WO2013008169A1 - Accurate location determination in a specified area - Google Patents

Accurate location determination in a specified area Download PDF

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Publication number
WO2013008169A1
WO2013008169A1 PCT/IB2012/053499 IB2012053499W WO2013008169A1 WO 2013008169 A1 WO2013008169 A1 WO 2013008169A1 IB 2012053499 W IB2012053499 W IB 2012053499W WO 2013008169 A1 WO2013008169 A1 WO 2013008169A1
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WO
WIPO (PCT)
Prior art keywords
sound
signal
receiver
synchronizer
location
Prior art date
Application number
PCT/IB2012/053499
Other languages
French (fr)
Inventor
Boaz Ben-Moshe
Original Assignee
Indoorgo Navigation Systems Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US201161506100P priority Critical
Priority to US61/506,100 priority
Application filed by Indoorgo Navigation Systems Ltd. filed Critical Indoorgo Navigation Systems Ltd.
Publication of WO2013008169A1 publication Critical patent/WO2013008169A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S1/00Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/72Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using ultrasonic, sonic or infrasonic waves
    • G01S1/76Systems for determining direction or position line
    • G01S1/80Systems for determining direction or position line using a comparison of transit time of synchronised signals transmitted from non-directional transducers or transducer systems spaced apart, i.e. path-difference systems
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/16Systems for determining distance or velocity not using reflection or reradiation using difference in transit time between electrical and acoustic signals
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/18Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
    • G01S5/30Determining absolute distances from a plurality of spaced points of known location

Abstract

Disclosed are devices and devices useful in the field of determining the location of a sound-receiver.

Description

ACCURATE LOCATION DETERMINATION IN A SPECIFIED AREA

RELATED APPLICATION

The present application gains priority from US Provisional Patent Application 61/506,100 filed 10 July 2011.

FIELD AND BACKGROUND OF THE INVENTION

The invention, in some embodiments, relates to the field of location determination, and more particularly, but not exclusively, to methods and devices useful for assisting in accurately determining a location of an object in a specified area.

There is often a need to determine the location of an object found in a specified area with great accuracy. For example, in the field of Location-Based Services (LBS), it is often required to known the location of a person with great accuracy.

Global navigation satellite systems (GNSS) methods for location determination are based on a terrestrial GNSS receiver receiving satellite transmissions from orbiting GNSS satellites. When the GNSS receiver is indoors, GNSS systems are unsuitable for location determination for various reasons, including that line of sight between the GNSS receiver and the GNSS satellites is blocked.

An indoor positioning system (IPS) is a network of devices used to wirelessly determine the location of objects inside a building or otherwise defined space. Known indoor positioning systems suffer from various limitations.

There is a need for an indoor positioning system that does not suffer from some or all of the limitations of known such systems.

SUMMARY OF THE INVENTION

The invention, in some embodiments, relates to the field of location determination, and more particularly, but not exclusively, to methods and devices useful for assisting in accurately determining a location of an object in a specified area.

In some embodiments, the invention relates to methods and devices useful for assisting in accurately determining a location of an object indoors, using a time of flight indoor positioning system design.

In some embodiments, the invention includes generation of discrete sound-signals from at least one localized sound-source. In some embodiments, a discrete sound-signal is generated substantially simultaneously with transmission of a wireless electromagnetic transmission that indicates the start-time of the sound-signal. The time difference between receipt of the electromagnetic transmission (for which the time of flight is considered virtually instantaneous) and receipt of the sound signal by a sound-receiver is the time of flight of the sound signal.

In some embodiments, a discrete sound-signal is generated a predetermined duration after the transmission of a wireless electromagnetic transmission. In such embodiments, the travel time of the sound signal is computed by subtracting the predetermined duration from the time difference between receipt of the electromagnetic transmission and receipt of the sound signal.

Since the speed of sound is known, the travel time of the sound signal allows calculation of the distance from the sound-source to the sound-receiver, which distance can then be used, using methods known in the art such as trilateration, to determine the location of the sound-receiver.

In accordance with some aspects of an embodiment of the teachings herein, there are provided methods for determining the location of a receiver in a specified area, comprising: from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;

at a plurality of sound-sources located in a specified area, receiving the synchronizing signal;

from each of the plurality of sound-sources, at a predetermined delay duration after receipt of the synchronizing signal, transmitting a sound signal having a base frequency;

at a sound-receiver located in the specified area, receiving the synchronizing signal and at least two of the sound signals transmitted by the sound-sources;

computing the time of flight of at least some of the received sound signal based on receipt of the received sound signals, receipt of the synchronizing signal, and on a respective the predetermined delay duration; and

using the calculated time of flight and respective the known locations of the sound- sources for which the time of flight is computed, determining the location of the receiver in the defined area.

