Automatic power-on restart system for wireless network equipment

Abstract

The present invention relates to an apparatus and method for automatically detecting whether a wirelessly connected network device having a non-network role is powered on / power cycled in a normal manner (such as using a conventional (wall) switch) or powered on / power cycled after a power failure recovery. Based on the result of the detection, the expected behavior of the end user is selected so that the connected network device can behave accordingly.

Description

Technical Field

[0001] The present invention relates to the field of power-on restart systems for wireless network devices, such as but not limited to wirelessly connected lighting devices in a ZigBee network for use in a variety of different applications in home, office, retail, hospitality and industry. Background Art

[0002] Using wireless networks with smart network devices (e.g., lighting devices such as smart light bulbs) makes it possible to automatically adjust the non-network functions of the device (e.g., lighting, sensing, etc.) based on other devices that are turned on, remotely control non-network functions, link the settings of non-network functions to motion detection, etc.

[0003] Such wireless networks of smart network devices can be built on the ZigBee protocol. ZigBee itself is built on a low-power radio network called IEEE 802.15.4.

[0004] US Pat. No. 9,883,570 B1 discloses a protocol for lighting control via a wireless network, wherein a monitor lighting control device receives a state change event message, the event message including a payload specifying: (i) a state change event of an occupancy, audio, or daylight sensor, or a switch to turn lighting on / off, dim / lower, set a scene, etc.; (ii) an identifier of a member lighting control device that detected the state change event; and (iii) a lighting control group identifier of a lighting control group including a member lighting control device and a monitor lighting control device. The monitor lighting control device transmits a receipt confirmation of the state change event message to the member lighting control device.

[0005] ZigBee devices offer reduced power consumption and cost, as well as mesh networking capabilities, which makes them suitable for use in large-scale deployments. Application examples of ZigBee mesh networks include home automation, building automation, retail services, smart energy, and wireless indoor lighting systems.

[0006] However, problems have been faced when network devices are used in areas with unstable power grids and they lose power very frequently, causing the network devices to return to an undesirable default state. This is highly problematic for markets such as India, as power outages occur almost daily. However, even in markets such as the United States or Australia, this leads to problems such as (in some areas) frequent power failures.

[0007] In the case of home lighting networks, most complaints come from customers who are woken up in the middle of the night because power to the light fixtures is lost and restored. This causes the lights to turn on at full brightness, waking up the person sleeping in that room. Customers also complain that their light bulbs have been on for long periods of time when they are not home due to power failures.

[0008] However, it is a conscious choice to have the network devices start up in a predetermined default state (e.g. 2700K @ full brightness). The reason may be that network devices are typically not powered directly from the mains, but rather via a "traditional" wall switch. By always starting up in the desired default state, the conventional wall switch can still be used to cause the network devices to produce functional outputs (e.g. functional light levels). If the network devices would always go to the previous setting (which might be off, or at a very low brightness, or at a saturated color in the case of color-capable lighting devices), it would be necessary to use, for example, an additional application or remote control to cause the network devices to produce the desired functional output after being manually turned on by the wall switch. Summary of the invention

[0009] The object of the present invention is to provide an adaptive restart process for a network device in a wireless network.

[0010] This object is achieved by an apparatus according to the present disclosure, a network device according to the present disclosure, a method according to the present disclosure, and a computer program product according to the present disclosure.

[0011] According to a first aspect, there is provided an apparatus for controlling a restart mode of a network node in a wireless network, wherein the apparatus comprises:

[0012] A power-on detector, used to detect a power-on event of a network node;

[0013] a message detector for detecting receipt of a wireless power-up message from another network node of the wireless network; and

[0014] The control unit is adapted to select one of a plurality of restart modes depending on the output of the message detector in response to detection of a power-on event by the power-on detector.

[0015] According to a second aspect, a network device comprising the apparatus of the first aspect and a non-network function is provided.

