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 emitted 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 operational mode the target tag (10) is configured to: detect the listener beacon signals and to 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 goal number of reached listener nodes; and emit the target beacon signal at the tag transmission power.

Claims

1. 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 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 has access to said transmission power-related data and said receiver sensitivity-related data of the plurality of listener nodes, and wherein in a tag operational mode the target tag is configured to: detect the listener beacon signals and to determine related listener beacon signal strengths 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 strengths, the transmission power-related data, the receiver sensitivity-related data, and a predetermined goal number of reached listener nodes; and emit the target beacon signal at the tag transmission power.

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

3. The target tag according to claim 2, wherein the predetermined goal number of reached listener nodes comprises a lower goal number, wherein the target tag is configured to determine the transmission power T.sub.t such that for more than or equal to the lower goal number of listener nodes of the plurality of listener nodes applies that T.sub.t≥R.sub.i+L.sub.i−S.sub.i.

4. The target tag according to claim 2, wherein the target tag is configured to minimize the transmission power T.sub.t.

5. The target tag according to claim 1, wherein in the tag operational mode the target tag is configured to determine the predetermined goal number of reached listener nodes based on a predetermined signal quality requirement.

6. The target tag according to claim 3, wherein the lower goal number is at least 3.

7. The target tag according to claim 1, wherein the target tag is configured to: execute the tag operational mode according to a scanning frequency, wherein the scanning frequency is based on one or more of movement, battery life, and a predefined period; or execute the tag operational mode upon receiving a tag calibration signal.

8. The target tag according to claim 1, wherein in the tag operational mode the target tag is configured to: emit a listener beacon signal request signal; wherein the listener beacon signal request signal is configured to control the plurality of listener nodes to emit the listener beacon signals upon receiving the listener beacon signal request signal.

9. 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 operational mode the target tag is configured to: detect the listener beacon signals and to determine related listener beacon signal strengths; determine a detection threshold range based on the related listener beacon signal strengths, the transmission power-related data, the receiver sensitivity-related data, and a predetermined goal number of reached listener nodes; and emit the target beacon signal comprising the detection threshold range to each listener node of the plurality of listener nodes; wherein said target beacon signal is arranged for enabling each listener node to set a receiver sensitivity to the detection threshold range.

10. An asset-tracking system comprising a target tag according to claim 1, wherein the asset-tracking system comprises said plurality of listener nodes and a control system, and wherein the plurality of listener nodes are configured to emit listener beacon signals, and wherein in a system operational mode: each of the plurality of listener nodes is configured to detect the target beacon signal and to provide a related target signal to the control system; and the control system is configured to determine a target tag location of the target tag based on the related target signals.

11. The asset-tracking system according to claim 10, wherein the control system is configured to send a tag calibration signal, wherein the target tag is configured to execute the tag operational mode upon receiving the tag calibration signal.

12. The asset-tracking system according to claim 10, wherein at least part of a total number of the plurality of listener nodes are integrated in lighting devices.

13. A method for calibrating a target tag, wherein the target tag is configured to detect listener beacon signals emitted by a plurality of listener nodes, 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 and determining related listener beacon signal strengths 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 strengths, the transmission power-related data, the receiver sensitivity-related data, and a predetermined goal number of reached listener nodes; and emitting a target beacon signal with the target tag at the tag transmission power.

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

[0093] FIG. 1 schematically depicts embodiments of the target tag and the asset-tracking system;

[0094] FIG. 2 schematically depicts embodiments of the tag operational mode and the system operational mode;

[0095] FIG. 3 schematically depicts a further embodiment of the asset-tracking system.

[0096] The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0097] FIG. 1 schematically depicts an embodiment of the target tag 10 for object tracking. In the depicted embodiment, the target tag 10 is configured to detect listener beacon signals emitted by a plurality of listener nodes 110 (of an asset-tracking system 100), especially wherein the target tag 10 has access to transmission power-related data and receiver sensitivity-related data of the plurality of listener nodes 110. In a tag operational mode, the target tag may be configured to: (i) detect (in a detection stage) the listener beacon signals and determine related listener beacon signal strengths; (ii) determine (in a signal processing stage) a tag transmission power T.sub.t based on the related listener beacon signal strengths, the transmission power-related data, the receiver sensitivity-related data, and a predetermined goal number of reached listener nodes; and emit (in an execution stage) the target beacon signal at the tag transmission power Tt.

