WO2001092910A2

WO2001092910A2 - Method and apparatus for determinig the location of a plurality of users

Info

Publication number: WO2001092910A2
Application number: PCT/GB2001/002405
Authority: WO
Inventors: Nigel John Walker; Brian Whelan
Original assignee: Nigel John Walker; Brian Whelan
Priority date: 2000-05-31
Filing date: 2001-05-31
Publication date: 2001-12-06
Also published as: AU2001262496A1; WO2001092910A3; GB0013295D0

Abstract

A method of determining the locations of a plurality of users within a predetermined space. The method comprising allocating an electronic tag having an identifier to each user, each tag being responsive to a predetermined interrogation signal to transmit a response signal from which the location of the tag within the predetermined space can be determined. The electronic tag identifier is associated with the user on allocation of said electronic tag, such that it is assumed that the location of an electronic tag corresponds to the location of the associated user. An interrogation signal is transmitted within the predetermined space and response signals are detected, to determine the location of users from the response signals.

Description

USER LOCATION

The present invention relates to a method and apparatus for determining the location of a plurality of users within a predetermined space.

A passenger travelling on an aircraft is conventionally issued with a paper ticket. This ticket is. presented by the passenger to a member of airline staff at a check-in desk, any luggage that is to travel in the hold is handed over and the customer is issued with a boarding pass specifying a seat number and allowing access to an aircraft. It may be that at the time of check-in, the number of the departure-gate from which the flight is to depart will not be known or alternatively only a provisional gate number will be printed on the boarding pass. In these cases, the passenger will be asked to look -at display boards to ascertain the correct gate number or alternatively to listen for announcements of a gate number for their particular flight. Such a system has the disadvantage that some passengers will be on-edge, looking out for the gate number while others may forget to do so, and therefore arrive at the departure gate late. Boarding time may also not be known with certainty at the time of check-in and again passengers are asked to look at displays or listen for announcements, resulting in the problems described above.

A passenger^' who does not arrive at the departure gate by a specified time can cause inconvenience to all other passengers while airline staff locate the passenger and bring him to the gate. If the passenger can not be found, the passenger's luggage must be unloaded from the hold (for security reasons), delaying the flight still further. Flight delays caused in this way are not only a source of inϊtation to other passengers, but cause considerable cost to the airline who will have to pay significant extra charges to the airport if their take off "slot" is missed in this way.

Furthermore, these problems worsen if a flight is delayed, or departure gate number is unexpectedly changed. In this case all passengers have to be informed by way of announcements or display messages. If these are not observed by all passengers further problems are created. It is an object of the present invention to obviate or mitigate one of more of the problems outlined above.

According to a first aspect of the present invention there is provided a method of determining the locations of a plurality of users within a predetermined space, comprising allocating an electronic tag having an identifier to each user, each tag being responsive to a predetermined interrogation signal to transmit a response signal from which the location of the tag within the predetermined space can be determined, associating the electronic tag identifier with the user on allocation of said electronic tag, such that it is assumed that the location of an electronic tag corresponds to the location of the associated user, transmitting an interrogation signal within the predetermined space, detecting response signals, and determining the location of users from the response signals.

Response signals may be detected by a plurality of receivers distributed within the predetermined space, each receiver being adapted to detect response signals transmitted by tags within a predetermined range of that receiver. The predetermined ranges of adjacent receivers may overlap, and the location of a user may be detennined by correlating the detection of a response signal by a plurality of receivers.

Preferably, each tag is responsive to two interrogation signals, and more preferably, each tag is responsive to a short range RFID interrogation signal and a long range RFID interrogation signal.

Users may be alerted to detection of an interrogation signal by an associated electronic tag. Users may be altered by means of a buzzer, light, or trembler incorporated in the associated electronic tag. A display may show information received with the detected interrogation signal. An indication may be provided if a user passes a predetermined boundary within the predetermined space. An indication may also be provided of a distance or transit time between a user's location and a predetermined location within the predetermined space. Directions for transit from a user's location to a predetermined point may be delivered to the user's associated tag.

Possession of an associated tag may allow access to a predetermined space. A user may surrender the associated tag upon gaining access to the predetermined space. Information may be transmitted to a user via the associated tag, the transmitted information being selected on the basis of a stored profile for that user and/or the current location of the user.

The predetermined space may comprise one or a plurality of airports through which a user may pass using a single electronic tag. Alternatively the predetermined space may be a retail outlet or a theme park.

The predetermined space may be an airport within which there is at least one retail outlet, and information may be transmitted to a user via the associated tag, the transmitted information including information intended to encourage retail activity until it is desirable for the user to start departure procedures, and thereafter information intended to encourage the user to start the departure procedures.

