according to the present invention for operating a controller suitable for controlling a radio frequency-based sensing arrangement is shown. Detailed Implementation

[0054] Figure 1 A schematic block diagram of an embodiment of a radio frequency (RF)-based sensing arrangement 150 according to the present invention is shown. In this particular example, the RF-based sensing arrangement is implemented as part of a lighting arrangement that includes lighting devices and associated devices such as switches and sensors. Typically, control signals from switches or sensors are wirelessly provided to the lighting devices (directly or via control devices such as routers, access points, bridges, etc.) to control the operation of the lighting devices, such as turning the lighting units on or off, changing the color or intensity of the light from the lighting units, etc.

[0055] A continuing trend in the professional and commercial lighting market is the increasing shift towards wirelessly connected lighting systems that enable all sorts of new features, such as remote dispatching, energy monitoring, sensor-based lighting control, indoor positioning services, and asset management.

[0056] The use of presence sensors enables to reduce the power consumption of a lighting system by switching on the lights only when a person is present, and dimming or even switching off the parts where no person is present. Typically, to detect presence, dedicated sensors are used, using methods like passive infrared, PIR, ultrasound or radar. Recently, it has been found possible to detect a person by analyzing the temporal evolution of signal quality values, for example the strength of the received signal of the wireless communication between radios in a wireless controlled light point network using for example Zigbee mesh protocol, or the two-way 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 other devices monitor or "sniff" how the signal behaves during propagation. This has the advantage that no additional hardware components are necessary and thus the presence sensing functionality can be provided at lower cost than using traditional sensors.

[0057] The RF-based sensing arrangement 150 is configured to use the wireless communication signals S to detect activity within a sensing volume V. In the present example, the activity will be limited to the presence or movement of an object or an object within the sensing volume V. However, in the sense of the present disclosure, the activity is not limited to presence and movement detection of an object or an object within the sensing volume. It can also include other object related activities such as respiration rate, heart rate, fall detection, hand gestures, facial expressions, etc. The sensing volume V is a spatial region in which a change in a particular 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 spatial region in which a given activity can be associated with a change in a particular signal or communication link parameter. The sensing volume V is thus dependent on the relative positions of the nodes involved in the communication and on the surrounding environment, which influences the multipath behavior of the provided wireless communication signals. The RF-based sensing arrangement 150 comprises a transmitter node 152, e.g. a sensor or a switch or a lighting device, configured to provide wireless communication signals S according to a wireless communication protocol, e.g. BLE. The transmitter node can operate in an active mode of providing wireless communication signals S and in a sleep mode of not providing wireless communication signals. The RF-based sensing arrangement 150 further comprises a receiver node 154, e.g. a lighting device with a lighting unit 155 that is wirelessly controllable, configured to receive the transmitted wireless communication signals S. Furthermore, the RF-based sensing arrangement comprises a controller 100 configured to control the operation of the transmitter node 152 and the receiver node 154 to determine a preferred amount of transmit power Pmin indicative of a minimum transmit power of the wireless communication signals 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, according to a signal provision schedule AM, SM that causes the transmitter node 152 to alternate between an active period in which the transmitter node 152 operates in an active mode AM in which the wireless communication signals are provided with the determined preferred amount of transmit power Pmin and a sleep period in which the transmitter node 152 operates in a sleep mode SM.

[0058] In particular, the controller 100 comprises 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, access point, gateway or any other device. The controller further comprises a processing unit 103 for ascertaining or determining a signal provision schedule and generating appropriate operation instructions for providing to the transmitter node 152, and if needed to the receiver node 154, via the communication unit 101 for operating the transmitter node according to the signal provision schedule AM, SM for determining a preferred transmit power amount Pmin.