[0098] For visualizational purposes, the tag transmission power T.sub.t is depicted as a circle around the target tag 10, indicative of the area in which a listener node 110 would need to be present to detect (and/or process) the target beacon signal. It will be clear to the person skilled in the art that this is a simplified representation and may not account for, for example, different receiver sensitivities of different listener nodes 110.

[0099] In the depicted embodiment, the target tag 10 may have default settings to emit the target beacon signal at a default transmission power T.sub.d, with which six different listener nodes 110, 110a, 110b, 110c, 110d, 110e, 110f may be reached. However, three listener nodes may be sufficient for accurate localization. Hence, the default transmission may be excessive for the space 500 the target tag 10 is currently in.

[0100] The target tag 10 may have access to transmission power-related data and receiver sensitivity-related data of the plurality of listener nodes 110. In the depicted embodiment, the target tag may especially have access to transmission power-related data and receiver sensitivity-related data of each of the listener nodes 110a, 110b, 110c, 110d, 110e, and 110f. Further, in the detection stage, the target tag may acquire listener beacon signal strengths related to the listener beacon signals of the plurality of listener nodes 110, especially each listener node 110 of the plurality of listener nodes 110a, 110b, 110c, 110d, 110e, and 110f.

[0101] In particular, for each listener node 110 of the plurality of listener nodes 110, the target tag 10 may determine a (respective) receiver sensitivity R.sub.i based on the receiver sensitivity-related data, a (respective) listener transmission power L.sub.i based on the transmission power-related data, and a (respective) signal strength S.sub.i based on the related listener beacon signal strengths. Based on this information, the target tag 10 can for each listener node 110 determine the (respective) transmission power T.sub.i that would be needed for the listener node 110 to detect the target beacon signal. Specifically, in embodiments, T.sub.i may be determined according to: T.sub.i=R.sub.i+L.sub.i−S.sub.i. Hence, with regards to the embodiment of FIG. 1A, the target tag 10 may have access to the information summarized in Table 1:

TABLE-US-00001 Listener node R.sub.i [dBm] L.sub.i [dBm] S.sub.i [dBm] T.sub.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

[0102] Hence, a target beacon signal emitted from the target 10 at a transmission power of −15 dBm would, according to the data available to the tag, be sufficient for detection by listener nodes 110b and 110e, whereas a target beacon signal emitted from the target 10 at a transmission power of −10 dBm would also be sufficient for detection by listener node 110c.

[0103] In further embodiments, the predetermined goal number of reached listener nodes 110 may comprise an upper goal number n.sub.U, wherein the target tag 10 is configured to determine the tag transmission power T.sub.t such that for less than or equal to the upper goal number n.sub.U of the plurality of listener nodes 110 applies that T.sub.t≥T.sub.i, i.e., that for less than or equal to the upper goal number n.sub.u of the plurality of listener nodes 110 applies that T.sub.t≥R.sub.i+L.sub.i−S.sub.i. In embodiments, the upper goal number n.sub.U may be at most 20, such as most 15, especially at most 10, such as at most 8, especially at most 5. For example, with regards to the information in table 1, if n.sub.U is 5, then T.sub.t has to be smaller than the largest T.sub.i (as there are six listener nodes), which is −3 dBm, hence, with regards to above example, for n.sub.U=5, T.sub.t<−3 dBm.

