WO2007060638A2

WO2007060638A2 - Initialisation of communication between wireless devices

Info

Publication number: WO2007060638A2
Application number: PCT/IB2006/054441
Authority: WO
Inventors: Jeremy Moss
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-11-28
Filing date: 2006-11-27
Publication date: 2007-05-31
Also published as: WO2007060638A3

Abstract

A wireless device (10) has a transceiver (20) and a device detector (60) to detect the presence nearby of another wireless device without using the transceiver, the wireless device being arranged to use the detection to determine a channel for the transceiver to start communication with the given other wireless device, and to start the communication. Having a separate detector enables the transceiver to avoid having to listen for long periods to detect other devices, to save transceiver power consumption. Having the channel determined according to the detection means that the transceiver need not scan many channels. Also, user set up or input can be minimised by having the communication start according to the detection. The detector is arranged to produce detection signals in both devices with related timings to synchronise the transceivers.

Description

DESCRIPTION

INITIALISATION OF COMMUNICATION BETWEEN WIRELESS DEVICES

FIELD OF THE INVENTION

This invention relates to a wireless device, to a networks of such devices, and to a method of initiating communication between wireless devices.

BACKGROUND

Most communications systems require a form of addressing that enables devices to communicate with each other by using this address to indicate the intended recipient. Examples of this include IP address, (and their domain name equivalents), telephone numbers, and MAC (Medium Access Control) addresses. In all of these cases, it is necessary to define a unique address for each device connected to the shared communications medium. By reducing the potential set of connected devices, the requirement on the size of the address space reduces which has the advantage of requiring less memory to store the addresses, and needing less time (and therefore less energy) to communicate them. The limit to this reduction is a shared medium that guarantees that only two devices can access it at a single time. In this instance, explicit addressing is no longer required as the recipient is implied by the absence of any other devices.

A common method of allowing the user to specify a particular recipient is to provide a user interface that allows them to either enter a particular user, or select from a list of possibilities. Examples of this include a telephone keypad, or the URL (Universal Resource Locator) box of a web browser. As a further example Bluetooth™ links typically require the user to respond to prompts displayed on a mobile phone screen for example. Generally speaking, the more sophisticated the user interface (such as a keyboard and screen), the more intuitive this process becomes (due to the added feedback given to the user). Devices where space and/or power is more of an issue, must make do with more limited interfaces. For example, Bluetooth headsets often require the user to follow a series of abstract button presses to enter the device into a suitable learning mode where it can be paired with a phone. To provide an intuitive user interaction paradigm that does not require sophisticated user-interface components, the two devices can be linked in such a way that implied addressing can first be used, i.e. they are the only two possible users of the communications link). In this mode, address information is exchanged which can then allow the devices to operate in a more open environment using explicit addressing. An example of this would be to use NFC (Near Field Communication) between two devices initially, before using standard RF (Radio Frequency) communications after the pairing process. Apart from the requirement to have an address to exchange, and the overhead involved in transmitting the destination address, the main disadvantage of this approach is that a separate technology is required to enable this process, which adds to the costs and power consumption budgets.

It is also known from US patent application 2002/132585 to communicate using inductive transducers which couple to each other via magnetic flux unlike RF antennas. To avoid interference when multiple transceiver devices attempt to share an available bandwidth to communicate with each other, each device is given a unique code in the form of a sequence of bits identifying a relationship between two or more transceivers for exclusive communications. If a received message includes an unexpected or unknown communication code, the message can be ignored. The contents of one or more received messages can be analysed to determine whether a transceiver device generating the inductive field has already been programmed with a unique communication code. If not, bidirectional communications can be established to program the transceiver device with a unique communication code over an inductive link. An activation protocol such as orientation or position of a transceiver can cause one or multiple transceivers to be initialised with a communication code. To initialise a pair of transceivers with a code, the transceiver devices can be moved in close proximity to each other. Proximity of a transceiver can be detected by sensing the strength of a received signal or orientation of the inductive field.

US patent application 2003/162556 shows the problem of making connection of wireless peripheral devices easier and faster. Two wireless- enabled devices each have a wireless handshake plug. Each plug is capable of receiving and sending data to the other plug. The two wireless-enabled devices are "handshaked" by connecting the plugs. Data is transmitted from one plug to the other to establish the wireless communication, such as network addresses. The plugs can make physical contact or use any means for establishing a communications link between the plugs, while being in physical proximity with each other.

SUMMARY OF THE INVENTION It is an object of the invention to provide improved apparatus or methods.

According to a first aspect of the invention, there is provided a wireless device able to communicate with one or more other wireless devices, the device having a transceiver and a device detector to detect the presence of a given one of the other wireless devices without using the transceiver, the wireless device being arranged to use the detection to determine a channel for the transceiver to start communication with the given other wireless device, and to start the communication.

