U.S. patent application number 10/648872 was filed with the patent office on 2004-02-26 for location finding system and method.
Invention is credited to Avery, David M..
Application Number | 20040038677 10/648872 |
Document ID | / |
Family ID | 10858543 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040038677 |
Kind Code |
A1 |
Avery, David M. |
February 26, 2004 |
Location finding system and method
Abstract
A method of locating an article or person comprises at least one
transponding station (TS 1) having its own radio identity carried
by a person or article in the radio coverage area of a radio
system. The system comprises a plurality of clusters of spatially
separate radio units (M1 to M7) having transceiving means and
received signal strength determining means, each of the radio units
having an individual identity. Each cluster is associated with a
network interrogating station (NIU(1), NIU(2)) comprising
transceiving means for communicating with at least the radio units
in its cluster. A central station (10) has transceiving means for
communicating with a plurality of the interrogating stations and
storage means for storing a database comprising the locations of
the radio units (M1 to M7). When it is required to determine the
location of the transponding station, the central station transmits
an enquiry signal to the interrogating stations which in turn
broadcast the enquiry signal. The transponding station in response
to hearing its radio identity in an enquiry signal transmits a
reply signal including its own radio identity on a frequency (F2)
to which the radio units are already tuned or to which they have
retuned in the case of the transmit frequency being the same as
that of the enquiry signal. The in-range radio units identify the
transponding station and determine the received signal strength and
in response to receiving an interrogation signal the radio units
relay the radio identity of the transponding station, the
determined received signal strength and its own identity to the
interrogating station which relays the information to the central
station (10), whereat the location of the transponding station
relative to the positions of the radio units is computed.
Inventors: |
Avery, David M.; (Woking,
GB) |
Correspondence
Address: |
PHILIPS INTELLECTUAL PROPERTY & STANDARDS
P.O. BOX 3001
BRIARCLIFF MANOR
NY
10510
US
|
Family ID: |
10858543 |
Appl. No.: |
10/648872 |
Filed: |
August 27, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10648872 |
Aug 27, 2003 |
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09631361 |
Aug 2, 2000 |
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6657549 |
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Current U.S.
Class: |
455/422.1 ;
455/444; 455/446 |
Current CPC
Class: |
G01S 5/0081 20130101;
G01S 13/878 20130101; G01S 5/14 20130101 |
Class at
Publication: |
455/422.1 ;
455/446; 455/444 |
International
Class: |
H04Q 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 1999 |
GB |
9918348.5 |
Claims
1. A radio system comprising a plurality of clusters of spatially
separate radio units having transceiving means and received signal
strength determining means, each of the radio units having an
individual identity, each cluster being associated with an
interrogating station comprising transceiving means for
communicating with at least the radio units in its cluster, a
central station having transceiving means for communicating with a
plurality of the interrogating stations and storage means for
storing a database comprising the locations of the radio units, and
at least one transponding station having transceiving means and its
own radio identity, whereby when it is required to determine the
location of the transponding station the central station transmits
an enquiry signal including its radio identity to the interrogating
stations which rebroadcast the enquiry signal, the transponding
station in response to hearing its radio identity in an enquiry
signal transmits a reply signal including its own radio identity,
the radio units in response to identifying the transponding station
determine the received signal strength, and each of the radio units
relaying the radio identity and the determined received signal
strength together with its own identity to at least one of the
interrogating stations which relays the information to the central
station which computes the location of the transponding station
relative to the positions of the radio units.
2. A radio system as claimed in claim 1, characterised in that the
transceiving means of the at least one transponding station
transmits a reply signal at a frequency corresponding substantially
to the frequency to which said radio units are tuned.
3. A radio system as claimed in claim 1, characterised in that the
transceiving means of the at least one transponding station
receives and transmits on the same frequency and in that at least
the radio units and at least one of the interrogating stations
include frequency changing means for changing at least their
receive frequencies to the transmitting frequency of the at least
one transponding station.
4. A method of locating at least one transponding station having
its own radio identity in the radio coverage area of a radio system
comprising a plurality of clusters of spatially separate radio
units having transceiving means and received signal strength
determining means, each of the radio units having an individual
identity, each cluster being associated with an interrogating
station comprising transceiving means for communicating with at
least the radio units in its cluster, and a central station having
transceiving means for communicating with a plurality of the
interrogating stations and storage means for storing a database
comprising the locations of the radio units, wherein when it is
required to determine the location of the transponding station, the
central station transmits an enquiry signal to the interrogating
stations which in turn broadcast the enquiry signal, the
transponding station in response to hearing its radio identity in
an enquiry signal transmits a reply signal including its own radio
identity, the in-range radio units identifying the transponding
station and determining the received signal strength and relaying
the radio identity of the transponding station, the determined
received signal strength and its own identity to the interrogating
station which relays the information to the central station which
computes the location of the transponding station relative to the
positions of the radio units.