[0104] Hence, in embodiments, the target tag may be configured to determine the tag transmission power T.sub.t according to a (pseudo-)optimization problem comprising:

[00001]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Select}& T_t\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i-S_i\right)\le n_U& \mathrm{for}i=1,.Math.,m\end{array}\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

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

[0105] In further embodiments, the predetermined goal number of reached listener nodes 110 may comprise a lower goal number n.sub.L, wherein the target tag 10 is configured to determine the transmission power T.sub.t such that for more than or equal to the lower goal number n.sub.L of listener nodes 110 of the plurality of listener nodes 110 applies that T.sub.t≥T.sub.i, i.e., such that for more than or equal to the lower goal number n.sub.L of listener nodes 110 of the plurality of listener nodes 110 applies that T.sub.t≥R.sub.i+L.sub.i−S.sub.i. In embodiments, the lower goal number n.sub.L may be at least 3, such as at least 4, especially at least 5, such as at least 7. For example, with regards to the information in table 1, if n.sub.L is 3, then T.sub.t has to be larger than the third smallest T.sub.i, which is −14 dBm, hence, with regards to above example, for n.sub.U=5, T.sub.t≥−14 dBm.

[0106] Hence, in further embodiments, the target tag may be configured to determine the tag transmission power T.sub.t according to a (pseudo-)optimization problem comprising:

[00002]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Select}& T_t\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i+S_i\right)\le n_L& \mathrm{for}i=1,.Math.,m\end{array}\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0107] In further embodiments, the predetermined goal number may comprise both a lower goal number n.sub.L and an upper goal number n.sub.U, especially wherein n.sub.U≥n.sub.L. For example, with regards to the information in table 1, if n.sub.L=3 and n.sub.U=5, then T.sub.t has to be larger than the third smallest T.sub.i, which is −14 dBm, and smaller than the largest T.sub.i, which is −3 dBm, hence, with regards to above example, −14 dBm≤T.sub.t<−3 dBm.

[0108] Hence, in further embodiments, the target tag may be configured to determine the tag transmission power T.sub.t according to a (pseudo-)optimization problem comprising:

[00003]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Select}& T_t\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i+S_i\right)\le n_U& \mathrm{for}i=1,.Math.,m\end{array}\\ & \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i+S_i\right)\ge n_L& \mathrm{for}i=1,.Math.,m\end{array}\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0109] In embodiments, the target tag 10 may be configured to minimize the transmission power T.sub.t. Hence, in embodiments, the (pseudo-)optimization problem may contain a minimization criterion. For example, with regards to the example of Table 1, and wherein if n.sub.L is 3 and n.sub.U is 5, T.sub.t may be selected to be −14 dBm in view of the minimization criterion.

[0110] Hence, in embodiments, the (pseudo-)optimization problem may, for example, comprise:

[00004]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Minimize}& T_t\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i+S_i\right)\ge n_L& \mathrm{for}i=1,.Math.,m\end{array}\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0111] Similarly, the target tag 10 may be configured to maximize the transmission power T.sub.t. Hence, in embodiments, the (pseudo)-optimization problem may comprise:

[00005]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Maximize}& T_t\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i-S_i\right)\le n_U& \mathrm{for}i=1,.Math.,m\end{array}\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0112] In practice, it may be desirable to select a value for T.sub.t that is slightly larger than the minimal value determined to reach the predetermined (lower) goal number. For example, the tag transmission power T.sub.t may be selected such that the tag transmission power T.sub.t has an added strength T.sub.a relative to the tag transmission power minimally needed in view of the predetermined goal number of reached listener nodes 110, wherein the added strength T.sub.a is at least 0.1 dBm, such as at least 0.2 dBm, especially at least 0.5 dBm, such as at least 1 dBm, such as at least 2 dBm. In further embodiments, the added strength T.sub.a may be at most 3 dBm, such as at most 2 dBm, especially at most 1 dBm.

[0113] As indicated above, as an alternative to adjusting the tag transmission power, the target tag may also inform the plurality of listener nodes to adjust their desired threshold value for receiving and processing the target beacon signal. In the example above, the target tag 10 may inform the listener nodes 110 to set the detection threshold value in the range of −82 dBm and −88 dBm. In this way, listener nodes 110b, 110c and 110e will be able to report the target beacon signal because their received signal strengths would lie above the detection threshold level, while the other listener nodes 110 will not.