[0059] Figure 2 A time diagram illustrating a signal exchange between a transmitter node and a receiver node (e.g. Figure 1 of the RF-based sensing arrangement 150 of Fig. 1. The diagram shows the transmit power amount PTXof the wireless communication signals S provided by the transmitter node 152 and the respective signal quality values SQRXof the received wireless communication signals at the receiver node 154. For example, the signal quality values SQ1, SQ2and SQ3are received signal strength indicators RSSI which are an indication of the power amount associated with the respective wireless communication signals S1, S2, S3arriving at the receiver node 154. For determining the preferred transmit power amount Pmin, the controller is configured to control the transmitter node to provide a set of wireless communication signals S1, S2, S3with different (in this particular case decreasing) transmit powers P1, P2, P3to ascertain the respective signal quality values SQ1, SQ2, SQ3of the received wireless communication signals at the receiver node 154 and to select from the transmit powers P1, P2of the set of wireless communication signals S1, S2, S3the lowest transmit power resulting in signal quality values SQ1, SQ2above a signal quality threshold SQthas the preferred transmit power amount Pmin. In Figure 2In the illustrated example, the determination of the preferred amount of transmit power Pmin is done in a commissioning phase CP, 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 and S3, each having a respective amount of transmit power P1, P2 and P3. The fact that three signals S1, S2, S3 are provided in this example should not be understood as limiting. The number of signals is arbitrary and the more signals with different, in particular reduced, transmit power, the higher the chance to determine the preferred amount of transmit power equal to the theoretical minimum of a reliable communication link. Signal S1 is received at the receiver node 154 and a RSSI value SQ1 higher than a threshold SQth is determined. S2 is received at the receiver node 154 and a RSSI value SQ2 lower than SQ1 but still higher than the threshold SQth is determined. Finally, S3 is received at the receiver node 154 and a RSSI value SQ3 lower than both SQ1 and SQ2 and also lower than the threshold SQth is determined. The values SQ1, SQ2 and SQ3 are sent to the controller which then determines, based on the threshold, that P2 (the transmit power P2 at which signal S2 is provided) is the preferred amount of transmit power Pmin for this communication link, i.e. the link between the transmitter node 152 and the receiver node 154. The preferred transmit power can be determined in the commissioning phase from known and controlled parameters, in particular for a known number of objects (which can not include the object) and known positions and / or movements within the sensing volume. Depending on these parameters and the surrounding environment, the measure used to determine the reliability of the communication link (e.g. RSSI, CSI, etc.) has different values as the activities performed by the object (presence, movement, gestures, breathing, heartbeat, etc.) can affect the wireless communication signal when it propagates, thus changing the value of the selected measure. In some exemplary RF-based sensing arrangements, in particular in case the preferred transmit power is determined using a threshold associated with a low occupancy of the sensing volume (e.g. where no object is present), the preferred amount of transmit power includes a sufficient headroom above the threshold to ensure reliable communication in case an object is present in the sensing volume. In other examples, the threshold SQth amount can vary over time, e.g. it is different, preferably it increases in case significant activity is detected in the sensing volume, in order to ensure reliable communication of the wireless communication signal.

[0060] In an RF-based sensing arrangement with more than one transmitter node and / or receiver node, the procedure can be performed for each communication link. The controller 100 then controls the operation of the transmitter node 152 in accordance with the signal provision schedule SP which causes the transmitter node to alternate between an active period in which the transmitter node operates in an active mode AM and a sleep period in which the transmitter node operates in a sleep mode AM, and wherein in the active mode AM the wireless communication signals Sa, Sb, Sc, KA are provided with the determined preferred amount of transmit power Pmin. Sa, Sb and Sc are for example wireless communication signals for controlling the operation of lighting units 155 of a lighting device 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 which is configured to ascertain the signal quality values of the wireless communication signals received by the receiver node 154 to determine the activity within the sensing volume V using the ascertained signal quality values of the received signals, typically by comparing the received signal quality directly or via a predetermined function with a threshold value for activity determination. The used signal quality values can be related to the activity within the sensing volume V.

[0061] In this particular example, the activity determination unit 105 is integrated in the controller 100. In other examples, the activity determination unit is integrated in the receiver node which is then configured to provide an activity signal indicating the detection or non-detection of activity within the sensing volume.

[0062] The controller 100 is further configured to control the operation of the transmitter node such that it provides at least one keep-alive signal KA as a wireless communication signal in each active period during the operation in the active mode in accordance with the signal provision schedule. This is exemplarily shown in Figure 2 During a first active period AM1 of the active mode AM, the signal Sa is provided, the signal Sa comprising a payload indicating the operation or status of the transmitter node. During a second active period AM2 of the active mode AM, the signals Sb and Sc are provided, each signal having a respective payload. However, during a third active period AM3, the transmitter node does not need to transmit any wireless communication signal, and in this case, and in order to keep the communication link between the transmitter node and the receiver node, the controller instructs the transmitter node to provide a keep-alive signal KA. The keep-alive signal is thus a communication signal sent by one device to another device to check whether the communication link between the two devices is operating or to prevent the communication link from being interrupted.