[0016] According to a third aspect, there is provided a method for controlling a restart mode of a network node in a wireless network, wherein the method comprises:

[0017] Detecting power-on events of network nodes;

[0018] detecting receipt of a wireless power up message from another network node of the wireless network; and

[0019] In response to a detected power-on event, one of a plurality of restart modes is selected depending on the received power-on message.

[0020] Finally, according to a fourth aspect, a computer program product is provided, comprising code means for producing the steps of the above method according to the third aspect when run on a computer device.

[0021] Thus, it can be determined at the network node whether the network node has experienced a power cycle caused by a power outage and / or whether it is the result of a regular power cycle, and an appropriate course of action (e.g., restart mode) can be selected accordingly. To achieve this, the network devices transmit power-up messages when powered on, and the relevant network devices check whether there are enough of these messages, in which case it is likely that there was a power outage. Based on the results of the detection, the expected behavior of the end user can be selected so that the connected network devices can behave accordingly.

[0022] According to a first option, the plurality of restart modes may include at least a safe mode that ensures proper operation of the non-network functions of the factory-configured network node and a power failure mode that restores a previous state of the non-network functions prior to a power-on event. This ensures that the restart mode automatically selected by the network device appropriately matches the user's expectations.

[0023] According to a second option which can be combined with the first option, the network device can be a luminaire device and the non-network function can be a lighting function. Thus, the luminaire devices of the lighting network can be configured to restore appropriate and expected lighting behavior depending on the cause of the power failure.

[0024] According to a third option, which may be combined with the first or second option, the control unit may be adapted to initiate the transmission of at least one power-on message to the wireless network in response to the detection of a power-on event by the power-on detector. This measure ensures that other network devices are informed of the power-on event and can determine whether a concurrent power-on event at their location was the result of a user's intended switch-on or an unintentional power failure.

[0025] According to a fourth option, which may be combined with any of the first to third options, the control unit may be adapted to select the power failure mode if the output of the message detector indicates that a predetermined number of power-up messages have been received within a predetermined time period. The predetermined number may be selected based on a local environment of the network device to ensure that a reliable distinction can be made between an intended shutdown and an unintentional power failure.

[0026] According to a fifth option which may be combined with any one of the first to fourth options, when the power failure mode is selected, the control unit may be adapted to restore a previous state of the non-network functions of the network device before the power-on event. This measure ensures that in the event of a power-on event following an unintentional power failure, the expected state of the non-network functions of the network device is restored.

[0027] According to a sixth option which may be combined with any one of the first to fifth options, the power-on message may be selected from a ZigBee link status message sent to all previously known neighbor devices, a ZigBee device advertisement message, a ZigBee inter-PAN broadcast or unicast message, a ZigBee broadcast message, a ZigBee multicast message, a ZigBee unicast message, and an original 802.15.4 message. Thus, based on the available message types, the proposed solution may be easily implemented in a ZigBee network.

[0028] According to a seventh option, which can be combined with any of the first to sixth options, the message detector can be adapted to distinguish between different sending network nodes by a source address or other identifier included in the power-on message. Thus, reliability can be increased because only such power-on messages received from different other network nodes are considered.

[0029] According to an eighth option which can be combined with any one of the first to seventh options, the message detector can be adapted to ignore at least one of power-on messages having a signal quality or strength above a predetermined threshold, a transmitter identifier indicating that the network device is located between the same light switches as the network node, and an identifier indicating the same light switch group as the network node. Thus, reliability can be further increased because only such power-on messages that may be received from other network nodes that are not connected to the same light switch are considered.

[0030] According to a ninth option, which can be combined with any of the first to eighth options, the control unit can be adapted to ignore a power-on message received from another network node based on a previous behavior of the other network node compared to the network node. Thus, reliability can be further increased, since only such power-on messages that may be received from other network nodes that are not connected to the same light switch are considered.

[0031] According to the tenth option which can be combined with any one of the first to ninth options, the power-on message may include information about the type or role of the device that has transmitted the power-on message (e.g., a lamp device, a sensor device, a bridge device, etc.). Therefore, reliability can be further increased because only such power-on messages that may be the result of the same cause of the power outage are considered.

