Power Cutoff Message Handling

Abstract

Set of devices adapted to form a local network (3), the set comprising at least one first communication device (1) and multiple second communication devices (2), wherein the first and the second communication devices comprise a short-range communication module (4) to communicate in the local network (3) via a hopping mechanism, and wherein the first communication device additionally comprises a long-distance communication module (5) to communicate with a remote server (6), wherein each one of the second communication devices (2) comprises a memory adapted to store a hopping distance to the first communication device wherein the second communication device is configured to execute actions based on said hopping distance in said power cutoff mode.

Claims

1. A set of devices adapted to form a local network, the set comprising at least one first communication device and multiple second communication devices, wherein the first and the second communication devices comprise a communication module to communicate in the local network via a hopping mechanism, wherein the first communication device additionally comprises a further communication module to communicate with a remote server, wherein each one of the second communication devices comprises a memory adapted to store a hopping distance to the first communication device, and wherein the second communication device is configured to execute actions based on said hopping distance.

2. The set of devices according to claim 1, wherein the second communication devices comprise a power cutoff detection module, wherein each one of the second communication devices comprises an energy storage module, wherein each second communication device is configured to operate in a power cutoff mode, using energy from the energy storage module, when the power cutoff detection module detects a power cutoff, and wherein the second communication device is configured to execute actions based on said hopping distance in said power cutoff mode.

3. The set of devices according to claim 1, wherein said memory is adapted to store, for different hopping distances, corresponding different parameters for said actions.

4. The set of devices according to claim 1, wherein said actions comprise a sequence of: receiving a message from a downstream second communication device for transmission to the first communication device; and transmitting the received message upstream.

5. The set of devices according to claim 4, wherein said actions further comprise receiving a further message from a further downstream second communication device for transmission to the first communication device and merging said message and said further message into a single merged message, and wherein the step of transmitting the received message upstream is comprised by transmitting said single merged message.

6. The set of devices according to claim 4, wherein the step of transmitting is delayed based on said hopping distance.

7. The set of devices according to claim 6, wherein the different parameters comprise at least a delay time for delaying the step of transmitting.

8. The set of devices according to claim 2, wherein said actions further comprise sending a message indicative for the power cutoff.

9. The set of devices according to claim 8, wherein the sending a message indicative for the power cutoff and the transmitting of the received message is combined, and wherein said actions comprise a sequence of: receiving a message from a downstream second communication device for transmission to the first communication device; and transmitting the received message upstream.

10. The set of devices according to claim 1, wherein said first communication device comprises a further power cutoff detection module and a further energy storage module.

11. The set of devices according to claim 1, wherein the local network is an outdoor luminaire network, and wherein at least one of the first and second communication devices serves as communication device for a corresponding luminaire.

12. The set of devices according to claim 1, wherein the communication module is a short-range communication module.

13. The set of devices according to claim 1, wherein the further communication module is a long-distance communication module.

14. A method for operating a communication device in a local network via a hopping mechanism using a communication module, the method comprising: storing a hopping distance to a predetermined other communication device in the local network; and operating the communication device, wherein actions are executed based on the stored hopping distance.

15. The method according to claim 14, further comprising: detecting a power cutoff via a power cutoff detection module, wherein the step of operating comprises operating the communication device in a power cutoff mode, and wherein said actions are executed using energy from an energy storage module.

16. The method according to claim 14, wherein the operating comprises: receiving a message from a downstream communication device for transmission to an upstream communication device; and transmitting the received message upstream.

17. The method according to claim 16, wherein the step of transmitting is delayed based on said hopping distance.

18. The method according to claim 17, wherein the step of transmitting further comprises grouping one or multiple received messages into a single message to be transmitted upstream.

19. A communication device comprising a communication module to communicate in a local network via a hopping mechanism, the communication device further comprising a memory, wherein the memory is adapted to store a hopping distance to a predetermined communication device in the network, and wherein the communication device is configured to execute actions based on said hopping distance.

20. The communication device according to claim 19, further comprising a power cutoff detection module and an energy storage module, wherein the communication device is adapted to operate in a power cutoff mode using energy in the energy storage module when the power cutoff detection module detects a power cutoff, and wherein the power cutoff mode comprises said actions based on said hopping distance.

