Luminaire status detection by adjacent connected streetlights

Abstract

: A method for determining a light status of a target luminaire within a set of luminaires. Each luminaire comprises a light emitting portion and an at least one ambient light sensor. The method comprises, in response to an indication that the target luminaire is offline, receiving a current illumination value, measured by the at least one ambient light sensor of a neighboring luminaire adjacent to the target luminaire. The current illumination value is compared to a reference illumination value to determine the light status of the target luminaire. The light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

Description

[0001] Luminaire status detection by adjacent connected streetlights

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of luminaires, and in particular to methods of determining a light status of a luminaire.

[0004] BACKGROUND OF THE INVENTION

[0005] City wide connected lighting systems can monitor the status of luminaires distributed throughout an urban area. The luminaires transmit information to a server regarding the luminaire’s lighting output level, power consumption, etc., which can be viewed by an operator. If an abnormal status is detected, e.g., the lighting output is different to expected, the operator is notified and can dictate corresponding maintenance actions to a lighting engineer.

[0006] On occasion, certain luminaires may be unable to transmit information to the server due to connectivity issues. The status of the luminaire will be unknown, though may still be functioning properly, i.e., emitting light. This may prompt an unnecessary or nonurgent onsite visit to the luminaire to check its status, resulting in increased effort from the lighting engineer.

[0007] US2013200807A1 discloses a lighting fixture that self-estimates its power usage and monitors its health. The lighting fixture determines its power usage by sensing, by an ambient light sensor, an intensity of light emitted from the lighting fixture, and estimating power usage of the lighting fixture based on the sensed intensity of light.

[0008] Thus, there is a desire to provide a method for determining the status of a luminaire when it is unable to transmit information to a server.

[0009] SUMMARY OF THE INVENTION

[0010] The invention is defined by the claims.

[0011] According to examples in accordance with an aspect of the invention, there is provided a computer-implemented method for determining a light status of a target luminaire within a set of luminaires. Each luminaire in the set of luminaires comprises a light emitting portion and at least one ambient light sensor. The computer-implemented method comprises, in response to an indication that the target luminaire is offline: receiving a current illumination value from a neighboring luminaire adjacent to the target luminaire, measured by the at least one ambient light sensor of the neighboring luminaire, and determining the light status of the target luminaire by comparing the current illumination value to a reference illumination value. The light status of the target luminaire comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

[0012] The present disclosure provides a technique for determining whether or not a target luminaire is emitting or outputting light. More particularly, the proposed approached provides a mechanism for determining a light status of a target luminaire within a set of luminaires. The light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light. Each luminaire in the set of luminaires comprises a light emitting portion and at least one ambient light sensor.

[0013] The proposed method is performed in response to an indication that the target luminaire is offline. In the present context, the target luminaire being offline refers to an inability for the target luminaire to transmit information to an external device and / or external server, wherein the information transmitted by the target luminaire is at least indicative of the light status of the target luminaire.

[0014] The target luminaire may be indicated as being offline, for example, in response to the external device and / or external server not receiving information from the target luminaire within a predefined period of time, e.g., several hours, one day, etc. Alternatively, the target luminaire may be indicated as being offline from a user input.

[0015] In the absence of the information from the target luminaire, the light status of the target luminaire must be determined by an indirect method, i.e., not from information directly transmitted from the target luminaire.

[0016] In the proposed technique, the at least one ambient light sensor of a neighboring luminaire adjacent to the target luminaire is used to define a light level (“illumination value”) in the vicinity of the neighboring luminaire. The defined light level is compared to a reference value (“reference illumination value”) to make the decision as to whether or not the target luminaire is outputting light.

[0017] It has been recognized that the ambient light level detected by an ambient light sensor of a luminaire adjacent to the target luminaire will change responsive to the amount of light emitted by the target luminaire. Thus, it is possible to discriminate between instances of the target luminaire emitting light and not emitting light. In particular, it has been recognized that a reference illumination value can be defined that facilitates the discrimination between an ON state of “ON” (i.e., emitting light) and an OFF state of “OFF” (i.e., not emitting light).

[0018] The proposed approach therefore provides a method that includes receiving a current illumination value for a neighboring luminaire adjacent to the target luminaire, as measured by the at least one ambient light sensor of the neighboring luminaire. The current illumination value is then compared to a reference illumination value and used to determine the light status of the target luminaire.

[0019] In the context of the present disclosure, an illumination value may represent a brightness in the vicinity of the measuring light sensor.

[0020] The proposed method may further comprise, in response to an indication that the target luminaire is offline, identifying which of the luminaires, in the set of luminaires, is a neighboring luminaire to the target luminaire responsive to location data of each luminaire in the set of luminaires. This may comprise determining which luminaires in the set of luminaires are closest to the target luminaire.

[0021] Location data may comprise, for example, GPS coordinates of each luminaire within the set of luminaires.

[0022] In some examples, a task may be triggered responsive to the indication that the target luminaire is offline. A task may comprise, for example, a communication (e.g., to a lighting engineering) that there is a need to fix one or more faults with the target luminaire. Furthermore, a severity of the task may be responsive to the determined light status of the target luminaire. For example, if the target luminaire is determined to be ON, a low priority task may be triggered, e.g., as the target luminaire cannot transmit information but is otherwise working as intended (i.e., emitting light) and therefore does not urgently need to be fixed.

[0023] The step of determining the light status may comprise controlling the predictive indicator to indicate that the target luminaire is not outputting light responsive to the current illumination value falling below the reference illumination value. In other words, the target luminaire may be determined to be OFF in response to the current illumination value being below a threshold, i.e., the reference illumination value.

[0024] If the target luminaire is not outputting light, the current illumination value measured by the at least one ambient light sensor of the neighboring luminaire will reduce (i.e., compared to when the target luminaire is outputting light), thereby falling below the reference illumination value. The target luminaire may thus be determined to be OFF in response to the current illumination value being below the reference illumination value. In some examples, the current illumination value may be measured only when the neighboring luminaire is outputting light. In this way, certain instances where the light status of the target luminaire may be incorrectly determined can be avoided, e.g., the current illumination value being below the reference illumination value due to the neighboring luminaire not outputting light, resulting in the target luminaire being determined as OFF when it may be ON.

[0025] The reference illumination value may be responsive to a previous illumination value measured by the at least one ambient light sensor of the neighboring luminaire. The previous illumination value may refer to an illumination value measured, by the at least one ambient light sensor of the neighboring luminaire, any time prior to the current illumination value, e.g., one hour before, one day before, etc. Preferably, the previous illumination value may refer to an illumination value measured, prior to the current illumination value, when the target luminaire was known to be outputting light. In this way, the reference illumination value may effectively represent an expected light level within the vicinity of the neighboring luminaire when the target luminaire is ON (i.e., emitting light).