[0032] According to an eleventh option, which may be combined with any of the first to tenth options, the message detector may be adapted to detect a power failure report received by the network device. Thus, reliability may be further increased as other relevant types of messages indicating a power outage are taken into account.

[0033] Note that the above apparatus may be implemented based on discrete hardware circuits having discrete hardware components, an integrated chip or a chip module arrangement, or based on a signal processing device or chip controlled by a software routine or program stored in a memory, written on a computer-readable medium or downloaded from a network (such as the Internet).

[0034] It should be understood that the apparatus according to the present disclosure, the network device according to the present disclosure, the method according to the present disclosure, and the computer program product according to the present disclosure may have similar and / or identical preferred embodiments.

[0035] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following figures:

[0037] Figure 1 Schematically illustrates a schematic system architecture of a wireless lighting network;

[0038] Figure 2 schematically shows a block diagram of a lighting device according to various embodiments; and

[0039] Figure 3 A flow chart of an automatic power-on restart process according to various embodiments is shown. DETAILED DESCRIPTION

[0040] Embodiments of the present invention are now described based on a wireless lighting network as an example of a wireless network and a lamp device as an example of a wireless control network device.

[0041] Typically, energy is generated and delivered to a home. In a home, there is a main fuse box, and electrical devices may be connected directly to the home grid, but often, especially light bulbs, they are wired behind a mains (light) switch. This light switch is usually located near the entrance to a room to make it easy for people walking in or out of the room to turn the light on and off.

[0042] Figure 1Schematically illustrated is the architecture of a multi-hop lighting network in which various embodiments may be implemented. The network includes at least one luminaire device 20, 30 (e.g., a smart lamp, such as a light emitting diode (LED)-based lamp, a gas discharge lamp, or a filament bulb, plus any associated support, housing, or other such casing) arranged to emit illumination into an environment. The environment may be an indoor space, such as one or more rooms and / or corridors of a building; or an outdoor space, such as a park, garden, road, or outdoor parking area; or a partially covered space, such as a stadium, a structured parking facility, or a terrace; or any other space, such as the interior of a ship, train, or other vehicle; or any combination of such possibilities. The luminaire devices 20, 30 may take any suitable form, such as a ceiling or wall mounted luminaire, a freestanding luminaire, a wall washer, a pendant; or a less conventional form, such as recessed lighting built into an item of furniture, a building material (such as glass or concrete), or any other surface.

[0043] The luminaire devices 20, 30 are equipped with wireless communication interfaces allowing them to transmit and receive wireless messages for remote control and / or signaling purposes.

[0044] The first lamp device 30 is wired directly to the mains power supply 100, while the second lamp device 20 is wired to the mains power supply 100 via the light switch 10. This allows the second lamp device 20 to be conveniently turned off, although doing so renders the wirelessly controllable second lamp device 20 uncontrollable from the lighting system. When the light switch 10 is turned back on, the second lamp device 20 is powered again. At this point, the control unit (e.g., software) in the wirelessly controllable second lamp device 20 needs to decide what to do: assume that the user has flipped the light switch 10 and therefore requires a functional light, or revert to the settings that the wirelessly controllable second lamp device had before the power was cut off. However, this may be a low dimming level, a saturated color, or even an off state (standby). This is typically not what the user intended when flipping the light switch 10.

[0045] However, in other cases of power outages—for example, a malfunction in the home's main fuse box, or a general blackout due to a problem with power plant generation or home transportation—the expected behavior may be different. In such cases, it would be more useful to the user if the wirelessly controllable lighting devices 20 would enter the last state they had before the power outage.

[0046] According to various embodiments, a restart control function, which may be referred to as "user defined start," may be introduced that lets the user select what should happen after a power failure.

[0047] As an example, the user may choose between the following (per light, or perhaps per room or home in aggregate):

[0048] 1. Safety Mode: Factory defined mode, for example, full strength on.

[0049] 2. Power failure mode: For example, restoring the previous state before the power failure (which may be a OFF state).