Having a separate detector enables the transceiver to avoid having to listen for long periods to detect other devices. This can save transceiver power consumption. Having the channel determined according to the detection means that the transceiver need not scan many channels to find which one works before it can communicate. This can save power and can avoid the need to pre program the devices with allocations of channels to particular devices, so they can be more generic and thus simpler to manufacture and manage. Also, user set up or input can be minimised by having the communication start according to the detection.

An additional feature of some embodiments is the detector being arranged to cooperate with the given other wireless device to produce a detection signal in both devices, the detection signals having related timings, and the wireless device being arranged to synchronise the transceiver to the other wireless device according to a timing of the detection signal of the wireless device. This enables both devices to be generic, and not need any pre- programming of which channel to use. There is no need to pre-determine unique addresses or relationships between many such devices, which can make set up much simpler, particularly where there are many such devices. Furthermore a dynamic network is easier to achieve since if another device is detected subsequently, the old pairing can be undone without administrative overhead, and a new pairing can be established. Again this can occur without the need for a user to reconfigure each device.

An additional feature of some embodiments is the transceiver being arranged to listen for transmissions only after the detector has produced the detection signal. This enables the transceiver power consumption to be reduced since lengthy listening periods before detection can be avoided. An additional feature of some embodiments is the channels being time slots, and the determination involving selecting a slot at a time or times referenced in a predetermined way to the detection signal. This enables both devices to know when the other will be listening, and so helps enable communication without wasting power by needing lengthy listening periods. Interference from other pairs can be avoided or reduced since provided there is a sufficiently low duty cycle, the chance of other pairs transmitting in the same slot and within range can be controlled. Other conventional multiplex techniques can be combined such as frequency division, frequency hopping or code division if needed, though this adds complexity. An additional feature of some embodiments is the transceiver using the same frequency for initiating communication as other wireless devices, and using a duty cycle for the communication which is lower than 1/n where n is the total number of pairs able to transmit. This enables the devices to rely only on the low duty cycle and the random timing of the detection, to avoid interference from other pairs when initiating communication. Once initiated, each pair can agree a different duty cycle or other ways of avoiding interference as desired according to power budget and bandwidth needs of the application amongst others.

An additional feature of some embodiments is the detector having part of a circuit, arranged such that the other wireless device can complete the circuit, and the detector being arranged to detect completion or breaking of the circuit. This is a convenient way of ensuring that the same event has been detected by both devices; the event can then be used as a synchronisation reference for both devices.

An additional feature of some embodiments is the circuit being any one or more of: an electrically conductive path, an optical path, a magnetic flux path, an acoustic or vibration path, a fluidic path, a mechanical linkage path, and a path for any radiation.

An additional feature of some embodiments is the device communicating without using a predetermined network address, and without being pre-programmed to communicate with specified other wireless devices.

This avoids or reduces the need for administration of network addresses, and helps simplify or avoid set up for the user.

An additional feature of some embodiments is the detector comprising a switch arranged to cause power up of the transceiver after physical contact of the device with the other wireless device is broken off. This enables power consumption by the transceiver to be reduced.

An additional feature of some embodiments is the transceiver having a range of less than 20m, or a power consumption of less than 1OmW when transmitting or receiving. Other embodiments can have higher ranges and higher power consumptions. An additional feature of some embodiments is the wireless device being arranged to communicate with more than one other wireless device. This enables one to many broadcasting, or network configurations such as star or ring networks. Another aspect is a network having a plurality of the wireless devices mentioned above.

An additional feature of some embodiments is at least some of the wireless devices having any one or more of: a sensor, an output device, and a computing device, and the network being arranged to communicate any one or more of: sensing data from the sensors to a monitoring point, commands to the output devices at different locations, and data to or from the computing device. This can be useful for creating a sensing network which can be set up easily and reconfigured easily with less administrative effort. This can be a peer to peer or other type of network as desired. It can be useful for creating any type of output network which can be set up easily and reconfigured easily with less administrative effort. Output devices can encompass, for example, mechanical actuators, display devices, audio output devices, and information processing devices. The output devices can be combined with sensors or a network of sensors and/or networks of computing devices. Another aspect provides a method of setting up a network of two or more wireless devices, each having a transceiver and a device detector to detect the presence of another of the wireless devices, and being arranged to use the detection to determine a wireless channel, and start communication with the detected wireless device using the channel, the method having the steps of initiating wireless communication with the other wireless device using the transceiver, by moving either wireless device into or out of the presence of the other wireless device to cause the detection, and to cause the channel to be selected, and to cause the communication between the wireless devices to start. An additional feature of some embodiments is the movement causing the wireless devices to produce detection signals in both devices, the detection signals having related timings, and the same channel being determined in both devices according to the timing of the detection signals.