[0063] Figure 3 A transmitter node and a receiver node exhibiting an RF-based sensing arrangement are shown (e.g. Figure 1a time diagram of a signal exchange between a transmitter node 152 and a receiver node 154 of an RF-based sensing arrangement 150. The diagram shows the amount of transmit power PTXprovided by the transmitter node 152 for the wireless communication signals S and the respective signal quality values SQRXof the received wireless communication signals at the receiver node 154. In this example, the transmitter node is configured to provide the wireless communication signals using a plurality of communication channels Chl, Ch2, each of which is associated with a respective frequency band fl, f2. In the active mode, the transmitter node 152 is operated to provide the wireless communication signals Sa, Sb, Sc using the communication channel Ch2for which the lowest preferred amount of transmit power has been determined and using the determined preferred amount of transmit power Pmin. Thus, during the commissioning phase, the controller 100 controls the transmitter node 152 to provide one or more wireless communication signals with a corresponding amount of transmit power for each communication channel Chl, Ch2available to the transmitter node. For example, the transmitter node is controlled to provide wireless communication signals Sll, S21 and S31 using the first channel Chl, which have respective amounts of power P1, P2 and P3. The signal quality values of these signals as received by the receiver node 154 are SQll, SQ21 and SQ31. Thus, the preferred amount of transmit power associated with channel 1 is P1, since only the associated signal quality value SQll is above the threshold value SQth. The transmitter node 152 is then instructed to provide wireless communication signals S12, S22 and S32 using the communication channel Ch2. The provision of these is shown to occur after the provision of Sll, S21 and S31. However, the provision of S12, S22 and S32 can also occur simultaneously. Furthermore, it is shown that the amount of transmit power of the signals S12, S22 and S32 is equal to the amount of transmit power of the signals Sll, S21 and S31. However, in other examples, the amount of transmit power for different channels can be different. The receiver node 154 receives the wireless communication signals S12, S22 and S32 with associated signal quality values SQ12, SQ22 and SQ32, respectively. For channel 2, the preferred amount of transmit power is P2, which is lower than the preferred transmit value P1 for channel 1. Thus, the controller 100 is configured to control the operation of the transmitter node 152 in the operational phase OP in accordance with a signal provision schedule SP, which causes the transmitter node 152 to alternate between active periods AM1, AM2 in which the transmitter node is operated in the active mode AM, in which the wireless communication signals Sa, Sb, Sc are provided with the determined preferred amount of transmit power P2, and sleep periods SM in which the transmitter node is operated in the sleep mode.

[0064] To improve the use of power resources, the signal communication within the RF-based sensing arrangement is done with a wireless communication protocol that allows the transmitter node 152 (e.g. a sensor or switch) to operate in sleep mode SM for a certain time using a time synchronization protocol. The transmitter node only wakes up at agreed times and operates in active mode AM to send / receive radio packets and then goes to sleep again. One example of such an RF protocol is Bluetooth Low Energy (BLE). BLE devices 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 interval between communications they will use and on which set of frequencies they will communicate on. In between these connection intervals, the transmitter node and optionally also the receiver node go to sleep, only waking up before the next connection interval. Preferably, the sleep period is at least 50%, preferably at least 90%, more preferably at least 99%, even more preferably at least 99.9%, and most preferably at least 99.99% of the operating time. In other words, and considering one full cycle (plus one active period and one consecutive sleep period), the sleep constitutes at least 50%, preferably at least 90%, more preferably at least 99%, even more preferably at least 99.9%, and most preferably at least 99.99% of one full cycle. This results in a less demanding way of using power resources.

[0065] However, the currently known RF-based sensing arrangements implemented as lighting arrangements have one disadvantage over traditional sensors, namely that the sensor (i.e. the radio) has to be co-located with the light point, due to the fact that the radio has to be on all the time in order to maintain the radio link for controlling the lighting device when performing active sensing. This limits the freedom of sensor placement and can thus result in suboptimal detection of activities.

[0066] Running a dedicated radio device on battery power is not practical for current RF sensing systems, as the consumption of a continuously active radio would quickly deplete the battery, resulting in insufficient lifetime.

