EP3278544A1

EP3278544A1 - Connecting lighting devices

Info

Publication number: EP3278544A1
Application number: EP15714209.2A
Authority: EP
Inventors: Pedro CARCEDO HERRERO
Original assignee: Intelligent Lumen SLU
Current assignee: Intelligent Lumen SLU
Priority date: 2015-04-01
Filing date: 2015-04-01
Publication date: 2018-02-07
Also published as: WO2016155820A1

Abstract

Lighting devices and methods of associating the lighting devices to a network of lighting devices are disclosed. The lighting devices comprise a wireless controller and a light emitting module operable in response to signals received from the wireless controller. The wireless controller is configured to receive one or more signals emitted from one or more remote lighting devices belonging to the network of lighting devices, respectively. The one or more signals comprise at least a short address. The wireless controller is further configured to identify, among the one or more remote lighting devices, a first remote lighting device emitting the most powerful signal. Then the wireless device is configured to associate with the first remote lighting device by self-assigning a short address based on the short address of the first remote lighting device. The first remote lighting device is thereafter the parental node of the connecting lighting device.

Description

Connecting Lighting Devices

The present disclosure relates to lighting devices and more specifically to connecting lighting devices to networks of lighting devices.

BACKGROUND The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The IEEE 802.15.4 protocol establishes the implementation of radio communications in the first two levels of the scheme defined by the OSI, which are the physical layer and medium access level. IEEE 802.15.4 is a standard which specifies the physical layer and media access control for low-rate (LR) wireless personal area networks (W-PANs).

There are various possible network topologies at the physical layer. In all physical layer network topologies, a node is a connection point, a redistribution point or a communication endpoint. There are several types of nodes: a coordinator node is responsible for managing the network; a full function node is capable of relaying and routing data packets; a reduced functionality node is only able to receive and send data and cannot function as a router. In all network topologies all nodes are directly or indirectly associated with the coordinator node.

In a star network topology all nodes are directly accessible to the coordinator node. In a mesh network topology full function device nodes are capable of relaying and routing the information between other network nodes. In a cluster tree network topology all nodes are associated with one higher level node (parental node) and may be associated with a plurality of lower level nodes (child nodes). Full function device nodes may be parental and/or child nodes. However, reduced function device nodes may only be child nodes.

To communicate in a 802.15.4 network there are two types of addresses, a physical or MAC address (64bits) and a short address (16 bits). The physical address is unique per device and is established by the manufacturer while the short address is typically assigned by the coordinator node for the association.

To establish different networks within the same radio channel it is possible to establish a number that identifies a device to the network and is known as a PAN ID (Personal Area Network Identifier) so that data packets are marked with these numbers and the nodes associated with this private network are able to filter them.

When a device joins a PAN it needs to obtain a short address to identify itself within the network so that when connected it may issue an association request to the PAN.

This request is filtered and relayed throughout the network until it reaches the coordinator node that maintains a table of connected devices and their short addresses. The association process ends with a confirmation sent from the coordinator node to the requesting node. However, the request may be rejected if the number of devices that the coordinator node can handle is exceeded, i.e. the table of connected devices is full, or if the coordinator node decides to reject for any other reason. When the association is accepted the coordinator node transmits the short address to the requesting node and the device is ready to receive or send data. However, the short address can be a maximum number of 16 bits. Therefore, a PAN network may only handle up to 65536 devices.

To manage this data or establish routes for sending these data a higher level (layer) protocol is required, such as ZigBee™. ZigBee uses various algorithms for routing. The basic ones are AODV (Adhoc On Demand Vector) and DSR (Dynamic Source Routing).

Basically, these 2 algorithms need to know the way to send information from one node to another and maintain this information in a table. AODV uses the transmission of beacons (signals) to keep these tables updated at the various nodes. DSR sends a packet every time a communication is started, requesting the path through the network. This causes some latency at the beginning of a communication.

To make this routing table both algorithms use common strategies: -the packages are marked with a source sequence number so that the packages are only forwarded once at each node (this obliges the nodes to maintain the sequence of the information)

-a hop counter is added to know the shortest path between two nodes, therefore the optimal path is established by the fewest number of hops irrespective of the signal^'s strength.