Another aspect provides a wireless device able to communicate with one or more other wireless devices, the device having a transceiver and a contact detector to detect physical contact with a given one of the other wireless devices in one or more predetermined relative orientations, the wireless device being arranged to use the detection to start communication and pair with the detected wireless device.

Compared to proximity detectors, a contact switch can be simpler to manufacture and can avoid inadvertent detection. Hence user initiation of communication by moving a device can be made more definite. This can enable storage of devices more easily without triggering operation. This aspect reflects that the advantages of definite user initiation can arise whether the channel is determined according to the detection or otherwise. Another aspect provides a wireless device able to communicate with one or more other wireless devices, the device having a transceiver and a device detector to detect the presence of a given one of the other wireless devices without using the transceiver, the wireless device being arranged to use the detection to switch on the transceiver, and to start communication with the given other wireless device without user input.

This can avoid power wasted by listening for transmissions. It enables power to be saved during the shelf life of the product without the need for a user operable power switch. Again this aspect reflects that the power saving can be achieved whether or not the channel is determined according to the detection.

Additional features and advantages will be described below. Any of the additional features can be combined together or with any of the aspects of the invention, as would be apparent to those skilled in the art. Other advantages may be apparent to those skilled in the art, especially over other prior art not known to the inventors. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a pair of wireless devices according to an embodiment; Figure 2 shows some of the principal operations of an embodiment;

Figure 3 shows a sequence chart of events according to an embodiment;

Figure 4 shows networks of devices;

Figures 5 and 6 show circuits for detecting other devices; Figures 7 and 8 show views of devices in contact and separated according to embodiments; and

Figures 9 and 10 show principal operations according to further embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

The term "wireless" is intended to encompass any type of transmission without wires including RF, optical, inductive, acoustic or any other type. Transceiver is defined as a transmitter and a receiver, or a transmitter only, or a receiver only The embodiments described below involve administering a wireless network of multiple low power radio nodes that can be embedded into a variety of devices. The nodes are all identical in nature (optionally they can differ) and are not given addresses, nor are they pre-programmed with a specific partner with which to communicate. It is desired that the user can specify which device they wish their wireless node to communicate with, in an environment of multiple similar nodes. The two 'paired' devices must then communicate successfully without interfering with communication channels of other similar devices. The point-to-point network established between a paired set of devices can remain for the duration of the devices' lifetime, or until they are either switched off or paired with a different device. One way of achieving this is pairing two identical radio nodes by physically connecting and/or separating them and using the time of connection or of separation to define a time slot in a TDMA (Time Division Multiplexed Access) based physical layer. In TDMA, communicating devices are assigned a time slot on a shared communications channel. These devices must then communicate only during that slot which is specified by the protocol to be free for their purposes. TDMA is typically used as part of a more complex communications protocol where many devices with individual addresses are configured to use a particular time slot for a particular communication event, such as the duration of a phone call. There must, therefore, be a mechanism by which devices are assigned time slots. The embodiments provide a way of maintaining the use of implicit addressing through TDMA timeslots, without the need for an extensive control infrastructure to manage these timeslots. Figure 1 shows an embodiment in schematic form. Two wireless devices 10 are shown, though many can be used. In each of the devices a transceiver 20 is controlled by a controller 40 and transmits and receives using an antenna 30. Conventional hardware can be used for each of the elements. A detector in the form of a proximity or contact detector 60 is provided. This can detect the presence of another wireless device 10. Again this can be implemented using conventional hardware in the form of contact switches, or optical or infra red transmitters and mirrors for example, or inductive loops to form a circuit for magnetic flux for example. For most purposes if the detector is a proximity detector, it will have a short range of detection, shorter than the range of the transceiver, so that it can detect devices nearby, such as within 10cm. In principle longer ranges of detection might suit some applications, and ranges greater than the transceiver range might be useful to enable search for hot spots or to provide early warning of other devices. The transceiver can be for two way or for one way communication, and in some embodiments can have a range of less than 20m. If the device is a mobile device, low power consumption can be an advantage. In some cases a power consumption for the transceiver of less than 1OmW when transmitting or receiving is envisaged.

Other functions of the device are represented by item 50. This can encompass for example application software for information processing, a sensor or an output device such as a display, an audio output device or a mechanical actuator such as a motor, relay, or hydraulic piston for example. For some applications, some user interaction with the device is useful by means of a user interface 70. The transceiver 20 can communicate with the transceiver 20 of the other device 10 to pass information between devices 10, and the detector 60 can cooperate with the detector 60 of the other device 10 to detect the presence of the other device 10.