[0067] Assuming the right conditions, in particular the preferred duration of the active period compared to the full cycle, and the use of a preferred amount of transmission power to transmit the wireless communication signals in the operating phase, the RF-based sensing arrangement 150 enables the transmitter node to be run on battery for a sufficient lifetime.

[0068] In particular, several embodiments of the RF-based sensing arrangement can be done in this way, which use a single battery-powered device as transmitter node in combination with a mains-powered device as receiver node, or use two or more battery-powered devices as transmitter and receiver nodes.

[0069] In Figure 1 The transmitter node 152 is exemplarily represented as a battery powered transmitter node, in particular a battery powered switch or sensor, which can be located in any desired location suitable for performing RF based activity sensing and which is basically independent of the location of the lighting units (assuming a communication link between them is possible). The transmitter node 152 comprises a battery unit 156 for providing operational power for operating the transmitter node. The transmitter node as a battery powered node is advantageously configured to use the temporary connection between itself and the receiver node, which is a mains powered device, for receiving the advertisements or wireless communication signals. This means that the battery powered node is controlled by the controller to send advertisements at regular intervals during the activity mode and to enter a sleep mode in the time between two activity periods. These advertisements or wireless communication signals are received by the mains powered device, which can be configured to scan at some or all times. In the exemplarily RF based sensing arrangement, the mains powered device is also part of the mesh network, either as a sleep end device or as a router. If it does not act as a router device, but only as an end device (sleeping or not), it can scan for BLE advertisements all the time. If the mains powered device is selected to also be a mesh router, it can only scan for a part of the time, which wastes some advertisements, resulting in a higher battery consumption in the battery powered device than would be possible otherwise.

[0070] The fact that the battery powered node can be placed in any desired location means that the battery powered node can be placed in a cleverly chosen location for the RF based activity sensing application, for example on both sides of a corridor (detecting people walking "through the signal path or multipath"), or between the lamp poles in a road lighting application (detecting cars / cycling people / pedestrians walking "through the signal path or multipath"), or on both sides of an entrance.

[0071] Figure 4 A schematic block diagram of an embodiment of a transmitter node 200 is shown, which can advantageously be used in a radio frequency based sensing arrangement configured to use wireless communication signals for detecting activity within a sensing volume. The transmitter node comprises 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 can also be a transceiver node having transmit and receive capabilities. This is equally applicable to Figure 1The terms "transmitter node" and "receiver node" are to be understood in relation to the origin and the destination of a given wireless communication signal and are not a limitation of the respective node capabilities.

[0072] The controller 100 is configured to control the operation of the transmitter node and the receiver node to determine a preferred transmit power amount Pmin indicative of a minimum transmit power of the wireless communication signal provided by the transmitter node resulting in a reliable communication link of the 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 with different transmit power amounts Pi, P2, and P3 and to wait for reception of signal quality data SQi, SQ2, SQ3 to determine the preferred transmit power amount. Further, the controller 100 is configured to control the operation of the transmitter node in accordance with a signal provision schedule SP, the signal provision schedule SP alternating an active period in which the transmitter node is operated in an active mode AM and a sleep period in which the transmitter node is operated in a sleep mode SM, and wherein in the active mode the wireless communication signal is provided with the determined preferred transmit power amount Pmin.

[0073] Preferably, the transmitter node 200 is a battery powered node, which further comprises a battery unit 156 for providing operating power. Further, the transmitter node 200 optionally comprises a battery control unit 158, which is 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.

[0074] Advantageously, and irrespective of whether the controller is integrated in the transmitter node 200, such as in the case of the transmitter node 152 of the Figure 1 The controller 100 is preferably further configured to ascertain or directly receive power supply data indicative of a power supply status of the transmitter node or the receiver node and to change the signal provision schedule in dependence on the ascertained power supply data.

[0075] If the battery control unit indicates via the power supply data that the transmitter device starts to run out of its battery, the controller can advantageously be configured to skip parts of the wireless communication signal, in particular some keep-alive signals provided to the receiver device, in order to stay alive as long as possible. In this case, the other device will experience a longer latency, but the device with lower battery power can still react with normal latency.

[0076] In an example where both the transmitter and receiver nodes are battery-powered, the controller can be advantageously configured to control the alternating skipping of some keep-alive messages to conserve battery power. This is preferably agreed upon between the two devices via the controller to ensure that at least one device always sends keep-alive packets in each connection interval. Again, here, the length of the "shift" can be negotiated based on which device has the best battery.