In accordance with some aspects of an embodiment of the teachings herein, there are provided methods for providing signals useful in determining the location of a sound-receiver in a specified area, comprising: from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;

at a plurality of sound-sources located in known locations in a specified area, receiving the synchronizing signal; and

from each of the plurality of sound-sources, at a predetermined delay duration after receipt of the synchronizing signal, transmitting a sound signal having a base frequency.

In accordance with some aspects of an embodiment of the teachings herein, there are provided methods for determining the location of a sound-receiver in a specified area, comprising:

at a sound-receiver located in a specified area, receiving a synchronizing signal at a synchronizing rate;

at the sound-receiver, receiving at least two sound signals transmitted by sound- sources located in the specified area, each of the at least two sound signals having a base frequency and being transmitted from the sound-sources a predetermined delay duration after the receipt of the synchronizing signal by the sound-sources;

computing the time of flight of at least some of the received sound signals based on receipt of the received sound signals, receipt of the synchronizing signal, and on a respective the predetermined delay duration; and

using the calculated time of flight and respective the known locations of the sound- sources for which the time of flight is computed, determining the location of the sound-receiver in the specified area.

In some embodiments, the synchronization signal is transmitted based on a reference time. In some such embodiments, the reference time is a local reference time, such as a reference time of the synchronizer or of one of the sound-sources. In some such embodiments, the reference time is an external local time, such as UTC (coordinated universal time), TAI (International Atomic Time), PTP according to the IEEE 1588 standard (accuracy of better than 1 microsecond), or a GNSS clock.

In some embodiments, transmitting the synchronizing signal comprises transmitting a wireless electromagnetic radiation signal. In some such embodiments, the electromagnetic radiation signal comprises a radiofrequency signal. In some such embodiments the electromagnetic radiation signal comprises an infrared signal. In some embodiments, transmitting the synchronizing signal comprises transmitting an electromagnetic signal over a physical medium, (e.g., wired transmission). In some embodiments, the synchronizing rate is in the range of 100Hz to lHz.

In some embodiments, the method also comprises from the synchronizer, also transmitting at least one of a sound-signal schedule and location information for at least one of the plurality of sound- sources.

In some embodiments, the synchronizer comprises a Wi-Fi access point and the synchronizing signal comprises a Wi-Fi beacon frame. In some such embodiments, the transmitting at least one of the sound signal schedule and the location information comprises embedding the at least one of the sound signal schedule and the location information in the Wi-Fi beacon frame and transmitting the Wi-Fi beacon frame.

In some embodiments, the sound-signal schedule comprises information relating to at least one of a predetermined delay duration, a sound-signal duration, a sound-signal frequency, and a sound-signal modulation, for at least one sound-signal transmitted by at least one of the plurality of sound-sources. In some embodiments, the location information comprises absolute location information for the at least one of the plurality of sound- sources. In some embodiments, the location information comprises location information for the at least one of the plurality of sound-sources relative to a location of the synchronizer.

In some embodiments, the predetermined delay duration is unique to each one of the plurality of sound- sources. In some embodiments, the predetermined delay duration is the same for at least two of the sound-sources. In some embodiments, the predetermined duration is the same for all the plurality of sound- sources.

In some embodiments, the predetermined delay duration corresponding to at least one of the plurality of sound-sources is equal to zero, and the sound signal of the at least one sound-source is transmitted substantially simultaneously with the synchronizing signal.

In some embodiments, each one of the sound signals has characteristics identifying from which one of the plurality sound-sources the sound signal is transmitted. In some such embodiments, the characteristic comprises a unique the base frequency for each one of the plurality of the sound- sources. In some such embodiments, the characteristic comprises a unique modulation for each of the plurality of the sound-sources. In some such embodiment, the characteristic comprises a unique signal duration for each of the plurality of the sound- sources.

In some embodiments, the base frequency is in the range of 18 kHz and 24 kHz. In some embodiments, the base frequency is in the range of 21 kHz and 24 kHz.