[0050] 3. Custom Mode: For example, the user can select the color and / or dimming level that the light fixture will show after power-up.

[0051] Power Failure Mode is primarily intended for markets like India where the grid is less stable. But again, many users in the US and EU have complained that “the light doesn’t remember its last state”.

[0052] However, the problem with the power failure mode is that the user can no longer use the conventional wall switch 10 to switch the light from the standby state to the on state.

[0053] However, this problem can be overcome by enabling wirelessly controllable lighting devices to determine with a high level of accuracy whether their power is due to a mains power failure or to a user flipping the light switch 10 .

[0054] According to various embodiments, this can be achieved by having the wirelessly controllable lighting device transmit a wireless power-on message when powered on. The wirelessly controllable lighting device can then also listen for the power-on message within a predetermined amount of time after powering on.

[0055] If a wirelessly controllable lighting device receives such a power-on message (not transmitted by itself) within a predefined time after power-on, it knows that other wirelessly controllable lighting devices also powered up at the same time, and it assumes that this was because of a mains power failure. The wirelessly controllable lighting device can then, for example, return to the previous state it was in.

[0056] Otherwise, if the wirelessly controllable lighting device does not receive such a power-on message within the predefined time after power-on, it is the only wirelessly controllable lighting device powered on at the time, and it assumes that this was due to a conventional power switch toggle by the user. The wirelessly controllable lighting device may then, for example, switch to a default full brightness (e.g., a default brightness of, for example, 2700K).

[0057] Figure 2 Schematically shows a block diagram of a wireless controllable network device according to various embodiments. Note that Figure 2 Only those blocks related to the proposed automatic restart function are shown in FIG. Other blocks have been omitted for the sake of brevity.

[0058] Figure 2 The network device can be Figure 1 One of the wirelessly controllable second lighting devices 20 in the system, or any other type of wirelessly controllable network device having non-network functions (e.g., light generation, sensing, control, recording, etc.).

[0059] according to Figure 2 , the network device includes a transceiver unit (TRX) 28 for transmitting and receiving wireless messages and / or other wireless signals via an antenna. The power-on message to be transmitted for automatic restart control is generated by a power-on control unit (PUCU) 21 and supplied to the transceiver unit 28 for wireless transmission over the network. In addition, messages received by the transceiver 28 from other network devices are forwarded to a power-on message detector (PUMD) 26, which is configured to determine the power-on message (e.g., a "just started" message) based on a predetermined characteristic (e.g., an identification pattern or flag).

[0060] Additionally, the network device includes a power up detector (PUD) 22 that detects power up after the network device loses power (eg, a user power down or due to a power failure).

[0061] Note that both the power-on message detector 26 and the power-on detector 22 may be integrated in the power-on control unit 21, for example as dedicated subroutines of a power-on control program.

[0062] Based on the information obtained from the power-on detector 22 and the power-on message detector 26 or the corresponding subroutine, the power-on control unit 21 controls the power-on mode setting unit (PUMS) 24 to set a predetermined power-on mode according to the power loss condition determined by the information obtained from the power-on detector 22 and the power-on message detector or the corresponding subroutine.

[0063] Therefore, an adaptive restart mode after power-up may be automatically selected based on the power loss situation.

[0064] Figure 3 FIG. 1 shows a flow chart of an automatic power-on restart process according to various embodiments, which may be performed, for example, in Figure 2 The power-on control unit 21 is implemented.

[0065] In step S300, in response to detecting a power-on condition, the process begins. Then, in step S301, a radio unit (e.g., Figure 2 The transceiver 28) can allow wireless messages to be transmitted and received to / from the network.

[0066] Then, the process branches into a transmission-related branch (steps S302 to S306) and a reception-related branch (steps S307 to S312), which can be processed simultaneously or alternately.