There are two ways to send a data packet under the IEEE 802.15.4 protocol based on the direction:

- by using 16-bit short addresses. This implies the use of the same PAN ID (16 bits). For unicast addressing the short addresses may be within the range 0X0000 - OxFFFE. The address 0X0000 usually is pre-assigned to the coordinator node. For broadcast addressing the short address is common and is OxFFFF. This allows transmission to all nodes.

- by using a 64-bit long addresses. This implies unicast addressing for all transmissions. Each unicast packet may be transmitted with or without acknowledgment request. When acknowledgment is requested any fault is detected at the transmission point and the message is forwarded again.

The ZigBee standard supports lighting devices. This allows for PAN lighting networks to be implemented. Their applications vary from home lighting to street lighting or even city lighting. However, having the coordinator node assigning short addresses to the requesting nodes limits the total number of lighting devices that may be connected in a 802.15.4 network. Furthermore, the various ZigBee algorithms oblige the forwarding nodes to maintain routing tables and information sequences that use up storage and processing resources of the forwarding nodes. This is particularly important when the forwarding devices are lighting devices where storage and processing resources increase the cost of the devices.

It would be desirable to provide devices and methods that at least partially solve the aforementioned problems.

SUMMARY

In a first aspect a lighting device is disclosed. The lighting device is configured to be connected to a network of lighting devices. The lighting device comprises a wireless controller and a light emitting module. The light emitting module may be a light emitting diode (LED) module. The light emitting module is operable in response to signals received from the wireless controller. The wireless controller is configured to receive one or more signals emitted from one or more remote lighting devices belonging to the network of lighting devices, respectively. Said one or more signals each comprises at least a short address. The wireless controller is further configured to identify, among the one or more remote lighting devices, a first remote lighting device emitting the most powerful signal and associate with the first remote lighting device by self-assigning a short address based on the short address of the first remote lighting device. The first remote lighting device is thereafter the parental node of the connecting lighting device. The terms "parental node", "forwarding node" and "retransmit node" are used herein interchangeably.

By self-assigning the short addresses the parental nodes do not need to maintain tables with information of the connected child-nodes. Therefore the number of devices that may belong to the same network is equal to N times the number of levels of the network tree, i.e. 65536 X N in a 16bit short address scheme.

In some examples the wireless controller may be configured to self-assign the short address as a function of the short address of the parental node. In one implementation the short address may be equal to the short address of the parental node incremented by one. This allows a direct association with the parental node.

In some examples each lighting device may further comprise a unique extended address. The wireless controller may then be configured to store the unique extended address of the parental node. This allows for addressing messages directly to the parental node when a message, e.g. an acknowledgment message, is directed to the coordinator node.

In some examples, the wireless controller is further configured to store a power value corresponding to the power of the parental node. This allows the wireless controller to compare the stored power value with the power value of other remote lighting devices. The wireless controller may then maintain the connection to the current parental node only while the power measured from said first remote lighting device is stronger than any other measured power. Otherwise, the wireless controller may be configured to connect to a second remote lighting device when the power from the second remote lighting device is measured higher than the power from the current parental node. As a result, the path from each lighting device to the coordinator node may always be the strongest path and not necessarily the shortest path. By maintaining the strongest path the system may be more robust and may require fewer retransmissions. When connecting to the second lighting device, the wireless controller may be configured to change the self-assigned short address. It may then acquire a short address that is the short address of the second lighting device incremented by one.

In another aspect a network of lighting devices is disclosed. The network may comprise a coordinating node and a plurality of lighting devices arranged in a tree network topology configuration wherein each lighting device is connected to only one parental node. The lighting devices may be configured according to examples disclosed herein. The parental nodes may either be the coordinating node or belong to the plurality of lighting devices. In some examples each lighting device may be configured to identify a received data packet between command data packets and response data packets. Each receiving lighting device may be configured to retransmit a command data packet directed to one or more lighting devices with a short address higher than the short address of the receiving lighting device when the command data packet originates from the parental node. Furthermore, each receiving lighting device may be configured to retransmit to the parental node of the receiving lighting device response data packets received from lighting devices having the receiving lighting device as parental higher level node.