5. A method as claimed in claim 4, characterised by the at least
one transponding station using a received signal as a reference
frequency against which its own oscillator frequency is
adjusted.
6. A method as claimed in claim 4, characterised in that in
anticipation of a transmission by the at least one transponding
station, the radio units and at least one of the interrogating
stations adjust their receive frequency to the transmit frequency
of the at least one transponding station.
7. A method as claimed in any one of claims 4 to 6, characterised
by the radio metering units being placed in a faster wake-up mode
when determining the location of a transponder station than in a
non-location determining mode.
8. A transponding station comprising non-volatile storage means for
storing the unit's radio identity, a radio receiver for receiving
an enquiry signal, means for comparing the stored radio identity
with a radio identity in the enquiry signal, and means responsive
to the radio identities being considered to be substantially the
same for activating a transmitter to send a reply signal having at
least one characteristic different from the received enquiry.
9. A transponding station as claimed in claim 8, characterised in
that the radio receiver is adapted to receive the enquiry signal at
a first frequency and to relay a signal to the transmitter for
transmission at a second frequency.
10. A transponding station as claimed in claim 9, characterised in
that the radio receiver and the transmitter operate on the same
frequency.
Description
[0001] The present invention relates to an article or person
location finding system and method.
[0002] Many methods of locating articles and persons are known. A
relatively coarse location method making use of the cellular
telephone system is to determine the location of the base station
through which a call is being handled. This will give an indication
of the cell in which the caller is located. Typically a cell may be
say 20 km across in a lower frequency operating system and
significantly less in a micro-cellular system operating at low
power at a higher frequency of the order of 1.8 or 1.9 GHz. If a
GPS satellite receiver is integrated with a cellular telephone,
position can be determined to an accuracy of about 100 m.
[0003] WO-A-97 33 386 discloses a location detecting system in
which the location of a cellular telephone terminal can be found by
the terminal transmitting base station identifications together
with electric field strengths of the received radio waves of a
plurality of base stations to a position management station which
determines the location of the terminal by using the relationship
between the electric field strength and the distance between the
transmitting points and the receiving point.
[0004] A disadvantage of these known systems is that they require
the user to be carrying and using a relatively expensive terminal
unit. This makes the system expensive to implement for article
tracing or for applications such as automatically tracking or
finding children who would not be entrusted with a cellular
telephone terminal.
[0005] An object of the present invention is to provide a location
system having a relatively inexpensive transponding unit.
[0006] According to one aspect of the present invention there is
provided a radio system comprising a plurality of clusters of
spatially separate radio units having transceiving means and
received signal strength determining means, each of the radio units
having an individual identity, each cluster being associated with
an interrogating station comprising transceiving means for
communicating with at least the radio units in its cluster, a
central station having transceiving means for communicating with a
plurality of the interrogating stations and storage means for
storing a database comprising the locations of the radio units, and
at least one transponding station having transceiving means and its
own radio identity, whereby when it is required to determine the
location of the transponding station the central station transmits
an enquiry signal including its radio identity to the interrogating
stations which rebroadcast the enquiry signal, the transponding
station in response to hearing its radio identity in an enquiry
signal transmits a reply signal including its own radio identity,
the radio units in response to identifying the transponding station
determine the received signal strength, and each of the radio units
relaying the radio identity and the determined received signal
strength together with its own identity to at least one of the
interrogating stations which relays the information to the central
station which computes the location of the transponding station
relative to the positions of the radio units.
[0007] According to a second aspect of the present invention there
is provided a method of locating at least one transponding station
having its own radio identity in the radio coverage area of a radio
system comprising a plurality of clusters of spatially separate
radio units having transceiving means and received signal strength
determining means, each of the radio units having an individual
identity, each cluster being associated with an interrogating
station comprising transceiving means for communicating with at
least the radio units in its cluster, and a central station having
transceiving means for communicating with a plurality of the
interrogating stations and storage means for storing a database
comprising the locations of the radio units, wherein when it is
required to determine the location of the transponding station, the
central station transmits an enquiry signal to the interrogating
stations which in turn broadcast the enquiry signal, the
transponding station in response to hearing its radio identity in
an enquiry signal transmits a reply signal including its own radio
identity, the in-range radio units identifying the transponding
station and determining the received signal strength and relaying
the radio identity of the transponding station, the determined
received signal strength and its own identity to the interrogating
station which relays the information to the central station which
computes the location of the transponding station relative to the
positions of the radio units.
