WO2007040398A1

WO2007040398A1 - Method of installing a wireless network component

Info

Publication number: WO2007040398A1
Application number: PCT/NL2006/050241
Authority: WO
Inventors: Cornelis Adrianus Henricus Maria Van Puijenbroek
Original assignee: Xanadu Wireless B.V.
Priority date: 1995-07-03
Filing date: 2006-10-02
Publication date: 2007-04-12

Abstract

A method of installing a wireless network component is disclosed. The signal strength of a data packet communicated between the wireless network component and a further network component is measured. The measured signal strength is used to enable the installation of the wireless network component. Several embodiments using the measured signal strength are described. The method enables a fast installation with a reliable connection of the wireless network component, wherein the wireless network component is bound with another network component.

Description

Method of installing a wireless network component

Field of the invention

The present invention relates to a method of installing a wireless network component. In a further aspect, the invention relates to a network component arranged to enable wireless communication with another network component and a computer program product.

The invention has particular application in wireless infrastructure employing wireless communication devices and protocols in which unique device identifiers are assigned to devices and/or support the "association" and "binding" of devices as part of the protocol. ZigBee is an example of such smart wireless protocols.

Prior art

Such a method is known from existing applications, e.g. in the form of ZigBee applications. ZigBee is a smart wireless networking and security stack that sits on top of an 802.15.4 MAC layer radio. 802.15.4 according to local regulations specifies the frequency bands, the number of channels, the spreading technique and the modulation method. ZigBee controls how data is routed between 802.15.4 physical layer radios and encryption, adding mesh and encryption capability along the way. ZigBee relates to a low power network system that functions by relaying a data packet from source node to destination node over a number of interim (relay) nodes that may not be related to the two nodes but share a common protocol.

The IEEE 802.15.4 network may be used as a low power wireless sensor and control network, e.g. applied in home automation, lighting and security, heating, ventilation and air-conditioning systems or industrial automation. These kinds of applications require sensor and control nodes in the network, which can be battery, operated, or even powered by energy recycling or energy scavenging techniques such as solar energy.

There are typically three types of devices specified: a coordinator, a router and an end device. The coordinator and router are sometimes referred to as Full Function Devices or FFDs. The end device is sometimes referred to as a Reduced Function Device. The coordinator is responsible for setting the channel for the network to use, making its presence known by routers and end devices, assigning network devices to routers and end devices and keeping the routing tables for the network that are necessary to route data from one (ZigBee) device to another in the same (ZigBee) network. Each network must have one and only one coordinator. Without a coordinator, a network cannot be formed.

The router, as its name implies, is responsible for routing data from other routers or end devices to the coordinator or to other routers, end devices or coordinator. The router can also be a data input device, either serially or through the I/O pins of the router.

The end device can only communicate with the coordinator or a router. An end device cannot communicate directly with another end device. Communication between one end device and another end device must go through the coordinator and may go through one or more routers and/or the coordinator. To enable communication the nodes have to be associated to the network around the coordinator and next, the nodes have to be bound. Association is depending on devices having matching network parameters that are stored in memory. Binding is the creation of a (virtual) permanent connection between two wireless network nodes. Thus, if we have a protocol compatible local lighting network and a protocol compatible heating network which carry data for each other, the binding parameters will prevent the network component binding in the wrong context - the room thermostat will not be able to dim the lights.

In time or event driven network routers and coordinators will always be powered and never put to sleep as they must always be awake since they do not know when another device may attempt to communicate. In a beacon network the coordinator controls when communications may occur and so it may be that both coordinator and routers may sleep between beacons and measures must be employed to cover these situations.

End devices on the other hand, are expected to send data for a brief period of time and then go to sleep for the majority of the time. Since the end device is normally asleep, any data addressed to it will be held by the router (or coordinator) with whom it is associated. When the end device wakes up, it can send a request for the router (or coordinator) to send any data it may be holding. In a beacon network the end device wakes up to receive a beacon with an indication of data hold by the router or coordinator.

Patent application EP0870384 discloses a method of installing a wireless control network. The method uses a special wireless installation tool and RF portable computer in conjunction with a central building computer to install a node by wireless programming of said node.

The ZigBee Alliance has defined profiles for various applications. One of these is the HCL (home control, lighting) profile with regard of control over light switches, light dimmers, light sensors, occupancy sensors etc. by means of on/off commands, dim/bright commands, present level (for dimmer), light level reading (light sensor), occupancy state (occupancy sensor) etc. Furthermore, ZigBee defines a protocol layer built on the IEEE 802.15.4 Medium Access Control (MAC) and Physical Layer (PHY) protocol layers.

ZigBee / IEEE 802.15.4 is covering the description of the message and frame types at various levels. The initiative for various actions like with regard to joining or to leaving a network, is part of the device system design and such initiative allows a certain degree of freedom that is not covered by the standards. A new device that wants to join a ZigBee network, will perform a ZigBee search to find a nearby ZigBee router (or coordinator) of the right network. Next, such a device will forward an associate request to that selected ZigBee router to get associated (at the MAC layer) and then the network join and authentication process can be completed by exchange of a few messages. When the new device has joined network, there can be set up a communication link at the APL (application layer) to allow communication as with APS (application sub layer) commands by the end user with a remote control for a light switch. With ZigBee such a link set up between a pair of devices is called a binding. The ZigBee protocol stack is disclosed in ZigBee Document 02130r9, Network Specification Rev. 10, version 1.00, Dec. 14, 2004. The device system design covers some pre-programmed actions, IDs and keys, and it allows some programmable data and addresses. With HCL applications it is desired to provide a simple and flexible binding approach without the need of entering address information (like the long IEEE 802.15.4 source and destination addresses, each of 64 bits) to assign a remote control to a single lamp or group of lamps. Wireless control gives the possibility for increased flexibility and other major benefits to ordinary people. To expedite installation of a wireless network it is a basic requirement that all the functionality of a network device is very easy to install, preferably, without the requirement of special tools or specialist technical knowledge.

