Asset tracking system

Abstract

The invention provides a target tag (10) for object tracking, wherein the target tag (10) is configured to detect listener beacon signals transmitted by a plurality of listener nodes (110), wherein the target tag (10) has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes (110), and wherein in a tag operation mode the target tag (10) is configured to: detect listener beacon signals and determine related listener beacon signal strengths; determine a tag transmission power based on the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and transmit a target beacon signal at the tag transmission power.

Description

TECHNICAL FIELD

[0001] The present invention relates to a target tag for object tracking. The present invention also relates to an asset tracking system. The present invention also relates to a method for calibrating a tag. The present invention also relates to a computer program product. BACKGROUND

[0002] For example, US20080224870 describes an apparatus and method for managing power of a radio frequency identification (RFID) tag. By measuring a power strength of a radio frequency (RF) signal received from an RFID reader and adjusting a level of transmission power based on the measured power strength of the signal, the apparatus for managing power of an RFID tag can effectively reduce power consumption of the RFID tag. Similarly, see also US2013 / 0337847A1. SUMMARY

[0003] An asset tracking system can typically comprise three types of field devices: (mobile) tags, listener nodes (or "anchors") and gateways. In such a system, tags can emit beacon signals, and listener nodes can detect incoming beacon signals sent by tags and take measurements (e.g. signal strength measurements). Measurements can typically be taken by multiple listener nodes, and listener nodes can send these results to a gateway from which they can be further processed, e.g. by further forwarding them to a positioning engine on a server or in the cloud. Listener nodes can be spatially distributed throughout a space in which tags are to be tracked to provide good coverage of that space, and tags can then be located based on signals from multiple listener nodes. For example, a position engine can estimate that a tag is closest to a listener node that recorded the highest signal strength for a beacon signal. Typically, a beacon signal of a target tag can be picked up by multiple listener nodes, each of which can report the relevant signal to a gateway, which requires some network capacity. Therefore, in asset tracking systems, especially those that are deployed with a dense grid of lighting and that operate with multiple target tags, it can be challenging to provide sufficient network capacity to carry all measurement results, i.e. the required network capacity can be very high if there is no meaningful reduction of communication.

[0004] While it can be recognized that a reduction in the measurement data, and thus a reduction in the required network capacity, can not result in a significant decrease in performance, a good way to select the listener nodes that need to report can not be readily available. In particular, the listener nodes can be distributed in space, and any coordination between them makes it such that selecting a few to report will require a communication bandwidth overhead. If not carefully designed, the overhead can cost more than the overhead saved by the listener nodes that do not report their measurement data. Furthermore, the target tags can operate inefficiently in terms of energy consumption, which can result in short battery life of the target tags.

[0005] It is therefore an aspect of the present invention to provide an alternative asset tracking system that preferably further at least partially obviates one or more of above-mentioned drawbacks. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. The invention is set out in the accompanying independent and dependent claims.

[0006] Thus, in a first aspect, the present application can provide a target tag for object tracking. The target tag can be configured to detect listener beacon signals emitted by a plurality of listener nodes (of an asset tracking system). The listener beacon signals can comprise one or more of transmission power related data and receiver sensitivity related data of the plurality of listener nodes. The target tag can also have access to transmission power related data and / or receiver sensitivity related data, in particular transmission power related data, or in particular receiver sensitivity related data, of the plurality of listener nodes. The tag can further be operating in a tag operation mode. In the tag operation mode, the target tag can be configured to perform one or more of a detection phase, a signal processing phase, and an execution phase. In the detection phase, the target tag can (be configured to) detect listener beacon signals (of the plurality of listener nodes) and can determine one or more of a related listener beacon signal strength, and transmission power related data and receiver sensitivity related data. In the signal processing phase, the target tag can (be configured to) determine a tag transmission power based on one or more of the related listener beacon signal strength, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of reached listener nodes. In the execution phase, the target tag can (be configured to) emit a target beacon signal at the tag transmission power. Thus, in a particular embodiment, the present application can provide a target tag for object tracking, wherein the target tag is configured to detect listener beacon signals emitted by a plurality of listener nodes, wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in a tag operation mode, the target tag is configured to: (i) detect listener beacon signals and determine a related listener beacon signal strength; (ii) determine a tag transmission power based on the related listener beacon signal strength, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of reached listener nodes; and (iii) emit a target beacon signal at the tag transmission power.

[0007] The target tag can provide the benefit of adjusting the tag transmission power based on (local) characteristics of the asset tracking system and the predetermined target number of reached listener nodes.

[0008] In an asset tracking system, it is common that the infrastructure listener nodes also periodically transmit respective listener beacon signals. This can serve the purpose that mobile central tags or mobile phones can use the listener beacon signals to determine their position themselves for indoor navigation applications. The target tag of the present invention can be configured to detect these listener beacon signals and determine based on the detected listener beacon signals an appropriate transmission power to reach a predetermined target number of listener nodes. Thus, the transmission power of the target tag can be adjusted to (on average) reach a number of listener nodes that fulfill a desired positioning accuracy, which can reduce the excessive communication of the listener nodes, as less listener nodes will have a relevant signal to report to the gateway, and can reduce the overhead communication between the listener nodes, and this can improve the battery life of the target tag, as the transmission power can be reduced. Thus, the present invention can provide a target tag that is configured to decide autonomously about its transmission power by detecting and measuring listener beacon signals from listener nodes.

[0009] Thus, the present invention can provide a target tag for object tracking, in particular for tracking objects in a space.

[0010] The term "target tag" (also referred to as "tag") can herein refer to an item that can be tracked, in particular a uniquely identifiable item, for example by being provided with a target tag identification. The target tag can in particular be connected to a (larger) object that is desired to be tracked, for example attached to the item, or for example worn by a person. For example, the target tag can comprise one or more of a sticker, a badge, a wristband, an implant, and a token. Further, the target tag can be configured to transmit a wireless signal, for example a radio beacon, or for example a Bluetooth Low Energy beacon. Typically, the target tag can be a mobile target tag.

[0011] The term "space" can herein refer to any space in which it can be desired to track the location of a target tag. The space can in particular comprise a building (part of), for example a shopping center, a factory or a hospital (part of). However, the space can also be located outside. For example, the space can comprise a leisure park or a farm. In embodiments, the term "space" can refer to an office, a shop, a warehouse, a theater, a reception area, a hospital, a nursing home, a hotel, a factory, an airport, a shopping center, a manufacturing plant, and a horticulture plant. The term space can refer to an indoor space or an outdoor space, in particular an indoor space. As will be clear to the skilled person, typically, the space is not comprised by the asset tracking system, i.e. the space is not part of the system.

[0012] In embodiments, the target tag can be configured to detect listener beacon signals transmitted by a plurality of listener nodes, in particular a plurality of listener nodes of an asset tracking system.

[0013] In particular, the plurality of listener nodes can (be configured to) transmit listener beacon signals, in particular periodically. In particular, each listener node of the plurality of listener nodes can transmit a (respective) listener beacon signal.

[0014] In further embodiments, the target tag can have access to transmission power related data and / or receiver sensitivity related data, in particular transmission power related data, or in particular receiver sensitivity related data, of the plurality of listener nodes.

[0015] The term "transmission power related data" can herein refer to data about the power with which a listener node transmits a listener beacon signal. In particular, with this data, the target tag can determine the signal strength loss that occurs when a listener beacon signal propagates from a respective listener node to the target tag, which can (substantially) be the same signal strength loss that can be expected when a target beacon signal propagates from the target tag to the respective listener node.

[0016] The term "receiver sensitivity related data" can herein refer to data about the minimum signal strength required by a listener node to detect and / or process an incident signal, e.g. a target beacon signal. In particular, with this data, the target tag can determine the minimum signal strength a target beacon signal can need to have when reaching a listener node in order for the listener node to detect the target beacon signal and / or to report a related signal.

[0017] The transmission power related data and the receiver sensitivity related data can both relate to hardware and software. For example, the hardware of a listener node can mean that the listener node can only detect a target beacon signal (when reaching the listener node) whose signal strength exceeds a threshold value. However, the listener node can also be configured to report a related signal only if the signal strength of the detected signal exceeds a second threshold value.