[0067] In step S302, the transmit counter is set to zero and the process proceeds to step S303 where a first power-up message (e.g., "Just Started") is broadcast over the network. Then, in step S304, the transmit counter is incremented by one and a predetermined or random delay period is introduced in step S305. Thereafter, in step S306, the process checks whether the value of the transmit counter is below a preset or random number of transmits. If so, the process jumps back to step S303 and a second power-up message is broadcast, followed by incrementing the transmit counter in step S304 and incrementing the delay period in step S305. This loop of steps S303 to S306 continues until the process determines in step S306 that the value of the transmit counter has reached a preset or random number of transmits.

[0068] If the current transmit number of power-up messages has been broadcast, the transmit-related branch of the process ends.

[0069] Additionally, in the first step S307 of the reception-related branch, the process checks whether a power-on message (e.g., "just started") has been received from another network device. If so, the process continues to step S308 and the reception counter is incremented by one. Otherwise, if no power-on message has been received from another network device, the process jumps to step S309 and checks whether a predetermined start-up time has been reached. If not, the process jumps back to step S307 and checks again whether a power-on message has been received in the meantime, and in the affirmative case increments the reception counter.

[0070] In addition, if the receive counter is not zero, the process also checks whether a receive message has been received from a new network device, and only increments the receive counter if a power-on message has been received from another network device that has not yet registered to just start up. Thus, it can be ensured that only power-on messages received from different network nodes are counted.

[0071] The loop S307 to S309 continues until a predetermined start-up time period is reached. The process then continues to step S310 and checks whether the reception counter has reached a preset threshold number of power-up messages. If so, the process assumes that a power failure has occurred and branches to step S312, where a power failure start-up mode or behavior is applied. Otherwise, if a preset number of messages has not been reached within the start-up period, the process assumes that the power has been turned off by the user and branches to step S311, where a conventional switch start-up mode or behavior is applied.

[0072] Note that the delay period of step S305, the preset number of step S306, the predetermined start time of step S309, and / or the preset threshold number of step S310 may also be calculated based on at least one external factor (e.g., interference level, received signal quality, total number of network devices, or other suitable factors).

[0073] therefore, Figure 3 The process ensures that the network device sends a preset number of power-on messages at each power-on event, and the startup mode or behavior applied by the network device depends on the number of power-on messages received from other network devices.

[0074] The wireless power-on message (eg, "Just Starting") may be a new wireless message created for this purpose, or an existing wireless message of the network system that is reused (eg, an empty link state message or a device advertisement message sent by a ZigBee device at startup).

[0075] As another option, the wireless power-on message (e.g., "Just Started") can be a raw 802.15.4 message or a ZigBee inter-PAN (personal area network) broadcast message. Although it is an inter-PAN message, its scope can still be limited to the current PAN by setting the destination PAN identification (ID) to the PAN ID of the current network, rather than the more typical setting it to "0xFFFF" (meaning all PANs). Therefore, the inter-PAN message does not leave the PAN.

[0076] ZigBee inter-PAN messages are not retransmitted by other nodes, whereas networking messages are retransmitted by nodes in the same network (eg, PAN).

[0077] Other options for the power-on message are ZigBee inter-PAN unicast message (which is sent to all previously known neighbors), ZigBee broadcast message, ZigBee multicast message, ZigBee unicast message (which is sent to all previously known neighbors). The wireless power-on message (e.g., "Just Started") can be transmitted once at a predefined (possibly random) time after startup (i.e., Figure 3 The preset number in step S306 of the power-on message may be one), or it may be transmitted multiple times after startup with some delays in between. In this case, as indicated above, if the value of the reception counter is greater than one, the receiver needs to distinguish between different senders of the power-on message. This can be done by, for example, including the source address of the sender.

[0078] As a further option, network devices that receive the wireless power up message and know that they have not been power cycled recently may send a response message to the sender of the power up message indicating that this was not a mains power failure.