According to a second aspect of the present mvention, there is provided a method for encouraging efficient use of retail facilities in airports, comprising allocating an electronic tag to each passenger intending to complete departure procedures at the airport, each tag including means for receiving information of relevance to the passenger to whom the tag has been allocated, transmitting information to each tag intended to encourage retail activity by the respective passenger until it is desirable for that passenger to start departure procedures, and thereafter transmitting information intended to encourage the respective passenger to start departure procedures. According to a third aspect of the present invention, there is provided an apparatus for determining the location of users within a predetermined space, comprising a plurality of electronic tags each having an identifier for distribution to users, means for transmitting an interrogation signal to electronic tags within the predetermined space, the tags being responsive to predetermined interrogation signals to transmit a response signal, means for detecting response signals transmitted by electronic tags within the predetermined space, and means for determining the location of tags within the predetermined space from detected response signals.

According to a fourth aspect of the present invention, there is provided a computer program for controlling a computer to carry out a method as set out above.

According to a fifth aspect of the present invention, there is provided an electronic tag for use in a method as set out above, comprising means for storing an identifier, means for receiving a plurality of distinct interrogation signals, and means for responding to a received interrogation signal.

Preferably, the plurality of distinct interrogation signals comprise a long range RFID interrogation signal and a short range RFID interrogation signal. The electronic tag may further comprise a microprocessor connected to a memory unit and display means.

According to a sixth aspect of the present invention, there is provided an electronic tag comprising a passive circuit which in use is powered by a predetermined radio frequency signal transmitted from a remote source, and an active circuit incorporating a power source for transmitting data from the tag, the active circuit being enabled by the passive circuit upon detection of the predetermined radio frequency signal and switched off to conserve the power source unless enabled by the passive circuit.

According to a seventh aspect of the present invention, there is provided an electronic tag for allocation to a passenger in an airport to serve as a boarding pass for the passenger to whom it is allocated, comprising means for receiving transmitted information related to the intended departure of the respective passenger.

The term predetermined space is hereinafter used to mean a controlled enclosed space in which the location of a.plurality of users is to be determined, for example an airport or any other space to which users are given access

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of an electronic tag used in a location system according to the present invention;

Figure 2 is a schematic illustration of a transceiver suitable for use in a location system according to the present invention;

Figure 3 is an schematic illustration of how a plurality of transceivers are used in a location system according to the present invention;

Figure 4 is a schematic illustration of a possible spacing between transceivers;

Figure 5 is a schematic illustration of a method of locating an electronic tag using a plurality of transceivers;

Figure 6 is a schematic illustration showing how transceivers may be arranged to locate users on a grid of pathways; and

Figure 7 is a schematic illustration of a method for fitting transceivers in a building employing the present invention.

Referring to Figure 1 , there is illustrated a block diagram of an electronic tag. .The electronic tag is issued to a user whose location is to be tracked within a predetermined space. The electronic tag comprises an aerial 1 connected to a radio receiver and transmitter unit 2, in communication with a microprocessor 3. The microprocessor 3 is provided with a memory unit 4 for storing data, including a unique identifier for the electronic tag. In use, a suitable transceiver may communicate with the electronic tag via the aerial 1. The microprocessor is further connected to an electronic compass 5, an input device 6 such as a small keyboard and a number of output devices 7. Suitable output devices include a buzzer, trembler, Liquid Crystal Display (LCD) screen or a visual indicator such as a Light Emitting Diode (LED). The LCD screen comprises two lines of 16 character text, and the screen is provided with a backlight to aid visibility.

The electronic tag is powered by a rechargeable battery 8 which is in communication with the microprocessor 3. The microprocessor 3 constantly monitors charge status of the rechargeable battery 8, and reports a low battery status to the user by means of an output device 7. Power is supplied from the rechargeable battery 8 to the microprocessor 3 and to the radio receiver and transmitter unit 2. A suitable transceiver communicates with the aerial 1 to request battery charge information which is then supplied to the radio receiver and transmitter unit 2 by the microprocessor 3 and transmitted by means of radio signals to the transceiver.

Referring now to Figure 2, there is illustrated a block diagram of a transceiver for communication with the electronic tag of Figure 1. The general architecture of the transceiver can be seen to be similar to that of the electronic tag of Figure 1. The transceiver comprises an aerial 9 connected to a radio receiver and transmitter unit 10. The radio receiver and transmitter unit is further connected to a microprocessor 11. The microprocessor 11 is connected to a network interface 12 to allow communication with another transceiver or a computer control system. The network interface 12 may use a dedicated hard wired connection or a conventional computer network arrangement based on a Local Area Network (LAN) topology such as Ethernet. Alternatively, a digital wireless network arrangement, such as one based upon Digital Enhanced Cordless Telecommunications (DECT) technology may be used. The network connects each transceiver to other transceivers situated within the predetermined space and additionally, connects the transceivers to a central computer control system. Each transceiver has a range in the order of 40 metres. Each transceiver is mounted within a small box, the box being manufactured to an appropriate standard.