[0114] In particular, with respect to the formulae above, the target tag may adjust S.sub.i of (at least part of) the plurality of listener nodes. Hence, the pseudo-optimization problem may comprise:

[00006]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Select}& S_i\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i-S_i\right)\le n_U& \mathrm{for}i=1,.Math.,m\end{array}\\ & S_{\min }<S_i\le S_{\max }\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0115] It will be clear for the person skilled in the art that the pseudo-optimization problems may also be combined. For example, in further embodiments, the pseudo-optimization problem may comprise:

[00007]$\begin{array}{cc}& \begin{array}{cc}\mathrm{Select}& T_t,S_i\end{array}\\ \mathrm{Subject}\mathrm{to}& \begin{array}{cc}.Math.\left(T_t\ge R_i+L_i-S_i\right)\le n_U& \mathrm{for}i=1,.Math.,m\end{array}\\ & S_{\min }<S_i\le S_{\max }\\ & T_{\min }\le T_t\le T_{\max }\end{array}$

[0116] Hence, 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 a 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 to determine related listener beacon signal strengths; determine a target beacon signal strength offset based on a predetermined goal number of reached listener nodes 110, the related listener beacon signal strengths, the transmission power-related data and the receiver sensitivity-related data; determine on the basis of the target beacon signal strength offset one or more of (a) a transmission power of the target beacon signal and (b) a detection threshold value and execute one or more of (a) emitting the target beacon signal at the transmission power, and (b) informing at least part of the plurality of listener nodes 110 to set the detection threshold at the detection threshold value.

[0117] In further embodiments, the target beacon signal may comprise instructions for the (at least part of the) plurality of listener nodes 110 to adjust the detection threshold value.

[0118] In embodiments, the target tag 10 may 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 a tag operational mode the target tag 10 is configured to: detect the listener beacon signals and to determine related listener beacon signal strengths; determine a (receiver) detection threshold range (for each listener node 110 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 goal number of reached listener nodes 110; and emit the target beacon signal comprising the detection threshold range, especially to at least part of the listener nodes 110 of the plurality of listener nodes 110, more especially to each listener node 110 of the plurality of listener nodes 110. In further embodiments, the target beacon signal, especially comprising the detection threshold range, may be arranged for enabling (each of) the listener nodes 110 (of the plurality of listener nodes 110) to set a (respective) receiver sensitivity to the detection threshold range.

[0119] In further embodiments, the predetermined goal number may comprise a desired goal number, and the target tag may be configured to minimize the deviation of the desired goal number of reached nodes and actual number of reached nodes.

[0120] FIG. 1 further schematically depicts an embodiment of the asset-tracking system 100 comprising a target tag 10. In the depicted embodiment, the asset-tracking system is configured for tracking the 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 may have a system operational mode, wherein in the system operational mode: (i) each of the plurality of listener nodes 110 is configured to detect the target beacon signal (of the 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.

[0121] FIG. 2 schematically depicts the tag operational mode 20 and the system operational mode 200.

[0122] The tag operational mode 20 may comprise a detection stage 22, a signal processing stage 23, and an execution stage 24. In the detection stage 22 the target tag 10 may (be configured to) detect listener beacon signals and determine related listener beacon signal strengths. In the signal processing stage 23 the target tag 10 may (be configured to) determine a tag transmission power T.sub.t based on the related listener beacon signal strengths, transmission power-related data, receiver sensitivity-related data, and a predetermined goal number of reached listener nodes. In the execution stage 24 the target tag 10 may (be configured to) emit the target beacon signal at the tag transmission power T.sub.t. In further embodiments, the target beacon signal may comprise instructions for the plurality of listener nodes 110 to adjust the detection threshold value.

[0123] In particular, as depicted in FIG. 2, the execution stage 24 may be repeated multiple times. The execution stage 24 may be repeated until the tag operational mode 20 is (re-)executed and, for example, restarts in the detection stage.

[0124] In embodiments, the target tag 10 may be configured to (re-)execute the tag operational mode according to a scanning frequency, especially wherein the scanning frequency is based on one or more of movement, battery life, and a predefined period. In further embodiments, the target tag 10 may be configured to (re-)execute the tag operational mode upon receiving an (external) tag calibration signal.