Figure 2 shows some of the principal steps in operation of the arrangement. At step 100 the user moves the wireless device near or in contact with another device. At step 110, the detector detects the other device. Subsequently, at step 120, the user separates the devices, and the detector detects the separation at step 130. At step 140 the transceiver transmits to the other device depending on the timing of the detection events. This can involve for example synchronising timeslots for transmission, based on start or end of detection, or could involve selecting a frequency according to a time interval between start and finish of detection for example. In the case illustrated, the transceiver transmits a predetermined time after separation, and the transceiver listens at step 150 to the other device, for a short time interval, a predetermined time after separation. At step 160 both devices confirm they are in communication and agree how to continue. This can involve continuing with a TDMA time slot with a low duty cycle, or changing to other schemes to increase bandwidth or reliability for example, if the power budget allows. In some cases a low power budget is used for the standby mode, and a higher power budget is available once the device has been paired and becomes active. This is suited to products which may have a battery or other power source which needs to be conserved during "shelf life " but which can be replenished during operational life, for example by a solar panel or other energy scavenging source. As discussed above, the user input and complexity can be kept to a minimum if there is no addressing needed and no set up other than simply moving the devices into contact or into proximity, perhaps with a given orientation, to initiate communication and create a small ad hoc network of two or more devices. The start of communication can also have the effect of switching on other functions in the device, for example a sensor, other input devices, or output devices.

With reference to Figure 3, an embodiment is shown with two devices 1OA and 10B. A sequence of events is shown with time flowing from left to right. Two cases are shown by the two horizontal lines. In both cases the user joins and then separates the devices. In a first case, the communication is triggered by the separation, indicated at time T₀. In the second case, the communication is triggered by the joining of the devices, so T₀ is earlier. Both cases therefore make use of the extremely simple and intuitive mechanism of the user physically touching together, and then separating, the desired pair of devices 10A, 10B to cause communication to start and network pairing to take place. This embodiment can use proximity or contact detection on one or all surfaces, or can rely on the specific nature of certain objects to be stacked or linked in some way together. Examples of such objects include tiles, bricks, containers, plates and books. Sensors on the object detect when the device has been stacked with a similar device in a particular orientation, and place it into state A. This helps avoid triggering the devices unintentionally when they are stored together in a container without being stacked for example. When the devices are separated, both devices detect this change and switch into state B. The application protocol defines either the entry or exit of state A to be time T₀. At this instant, both devices initialise a synchronisation timer to zero. After a protocol-specified period of time t_sync, the devices communicate and confirm their clock synchronisation. From this point on, their 'timeslot' is set, ensuring that the devices only communicate at this instant once every polling period t_pon which is also specified by the protocol. The period of time tsync may be the same as or different to the period of time t_pon . Period t_sync could be set to zero, or set to allow sufficient time to power up the transceiver and run any warm up tests. It can be less than t_pon to provide an early confirmation of communication to a user. The initial duty cycle is effectively the transmission duration divided by t_sync and immediately afterwards is set by the transmission duration divided by t_pon

In this way, devices can exist in a radio environment with other similar devices that communicate in different timeslots. This time division multiple access scheme relies on the fact that the communicating time slot is extremely short compared to the polling period of the protocol, as the lower the duty- cycle, the lower the probability that two time slots will coincide. This duty cycle can be predetermined to suit the application or can be adjusted in use by the pair, and increased gradually, within limits of available power budget and amount of interference detected by the pair for example. The unique and detectable event of two devices being separated, allows this TDMA scheme to be implemented without the need for either an independent arbitrator, or some form of network awareness in the devices.

Some of the advantages of this are reduced device and network complexity.

Detecting the separation of two devices is slightly more application specific, but is in general, simple. A particular example is given in the embodiments below. It should be noted that orientation of attached devices could be used to control the action of the protocol. For example, devices in the form of bricks stacked in one orientation would follow the procedure described above, while in the opposite orientation, would continue operation unaltered (effectively remaining in State B). Device markings could be easily used to indicate the orientations required.

If two devices do happen to initialise in an existing device-pair timeslot, error detection and correction schemes built into the protocol should allow devices to detect and recover from this. Possible recovery mechanisms may include delaying the timeslot by a specified period of time or, if the application allows it, indicating to the user that the devices need to be reattached and separated again. It is possible to use multiple devices on a single channel by reintroducing schemes such as device addresses or encryption. This would be useful in situations where the low power consumption advantages are used but the number of devices to be serviced is more than could be supported from a single multiplexing scheme.