The microprocessor 11 and the receiver and transmitter unit 10 are powered by a power control unit 13 comprising a rechargeable battery. The power control unit is powered by a mains power supply 14. The rechargeable battery provides a failsafe solution in the event of a mains power failure.

Referring now to figure 3, a predetermined space 15 is provided with a plurality of transceivers 16 each operating over a range depicted by a dotted circle 17. It can therefore be seen that the plurality of transceivers 16 shown in figure 3 provide coverage over the predetermined space 15.

A typical spacing between three transceivers A, B, and C is illustrated in figure 4. It can be seen that two tranceivers A, B are spaced apart at a distance r in a first direction where r is the radius of the circle defining the range of the transceivers A,B. In a second direction, it can be seen that the distance between transceiver C and transceivers A,B is 0.866r. The spacing illustrated allows an effective coverage of the predetermined space to be achieved while keeping the number of transmitters required within a reasonable limit.

Referring now to figure 5, there are illustrated a plurality of transceivers 16, each having a range depicted by a circle 17. An area 18 is shaded, being within the range of each of the transceivers a, b, c, d and e but no other transceiver. By use of a suitable control system, it is possible to determine that any electronic tag in comimrmcation with each of transceivers a, b, c, d, and e but no other transceiver, must be within the area 18.

Communication between a transceiver 16 and an electronic tag is as follows. A transceiver will send an interrogation signal addressed to a predetermined tag. All electronic tags within range will detect this message. If the interrogation signal is addressed to a predetermined electronic tag, the microprocessor 3 _, of that predetermined electronic tag switches the radio receiver and transmitter 2 to transmit and sends a response message to adjacent transceivers 15. This allows each transceiver detecting the response message to confirm that the predetermined electronic tag is within its range.

To locate a predetermined tag, all transceivers within the predetermined space send an interrogation signal to the predetermined tag. The transceivers receiving a response from the predetermined tag are correlated to determine a set of transceivers within range of the predetermined tag, and thereby determine the location of the predetermined tag.

Alternatively, a single interrogation signal may be sent out across the predetermined space from a single transceiver. The response of the tag to such a message may then be detected by correlating the or each transceiver receiving a response to the interrogation signal as described above.

In a preferred embodiment of the invention, an alternative location algorithm is used. Each transceiver determines which tags are within its range at a predetermined time. This information is relayed to the computer control system and the current location of each tag at that predetermined time is stored.

Determination of which tags are within range of the transceiver is carried out as follows. A transceiver will send out an interrogation signal addressed to all tags. If only one response message is received the transceiver will determine that only one tag is within its range, and will determine the identifier of that tag from the response message. If a plurality of tags are within range of the transceiver, a number of response messages will be transmitted simultaneously by in-range tags, and a signal containing interference will be detected by the transceiver. The transceiver will then send a message addressed only^' to half of the tags. For example, if each tag has a forty-eight bit address as is often used, an interrogation signal is transmitted only to tags having addresses in the lower half of this address range. If only one responds it is identified and the procedure is repeated by sending a further interrogation signal, this time addressed to tags having addresses in the upper half of the address range.

It is likely that splitting the address range in half will still result in interference and the procedure is therefore repeated by splitting each half of the address range in half again, and so on, until each tag sends a signal to the transceiver without interference from any other tags transmitting simultaneously. This approach is a well known search algorithm known as "binary search" or "binary chop".

The central record of the last known location of a tag is used when it is necessary to locate a tag. A look up table is consulted to determine the last known location of the tag, and an interrogation signal is sent out to that tag as described above by the transceivers which were last in communication with the tag. If the tag can not be found within range of those transceivers, adjacent transceivers are instructed to send interrogation messages and the procedure continues until the tag is located.

By storing a look up table and using this as a starting point for the location process, the number of interrogation messages is reduced as is the number of instructions travelling between the central computer and the transceivers.

A suitable map may be stored by a computer system connected to each of the transceivers to relate communication between a predetermined electronic tag and a predetermined set of transceivers to a location within the predetermined space. Communication time between a transceiver and an electronic tag takes in the order of 1 second, although target time for a single unidirectional message is in the order of 100ms. Ideally, each electronic tag will be within range of at least two transceivers at a given time.