In some embodiments, the duration of a specific the sound-signal is not more than 100 microseconds. In some embodiments, the duration of a specific the sound-signal is not more than 50 microseconds. In some embodiments, the duration of a specific the sound-signal is not more than 20 microseconds. In some embodiments, the duration of a specific the sound signal is not less than 0.1 microseconds. In some embodiments, the duration of a specific the sound-signal is in the range of 1 and 10 microseconds.

In some embodiments, a repetition rate of the transmitting the sound-signal is less frequent than a maximum repetition rate. In some embodiments, the maximal repetition rate is 5 Hz.

In some embodiments, at least one specific sound-source of the plurality of sound- sources comprises a modified Wi-Fi access point including a speaker for transmitting the sound signal. In some embodiments, each of the plurality of sound-sources comprises a modified Wi-Fi access point including a speaker for transmitting a respective the sound signal.

In some embodiments, the modified Wi-Fi access point operates as a standard access point and recurrently transmits Wi-Fi beacon frames. In some such embodiments, the method also comprises embedding in the beacon frames information relating to the modified Wi-Fi access point sound-source. In some such embodiments, the information includes at least one of an identifier of the modified Wi-Fi access point sound-source, physical coordinates of the modified Wi-Fi access point sound-source, a base frequency of a sound-signal transmitted by the modified Wi-Fi access point sound-source, a duration of a sound-signal transmitted by the modified Wi-Fi access point sound-source, a predetermined delay duration corresponding to the modified Wi-Fi access point sound-source, and a start-time schedule of start times of generation of the next sound-signals transmitted by the modified Wi-Fi access point sound- source.

In some embodiments, each of the plurality of sound-sources comprises a modified Bluetooth® device, and the method also comprises establishing at least one Bluetooth® network comprising the sound-sources, recurrently transmitting a sound-generation schedule to the plurality of sounds sources over the at least one Bluetooth® network, and the sound- sources transmitting sound signals in accordance with the sound-generation schedule.

In some embodiments, each of the plurality of sound-sources comprises a modified Bluetooth® device, and the method also comprises from a Bluetooth® master device, recurrently transmitting a sound-generation schedule to a plurality of Bluetooth® slave devices, and from each Bluetooth® slave device, transmitting sound signals in accordance with the sound-generation schedule. In some such embodiments, the sound-generation schedule includes at least one of a sound-signal start time, an identity of a single the sound-source, a location of the single the sound-source, a base frequency for the sound signal, and a duration of the sound signal.

In some embodiments, the sound-source is a device comprising a speaker, a radio- receiver, a processor and a clock.

In some embodiments the sound-receiver is a device comprising a microphone, a radio receiver, a processor, and a clock. In some embodiments, the sound-receiver comprises a modified mobile device selected from the group consisting of a smart phone, a Wi-Fi enabled cell phone, a PDA, a mobile computer, a Bluetooth® earphone, and a tablet computer.

In some embodiments, the sound-receiver is in motion, and has a velocity of up to about 10 km/h (2.8 m/sec).

In some embodiments, the method also comprises the sound-receiver recurrently scanning Wi-Fi radio frequencies to identify beacon frames. In some such embodiments the method also comprises, upon identification of a beacon frame, interrogating the beacon frame for an identifier of one of the plurality of sound-sources, without establishing a Wi-Fi session.

In some embodiments, the method also comprises reporting the determined location to a user interface of the sound-receiver. In some embodiments, the method also comprises reporting the determined location to a location remote from the sound-receiver.

In some embodiments, the determining the location of the receiver comprises trilateration.

In some embodiments, the at least one synchronizer comprises a plurality of synchronizers, one of the plurality of synchronizers comprising a control synchronizer, and the method also includes from the control synchronizer, generating a synchronizer synchronizing signal for synchronizing the plurality of synchronizers, at each of the plurality of synchronizers, receiving the synchronizer synchronizing signal, and from each of the plurality of synchronizers, transmitting a the synchronizing signal at a set duration following receipt of the synchronizer synchronizing signal.

In some embodiments, the synchronizer synchronizing signal comprises a change of phase in an electrical current powering the plurality of synchronizers. In some embodiments, the synchronizer synchronizing signal comprises a Wi-Fi beacon frame transmitted by the control synchronizer.