An example embodiment of this protocol could be in the area of children's building bricks. Radio nodes embedded in bricks could provide functionality such as LEDs (light emitting diodes), buzzers, and motion detection and children would be encouraged to build models that utilised these elements. Bricks would be supplied initially in stacked form so that the nodes would be in State A, defined in this example as having the nodes off. As the child builds the model, they would separate two bricks knowing that those bricks would then communicate with each other. As the bricks were built into the model, they would know that by placing them in the opposite orientation to which they were initially supplied, possibly indicated by colouring on the bricks, the bricks would remain active in the model. The pairings or networks created could be used for remote control or remote sensing or other communication purposes. If at a later stage, a friend appeared with a different set of bricks with new functionalities, these bricks could be incorporated into the existing model simply by connecting and then separating the new bricks with the old bricks, therefore forming new point-to- point links.

The network initialisation scheme could be expanded to incorporate one to many communication paradigms. One way of doing this is by specifying that if bricks are separated within a specified time window, the devices will communicate to allow the inclusion of them all in the timeslot access scheme.

Another method involves a packing mechanism that ensures that once one device is separated, all devices break-apart. The separation is then used as the synchronising signal. This could be achieved by arranging a mechanical connection between all devices, which loses its rigidity once one device is removed (similar to the keystone in an arch).

Another way of achieving multiple device pairing would be to use a detector that passes the presence or absence signal between its two ports, the device supporting two other devices, one either side. If the devices are arranged in a circular fashion, perhaps as sectors of a circle, the absence of one device would be detected by its neighbours and this signal propagated through to all the other devices. This is a specific example of a type of AND operation as it requires all devices to be present to generate the synchronising signal.

Alternatively, or as well, once paired, a device can be paired with another device without losing the first pairing so that the first pair can be coupled to other networks or form a network of three or more devices. This can be implemented in various ways, for example a predetermined duration of detection could be used to determine that the existing pairing is not to be broken. Conventional networking protocols can be used on top of the one to one connections or pairings created as described above. Figure 4 shows examples of networks. In this case, a pair 75 is formed by two devices 10. One of the devices has a further connection to other networks 80 such as the internet. Of course there can be many such pairs and they can be linked together to form larger networks. In the same figure an ad hoc network 85 is formed by two devices 10 as described above, and by a device 15 with a sensor, and a device 25 with an output. An ad hoc network is defined as one with a topology which is built up as needed or without central control. These devices are put into communication with each other as described above. In this case one of the devices acts as a hub for multiple sensors or output devices. Complex networks can be built up simply by pairing devices by moving them into contact with each other, or into proximity with each other, with minimal administration overhead. In principle there can be three types of devices 10, sensor devices 15, output devices 25 and computing devices, and devices 25 combining two or three of these functions. The hub can be an example of a computing device, or each of the sensing devices 15 or output devices could be provided with computing power. Hence in principle there can be three types of these ad hoc networks, distributed computing networks, sensing networks and output networks, and networks combining two or three of these functions.

Although described with regard to TDMA, the communication could use other forms of multiplex. For example the devices could cycle through many frequency bands to use for transmission and reception, referenced to the time T₀ from the detector. This can be implemented by using the duration of the contact / proximity event to seed a pseudo random number algorithm to select a frequency. As both devices know the duration of the event, both devices will select the same frequency channel to communicate on. Another implementation uses the contact / proximity event to reference against an external signal common to both devices such as absolute time provided from the Global Positioning System (GPS) system or another radio time signal. Again this common reference allows independent selection of a common operating channel. These are examples of the more general principle of both devices requiring an integer value that is common. This can be obtained from two mutually identifiable trigger events by subtracting the time between them as described above; or from a single event which has magnitude that can be reliably quantised and identified by both devices; or using one binary event to sample a variable common to both devices, as in the GPS example above).

Figures 5 and 6 show examples of the devices 10 with more details of circuitry for implementing the detector 60. Other examples can be envisaged, for example employing an optical path, a magnetic flux path, and acoustic or vibration path, a fluidic path, a mechanical linkage path, or a path for radiation. In the cases of Figures 5 and 6, an aim is to ensure that both devices detect a connection or separation at the same time. Figure 5 shows a circuit using two connectors for connecting with corresponding connectors of another device. Three devices are shown. Device 10A has one of the connectors connected to ground, and another connected via resistor R to a power supply. Device 1OB has two pairs of connectors. The connectors facing device 1OA are coupled respectively to ground and to an input of an NPN transistor T_b. The transistor has a current path coupled between ground and the power supply via a load resistor R. When the connectors are connected, current flows into the input of the transistor through the input resistor in device A. This causes the transistor T_b to switch on, and so current passes through the load resistor R in device 10B. These events are practically simultaneous and so making and breaking of the connectors can be detected in both devices simultaneously by detecting the currents, or their effects on the voltage across the resistors R in each device.