[0026] A measured illumination value (i.e., a current and / or previous illumination value) may be assumed to comprise three light contributions: light from luminaires, light from artificial light sources (e.g., cars, buildings, etc.), and light from the environment (e.g., moon light). The at least one ambient light sensor may not be able to distinguish between different light contributions. Therefore, to accurately determine the luminaire light level contribution (which may be indicative of a target luminaire’s light status) changes in the environmental and the artificial light contributions between different illumination value measurements should desirably be minimized and / or accounted for.

[0027] In some examples, the current illumination value and the previous illumination value may be measured, by the at least one ambient light sensor of the neighboring luminaire, at the same time of day. The same time of day may define a specific time, e.g., 3:20 AM, or a time window, e.g., between 2:00 AM and 3:00 AM, or a period of the day, e.g., nighttime. In this way, differences between the artificial light contribution for the current illumination value and the previous illumination value may be minimized.

[0028] Furthermore, the current illumination value (and previous illumination value) may be measured, by the at least one ambient light sensor of the neighboring luminaire, within a predefined time window during the day and / or a predefined time of day. In this way, a time (window) may be chosen which minimizes the artificial light contribution, e.g., between 2:00 AM and 3:00 AM when there is minimal street activity. In some examples, at least the neighboring luminaire may comprise a motion sensor, configured to detect the presence or absence of movement in the vicinity of the neighboring luminaire. Furthermore, the current illumination value and the previous illumination value may be measured, by the at least one ambient light sensor of the neighboring luminaire, when the motion sensor detects the absence of movement in the vicinity of the neighboring luminaire. In this way, the artificial light contribution to the current illumination value and the previous illumination value from moving entities that may travel past the neighboring luminaire (e.g., cars, pedestrians) may be minimized.

[0029] The environmental light contribution may naturally vary due to environmental factors, e.g., moon cycle, cloudiness, weather, air particulates, etc. Changes in the environmental light contribution should desirably be accounted for when determining the light status of the target luminaire, specifically when comparing the current illumination value and the reference illumination value.

[0030] A proposed approach may be to adjust the reference illumination value such that it is representative of a current environmental light contribution. More specifically, the reference illumination may be adjusted (i.e., increased or decreased) based on or responsive to a determined change in the environmental light contribution.

[0031] One possible technique to determine the change in the environmental light contribution may be to measure the difference between a further current illumination value and a further previous illumination value measured by the at least one ambient light sensor of a further luminaire, different to the target luminaire and the neighboring luminaire. Preferably, the light status of the further luminaire and the light status of luminaires adjacent to the further luminaire may be the same as when the further previous illumination value was measured. In this way, any difference between the further current illumination value and the further previous illumination value may be assumed to come primarily from changes in the environmental light contribution.

[0032] The reference illumination value may thus be adjusted by the determined change in the environmental light contribution. In other words, the reference illumination value may be further responsive to the difference between a further current illumination value and a further previous illumination value measured by the at least one ambient light sensor of a further luminaire, different to the target luminaire and the neighboring luminaire.

[0033] Another possible technique to determine the change in the environmental light contribution may be to use a “two-sensor” luminaire configuration. More specifically, the at least one ambient light sensor may comprise a first ambient light sensor, facing a first direction, and a second ambient light sensor facing a second direction opposite to the first direction. For instance, the first ambient light sensor may be configured to face downwards, and the second ambient light sensor may be configured to face upwards. In this way, the second ambient light sensor may measure a (second) illumination value corresponding solely to the environmental light contribution.

[0034] The change in the environmental light contribution may thus be determined from the difference between a previous second illumination value and a current second illumination value.

[0035] In operation, the target luminaire may have more than one neighboring luminaire, e.g., two neighbors when the luminaires are arranged in a line along a path. Accordingly, the light status of the target luminaire may be determined by comparison of the current illumination value and the reference illumination value of more than one neighboring luminaire. This allows for a “double-checking” technique to provide greater validity to the determined light status of the target luminaire.

[0036] Thus, the computer-implemented method may further comprise, for each of one or more additional neighboring luminaires in the set of luminaires, receiving a respective additional current illumination value measured by the at least one ambient light sensor of the additional neighboring luminaire. Each additional neighboring luminaire may be adjacent to the target luminaire. Additionally, the step of determining the light status of the target luminaire may further comprise, for each one or more additional neighboring luminaire, comparing the respective additional current illumination value to a respective additional reference illumination value for the additional neighboring luminaire, such that each additional current illumination value is associated with a respective additional reference illumination value.

[0037] In some examples, the step of determining the light status of the target luminaire may comprise controlling the predictive indicator to indicate that the target luminaire is not outputting light responsive to the current illumination value falling below the reference illumination value and each additional current illumination value falling below its respective additional reference illumination value. In this way, the target luminaire may be confidently determined to be OFF.

[0038] There is also provided a processing system configured to determining a light status of a target luminaire within a set of luminaires, wherein each luminaire in the set of luminaires comprises a light emitting portion and at least one ambient light sensor. The processing system is configured to, in response to an indication that the target luminaire is offline, receive a current illumination value from a neighboring luminaire adjacent to the target luminaire, measured by the at least one ambient light sensor of the neighboring luminaire, and determine the light status of the target luminaire by comparing the current illumination value to a reference illumination value, wherein the light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

[0039] There is also provided a computer program product comprising computer program code means which, when executed on a computing device having a processing system according to the above example, cause the processing system to perform all of the steps of the method according to the present disclosure.

[0040] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0043] Fig. 1 illustrates a set of luminaires;

[0044] Fig. 2 is a flowchart illustrating a proposed method;

[0045] Fig. 3 illustrates the set of luminaires at a past and present time;

[0046] Fig. 4 is a flowchart illustrating another proposed method;

[0047] Fig. 5 illustrates the set of luminaires at another past and present time;

[0048] Fig. 6 is a flowchart illustrating another proposed method;

[0049] Fig. 7 illustrates a luminaire according to an example;

[0050] Fig. 8 illustrates another set of luminaires at a past and a present time according to the luminaire of Fig. 7;

[0051] Fig. 9 is a flowchart illustrating another proposed method;

[0052] Fig. 10 illustrates a luminaire according to another example; and Fig. 11 is a flowchart illustrating another proposed method.

[0053] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The invention will be described with reference to the Figures.

[0055] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0056] The invention provides a method for determining a light status of a target luminaire within a set of luminaires. The light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light. Additionally, each luminaire within the set of luminaires comprises a light emitting portion and at least one ambient light sensor.