[0008] According to a third aspect of the present invention there
is provided a transponding unit comprising non-volatile storage
means for storing the unit's radio identity, a radio receiver for
receiving an enquiry signal, means for comparing the stored radio
identity with a radio identity in the enquiry signal, and means
responsive to the radio identities being considered to be
substantially the same for activating a transmitter to send a reply
signal having at least one characteristic different from the
received enquiry.
[0009] The at least one characteristic may be the frequency of the
reply signal being different from that of the enquiry signal or the
signalling rate of the reply signal being different from that of
the enquiry signal.
[0010] In implementing the system, the infrastructure may be a
modified version of an installed wide area automatic metering
system for use in measuring consumption of for example water, gas,
electricity and/or heating water in domestic and business premises.
Thus in urban areas the radio unit comprises the telecommunications
part of a metering unit coupled to each of the premises which will
enable a resolution equivalent to one dwelling to be obtained. The
network interrogating stations are normally mounted in advantageous
positions, for example on posts, from a radio communications point
of view. In rural areas where the radio units may be dispersed less
densely than in urban areas, the network interrogating stations may
function as radio units for the purpose of location finding and
information is relayed to the central station by way of one or more
intermediate network interrogation stations functioning as relay
stations.
[0011] A transponding station may be physically small so that it
can comprise an accessory which can be attached to clothing,
especially children's clothing, or integrated into a container for
an article or attached to the article. The transponder station is
typically a transceiver which is able to receive an enquiry signal
at one frequency and transmit a signal at another frequency.
[0012] The present invention will now be described, by way of
example, with reference to the accompanying drawings, wherein:
[0013] FIG. 1 is a diagrammatic of the embodiment of a location
system,
[0014] FIG. 2 is a block schematic diagram of a central metering
station,
[0015] FIG. 3 is a block schematic diagram of a transponding
station,
[0016] FIG. 4 is a block schematic diagram of a radio metering
unit, and
[0017] FIG. 5 is a flow chart showing the sequence of operations
when conducting a location enquiry.
[0018] In the drawings the same reference numerals have been used
to indicate corresponding features.
[0019] The system shown in FIG. 1 comprises a central metering
station 10 which comprises a large computer 12 and a transceiver 14
coupled to antennas 16, 18 which may provide antenna diversity. The
computer 12 stores a map of the entire system.
[0020] A plurality of geographically distributed radio metering
units M1 to M7, for example water metering units, are connected to
each of the domestic and industrial premises receiving the
particular commodity. As will be described later in greater detail
each metering unit comprises a radio transceiver coupled to an
antenna which may be incorporated into the lid of a boundary box
containing the meter or which may comprise a whip antenna suitably
positioned to provide good signal reception and propagation. The
radio metering units are loosely arranged in clusters which are
operatively associated with network interrogation units NIU (1) and
NIU (2). Each of the network interrogation units includes a
transceiver to enable it to receive messages from the metering
units in its cluster and to relay messages to the central metering
station. In certain cases, such as in rural environments, radio
relay network interrogation units NIU (R) are provided. However it
is possible for NIU (1) and NIU (2) to provide a relay function
when called upon to do so.
[0021] A transponder station TS1 is carried by a person, for
example a child, or an article, for example a vehicle or package.
Each transponder station comprises a transceiver and a store for
storing a unique identity which is included in transmitted
messages.
[0022] In operation as a metering system, the network interrogating
units NIU (1) and NIU (2) interrogate individually the radio
metering units M1 to M4 and M5 to M7 in their respective clusters
and store the meter reading and the meter's identity.
Alternatively, or additionally, the radio metering units may make
their transmissions at random. From time to time the central
metering station 10 contacts the respective network interrogation
units which download the stored meter readings and identities. The
transmission frequency or frequencies lie within an approved
frequency band reserved for this purpose. For ease of illustration
it will be assumed that a single frequency F2 is used.