Summary of the invention

The present invention seeks to provide a method to simplify the installation of a wireless network component.

According to the present invention, the method of installing a wireless network component comprises:

- measuring the signal strength of a data packet communicated between the wireless network component and a further network component,

- if the measured signal strength exceeds a predefined level, binding the wireless network component and the further network component. The object of the invention is achieved by making the network component more intelligent. By means of the measured signal strength of a data packet the network components can determine without special user input whether a network component has to be added to the network. The measured signal strength can be used as a proximity parameter or a communication reliability parameter to perform a decision on allowing a bind or a higher protocol layer. Such a decision based on the signal strength depends on the distance between the wireless network component and the further network component. The shorter the distance the higher the signal strength. In normal use the distance between a coordinator and an end device is several meters or more. By bringing the end device in close proximity (much shorter than one meter) to the network device to be bound with, the coupling between the two devices can be enforced.

In a further exemplary embodiment of the invention the method comprises - if the measured signal strength exceeds the predefined level a second time, unbinding the wireless network component and the further network component. This feature allows to undo the installation and to reuse the wireless network component in an other configuration. Bringing the end device, for instance a light switch, for a second time in the proximity of a router comprising for instance a controllable lamp, is used as an indication for the network that the binding between the light switch and controllable lamp is not necessary any more and could be unbound.

In a further embodiment of the invention the wireless network component measures the signal strength. This embodiment is very suitable to be used in a mesh/ cluster tree and beacon networks however could also be used in other network configurations. In a mesh network the coordinator is responsible for the network and the routing of data from one device to another, which could be over several routers or relay nodes. Using the measurement of the signal strength in an end device, allows the device to determine the signal strength to communicate with a network and not the signal strength to communicate directly with the coordinator. Normally, in a mesh network the signal strength is defined by the distance between an end device and a router. In an exemplary embodiment of the invention the wireless network component will be bound with the further network component. This feature is very useful in peer- to-peer network configuration, wherein the signal strength is used as a proximity parameter to enable the binding between the two network devices.

In a further exemplary embodiment of the invention the method comprises

- measuring the signal strength of data packets transmitted by more than one further network component;

- selecting from the signal strength exceeding a predefined value, the strongest measured signal strength to enable the binding of the wireless network component. Use of this feature allows to bind with the network component with the best connection with respect to signal to noise ratio. In the event the transmission power of all transmitters is equal, the signal strength is an indication of the distance between the transmitter and the receiver. In a further embodiment of the invention the method comprises:

- retrieving from a data packet transmitted by a further network component a transmit power level value; and

- measuring comprises correcting the measured signal strength by means of the transmit power level. This feature enables to correct the signal strength with respect to the transmit power level of the transmitter. The thus obtained normalized value of the signal strength is an indication of the distance between the transmitter and the receiver, which makes it possible to bind with the network device, which could be a controllable lamp, which is closest to the remote control to be bind. In an further embodiment the transmit power level value is a difference between the transmit power level and a nominal power level

In a further embodiment of the invention the method further comprises maintaining the binding between the wireless network component and further network component when the signal strength of subsequent data packets drops below the predefined level. This feature enables that as soon a remote control is bound with a controlled lamp, this binding will exist even when no communication is possible between the remote control and lamp due to the distance between said devices. As soon as the devices become again in there respective transmission area, the devices can communicate with each other without installing the remote control again and binding the remote control with the network.

In a further embodiment of the invention maintaining further comprises: - using other network component to enable the communication between the wireless network component and the further network component. This feature enables to have a distance between two bound devices which is too large for direct communication between said devices. By maintaining the binding between the two devices and changing the associations in the network, the communication between the two devices is still sufficient reliable while the transmission path of the packets over the network changes dynamically with the movement of the wireless device. In this way, the most reliable transmission path between the two devices can be assured.

In a further embodiment of the invention the method further comprises binding to a second network component if the measured signal strength of a data packet transmitted from said second network component exceeds a predefined value. This feature enables to bind the wireless network component to more than one network device. For instance, one switch can be bound to two or more lamps to enable simultaneous control of the lamps.

In an embodiment of the invention the binding corresponds to a higher layer protocol connection set-up, for instance the ZigBee APS layer. This feature enable to bind devices at application layer and not at the data link layer (OSI model level 2) and network layer (OSI model level 3). This improves the possibilities to use an end-node in a network system and the ease of installation/deinstallation of a network component by a user as he does not have the set network addresses and to define the network path over the network. The method of the invention is suitable for all types of transmission technologies which enable the determination of the signal strength, such as a radio frequency signal strength, magnetic field strength or light strength.