In some embodiments, the method also comprises the sound-receiver accessing a database to retrieve information relating to a sound-source from which a sound signal was received based on at least one characteristic of the sound signal. In some such embodiments the information comprises at least one of physical coordinates of the sound-source from which the sound signal was received, a base frequency of the sound-signal transmitted by the sound-source from which the sound signal was received, a duration of the sound-signal transmitted by the sound-source from which the sound signal was received, and the predetermined delay duration corresponding to the sound-source from which the sound signal was received.

In some embodiments, the method also comprises prior to the computing of the time of flight and to the determining of the location, transmitting a time of receipt of the synchronizing signal and the times of receipt of the sound signals to a server and at the server, carrying out the computing and the determining.

In some embodiments, the method also comprises carrying out the computing of the times of flight at the sound-receiver, transmitting the computed times of flight to a server, and at the server, carrying out the determining.

In some embodiments, the computing of the times of flight and the determining of location are carried out at the sound-receiver.

In some embodiments, the determining the location is recurrent at a determining rate. In some such embodiments, the determining rate is in the range of 10 Hz - 0.01 Hz.

In some embodiments, a size of the specified area is in the range of 1 m2 to 10000 m2.

In some embodiments, the method also comprises determining a velocity vector of the sound-receiver. In some such embodiments, the determining of the velocity vector comprises determining a Doppler-shift to at least one of the plurality of sound-sources. In some such embodiments, the determining of the velocity vector comprises determining a difference between at least two the determined locations.

In accordance with some aspects of an embodiment of the teachings herein, there are provided devices for determining the location of a sound-receiver in a specified area, comprising:

at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate;

a plurality of sound-sources located in a specified area, configured to receive the synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of the synchronizing signal;

a sound-receiver located in the specified area, configured to receive the synchronizing signal and at least two of the sound signals transmitted by the sound-sources; a time-of-flight computing module, functionally associated with the receiver and configured to compute a time of flight of at least some of the sound signals received by the sound-receiver based on time of receipt of the synchronizing signal, time of receipt of the sound signals, and on a respective the predetermined delay duration; and a location determining module functionally associated with the time-of-flight computing module and configured to use the calculated time of flight and respective locations in the specified area of the sound-sources in for which the time of flight is computed to determine the location of the sound-receiver in the specified area.

In accordance with some aspects of an embodiment of the teachings herein, there are provided devices for providing signals useful in determining the location of a receiver in a specified area, comprising:

at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate; and

a plurality of sound-sources located in a specified area, configured to receive the synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of the synchronizing signal.

In accordance with some aspects of an embodiment of the teachings herein, there are provided devices for determining the location of a sound-receiver in a specified area, comprising:

a sound-receiver located in a specified area configured to receive a synchronizing signal and at least two sound signals transmitted by at least two sound-sources located in the specified area, each of the at least two sound signals being transmitted a predetermined delay duration after the receipt of the synchronizing signal by the at least two sound-sources;

a time-of-flight computing module, functionally associated with the sound-receiver and configured to compute the time of flight of at least some of the sound signals received by the sound-receiver based on time of receipt of the synchronizing signal, times of receipt of the sound signals, and on a respective the predetermined delay duration; and

a location determining module functionally associated with the time-of-flight computing module and configured to use the calculated time of flight and respective the locations in the specified area of the sound-sources for which the time of flight is computed to determine the location of the sound-receiver in the specified area. In some embodiments, the synchronizer is configured to transmit the synchronization signal based on a reference time. In some such embodiments, the reference time is a local reference time, such as a reference time of the synchronizer or of one of the sound-sources. In some such embodiments, the reference time is an external local time, such as UTC (coordinated universal time), TAI (International Atomic Time), PTP according to the IEEE 1588 standard (accuracy of better than 1 microsecond), or a GNSS clock.

In some embodiments, the synchronizing signal comprises a wireless electromagnetic radiation signal. In some such embodiments, the synchronizing signal comprises a radiofrequency signal. In some such embodiments the synchronizing signal comprises an infrared signal.

In some embodiments, the synchronizing signal comprises an electromagnetic signal and the synchronizer is configured to transmit the electromagnetic signal over a physical medium.

In some embodiments, the synchronizing rate is in the range of 100Hz to lHz.

In some embodiments, the synchronizer is also configured to transmit at least one of a sound-signal schedule and location information for at least one of the plurality of sound- sources.

In some embodiments, the synchronizer comprises a Wi-Fi access point and the synchronizing signal comprises a Wi-Fi beacon frame. In some such embodiments, the synchronizer is configured to embed the at least one of the sound signal schedule and the location information in the Wi-Fi beacon frame and transmitting the Wi-Fi beacon frame.