Description

[0059] The invention will now be described in more details with respect to the drawings illustrating some preferred embodiments of the invention. In the drawings:

[0060] FIG. 1 illustrates a local network according to an embodiment of the invention;

[0061] FIG. 2 illustrates a luminaire according to a first embodiment of the invention;

[0062] FIGS. 3a and 3b illustrate a luminaire according to a second embodiment of the invention;

[0063] FIG. 4 schematically illustrates a local network according to an embodiment of the invention;

[0064] FIG. 5 illustrates how messages are transmitted in the local network according to an embodiment of the invention; and

[0065] FIGS. 6a-6d illustrate several possible scenarios of communication in the network, based on the hopping distance, in case of power cutoff.

[0066] In the drawings a same reference number has been allocated to a same or analogous element.

[0067] The invention particularly relates to the operation of the devices in a local network. First, the local networks and devices used therein will be described in some embodiments with reference to FIGS. 1-4. Secondly, a more general explanation is given in relation to operation of a device in power cutoff mode, including the transmission of a last message. Thirdly, as of FIG. 6, more specific examples of the invention are described including examples showing how the actions can be defined differently based on the hopping distance of a device in the network.

[0068] FIG. 1 shows a first embodiment of the present invention. FIG. 1 shows a first communication device 1 and a second communication device 2. The devices form a local network 3. The first communication device 1 is a device of a first type. The terms ‘first communication device 1’ and ‘device of the first type 1’ are both used in this description to refer to the same device. This device of the first type 1 is characterized by having two communication modules, a short-distance communication module 4 and a long-distance communication module 5. The short-distance communication module 4 is adapted to enable communication between multiple devices in the local network 3 over a predetermined maximum distance. Via the short-distance communication modules 4, the local network 3 is formed. Depending on the type of short-distance communication module 4, the distance is limited to a guaranteed maximum of 2.000 m, preferably a guaranteed maximum of 1.000 m, more preferably a guaranteed maximum of 500 m, most preferably a guaranteed maximum of 100 m. The short-distance communication module is further preferably a low power module. Examples of such short-distance communication modules 4 include ZigBee, WiFi, thread, Bluetooth, wi-sun.

[0069] The long-distance communication module 5 is adapted to enable communication with a remote server 6. In other words, the long-distance communication module 5 enables communication outside the local network 3, preferably with another network such as the internet, most preferably. Depending on the type of long-distance communication module, the distance is minimum 5 km, preferably minimum 10 km, more preferably 20 km Examples of such long-distance communication module include LoRa, cellular (GPRS, 3G/4G/5G), and power line communication networks, which normally have limited bandwidth.

[0070] The second communication device 2 is a device of a second type. The terms ‘second communication device 2’ and ‘device of the second type 2’ are both used in this description to refer to the same device. The device of the second type 2 is characterized by having a short-distance communication module 4. In other words, the device of the second type 2 does not have a long-distance communication module 5. Therefore, this second communication device is unable to directly communicate with a remote server 6. However, when installed in a local network 3, the second communication device 2 can indirectly communicate with the remote server 6 via the first communication device 1. This is further explained hereunder.

[0071] Building a local network 3 with a combination of devices of the first type 1 and devices of the second type 2 has multiple advantages. A first advantage is related to costs. It will be clear to the skilled person that a second communication device 2 is cheaper due to the absence of the long-distance communication module 5 than the first communication device 1. In an alternative embodiment, the hardware of all communication devices is identical or at least substantially the same, to reduce costs in mass production. In such communication devices, the long-distance communication module 5 is disabled or deactivated for the second communication devices 2. Therefore, overall costs can be reduced by using multiple devices of the second type 2 in a local network 3. A local network 3 should comprise at least one device of the first type 1 so that the multiple devices in the local network can communicate to a remote server 6 via this first communication device 1. These multiple devices of the second type communicate via a hopping mechanism.