[0057] The method includes, in response to an indication that the target luminaire is offline, receiving a current illumination value from a neighboring luminaire (also within the set of luminaires) adjacent to the target luminaire. The current illumination value is measured by the at least one ambient light sensor of the neighboring luminaire and is indicative of an ambient light level within the vicinity of the neighboring luminaire. The current illumination value is then compared to a reference illumination value for the neighboring luminaire and used to determine the light status of the target luminaire.

[0058] The set of luminaires may comprise, though is not limited to, a streetlighting system in an outdoor urban setting. Accordingly, each luminaire within the set of luminaires may be a streetlamp configured to provide light to an area surrounding the streetlamp.

[0059] Figure 1 illustrates a set of luminaires 100 comprising five individual luminaires A-E. It shall be understood that the set of luminaires may comprise any number of luminaires and the choice of five luminaires within the example of Figure 1 is arbitrary.

[0060] Each luminaire within the set of luminaires 100 comprises a light emitting portion 102, configured to output light towards the ground, and at least one ambient light sensor 104. The at least one ambient light sensor 104 is sensitive to the ambient light level in the vicinity of the luminaire and is used to define an illumination value indicative of the ambient light level.

[0061] A target luminaire 110 may be chosen for which a light status will desirably be determined. In Figure 1, luminaire B has been labelled as the target luminaire 110, though it shall be understood that any luminaire A-E within the set of luminaires 100 may be considered a target luminaire.

[0062] The target luminaire 110 has at least one neighboring luminaire 120 (luminaires A and C) that is adjacent to the target luminaire 110 and within the set of luminaires 100. The at least one ambient light sensor 104 of the neighboring luminaire 120 measures an illumination value that is indicative of the ambient light level in the vicinity of the neighboring luminaire 120 and, hence, sensitive to the amount of light emitted by the target luminaire 110.

[0063] An illumination value may be a numeric value that represents a brightness in the vicinity of the measuring luminaire, e.g., a value for a physical quantity.

[0064] Each luminaire A-E in the set of luminaires 100 can transmit information to an external device and / or an external server (not shown). For example, the information may be transmitted to a cloud server where it may be presented to a user, e.g., an operator. Alternatively or additionally, the information may be transmitted to an external processing system where it may be processed and / or analyzed.

[0065] The information may at least be indicative of (e.g., usable to derive or derived from) the light status of the luminaire that transmitted the information. For example, the information may comprise an ambient light level, measured by the at least one ambient light sensor of the luminaire, and / or a power consumption of the luminaire. By processing the information transmitted by a luminaire, it may be possible to determine the light status of the luminaire.

[0066] In some instances, a luminaire may be unable to transmit information, e.g., due to a fault with the luminaire. In such cases, the luminaire is considered as being “offline”, i.e., the luminaire is unable to communicate with an external device and / or external server. The light status of the target luminaire therefore cannot be determined directly from the information transmitted by the luminaire. It would thus be desirable for a technique to determine a light status of a luminaire when it is offline.

[0067] Figure 2 shows a flowchart illustrating a proposed method 200 for determining a light status of a target luminaire. The method may be performed, for instance, by the external device and / or external server.

[0068] The method 200 comprises a step 210 of determining if the target luminaire is offline. Specifically, step 210 determines if there is an indication that the target luminaire is offline.

[0069] The target luminaire may be indicated as being offline in response to a / the external device and / or external server (or another luminaire of the set of luminaires) not receiving information from the target luminaire within a predefined period of time, e.g., several hours, one day, etc. This approach may be appropriate when the target luminaire is configured to periodically transmit information to the external device and / or external server and, therefore, there is an expected period of time during which the external device and / or external server expects to receive information from the target luminaire.

[0070] Alternatively, the target luminaire may be indicated as being offline from a user input., e.g., an operator may deem the target luminaire as being offline if the operator is unable to request information from the target luminaire. As another example, the target luminaire may be determined to be offline if it fails to respond to a predetermined number of enquiries, e.g., produced by the external device and / or server. Other suitable approaches for generating an indication that the target luminaire is offline will be apparent to the skilled person.

[0071] In response to a negative determination for step 210, the method 200 may proceed to a step 215 to indicate that the target luminaire is “online”, i.e., that the target luminaire is not offline. In such cases, the target luminaire is able to transmit information to an external device and / or an external server, and the light status of the target luminaire may be determined from the transmitted information. Thus, proceeding to step 215 is indicative that the method 200 is not required to determine the light status of the target luminaire.

[0072] The method 200 further comprises a step 220 of receiving a current illumination value for a neighboring luminaire adjacent to the target luminaire. Step 220 is only triggered if there is an indication that the target luminaire is offline, i.e., a positive determination is made for step 210.

[0073] The current illumination value may be a most recently measured illumination value produced by the at least one ambient light sensor of the neighboring luminaire. The current illumination value is therefore indicative of the ambient light level in the vicinity of the neighboring luminaire.

[0074] The current illumination value may be received by the external device and / or the external server. In other words, the neighboring luminaire (which is online) may transmit the current illumination value to the external device and / or the external server.

[0075] The method 200 further comprises a step 230 of determining the light status of the target luminaire by comparing the current illumination value to a reference illumination value. The reference illumination value is associated with the neighboring luminaire and may represent a threshold value for which the current illumination value is compared against, i.e., determining if the current illumination value is higher, lower, or the same as the reference illumination value.

[0076] Each luminaire within the set of luminaires may possess or be otherwise associated with its own reference illumination value. The reference illumination value of each luminaire may be indicative of an expected light level in the vicinity of the luminaire, i.e., the expected brightness when the light emitting portion of all nearby luminaires are outputting light. The comparison performed in step 230 may thus represent a determination of whether a current illumination value (e.g., measured light level) is as expected (i.e., when all luminaires are correctly emitting light).

[0077] It is therefore possible to infer whether or not a nearby luminaire (e.g., the target luminaire) is outputting light from the comparison of step 230 by assessing whether or not a current light level meets an expected light level. More specifically, it is possible to determine the light status of the target luminaire from step 230.

[0078] The light status comprises at least a predictive indicator of whether or not the target luminaire (or more specifically, the light emitting portion of the target luminaire) is outputting light. That is, the light status is indicative of at least whether or not the target luminaire, at a particular moment, is “ON” (i.e., emitting light) or “OFF” (i.e., not emitting light). Thus, the light status may comprise data or information that includes at least the predictive indicator.