The present invention further seeks to provide a network component arranged to enable wireless communication with another network component, comprising a structure to enable to carry out the method according to the invention. The structure comprises in an exemplary embodiment a memory carrying software instruction to be processed on a general purpose processor. In another exemplary embodiment the structure comprises a state machine carrying out the method according to the invention. The present invention further seeks to provide a computer program product comprising computer executable instructions which instructions when executed on a network component perform the method according to the invention, which enables to program very easily a device capable to communicate wireless to execute the method according to the invention.

Short description of drawings

The present invention will be discussed in more detail below, using a number of exemplary embodiments, with reference to the attached drawings, in which

Fig. 1 shows schematically a wireless lighting network; Fig. 2 shows a simplified block diagram of an embodiment of a data transceiver device according to the present invention;

Fig. 3 is a simplified flow graph schematically illustrating a method of identifying a data transceiver device in accordance with the present invention;

Fig. 4 shows schematically a wireless security system; Fig. 5 is a simplified flow graph schematically illustrating another method of identifying a data transceiver device in accordance with the present invention; Fig. 6 shows schematically a wireless lighting network; and, Fig. 7 shows schematically another wireless lighting network.

Detailed description of exemplary embodiments

Fig. 1 shows schematically a wireless lighting network configuration. The configuration comprises a first lamp 100 connected to a first control unit 102 and the mains supply 104. The control unit 112 could be any electronic switch or triac, to enable dimming of the lamp 100. The control unit 102 obtains a control signal from a first central node unit 106. The configuration further comprises a second lamp connected to a mains supply 114 and a second control unit 112. The second control unit 112 obtains a control signal from a second central node unit 116. The configuration further comprises a first end node unit 108 and a second end node unit 118. The end node units could be powered by a battery or a mains supply. The end nodes could be in the form of wall mounted RF switches, RF dimmer controllers, mobile RF remote controls, RF light level sensors, RF occupancy sensors, RF switches controlled by a time clock, etc. The central node units 106, 116 control the switching of the power of the lamps or the lamp dimming ballasts. The central node units will normally control certain lamps in the vicinity but not others.

In this exemplary embodiment the first central node unit 106 is arranged to receive commands from a first end node unit 108 and a second end node unit 118. The second control unit 112 is arranged to receive only commands from the second end node unit 118. In this configuration the first lamp 100 is controllable by two input devices, and the second lamp 110 is controllable only via the second end node unit 118. These configurations are difficult to implement with conventional wired systems and prohibitive cost-wise to modify due to the cost of installation of the wires. Furthermore, particularly with normal dimming systems only one dimmer can be used. The wireless systems are able to be very flexible and expansion is only the cost of an extra end node unit multi-point dimming can be realised.

Fig. 1 discloses two networks, one for each lamp. In practice there may be a number of such networks in proximity of each other such that the devices receive each other network signal. It is important that these networks do not interact. In an exemplary embodiment of method of installation according to the invention an end node unit will be installed by bringing the end node close to the central node unit which controls the desired lamp. Preferably the end node unit is reinitiated by a battery power-up or a dedicated (hidden) reinit button in the close proximity of the central unit. When assuming the end node unit and the central node unit are close enough to each other, the signal strength for receiving each other will exceed a predefined level. The procedure to couple or bind two devices is not discussed in more detail as this depends on the used protocol or system, which details are regarded to be commonly known to the person skilled in the art. With a Zigbee/802.15.4 network the end device has to be associated (and joined to the network) at first before the binding procedure (at the ZigBee APS layer) can be started. The method described above could be repeated for each desired node combination so that the desired functionality is achieved. For example, the second end node unit 128 is first hold in the proximity of the first central unit 106 and subsequently in the proximity of the second central unit 116. When the desired functionality is achieved the end node unit is mounted in its final location. Because the network association is normally based on unique MAC addresses and the binding takes place at a higher (application) level, extra network functionality can be performed. In special cases a (hidden) reinit button can be used to enforce a second binding to allow control by a single end node unit over more than one central node unit. Likewise, a (hidden) reinit button can be used to couple more than one end node units to a single central node unit.

Fig. 2 shows a simplified block diagram of an embodiment of a data transceiver device 200 according to the present invention. The data transceiver device could be used in an end node unit as well as a central unit. The data transceiver comprises a transceiver unit 202, a node processor 204, a memory 206 and interface circuitry to external component arranged for specific applications (not shown). The node processor 204 could be implemented by means of a microprocessor or a state machine. The memory 206 could be in the form of battery supported RAM or non- volatile memory and is used for retaining configuration data. The data transceiver device could be a single chip solution or assemble from discreet components. Furthermore, an antenna 210, xtal 212 and power supply 214, battery or mains supply, are connected to the transceiver device 200. The transceiver further comprises an application unit 208. The application unit 208 is arranged perform any kind of sensor or control application, such as temperature measurement/control, speed measurement/control, pressure measurement/control, smoke detection, door or light switches. Application of the invention is not limited to the mentioned applications. The application unit may be equipped with interface circuitry, e.g. for connecting to an external sensor (not shown) or an external device (not shown). Such external device could be a building control unit. The application unit 208 could be implemented in software or hardware or any other combination of software and hardware.

The transceiver 202 is arranged to receive packets and to forward the corresponding information derived from said packets to the node processor 204. The transceiver 202 is further arranged to transmit packets based on the commands received from the node processor 204.