National and international licensing authorities restrict frequencies at which communications between the transceiver and the electronic tag may operate. Communications can conveniently use long range radio frequency identification (RFID) signals, with a number of suitable frequencies being available.

Referring now to figure 6, it can be seen that the number of transceivers 18 required to obtain coverage of the predetermined space can be reduced if users are restricted to pathways 19 with the space. For example, if the blocks 20 represent areas that are inaccessible to the public (for example restricted areas) it is not necessary to accurately locate a user within an area 20 thereby reducing the required resolution, and in turn the number of transceivers 16 required.

The transceivers may be conveniently housed in a roof space of the predetermined space, and such a configuration is illustrated in figure 7. Here transceivers 16 are attached to a ceiling 21 which is situated below a roof 22 of a building. It can be seen from Figure 6 that the range of the transceivers 16 is such that adequate coverage is provided to reach a floor 23 of the building.

It will be apparent to those skilled in the art that the transceivers mentioned above may be replaced by separate transmitters and receivers.

The electronic tag is designed in such a way as to balance battery life, display capability and response time. In order to ensure that the necessary response time targets are met, it will be necessary for the radio receiver and transmitter unit of the electronic tag to be powered for much of the time so that the electronic tag can respond promptly .to any messages addressed to it. The LCD display is designed to consume little battery power.

Active and passive RFID tags are both known. Passive tags contain no power source, and on receiving a radio^" frequency (RF) signal, the tag uses power from this signal to generate a response. Such tags are advantageous in that there is no requirement for a power source within the tag. However, the power obtained from the RF signal is sufficient only to transmit over a relatively short distance, thereby requiring an active tag having a built in power source for longer range RFID devices. In a preferred embodiment of the present invention, each tag is a hybrid tag comprising a passive receiver circuit, which in turn activates an active transmitter circuit having a power source. Receipt of an interrogation signal by the passive circuit will cause the passive circuit to activate the active circuit, thereby facilitating the transmission of the response message over a longer range. As the active circuit is switched off unless the interrogation signal is received, battery power is conserved.

In an alternative embodiment of the invention, each tag comprises an active transceiver, chosen such that its power consumption is as low as possible while obtaining adequate range.

Therefore, battery power is consumed only when an interrogation message has been received, requiring that a response message is generated.

Electronic tag size is also an important factor in its design. Size is related to the requirements of battery power, as the battery pack is likely to take up a considerable fraction of the volume of the electronic tag. In particular, the battery is likely to influence minimum thickness and also flexibility of the electronic tag. The electronic tag needs to be large enough so as not to be lost, but small enough and light enough so as to be convenient to carry.

The electronic tag is manufactured using an Application Specific Integrated Circuit (ASIC) in order to obtain optimal size and performance. Optimum size may be credit card size, with a thickness of about 1mm being possible if suitable battery technology is used. If a larger size of electronic tag is preferable, for example in order to reduce the risk of loss of .an electronic tag, then an ASIC may still be used so as to reduce production costs and increase reliability.

The electronic tag may be provided with a vibration sensor to sense movement or breathing of a passenger. Failure to sense movement would imply that the electronic tag had been discarded or the passenger had stopped breathing. An application using the system as described above within an airport will now be described. A user reports to an airline check-in desk in the normal way, and presents a valid ticket for a flight to a member of airline staff. The validity of the ticket is then checked and other formalities completed. The user is issued with an electronic tag of the form described above. In an alternative embodiment of the present invention the electronic tag is provided with attachment means to hold a conventional paper electronic tag. In issuing an electronic tag, the airline and airport computer system stores a link between the identifier of the electronic tag and an identifier of the user. Additionally, information about the passenger is loaded into the memory unit of the electronic tag in the form of a user profile at check-in, and the status of the passenger, i.e. checked-in, is also loaded into the memory. The memory of the electronic tag may also store a photograph of the passenger to whom the electronic tag was issued. Such a photograph could either be obtained using a digital camera at check-in or by scanning a photograph from the passenger's passport. Luggage may also be photographed to allow easier location of the luggage if it should be lost. The electronic tag is formed such that the user is not able to modify the program code thereon.

The user, having checlced-in, will have been allocated a seat number on board the aircraft and will have been told the number of a departure gate to which he should report. The user is then free to roam about the airport until it is time for the flight to be called. The record of which user has which electronic tag held by the system will mean that the system can be used to determine the location of a particular user, using a mechanism as described with reference to figure 5. If a passenger does not arrive at the correct departure gate promptly, the system can determine the passenger's location, allowing airport staff to find the missing passenger quickly and escort him to the departure gate.