[0079] Step 230 may comprise controlling the predictive indicator in response to the comparison of the current illumination value with the reference illumination value. For instance, if the current illumination value, as measured by the at least one ambient light sensor of the neighboring luminaire, does not breach the reference illumination value, the predictive indicator may indicate that the target luminaire is not outputting light, i.e., that the target luminaire is OFF (in step 421), otherwise the target luminaire is determined to be ON (in step 422). For instance, if a lower current illumination value indicates a lower (detected) light level, then if the current illumination is below the reference illumination value, then the predictive indicator may indicate that the target luminaire is not outputting light, i.e., that the target luminaire is OFF.

[0080] The light status of the target luminaire, as determined by step 230, may also comprise an indicator of the light output level (i.e., the brightness) of the target luminaire. For example, the comparison of the current illumination value with the reference illumination may also comprise determining the difference between the current illumination value and the reference illumination value. The difference may represent a deviation from an expected light output level of the target luminaire and, thus, is indicative of the present light output level of the target luminaire. This can help establish, for instance, whether or not the target luminaire is outputting the correct or an expected amount of light. This provides additional information beyond the mere indication of whether or not the target luminaire is outputting light for use in controlling and understanding the operation of the set of luminaires.

[0081] The method 200 may also comprise, in response to a positive determination in step 210, a step 240 of identifying which luminaires, in the set of luminaires, is a neighboring luminaire adjacent to the target luminaire. Step 240 is therefore performed prior to step 220 and may be used to identify a neighboring luminaire for the purposes of step 220, i.e., at least one neighboring luminaire to receive a current illumination value for.

[0082] A neighboring luminaire may be identified responsive to location data for each luminaire in the set of luminaires. The location data for a luminaire may be at least responsive to changes in distance between each of the set of luminaires. For instance, the location data may be indicative of the position of the luminaire, e.g., GPS coordinates or WPS positioning system data. As another example, the location data may comprise signal strength data (e.g., RSSI) between pairs of luminaires in the set of luminaires and / or between each luminaire and a central device). In this way, the relative positions of luminaires with other luminaires can be determined.

[0083] A luminaire may be determined to be a neighboring luminaire to the target luminaire when the relative position or distance between the luminaire and the target luminaire meets one or more criteria. For example, the luminaire may be determined to be a neighboring luminaire when the distance between the luminaire and the target luminaire is below a predefined threshold. Alternatively, the luminaire may be determined to be a neighboring luminaire when there is not another luminaire between the luminaire and the target luminaire, e.g., there is not another luminaire within a certain distance of a straight line drawn between the luminaire and the target luminaire.

[0084] In some examples, a task may be triggered (not shown in Figure 2) responsive to the indication that the target luminaire is offline, i.e., in response to a positive determination in step 210. The task may at least comprise a communication indicating a desired action for addressing the offline state of the target luminaire, e.g., a communication to a lighting engineering to visit the target luminaire to fix one or more faults with the target luminaire, such that the target luminaire becomes online.

[0085] Additionally, the task may comprise an indication of one or more further actions (of varying importance) depending on the determined light status of the target luminaire. In other words, a severity of the task, i.e., how many actions the task comprises and the urgency of said actions, may be responsive to the determined light status of the target luminaire (i.e., responsive to step 230). For example, if the target luminaire is determined to be ON, a low priority task may be triggered, e.g., as the target luminaire cannot transmit information but is otherwise working as intended (i.e., emitting light) and therefore does not urgently need to be fixed. Alternatively, a high priority task, comprising multiple actions, may be triggered if the target luminaire is determined to not be outputting light.

[0086] The following examples are designed to explain how the method 200 may be used in practice. For simplicity, throughout the description below, a luminaire B is designated as the target luminaire and luminaire A is designated as the neighboring luminaire. However, from the following examples, it will be clear to the skilled person how the present method could be applied to any luminaire, i.e., that any luminaire could operate as the target luminaire. In such cases, the corresponding neighboring luminaire(s) will be clear to the skilled person.

[0087] Figure 3 shows the set of luminaires 100 at a past time and a present time (i.e., a first point in time tl and a second later point in time t2). The present time may be considered as any time at which the light status of the target luminaire 110 is to be determined. The past time may be considered as any time before the present time, but, preferably, a time when the target luminaire 110 was (known to be) outputting light (as depicted in Figure 3).

[0088] The at least one ambient light sensor 104 of the neighboring luminaire 120 measures a previous illumination value 310 at the past time. The previous illumination value 310 is dependent on the amount of light emitted by (and hence light status of) the target luminaire 110 at the past time. Similarly, a current illumination value 320 is measured by the at least one ambient light sensor 104 of the neighboring luminaire 120 at the present time.

[0089] The previous illumination value 310 may correspond to a past current illumination value, i.e., an illumination value that was measured in the past and compared to a reference illumination value to determine a past light status of the target luminaire 110.

[0090] The previous illumination value 310 may be stored within a memory device (not shown in Figure 3) at the past time. In this way, the previous illumination value 310 may be accessed at a later time (e.g., the present time). Accordingly, the past light status of the target luminaire 110 may be determined at the later time by accessing the previous illumination value 310.

[0091] The memory device may be part of an external device or may be able to communicate with an external server, to which the target luminaire and the neighboring luminaire may transmit information to when online. Figure 4 shows a flowchart illustrating a method 400 (similar to the method 200 of Figure 2) that makes use of the environment illustrated by Figure 3.

[0092] The method 400 is usable to determine the light status of the target luminaire based on (i.e., responsive to) the previous illumination value 310 and the current illumination value 320, as measured by the at least one ambient light sensor of the neighboring luminaire at the past time and the present time, respectively.

[0093] The method 400 comprises previously described steps 210 and 220 for receiving the current illumination value 320, in response to an indication that the target luminaire is offline.

[0094] Additionally, the method 400 comprises a step 410 of setting a reference illumination value 330 responsive to the previous illumination value 310. For example, this may include setting the reference illumination value 330 to be equal to the previous illumination value 310. As another example, this may comprise setting the reference illumination value 330 to be a predetermined percentage of the previous illumination value, e.g., a percentage between 60% and 100%. This embodiment may be useful to account, for example, for minor fluctuations in brightness - e.g., due to minor changes in environmental conditions and / or allowable power fluctuations in a supply for the luminaire(s). Other example approaches are discussed later in the disclosure.

[0095] In some examples, the previous illumination value 310 is measured at a past time when the target luminaire is outputting light. In this way, the reference illumination value 330, set responsive to the previous illumination value 310, may represent an expected light level in the vicinity of the neighboring luminaire when the target luminaire is outputting light.

[0096] The method 400 also comprises previously described step 230. Step 230 may include a step 420 of determining whether or not the current illumination value 320 breaches the reference illumination value 330. For instance, if a lower current illumination value indicates a lower (detected) light level, then step 420 may comprise determining whether or not the current illumination value 320 is less than the reference illumination value. This may effectively represent a type of comparison between the current illumination value 320 and the reference illumination value 330.