In some embodiments, the sound-signal schedule comprises information relating to at least one of the predetermined delay duration, a sound-signal duration, a sound-signal frequency, and a sound-signal modulation, for at least one sound-signal transmitted by at least one of the plurality of sound- sources.

In some embodiments, the location information comprises absolute location information for the at least one of the plurality of sound- sources. In some embodiments, the location information comprises location information for the at least one of the plurality of sound-sources relative to a location of the synchronizer.

In some embodiments, the predetermined delay duration is unique to each one of the plurality of sound- sources. In some embodiments, the predetermined delay duration is the same for at least two of the sound-sources. In some embodiments, the predetermined duration is the same for all the plurality of sound-sources. In some embodiments, the predetermined delay duration corresponding to at least one of the plurality of sound-sources is equal to zero, and the at least one sound-source is configured to transmit a corresponding the sound signal substantially simultaneously with the synchronizing signal.

In some embodiments, each one of the sound signals has characteristics identifying from which one of the plurality sound-sources the sound signal is transmitted. In some embodiments, the characteristic comprises a unique the base frequency for each one of the plurality of the sound- sources. In some embodiments, the characteristic comprises a unique modulation for each of the plurality of the sound-sources. In some embodiments, the characteristic comprises a unique signal duration for each of the plurality of the sound- sources.

In some embodiments, the base frequency is in the range of 18 kHz and 24 kHz. In some embodiments, the base frequency is in the range of 21 kHz and 24 kHz.

In some embodiments, the duration of a specific the sound-signal is not more than 100 microseconds. In some embodiments, the duration of a specific the sound-signal is not more than 50 microseconds. In some embodiments, the duration of a specific the sound-signal is not more than 20 microseconds. In some embodiments, the duration of a specific the sound signal is not less than 0.1 microseconds. In some embodiments, the duration of a specific the sound-signal is in the range of 1 and 10 microseconds.

In some embodiments, the at least one of the plurality of sound-sources is configured to transmit a sound signal at a repetition rate which is less frequent than a maximum repetition rate. In some embodiments, the maximal repetition rate is 5 Hz.

In some embodiments, at least one specific sound-source of the plurality of sound- sources comprises a modified Wi-Fi access point including a speaker for transmitting a the sound signal. In some embodiments, each of the plurality of sound-sources comprises a modified Wi-Fi access point including a speaker for transmitting a respective the sound signal.

In some embodiments, the modified Wi-Fi access point is configured to operate as a standard access point and to recurrently transmit Wi-Fi beacon frames. In some embodiments, the modified Wi-Fi access point is also configured to embed in the beacon frames information relating to the modified Wi-Fi access point sound-source.

In some embodiments, the information includes at least one of an identifier of the modified Wi-Fi access point sound-source, physical coordinates of the modified Wi-Fi access point sound-source, a base frequency of a the sound-signal transmitted by the modified Wi-Fi access point sound-source, a duration of a the sound-signal transmitted by the modified Wi-Fi access point sound-source, a predetermined delay duration corresponding to the modified Wi- Fi access point sound-source, and a start-time schedule of start times of generation of the next sound-signals transmitted by the modified Wi-Fi access point sound- source.

In some embodiments, each of the plurality of sound-sources comprises a modified Bluetooth® device, and each the modified Bluetooth® device is configured to connect to at least one Bluetooth® network comprising the sound-sources, recurrently receive a sound- generation schedule transmitted over the at least one Bluetooth® network, and transmit sound signals in accordance with the sound-generation schedule.

In some embodiments, each of the plurality of sound-sources comprises a modified Bluetooth® device, and each the modified Bluetooth® device is configured to, from a Bluetooth® master device, recurrently receive a sound-generation schedule, and to transmit sound signals in accordance with the sound-generation schedule.

In some embodiments, the sound-generation schedule includes at least one of a sound- signal start time, an identity of a single the sound-source, a location of the single the sound- source, a base frequency for the sound signal, and a duration of the sound signal.

In some embodiments, the sound-source comprises a speaker, a radio-receiver, a processor and a clock. In some embodiments, the sound-receiver comprises a microphone, a radio receiver, a processor, and a clock.