In some examples the wireless controller is configured to retransmit the response data packets using the unique extended address of the parental node and to request acknowledgement of receipt from the parental node. This allows for a fault tolerant network of a large number of nodes to be implemented. The traffic is asymmetric; the majority of messages is transmitted from the coordinator node to the lighting device nodes (to each lighting device). A packet or signal (beacon) may be generated to maintain the current network updated and ensure that each node knows the best way to receive and send data. Therefore, if a node fails or something interrupts the signal, the data can always be received from other alternate nodes even if a node demonstrates a signal weaker than the signal of the current parent node. At that moment a dynamic re-association would take place (no need for acknowledgment), for as long as the failure or loss of signal from the node with the strongest signal lasts. In some examples each lighting device may further comprise a grouping identifier. All lighting devices with the same grouping identifier may then belong to the same group. The grouping identifier may act as a virtual cable or circuit. With the use of the grouping identifier the nodes with the same grouping identifier do not need to be close between them since all the nodes retransmit the data packets even if they do not share the same grouping identifier. Each node is converted to a repeater and eventually all nodes with the same grouping identifier will receive the messages directed to the group.

In another aspect, a method of associating a connecting lighting device to a network of lighting devices is disclosed. The method comprises: receiving a plurality of signals emitted from a plurality of remote lighting devices of the network; measuring the power of each of the plurality of signals; identifying the most powerful signal from the measured signals; identifying the short address of the remote lighting device emitting the most powerful signal; and self-assigning a short address based on the short address of the remote lighting device emitting the most powerful signal. The self-assigned short address of the connecting lighting device may be set equal to the short address of the remote lighting device emitting the most powerful signal incremented by one. The remote lighting device emitting the most powerful signal thereafter is thereafter a parental node to the connecting lighting device.

The method may further comprise storing a unique extended address of the remote lighting device emitting the most powerful signal. Therefore communications may be directed directly to the parental node.

The connecting lighting device may retransmit received command data packets that are directed to lighting devices with a short address higher than the short address of the connecting lighting device when the command data packets originate from the parental node of the connecting lighting device. Furthermore, the connecting lighting device may retransmit response data packets using the unique extended address of the parental node and requests acknowledgement of receipt from the parental node when the response data packets are received from lighting devices having the connecting lighting device as parental node.

In some examples the method may further comprise storing at the connecting lighting device the value of the power of the parental node. In some examples the method may further comprise systematically comparing the stored value with the power values of other remote lighting devices^' signals to determine if the current connection is the most powerful connection. In some examples the method may further comprise self-assigning a new short address if the value of the power of the signal of another remote lighting device is higher than the value of the power of the signal of the current parental node. The new short address may be based on the short address of the other remote lighting device. For example the new short address may be equal to the short address of the other remote lighting device incremented by one.

BRIEF DESCRIPTION OF THE DRAWINGS

Particular embodiments of the present invention will be described in the following by way of non-limiting examples, with reference to the appended drawings, in which:

Fig. 1 shows a network of lighting devices according to an example; Fig. 2 illustrates an example of message routing;

Fig. 3 is a flow diagram of a method of associating a connecting lighting device to a network of lighting devices according to an example.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows a network of lighting devices according to an example. The network 100 comprises a coordinator node 105A and a plurality of lighting devices 105B to 105H. Each lighting device may be a node in the network. The network may be a PAN network. The coordinator node 105A may comprise a short address equal to 0 and a unique extended address. In the example of Fig. 1 the unique extended address of the coordinator node 105A may be equal to 00158D00;;003552A0. The coordinator node 105A may have three child nodes 105B, 105C and 105D. Each of the child nodes may self-assign a short address equal to the short address of the parent node (105A) incremented by 1 . Therefore, the nodes 105B, 105c and 105D may self-assign a short address equal to 1 . In the example of Fig. 1 , the unique extended address of the node 105B may be equal to 00158D00;;003552A1 , of node 105C may be equal to 00158D00;;003552A2 and of node 105D may be equal to 00158D00;;003552A3. Now, the node 105B may be parental node to nodes 105E, 105F and 105G. Therefore, the nodes 105E, 105F and 105G may self-assign a short address equal to the short address of node 105B incremented by 1 . Therefore, the nodes 105E, 105F and 105G may self- assign a short address equal to 2. The unique extended address of the node 105E may be equal to 00158D00;;003552A4, of node 105F may be equal to 00158D00;;003552A5 and of node 105G may be equal to 00158D00;;003552A6. Finally, the node 105D may be parental node to node 105H. Therefore, the node 105H may also self-assign a short address equal to 2. The unique extended address of the node 105H may be equal to 00158D00;;003552A7.