[0072] A hopping mechanism enables multiple devices to transmit data over long distances by passing data through a network of intermediate devices to reach a more distant one. In other words, the first communication device can be reached in the network by passing data through multiple second devices in the network. Such passing data through is known as hopping. A data package is hopped, which is another word for transmitted, from one communication device to a next communication device such that a communication path is virtually created between a sender device and a receiver device. Sender device and receiver device could be any predetermined device in the local network. In the context of the invention, each second device in the local network 3 is connected to the remote server 6, via a first communication device 1 and via a hopping mechanism within the local network 3. The communication path in the local network 3 may be predetermined or may be dynamically determined. Based on the communication path, the number of hops between each of the second communication devices 2 and the first communication device 1 may be determined. This number of hops is fixed at least when the communication path is predetermined. This number of hops is alternatively varying around an average number when the communication path is dynamically determined. In any case, a hopping distance may be determined based on the fixed or average number of hops. The hopping distance is a measure or an indication of the operational distance between a second communication device 2 and a corresponding first communication device 1 in the local network.

[0073] The local network 3 preferably extends over a predetermined limited area to connect multiple devices in that area. The first and second communication device 1, 2 each comprise at least one of an input and/or output, illustrated with reference number 19. Via the input and/or output, external devices can receive and/or send data from/to the communication device 1, 2. The skilled person will understand that such local network 3 enables such external devices to communicate with each other and/or to communicate with a remote server 6 via the communication devices 1, 2. The local network 3 is typically provided with a mesh or star or tree topology. When the local network has a star topology, the central communication device is preferably of the first type 1.

[0074] Each of the first and second communication device 1, 2 is provided with a power supply 9. Via the power supply 9, the communication device 1, 2 receives the power or energy that is needed to operate the communication device. The electronic circuits in the communication device 1, 2, the short-distance communication module 4 in the devices and, when present/activated, the long-distance communication module 5 is powered via the power supply 9. The power supply 9 is typically connected to the external power supply of the external device that communicates to the input-output 19.

[0075] In the embodiment of FIG. 1, the first communication device 1 comprises a battery 7. The battery is charged when the power supply 9 is connected. When the power supply 9 is disconnected, or the power is cut, which can have multiple reasons or causes, the battery provides energy to the communication modules 4, 5. The battery 7 is dimensioned such that the first communication device 1 can continue its operation during a predetermined period of time after power cutoff is detected. A power cutoff detection module (not shown) is provided, which can be formed as separate circuitry or which can be integrated in the power convertor of the communication device 1. The power cutoff detection module can be arranged as part of the communication device 1 or may be arranged as an external module or may be part of the driver. In the predetermined period of time after power cutoff, the first communication device listens for messages received via the short-distance communication module 4. When the first communication device 1 receives a message, it transmits the message via the long-distance communication module 5 to the remote server 6. It will be clear that the first communication device 1 also sends a message to the server regarding its own status, i.e. when it detects a power cutoff, in the same manner as the second communication device 2.

[0076] The battery is preferably dimensioned such that the predetermined period of time is at least 10 seconds, preferably at least 30 seconds, more preferably at least 60 seconds, most preferably at least 300 seconds. The reason for configuring the first communication device 1 as described above is based on the insight that when power goes down, this typically affects more than one external device and corresponding communication device 1, 2 in the local network 3. Therefore communication device of the second type 2 are sending their last messages to the first communication device 1 for transmission to the remote server 6. By configuring the first communication device such that it can continue its operation for a predetermined period of time, messages from surrounding communication devices of the second type can be captured and transmitted to the remote server. The operating mode of the first device is preferably switched, upon detection of power supply cutoff, from normal operational mode into power cutoff mode. Power cutoff mode is configured to reduce power consumption of the communication device compared to normal operational mode.