[0023] In one embodiment of a location finding mode the central
metering station 10 or a dedicated control centre (not shown) sends
a short message including a unique address, such as "TS1", to some
or all of the NIUs depending on the breath of the search. The NIUs
transmit on a dedicated emergency channel F1 receivable by all the
transponder stations "TS1 please transmit your ID on frequency F2".
The frequency F2 is the customary frequency used for metering units
to transmit to their NIU. The frequency F2 could be different
depending upon the area, type of utility and company owning the
meter reading system.
[0024] The transponding station TS1 responds to the above message
by retuning its transmitter to the frequency F2 and transmits "TS1
responding". This message is received by in-range radio metering
units and perhaps also by some interrogation units NIUs. The
metering units measure the strength of the received signal. When
interrogated by the interrogation unit poling in turn the metering
units in its cluster, messages such as "Meter M1 has heard TS1 at
signal level 56" and "Meter M2 has heard TS1 at signal level 23"
are transmitted. The interrogation unit relays these messages to
the central metering station 10 which using the map data stored in
its data base can determine the location of the metering unit which
received the message with the highest signal level. The relatively
high density of metering units in an urban area will mean that the
person, article or vehicle carrying the transponding station TS1
can be identified visually. If the transponder station is moved
then its movement can be tracked.
[0025] In another embodiment (not shown) the transponder stations
receive and transmit on the same frequency, such as F1, and the
radio metering units and some or all of the NIUs retune their
transceivers to F1. The retuned condition may be maintained until
another retune signal is received or the condition is timed-out and
the radio metering units and NIU's retune themselves.
[0026] Referring to FIG. 2, the central metering station 10
comprises a receiver 14R having an input coupled to the antennas
16, 18 and an output coupled to a decoder 20. The decoder 20 is
coupled to the controller 12 which operates in accordance with
software stored in a PROM 22. Various facilities and databases are
coupled to the controller 12. These include a data base of the
locations of the interrogating units and the metering units, a
billing facility 26 for compiling bills to be sent to consumers, a
display device 28, a store 30 for storing the identifications of
the interrogation units NIUs and radio metering units M1 to M7 and
a store 32 for storing the identification of the transponding
stations. The controller 12 has an input for external data which
may be via the PSTN or a local personal computer generally
represented by the block referenced 42.
[0027] If it is required that the central metering station 10 sends
a message, it is generated in a stage 36. The message is relayed to
a transmitter 14T which is coupled to the antennas 16, 18.
[0028] A frequency synthesiser 38 is coupled to the receiver 14R
and the transmitter 14T. Its output frequency is determined by the
controller and a set frequency signal is applied on an output 40.
The receiver 14R and the transmitter 14T are able to be tuned over
a range of frequencies in the assigned meter reading band.
[0029] FIG. 3 illustrates an embodiment of the transponding station
TS1 which comprises an antenna 50, which may be a loop antenna,
coupled to a receiver 52 and a transmitter 54. The receiver 52 is
coupled to a decoder 56 which in turn is coupled to a controller
58. If desired the decoder 56 may be omitted and the decoding
function is carried out by the controller 58 under software
control. A PROM 60 (or a code plug) storing the transponding
station's identity is coupled to the controller 58. In the
embodiment in which the receive and transmit frequencies are the
same, the required locally generated signals are produced using a
fixed frequency generator 62 which is coupled to the receiver 52
and the transmitter 54. However in the embodiment in which the
transmit frequency, say F2, is different from the receive
frequency, say F1, the frequency generator 62, is controlled to
generate a local oscillator signal which will enable the receiver
52 to receive the frequency F1 and to generate a frequency which
will enable the transmitter 54 to transmit on the frequency F2.
Since the transponding station TS1 need only to be able to respond
to a location enquiry signal, the controller 58 prestores an
appropriate message with the station's identification being
obtained from the PROM 60.
[0030] The transponding station TS1 is battery powered using a
battery 64. In order to maximise the battery life, the receiver 52
is energised periodically in accordance with a battery saving
protocol. It is convenient if the protocol used is compatible with
the protocol used by the radio metering units. Thus in order to
ensure that the transponding station TS1 receives an enquiry
message, the message has to be repeated over a time period
equivalent to twice the normal on-period of the receiver 52 plus
the off-period between two successive on-periods.
[0031] In the single frequency embodiment of the frequency
generator 62, the local oscillator may have a low tolerance crystal
and use the receive frequency F1 as a reference to pull the local
oscillator frequency. An advantage of using F1 is that it is a
relatively stable frequency and is unaffected by ageing of
components of the transponding station TS1.