[0077] Regardless of whether controller 100 is integrated Figure 4 In transmitter node 200, such as in Figure 1 In this case, the controller 100 can be further configured to identify (e.g., receive or determine) detected activity data AD indicating activity in the sensing volume V, and to change the signal provided by the signal AM, SM depending on the identified activity data AD.

[0078] For example, controller 100 may adjust the duration of the activity cycle and sleep cycle depending on whether activity has been detected or sensed (e.g., the presence or movement of an object in the sensed volume). When activity is detected, the connection interval may be temporarily increased (by a short exchange between the controller and the transmitter node after activity is detected) and reduced back to the original connection interval after a specified time.

[0079] Alternatively or additionally, the controller 100 may adjust the duration of the activity cycle and sleep cycle so that when no activity is detected for a specified (long) period, the connection interval can be increased, in which case a slightly longer delay is accepted. After the first detection, the duration of the activity cycle and sleep cycle can be restored again.

[0080] Figure 5A flow chart illustrating an embodiment of a method 500 for operating a controller adapted to control a radio frequency based sensing arrangement configured to detect activity within a sensing volume using wireless communication signals and comprising 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 of providing wireless communication signals and a sleep mode of not providing wireless communication signals. The method comprises, in step 502, controlling operation of the transmitter node and the receiver node to determine a preferred transmit power amount Pmin indicative of a minimum transmit power of the wireless communication signals provided by the transmitter node resulting in a reliable communication link for wireless communication between the transmitter node and the receiver node; and in step 504, controlling operation of at least the transmitter node according to a signal provision schedule alternating active periods in which the transmitter node is operated in the active mode and sleep periods in which the transmitter node is operated in the sleep mode, and wherein in the active mode the wireless communication signals are provided with the determined preferred transmit power amount. In one embodiment, the step 504 of controlling operation of at least the transmitter node comprises the step of controlling 504.1 operation of at least the transmitter node such that it provides at least one keep-alive signal as the wireless communication signals in each active period during operation in the active mode according to the signal provision schedule.

[0081] In another embodiment, the step 502 of determining the preferred transmit power amount comprises the steps of controlling 502.1 provision of a set of wireless communication signals having different transmit powers, ascertaining 502.2 respective signal quality values of the wireless communication signals received at the receiver node, and selecting 502.3 from the transmit powers of the set of wireless communication signals the lowest transmit power resulting in a signal quality value above a signal quality threshold as the preferred transmit power amount.

[0082] In another embodiment (not shown), the step of determining the preferred transmit power amount is performed for a plurality of communication channels, each communication channel being associated with a respective frequency band, and wherein the method comprises providing the wireless communication signals using the communication channel for which the lowest preferred transmit power amount has been determined and using the determined preferred transmit power amount.

[0083] In yet another embodiment, the method 500 additionally or alternatively comprises the steps of ascertaining 506 activity data indicative of detection of activity in the sensing volume, and changing 508 the signal provision schedule in dependence on the ascertained activity data.

[0084] In another embodiment, the method comprises additionally or alternatively the steps of ascertaining 510 power supply data indicative of a power supply status of the transmitter node or the receiver node, and changing 512 the signal provision schedule in dependence on the ascertained power supply data.

[0085] In summary, the present application relates to a controller for controlling a radio frequency based sensing arrangement comprising at least a transmitter node configured to provide a wireless communication signal and a receiver node configured to receive the provided wireless communication signal, wherein 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 in accordance with a signal provision schedule alternating active periods in which the transmitter node is operated in the active mode and sleep periods in which the transmitter node is operated in the sleep mode. In the active mode, the wireless communication signal is provided with the determined preferred amount of transmit power, thereby enabling an efficient use of power resources.

[0086] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims.

[0087] In the claims, the word "comprising" does not exclude other elements or steps, and the

[0088] A single unit or device can 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.