[0077] The second communication device 2 comprises a capacitor 8. When power is provided via the power supply 9 to the second communication device 2, the capacitor 8 is charged. When the power supply 9 is disconnected or the power is cut off, the capacitor 8 provides the second communication device 2 with sufficient power to send at least one message. The operating mode of the second device is preferably switched, upon detection of power supply cutoff, from normal operational mode into power cutoff mode. Power cutoff mode is configured to reduce power consumption of the communication device compared to normal operational mode. In an exemplary embodiment, the message sent by the second communication device 2 after detection of the power cutoff is as short as possible, for example the message can be sent in a single telegram, and requires a minimum of computing power. This increases the reliability of the operation of the second communication device 2 after power cutoff. After power cutoff, potential queuing of messages is ignored and the ‘last message’ is sent immediately.

[0078] In the local network 3, hopping is used to transmit messages from a communication device of the second type 2 to a communication device of the first type 1 for transmission to the server 6. In some situations, two or more hops are needed for a message to reach the communication device of the first type 1. In such local networks, the energy storage module 8 in the second communication devices 2 are dimensioned not only to send a last message by the second communication device 2, but also to continue the message transmission functionality for at least a predetermined period of time. Still, the amount of energy stored in the second energy storage module 8 will be significantly smaller than the amount of energy stored in the first energy storage module 7 because the short-distance communication modules 4 consume significantly less energy than the long-distance communication module 5. Therefore, even when the predetermined period of time for continuous operation of the first communication module 1 and the second communication module 2 is identical, still the predetermined amount of energy of the second energy storage module would be significantly smaller than the predetermined amount of energy of the first energy storage module.

[0079] In the embodiment of FIG. 1, the first energy storage module 7 is illustrated as a battery and the second energy storage module 8 is illustrated as a capacitor. The skilled person will understand that these are mere examples and that the type of energy storage module can be selected based on the above described functional requirements by the skilled person. Alternatively, the energy storage modules may be identical or at least substantially the same for the first and second communication devices. The energy storage modules can be selected from batteries, capacitors, series of capacitors, thermo-electric generators, solar panels, and other modules capable of storing and/or generating a limited amount of energy.

[0080] FIG. 2 shows a luminaire device comprising a housing 12. The housing encloses at least one lamp 11 and a corresponding driver 10. Alternatively the driver is outside the luminaire housing, e.g. in the pole. The driver 10 controls the output of the lamp 11. In some embodiments, multiple lamps are provided to be controlled by one or multiple drivers. Sensors can also be added to the luminaire, for example motion sensors, humidity sensors, environmental sensors including pollutant sensors, light sensors, temperature sensors, visibility sensors etc. The sensors can be arranged inside and/or outside the housing 12. An external power supply 9 is typically provided to power the multiple components in the luminaire. In the embodiment of FIG. 2, the external power supply 9 is connected to the driver 10, and the driver 10 distributes the power among the components in the luminaire. Optionally, the driver 10 is physically and/or functionally segmented such that several drivers may be present.

[0081] The housing 12 of the luminaire is provided with a socket 13. This socket can be formed as by any known type of socket. Such socket may provide a mechanism to provide the controller with a 24V DC signal, as shown in FIG. 3a which shows a Zhaga socket. Alternatively, the socket may be connected to the main power supply and be provided to distribute the power to other devices, as shown in FIG. 3b. Such socket may be formed as a socket fulfilling the requirements of the ANSI C136.41-2013 standard or the ANSI C136.10-2017 standard. Such socket is provided to receive the 230V AC power signal, and to provide power to the driver of the luminaire.

[0082] A controller 14 is connected to the luminaire, preferably to the socket 13. The controller 14 preferably comprises a communication device 1, 2. In the embodiment of FIG. 2 the controller 14 comprises a first communication device 1 having both a short-distance and a long-distance communication module 4, 5.

[0083] The first energy storage module 7 is provided inside the housing 12 of the luminaire. As described above, this facilitates maintenance. When the first energy storage module 7 is formed as a battery, it could be necessary to replace the battery periodically, for example once every five years. This is particularly beneficial when the lifetime of the controller 14 is expected to be higher than the lifetime of the energy storage module. In the embodiment of FIG. 2, a connection 15 is illustrated between the driver 10 and the controller 14. Via this connection 15, power is transmitted and communication messages are exchanged between the driver 10 and the controller 14. Via an additional connection, the energy storage module 7 is connected to the controller 14.