[0097] When set using a previous illumination value measured when the target luminaire was outputting light, the reference illumination value 330 may effectively represent an expected (current) illumination value, measured by the at least one ambient light sensor of the neighboring luminaire, when the target luminaire is ON. Step 420 therefore allows the method to discriminate between the target luminaire being ON or OFF at the present time from whether or not the current illumination value 320 breaches the reference illumination value 330.

[0098] More specifically, in response to the current illumination value 320 breaching the reference illumination value 330 (i.e., a positive determination in step 420) the target luminaire may be determined to be OFF. By contrast, in response to the current illumination value 320 failing to breach the reference illumination value 330 (i.e., a negative determination in step 420) the target luminaire may be determined to be ON.

[0099] The method 400 therefore demonstrates an approach of determining the light status of the target luminaire from (changes in) the ambient light level in the vicinity of the neighboring luminaire, adjacent to the target luminaire.

[0100] So far, the ambient light level in the vicinity of a luminaire has been assumed to depend only on the light emitted by nearby luminaires. However, in practice, there may be (other) background contributions to the ambient light level.

[0101] By way of example, in an outdoor setting (e.g., in the case of streetlighting) there is expected to be an environmental light contribution to the ambient light level during use of the luminaires (s), e.g., moonlight and / or light pollution. This may vary over time (e.g., from day-to-day) due to natural changes in the environment, e.g., moon cycle, cloudiness, weather, etc. An illumination value measured at one time may thus be different to another illumination value measured at another time due to changes in the environmental light contribution, even if the ambient light contribution from luminaires stays the same between the two measurements.

[0102] It may therefore be desirable to account for changes in the environmental light contribution when determining the light status of the target luminaire. This is to avoid a scenario that may result in determining the wrong light status e.g., the current illumination value being below the reference illumination value due to a reduction in the environmental light contribution rather than the target luminaire not emitting light.

[0103] Accordingly, it may be desirable to adjust the reference illumination value responsive to the change in the environmental light contribution, such that the comparison between the current illumination value and the reference illumination value is representative of the current environmental light contribution.

[0104] The following examples are designed to explain possible methods of determining a light status of a target luminaire which include adjusting a reference illumination value according to an estimated change in an environmental light contribution. Figure 5 shows the set of luminaires 100 at another past time and another present time (i.e., a first point in time tl and a second later point in time t2). The past time has been depicted with a moon obscured by a cloud and the present time has been depicted with an unobscured moon. This is representative of the past time having a different environmental light contribution compared to the present time. More specifically, the past time has been depicted with a smaller environmental light contribution than the present time, i.e., due to the moon light being blocked by clouds. It shall be understood, however, that this choice is purely arbitrary.

[0105] The at least one ambient light sensor 104 of the neighboring luminaire 120 measures the previous illumination value 310 at the past time. Similarly, the current illumination value 320 is measured by the at least one ambient light sensor 104 of the neighboring luminaire 120 at the present time.

[0106] Additionally, a further previous illumination value 510 and a further current illumination value 520 may be measured by the at least one ambient light sensor 104 of a further luminaire 130 (luminaire D) at the past time and the present time, respectively. The further luminaire 130 is different to both the target luminaire 110 and the neighboring luminaire 120 and within the set of luminaires 100.

[0107] The further luminaire 130 may ideally be a luminaire whose light status, and whose adjacent luminaire’s light statuses, are the same at the present time as they were at the past time. For example, the further luminaire 130 and the luminaires adjacent to the further luminaire may all be ON (i.e., outputting light) at the present time and the past time. In this way, the contribution to the light level in the vicinity of the further luminaire 130 from just luminaires may be substantially the same between the two times. Therefore, a measured difference between the illumination value of the further luminaire 130 at the past time and the present time, i.e., a difference between the further previous illumination value 510 and the further current illumination value 520, may be considered or treated as coming primarily from changes in the environmental light contribution.

[0108] The luminaires adjacent to the further luminaire 130 do not include the target luminaire 110 but may include the neighboring luminaire 120.

[0109] Figure 6 shows a flowchart illustrating a method 600 for determining the light status of the target luminaire making use of the environment illustrated by Figure 5.

[0110] The method 600 comprises previously described step 410. In the present case, the reference illumination value represents an ambient light level in the vicinity of the neighboring luminaire at the past time, comprised of light contributions from luminaires (nearby to the neighboring luminaire) and from the environment.

[0111] The method 600 further comprises a step 605 of determining a change in the environmental light contribution between the past time and the present time. The change in the environmental light contribution may be determined / estimated from the difference between the further current illumination value 520 and the further previous illumination value 510, as measured by the at least one ambient light sensor of the further luminaire.

[0112] More specifically, the change in the environmental light contribution may be given by subtracting the further previous illumination value 510 away from the further current illumination value 520. The change in the environmental light contribution may hence have a positive or a negative value depending on the relative magnitude of the further previous illumination value 510 and the further current illumination value 520.

[0113] For example, the change in the environmental light contribution may be positive when the further current illumination value 520 is greater than the further previous illumination value 510. This may correspond to the environmental light contribution being greater at the present time compared to the past time due to a change in the environment, e.g., reduced cloud coverage at the present time compared to the past time (as depicted in Figure 5). Conversely, a negative change in the environmental light contribution may correspond to the environmental light contribution being smaller at the present time compared to the past time.

[0114] Step 605 may therefore provide a positive or a negative value that is representative of the change in the environmental contribution between the past time and the present time.

[0115] The method 600 further comprises a step 610 of adjusting the reference illumination value 330 (as initially set by step 410) according to the determined change in the environmental light contribution, i.e., from the result of step 605. This may include increasing or decreasing the reference illumination value 330 based on the change in the environmental light contribution.

[0116] When the change in the environmental light contribution is represented by a positive or a negative value, step 610 may comprise adding the change in the environmental light contribution to the reference illumination value 330. In other words, if the change in the environmental light contribution is positive, the reference illumination value 330 may increase by the magnitude of the change in the environmental light contribution. Alternatively, if the change in the environmental light contribution is negative, the reference illumination value 330 may decrease by the magnitude of the change in the environmental light contribution.

[0117] The reference illumination value 330, as set by step 410, may effectively represent an expected light level when the target luminaire is ON and the environmental light contribution is the same as at the past time. Step 610 therefore adjusts the reference illumination value 330 so that the reference illumination value 330 may effectively represent an expected light level when the target luminaire is ON and the environmental light contribution is the same as at the present time.

[0118] After step 610, the reference illumination value 330 may therefore comprise substantially the same environmental contribution as the current illumination value 330.