[0125] In embodiments, the target tag 10 may be configured to remain in the execution stage even if the target tag 10, is switched off and on again, i.e., the target tag may be configured only to execute the tag operational mode according to one or more of the scanning frequency and the tag calibration signal.

[0126] In further embodiments, the operational mode 20 may further comprise an initiation stage 21. In the initiation stage 21, the target tag may (be configured to) emit a listener beacon signal request signal. In particular, in embodiments (of the system), the plurality of listener nodes 110 are configured to emit listener beacon signals upon receiving the listener beacon signal request signal. Hence, the listener beacon signal request signal is configured to control the plurality of listener nodes to emit the listener beacon signals upon receiving the listener beacon signal request signal

[0127] The system operational mode 200 may comprise a beacon detection stage 201 and a localization stage 202. In the beacon detection stage 201, each of the plurality of listener nodes 110 may be configured to detect the target beacon signal and to provide a related target signal to the control system 300. It will be clear to the person skilled in the art, that although all of the listener nodes 110 may be configured to detect the target beacon signal, typically only a first subset of the listener nodes 110 may detect the target beacon signal and typically only a second subset (of the first subset) may report the a related target signal to the control system 300.

[0128] In the localization stage 202, the control system 300 may (be configured to) determine a target tag location of the target tag 10 based on the related target signals. In embodiments, the control system 300 may (be configured to) determine the target tag location of the target tag 10 based on the related target signals and one or more of listener location data and/or map data.

[0129] FIG. 2 further schematically depicts 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 stage 22 comprising detecting the listener beacon signals with the target tag 10 and determining related listener beacon signal strengths; a signal processing stage 23 comprising determining 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 goal number of reached listener nodes; and an execution stage 24 comprising emitting a target beacon signal with the target tag 10 at the tag transmission power.

[0130] FIG. 3 schematically depicts another embodiment of the asset-tracking system 100, wherein (at least part of a total number of) the plurality of listener nodes 110 are integrated in lighting devices 1000. In particular, FIG. 3 schematically depicts lighting devices 1000 comprising light generating devices, such as a lamp 1001, and a luminaire 1002, and a lighting control element 1003, such as a user interface, like a graphical user interface. Reference 1010 indicates the light that is generated by a lighting device 1000. Especially, this light is visible light, such as white light. The lighting control element 1003 may also be a portable device, such as an I-phone or Smartphone.

[0131] FIG. 3 also schematically depicts an embodiment of the lighting device 1000, wherein the lighting device 1000 comprises at least one of the listener nodes 110 of the invention for use in the asset-tracking system 100 of the invention.

[0132] The term “plurality” refers to two or more. Furthermore, the terms “a plurality of” and “a number of” may be used interchangeably.

[0133] The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Moreover, the terms “about” and “approximately” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. For numerical values it is to be understood that the terms “substantially”, “essentially”, “about”, and “approximately” may also relate to the range of 90%-110%, such as 95%-105%, especially 99%-101% of the values(s) it refers to.

[0134] The term “comprise” also includes embodiments wherein the term “comprises” means “consists of”.

[0135] The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

[0136] 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 invention described herein are capable of operation in other sequences than described or illustrated herein.

[0137] The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

[0138] The term “further embodiment” and similar terms may refer to an embodiment comprising the features of the previously discussed embodiment, but may also refer to an alternative embodiment.

[0139] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0140] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0141] Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, “include”, “including”, “contain”, “containing” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0142] The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

[0143] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may 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.

[0144] The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0145] The term “controlling” and similar terms herein especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and the element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a control system and one or more others may be slave control systems.

[0146] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. Moreover, if a method or an embodiment of the method is described being executed in a device, apparatus, or system, it will be understood that the device, apparatus, or system is suitable for or configured for (executing) the method or the embodiment of the method, respectively.

[0147] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

[0148] Amongst others, the invention involves a target tag configured to adjust the transmission power of its 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. For this, the target tag may determine the signal loss that occurs as listener beacon signals, emitted from the listener nodes, travel to the target tag, and may adjust its transmission power, accordingly, also considering the transmission power and sensitivity of the listener nodes.