[0089] A computer program can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state storage medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0090] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A controller (100) for controlling a radio frequency based sensing arrangement (150), the radio frequency based sensing arrangement (150) being configured to detect activity within a sensing volume (V) using wireless communication signals (S) and comprising at least a transmitter node (152) configured to provide wireless communication signals (S) according to a wireless communication protocol and a receiver node (154) configured to receive the provided wireless communication signals, wherein at least the transmitter node is operable in an active mode (AM) of providing wireless communication signals and a sleep mode (SM) of not providing wireless communication signals, the controller being configured to: - control operation of the transmitter node and the receiver node to determine a preferred transmit power amount (Pmin) indicative of a minimum transmit power of the wireless communication signals provided by the transmitter node, the minimum transmit power resulting in a reliable communication link for wireless communication between the transmitter node and the receiver node; and - control operation of at least the transmitter node according to a signal provision schedule (SP), the signal provision schedule alternating active periods in which the transmitter node is operated in the active mode and sleep periods in which the transmitter node is operated in the sleep mode, and wherein in the active mode the wireless communication signals are provided with the determined preferred transmit power amount.

2. The controller of claim 1, wherein, For determining the preferred transmit power amount, the controller is configured to control provision of a set of wireless communication signals (S1, S2, S3) having different transmit powers (P1, P2, P3) to find respective signal quality values (SQ1, SQ2, SQ3) of the wireless communication signals received at the receiver node and to select from the transmit powers of the set of wireless communication signals the lowest transmit power resulting in a signal quality value above a signal quality threshold (SQth) as the preferred transmit power amount.

3. The controller of claim 1, wherein, Respective preferred transmit power amounts (Pmin1, Pmin2) are determined for a plurality of communication channels (Ch1, Ch2), each communication channel being associated with a respective frequency band (f1, f2), and wherein in the active mode the transmitter node is operated to provide the wireless communication signals using the communication channel for which the lowest preferred transmit power amount has been determined and using the determined preferred transmit power amount.

4. The controller according to claim 1, further configured to find activity data (AD) indicative of detection of activity in the sensing volume and to change the signal provision schedule depending on the found activity data.

5. The controller according to claim 1, further configured to find power supply data (PD) indicative of a power supply state of the transmitter node or the receiver node and to change the signal provision schedule depending on the found power supply data.

6. The controller according to claim 1, further configured to control operation of at least the transmitter node such that it provides at least one keep-alive signal (KA) as the wireless communication signal in each active period during operation in the active mode according to the signal provision schedule.

7. A transmitter node (200) for a radio frequency based sensing arrangement, the radio frequency based sensing arrangement being configured to use wireless communication signals for detecting activity within a sensing volume, the transmitter node comprising: - a controller (100) according to claim 1 ; - a transmitter (202) connected to the controller (100) and configured to provide wireless communication signals according to a predetermined wireless communication protocol.

8. The transmitter node (200) according to claim 7, further comprising a battery unit (156) for providing operating power.

9. The transmitter node according to claim 8, further comprising a battery control unit (158) arranged and configured to ascertain power supply data indicative of a battery status of the battery unit (156) and to provide the power supply data to the controller.

10. A radio frequency based sensing arrangement (150) comprising: - at least one transmitter node (152) configured to provide wireless communication signals (S) according to a wireless communication protocol, wherein the at least one transmitter node is operable in an active mode (AM) of providing wireless communication signals and a sleep mode (SM) of not providing wireless communication signals; - at least one receiver node (154) configured to receive the transmitted wireless communication signals, - at least one controller (100) according to claim 1 ; and - an activity determination unit (105) configured to ascertain a signal quality value of the wireless communication signals 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.

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

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

13. A method (500) for operating a controller, the controller being adapted to control a radio frequency based sensing arrangement, the radio frequency based sensing arrangement being configured to use wireless communication signals for detecting activity within a sensing volume, and the radio frequency based sensing arrangement comprising 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 of providing wireless communication signals and a sleep mode of not providing wireless communication signals, the method comprising the steps of: - controlling (502) the operation of the transmitter node and the receiver node for determining a preferred amount of transmit power (Pmin) indicative of a minimum transmit power of the wireless communication signals provided by the transmitter node, the minimum transmit power resulting in a reliable communication link (CL) for wireless communication between the transmitter node and the receiver node; and and - controlling (504) operation of at least the transmitter node according to a signal provision schedule (SP), the signal provision schedule alternating an active period in which the transmitter node operates in an active mode and a sleep period in which the transmitter node operates in a sleep mode, and wherein in the active mode the wireless communication signal is provided with the determined preferred amount of transmit power (Pmin).

14. The method of claim 13, wherein, The step (504) of controlling operation of at least the transmitter node comprises controlling (504.1) operation of at least the transmitter node such that it provides at least one keep-alive signal as the wireless communication signal in each active period during operation in the active mode according to the signal provision schedule.

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

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