[0119] The method 600 further comprises previously described steps 210 and 220 for receiving the current illumination value 320, in response to an indication that the target luminaire is offline.

[0120] The method 600 also comprises previously described step 230. Using the approach of the method 600, the step of determining the light status of the target luminaire may effectively take into account the environmental light contribution.

[0121] An alternative method of determining a change in an environment light contribution may be to use a luminaire with a “two-sensor” configuration.

[0122] Figure 7 shows an example of a luminaire with a two-sensor configuration. In this example, the luminaire comprises a first ambient light sensor 104a and a second ambient light sensor 104b. The first ambient light sensor 104a faces a first direction and the second ambient light sensor 104b faces a second direction, opposite to the first direction, i.e., the first and second ambient light sensors face away from each other.

[0123] In operation, the first ambient light sensor 104a may be configured to face downwards, i.e., towards the ground, corresponding to facing the same direction as the light emitting portion 102. In this configuration, the first ambient light sensor 104a may measure a first illumination value comprising contributions from nearby luminaires and the environment. Conversely, the second ambient light sensor 104b may be configured to face upwards, i.e., towards the sky. In this configuration, the second ambient light sensor 104b may measure a second illumination value comprising only an environmental light contribution, i.e., as the second ambient light sensor 104b is facing away from the light emitted by nearby luminaires.

[0124] In this way, the environmental light contribution may be measured directly by the second ambient light sensor 104b and used to adjust the reference illumination value. Figure 8 shows a set of luminaires 800 at a past time and a present time (i.e., a first point in time tl and a second later point in time t2). Each luminaire in the set of luminaires 800 is configured according to the example of Figure 7, i.e., each luminaire comprises a first ambient light sensor 104a and a second ambient light sensor 104b. The first ambient light sensor 104a of each luminaire is configured to face downwards and the second ambient light sensor 104b is configured to face upwards.

[0125] The first ambient light sensor 104a of the neighboring luminaire 120 measures a first previous illumination value 810a at the past time. Similarly, a first current illumination value 820a is measured by the first ambient light sensor 104a of the neighboring luminaire 120 at the present time. The first previous illumination value 810a and the first current illumination value 820a may represent a total ambient light level (i.e., due to contributions from all nearby luminaires and background contributions) at the past time and the present time, respectively.

[0126] Additionally, the second ambient light sensor 104b of the neighboring luminaire measures a second previous illumination value 810b at the past time. Similarly, a second current illumination value is measured by the second ambient light sensor 104b of the neighboring luminaire 120 at the present time. The second previous illumination value 810b and the second current illumination value 820b may represent an environmental ambient light level (i.e., due to an environment light contribution) at the past time and the present time, respectively.

[0127] In this way, the environmental light contribution may be determined directly from the ambient light level measured by the second ambient light sensor 104b.

[0128] Figure 9 shows a flowchart illustrating a method 900, making use of the environment illustrated by Figure 8, for determining a light status of a target luminaire.

[0129] The method 900 comprises a step 902 of setting the reference illumination value 330 responsive to the first previous illumination value 810a, as measured by the first ambient light sensor of the neighboring luminaire at the past time. For example, the reference illumination value 330 may be set to be equal to the first previous illumination value 810a. In the present case, the reference illumination value 330 represents an ambient light level in the vicinity of the neighboring luminaire at the past time, comprised of light contributions from luminaires (nearby to the neighboring luminaire) and from the environment.

[0130] The method 900 further comprises a step 905 of determining a change in the environmental light contribution between the past time and the present time. The change in the environmental light contribution may be determined / estimated from the difference between the second current illumination value 820b and the second previous illumination value 810b, as measured by the second ambient light sensor of the neighboring luminaire.

[0131] More specifically, the change in the environmental light contribution may be given by subtracting the second previous illumination value 810b away from the second current illumination value 820b. The change in the environmental light contribution may hence have a positive or a negative value depending on the relative magnitude of the second previous illumination value 810b and the second current illumination value 820b.

[0132] For example, the change in the environmental light contribution may be positive when the second current illumination value 820b is greater than the second previous illumination value 810b. This may correspond to the environmental light contribution being greater at the present time compared to the past time due to a change in the environment, e.g., reduced cloud coverage at the present time compared to the past time (as depicted in Figure 9). Conversely, a negative change in the environmental light contribution may correspond to the environmental light contribution being smaller at the present time compared to the past time.

[0133] Step 905 may therefore provide a positive or a negative value that is representative of the change in the environmental contribution between the past time and the present time.

[0134] The method 900 further comprises a step 910 of adjusting the reference illumination value 330 (as initially set by step 902) according to the determined change in the environmental light contribution, i.e., from the result of step 905. This may include increasing or decreasing the reference illumination value 330 based on the change in the environmental light contribution.

[0135] When the change in the environmental light contribution is represented by a positive or a negative value, step 910 may comprise adding the change in the environmental light contribution to the reference illumination value 330. In other words, if the change in the environmental light contribution is positive, the reference illumination value 330 may increase by the magnitude of the change in the environmental light contribution. Alternatively, if the change in the environmental light contribution is negative, the reference illumination value 330 may decrease by the magnitude of the change in the environmental light contribution.

[0136] The reference illumination value 330, as set by step 902, may effectively represent an expected light level when the target luminaire is ON and the environmental light contribution is the same as at the past time. Step 910 therefore adjusts the reference illumination value 330 so that the reference illumination value 330 may effectively represent an expected light level when the target luminaire is ON and the environmental light contribution is the same as at the present time.

[0137] After step 910, the reference illumination value 330 may therefore comprise substantially the same environmental contribution as the first current illumination value 820a.

[0138] The method 900 further comprises previously described step 210 and step 920, for receiving the first current illumination value 820a, in response to an indication that the target luminaire is offline.

[0139] The method 900 also comprises previously described step 230. Using the approach of the method 900, the step of determining the light status of the target luminaire may hence take into account the environmental light contribution.

[0140] In an alternative approach, when using a two-sensor configuration, the environmental light contribution may be accounted for by subtracting the second illumination value from the first illumination value. More specifically, when the second illumination value represents the environmental light contribution, and the first illumination value represents the total ambient light level (in the vicinity of the neighboring luminaire) the environmental light contribution may be removed by subtracting the second illumination value from the first illumination value. In this way, the resulting illumination value may be comprised primarily by light contributions from luminaires, i.e., and not comprise an environmental light contribution.

[0141] Using the above approach, the environmental light contribution may be removed from a corresponding illumination value (i.e., a current illumination value and a reference illumination value). In this way, the step of determining the light status of the target luminaire may be responsive only to the light contributions from luminaires and not from the environmental light contribution.