[0084] The power cutoff detection module (not shown) may be provided in the controller 14, or may be arranged in the housing 12 of the luminaire as a dedicated module. Further alternative, the power cutoff detection module may be arranged in the driver 10 or in the socket 13. Preferably the power cutoff detection module is provided as part of the controller 14. This makes the controller 14 independent from the device it is connected to. It may be connected to any driver or any external device.

[0085] The skilled person will understand that the embodiment of FIG. 2 is a mere example, and that multiple modifications can be made without affecting the overall operation of the luminaire. For example, the connection 15 could be split in a power connection and a data connection so that the socket 13 would have three pairs of connectors. The transmission of energy and/or signals through the socket 13 can be formed physically, being a wired connection, or optical or electromagnetic, for example via coils. Instead of setting up a direct communication between the driver 10 and the controller 14 electronics can be provided in the housing 12 of the luminaire as an intermediate element, to which for example also one or more of the described sensors can be connected.

[0086] In luminaire networks, there has been a history of switching off the lights by simply switching off the main power 9. Recent developments have added additional functionalities and possibilities to control the luminaires Even with advanced control mechanisms it remains common practice to switch off the lights in the morning by switching off the power 9. Because the energy storage module 7 is provided in the luminaire 12 to provide energy to the communication device 1 in the controller 14, the communication device is able to update its status in the remote server 6 before being switched off. The controller 14 preferably comprises a mechanism to measure the external power 9 such that it can detect a cutoff of the external power supply 9. Upon detection of the power cutoff, the controller 14 is configured to send a status update to the remote server via the first communication device 1. This allows the remote server to show the most recent events, also when this most recent event is a power cutoff. This makes the information in the remote server more reliable.

[0087] FIG. 3a shows an alternative embodiment of a luminaire. The luminaire comprises a housing 12 enclosing a lamp 11 and a corresponding driver 10. The luminaire also comprises a socket 13 for mounting a controller 14. In the embodiment of FIG. 3a, the controller 14 is provided with a second communication device 2. In the embodiment of FIG. 3a, the energy storage module 8 is provided inside the controller 14. Therefore, in this embodiment, the energy storage module 8 is located outside the housing 12 of the luminaire. In this embodiment the energy storage module 8 can only be replaced together with the controller 14. This is a beneficial situation when the lifetime of the energy storage module is expected to be about the same as the lifetime of the controller 14. In the embodiment of FIG. 3a, a communication connection 16 is provided between the controller 14 and the driver 10, and a power connection 17 is provided between the controller 14 and the driver 10. The operation and advantages of the embodiment of FIG. 3a are analogue to the operation and advantages described in relation to FIG. 1 and FIG. 2. The skilled person will understand, on the basis of the description above, how the luminaire 12 can send a status update after power cutoff. In FIG. 3a, the controller typically receives a 24V DC signal from the driver. Control circuitry is provided in the controller 14 to detect power supply cutoff.

[0088] FIG. 3b is comparable to FIG. 3a, but in the embodiment of FIG. 3b the main power supply is connected to the controller 14, via the socket 13. The power supply cutoff module in FIG. 3b can be formed by zero-crossing detectors. When a predetermined number of zero-crossings is missing, power supply cutoff is detected. In FIG. 3b, connection 15 is illustrated between the driver 10 and the controller 14. Via this connection 15, power is transmitted from the controller 14 to the driver 10 and communication messages are exchanged between the driver 10 and the controller 14.

[0089] FIG. 4 shows a schematic illustration of a local network 3 built with a combination of communication devices of the first type 1 and communication devices of the second type 2. The ratio of the number of communication devices of the second type 2 to the number of communication device of the first type 1 is preferably at least 2:1, more preferably at least 3:1, more preferably at least 5:1 and can go up to 10:1, 20:1, 50:1, 100:1 and more. The devices of the second type 2 can communicate to the server 6 via the communication devices of the first type 1.