The transceiver unit 202 of at least one of the devices to bind comprises circuitry for measuring the strength of the received radio signal. In general this is known as the RSSI or Received Signal Strength Indication. The signal strength could be supplied to control circuitry in the node processor 204. If the signal strength is an analogue signal, the signal strength could be supplied to a comparator circuit and a logic signal will be generated indicating that the signal strength has exceeded a predetermined value. This logical signal will then be used to enable the binding operation. Alternatively, the signal strength could be converted in to a digital value which is supplied to the node processor 204, which would perform the corresponding comparison with a value stored in the memory 206.

The RSSI level will rise as the two devices are brought closer together. Whilst being dependent on the transmission power of the end node, the reception sensitivity and the efficiency of the antennas, these parameters are however substantially constant for any similar manufactured devices, so the predetermined level could be a preset value. Consequently the binding procedure will be initiated and performed reliably at known distance.

By bringing the two devices into close proximity and causing normal RF communications to occur (such as pushing a hidden reinit button or reinstalling the end node unit its battery) at a distance where the RSSI level has exceeded the predetermined level, this signal will then be used as an enable signal to the node processor to proceed during the binding procedure a successful bind. The preceding association procedure and binding procedure depend on the used protocols which define the handshake communication to be executed. After binding and association the devices will interact corresponding to there functionality.

In the wireless lighting network the end units work on event based operation. The central node of a lamp unit will be almost constantly in receiving mode and will react immediately to any signal transmitted by a compatible end node in the close vicinity, and so the operation will be completed quickly.

Confirmation of the binding may be controlled by withdrawing the end device to a reasonable distance beyond the binding procedure distance and operating it to verify normal and expected control functions. The circuitry to measure the signal strength could be in a central node or an end unit. If the circuitry is in a router node the cost of the wireless network can be dramatically reduced. This could be very beneficial in a star network, wherein the central node corresponds to the further network and the end node corresponds to the wireless network component. In such a network the circuitry to measure the signal strength is present only once. If in a lighting application the number of controllable lamps, which comprises a router, and the number of switches, which comprises an end node, is almost the same, there is no preference where the circuitry to measure the signal strength should be build in. An end node comprising the circuitry to measure the signal strength is very suitable to be used in a mesh/ cluster tree and beacon networks however could also be used in other network configurations. In a mesh network the coordinator is responsible for the network and the routing of data from one device to another, which could be over several routers or relay nodes. Using the measurement of the signal strength in an end device, allows the device to determine the signal strength to communicate with a network and not the signal strength to communicate directly with the coordinator. Normally, in a mesh network the signal strength is defined by the distance between an end device and a router. In an exemplary embodiment the wireless network component will be bound with the further network component. This feature is very useful in peer- to-peer network configuration, wherein the signal strength is used as a proximity parameter to enable the binding between the two network devices.

A lamp unit comprising a central unit will be mounted in a fixed location and will be powered from the mains voltage. If a light switch/dimmer or other control unit comprising an end node unit is held within a predetermined distance and activated by placing the battery the binding will occur and the switch will always operate that particular lamp unit. The central node unit will store a unique identifier of the end node unit, so as to react only on commands transmitted by said end node unit.

This may then be repeated with other lamp units that the switch will control or bind to, and similarly each lamp may bind with more than one switch or dimmer. In that case the central node unit is arranged to store more than one unique identifier in a memory. The combinations in which the switches, control units and lamps may work with each other to give maximum flexibility are many. The invention enables that these combinations can be easily achieved.

There could be a number of independent network components in the reception area of the network component to be installed. It is of importance that these should not conflict with each other during the installation and normal operation. Therefore, a device according to the invention is arranged to accept one binding at a time during a single binding procedure. Therefore, the sensitivity to the proximity which has a relationship with the measured signal strength is set so that the network component to be installed will be bound with two networks simultaneously.

In the event an installed end node unit is brought a second time in the proximity of the central node with which it is bound and activated, this action will de-install the end node. In this way devices could be reused in the network, obsolete functionality could be removed or erroneous unintended connections could be reversed. The invention could be used in a system where the remote or end node unit contains only a transmitter and the central unit contains both a receiver and transmitter. The same procedure is used. The central unit will measure the RSSI level obtained by the received signal transmitted by the end node unit. If the RSSI level exceeds the predefined level a unique identifier of the end node is recorded in the memory of the central node as a binding parameter. As the end node unit does not have a receiver there is no need to acknowledge the binding.

It should be noted that the invention is not limited to RF systems but could also be used by magnetic field communication systems, or optical communication systems. In general, the invention is suitable in a communication system in which a relationship exist between the measured signal strength and the distance between an end node unit and a central node unit.

An installation procedure for installing a wireless network for example a wireless lighting network could be as follows. In a first step a central node, for instance a controllable lamp, is physically placed and installed in the desired location. In a second step, the central node is connected to a power supply and powered up. In a third step, an end node, for instance a remote switch, is unpacked and a battery inserted in the end node. In a fourth step, the end node is brought within a prescribed distance from the central node and the communication between the end node and central node is initiated. This could for example be done automatically by means of power-up detection or by means of an input given by the user. Some examples of input given by a user are pushing an installation button or using one or more buttons in a prescribed manner (a hidden button). In a fifth step, the end node is brought beyond the installation distance and correct operation is tested. In a sixth step the end node is placed in its final destination. The sixth step is required if the end node is for example in the form of a wall mounted switch or dimmer.