[0079] In the case where more than one network device (e.g., wirelessly controllable lighting device) is connected behind the same traditional light switch (e.g., Figure 1 ), the preset threshold number of the receiving counter in step S310 should be at least the number of wireless controllable lighting devices behind the light switch minus 1 (for example, Figure 1 1 in ). This can be accomplished by the user configuring the system and indicating which light devices are behind the same conventional light switch. The algorithm is slightly adjusted so that when a power-on message is received from a light device behind the same conventional light switch, the message is ignored. Wherein the power-on message may contain an identifier of the transmitting network device and all light devices behind the same conventional light switch are configured so that they know the identifiers of the other lights behind the light switch, or alternatively, the power-on message contains an identifier of the light switch group.

[0080] As a still further option, the wirelessly controllable network device may ignore power-on messages having a signal strength (e.g., RSSI (Received Signal Strength Indication)) above a certain threshold, assuming that the messages come from a nearby wirelessly controllable network device (and therefore likely part of the same light fixture or light switch group).

[0081] As a still further option, wirelessly controllable network devices may detect that certain other wirelessly controllable network devices always power up (using power up messages) at the same time as themselves, and may use this information to ignore power up messages received from those devices.

[0082] In a more sophisticated embodiment, the wirelessly controlled network device may also enter a learning mode in which it checks which devices report normally (e.g., when the device is in a group). In this case, if, for example, four other lights report power, the network device may determine that this is not a problem, but if more than four lights report power, this may be a problem.

[0083] Alternatively or additionally, wireless controllable network devices can report more information, not only that they have just powered on, but also what type of device they belong to. For example, it is uncommon for a sensor node to report power-on at the same time as a lighting node. Additional information or optional fields of the power-on message can be intermediate counter values ​​of power-on messages received from the reporting node and / or the switching group to which the reporting node belongs. Such additional information can help determine the cause of the power failure. Alternatively or additionally, a second stage can be implemented in which a network device that detects power failure (e.g., a bridge device that is typically not located behind a light switch) reports this using a further broadcast message in order to confirm the discovery of other network devices. This option can increase reliability because when the network device has not recently been powered on, it can respond to the power-on message by broadcasting a message indicating that no power failure has occurred (e.g., "not a power failure"). For all of the above situations, it is also relevant to consider the situation where there is a bridge device with multiple lights in the mesh network, or whether there is a mesh network with only peer devices. In the first case, it may be necessary to appropriately increase the threshold of the required number of power-on messages received to cover all relevant network devices controlled by the bridge device.

[0084] Figure 3 The flowchart in depicts an embodiment in which each device transmits multiple "just started" messages. As a result, the likelihood that a node's startup is registered by other nodes is increased, resulting in more robust system behavior. This may be particularly relevant when devices have different startup times and / or utilize randomized delays before transmitting their startup messages. However, if system performance is less critical, then a single transmission per device may be used, thereby simplifying operation. A single transmission may be combined with a lower threshold number, thereby allowing a limited number of startup message collisions. In addition, the likelihood of collisions may be reduced by increasing the duration of the time window in which the startup message is transmitted.

[0085] In summary, a method and apparatus for automatically detecting whether a wirelessly connected network device with a non-network role is powered on by using a conventional (wall) switch or after a power failure is restored has been described. Based on the results of the detection, an expected behavior of the end user is selected so that the connected network device can behave accordingly.

[0086] Although the present invention has been illustrated and described in detail in the accompanying drawings and the foregoing description, such illustrations and descriptions are considered to be illustrative or exemplary and not restrictive. The present invention is not limited to the disclosed embodiments. The proposed restart control process can be applied to and may be standardized on other types of multi-hop networks and other types of messages and control fields. In addition, the present invention can be applied to any product that implements a wireless network (e.g., ZigBee or others). The present invention is also applicable to network devices of any other wireless technology (e.g., BLE, infrared (IR), near field communication (NFC), wireless LAN communication (Wi-Fi), ZigBee PRO, Thread, Zwave, WirelessHART, CityTouch, IP500, other 802.15.4 networks, or also to 802.11 networked devices and any other grid or tree-based technologies).