[0032] FIG. 4 shows an implementation of a radio metering unit M.
An antenna 70 is coupled to a receiver 72 and a transmitter 74. The
receiver 72 is coupled to a decoder 76 which in turn is coupled to
a controller 78 operating in accordance with a program stored in a
ROM 80. Also coupled to the controller 78 are a PROM storing the
unit's identification, a metering unit 84, which provides a digital
output representing the consumption of the resource, for example
water, being measured, a RAM 86 for storing the consumption, a
frequency synthesiser 88, received radio signal strength indication
(RSSI) determining stage 90 and a battery 91. In normal operation
the metering unit M receives and transmits signals at the same
frequency F2 but as different systems operate at other frequencies
in the allocated metering band, the use of a frequency synthesiser
88 enables the receiver 72 and the transmitter to be tuned to the
desired channel. In the embodiment of the transponding station
being a single frequency device, the frequency synthesiser 88 will
enable the radio metering unit to be retuned as required and be
retuned back again either in response to an instruction to retune
or as a result of timing-out after being in a temporary retuned
state.
[0033] An interrogation unit NIU is essentially the same a radio
metering unit with the differences that it will not be connected to
a metering unit, the PROM 82 will store all the metering unit
identifications in the cluster and the RAM 86 will have sufficient
capacity to store all the measurements being relayed.
[0034] The radio metering units and the interrogation units all
practice battery economy in accordance with a suitable protocol
such as that disclosed in WO-A-99/25051. In summary the metering
unit has a radio identity code consisting of M bits and the network
interrogation unit NIU (or the central metering station, if
applicable) transmits a wake-up message consisting at least two
repetitions of a wake-up sequence, the wake-up sequence comprising
N concatenated parts, where N is an integer, each of the N parts
includes a sync code word and a different fraction M/N of bits of a
radio identity code. The metering unit is energised intermittently
in order to detect carrier and at least one of the N parts. In
response to detecting that one of the N parts, the metering unit
remains energised and analyses at least the detected one of the N
parts. If the received bits of the radio identity code do not
correspond to the corresponding bits of the metering unit's radio
identity code, the metering unit reverts to its intermittent
energisation, otherwise it remains energised to receive a message
appended to the transmitted radio identity code.
[0035] The flow chart shown in FIG. 5 commences with block 92
denoting the central metering station receiving an SOS request and
transmitting a message identifying the transponding station. Block
94 relates to the interrogation units relaying the message on the
frequency F1. Block 96 denotes the transponding stations receiving
the relayed message. In Block 98 a check is made to see if the
identity of the requested transponding station agrees with that
allocated to the station. If the answer is yes (Y), the flow chart
proceeds to block 102 which relates to the identified transponding
station replying on frequency F2 (or F1). If the answer is no (N),
the transponding station reverts to its battery economy mode.
[0036] Block 104 relates to in-range metering units receiving the
response on F2 (or F1) and checking the received signal strength.
Block 106 relates to the metering units forwarding their messages
to the network interrogation unit either at random or in response
to an invitation. Block 108 relates to checking to see if all the
metering units in a cluster have responded or have been poled. If
the answer is no (N) the flow chart reverts to the block 108 but if
it is yes (Y) the flow chart proceeds to the block 110. This block
denotes an interrogation unit relaying messages it has stored onto
the central metering station. Generally this will be done in
response to over-the-air invitations issued by the central metering
station.
[0037] Block 112 denotes the central metering station receiving the
messages and using the signal strength indications to determine the
metering unit closest to the transmitting transponder. Block 114
relates to the central metering unit providing an output comprising
the identification of the closest metering unit.
[0038] In order to minimise current consumption by the transponding
station TS1 and the radio metering units, the metering units may be
placed in a fast wake-up mode in which they are activated either
continuously for a short time or more frequently than in their
meter reading mode in order to be able to detect quickly a sequence
of short messages transmitted by the transponding station TS1.
[0039] In a further non-illustrated embodiment the central metering
station and the network interrogation units have a separate
dedicated emergency receiver which receives a message from a
transponding station. A coarse determination of the location of the
transponding station can be made and then the central metering
station can put in hand a fine search based on using the radio
metering units in the localised area determined by the coarse
search.
[0040] 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.
[0041] From reading the present disclosure, other modifications
will be apparent to persons skilled in the art. Such modifications
may involve other features which are already known in the design,
manufacture and use of radio location systems and component parts
thereof and which may be used instead of or in addition to features
already described herein.
* * * * *