[0018] Thus, when the target tag has access to the data related to the transmission power, the data related to the receiver sensitivity, and the signal strength of the detected listener beacon signal, the target tag can determine, for each listener node, the transmission power that would be required for the listener node to detect a target beacon signal (and to report a related signal).

[0019] The phrase "has access to data" and similar phrases can herein refer to (i) having default data, (ii) having specific data, (iii) receiving default data, and / or (iv) receiving specific data. Thus, in embodiments, the transmission power related data can comprise default transmission power related data. In further embodiments, the transmission power related data can comprise specific transmission power related data, i.e. transmission power related data specific to one (or more) of the plurality of listener nodes. In further embodiments, the target tag can comprise a data carrier having stored thereon the transmission power related data. In further embodiments, the target tag can (be configured to) receive the transmission power related data during operation, e.g. in an operational mode, in particular via the listener beacon signals.

[0020] For example, the target tag can comprise a data carrier having stored thereon default transmission power related data indicating - by default - that the listener node is assumed to transmit the listener beacon signal at a power of 0 dBm. Thus, without further information, the target tag can determine the tag transmission power in the signal processing phase based on the assumption that the listener node emits the listener beacon signal at a power of 0 dBm. However, for example, the listener node can emit listener beacon signals comprising transmission power related data. In particular, each listener beacon signal can comprise specific transmission power related data about the power at which the (respective) listener beacon signal is emitted. Thus, in this example, the target tag detecting the listener beacon signal has access to the specific transmission power related data. In general, if the target tag has access to both the default and the specific transmission power related data about the listener node, the target tag will use the specific data in the signal processing phase. Thus, in the signal processing phase, for each listener node, the transmission power related data can be the specific transmission power related data, if available, and the default transmission power related data, if the specific transmission power related data is not available.

[0021] Similarly, in the signal processing phase, for each listener node, the receiver sensitivity related data can be the specific receiver sensitivity related data, if available, and the default receiver sensitivity related data, if the specific receiver sensitivity related data is not available.

[0022] In embodiments, the target tag can have a tag operating mode. The term “tag operating mode” especially refers to one operating mode of the tag. The term “operating mode” can also be indicated as “control mode”. The target tag, system or device or apparatus (see also further below) can perform an action in a “mode” or “operating mode” or “mode of operation”. Likewise, in a method, an action, phase or step can be performed in a “mode” or “operating mode” or “mode of operation”. This does not exclude that the target tag, system or device or apparatus can also be adapted to provide another control mode, or a plurality of other control modes. Likewise, this does not exclude that one or more other modes can be performed before and / or after performing this mode. However, in embodiments, a control system (see also further below) can be available which is adapted to provide at least the control mode. If other modes are available, the selection of such mode can especially be performed via a user interface, although other options, like performing a mode according to a sensor signal or (time) scheme, can also be possible. In embodiments, the operating mode can also refer to a target tag, system or device or apparatus which can only operate in a single operating mode (i.e. “on”, without further tunability).

[0023] The tag operating mode can comprise one or more of a detection phase, a signal processing phase, and an execution phase. In particular, the tag operating mode can comprise a detection phase, a signal processing phase, and an execution phase.

[0024] In the detection phase, the target tag can (be configured to) detect listener beacon signals (of the plurality of listener nodes) and determine a related listener beacon signal strength. In particular, the target tag can detect listener beacon signals (of at least a part of the plurality of listener nodes) and can determine a related listener beacon signal strength for each detected beacon signal.

[0025] The term “signal strength” can especially refer herein to a power present in a detected beacon signal. In particular, the signal strength can correspond to a received signal strength indication (RSSI). i ).

[0026] The term “related” in terms like “related listener beacon signal strength” can refer herein to a relationship between two characteristics, such as a relationship between a detected listener beacon signal and a determined related listener beacon signal strength, such as the related listener beacon signal strength being based (at least partially) on the (detection of) the listener beacon signal.

[0027] In the signal processing phase, the target tag can (be configured to) determine a tag transmission power based on the related listener beacon signal strength, transmission power related data, receiver sensitivity related data, and a predetermined target number of arrived listener nodes.

[0028] The term "predetermined target number" can herein refer to a target number of listener nodes to detect a target beacon signal (and report a related signal). The term "target number" can herein refer to a respective number as a target to be achieved, i.e. a target tag can be configured to reach (on average) a number of listener nodes as close as possible to the target number. In further embodiments, the predetermined target number can comprise a lower target number, i.e. a desired minimum number of listener nodes to reach. In further embodiments, the predetermined target number can comprise an upper target number, i.e. a desired maximum number of listener nodes to reach. The term "predetermined target number" can also refer to a plurality of predetermined target numbers, e.g. a lower target number and an upper target number. Thus, the predetermined target number can effectively provide a range of (acceptable) listener nodes to reach.

[0029] For example, the predetermined target number can be 3 (lower target number) - 5 (upper target number), and the target tag can also determine a transmission power based on related listener beacon signal strengths, transmission power related data and receiver sensitivity related data, such that based on the current information and at the current tag position, the target beacon signal will be detected by 3-5 listener nodes.

[0030] As an alternative to adjusting the tag transmission power, the target tag can also inform the plurality of listener nodes to adjust their desired threshold to receive and process the target beacon signal.

[0031] Thus, the present application can provide a target tag for object tracking. The target tag can be configured to emit a target beacon signal. The target tag can also be configured to detect listener beacon signals emitted by a plurality of listener nodes. In particular, each of the plurality of listener nodes can be configured to detect the target beacon signal and report a related target signal if a target signal strength of the target beacon signal exceeds a detection threshold. In embodiments, the target tag can have access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes. The target tag can have an operational mode, in particular wherein the operational mode comprises one or more of (the execution of) a detection phase, a signal processing phase, and an execution phase. The detection phase can comprise detecting the listener beacon signals and determining related listener beacon signal strengths. The signal processing phase can comprise determining a target beacon signal strength offset based on a predetermined target number of arrived listener nodes, the related listener beacon signal strengths, the transmission power related data, and the receiver sensitivity related data. The signal processing phase can also comprise determining one or more of (a) a (first) transmission power of the target beacon signal and (b) the detection threshold based on the target beacon signal strength offset. The execution phase can comprise executing one or more of (a) emitting the target beacon signal at the (first) transmission power and (b) informing at least a portion of the plurality of listener nodes to set a detection threshold (of the target tag) to the detection threshold.

[0032] Thus, in particular embodiments, the target tag can be configured to emit a target beacon signal, and wherein the target tag is configured to detect listener beacon signals emitted by a plurality of listener nodes, and wherein each of the plurality of listener nodes is configured to detect the target beacon signal and report a related target signal if a target signal strength of the target beacon signal exceeds a detection threshold, and wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in an operational mode, the target tag is configured to: detect the listener beacon signals and determine related listener beacon signal strengths; determine a target beacon signal strength offset based on a predetermined target number of arrived listener nodes, the related listener beacon signal strengths, the transmission power related data, and the receiver sensitivity related data; determine one or more of (a) a transmission power of the target beacon signal and (b) the detection threshold based on the target beacon signal strength offset; and execute one or more of (a) emitting the target beacon signal at the transmission power and (b) informing at least a portion of the plurality of listener nodes to set a detection threshold to the detection threshold.

[0033] Thus, if the target signal strength received by the target tag is higher than the detection threshold, the target tag can inform the plurality of listener nodes to only process the target beacon signal instead of determining that the target tag will arrive at the desired number of listener nodes with the tag transmission power.

[0034] This can provide the additional benefit that the target beacon signal can have a higher signal-to-noise ratio, as the tag transmission power can be kept at a higher level.

[0035] The term "detection threshold" can herein refer to a (software level) threshold of the listener nodes, wherein the listener nodes are configured to only report a related target signal in case the detected signal strength of the target beacon signal exceeds the detection threshold.

[0036] The target tag can in particular inform at least part of the plurality of listener nodes to set the detection threshold of the target tag to the detection threshold, i.e. the detection threshold can remain unchanged for any other signal, e.g. for other beacon signals.

[0037] The term "target beacon signal strength offset" can herein in particular refer to a signal strength difference (based on the information currently available to the target tag) that would lead to a predetermined target number of reached listener nodes reaching the target beacon signal. For example, if the target beacon signal strength offset is -10 dBm, then the tag transmission power can be reduced by 10 dBm, or the detection threshold can be increased by 10 dBm; or a combination of both can be performed to provide a total difference of 10 dBm, e.g. the tag transmission power is reduced by 5 dBm and the detection threshold is increased by 5 dBm.