[0142] In addition to the environmental light contribution, further background contributions to the measured ambient light level may be expected due to artificial light sources, such as cars and buildings, i.e., light pollution. Accordingly, it may be desirable to account for an artificial light contribution when determining the light status of a target luminaire, specifically when comparing a current illumination value to a reference illumination value.

[0143] In a proposed approach, to minimize variations in the measured artificial light contribution between different ambient light measurements, it may be desirable to measure a current illumination value and a previous illumination value at a same time of day. Put another way, a past time, when a previous illumination value is measured, and a present time, when a current illumination value is measured, may correspond to the same time of day (i.e., on different days).

[0144] The same time of day may define a specific time, e.g., 3:20 AM, or a time window, e.g., between 2:00 AM and 3:00 AM, or a period of the day, e.g., nighttime, twilight or dusk.

[0145] Certain artificial light sources may have a substantially systematic timedependence, i.e., the amount of light output by an artificial light source as a function of time may be (modelled as being) substantially the same between consecutive days. This may be the case for building lights that predominantly turn off after a specific time, e.g., due to businesses closing for the evening, people going to sleep, etc. By measuring the ambient light level at the same time of day, changes in the artificial light contribution between different measurements may be minimized. In other words, when measured at the same time of day, the artificial light contribution from certain artificial light sources may be substantially the same for the current illumination value and the previous illumination value.

[0146] As another example, a specific time of day may be chosen that minimizes the artificial light contribution, thereby reducing the influence of artificial light sources on a measured light level. For example, an illumination value may always be measured between 2:00 AM and 3:00 AM, i.e., when many building lights have turned off and there is a minimal number of cars on the road.

[0147] Furthermore, it may be desirable to measure an illumination value, by the at least one ambient light sensor of a luminaire, when there is an absence of movement in the vicinity of the luminaire. In this way, the artificial light contribution from entities travelling close to the luminaire, e.g., cars, pedestrians carrying light emitting objects, etc., may be minimized.

[0148] Figure 10 shows an example of a luminaire further comprising a motion sensor 106. The motion sensor may be configured to detect the presence or absence of movement in the vicinity of the luminaire.

[0149] In a proposed approach, an illumination value (e.g., a current illumination value and / or a previous illumination value) may be measured, by the at least one ambient light sensor of the luminaire, when the motion sensor 106 detects the absence of movement in the vicinity of the luminaire. In this way, the illumination value may be measured when there is an absence of cars 1000 and / or pedestrians in the vicinity of the luminaire, thereby reducing the artificial light contribution to the measured light level. In the context of determining a light status of a target luminaire, at least a neighboring luminaire, adjacent to the target luminaire, may comprise a motion sensor. However, any additional luminaire within the set of luminaires may also comprise a motion sensor.

[0150] In operation, a target luminaire may have more than one neighboring luminaire. For example, for the set of luminaires 100 illustrated in Figures 1, 3, and 5, the target luminaire 110 (luminaire B) may have two neighboring luminaires 120 (luminaires A and C). Correspondingly, each neighboring luminaire 120 may determine a respective light status for the target luminaire 110. This allows for a “double-checking” technique, whereby respective light statuses for a target luminaire are compared with each other to either provide greater validity to the determined light status of the target luminaire and / or increased contextual information regarding the light status of other luminaires nearby to the target luminaire.

[0151] Figure 11 shows a flowchart illustrating a proposed method 1100 for determining a light status of a target luminaire.

[0152] The method 1100 comprises previously described steps 210 and 220 for receiving a current illumination value from a neighboring luminaire adjacent to the target luminaire, in response to an indication that the target luminaire is offline.

[0153] The neighboring luminaire may comprise a first neighboring luminaire within a set of neighboring luminaires. The set of neighboring luminaires may be defined such that each neighboring luminaire, within the set of neighboring luminaires, is adjacent to the target luminaire.

[0154] The method 1100 further comprises a step 1120 of receiving an additional current illumination value from an additional neighboring luminaire adjacent to the target luminaire, measured by an at least one ambient light sensor of the additional neighboring luminaire. Step 1110 may be substantially the same as step 210 except that it is performed for the additional neighboring luminaire.

[0155] The additional neighboring luminaire may comprise a second neighboring luminaire, different to the first neighboring luminaire, within the set of neighboring luminaires.

[0156] The method 1100 may further comprise additional steps of receiving further additional current illumination values from further additional neighboring luminaires adjacent to the target luminaire, measured by an at least one ambient light sensor of the further additional neighboring luminaires. For example, the method 1100 may comprise as many steps of receiving a respective current illumination value of a respective neighboring luminaire as there are neighboring luminaires within the set of neighboring luminaires. In this way, a current illumination value may be received for each neighboring luminaire adjacent to the target luminaire, where each current illumination value is indicative of the light level in the vicinity of each respective neighboring luminaire.

[0157] The method 1100 further comprises a step 1130 of determining the light status of the target luminaire by comparing each current illumination value (e.g., the current illumination value and the additional current illumination value) with a respective reference illumination value (e.g., a reference illumination value and an additional reference illumination value). The light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

[0158] Each respective illumination value is associated with a respective neighboring luminaire and is compared with the respective current illumination value measured by the respective neighboring luminaire.

[0159] Each respective illumination value may be set according to any previous example, e.g., each respective illumination value may be responsive to a respective previous illumination value measured by the respective neighboring luminaire, etc.

[0160] Step 1130 may comprise determining if each respective current illumination value is higher or lower than each respective reference illumination value. More specifically, step 1130 may comprise determining if the current illumination value is higher or lower than the reference illumination value and if each additional current illumination value is higher or lower than its respective additional reference illumination value.

[0161] Furthermore, step 1130 may comprise controlling the predictive indicator to indicate the target luminaire is not outputting light in response to each current illumination value being below its respective reference illumination value. For example, (if increasing current illumination values indicate increasing light levels) if the current illumination value is determined to be below the reference illumination value, and each additional current illumination value is determined to be below its respective additional reference illumination value, the predictive indicator may indicate that the target luminaire is not outputting light.

[0162] Put another way, if the light level measured in the vicinity of each neighboring luminaire is below an expected value (i.e., the expected value when the target luminaire is ON) the target luminaire can confidently be determined to be OFF.

[0163] In the present example, there may be instances where the light level measured by only some (i.e., not all) of the neighboring luminaires within the set of neighboring luminaires is below an expected value. In other words, some of the neighboring luminaires may determine the target luminaire to be OFF while some of the neighboring luminaires may determine the target luminaire to be ON. In this case, the light status of the target luminaire cannot be known with certainty.