As shown, device 10B also has a repeat of the circuit of device 10A, and device 10C has a repeat of the transistor circuit of device 10B. So device 10A could be connected to device 10C or 10B, and device 10B can be connected to device 10A and 10C. In some embodiments the devices can all be like device 10B. In other embodiments, there may be only devices like devices 10A and 10C. Or there may be all three types of devices.

This arrangement uses two connectors which has the advantage that only two connectors are needed therefore guaranteeing identical timing between devices. Its disadvantages include: current flows when devices are connected together; and it is an asymmetric solution, unless two pairs of connectors on each device are provided as shown for device 10B, which adds costs.

In practice, making resistors R larger reduces the current and thus power consumption. This is practical as long as the detector outputs only drive high impedance loads. Pulsing the supply of the driving circuit as in device 10A could help reduce power consumption. The event would then be detected by both devices on the next pulse after separation or the first pulse after contact. Notably, if this pulsing were globally synchronised via other external means, it could also be used to achieve effective segmentation of the communications channel to therefore prevent fragmentation, for example in the time-domain. Such external means could be a radio time signal, global positioning system broadcasts, or a burst of optical or other radiation for example.

The circuit could be inverted using a PNP transistor to make the current consumption mode occur when devices are separated. If two sets of connectors are used per device as in device 1OB, the solution becomes symmetric both from a circuit view-point, and a physical and packaging viewpoint.

Figure 6 shows a three-port solution. Device 1OA and device 10B have the same circuit. A centre pin is connected to ground in both devices. Outer pins are coupled to ground and to the power supply through a load resistor R.

By reversing the orientation of the devices 10A or 10B as shown, the outer ground pin of device 10A is coupled to the load resistor of device 10B and vice versa. Hence current flows through the resistors R in both devices.

This has the advantage that it is a symmetric solution electrically although the physical connectors must still be arranged in a given orientation to guarantee the correct contacts meet. This means that the physical packaging must still be asymmetric.

A disadvantage is that it doesn't guarantee a simultaneous event in both devices as switch bounce can introduce timing errors. Also a current flows when devices are connected together, which implies high power consumption. The symmetry available from this solution is only valid at a circuit level. If identical packaging were used for both devices, wiring between the circuit and packaging contacts would be different for the two devices. This leads to the conclusion that each device must have two sets of contacts, e.g. male and female. This ensures the correct connections are made and it is then up to the user whether device 10A connects into device 10B or device

10B connects into device 10A. Indeed this could be used as a feature to implement two different modes of operation.

If two connector sets are made available, as in Figure 5 device 10B, this solution becomes unnecessary anyway because the two-port solution becomes symmetrical when viewed from a device level perspective. Physical design of the connector can be tailored to guide the correct contacts into connection and to help ensure that the contact/separation is made instantaneously and with minimal bounce. Using male & female contact designs is one way to implement this although so called "androgynous" designs without distinction between male and female may also be suitable. The latter problem could be solved by ensuring that the central connection is guaranteed to break before the other two upon separation, or make last upon connection.

The applications of this invention are extremely extensive as shown by the following examples:

A) Children's toys - Association example: Items of a certain colour, and words indicating that colour could be physically touched together to test correct association. When separated, shaking of one item would make the corresponding correctly paired item identify itself, e.g. flash or beep. B) Children's toys - Remote control example: While building a model, an actuator element could be paired with a controller element before fitting into the model. This would allow children to not only build the model, but also build a working user interface to control it with. Figures 7 and 8 show an example using building bricks. In Figure 7, two bricks 200, 220 are shown stacked together. The same bricks are shown separated in Figure 8. The top brick 200 has a circuit board 210 built in to support the circuitry for the functions shown in Figure 1. Similarly the lower brick 220 has a similar circuit board. Each brick 200, 220 has pegs 240 for engaging other bricks. Some or all of these can be used as connectors for the detector 60. C) Distributed sensors, such as intruder sensors around a property.

D) Medical sensors - Disposable Plaster example: Plasters could be paired with a particular monitoring device before application.