[0038] In a further embodiment, the signal processing phase can comprise determining a transmission power of the target beacon signal based on the target beacon signal strength offset, and the execution phase can comprise emitting the target beacon signal at the transmission power.

[0039] In a further embodiment, the signal processing phase can comprise determining a detection threshold based on the target beacon signal strength offset, and the execution phase can comprise informing at least part of the plurality of listener nodes to set the detection threshold to the detection threshold.

[0040] A combination of adjusting the tag transmission power and adjusting the detection threshold is also possible. In particular, the target tag can even increase its tag transmission power and increase the detection threshold in order to provide a higher signal-to-noise ratio while taking into account the predetermined target number of n listener nodes.

[0041] In an embodiment, the target beacon signal can comprise the detection threshold, i.e. in an embodiment the target tag can be configured to (in the execution phase) inform via the target beacon signal at least part of the plurality of listener nodes to set the detection threshold to the detection threshold.

[0042] In embodiments, the present application can provide a target tag for object tracking, wherein the target tag is configured to detect listener beacon signals transmitted by a plurality of listener nodes, wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in a tag operation mode, the target tag is configured to: detect listener beacon signals and determine related listener beacon signal strengths; determine a tag transmission power and / or a receive signal strength threshold based on the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of listener nodes to reach; and transmit a target beacon signal at the tag transmission power and / or indicate in its target beacon signal a receive signal strength threshold to be applied at the listener when receiving (the target beacon signal). In particular, the operation mode can comprise determining a receive signal strength threshold based on the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and the predetermined target number of listener nodes to reach; and indicating in the target beacon signal a receive signal strength threshold to be applied at the listener when receiving.

[0043] In embodiments, the present application can provide a target tag for object tracking, wherein the target tag is configured to detect listener beacon signals transmitted by a plurality of listener nodes, wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in a tag operation mode, the target tag is configured to: detect listener beacon signals and determine related listener beacon signal strengths; determine a (receiver) detection threshold range (for each of the plurality of listener nodes) based on the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of listener nodes to reach; and transmit a target beacon signal comprising the detection threshold range, in particular to at least a portion of the plurality of listener nodes, more particularly to each of the plurality of listener nodes. In further embodiments, the target beacon signal, in particular the target beacon signal comprising the detection threshold range, can be arranged to enable (each of the) listener nodes (of the plurality of listener nodes) to set the (respective) receiver sensitivity to the detection threshold range.

[0044] It will be clear to the skilled person that the target tag can move (through space) and that the number of listener nodes that detect the target beacon signal emitted at a certain transmission power can vary depending on the position of the target tag. Hence, the target tag can determine the transmission power, inter alia, based on (local) measurements, and use this transmission power as the target tag moves (through space). For example, the target tag can select a tag transmission power according to which the tag beacon signal will reach four listener nodes according to its measurements at the current position. However, as the target tag moves through space, the tag beacon signal can also reach fewer or more listener nodes depending on its position, which can depend, inter alia, on whether the listener nodes are arranged in a regular or irregular pattern. In embodiments (see also below), the target tag can be configured to (re)perform the tag operating mode after moving more than a movement threshold, or the control system (of the asset tracking system) can instruct the target tag to (re)perform the tag operating mode. Moreover, in embodiments in which most of the listener nodes are arranged in a regular grid such that (re)performance of the tag operating mode can be limited - for example in embodiments in which the listener nodes are incorporated into a lighting system - the invention can be particularly beneficial.

[0045] In the execution phase, the target tag can emit the target beacon signal at the tag transmission power. Hence, the execution phase can comprise emitting the target beacon signal at the tag transmission power determined in the signal processing phase.

[0046] In particular, the target tag can (be configured to) remain in the execution phase until the restart operating mode (see below).

[0047] In further embodiments, in the execution phase, the target tag can (be configured to) periodically emit the target beacon signal (in the execution phase). In further embodiments, in the execution phase, the target tag can (be configured to) emit the beacon signal according to a regular period, for example every 15 minutes. However, in further embodiments, the target tag can emit the target beacon signal according to an irregular period, for example a period that varies with the time of day, or every time an external signal is received, or every time the target tag moves. For example, the target tag can comprise a (passive) RFID tag, and can emit the beacon signal upon receiving a (suitable) radio wave.

[0048] In further embodiments, the target tag can (be configured to) emit the target beacon signal (substantially) continuously.

[0049] The target beacon signal can comprise any type of signal that can be detected by multiple listener nodes. In embodiments, the beacon signal may, for example, comprise a wireless communication signal, such as a wireless communication signal selected from the group comprising a Bluetooth signal, a ZigBee (beacon packet) signal, a Wi-Fi (beacon packet) signal, a LoRa signal, an ultra-wideband packet signal, and a Thread signal. In embodiments, the target beacon signal can comprise one or more carrier frequencies, in particular a plurality of carrier frequencies. i The target beacon signal may, in particular, comprise a target tag identification code. The target tag identification code can be specific to the target tag and can be particularly suited to uniquely identifying the target tag. Thereby, different target tags can be distinguished and different (tagged) items can be (independently) tracked.

[0050] The target beacon signal may, in particular, comprise a target tag identification code. The target tag identification code can be specific to the target tag and can be particularly suited to uniquely identifying the target tag. Thereby, different target tags can be distinguished and different (tagged) items can be (independently) tracked.

[0051] The target beacon signal may, in particular, comprise a target tag identification code. The target tag identification code can be specific to the target tag and can be particularly suited to uniquely identifying the target tag. Thereby, different target tags can be distinguished and different (tagged) items can be (independently) tracked.

[0052] In embodiments, the target tag can be configured to determine, in particular in the signal processing phase, for each listener node of the plurality of listener nodes, one or more of: (i) a (respective) receiver sensitivity R i based on receiver sensitivity related data, (ii) a (respective) listener transmission power L i based on transmission power related data, and (iii) a (respective) signal strength S i based on the related listener beacon signal strength.

[0053] In further embodiments, the predetermined target number of arrived listener nodes can comprise an upper target number, in particular wherein the target tag can be configured to determine a tag transmission power T t such that for a plurality of listener nodes smaller or equal to the upper target number, T t ≥ R i + L i - S i In particular, the term L i - S i" can indicate an expected signal strength loss that can occur when the target beacon signal propagates from the target tag to the (i-th) listener node. Thus, in order for the target beacon signal to be detected (and / or processed) by the (i-th) listener node, the tag transmission power T t may need to be at least: the receiver sensitivity R i + the expected signal strength loss L i - S i . Since the predetermined target number comprises an upper target number, the formula T t ≥ R i + L i - S i should apply for less than or equal to the upper target number of listener nodes.

[0054] Similarly, in further embodiments, the predetermined target number of reached listener nodes can comprise a lower target number, wherein the target tag can be configured to determine the transmission power T t such that for greater than or equal to the lower target number of listener nodes of the plurality of listener nodes, the T t ≥ R i + L i - S i applies.

[0055] In further embodiments, the target tag can be configured to minimize the transmission power T t . Thus, the target tag can be configured to minimize the transmission power in view of the predetermined target number of listener nodes, in particular in view of the lower target number of listener nodes.

[0056] The transmission power T t may be chosen to account for some variation in the signal loss, for example. Thus, it can be desirable to choose T t slightly larger than the minimum value determined for reaching the predetermined (lower) target number. For example, the tag transmission power T t may be chosen such that the tag transmission power T t has an increased strength T a relative to the minimum required tag transmission power in view of the predetermined target number of reached listener nodes. Thus, T t may be chosen such that for greater than or equal to the lower target number of listener nodes of the plurality of listener nodes, the T t ≥ R i + L i - S i + T a applies, wherein the increased strength T ais at least 0.1 dBm, such as at least 0.2 dBm, in particular at least 0.5 dBm, such as at least 1 dBm, such as at least 2 dBm. In further embodiments, the increased strength T a may be at most 3 dBm, such as at most 2 dBm, in particular at most 1 dBm.