[0090] In FIG. 4 a zone 18 is marked, which is a part of the local network 3. When the power goes down in this zone 18, communication devices 1 and 2 within this zone 18 can send a status update to the remote server 6, using the above described mechanism. Particularly, in the context of outdoor lighting networks, this is a significant advantage. A local loss of power can have multiple reasons, for example cable theft, cable break, lightning strike, tripped master circuit breaker or other cable malfunctioning. Independent from the reason, it is a benefit that the loss of power is communicated to the remote server 6. The remote server 6 is preferably programmed to generate a warning signal when unexpected loss of power messages are received. The skilled person will understand that when power is switched off in the morning, and loss of power messages are received from all or nearly all devices in the local network 3, these messages do not qualify as unexpected loss of power messages. However, when during the night, a segment of the local network 3 looses power, the correspondingly received messages can be considered as unexpected. These unexpected messages can trigger an alarm to an operator, which operator can decide whether and how to take action. This allows an operator to restore the power supply as soon as possible, thereby increasing the operation and safety of the luminaire network.

[0091] Mechanisms can be provided to detect the origin of the power failure by mapping the loss of power messages onto a power grid map. In most situations this reduces the physical area wherein the problem causing the power cutoff can be reasonably expected. This reduces local network maintenance costs and decreases the time needed to detect the problem. The last message may contain other information than just power cutoff information. This other information might provide an operator with an indication on the reason of the power cutoff.

[0092] FIG. 5 illustrates how messages are transmitted in the local network. FIG. 5 shows one first communication device 1 and three second communication devices 2a, 2b, 2c. FIG. 5 furthermore shows the remote server 6. The upper part of FIG. 5 shows normal operation of the local network. In normal operation, the server can send messages, for example instruction messages, to the communication devices. Different examples of such messages are illustrated by arrows 100-104. Arrow 100 illustrates an instruction message from the server 6 to the first communication device 1. Message 102 is an instruction message for a second communication device 2a. Since the server cannot directly reach the second communication device 2a it sends the message to the first communication device, see arrow 101, which transmits the message to the second communication device 2a, see arrow 102. In another embodiment, the server 6 can send more general messages, which are received by the first communication device, see arrow 103, and which is further distributed in the local network to all second communication devices 2a, 2b, 2c, see arrow 104.

[0093] In normal operation mode, communication devices 1 and 2 are typically provided with a mechanism to send messages to the remote server 6. These messages typically comprises status update information. These messages are shown in FIG. 5 by arrows 105-111. Arrow 105 illustrates a message from the first communication device 1 to the remote server 6. Arrows 106, 108 and 110 illustrate messages from the second communication device 2a, 2b, 2c, respectively, to the remote server 6. However, since the second communication devices 2a, 2b, 2c cannot directly reach the remote server 6, these messages 106, 108, 110 are transmitted to the first communication device 1, that transmits messages to the remote server 6 as is illustrated by arrows 107, 109 and 111.

[0094] The skilled person will understand that mechanisms can be provided to optimize the flow of data and messages through the local network, for example by combining multiple messages from second communication devices into a single message to the remote server. The skilled person will also understand that not all devices 1 and 2 in the local network must be able to bi-directionally communicate. Some devices might only be provided to receive instructions, other devices might only be provided to send data. The invention is applicable in such cases.

[0095] In FIG. 5, dotted line 112 illustrates a power cutoff. Without energy storage modules, the communication devices 1 and 2 would not be able to communicate after the power cutoff 112. However, since these devices are provided with energy storage modules, as is explained above, communication devices 1 and 2 are able to notify the power cutoff to the remote server 6. To this end, each of the second communication devices 2a, 2b, 2c send a last message via the first communication device 1 to the server 6. The first communication device 1 receives the messages 113, 115, 117 from the second communication devices 2a, 2b, 2c and transmits these messages to the server 6 as is illustrated by arrows 114, 116, 118. Typically, the first communication device 1 also sends a power cutoff message 119, or a last message 119 to the server 6 to update its status. The first communication device 1 is provided to operate for a predetermined time 120 after power cutoff 112. The second communication devices 2a, 2b, 2c typically stop working a short time after sending their last message. This is illustrated by sign 122 and 122a, 123 and 123a, 124 and 124a, respectively showing the time period wherein the device continues operation after power cutoff 112 and the point in time where it stops.