Each lighting device may comprise a wireless controller and a light emitting module (e.g. an LED module with a plurality of LED lights) operable in response to signals received from the wireless controller. The wireless controller may be integrated in a circuit board and may be based on the IEEE 802.15.4 standard. Furthermore, the wireless controller may control illumination parameters of the lighting device, e.g. level of illumination, number of LEDs switched on etc., as well as a number of sensors, e.g. motion detectors, carbon monoxide detectors, cameras (video or photographic), light level sensors or temperature sensors. Lighting devices acting as coordinator nodes may further comprise double connectivity. From one side they may receive instructions through a WiFi or cable Ethernet connection and from the other side communicate with the other nodes of the PAN through the 802.15.4 network to transmit the commands to the various lighting devices of the PAN. During the PAN formation, the coordinator node 105A may send a beacon signal. This beacon signal may be picked-up by lighting devices 105B, 105C and 105D and, as a consequence, these devices may self-assign a short address based on the short address of the coordinator node 105A. The nodes 105B, 105C and 105D may then store the value of the power of the signal received from the coordinator node 105A and the extended address of the parental node 105A. After their association the nodes 105B, 105C and 105D may compare the stored value of the power of the signal with the value of the power of the signals received from the other nodes. If the stored value remains the higher value then the association may be maintained unchanged. Now, when the nodes 105E, 105F and 105G want to connect to the network they may receive a signal from the node 105B as the strongest signal and therefore associate with this node by self-assigning the short address based on the short address of the node 105B. Again, after their association with node 105B, they will store the value of the power of the signal and the extended address of the parental node 105B and will maintain these values as long as the signals received from other nodes remain weaker. Accordingly, when node 105H wants to connect to the network, it may receive a stronger signal from node 105D. It may then self- assign a short address based on the short address of the parental node 105D and store the value of the power of the signal and the extended address of the parental node.

Data packets going through the network may be marked to indicate if they are commands or responses. If they are commands they may always originate from the coordinator node that receives orders from a PC or from some other internal process of the coordinator node. The commands may only be relayed forward, if they come from lower short directions, so that the packets follow an upward direction (i.e. from root to leaves) in the network tree. In the case of responses they travel downwards (i.e. from leaves to root) and are sent from child to parent using the extended (physical or MAC) address (e.g. 64 bits) and with acknowledgment of receipt. This implies a maximum security system and also a robust system since the signal strength is always optimal. In case of a fault, when no acknowledgment is received, the message may be retransmitted a configurable number of attempts (e.g. 3).

No tables need to be maintained with information from the child nodes. It is every child node who holds the address of the parent who is always the node with the strongest signal, and this address is the one used to return the answers to the coordinator. It is assumed that the node emitting the strongest signal is the node that is closer. As the short addesses are self- assigned the maximum number of devices that may be connected is N times the number of bits of the short address, where N is the number of levels. In a 16 bit system, the maximum number is N X 65536, substantially larger than the theoretical limit of other 16bit systems that are limited to 65536 nodes.