[0087] By studying the drawings, the disclosure and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention. 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. A single processor or other unit can implement the functions of several items listed in the claims. The mere fact that certain measures are cited in mutually different dependent claims does not indicate that the combination of these measures cannot be used advantageously. The foregoing description details certain embodiments of the present invention. However, it will be appreciated that no matter how detailed the foregoing appears in the text, the present invention can be practiced in a variety of ways and is therefore not limited to the disclosed embodiments. It should be noted that when describing certain features or aspects of the present invention, the use of specific terms should not be understood to imply that the term is redefined herein as being limited to including any specific characteristics of the features or aspects of the present invention associated with the term.

[0088] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0089] Described similar to Figure 3 The operations indicated in can be implemented as program code means of a computer program and / or dedicated hardware of a debugging device or a lighting device, respectively. The computer program can be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, provided together with other hardware or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

1. A device for controlling a restart mode of a network node (20) in a wireless network, wherein the device comprises: A power-on detector (22) for detecting a power-on event of a network node a message detector (26) for detecting receipt of a wireless power-up message from another network node (30) of the wireless network; and a control unit (21) adapted to select one of a plurality of restart modes in response to detection of a power-on event by a power-on detector (22); The control unit (21) is further adapted to: In response to detection of a power-up event by a power-up detector (22), initiating transmission of at least one wireless power-up message to a wireless network, and Selection of one of a plurality of restart modes is dependent upon an output of a message detector (26), and wherein the power failure mode is selected if the output of the message detector (26) indicates that a predetermined number of wireless power-up messages have been received within a predetermined period of time.

2. The apparatus according to claim 1, wherein the plurality of restart modes at least include: - a safe mode, in which the device is adapted to use a factory setting of non-network functions of the network node (20), and - A power failure mode, wherein the device is adapted to restore a previous state of non-network functions prior to a power-on event.

3. The apparatus according to claim 2, wherein the network node (20) is a lighting device and the non-network function is a lighting function.

4. The device according to claim 1, wherein: The control unit (21) is adapted to restore a previous state of non-network functions of the network node (20) prior to a power-on event when the power failure mode is selected.

5. The device according to claim 1, wherein: The wireless power-on message is selected from ZigBee link status message of 802.15.4 protocol, ZigBee device announcement message, ZigBee inter-PAN broadcast or unicast message, ZigBee broadcast message, ZigBee multicast message, ZigBee unicast message and original message, and the device is arranged to send the wireless power-on message to all previously known neighbor devices.

6. The apparatus of claim 1, wherein the message detector (26) is adapted to distinguish between different sending network nodes by a source address or other identifier included in the wireless power up message.

7. The device according to claim 1, wherein: The message detector (26) is adapted to ignore wireless power-on messages having a signal quality above a predetermined threshold, at least one of a transmitter identifier indicating a network device located between the same light switches (10) as the network node (20), and an identifier indicating the same light switch group as the network node (20).

8. The device according to claim 1, wherein: The control unit (21) is adapted to ignore a wireless power-on message received from another network node based on the previous behavior of the other network node compared to the network node (20).

9. The device according to claim 1, wherein: The wireless power up message comprises information about a type of device transmitting the wireless power up message, and the apparatus is arranged to extract the device type from the wireless power up message.

10. The apparatus of claim 9, wherein the message detector (26) is adapted to detect a power failure report received by the network node (20).

11. A network device, comprising the apparatus according to claim 1, wherein the network device has a non-network function.

12. A method of controlling a restart mode of a network node (20) in a wireless network, wherein the method comprises an apparatus: detecting a power-on event of the network node (20); detecting receipt of a wireless power-on message from another network node (30) of the wireless network; as well as In response to a detected power-on event, one of a plurality of restart modes is selected In response to detection of a power-up event by the power-up detector (22), initiating transmission of at least one wireless power-up message to the wireless network, and Wherein selection of one of the plurality of restart modes is dependent upon an output of a message detection, and wherein the power failure mode is selected if the output of the message detection indicates that a predetermined number of wireless power-on messages have been received within a predetermined time period.

13. A computer program product comprising code for implementing the steps of the method according to claim 12 when the code is executed on a computer device.

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