[0096] The first communication device 1 continues its operation typically for a longer period, and stops working as is illustrated in FIG. 5 with sign 121. The skilled person will understand that the messages shown in FIG. 5 could in practice be sent in a different succession. The last messages 113, 115, 117 and 119 typically comprise a status update for the remote server 6. This status update comprises at least information indicating that the power is down. Further, preferably, the last message comprises the latest measured sensor information and/or latest device status information. By receiving these messages at the server 6, an operator 126 checking the status of the luminaires via the server, illustrated by arrow 125, will see the most recent status of the devices, even after power cutoff. Therefore, the information provided by the server 6 to the operator 126 is reliable.

[0097] The operation of the second communication devices is based on the hopping distance, which is described above. FIG. 6a illustrates a drawback when all communication devices operate in the same way in the network, thus not based on the hopping distance. FIG. 6a illustrates a communication path between a second communication device 2F and the remote server 6. The second communication device 2F communicates to the server 6 via the first communication device 1 and further via the second communication device 2D and the second communication device 2E. The hopping distance between the second communication device 2F and the first communication device 1 is two, namely a data package is transmitted two times being by the device 2E and the device 2D before it reaches the first communication device 1. In an analogue way, FIG. 6a illustrates the communication path between the second communication device 2E and the first communication device 1. The hopping distance for device 2E is 1. In an analogue way, FIG. 6a illustrates the communication path between the second communication device 2D and the first communication device 1. The hopping distance for device 2E to the first communication device 1 is 0 because there is a direct communication between the device 2E and the first communication device 1. The first communication device 1 re-transmits all messages to the server 6. The first communication device 1 may group multiple message for re-transmission to the server 6, or may re-transmit the messages individually.

[0098] FIG. 6a illustrates the communication messages that can reasonably be expected between second communication device 2F and the remote server 6 in case of a power cutoff when actions of the devices are not based on a hopping distance. Second communication device 2F will transmit a ‘last message’. To distinguish between ‘last messages’ of different devices, this last message will be ‘last message 2F’. Second communication device 2E also transmits a ‘last message’ being ‘last message 2E’. However, second communication device 2E also receives ‘last message 2F’ for transmission. Therefore second communication device 2E sends two messages. Second communication device 2D will also transmit a ‘last message’ being ‘last message 2D’. Analogue to second communication device 2E, second communication device 2D receives ‘last message 2E’ and ‘last message 2F’, which are both transmitted such that second communication device 2D sends three messages. First communication device 1 receives all messages for transmission to the server 6, and transmits its own ‘last message’. This makes clear that even in a short segment of a hopping network, a multitude of messages is generated and transmitted in case of a power cutoff. In the specific example of FIG. 6a, 10 messages or data packets are transmitted and re-transmitted substantially at the same time or at least in a short period of time.

[0099] FIG. 6b illustrates a communication path between a second communication device 2F and the remote server 6 which is the same as FIG. 6a. In FIG. 6b, the operation of the second communication devices is based on the hopping distance. This allows to control actions executed in the second communication devices based on the hopping distance. In the example of FIG. 6b, the second communication devices with an uneven hopping distance, being the device 2E, as well as the first communication device 1, are configured to listen for a predetermined time for received messages and, in a further step, configured to combine the messages received during listening with their own last message. As a result, second communication device 2E receives a ‘last message 2F’ and combines its own ‘last message 2E’ with the received ‘last message 2F’ into a single message which is transmitted to second communication device 2D. Second communication device 2D sends its ‘last message 2D’ to the first communication device 1. Furthermore, its transmits the combined ‘last message 2E and 2F’ to the first communication device 1 such that the second communication device 2D sends two messages to the first communication device 1. The first communication device 1 receives the ‘last message 2D’ from the second communication device 2D. The first communication device 1 combines this ‘last message 2D’ with its own last message into a combined single message to the server 6. Furthermore, its transmits the combined ‘last message 2E and 2F’ received from the second communication device 2D to the server 6 such that the first communication device 1 sends two messages to the server 6. In comparison with FIG. 6a, it is evident that significantly less messages are transmitted. Alternatively, the first communication device 1 combines messages 2D+2E+2F in a first message to the server 6, and transmits its own message separately.