At regular intervals, all nodes may compare the stored value of the power of the signal from their parental node with the values of the powers of the signals received from other nodes. In one example, the node 105H may receive a signal from its parental node and may store its power value. Then, it may compare the stored value with the value of the power of a signal received from node 105G and determine that the signal emitted from node 105G is stronger. In that case, it may re-assign its short address to 3 (one higher than the short address of the new parental node 105G) and store the value of the power of the signal of node 105G as well as the extended address of the new parental node 105G. When the coordinator node A wants to address node 105H it may transmit a message that may be received by its child nodes, among them 105B. Then 105B will retransmit the message, as it is not directed to it. The child nodes of 105B, among them 105G, will receive the message and retransmit it as it is not directed to them either. Finally, node 105H will receive the message and recognize that it is directed to it. It will then acknowledge receipt by responding to its parental node, 105G using the stored extended address of 105G. Then, node 105G will receive the acknowledgment message, recognize it as an acknowledgement message and transmit it using the extended address of its parental node, 105B. Finally, node 105B will receive the acknowledgment message from node 105G, recognize it as an acknowledgement message and transmit it using the extended address of its parental node, 105A, which is the final destination. It may be seen that, in this example, the acknowledgment message requires 3 levels to reach the coordinator node. Although this route may not be the shorter one, it is the more robust one and the one that will require fewer retransmissions if anything fails. It may, therefore, minimize any latency in the network.

Now each node may also comprise a grouping identifier ("wirelD") that may act as a virtual cable between all nodes that have the same wirelD. For example, nodes 105B, 105C may comprise a wirelD equal to 1 , while nodes 105E, 105F, 105G and 105H may comprise a wirelD equal to 2. Node 105D may comprise a wirelD equal to 4. In an example, the coordinator node 105A may transmit a command, e.g. a switch-on command, intended to group with wirelD equal to 2. The child nodes 105B, 105C and 105D will pick up the command, see that it is not directed to them and retransmit it. The child nodes 105E, 105F and 105G of node 105B will receive the command and execute it, as it is directed to them. Then, using the extended address of the parental node 105B they will acknowledge receipt and/or execution of the command to the parental node 105B who, in turn, will retransmit the acknowledgment to its parental node 105A that coincides with the coordinator node. In a similar manner, child node 105H may receive the command from parental node 105D and subsequently acknowledge receipt and/or execution to the parental node using the extended address of the node 105D. In turn, parental node 105D will retransmit the acknowledgement to its parental node 105A. Thus the communication is concluded.

The coordinator node 105A may emit broadcast packets or beacon to all devices that use the same channel and belong to the same PAN. These packages may be used to set the time or light values, etc. of any group of nodes as they are broadcast throughout the network. It is noted that the short addresses may be shared among nodes having the same parent and may not be used to send unicast information but they may be used to send information up to one level away (level within the tree).

It is also noted that in ZigBee PANs if a node is not configured in the same PAN ID as the coordinator node, it may not receive data. Therefore, ZigBee PANs are not viable systems to establish groups. In the PANs according to the examples disclosed herein, the nodes broadcast data packets whether or not they have the same "wirelD". Each node becomes a repeater and a node with a wirelD doesn^'t need to be close-by, via radio, to another with the same wirelD. The lighting devices may also comprise sensors e.g. motion detectors, carbon monoxide detectors, cameras (video or photographic), light level sensors or temperature sensors. When a sensor of a lighting device records a signal from one of its sensors it may be required to transmit this information to the coordinator node. This may be done using the extended address of its parental node. For example, node 105E may comprise a motion detector. The motion detector may detect motion and the node 105E may send a message to its parental node 105B containing this information. The parental node will detect that the message comes from a child node and will retransmit the message to its parental node that is the coordinator node 105A. The coordinator node 105A may comprise a database having rules stored with a number of events with the following fields:

(i) a source field. It may comprise the extended address (e.g. 64 bit) of each lighting device

(ii) a type of sensor field. It may indicate the type of sensor or sensors each lighting device comprises. For example: motion detectors, carbon monoxide detectors, cameras (video or photographic), light level sensors or temperature sensors.

(iii) a condition field: It may contain the value of sensor that may activate an event rule. For example a sensor value > n (n being a threshold value), [TRUE | FALSE], etc. (iv) an action field: it may indicate the command sent after receiving an event. For example: switch-on, switch-off, change light level, or send a "trigger action". A trigger action may be defined by a command and a time duration, e.g. after this time duration the light may return to default value. For example, a trigger action may be: "Set maximum light level" for 20 seconds.