The first and second step have to be repeated for each central node to be installed. At least the third to fifth step have to be repeated for each end node to be installed. If an installed end node has to be bound with a second central node or more central nodes, the fourth and fifth step have to be repeated for this central node also.

Fig. 3 is a simplified flow graph schematically illustrating a method of installing a data transceiver device in accordance with the present invention. A power up will be detected [step 301] when a battery is inserted or the device is connected to the mains supply. Subsequently, the device sets a channel and predetermined period to monitor the channel for a packet [step 302]. The device could for example scan a beacon according to the ZigBee standard. Next, the device scans the selected channel for a packet for a predetermined time until [step 303]. If a packet is received [step 304] the method will proceed with step 305. From said packet some characteristics will be determined [step 305]. Characteristics that could be determined, are the signal strength of the packet, the individual number of the sender of the packet, the network to which the sender belongs. Next, the determined signal strength of the packet is compared with a predetermined value x [step 306]. If the determined signal strength exceeds the predetermined value, the channel corresponding to the packet will be used to associate with the transmitter that transmitted the corresponding packet. In that case, the data transceiver device will associate and bind with the device that had transmitted the packet and consequently the transceiver device will be associated with the corresponding personal area network [step 307] and subsequently the method will be ended. If the determined signal strength is lower than the predetermined value [step 306], the device will scan for a packet for the remaining time of the period set in step 303. If no packet has been received in the whole period or remaining time, the device will determine whether other channels have to be scanned [step 308]. If no packet has been received at all, the device could decide to repeat the method from step 302 onwards until a signal with minimum acceptable signal strength has been found.

It should be noted, that if only one channel is used within the wireless lighting system, step 308 will be obsolete. Depending on the implementation, the method will end or repeat the procedure by returning to step 302.

A transceiver according to the IEEE 802.15.4 performs the determination of the signal strength by a LQI measurement. LQI is a short for Link Quality Indication measurement and is a characterization of the strength and/or quality of a received packet. The LQI measurement is performed for each received packet. Each of the results is reported to the node processor. The minimum and maximum LQI value could be associated with the lowest and highest quality signals detectable by the transceiver. Furthermore, from the packet received could be determined the identifier of the transmitter that sent the packet.

The method described above is very suitable to set up a peer to peer network or a star network. However, for mesh networks as may be typified (but not limited to) in security or HVAC (heating ventilation air conditioning) system networks, another installation method based on signal strength is required. Such network systems work normally throughout a building.

A mesh network comprises normally only one central node and many end nodes. The distance between an end node and the central node may become so large that the nodes may not be able to communicate directly with each other. Therefore, relaying nodes are strategically placed for relaying of data from one node to another, to enable the communication between an end node and a central node over long distances. As a relaying node only passes data from one node to another, a relaying node does not play part in the system functionality. A relaying node could be used simultaneously by more than one network, for example security network and HVAC network. Fig. 4 shows a security network with security sensor end nodes, relaying nodes and a central node. A central node could perform simultaneously the function of control node, central node and relaying node. Mesh networks could work on beacon operation basis where the central node is regularly polling the end nodes for information. The end nodes in beacon based networks are often battery powered. The end nodes will wake up briefly for this interrogation at a predetermined time point and return to sleep mode when an acknowledge signal, indicating that data has been correctly exchanged, is received.

Furthermore, if in a beacon network an end node is transmitting out of sequence then no response will be given on data received. Therefore, to install a new end node, the end node must be formatted in order to program that it is permitted to join the network (out of sequence) and that it has to find the corresponding central node across the network.

An installation method according to the invention will be described to allow each end node to be installed and enabled or powered for the first time to seek the strongest signal from a central node or relaying node that would support the end node in joining the network, subsequently the network is joined and a link to the central node of the network is established.

The end node could also make use of the RSSI signal value but differently. The installation of an end node in a network will be discussed by means of the security network in fig. 4. In the system is a central unit or alarm unit that receives and if necessary acknowledges signals from sensors in the system. Sensors in the system may be: occupancy/movement detectors, proximity detectors (in doors or widows controlling if they are open or close) glass break detectors etc. etc.

First the central node and the relaying nodes have to be installed and powered up. The relaying nodes have to be strategically placed so that the network coverage is sufficient in the entire building. Subsequently, sensor nodes are installed and added to the network one at a time. The method also provides that the network could be expanded or extended from time to time.

When an end node is placed for the first time and powered up it is pre- programmed to scan passive or active to allow the identification of an appropriate central or relay node that permits association with the network.

Once the beacon cycle period or periods has passed the central node ID's will repeat, and at this point the most suitable node may be chosen.

Because each central node or relay node has an own ID number, this may be logged against the respective signal strength measured from the RSSI circuits.

At this point a procedure will be instigated by which the remote node is first joining the network, and then seeking across the network a device with which it may associate which is assumable the desired central node, if the central node is acknowledging the ability to associate then a binding is created and the end node will join the network.

This will be facilitated by the end node having initially an identifier or flag programmed in to identify that it is "not-bound" to another node and with this flag active it will be given access to the network temporarily in order to search a central node to bind with. This identifier or flag is preferably stored in non- volatile memory of the end node. The remote node is arranged to transmit a packet comprising an indicator indication that the remote node is not bound with a network. The relaying nodes should be arranged to relay the packets with said indicator to a central node. The central node should be arranged to detect said indicator, and to determine whether the remote node transmitting the packet is allowed to associate and bind with the network. If so, the central node will transmit to the remote node a packet indicating that the remote node is bound to the network.