E) Sensors for finding an item - Golf Ball Finder example: By pairing a golf ball with a suitable unit, a particular ball could be located for the duration of the game. If the ball became irretrievable for some reason, a new ball could be paired with the finding unit. Other embodiments are shown in Figures 9 and 10, which may be used in many of the applications already discussed. In Figure 9, a contact switch is used to trigger starting of communication, whether the channel is predetermined or determined according to the detection event. By using lugs such as the pegs 240 shown in Figures 7 and 8, or other mechanisms, the contact switches may be triggered only when the two devices are in a predetermined relative orientation. At step 200, the user moves one of the wireless devices into contact with another device. At step 110 the detector detects the other device. The contact in a given orientation such as by stacking the devices helps ensure the communication is not triggered inadvertently by other movements. At step 240 the transceiver starts communication to the other device based on the detection by the contact, and without further user input other than the moving of the devices into contact. At step 250 the transceiver listens to the other device and pairs with it. This may not be needed if the communication is to be one way, for example from a sensor. At step 160, both devices confirm they are in communication and agree how to continue. As in Figure 2, this step may not be needed if communication is to be one way and the transceiver has only one of a transmitter or a receiver. In Figure 10, as in Figure 2, at step 100, the user moves the wireless device near or in contact with the other device. At step 110, the detector detects the other device. At step 320 the detection causes transceiver switch on without other user input. This enables power to be saved without needing to have other measures, so the device can be kept as simple and low cost as possible. As in Figure 9, at step 240 the transceiver starts communication to the other device based on the detection by the contact, and without further user input other than the moving of the devices into contact. At step 250 the transceiver listens to the other device and pairs with it. At step 160, both devices confirm they are in communication and agree how to continue. Another application for such devices is in tags or tickets, such as those where further monitoring of the tag or ticket for location or validity is warranted, such as flight boarding passes or luggage tags. Tearing the ticket in half can be detected and the event used by both halves as their detection signals. Half of the ticket can be retained by the issuer, and used to communicate with the half retained by the buyer for example when the buyer or their luggage moves to a given monitoring location such as onto the plane. The half retained by the issuer could be coupled to a wide area network of sensors and could communicate the timing or the channel used by the given ticket to all the sensors so that progress of the buyer's half could be tracked or checked at many locations. This can be applied usefully to many tracking applications, particularly those where low power, low cost generic wireless devices, many channels and low set up complexity and minimum user input are sought.

Another application is a monitoring system for goods in a container. Goods that are loaded into the container are swiped or touched with a master device that sits in the container. The synchronisation event initialises the tag and the time event is stored by the master. It is then able to communicate with any device in the container as it knows the timing/channel characteristics of all the tags. Similarly, the master need only activate its receiver when it knows that tags are active which helps save power. This could mean the difference between supplying power externally to containers, or enabling them to run off a battery or a suitable energy scavenging device.

In many applications the devices need to communicate only occasionally. This means that they can be off most of the time to keep power consumption down. As the operating duty cycle of a device (i.e. the period of time that a transceiver is on compared to the amount of time that it is off) goes down, the average power saving of the system goes up. Given a certain amount of data that is to be sent in each cycle, reducing the duty cycle means increasing the off time of the transceivers. In this case message latency increases because on average there is a longer wait before a message can be sent. This means that the initial synchronisation takes longer as well. In many embodiments the devices 10 will be mobile and need a small power supply. For low cost or one time use applications, it is likely that the source of energy for the devices will be unable to supply the peak current or peak power (e.g. 1-5mW) required to actually transmit or receive. For such low power transmissions, the power required to receive is comparable to the power for transmission. This is the case for very small batteries, and will be even more of an issue if using energy scavenging sources such as solar cells. To circumvent this, the transceiver can be powered via some form of energy storage mechanism such as a capacitor. The capacitor can charge relatively slowly from the power limited energy source, and then dump this energy in a short burst to the transceiver when required. This supplies enough current to operate the device but only for short periods of time. As a result, having a low duty cycle protocol can enable smaller cheaper power sources to be used. The power source could in some embodiments be a transponder which obtains enough energy from a received signal to power a brief transmission in response.

In some embodiments the power constraints apply only to one of the pair. An example is mains supply powered home automation devices communicating with mobile devices. In such cases, synchronising one low power mobile device to a mains powered device can involve the mobile device selecting a channel based on the movement, so that it need not be preprogrammed or have a predetermined network address and the mains supplied transceiver can operate continuously to scan time slots until synchronisation has occurred. At this point, time slots can be agreed upon so that they can then operate in a pulsed mode safe in the knowledge that both devices will be on at the same time.

The same mobile device can be arranged to pair to other mobile devices instead or as well, by moving the pair into contact or proximity as described above, even where neither device has enough energy to keep a transceiver on for long enough to scan timeslots or frequencies or any type of channels. A detection event enables the setting up of a channel by synchronising the devices without having to transmit or receive for lengthy periods of time initially to scan channels to discover each other and achieve synchronisation. Such synchronising is occurring before exchanging messages and so can be regarded as a low level pairing, distinct from the subsequent higher level pairing process of exchanging messages to discover details such as network characteristics and bandwidth capabilities.

The devices can continue to operate in a low duty cycle TDMA manner or can change to other multiplex types, or increase the duty cycle. By continuing to operate in this pulsed manner, it is possible to have multiple networks operating within the same area of influence but using different TDMA time slots. This can apply to any form of physical layer such as ultrasound, inductive coupling and infra-red.