(v) a destination field: it may contain a wirelD, a single node identifier (e.g. the 64bit address of the node), or an identifier of all nodes.

In our example, when the coordinator node receives the message from node 105E indicating the detection of motion, it may determine, according to the rules, that e.g. (i) a single node (the node 105E that sent the message) needs to be switched on, or (ii) that a group of nodes (e.g. the group having wirelD equal to the wirelD of the node 105E that had sent the message, i.e. wirelD=2, needs to be switched on, or (iii) that all nodes need to be switched on. Accordingly, if the rule requires node 105E only to be switched on it will send a switch-on command using the 64bit address of node 105E. If the rule requires that all nodes with wirelD 2 need to be switched-on then it will send the switch-on message indicating as a destination the wirelD=2 nodes. Finally, if all nodes need to be switched on, it will send a message directed to all nodes. Therefore, all nodes will receive, act and at the same time retransmit the signal. In all cases, the coordinator node will wait for the corresponding nodes (one, group or all) to acknowledge receipt of the message. Only when all corresponding nodes have acknowledged receipt, will the coordinator node consider the command executed. Otherwise it may require retransmission to the node or nodes that are unresponsive.

Fig. 2 illustrates an example of message routing. In the example of Fig. 2, Node 205A is the coordinator node with short address equal to 0 and is associated with child nodes 205B, 205C and 205D that self-assign a short address equal to 1 . Node 205D is parental node to node 205E that self- assigns a short address equal to 2. The coordinator may send a broadcast message directed for node 205E or to the group where 205E belongs to. The message is received by all child nodes of node 205A. Node 205D receives the message, determines that it is not directed to it and retransmits the message. The node 205E receives the message, determines that it is directed to it and confirms receipt by sending a response to the parental node 205D. The node 205D receives the response, identifies it as a response and retransmits it to its parental node 205A, that coincides with the coordinator node.

Fig. 3 is a flow diagram of a method of associating a connecting lighting device to a network of lighting devices according to an example. In a first step 305,a plurality of signals emitted from a plurality of remote lighting devices of the network are received at the connecting lighting device. Then, in step 310, the power of each of the plurality of signals is measured. In step 315, the most powerful signal from the measured signals is identified. Following this, in step 320, the short address of the remote lighting device emitting the most powerful signal is identified. The connecting lighting device may then self-assign, in step 325, a short address based on the short address of the remote lighting device emitting the most powerful signal. Thereafter, the remote lighting device emitting the most powerful signal thereafter is perceived as a parental node to the connecting lighting device.

It should be noted that although the examples disclosed herein refer to lighting devices, the scope of the disclosure is not limited to lighting devices. Any device or device type connectable in a PAN network may take advantage of the proposed networking method.

Furthermore, although only a number of particular embodiments and examples have been disclosed herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses and obvious modifications and equivalents thereof are possible. Furthermore, the disclosure covers all possible combinations of the particular embodiments described. Thus, the scope of the disclosure should not be limited by particular embodiments.

Further, although the examples described with reference to the drawings comprise computing apparatus/systems and processes performed in computing apparatus/systems, the disclosure also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the system into practice.

Claims

1 . A lighting device configured to be connected to a network of lighting devices, comprising: a wireless controller; and a light emitting module operable in response to signals received from the wireless controller, wherein the wireless controller is configured to: receive one or more signals emitted from one or more remote lighting devices belonging to the network of lighting devices, respectively, said one or more signals comprising at least a short address, respectively; identify, among the one or more remote lighting devices, a first remote lighting device emitting the most powerful signal; associate with the first remote lighting device by self-assigning a short address based on the short address of the first remote lighting device, whereby the first remote lighting device is thereafter the parental node of the connecting lighting device.

2. The lighting device according to claim 1 , wherein the wireless controller is configured to self-assign the short address as a function of the short address of the parental node.

3. The lighting device according to claim 2, wherein the wireless controller is configured to self-assign the short address by incrementing by one the short address of the first remote lighting device.

4. The lighting device according to any of claims 2 to 3, wherein each lighting device of the network of lighting devices further comprises a unique extended address and wherein the wireless controller is configured to store the unique extended address of the parental node.