Once the binding is made the "not bound" value will be removed from the memory or deactivated. The device is then installed and will start to perform the desired function in the network.

In case where the end node cannot find a central node with which it may associate over the network corresponding to the strongest signal strength, the procedure will be repeated over the node with the second strongest signal and so on until a successful association and binding is achieved.

The corresponding method of installing a network component could be software instructions in the memory of the micro-processor or instigated in a state machine integrated within the node processor of the end node.

In the situation where the network is non-beaconed or the beacon network can exceptionally accept asynchronous inputs, the node itself will instigate communication across the network, on the basis of comparable signals that have been received within a pre-programmed or reasonable period for that network. The received signals are examined for similarly profiled central nodes. Subsequently the similarly profiled central node with the strongest signal will be selected and the associating and binding procedure will follow.

The installation procedure for installing a wireless network component in accordance with the above described exemplary embodiment comprises a first step to unpack and activate the end node. In the second step the end node is mounted in the desired location. In the third step, the end node searches for the strongest signal of a network that enables binding. In the fourth step the operation of the end node in the network is confirmed. The procedure above has to be repeated for each additional end node to be installed. Fig. 5 shows a simplified flow graph schematically illustrating a method of installing a data transceiver device in a mesh network. The method differs from the method disclosed in Fig. 3 in the step 321 and 322. In this method all channels to be scanned, will be scanned for a predetermined period. From all the packets received during said scan, some characteristics, including the signal strength or quality, will be determined [step 305]. Furthermore in step 305 is determined whether the end node is permitted to associate and bind over the network with the central node which transmitted the corresponding packet. The signal strength, the transmission channel and at least one identifier of the corresponding central node determined from the received packet will be stored in a list [step 321]. The identifier of the central node could be for example the individual address of the transmitter or a personal area network identifier. After scanning all channels for said predetermined period, a transmitter to associate with will be selected from the list [step 322]. For example could be selected the transmitter belonging to the packet from the list with the highest signal strength. It should be noted that the result of the method disclosed in fig. 3, could also be implemented with the method disclosed in fig. 5. Step 322 should then be arranged to compare sequentially the signal strength of a received packet with a predetermined value, starting from the first entry in the list up to the first entry in the list for which the signal strength exceeds the predetermined value X.

With a data transceiver device according to the IEEE 802.15.4 the list can be obtained by performing a passive scan request. This request is used to locate all coordinators transmitting beacon frames in the operating space of the data transceiver device. The scan is performed on all channels indicated in the request. In a channel more than one coordinator can be found. The method allows selection in a specific channel the coordinator with the highest signal strength and thus most likely to have the best data connection or link.

Another method to find the most reliable connection could be done by an ED measurement. ED is a short for Energy Detection and is an estimate of the received signal power within an IEEE 802.15.4 channel. The measurement may be implemented using a receiver ED measurement, signal- to noise ratio estimation, or a combination of these methods. The receiver ED measurement is intended for use as part of a channel selection algorithm. During an ED measurement no attempt is made by the node processor to identify or decode signals on the channel. The ED measurements allow selection of the channel with the highest signal power and thus most likely the best signal to noise ratio. After selecting the channel with the highest signal power, the device has to perform the steps 302 up to 307, to select a transmitter, which is transmitting via the channel selected by means of the ED measurement, to associate with. These steps have to be performed as on a channel more than one coordinator or even personal area network could be active.

It should be noted that the predetermined time could be a fixed time, for example ten minutes. The predetermined time could also be defined by the individual number of the sender of the packet. For example, if the device is powered the device could store the individual number of sender of the first received packet. The individual address could be the unique address of the relay or central node which actually transmitted the packet. The unique address could if necessary be combined with the network identifier, if relaying nodes are used by more than one network. After reception of the first packet with has an individual number, the device will measure the signal strength of packets until a packet with the same individual number will be received. A wireless network component to be installed could be in the range of two beacon networks. In that case the wireless network component has to be arranged to measure the signal strength of data packets for each beacon network for at least one beacon period to be sure that the signal strength of each devices in the beacon network could be measured. Consequently the predetermined period is defined by the instant that for each beacon network a packet with an individual number corresponding to the individual number of the first packet of said beacon network has been received.

Fig. 6 illustrates an other example of the invention in the form of a wireless lighting network. The network comprises remote controls (end node units) and controlled lamps (lamp + control unit + router). ZigBee network 500 has a tree structure and consists of a remote control / ZigBee end device 501 and a ZigBee coordinator 502, ZigBee routers with controllable lamps 503 - 506 and ZigBee routers without lamps 507 - 508. Other devices can be part of the same ZigBee network 500, but are not depicted. Of the depicted devices only remote control / ZigBee end device 501 is battery powered, while the other devices are mains powered to allow permanent access and to supply power for the lamp in a more practical way.

At first, remote control / ZigBee end device 501 is held nearby the controlled lamp / ZigBee router 504 to perform the binding after pushing a hidden reinit button or reinstalling the end node unit its battery and next, it is moved away over different positions as depicted. When the remote control comes more near to respectively the ZigBee routers 505, 507 or 506, it associates with these devices and stays bound to the controlled lamp / ZigBee router 504. By the ZigBee network it communicates via among other ZigBee routers 508 and 503 and not directly to the controlled lamp / ZigBee router 504.