Embodiments of the invention may have controllers 40 implemented using a conventional general purpose digital computer or microprocessor programmed according to the teachings of the present specification, as will be apparent to those skilled in computers. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in software.

Embodiments may also be implemented by the preparation of application specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art.

Embodiments may also be implemented by a computer program product on a storage medium including instructions which can be used to program a computer to perform a process of the invention. The storage medium can include, but is not limited to, any type of disk including floppy disks, optical discs, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions. The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Many alternatives, modifications, and variations will be apparent to those skilled in the art within the scope of the claims.

In the present specification and claims the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Further, the word "comprising" does not exclude the presence of other elements or steps than those listed.

The inclusion of reference signs in parentheses in the claims is intended to aid understanding and is not intended to be limiting.

Claims

1. A wireless device (10) able to communicate with one or more other wireless devices, the device having a transceiver (20) and a device detector (60) to detect the presence of a given one of the other wireless devices without using the transceiver (20), the wireless device (10) being arranged to use the detection to determine a channel for the transceiver (20) to start communication with the given other wireless device, and to start the communication.

2. The wireless device (10) of claim 1 , the detector (60) being arranged to co-operate with the given other wireless device to produce a detection signal in both devices, the detection signals having related timings, and the wireless device (10) being arranged to synchronise the transceiver (20) to the other wireless device according to a timing of the detection signal of the wireless device (10).

3. The wireless device (10) of claim 1 or 2, the transceiver (20) being arranged to listen for transmissions only after the detector (60) has produced the detection signal.

4. The wireless device (10) of claim 3, the channels being time slots, and the channel determination involving selecting a time slot at a time or times referenced in a predetermined way to the detection signal.

5. The wireless device (10) of claim 4, the transceiver (20) using the same frequency for initiating communication as other wireless devices, and using a duty cycle for the communication which is lower than 1/n where n is the total number of pairs able to transmit.

6. The wireless device (10) of any preceding claim, the detector (60) having part of a circuit (R, T_b), arranged such that the other wireless device can complete the circuit, and the detector (60) being arranged to detect completion or breaking of the circuit (R, T_b).

7. The wireless device (10) of claim 6, the circuit (R, T_b) being any one or more of: an electrically conductive path, an optical path, a magnetic flux path, an acoustic or vibration path, a fluidic path, a mechanical linkage path, and a radiation path.

8. The wireless device (10) of any preceding claim, arranged to communicate without using a predetermined network address, and without being pre-programmed to communicate with a predetermined other wireless device.

9. The wireless device (10) of any preceding claim, the detector (60) comprising a switch (T_b) arranged to cause power up of the transceiver (20) after physical contact of the device (10) with the other wireless device is broken off.

10. The wireless device (10) of any preceding claim, the transceiver (20) having a range of less than 20m, or a power consumption of less than 1OmW when transmitting or receiving.

11. The wireless device (10) of any preceding claim, arranged to communicate with more than one other wireless device.

12. A network (85) having a plurality of the wireless devices (10) of any preceding claim.

13. The network of claim 12, at least some of the wireless devices (10) having any one or more of: a sensor, an output device, and a computing device and the network being arranged to communicate any one or more of: sensing data from the sensors to a monitoring point, commands to the output devices at different locations, and data to or from the computing device.

14. A method of setting up a network of two or more wireless devices (10), each having a transceiver (20) and a device detector (60) to detect the presence of another of the wireless devices (10), and being arranged to use the detection to determine a wireless channel, and start communication with the detected wireless device (10) using the channel, the method having the steps of initiating wireless communication with the other wireless device (10) using the transceiver (20), by moving either wireless device (10) into or out of the presence of the other wireless device (10) to cause the detection, and to cause the channel to be selected, and to cause the communication between the wireless devices (10) to start.

15. The method of claim 14, the movement causing the wireless devices (10) to produce detection signals in both devices, the detection signals having related timings, and the same channel being determined in both devices (10) according to the timing of the detection signals.

16. A wireless device (10) able to communicate with one or more other wireless devices, the device (10) having a transceiver and a contact detector (240, R, T_b), to detect physical contact with a given one of the other wireless devices in one or more predetermined relative orientations, the wireless device (10) being arranged to use the detection to start communication (240) and pair with the detected wireless device.

17. A wireless device (10) able to communicate with one or more other wireless devices, the device (10) having a transceiver (20) and a device detector (60) to detect the presence of a given one of the other wireless devices without using the transceiver (20), the wireless device (10) being arranged to use the detection to switch on the transceiver (20), and to start communication with the given other wireless device without user input.