[0057] Upon detecting the listener beacon signal, the target tag can further (be configured to) determine an associated listener beacon signal quality. The term "signal quality" can herein specifically refer to the quality of the detected signal. In particular, the quality can be determined, e.g., by comparing the detected signal to an (ideal) s-shaped signal. The signal quality can be indicative of the amount of information / trustworthiness of the signal. The target tag can (be configured to) determine (or adjust) the predetermined target number of reached listener nodes based on the associated listener beacon signal quality. For example, the target tag can detect beacon signals of six listener nodes, wherein the two strongest signals have a poor signal quality. Thus, the target tag can, e.g., set the predetermined target number to 5, such that three listener nodes having a listener beacon signal with sufficient signal quality will detect the target beacon signal. Thus, in embodiments, in the tag operating mode, the target tag can (be configured to) determine the predetermined target number of reached listener nodes based on a predetermined signal quality requirement.

[0058] In further embodiments, the predetermined signal quality requirement can be changed by, e.g., a functionally coupled control system, such as a control system of the asset tracking system. In particular, the asset tracking system can inform the listener nodes that the predetermined signal quality will be adjusted to a different value, e.g., in view of positioning difficulties and / or the importance of tracking the associated object.

[0059] The term "signal quality" can herein specifically refer to the quality of the detected tag beacon signal. In particular, the quality can be determined, e.g., by comparing the detected target beacon signal to an (ideal) s-shaped signal. The signal quality can be indicative of how the amount of information / trustworthiness of the signal.

[0060] In embodiments, the lower target number can be at least 3, such as at least 4, in particular at least 5, such as at least 7. In general, a detection by three listener nodes can achieve a rather good target tag positioning. In further embodiments, the upper target number can be at most 20, such as at most 15, in particular at most 10, such as at most 8, in particular at most 5.

[0061] In embodiments, the target tag can be configured to (re-)perform the tag operation mode according to a scan frequency, e.g. at least every day or at least every few hours, at least every few minutes (e.g. at least every 5 minutes), or at least every 2 minutes, or at least every few seconds (e.g. at least every 10 seconds), or at least every two seconds (e.g. at least every second). In further embodiments, the scan frequency can be based on one or more of a movement of the (target tag), a battery life of the (target tag), and a predefined period. In particular, the target tag can have a predefined period for the scan frequency, e.g. about every 5 minutes, but can also be configured to adjust the scan frequency based on one or more of the movement and the battery life. In particular, the target tag can be configured to reduce the time until the next scan due to a movement, i.e. when the target tag moves - in particular when the target tag moves beyond a predefined movement threshold - the target tag can (be configured to) (at least temporarily) reduce the scan frequency. Similarly, the target tag can be configured to increase the time until the next scan based on a battery life, i.e. when the battery is running low - in particular when the battery life drops below a predefined battery threshold (e.g. below 15% of the full battery life, in particular below 5% of the full battery life) - the target tag can (be configured to) (at least temporarily) increase the scan frequency.

[0062] In further embodiments, the target tag can be configured to (re-)perform the tag operation mode upon receiving an (external) tag calibration signal. For example, the asset tracking system can be configured to send out a tag calibration signal (for the target tag) when the localization of the target tag is deemed to need improvement. For example, the target tag localization can have become more important due to the circumstances (the target can be associated with an expert that can be needed soon), the signal quality of the target beacon signal as detected by the listener nodes can be below a quality criterion, or the target beacon signal can no longer be sufficiently detected for localization (the target tag can have moved to a part of the space where the density of listener nodes is reduced). As will be clear to the person skilled in the art, further variations on this topic are possible.

[0063] As indicated above, the listener nodes can typically periodically emit listener beacon signals, in particular according to a reporting frequency. However, there can be asset tracking systems where the listener nodes do not periodically emit listener beacon signals, or where the time between listener beacon signals is relatively long. With regard to the latter, since the target tag operates in the detection phase can be relatively energy consuming, it can be undesirable to stay in the detection phase for a period of time in which every listener node should have emitted a listener beacon signal (according to their reporting frequency).

[0064] Thus, in embodiments, the target tag can (be configured to) emit a listener beacon signal request signal in the tag operation mode, in particular in the start-up phase. Thus, the tag operation mode can further comprise a start-up phase. In the start-up phase, the target tag can (be configured to) emit the listener beacon signal request signal, i.e. the start-up phase can comprise the target tag emitting the listener beacon signal request signal. The plurality of listener nodes can be configured to emit the listener beacon signal upon receiving the listener beacon signal request signal. Thus, thereby each listener node can emit the (respective) listener beacon signal in a short time window, which means that the target tag can limit the length of the detection phase, which can be advantageous for battery life. In particular, the listener beacon signal request signal is a request signal from the target tag to the listener nodes to provide the listener beacon signal. Thus, the listener beacon signal request signal is configured to control the plurality of listener nodes to emit the listener beacon signal upon receiving the listener beacon signal request signal.

[0065] In further embodiments, the target tag can have access to a reporting frequency of the (plurality of listener nodes). The reporting frequency can in particular comprise a default reporting frequency and / or in particular comprise a specific reporting frequency, in particular the default reporting frequency, or in particular the specific reporting frequency.

[0066] In further aspects, the present application can provide an asset tracking system which is functionally couplable with or functionally comprises (in particular comprises) a target tag according to the present application. The asset tracking system can (be configured to) track the target tag in a space. The asset tracking system can further comprise a plurality of listener nodes and a control system. The plurality of listener nodes can in particular be arranged in the space, and the plurality of listener nodes can in particular be configured to (periodically) emit listener beacon signals. The control system can have access to listener position data and / or map data. The asset tracking system can operate in a system operation mode. In the system operation mode: each of the plurality of listener nodes can (be configured to) detect a target beacon signal and provide a related target signal to the control system; and the control system can (be configured to) determine a target tag position of the target tag based on the related target signal, and in particular further based on the listener position data and / or the map data.

[0067] In particular embodiments, the present application can provide an asset tracking system comprising a target tag, wherein the asset tracking system comprises a plurality of listener nodes and a control system, wherein the plurality of listener nodes is configured to emit listener beacon signals, and wherein in a system operation mode: (i) each of the plurality of listener nodes is configured to detect a target beacon signal and to provide a related target signal to the control system; and (ii) the control system is configured to determine a target tag position of the target tag based on the related target signals.

[0068] Thus, the present application can provide an asset tracking system for tracking a target tag in a space. The term "asset tracking system" can refer to any system configured to track the position and / or movement of one or more objects, in particular a target tag, within a space, in particular a (defined) space (see above).

[0069] The asset tracking system can comprise a plurality of listener nodes. In the art, a listener node can also be commonly referred to as "tag listener", "tag localizer", "anchor node", "tag scanner", "reference node", and "sniffer". In embodiments, a listener node can be configured to detect (or: "receive") a target beacon signal, i.e. a listener node can be able to detect a target beacon signal. A listener node can in particular detect a beacon signal passively. In further embodiments, a listener node can comprise an antenna configured for detecting (or: "receiving") a target beacon signal.

[0070] The listener nodes can in particular be arranged in a space, i.e. in a space in which the target tag is to be tracked. It will be clear to the skilled person that a listener node can be arranged at a location which is typically not reached by a target tag, e.g. a target tag can be used for tracking people in an office building, and a listener node can be arranged in a lighting system of the office building.

[0071] In embodiments, at least part of the plurality of listener nodes, in particular each of the plurality of listener nodes, can be configured to adjust a detection threshold (for a target beacon signal) to a detection threshold (for a target tag) when the target tag informs the listener node(s) to set the detection threshold to the detection threshold value.

[0072] In embodiments, the asset tracking system can further comprise a control system. The control system can in particular be configured to control the asset tracking system, in particular the plurality of listener nodes. The control system can in particular be configured to (have to be the asset tracking system) perform the system operation mode.

[0073] In embodiments, the control system can have access to location data of the plurality of listener nodes. The location data can in particular comprise data on a location of (each of) the plurality of listener nodes in the space, e.g. data on a room of (each of) the listener nodes, or e.g. coordinates of (each of) the listener nodes.

[0074] Phrases like “in the operation mode, the control system can determine a target tag location” or “in the operation mode, the control system performs (steps of) a method” or “in the operation mode, the control system can perform a method” and similar phrases can also be understood in embodiments as the control system being configured to perform the indicated action (in the operation mode), e.g. being configured to determine a target tag location in the operation mode, or being configured to perform a method (in the operation mode).