5. The lighting device according to any of claims 2 to 4, wherein the wireless controller is further configured to store a power value corresponding to the power of the parental node.

6. The lighting device according to claim 5, wherein the wireless controller is configured to compare the stored power value with the power value of other remote lighting devices and maintain the connection to the current parental node only while the power measured from said first remote lighting device is stronger than any other measured power.

7. The lighting device according to claim 6, wherein the wireless controller is configured to connect to a second remote lighting device when the power from the second remote lighting device is measured higher than the power from the current parental node.

8. The lighting device according to claim 7, wherein the wireless controller is configured to change the self-assigned short address to connect the lighting device to the second remote lighting device.

9. A network of lighting devices comprising a coordinating node; and a plurality of lighting devices according to any of claims 1 to 8, arranged in a tree network configuration wherein each lighting device is connected to only one parental node.

10. The network of lighting devices according to claim 9, wherein the parental nodes are either the coordinating node or belong to the plurality of lighting devices.

1 1 . The network of lighting devices according to claim 10, wherein each lighting device is configured to identify a received data packet between command data packets and response data packets.

12. The network of lighting devices according to claim 1 1 , wherein each receiving lighting device is configured to retransmit a command data packet directed to one or more lighting devices with a short address higher than the short address of the receiving lighting device when the command data packet originates from the parental node.

13. The network of lighting devices according to claim 1 1 or 12, wherein each receiving lighting device is configured to retransmit to the parental node of the receiving lighting device response data packets received from lighting devices having the receiving lighting device as parental higher level node.

14. The network of lighting devices according to claim 13, wherein the wireless controller is configured to retransmit the response data packets using the unique extended address of the parental node and to request acknowledgement of receipt from the parental node.

15. The network of lighting devices according to any of claims 9 to 14, wherein each lighting device further comprises a grouping identifier, wherein all lighting devices with the same grouping identifier belong to the same group.

16. The network of lighting devices according to any of claims 9 to 15, wherein the coordinating node is configured to generate a beacon signal to maintain the network of lighting devices up-to-date.

17. A method of associating a connecting lighting device to a network of lighting devices comprising: receiving a plurality of signals emitted from a plurality of remote lighting devices of the network; measuring the power of each of the plurality of signals; identifying the most powerful signal from the measured signals; identifying the short address of the remote lighting device emitting the most powerful signal; self-assigning a short address based on the short address of the remote lighting device emitting the most powerful signal, wherein the remote lighting device emitting the most powerful signal thereafter is a parental node to the connecting lighting device.

18. The method according to claim 17, wherein the self-assigned short address of the connecting lighting device is set equal to the short address of the remote lighting device emitting the most powerful signal incremented by one.

19. The method according to claim 18, further comprising storing a unique extended address of the remote lighting device emitting the most powerful signal.

20. The method according to claim 19, wherein the connecting lighting device retransmits received command data packets that are directed to lighting devices with a short address higher than the short address of the connecting lighting device when the command data packets originate from the parental node of the connecting lighting device.

21 . The method according to claim 19 or 20, wherein the connecting lighting device retransmits response data packets using the unique extended address of the parental node and requests acknowledgement of receipt from the parental node when the response data packets are received from lighting devices having the connecting lighting device as parental node.

22. The method according to any of claims 17 to 21 , further comprising storing at the connecting lighting device the value of the power of the parental node.

23. The method according to claim 22, further comprising systematically comparing the stored value with the power values of other remote lighting devices^' signals to determine if the current connection is the most powerful connection.

24. The method according to claim 23, further comprising self-assigning a different short address if the value of the power of the signal of another remote lighting device is higher than the value of the power of the signal of the current parental node.

25. A computing device comprising a memory and a processor, wherein the memory stores computer program instructions executable by the processor, said instructions comprising functionality to execute a method of associating a connecting lighting device to a network of lighting devices according to any of claims 17 to 24.

26. A computer program product comprising instructions to provoke that a computing device implements a method of associating a connecting lighting device to a network of lighting devices according to any of claims 17 to 24.