[0164] In the above scenario, it may still be possible to estimate the light status of the target luminaire with a high probability. For example, if the majority (e.g., greater than 75%, greater than 90%, etc.) of neighboring luminaires measure a current illumination value less than a reference illumination value, the target luminaire can be estimated to be OFF.

[0165] The above scenario may occur, for instance, if there is a change in a background light contribution for only some of the neighboring luminaires.

[0166] Alternatively, the above scenario may occur if a luminaire adjacent to one or more of the neighboring luminaires, different to the target luminaire, is not outputting light. In other words, the light level in the vicinity of some of the neighboring luminaires may be lower than expected due to a luminaire different to the target luminaire being OFF. The method 1100 can therefore provide additional contextual information regarding the light statuses of luminaires different to the target luminaire.

[0167] The skilled person is capable of developing a processing system for carrying out any herein described method. Thus, each step of the flow chart may represent a different action performed by a processing system, and may be performed by a respective module of the processing system. The processing system may be embodied by the external device / server.

[0168] Embodiments may therefore make use of a processing system. The processing system can be implemented in numerous ways, with software and / or hardware, to perform the various functions required. A processor is one example of a processing system which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform the required functions. A processing system may however be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.

[0169] Examples of processing system components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0170] In various implementations, a processor or processing system may be associated with one or more storage media such as volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM. The storage media may be encoded with one or more programs that, when executed on one or more processors and / or processing systems, perform the required functions. Various storage media may be fixed within a processor or processing system or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or processing system.

[0171] It will be understood that disclosed methods are preferably computer- implemented methods. As such, there is also proposed the concept of a computer program comprising code means for implementing any described method when said program is run on a computing device. Thus, different portions, lines or blocks of code of a computer program according to an embodiment may be executed by a processing system of the computing device to perform any herein described method.

[0172] There is also proposed a non-transitory storage medium that stores or carries a computer program or computer code that, when executed by a processing system, causes the processing system to carry out any herein described method.

[0173] In some alternative implementations, the functions noted in the block diagram(s) or flow chart(s) may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. 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. If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A computer-implemented method (200) for determining a light status of a target luminaire (110) within a set of luminaires (100), wherein each luminaire in the set of luminaires comprises a light emitting portion (102) and at least one ambient light sensor (104), the computer-implemented method comprising, receiving an indication that the target luminaire (110) is offline, the target luminaire being offline refers to an inability for the target luminaire to transmit information to an external device and / or external server; receiving (220) a current illumination value from a neighboring luminaire adjacent to the target luminaire, measured by the at least one ambient light sensor of the neighboring luminaire; and determining (230) the light status of the target luminaire by comparing the current illumination value to a reference illumination value, wherein the light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

2. The computer-implemented method (200) of claim 1, wherein the current illumination value is measured, by the at least one ambient light sensor (104) of the neighboring luminaire, when the light emitting portion of the neighboring luminaire is outputting light.

3. The computer-implemented method (200) of any of claims 1 or 2, further comprising, in response to the indication that the target luminaire is offline, identifying (240) which of the luminaires, in the set of luminaires (100), is a neighboring luminaire to the target luminaire responsive to location data of each luminaire in the set of luminaires.

4. The computer-implemented method (200) of any of claims 1 to 3, wherein: a task is triggered responsive to the indication that the target luminaire is offline; anda severity of the task is responsive to the determined light status of the target luminaire.

5. The computer-implemented method (200) of any of claims 1 to 4, wherein the step of determining the light status comprises controlling the predictive indicator to indicate that the target luminaire is not outputting light responsive to the current illumination value falling below the reference illumination value.

6. The computer-implemented method (200) of claim 5, wherein the reference illumination value is responsive to a previous illumination value measured by the at least one ambient light sensor (104) of the neighboring luminaire.

7. The computer-implemented method (200) of claim 6, wherein the reference illumination value is further responsive to the difference between a further current illumination value and a further previous illumination value measured by the at least one ambient light sensor (104) of a further luminaire, different to the target luminaire and the neighboring luminaire.

8. The computer-implemented method (200) of any of claims 6 or 7, wherein the current illumination value and the previous illumination value are measured, by the at least one ambient light sensor (104) of the neighboring luminaire, at the same time of day.

9. The computer-implemented method (200) of any of claims 6 to 8, wherein the current illumination value is measured, by the at least one ambient light sensor (104) of the neighboring luminaire, within a predefined time window during the day and / or at a predefined time of day.

10. The computer-implemented method (200) of any of claims 6 to 9, wherein at least the neighboring luminaire further comprises a motion sensor, configured to detect the presence or absence of movement in the vicinity of the neighboring luminaire; and wherein the current illumination value and the previous illumination value are measured, by the at least one ambient light sensor of the neighboring luminaire, when the motion sensor detects the absence of movement in the vicinity of the neighboring luminaire.

11. The computer-implemented method (200) of any of claims 1 to 10, wherein the at least one ambient light sensor comprises a first ambient light sensor, facing a first direction, and a second ambient light sensor facing a second direction opposite to the first direction.

12. The computer-implemented method (200) of any of claims 1 to 11, further comprising, for each of one or more additional neighboring luminaires in the set of luminaires, receiving a respective additional current illumination value measured by the at least one ambient light sensor of the additional neighboring luminaire, wherein: each additional neighboring luminaires is adjacent to the target luminaire; and the step of determining the light status of the target luminaire further comprises, for each one or more additional neighboring luminaires, comparing the respective additional current illumination value to a respective additional reference illumination value for the additional neighboring luminaire, such that each additional current illumination value is associated with a respective additional reference illumination value.

13. The computer-implemented method (200) of claim 12, wherein the step of determining the light status of the target luminaire comprises controlling the predictive indicator to indicate that the target luminaire is not outputting light responsive to the current illumination value falling below the reference illumination value and each additional current illumination value falling below its respective additional reference illumination value.

14. A processing system configured to determining a light status of a target luminaire within a set of luminaires (100), wherein each luminaire in the set of luminaires comprises a light emitting portion (102) and at least one ambient light sensor (104), the processing system being configured to: receiving an indication that the target luminaire (110) is offline, the target luminaire being offline refers to an inability for the target luminaire to transmit information to an external device and / or external server; receive (220) a current illumination value for a neighboring luminaire adjacent to the target luminaire, measured by the at least one ambient light sensor of the neighboring luminaire; compare (420) the current illumination value for the neighboring luminaire to a reference illumination value; anddetermine (421,422) the light status of the target luminaire by comparing the current illumination value to the reference illumination value, wherein the light status comprises at least a predictive indicator of whether or not the target luminaire is outputting light.

15. A computer program product comprising computer program code means which, when executed on a computing device having a processing system according to claim 14, cause the processing system to perform all of the steps of the method according to any of claims 1 to 13.

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