[0075] In embodiments, the receiver beacon signal can comprise one or more of transmission power related data and receiver sensitivity related data of the plurality of listener nodes, in particular one or more of specific transmission power related data and specific receiver sensitivity related data, in particular specific transmission power related data, or in particular specific receiver sensitivity related data. In particular, each listener node can be configured to emit a listener beacon signal comprising one or more of (respective) specific transmission power related data and (respective) specific receiver sensitivity related data, in particular (respective) specific transmission power related data, or in particular (respective) specific receiver sensitivity related data. Thereby, the target tag has access to (specific) transmission power related data and / or receiver sensitivity related data of the plurality of listener nodes, which can facilitate and / or improve the tag operation mode, with all associated benefits.

[0076] In embodiments, the control system can be configured to send a tag calibration (request) signal. Also as indicated above, in embodiments, the target tag can be configured to perform the tag operation mode upon receiving the tag calibration (request) signal. The control system can in particular be configured to send the tag calibration signal in one or more of the following cases: the accuracy of the target tag positioning is below a (predefined) accuracy threshold, and the signal quality of the (detected) target beacon signal is below a (predefined) signal quality threshold. In further embodiments, the control system can adjust the accuracy threshold and the signal quality threshold based on input data, e.g. input data related to a (temporary) importance of the target tag, or e.g. input data from a user interface.

[0077] In embodiments, the control system can be configured to determine a (suitable) calibration spot for the target tag, especially wherein the control system informs the target tag about the calibration spot. For example, in embodiments, the control system can (be configured to) determine a calibration spot that represents an average area in the space, especially with respect to the listener node density, e.g. especially representing an average area in a portion of the space that the target tag has historically moved through. Thus, the control system can have access to one or more of listener location data, map data, and historical data. In further embodiments, the control system can be configured to determine a (suitable) calibration spot for the target tag based on one or more of listener location data, map data, and historical data. The historical data can especially include data about previous tag locations.

[0078] The asset tracking system can especially (at least partially) be integrated into other (pre-existing) infrastructure. Especially, in embodiments, at least a portion of the total number of listener nodes can be integrated in lighting devices, e.g. at least 50% of the total number of listener nodes can be integrated in lighting devices. The lighting devices can be equipped with a low-bandwidth wireless communication device for controlling the lighting devices. For example, the light generating devices can comprise or be functionally coupled to a wireless communication device, such that the light generating devices can be remotely controlled. Thus, in embodiments, the wireless communication device can comprise a listener node.

[0079] The term “lighting device” can herein for example refer to one or more of a light generating device, a light control element (e.g. a light switch), and a sensor (e.g. an occupancy sensor or a proximity sensor).

[0080] In further embodiments, the asset tracking system can comprise a plurality of lighting devices, wherein at least a portion of the plurality of listener nodes are integrated in the lighting devices.

[0081] In embodiments, at least 30% of the total number of listener nodes can be arranged in a regular grid, e.g. of lighting devices. In further embodiments, at least 50% of the total number of listener nodes can be arranged in a regular grid, such as at least 60%, especially at least 70%, such as at least 80%, especially at least 90%, including 100%. The term “regular grid” can herein especially refer to a pattern formed by the intersection of two or more sets of regularly spaced parallel lines, especially wherein the listener nodes are arranged at the intersection points. In further embodiments, the listener nodes comprised by the regular grid can be arranged at (substantially) the same height, e.g. on a ceiling. In further embodiments, the plurality of listener nodes can further comprise one or more listener nodes that are not comprised by the regular grid and are configured at a different height than the listener nodes configured in the regular grid.

[0082] The term "target tag" can also refer to a plurality of target tags herein. In particular, in embodiments, the asset tracking system can be configured to track a plurality of target tags simultaneously. In further embodiments, at least two of the plurality of target tags can have different predetermined target numbers of arrived listener nodes.

[0083] In a further aspect, the application can provide a method for calibrating a target tag, in particular wherein the target tag is configured to detect listener beacon signals transmitted by a plurality of listener nodes. The method can comprise one or more of a detection phase, a signal processing phase, and an execution phase. The detection phase can comprise detecting, with the target tag, listener beacon signals and determining associated listener beacon signal strengths. The signal processing phase can comprise determining a tag transmission power based on the associated listener beacon signal strengths, transmission power related data, receiver sensitivity related data, and the predetermined target number of arrived listener nodes. The execution phase can comprise transmitting a target beacon signal with the target tag at the tag transmission power.

[0084] In embodiments, the method can comprise determining, based on the predetermined target number of arrived listener nodes, the associated listener beacon signal strengths, the transmission power related data, and the receiver sensitivity related data, a target beacon signal strength offset; determining, based on the target beacon signal strength offset, one or more of (a) a (first) transmission power of the target beacon signal and (b) a detection threshold; performing (a) to transmit the target beacon signal at the (first) transmission power, and (b) to inform at least a portion of the plurality of listener nodes to set a detection threshold (of the target tag) to one or more of the detection thresholds.

[0085] In embodiments, the method can comprise detecting, with the target tag, listener beacon signals and determining associated listener beacon signal strengths; determining, based on the associated listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and the predetermined target number of arrived listener nodes, a tag transmission power and / or a receive signal strength threshold; and transmitting a target beacon signal with the target tag at the tag transmission power and / or indicating in the target beacon signal a receive signal strength threshold to be applied by a listener when receiving the (target beacon signal). In particular, the method can comprise determining, based on the associated listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and the predetermined target number of arrived listener nodes, a receive signal strength threshold; and indicating in the target beacon signal a receive signal strength threshold to be applied by a listener when receiving the (target beacon signal).

[0086] In a further aspect, the present application can provide a computer program product comprising instructions for execution on a computer functionally coupled to the target tag, wherein the instructions, when executed by the computer, cause the target tag to perform the method or the tag operating mode of the present application, in particular the method of the present application, or in particular the tag operating mode.

[0087] In embodiments, the computer program product can be executed by a computer functionally coupled to the target tag to cause the target tag to perform the method of the present application. In a further aspect, the present application can provide a data carrier carrying program instructions thereon, which program instructions, when executed by a computer functionally coupled to the target tag, cause the target tag to perform the method or the tag operating mode of the present application, in particular the method of the present application, or in particular the tag operating mode.

[0088] The terms "phase" and similar terms used herein can refer to a (temporal) period (also referred to as "phase") of the method and / or operating mode. Different phases can (partially) overlap in time. For example, the detection phase can typically be initiated before the signal processing phase, but can partially overlap in time therewith. However, for example, the signal processing phase can typically be completed before the execution phase. It will be clear to the skilled person how these phases can be advantageously arranged in time.

[0089] In a further aspect, the present application can provide a target tag for object tracking, wherein the target tag is configured to detect listener beacon signals transmitted by a plurality of listener nodes, wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in the tag operating mode the target tag is configured to: detect listener beacon signals and determine related listener beacon signal strengths; determine a tag transmission power based on at least one of the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and transmit a target beacon signal at the tag transmission power.

[0090] In a further aspect, the present application can provide: a target tag for object tracking, wherein the target tag is configured to detect listener beacon signals transmitted by a plurality of listener nodes, wherein the target tag has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes, and wherein in a tag operating mode, the target tag is configured to: detect listener beacon signals and determine associated listener beacon signal strengths; determine a detection threshold range based on at least one of the associated listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and transmit a target beacon signal comprising the detection threshold range to each listener node of the plurality of listener nodes; wherein the target beacon signal is arranged to enable each listener node to set a receiver detection sensitivity to the detection threshold range.

[0091] The advantages and / or embodiments of the first object of the present application can be applied mutatis mutandis to the other aspects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0092] Embodiments of the present application will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference signs indicate corresponding parts, and in which:

[0093] Figure 1 Embodiments of a target tag and asset tracking system are schematically depicted;

[0094] Figure 2 Embodiments of a tag operating mode and system operating mode are schematically depicted;

[0095] Figure 3 Further embodiments of an asset tracking system are schematically depicted.