In a preferred embodiment of the present invention, the output devices 8 of the electronic tag of figure 1 will allow a transceiver to communicate to a passenger the fact that he is late arriving at the departure gate. Such a communication may involve a trembler or a flashing light. The use of the trembler is particularly advantageous for use with passengers who are visually impaired or hard of hearing. More preferably, a message is displayed on the LCD screen telling the passenger to make his way to the departure gate immediately. A buzzer could also be used, which would alert the passenger that he was late, and would also attract the attention of airport staff looking for the passenger.

Dispatch of messages to a particular electronic tag or group of electronic tags (e.g. those for all passengers on a given flight) can be controlled by a computer system connected to the transceivers situated about the airport. The computer runs appropriate software to allow communication with the transceivers. The software allows a list of electronic tags issued, together with the identity of the passengers to whom they have been issued, to be viewed. The software allows an electronic tag to be selected from a drop-down list showing the unique identifier of the electronic tag together with an appropriate text string to allow easy identification of the user. When an electronic tag is selected in this way, a message may be entered in an appropriate dialog box for transmission to the selected electronic tag. Similarly, options for transmitting a tremble or bleep may be selected.

Selection of an electronic tag from the drop-down list also allows the current location of the electronic tag within the airport to be displayed. This location is derived from the transceivers with which the electronic tag is in communication using a method as described above.

The control software described above would also be provided with functionality to interface, with existing airport and airline computer systems. This would allow cross checking with a list of passengers who have tickets for a given flight, and cross reference to passenger history records showing routes travelled and any other pertinent details such as a user profile.

The electronic compass 7 of the electronic tag may direct the passenger to the correct departure gate. Such a system would operate using a map of the area stored in a data memory 4 of the electronic tag. Signals from the compass 7, in combination with the map will allow arrows to be displayed on the LCD screen showing a passenger the way in which he should proceed to the correct departure gate which the system will have identified on the map.

Alternatively, the system may print messages oh the LCD display such as "follow the RED line on the floor". If the passenger takes a wrong turning the system can detect this using the location system, described above and inform the passenger by means of a trembler signal, a flashing light, or an audio signal and give correcting directions by means of the LCD display.

The location system can also be used to detect if a passenger has left the airport or had remained motionless for a long time, particularly if a flight has been called and the passenger is not at the correct departure gate. The location monitoring system can also be used to monitor passengers who are considered to be a security risk

A Frequency Modulation (FM) radio receiver may be included in the electronic tag of figure 1. In this embodiment a headphone socket is provided such that a user can connect headphones to the electronic tag to listen to radio as they wait for their flight. This feature may make use of the user profile stored on the card to periodically interrupt the radio programme and play pre-recorded advertisements. The user profile may be used to target the advertisements to a particular sector of passengers. For example children would not be broadcast advertisements relating to alcohol or tobacco. The radio could be provided digitally using stored music and advertisements,' News could be purchased from a commercial news broadcaster and automatically updated on the digital storage system.

The electronic tag of figure 1 displays departure gate and departure time information to the passenger by means of the LCD display. The display can also show flight number and destination information. The electronic tag is also used to inform a passenger of the latest status of their flight. For example a change of departure gate or delayed boarding may be communicated to the passenger by means of an audio indicator and a message displayed on the LCD screen. The electronic tag could also be used to remind the passenger that the flight has started boarding, or that boarding is about to close, before the passenger is late.

The system according to the present invention may additionally include capabilities to allow an electronic tag to be read at short range. In such an embodiment the electronic tag of figure 1 may further include a second aerial to for use with a short range RFID transceiver. An electronic tag placed within a small distance of an appropriate reader can then be read and identified by means of the identifier stored within the memory of the electronic tag. Such a feature is used when a passenger passes through passport control or customs to identify the passenger as they pass through the checkpoint. The fact that they have passed through the checkpoint is loaded into the memory of the electronic tag so as to update the status of the passenger. This status update is also registered with the system control software to allow an accurate record of passenger status to be held by the control ^" computer system. The invention would therefore obviate the need for staff to manually update lists based upon paper boarding pass stubs collected when passengers board the aircraft.

Identification of a tag placed adjacent the reader by means of short range RFID uses the binary search method described above for the long range RFID location system. However, due to the relatively short range over which the short range system functions it is likely that only one or two interactions of the process will be required before a tag is conclusively identified.

Signals used by the short range RFID system are similar to those used for the long range system although different frequencies may be used in some applications. It is also likely that the short range signal will be transmitted at a lower power level as it will travel over a considerably shorter distance.