In some embodiments, the sound-receiver comprises a modified mobile device selected from the group consisting of a smart phone, a Wi-Fi enabled cell phone, a PDA, a mobile computer, a Bluetooth® earphone, and a tablet computer.

In some embodiments, the sound-receiver is configured to move at a velocity of up to about 10 km/h (2.8 m/sec). In some embodiments, the sound-receiver is also configured to recurrently scan Wi-Fi radio frequencies to identify beacon frames. In some embodiments, the sound-receiver is also configured, upon identification of a beacon frame, to interrogate the beacon frame for an identifier of one of the plurality of sound-sources, without establishing a Wi-Fi session.

In some embodiments, the sound-receiver comprises a user interface, the device also comprising a reporting module configured to report the determined location to the user interface of the sound-receiver. In some embodiments, the device also comprises a reporting module configured to report the determined location to a location remote from the sound- receiver.

In some embodiments, the location determining module is configured to use trilateration to determine the location of the sound-receiver. In some embodiments, the at least one synchronizer comprises a plurality of synchronizers, one of the plurality of synchronizers comprising a control synchronizer, wherein the control synchronizer is configured to generate a synchronizer synchronizing signal for synchronizing the plurality of synchronizers and each of the plurality of synchronizers is configured to receive the synchronizer synchronizing signal to transmit a the synchronizing signal at a set duration following receipt of the synchronizer synchronizing signal. In some embodiments, the synchronizer synchronizing signal comprises a change of phase in an electrical current powering the plurality of synchronizers. In some embodiments, the synchronizer synchronizing signal comprises a Wi-Fi beacon frame transmitted by the control synchronizer.

In some embodiments, the device also comprises a database including data relating to the plurality of sound sources, wherein the sound-receiver is also configured to access the database to retrieve information relating to a the sound-source from which a the sound signal was received based on at least one characteristic of the sound signal.

In some embodiments, the information comprises at least one of physical coordinates of the sound-source from which the sound signal was received, a base frequency of a sound- signal transmitted by the sound-source from which the sound signal was received, a duration of a sound-signal transmitted by the sound-source from which the sound signal was received, and a predetermined delay duration corresponding to the sound-source from which the sound signal was received.

In some embodiments, the device also comprises a remote server including the time of flight computing module and the location determining module, and wherein the sound receiver is configured to transmit to the remote server a time of receipt of the synchronizing signal and the times of receipt of the sound signals to a server for the time of flight module to compute the times of flight and for the location determining module to determine the location.

In some embodiments, the time of flight computing module forms part of the sound- receiver, wherein the device also comprises a remote server including the location determining module, wherein the sound receiver is configured to transmit to the remote server the computed times of flight for the location determining module to determine the location.

In some embodiments, the sound-receiver comprises the time of flight computing module and the location determining module, and wherein the computing of the times of flight and the determining of location are configured to be carried out at the sound-receiver. In some embodiments, the location determining module is configured to determine the location is recurrently at a determining rate. In some embodiments, the determining rate is in the range of 10 Hz - 0.01 Hz.

In some embodiments, a size of the specified area is in the range of 1 m2 to 10000 m2.

In some embodiments, the device also comprises a velocity determining module configured to determine a velocity vector of the sound-receiver. In some embodiments, the velocity determining module is configured to determine the velocity vector by determining a Doppler-shift to at least one of the plurality of sound-sources. In some embodiments, the velocity determining module is configured to determine a difference between at least two the determined locations.

Aspects and embodiments of the invention are described in the specification hereinbelow and in the appended claims.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. In case of conflict, the specification, including definitions, will control.

As used herein, the terms "comprising", "including", "having" and grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. These terms encompass the terms "consisting of and "consisting essentially of.

As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly dictates otherwise.

Some embodiments of the invention may involve performing or completing selected tasks manually, automatically, or a combination thereof. Some embodiments of the invention are implemented with the use of components that comprise hardware, software, firmware or combinations thereof. In some embodiments, some components are general-purpose components such as general-purpose computers or processors. In some embodiments, some components are dedicated or custom components such as circuits, integrated circuits or software. For example, some embodiments are performed, at least partially, as a plurality of software instructions executed by a data processor, for example which is part of a general- purpose or custom computer. In some embodiments, the data processor or computer comprises volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. In some embodiments, implementation includes a network (e.g., Internet, Intranet, wired, wireless) connection. In some embodiments, implementation includes a user interface, generally comprising one or more of input devices (e.g., allowing input of commands and/or parameters) and output devices (e.g., allowing reporting parameters of operation and results).