[0096] The accompanying schematic drawings are not necessarily to scale. DETAILED DESCRIPTION

[0097] Figure 1An embodiment of a target tag 10 for object tracking is schematically depicted. In the depicted embodiment, the target tag 10 is configured to detect listener beacon signals emitted by a plurality of listener nodes 110 (of the asset tracking system 100), and in particular, the target tag 10 has access to transmission power-related data and receiver sensitivity-related data of the plurality of listener nodes 110. In tag operation mode, the target tag can be configured to: (i) detect (in the detection phase) the listener beacon signal and determine the associated listener beacon signal strength; (ii) determine (in the signal processing phase) the tag transmission power T based on the associated listener beacon signal strength, transmission power-related data, receiver sensitivity-related data, and a predetermined number of targets arriving at the listener nodes. t ; and with tag transmission power T t Transmit the target beacon signal (during the execution phase).

[0098] For visualization purposes, the tag transmission power T t The circle depicted around target tag 10 indicates the area where listener node 110 will need to be present to detect (and / or process) the target beacon signal. Those skilled in the art will appreciate that this is a simplified representation and may not take into account, for example, the different receiver sensitivities of different listener nodes 110.

[0099] In the depicted embodiment, the target tag 10 may have a default transmission power T d The default settings for transmitting target beacon signals utilize the default transmission power T. d Six different listener nodes 110 (110a, 110b, 110c, 110d, 110e, 110f) are reachable. However, three listener nodes may be sufficient for accurate positioning. Therefore, the default transmission may be excessive for the space 500 where the target tag 10 is currently located.

[0100] The target tag 10 may have access to transmission power-related data and receiver sensitivity-related data of multiple listener nodes 110. In the depicted embodiment, the target tag may in particular have access to transmission power-related data and receiver sensitivity-related data of each of the multiple listener nodes 110a, 110b, 110c, 110d, 110e, and 110f. Furthermore, during the detection phase, the target tag may acquire the listener beacon signal strength associated with the listener beacon signals of the multiple listener nodes 110 (especially each of the multiple listener nodes 110a, 110b, 110c, 110d, 110e, and 110f).

[0101] Specifically, for each of the multiple listener nodes 110, the target tag 10 can determine the (corresponding) receiver sensitivity R based on receiver sensitivity-related data. i The listener's transmission power L is determined based on transmission power related data. i And determine the (corresponding) signal strength S based on the relevant listener beacon signal strength. i Based on this information, target tag 10 can determine the (corresponding) transmission power T required for each listener node 110 to detect the target beacon signal. i Specifically, in the embodiments, T i T can be determined according to the following formula: i =R i +L i -S i Therefore, regarding Figure 1 In an embodiment, target tag 10 may have access to the information summarized in Table 1:

[0102] Listener node [R i [dBm]]]> L i [dBm]]]> S i [dBm]]]> T i [dBm]]]> 110a -96 0 -90 -6 110b -96 0 -66 -30 110c -96 0 -82 -14 110d -96 0 -93 -3 110e -96 0 -75 -21 110f -96 0 -88 -8

[0103] Therefore, based on the data available for the tag, the target beacon signal transmitted from target 10 at a transmission power of -15dBm will be sufficient to be detected by listener nodes 110b and 110e, and the target beacon signal transmitted from target 10 at a transmission power of -10dBm will also be sufficient to be detected by listener node 110c.

[0104] In another embodiment, the predetermined target number of arriving listener nodes 110 may include an upper target number n. U The target tag 10 is configured to determine the tag transmission power T. t This makes the upper limit target number n less than or equal to the number of listener nodes 110. U Application T t ≥T i That is, for an upper limit target number n that is less than or equal to multiple listener nodes 110 U Application T t ≥R i +L i -S i In the embodiment, the upper limit target quantity n U It can be a maximum of 20, for example, a maximum of 15, especially a maximum of 10, for example, a maximum of 8, especially a maximum of 5. For example, regarding the information in Table 1, if n U If it is 5, then T t It must be less than the largest T i (Because there are six listener nodes), the largest T iis -3 dBm, thus, with respect to the above example, for n U = 5, T t <- 3 dBm.

[0105] Thus, in embodiments, the target tag can be configured to determine the tag transmission power T t according to a (pseudo) optimization problem comprising:

[0106] selecting T t

[0107] a constraint 2 (T t ≥ R i + L i - S i ) ≤ n U for i = 1,..., m

[0108] T min ≤ T t ≤ T max

[0109] where m is the total number of (relevant) listener nodes, where T min is the minimum transmission power the target tag can emit (which can be hardware- or software-determined), and where T max is the maximum transmission power the target tag 10 can emit.

[0110] In further embodiments, the predetermined target number of reached listener nodes 110 can comprise a lower target number n L , where the target tag 10 is configured to determine the transmission power T t such that for the lower target number n L of listener nodes 110 greater than or equal to the plurality of listener nodes 110, T t ≥ T i , i.e., such that for the lower target number n L of listener nodes 110 greater than or equal to the plurality of listener nodes 110, T t ≥ R i + L i - S i . In embodiments, the lower target number n L may be at least 3, e.g., at least 4, in particular at least 5, e.g., at least 7. For example, with respect to the information in Table 1, if n L is 3, then T t must be greater than the third smallest T i (which is -14 dBm), thus, with respect to the above example, for n U = 5, T t ≥ -14 dBm.

[0111] Thus, in further embodiments, the target tag can be configured to determine the tag transmission power T according to a (pseudo) optimization problem t comprising:

[0112] selecting T t

[0113] subject to the constraint ∑(T t ≥ R i + L i + S i ) ≥ n L for i = 1,..., m

[0114] T min ≤ T t ≤ T max

[0115] In further embodiments, the predetermined target number can comprise a lower target number n L and an upper target number n U , in particular wherein n U ≥ n L . For example, with respect to the information in Table 1, if n L = 3 and n U = 5, then T t must be greater than the third smallest T i (which is -14 dBm) and less than the largest T i (which is -3 dBm), thus, with respect to the above example, -14 dBm ≤ T t <- 3 dBm.

[0116] Thus, in further embodiments, the target tag can be configured to determine the tag transmission power T according to a (pseudo) optimization problem t comprising:

[0117] selecting T t

[0118] subject to the constraint ∑(T t ≥ R i + L i + S i ) ≤ n U for i = 1,..., m

[0119] ∑(T t ≥ R i + L i + S i ) ≥ n L for i = 1,..., m

[0120] T min ≤T t ≤T max

[0121] In embodiments, the target tag 10 can be configured to minimize the transmission power T t . Hence, in embodiments, the (pseudo) optimization problem can comprise a minimization criterion. For example, with respect to the example of Table 1, and where n L is 3 and n U is 5, T t may be chosen to be -14 dBm in view of the minimization criterion.

[0122] Hence, in embodiments, the (pseudo) optimization problem may, for example, comprise:

[0123] minimize T t

[0124] subject to the constraint ∑(T t ≥ R i + L i + S i ) ≥ n L for i = 1,..., m

[0125] T min ≤ T t ≤ T max

[0126] Similarly, the target tag 10 can be configured to maximize the transmission power T t . Hence, in embodiments, the (pseudo) optimization problem can comprise:

[0127] maximize T t

[0128] subject to the constraint ∑(T t ≥ R i + L i - S i ) ≤ n U for i = 1,..., m

[0129] T min ≤ T t ≤ T max

[0130] In practice, it can be desirable to choose T t to be a value slightly larger than the minimum value determined for reaching a predetermined (lower) target number. For example, the tag transmission power T t may be chosen such that the tag transmission power T tan increased strength T with respect to a minimum required tag transmission power taking into account a predetermined target number of listener nodes 110 to reach a where the increased strength T a is at least 0.1 dBm, such as at least 0.2 dBm, in particular at least 0.5 dBm, such as at least 1 dBm, such as at least 2 dBm. In further embodiments, the increased strength T a may be at most 3 dBm, for example at most 2 dBm, in particular at most 1 dBm.

[0131] As mentioned above, as an alternative to adjusting the tag transmission power, the target tag can also inform the plurality of listener nodes to adjust their expected threshold for receiving and processing the target beacon signal. In the example above, the target tag 10 can inform the listener nodes 110 to set the detection threshold in the range of -82 dBm and -88 dBm. In this way, the listener nodes 110b, 110c and 110e will be able to report the target beacon signal, as their received signal strength will be above the detection threshold level, while the other listener nodes 110 will not.