Binding defines at application level which source device and destination device communicates with each other. Binding does not define the actual network path that is used to transmit a data packet from a source device to a destination device. The actual data path is defined by the association. In the given example in figure 6 when the remote control 501 is bound to the controllable lamp 504, they are close to each other and consequently the remote control 501 is also associated with controllable lamp 504. Which means that remote control 501 transmits data packets directly to controllable lamp 504. However, when the remote control 501 is moved to the neighbourhood of controllable lamp 505, the remote control 501 will associate with controllable lamp 505 and stays joined with the ZigBee network 500 with coordinator 502. In the given examples for transmitting a data packet from the remote control 501 to controllable lamp 504 via controllable lamp 505 which functions now as a router, remote control 501 is associated with controllable lamp 505, controllable lamp 505 is associated with router 507, router 507 is associated with router 508, router 508 is associated with route 503 and router 503 is associated with controllable lamp 504. In this way the remote control 501 continues its functioning with respect to the lamp 504 in question while it has been moved eventually into another room.

The mechanism to create and maintain a binding could also be explained in the following way. The binding between a remote control / ZigBee end device 501 and a controlled lamp / ZigBee router 504 can only take place with a short distance between these two devices. The binding of the ZigBee end device 501 is initiated by means of pressing a (hidden) re-init button or button combination, or by powering the device up again with a battery. After the two devices have been bound, the remote control 501 is assigned to control the lamp 504 in question. When somebody moves away with that remote control 501 the binding between the two devices will stay established. The remote control / ZigBee end device 501 can communicate active (or passive) to the ZigBee network 500 at regularly intervals by sending 'alive' messages at regular intervals that are replied, or listening to beacons. In case the distance between the remote control / ZigBee end device and the controlled lamp / ZigBee router becomes larger, or the signal strength becomes too low for a predetermined time, the remote control / ZigBee end device 501 will make a disassociate with respect to the first router and will start looking for another ZigBee router that is part of the same network characterised by the same ID. Then, the remote control / ZigBee end device might decide to associate with another router that can be also a controlled lamp / ZigBee router. If the remote control is associated with a controlled lamp this does not mean that the remote control could control said lamp, association indicates only that the router in the controlled lamp is used for communication. Next, it might be that the remote control / ZigBee end device might decide again to associate with another router within the same network after a disassociate related to current router to which the remote control is currently associated. In this way the remote control / ZigBee end device 501 will stay connected with the network and communicates no longer directly to the controlled lamp / ZigBee router to which the remote control is bound. However, the remote control 501 communicates via one or more ZigBee routers to control the lamp 504. The routers used to establish the communication between the remote control 501 and controllable lamp/ ZigBee router could function also as a controlled lamp / ZigBee router.

With ZigBee radio and other communication systems the receive level of a message transmitted by the source station is measured by the addressed destination station(s). The circuit in a receiving station that measures the received signal level, and/or the measured level is called the RSSI (receive signal strength indicator) (level). In general the RSSI measurement circuit is embedded in the receiver gain stages. In common the measured RSSI value is subjected to limitations in accuracy and the range of level measurement. The 802.15.4 standard defines some requirements for the RSSI accuracy and level range (with respect to moderate receive levels), and these apply also for ZigBee radio's. Often the measured RSSI value has a numerical representation that is linear to actual receive level in dBm, as long as this receive level is within the RSSI measurement range. The strength of the electromagnetic signal that arrives at the receiving station antenna, is dependent on the distance, antenna properties of both transmitter and receiver, reflections and obstructions. With relative short distances between the transmitter and receiver, the receive level is in general dominated by the (free space) distance path loss and the antenna properties. With ZigBee radio systems the stations are in general provided with small size, low cost antennas with limited directional gain. Normally such antennas at both the transmit and receive side and a short unobstructed path will be present. Then, in case the RSSI measurement provision covers a range that includes relative high receive level as occurring with those short distances, the measured RSSI value will have a relationship with the distance between the transmitter and receiver. This is because the free space path loss formula approximates the power loss between radio front ends of transmitter and receiver. The present invention uses this approximation to compare during the binding process the measured RSSI level with a predetermined threshold value which corresponds to a small distance. Under free space propagation conditions and with omni directional antennas a radio operating at 2.4 GHz with a transmit power level of 0 dBm (1 mW) a data packet is received with 10 cm distance at -20 dBm, with 30 cm distance at -30 dBm and with 1 m distance at -40 dBm. With ZigBee devices that have quasi-omni directional antennas the measured RSSI value will approximately reflect these levels for the given distances.

In an embodiment of the present invention a predefined value corresponding to an RSSI of -30 dBm reflecting a minimum required distance of 30 cm for the binding is used.

In another embodiment of the present invention the binding between a remote control / ZigBee end device and a single controlled lamp / ZigBee router will only take place with the one that provides the highest receive level or the actual ZigBee RSSI level. In this embodiment the bind request is addressed to more than one controlled lamp / ZigBee router all within a short distance, consequently transmitted data packets from these devices are all received with a signal strength above the predefined RSSI threshold level. During such a binding process the remote control / ZigBee end device in question selects the controlled lamp / ZigBee router that provides the highest RSSI level.

In another embodiment of the present invention ZigBee devices could forward during the binding process in a data packet a representation of the transmit power level. The measured signal strength is corrected with the retrieved transmit power level representation to derive a normalized signal strength, as would occur with a reference transmit power level. This enables to use a fixed threshold level which corresponds to a predefined minimum required binding distance.