[0100] FIGS. 6c and 6d show further embodiments illustrating how the operation of the communication devices may be based on the hopping distance. Both FIGS. 6c and 6d show six second communication devices 2G-2L, and a single first communication device 1. The skilled person recognizes from the figure, in analogy to the explanation given above with respect to FIGS. 6a and 6b, that the hopping distance increases from zero for communication device 2G to five for communication device 2L.

[0101] In FIG. 6c, the sending and transmitting of messages is based on the hopping distance by providing different transmission slots to different communication devices. Particularly, communication is allowed or enabled alternately between second communication devices with an even hopping distance and with an uneven hopping distance. The consecutive timeslots are illustrated in FIGS. 6c and 6d with consecutive reference numbers 20-26. FIG. 6d differs from FIG. 6c in that the consecutive timeslots are differently assigned to the communication devices. In particular, the second communication devices 2G-2L are divided in trios and different communication devices in the trio are assigned to different timeslots. Based on the illustration in FIGS. 6c and 6d, the skilled person realizes that an optimal balance may be obtained between on the one hand the number of messages transmitted when a power cutoff situation occurs and on the other hand the size of the messages transmitted. Multiple solutions may be proposed wherein the sending and transmitting of messages is based on the hopping distance.

[0102] FIG. 6 shows only a single communication path. Hopping mechanisms typically comprise a three structure such that the effect in practice is significantly larger. It is also noted that listening for messages consumes considerably less energy than transmitting messages. Therefore, from energy management point of view, it is advantageous to configure at least some devices in the network, depending on the hopping distance, to listen for messages.

[0103] Further mechanisms can be provided to optimize the operation of the network. For example, while listening for messages, messages received are stored in a buffer at the respective communication device. Furthermore, a selection can be made by the receiving communication device to only store those messages which are intended to be transmitted by the communication device. This avoids unnecessary storage of data. In the communication device, the buffer usage can be monitored and, when the buffer usage is above a predetermined threshold, a combined message is transmitted even when the listening period has not been completed or finished. This avoids that messages become too big. This also avoids that messages are dropped because of lack of buffer space.

[0104] The actions to be executed by the communication devices in power cutoff mode may be made dependent on the hopping distance in many different ways. Above, a first embodiment is described wherein the listening time of the second communication devices 2 with an even hopping distance is different from the listening time of the second communication devices 2 with an uneven hopping distance. In another embodiment, the listening time of the second communication devices can be made inversely proportional to the hopping distance. The inversely proportional listening may be implemented in a static or dynamic manner. When the action of listening is implemented in all devices in the same way, wherein the listening time is encoded as a formula or algorithm wherein the hopping distance is a factor, the listening action is dynamically made proportional to the hopping distance. Alternatively, the remote server could, when installing the network, provide instructions to the communication device to listen for a predetermined period of time. This predetermined period of time may be chosen by the remote server based on knowledge of the local network, including knowledge of the hopping distance of the particular communication device. The latter would be a static implementation.

[0105] Other actions may be implemented based on the hopping distance or actions may be differently executed based on the hopping distance. For example, sequence of actions may be different based on the hopping distance while the actions itself remain identical.

[0106] Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.

LIST OF REFERENCES

[0107] 1. first communication device [0108] 2. second communication device [0109] 3. local network [0110] 4. short-distance communication module [0111] 5. long-distance communication module [0112] 6. remote server communication module [0113] 7. first energy storage module [0114] 8. second energy storage module [0115] 9. external power supply [0116] 10. driver [0117] 11. lamp [0118] 12. housing [0119] 13. socket [0120] 14. controller [0121] 15. power+communication [0122] 16. communication [0123] 17. power [0124] 18. zone [0125] 19. input-output [0126] 20-26. consecutive timeslots [0127] 100-104. instructions [0128] 105-111. status update [0129] 112: power cutoff [0130] 113-119: last message [0131] 120: period of time [0132] 121-124: shutoff [0133] 125: status request [0134] 126: operator