[0132] In particular, with respect to the above formula, the target tag can adjust the S i of the plurality of listener nodes (at least part of). Thus, the pseudo-optimization problem can comprise:

[0133] selecting S i

[0134] subject to the constraint ∑(T t ≥ R i + L i - S i )≤ n U for i = 1,..., m

[0135] S min < S ≤ S max

[0136] T min ≤ T t ≤ T max

[0137] It will be clear to the person skilled in the art that the pseudo-optimization problem can also be combined. For example, in further embodiments, the pseudo-optimization problem can comprise:

[0138] selecting T t , S i

[0139] subject to the constraint ∑(T t ≥ R i + L i - S i )≤ nU for i = 1,..., m

[0140] S min <S i ≤ S max

[0141] T min ≤ T t ≤ T max

[0142] Thus, in embodiments, the target tag 10 is configured to emit a target beacon signal, and wherein the target tag 10 is configured to detect listener beacon signals emitted by the plurality of listener nodes 110, and wherein each of the plurality of listener nodes 110 is configured to detect the target beacon signal and to report a related target signal if a target signal strength of the target beacon signal exceeds a detection threshold, and wherein the target tag 10 has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes 110, and wherein in an operational mode, the target tag 10 is configured to: detect the listener beacon signals and determine related listener beacon signal strengths; determine a target beacon signal strength offset based on a predetermined target number of arrived listener nodes 110, the related listener beacon signal strengths, the transmission power related data and the receiver sensitivity related data; determine one or more of (a) a transmission power of the target beacon signal and (b) the detection threshold based on the target beacon signal strength offset, and perform (a) to emit the target beacon signal with the transmission power and (b) to inform at least a portion of the plurality of listener nodes 110 to set the detection threshold to one or more of the detection threshold.

[0143] In further embodiments, the target beacon signal can comprise instructions for the plurality of listener nodes 110 (at least a portion thereof) to adjust the detection threshold.

[0144] In embodiments, the target tag 10 can be configured to detect listener beacon signals emitted by a plurality of listener nodes, wherein the target tag 10 has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes 110, and wherein in the tag operation mode the target tag 10 is configured to: detect listener beacon signals and determine related listener beacon signal strengths; determine a (receiver) detection threshold range (for each of the plurality of listener nodes 110) based on the related listener beacon signal strengths, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes 110; and emit a target beacon signal including the detection threshold range, in particular to at least a portion of the plurality of listener nodes 110, more particularly to each of the plurality of listener nodes 110. In further embodiments, the target beacon signal, in particular the target beacon signal including the detection threshold range, can be arranged to enable (each of the) listener nodes 110 (of the plurality of listener nodes 110) to set the (respective) receiver sensitivity to the detection threshold range.

[0145] In further embodiments, the predetermined target number can comprise a desired target number, and the target tag can be configured to minimize a deviation of the desired target number of arrived nodes and an actual number of arrived nodes.

[0146] Figure 1 Further embodiments of an asset tracking system 100 including a target tag 10 are schematically depicted. In the depicted embodiments, the asset tracking system is configured for tracking a target tag 10 in a space 500. The asset tracking system 100 comprises a plurality of listener nodes 110 and a control system 300, wherein the plurality of listener nodes 110 are arranged in the space 500, and wherein the plurality of listener nodes 110 are configured to emit listener beacon signals. The system 100 can have a system operation mode, wherein in the system operation mode: (i) each of the plurality of listener nodes 110 is configured to detect a target beacon signal (of a target tag) and to provide a related target signal to the control system 300; and (ii) the control system 300 is configured to determine a target tag location of the target tag 10 based on the related target signals.

[0147] Figure 2 The tag operation mode 20 and the system operation mode 200 are schematically depicted.

[0148] The tag operation mode 20 can comprise a detection phase 22, a signal processing phase 23 and an execution phase 24. In the detection phase 22, the target tag 10 can (be configured to) detect listener beacon signals and determine a related listener beacon signal strength. In the signal processing phase 23, the target tag 10 can (be configured to) determine a tag transmission power T t In the execution phase 24, the target tag 10 can (be configured to) transmit a target beacon signal with the tag transmission power T t The target beacon signal can comprise a target beacon signal strength. In further embodiments, the target beacon signal can comprise an instruction for the plurality of listener nodes 110 to adjust a detection threshold.

[0149] In particular, as Figure 2 depicted, the execution phase 24 can be repeated multiple times. The execution phase 24 can be repeated until the tag operation mode 20 is (re-)executed and, for example, restarted in the detection phase.

[0150] In embodiments, the target tag 10 can be configured to (re-)execute the tag operation mode according to a scan frequency, in particular wherein the scan frequency is based on one or more of a movement, a battery life and a predefined period. In further embodiments, the target tag 10 can be configured to (re-)execute the tag operation mode upon reception of an (external) tag calibration signal.

[0151] In embodiments, the target tag 10 can be configured to remain in the execution phase even if the target tag 10 is switched off and switched on again, i.e. the target tag can be configured to execute the tag operation mode only according to one or more of a scan frequency and a tag calibration signal.

[0152] In further embodiments, the operation mode 20 can further comprise a start-up phase 21. In the start-up phase 21, the target tag can (be configured to) transmit a listener beacon signal request signal. In particular, in (systems of) embodiments, the plurality of listener nodes 110 are configured to transmit a listener beacon signal upon reception of the listener beacon signal request signal. Thus, the listener beacon signal request signal is configured to control the plurality of listener nodes to transmit a listener beacon signal upon reception of the listener beacon signal request signal.

[0153] The system operation mode 200 can comprise a beacon detection phase 201 and a localization phase 202. In the beacon detection phase 201, each of the plurality of listener nodes 110 can be configured to detect a target beacon signal and to provide a related target signal to the control system 300. It will be clear to the skilled person that, although all listener nodes 110 can be configured to detect a target beacon signal, typically only a first subset of the listener nodes 110 can detect a target beacon signal, and typically only a second subset (of the first subset) can report a related target signal to the control system 300.

[0154] In the localization phase 202, the control system 300 can be (configured to) determine a target tag position of the target tag 10 based on the related target signals. In embodiments, the control system 300 can be (configured to) determine a target tag position of the target tag 10 based on the related target signals, and one or more of listener position data and / or map data.

[0155] Figure 2 Further illustratively depicted is a method for calibrating a target tag 10, wherein the target tag 10 is configured to detect listener beacon signals emitted by a plurality of listener nodes 110. The method comprises a detection phase 22 comprising detecting, with the target tag 10, a listener beacon signal and determining a related listener beacon signal strength; a signal processing phase 23 comprising determining a tag transmission power based on the related listener beacon signal strength, transmission power related data, receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and an execution phase 24 comprising emitting, with the target tag 10, a target beacon signal at the tag transmission power.

[0156] Figure 3 Another embodiment of the asset tracking system 100 is illustratively depicted, wherein at least a part of the total number of the plurality of listener nodes 110 is integrated in a lighting device 1000. In particular, Figure 3 Illustratively depicted is a lighting device 1000 comprising a light generating device such as a lamp 1001 and a luminaire 1002, and a lighting control element 1003 such as a user interface (e.g. a graphical user interface). Reference sign 1010 denotes light generated by the lighting device 1000. In particular, such light is visible light, e.g. white light. The lighting control element 1003 can also be a portable device, e.g. an I-phone or a smart phone.

[0157] Figure 3 Also illustratively depicted is an embodiment of the lighting device 1000, wherein the lighting device 1000 comprises at least one listener node 110 of the present invention for use in the asset tracking system 100 of the present invention.

[0158] The term "plurality" means two or more. Furthermore, the terms "plurality" and "a number of can be used interchangeably.

[0159] The terms "substantially" and "essentially" and similar terms in the present text will be understood by the skilled person. The terms "substantially" or "essentially" can also include embodiments with "completely", "entirely", "all" and the like. Thus, in embodiments, the adjective substantially or essentially can also be removed. Where applicable, the term "substantially" or the term "essentially" can also relate to 90% or more, such as 95% or more, in particular 99% or more, even more particularly 99.5% or more, including 100%. Furthermore, the terms "about" and "approximately" can also relate to 90% or more, for example 95% or more, in particular 99% or more, even more particularly 99.5% or more, including 100%. For numerical values, it is to be understood that the terms "substantially", "essentially", "about" and "approximately" can also relate to a range of 90-110%, for example 95-105%, in particular 99-101% of the numerical value(s) to which they refer.

[0160] The term "comprising" also includes embodiments where the term "comprising" is interpreted as "consisting of".