A short range RFID reader is housed in a box having approximate dimensions 300mmxl50mmxl00mm and has a maximum read range in the order of 20cm. This range allows an electronic tag to be conveniently read without any ambiguity with respect to adjacent electronic tags. There are several frequencies in use for short range RFID applications. A number of these frequencies may be used in a system according to the present invention. When an electromc tag is read, the reader will display the identifier of the electronic tag together with a text string which may conveniently be the name of the passenger. A short range RFID reader need not give any location data because it can only read electronic tags proximate the reader. The short range RFID reader can also read a photograph of the passenger stored in the memory of the electronic tag, thereby allowing a member of airport staff to verify that the passenger presenting the electronic tag is the one to whom the electronic tag was originally issued.

A short range RFID reader may also be provided in a portable case such that it may be carried by airport staff who may check the validity of a passenger's electronic tag.

The short range RFID system may also be used to control access to first class or VIP lounges. Here, the class of travel of the passenger, and any "frequent flyer" club membership details are stored in the memory of the electronic tag. The electronic tag is presented to a short range RFID reader outside a lounge and the system then ascertains whether or not the information on the card is such that the passenger is allowed access to the lounge.

The electronic tag can also act as a payment means. If a flight is delayed an airline may wish to offer all passengers a complimentary meal up to a predetermined value. Credit to this predetermined value is loaded in the memory of the electronic tag remotely from a transceiver. A customer then presents the card at a retail outlet as payment or part payment for goods purchased.

The electronic tag can also be used as a payment means in airport shops. In this case, the system links the electronic tag to a credit or debit card of the user such that the user may pay for goods using his electronic tag with the transactions appearing on his credit card statement in the normal way. The electronic tag may store the passengers name and address within the user profile so that large goods can be paid for using the electronic tag, and automatically dispatched to the address stored on the electronic tag. By using the electronic tag as a payment means in this way useful marketing information can be collected so as to allow the airport to target appropriate advertising to the user. The information identifying goods bought may also be stored by a central computer system as part of the user's profile for future marketing use.

The location system provided by the present invention may also be used to entice a passenger into a retail outlet. This is particularly effective when combined with information from the user profile. For example, a passenger who is known to have bought red wine in the past can be sent a message through his electronic tag informing him of a special offer on red wine. Such a feature would be particularly useful if the message was sent while the passenger was near the duty free shop.

A passenger approaching a coffee shop can use the keyboard provided on the pass to order food, and then follow directions provided by the electronic tag to collect the items ordered, the cost being charged to the electronic tag as previously described.

The location system may be combined with data stored by the central computer system to estimate the travelling time between a current location and a predetermined point. Such a system will allow a passenger to be notified that he is due at the departure gate in adequate time for him to arrive at the departure gate without being late.

A passenger may use the electronic tag to determine the location of another passenger within the airport. This is particularly useful for a parent in locating a child who has wondered off. It may be desirable to add security features to the system such that a passenger can only determine the location of passengers with whom they are travelling. It is also possible to allow passengers to send messages to one another by means of the electronic tags using a mechanism such as Short Message Service (SMS) messages. Electronic tags will be issued to passengers at a check-in desk and therefore each check-in desk will require a programming dispenser to hold the electronic tags in a charging cassette, so as to ensure that the battery is fully charged. When a passenger is issued with an electronic tag, the airline computer system, interfaced to the programming dispenser, supplies information that is to be written onto the card. This information includes passenger details, flight details and departure gate and boarding time information together with other information as previously described. The programming dispenser then issues the card and it is handed to the passenger.

The programming dispenser could be adapted to allow for an automatic check-in option whereby a passenger would insert their ticket into a machine, the ticket would be read and an appropriately programmed electronic tag issued.

An electronic tag receiver collects electronic tags as passengers board an aircraft. On receiving an electronic tag the tag is verified using the short range RFID system described above. Information about a passenger is deleted from the memory of the electronic tag, and a small ticket is printed informing airline cabin crew of a seat to which the passenger should be directed. The electronic tag receiver also charges electronic tags once they have been received.

A large number of electronic tags will be issued and these will need to be transported about the airport. This can be conveniently achieved by the provision of specially adapted trolleys to carry the electronic tags.

If battery life is sufficient, a passenger travelling on a long haul flight from a first airport to a second airport, passing through an intermediate airport can retain the electronic tag when they board the plane. On arrival at the intermediate airport the electronic tag is identified by the transceiver system at that airport and the passenger is presented with departure information using the LCD screen. Such a use of the electronic tags requires that the first and intermediate airports adopt compatible systems. A frequent flyer passenger can retain a particular electronic tag at all times. It is necessary to provide the passenger with means to charge the electronic tag and this can be conveniently achieved using a conventional personal computer and an appropriate adapter. The passenger can book a flight over the Internet, personal details are read from the electronic tag, and the electronic tag is programmed by the adapter to act as a ticket, holding flight details. When the passenger arrives at the airport, the electronic tag can then be used either as a ticket at a manual or automatic check-in point or more preferably a transceiver can detect the arrival of the passenger in the airport, send a message detailing departure gate and time information to the electronic tag, and inform the passenger where he should take any hold baggage. The electronic tag can also allow the passenger to select his seat on the aircraft by means of the LCD screen and keyboard, and confirm the seat number to the passenger using the LCD screen. Thus there is no need for the passenger to undergo a check-in process, and the passenger may proceed directly to the VIP lounge.