Figure 7 illustrates an example of the embodiment given above. Shown is a part of a ZigBee network 600 for light control application. The network 600 has a ZigBee coordinator (that is not depicted), ZigBee routers (these are not depicted) and controllable lamp / ZigBee routers 602, 603, 604 and remote control / ZigBee end devices 601. In the network 600, only the remote control / ZigBee end devices are battery powered. The routers and coordinator are mains powered. When remote control / ZigBee end device is attempting to bind with a lamp after installing a battery, or by pressing a re-init button (combination), all controlled lamp / ZigBee routers 602, 603, 604 will forward to remote control / ZigBee end device 601 in some sequence a response message with their transmit power level information, that represents 0 dBm, - 6 dBm and +3 dBm respectively. In Figure 6 remote control 601 has a distance of 40 cm, 25 cm and 100 cm from respectively controllable lamps 602, 603 and 604.

Without correction device 601 will measure an RSSI level representing respectively -32 dBm, -34 dBm an -40 dBm. However, remote control 601 will correct the RSSI level based on the forwarded transmit power level information representing an offset of 0 dB, -6 dB and +3 dB respectively with regard to a 0 dBm reference. Consequently, device 601 will compare the corrected measured RSSI level of respectively -32 dBm, - 28 dBm and -37 dBm with the RSSI level threshold of -30 dBm. Now as normalized signal strength values are used, the signal strength is a representation of the distance and as a result the binding between devices 601 and the nearest one, 603, will take place. In another embodiment of the present invention the controllable lamp / ZigBee router 602, compares the RSSI level with a predefined threshold to allow the binding or not (in stead of the remote control / ZigBee end device).

In another embodiment of the present invention the binding within a light control ZigBee network has a pre-programmed limitation of the number of controllable lamps / ZigBee routers that could be controlled by a single remote control / ZigBee end device.

During the device production or by some installation technician the maximum number of lamps that be controlled, could be programmed. Before an enforced binding will be completed within the distance limit and the RSSI threshold is exceeded, the remote control / ZigBee end device compares the number of already bounded devices with that programmed maximum number. In case the remote control / ZigBee end device had already a number of bounded devices equal to the maximum, the remote control /

ZigBee end device will not allow the new binding.

In another embodiment when a remote control ZigBee end device is bound with the maximum number of devices and said remote control allows a new binding, the remote control / ZigBee end device will unbind the controlled lamp / ZigBee router that was bounded for the longest time. This could be implemented by a dedicated bind follow-up number, which is a pointer to the memory location in a list comprising the bindings. In a specific embodiment of the last two embodiments the maximum number of bindings is fixed at 1. Such an embodiment leads to only one remote control per controlled lamp, with either the first or the latest enforced bind.

Several embodiments of the invention have been described above by way of exemplary embodiments. Various modifications and variations for the elements described with respect of these embodiments may be made by skilled persons without departing from the scope of the present invention, which is defined by the appended claims.

Claims

1. Method of installing a wireless network component, comprising:

- if the measured signal strength exceeds a predefined level, binding the wireless network component and the further network component.

2. Method as claimed in claim 1, further comprising: - if the measured signal strength exceeds the predefined level a second time, unbinding the wireless network component and the further network component.

3. Method as claimed in claim 1 or 2, wherein the wireless network component measures the signal strength.

4. Method as claimed in any one of the preceding claims, further comprising

- selecting from the signal strength exceeding a predefined value, the strongest measured signal strength to enable the binding of the wireless network component.

5. Method as claimed in any one of the preceding claims, further comprising:

- retrieving from a data packet transmitted by a further network component a transmit power level value; and - measuring comprises correcting the measured signal strength by means of the transmit power level.

6. Method as claimed in claim 5, wherein the transmit power level value is a difference between the transmit power level and a nominal power level.

7. Method as claimed in claim 1, further comprising maintaining the binding between the wireless network component and further network component is maintained when the signal strength of subsequent data packets drops below the predefined level.

8. Method as claimed in claim 7, wherein maintaining further comprises:

- using other network component to enable the communication between the wireless network component and the further network component.

9. Method as claimed in claim 1, further comprising:

- binding to a second network component if the measured signal strength of a data packet transmitted from said second network component exceeds a predefined value.

10. Method as claimed in any one of the preceding claims, wherein the binding corresponds to a higher layer protocol connection set-up.

11. Method as claimed in claim 10, wherein the higher layer protocol connection setup is the ZigBee APS layer.

12. Method according to any one of the preceding claims, further comprising transmitting a data packet comprising an indicator indicating that the wireless network component is not bound with a network.

13. Method according to any one of the preceding claims, wherein the signal strength is a radio frequency signal strength or magnetic field strength or light strength.

14. Method as claimed in any one of the preceding claims wherein the network component is an end node unit and the further network component is a central node unit.

15. Network component arranged to enable wireless communication with a further network component, comprising a structure to carry out the method according to any one of the preceding claims.

16. Network component according to claim 15 wherein the network component is arranged to transmit an indicator indicating that the network component is not bound with a network.

17. Network component according to claim 16 wherein the network component is arranged to receive an indicator indicating that the further network component which transmitted said indicator and arranged to enable binding of network component with the further network component.

18. A computer program product comprising computer executable instructions which instructions when executed on a network component, perform the method according to any one of the claims 1 to 14.