[0161] The term "and / or" relates in particular to one or more of the items of the list that it connects. For example, the phrase "item 1 and / or item 2" and similar phrases can relate to one or more of item 1 and item 2. The term "comprising" can in one embodiment refer to "consisting of", but can in another embodiment also refer to "including at least the defined species and optionally one or more additional species".

[0162] Furthermore, the terms first, second, third and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the application described herein are capable of operation in other sequences than described or illustrated herein.

[0163] During operation, an apparatus, device, or system can be described herein, among others. As will be apparent to those of ordinary skill in the art, the application is not limited to the method of operation, or to apparatus, devices, or systems in operation.

[0164] The term "further embodiments" and similar terms can refer to embodiments that include features of previously discussed embodiments, but can also refer to alternative embodiments.

[0165] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0166] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0167] The use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in the claims. Throughout the description and claims, the word "comprise" (also "comprising"), "include" (also "including"), "contain" (also "containing") and variations thereof shall not be interpreted as limiting the scope of the claims but as meaning "including, but not limited to".

[0168] The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0169] The application can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim enumerating several means, those means can be embodied by one and the same item of hardware. 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.

[0170] The application also provides a control system, which can control an apparatus, device or system, or which can carry out a method or process as described herein. Yet further, the application also provides a computer program product, which, when run on a computer functionally coupled to or comprised by an apparatus, device or system, controls one or more controllable elements of such apparatus, device or system.

[0171] The terms "control" and similar terms herein refer at least to determining the behavior of an element or supervising the operation of an element. Thus, "control" and similar terms herein can refer, for example, to exerting a behavior on an element (determining the behavior or supervising the operation of an element), such as, for example, measuring, displaying, actuating, opening, moving, changing a temperature, etc. In addition to this, the terms "control" and similar terms can additionally include monitoring. Thus, the terms "control" and similar terms can include exerting a behavior on an element, as well as exerting a behavior on an element and monitoring the element. The control of the element can be done with a control system. Thus, the control system and the element can be functionally coupled at least temporarily or permanently. The element can comprise the control system. In embodiments, the control system and the element can not be physically coupled. The control can be done via wired and / or wireless control. The term "control system" can also refer to a plurality of different control systems, which are functionally coupled, and wherein, for example, one control system can be a master control system and one or more other control systems can be slave control systems.

[0172] The application also applies to a device, apparatus, or system comprising one or more features described in the description and / or shown in the attached drawings. The application also relates to a method or procedure comprising one or more features described in the description and / or shown in the attached drawings. Furthermore, if a method or an embodiment of the method is described as being performed in a device, apparatus, or system, it will be understood that the device, apparatus, or system is respectively adapted or configured to (perform) the method or the embodiment of the method.

[0173] The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, a person skilled in the art will understand that embodiments can be combined and that more than two embodiments can also be combined. Furthermore, some features can form the basis of one or more divisional applications.

[0174] The application relates, inter alia, to a target tag configured to adjust its transmission power of a target beacon signal in view of a desired number of listener nodes that detect the target beacon signal and report a related signal to a control system. To this end, the target tag can determine a signal loss that occurs when a listener beacon signal emitted from a listener node propagates to the target tag, and can adjust its transmission power accordingly, also taking into account the transmission power and sensitivity of the listener nodes.

Claims

1. A target tag (10) for object tracking, wherein the target tag (10) is configured to detect listener beacon signals transmitted by a plurality of listener nodes (110), wherein the listener beacon signals comprise one or more of transmission power related data and receiver sensitivity related data of the plurality of listener nodes; wherein the target tag (10) has access to the transmission power related data and the receiver sensitivity related data of the plurality of listener nodes (110), and wherein in a tag operation mode, the target tag (10) is configured to: - detect the listener beacon signals and determine a related listener beacon signal strength and one or more of the transmission power related data and the receiver sensitivity related data; - determine a tag transmission power based on the related listener beacon signal strength, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and - transmit a target beacon signal at the tag transmission power.

2. The target tag (10) according to claim 1, wherein the predetermined target number of reached listener nodes (110) comprises an upper target number, wherein for each listener node of the plurality of listener nodes (110) the target tag (10) determines a receiver sensitivity R i based on the receiver sensitivity related data, determines a listener transmission power L i based on the transmission power related data, and determines a signal strength S i based on the related listener beacon signal strength, and wherein the target tag (10) is configured to determine the tag transmission power T t such that for less than or equal to the upper target number of the plurality of listener nodes (110) applies T t ≥ R i + L i - S i .

3. The target tag (10) according to claim 2, wherein the predetermined target number of reached listener nodes (110) comprises a lower target number, wherein the target tag (10) is configured to determine a transmission power T t such that for a number of reached listener nodes (110) being greater than or equal to the lower target number of listener nodes (110) of the plurality of listener nodes (110), T t ≥ R i + L i - S i is applied.

4. The target tag (10) according to claim 2 or 3, wherein the target tag (10) is configured to minimize transmission power T t .

5. The target tag (10) according to any one of the preceding claims 1-3, wherein In the tag operation mode, the target tag (10) is configured to determine the predetermined target number of arrived listener nodes (110) based on a predetermined signal quality requirement.

6. The target tag (10) of claim 3, wherein the lower target number is at least 3.

7. The target tag (10) according to any of the preceding claims 1, 2, 3 and 6, wherein The target tag (10) is configured to: - perform the tag operation mode according to a scan frequency, wherein the scan frequency is based on one or more of movement, battery life, and a predefined period; or - perform the tag operation mode upon reception of a tag calibration signal.

8. The target tag (10) according to any of the preceding claims 1, 2, 3 and 6, wherein In the tag operation mode, the target tag (10) is configured to: - transmit a listener beacon signal request signal; wherein the listener beacon signal request signal is configured to control the plurality of listener nodes (110) to transmit the listener beacon signals upon reception of the listener beacon signal request signal.

9. A target tag (10) for object tracking, wherein the target tag (10) is configured to detect listener beacon signals transmitted by a plurality of listener nodes (110), wherein the target tag (10) has access to transmission power related data and receiver sensitivity related data of the plurality of listener nodes (110), and wherein in a tag operation mode, the target tag (10) is configured to: - detect the listener beacon signals and determine a related listener beacon signal strength; - determining a detection threshold range based on said correlated listener beacon signal strength, said transmission power related data, said receiver sensitivity related data, and a predetermined target number of arrived listener nodes (110); and - transmit a target beacon signal comprising the detection threshold range to each listener node (110) of the plurality of listener nodes (110); wherein the target beacon signal is arranged to enable each listener node (110) to set a receiver sensitivity to the detection threshold range.

10. An asset tracking system (100) comprising a target tag (10) according to any of the preceding claims, wherein the asset tracking system (100) comprises the plurality of listener nodes (110) and a control system (300), and wherein the plurality of listener nodes (110) are configured to emit listener beacon signals, and wherein in a system operation mode: - each of the plurality of listener nodes (110) is configured to detect a target beacon signal and to provide a related target signal to the control system (300); and - the control system (300) is configured to determine a target tag location of the target tag (10) based on the related target signals.

11. The asset tracking system (100) according to claim 10, wherein the control system (300) is configured to send a tag calibration signal, wherein the target tag (10) is configured to perform a tag operation mode upon reception of the tag calibration signal.

12. The asset tracking system (100) according to any of the preceding claims 10-11, wherein, at least a portion of the total number of the plurality of listener nodes (110) are integrated in a lighting device (1000).

13. A method for calibrating a target tag (10), wherein the target tag (10) is configured to detect listener beacon signals emitted by a plurality of listener nodes (110), wherein the listener beacon signals comprise one or more of transmission power related data and receiver sensitivity related data of the plurality of listener nodes; wherein the method comprises: - detecting the listener beacon signals with the target tag (10) and determining a related listener beacon signal strength and one or more of the transmission power related data and the receiver sensitivity related data; - determining a tag transmission power based on the related listener beacon signal strength, the transmission power related data, the receiver sensitivity related data, and a predetermined target number of arrived listener nodes; and - emitting a target beacon signal with the target tag (10) at the tag transmission power.

14. A computer program product comprising instructions for execution on a computer functionally coupled to a target tag (10), wherein the instructions, when executed by the computer, cause the target tag (10) to perform the method according to the preceding claim 13.

Images