The electronic tag can also allow access to information services such as Internet access within the airport. For example, an airline may wish to offer all business class passengers free Internet access. In such a system the electronic tag would be presented to an RFID reader and the passenger would then be allowed to access the Internet.

Luggage tags may take a similar format to the electronic tags described above. This would allow location of luggage to be accurately determined using a method as described above. Additionally, if a frequent flyer has an electronic tag at the time that luggage is collected from the carousel, the passenger's electronic tag can be caused to bleep, tremble or flash as soon as the passenger's luggage bearing a luggage tag having a predetermined identifier arrives on the carousel using an RFID messaging system between electronic tags.

Electronic tags similar to those described above may be issued to airport and airline staff. The electronic tags could then be used to allow staff access to restricted areas. Additionally, the electronic tags could be used to locate a member of staff within the airport, or to allow staff to obtain meals or other goods from airport retail outlets at a discount using the electronic tag as an identity card.

Although the above description relates to electronic tags for passengers within an airport, it will be clear that the invention need not be limited to this application but is instead widely applicable in a number of different fields. These include, for example, a large scale retail outlet where it may be desired to determine a customer's location within the retail outlet. In such an application a user obtains a tag on entering the retail outlet, and as the location of the user is tracked within the retail outlet appropriate advertising, special offer or other information would be forwarded to the customer's electronic tag based upon a stored user profile.

Furthermore, the invention is equally applicable in a theme park. In such an application a user obtains a tag on admission to the theme park. It is then possible to track the user's location within the theme park and monitor usage of different areas of the park so as to determine currently popular attractions. Additionally, it is possible to transmit information to the tag to encourage the user to enter a retail outlet to buy souvenirs or to enter a eating place for a^' meal. It is possible for information to be transmitted to the tag to inform a user of current queue times for particularly popular attractions, so as to balance users in different parts of the park. For example, if a user approaches a roller coaster having a long queue, a message may be supplied informing the user that another roller coaster currently has only a short queue thereby balancing users between attractions, and reducing queue times which will enhance the enjoyment of the user.

It will be appreciated that the invention may be applied to a number of different fields, in addition to those set out above.

Claims

1. A method of determining the locations of a plurality of users within a predetermined space, comprising allocating an electronic tag having an identifier to each user, each tag being responsive to a predetermined interrogation signal to transmit a response signal from which the location of the tag within the predetermined space can be determined, associating the electronic tag identifier with the user on allocation of said electronic tag, such that it is assumed that the location of an electronic tag corresponds to the location of the associated user, transmitting an interrogation signal within the predetermined space, detecting response signals, and determining the location of users from the response signals.

2. A method according to claim 1, wherein response signals are detected by a plurality of receivers distributed within the predetermined space, each receiver being adapted to detect response signals transmitted by tags within a predetermined range of that receiver.

3. A method according to claim 2, wherein the predetermined ranges of adjacent receivers overlap, and the location of a user is determined by correlating the detection of a response signal by a plurality of receivers.

4. A method according to any one of claims 1, 2 or 3, wherein each tag is responsive to two interrogation signals.

5. A method according to claim 4, wherein each tag is responsive to a long range RFID interrogation signal and a short range RFID interrogation signal.

6. A method according to any preceding claim, wherein users are alerted to detection of an interrogation signal by an associated electronic tag.

7. A method according to claim 6, wherein users are altered by means of a buzzer, light, or trembler incorporated in the associated electronic tag.

8. A method according to claim 6 or 7, wherein users are alerted by means of a display showing information received with the detected interrogation signal.

9. A method according to any preceding claim, wherein an indication is provided if a user passes a predetermined boundary within the predetermined space.

10. A method according to any preceding claim, wherein an indication is provided of a distance between a user's location and a predetermined location within the predetermined space.

11. A method according to any preceding claim, wherein an indication is provided of a transit time from a user's location to a predetermined location within the predetermined space.

12. A method according to any preceding claim, wherein directions for transit from a user's location to a predetermined point are delivered to the user's associated tag.

13. A method according to any preceding claim, wherein possession of an associated tag allows access to a predetermined area.

14. A method according to claim 13, wherein a user surrenders the associated tag upon gaining access to the predetermined area.

15. A method according to any preceding claim, wherein the predetermined space comprises a plurality of airports through which a user may pass using a single electronic tag.

16. A method according to any one of claims 1 tol4, wherein the predetermined space is an airport, a retail outlet or a theme park.

17. A method according to any preceding claim, wherein information is transmitted to a user via the associated tag, the transmitted information being selected on the basis of a stored profile for that user and/or the current location of the user.

18. A method according to any one of claims 1 to 14, wherein the predetermined space is an airport within which there is at least one retail outlet, and information is transmitted to a user via the associated tag, the transmitted information including information intended to encourage retail activity until it is desirable for the user to start departure procedures, and thereafter information intended to encourage the user to start the departure procedures.

19. A method for encouraging efficient use of retail facilities in airports, comprising allocating an electronic tag to each passenger intending to complete departure procedures at the airport, each tag including means for receiving information of relevance to the passenger to whom the tag has been allocated, transmitting information to each tag intended to encourage retail activity by the respective passenger until it is desirable for that passenger to start departure procedures, and thereafter transmitting information intended to encourage the respective passenger to start departure procedures.

20. An apparatus for determining the location of users within a predetermined space, comprising a plurality of electronic tags each having an identifier for distribution to users, means for transmitting an interrogation signal to electronic tags within the predetermined space, the tags being responsive to predetermined interrogation signals to transmit a response signal, means for detecting response signals transmitted by electronic tags within the predetermined space, and means for determining the location of tags within the predetermined space from detected response signals.

21. An apparatus according to claim 20, wherein response signals are detected by a plurality of receivers distributed within the predetermined space, each receiver being adapted to detect response signals transmitted by tags within a predetermined range of that receiver.

22. An apparatus according to claim 21, wherein the predetermined ranges of adjacent receivers overlap, and means are provided to determine the location of a user by correlating the detection of a response signal by a plurality of receivers.

23. An apparatus according to any one of claims 20, 21 or 22, wherein each tag comprises means to respond to two interrogation signals.

24. An apparatus according to claim 23, wherein each tag is responsive to a short range RFID interrogation signal and a long range RFID interrogation signal.

25. An apparatus according to any one of claims 20 to 24, wherein an associated electronic tag comprises means to alert a user to detection of an interrogation signal.

26. An apparatus according to claim 25, wherein the altering means comprise a buzzer, light, or trembler incorporated in the associated electronic tag.

27. An apparatus according to claim 25 or 26, wherein the alerting means comprises a display showing information received with the detected interrogation signal.

28. An apparatus according to any one of claims 20 to 27, comprising means to indicate if a user passes a predetermined boundary within the predetermined space.

29. An apparatus according, to any one of claims 20 to 28, comprising means to indicate a distance between a user's location and a predetermined point location within the predetermined space.

30. An apparatus according to any one of claims 20 to 29, comprising means to indicate a transit time from a user's location to a predetermined location within the predetermined space.

31. An apparatus according to any one of claims 20 to 30, comprising means to deliver directions for transit from a user's location to a predetermined point to the user's associated tag.

32. An apparatus according to any one of claims 20 to 31, wherein the predetermined space comprises a plurality of airports through which a user may pass, whereby a user may pass through the plurality of airports using the same electronic tag.

33. An apparatus for carrying out the method of any one of claims 1 to 19.

34. A computer program for controlling a computer to carry out a method according to any one of claims 1 to 19.

35. An electronic tag for use in a method according to any one of claims 1 to 19, comprising means for storing an identifier, means for receiving a plurality of distinct interrogation signals, and means for responding to a received interrogation signal.

36. An electronic tag according to claim 35, wherein the plurality of distinct interrogation signals comprise a long range RFID interrogation signal and a short range RFID interrogation signal.

37. An electronic tag according to claim 35 or 36, further comprising a microprocessor connected to a memory unit.

38. An electronic tag according to claim 35, 36 or 37, further comprising display means.

39. An electronic tag comprising a passive circuit which in use is powered by a predetermined radio frequency signal transmitted from a remote source, and an active circuit incorporating a power source for transmitting data from the tag, the active circuit being enabled by the passive circuit upon detection of the predetermined radio frequency signal and switched off to conserve the power source unless enabled by the passive circuit.

40. An electronic tag for allocation to a passenger in an airport to serve as a boarding pass for the passenger to whom it is allocated, comprising means for receiving transmitted information related to the intended departure of the respective passenger.

41. A method substantially as hereinbefore described, with reference to the accompanying drawings.

42. An apparatus substantially as hereinbefore described, with reference to the accompanying drawings.

43. An electronic tag substantially as hereinbefore described with reference to the accompanying drawings.