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the invention may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted are not to scale. In the Figures:

FIG. 1A is a schematic depiction of an embodiment of a sound- source according to the teachings herein;

FIG. IB is a schematic depiction of an embodiment of a sound-source using Wi-Fi infrastructure according to the teachings herein; and

FIG. 2 is a schematic depiction of an embodiment of a sound-receiver according to the teachings herein; and

FIG. 3 is a schematic depiction of an embodiment of a method for determining the location of a sound-receiver using Wi-Fi and ultrasound infrastructure according to the teachings herein.

DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

The invention, in some embodiments thereof, relates to location determination, which, in some aspects, has advantages over known methods of location determination.

Some embodiments of the invention relate to methods for determining the location of a receiver in a specified area, comprising:

from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;

at a plurality of sound-sources located in a specified area, receiving the synchronizing signal;

from each of the plurality of sound-sources, at a predetermined delay duration after receipt of the synchronizing signal, transmitting a sound signal having a base frequency; at a sound-receiver located in the specified area, receiving the synchronizing signal and at least two of the sound signals transmitted by the sound-sources;

computing the time of flight of at least some of the received sound signal based on receipt of the received sound signals, receipt of the synchronizing signal, and on a respective the predetermined delay duration; and

using the calculated time of flight and respective the known locations of the sound- sources for which the time of flight is computed, determining the location of the receiver in the defined area.

Some embodiments of the invention relate to methods for providing signals useful in determining the location of a sound-receiver in a specified area, comprising:

from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;

at a plurality of sound-sources located in known locations in a specified area, receiving the synchronizing signal; and

from each of the plurality of sound-sources, at a predetermined delay duration after receipt of the synchronizing signal, transmitting a sound signal having a base frequency.

Some embodiments of the invention relate to methods for determining the location of a sound-receiver in a specified area, comprising:

at a sound-receiver located in a specified area, receiving a synchronizing signal at a synchronizing rate;

at the sound-receiver, receiving at least two sound signals transmitted by sound- sources located in the specified area, each of the at least two sound signals having a base frequency and being transmitted from the sound-sources a predetermined delay duration after the receipt of the synchronizing signal by the sound-sources;

computing the time of flight of at least some of the received sound signals based on receipt of the received sound signals, receipt of the synchronizing signal, and on a respective the predetermined delay duration; and

using the calculated time of flight and respective the known locations of the sound- sources for which the time of flight is computed, determining the location of the sound-receiver in the specified area.

Some embodiments of the invention relate to devices for determining the location of a sound-receiver in a specified area, comprising: at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate;

a plurality of sound-sources located in a specified area, configured to receive the synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of the synchronizing signal;

a sound-receiver located in the specified area, configured to receive the synchronizing signal and at least two of the sound signals transmitted by the sound-sources;

a time-of-flight computing module, functionally associated with the receiver and configured to compute a time of flight of at least some of the sound signals received by the sound-receiver based on time of receipt of the synchronizing signal, time of receipt of the sound signals, and on a respective the predetermined delay duration; and a location determining module functionally associated with the time-of-flight computing module and configured to use the calculated time of flight and respective locations in the specified area of the sound-sources in for which the time of flight is computed to determine the location of the sound-receiver in the specified area.

Some embodiments of the invention relate to devices for providing signals useful in determining the location of a receiver in a specified area, comprising:

at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate; and

a plurality of sound-sources located in a specified area, configured to receive the synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of the synchronizing signal.

Some embodiments of the invention relate to devices for determining the location of a sound-receiver in a specified area, comprising:

a sound-receiver located in a specified area configured to receive a synchronizing signal and at least two sound signals transmitted by at least two sound-sources located in the specified area, each of the at least two sound signals being transmitted a predetermined delay duration after the receipt of the synchronizing signal by the at least two sound-sources;

a time-of-flight computing module, functionally associated with the sound-receiver and configured to compute the time of flight of at least some of the sound signals received by the sound-receiver based on time of receipt of the synchronizing signal, times of receipt of the sound signals, and on a respective the predetermined delay duration; and a location determining module functionally associated with the time-of-flight computing module and configured to use the calculated time of flight and respective the locations in the specified area of the sound-sources for which the time of flight is computed to determine the location of the sound-receiver in the specified area.

Typical implementations of the teachings herein include:

a) location-determination of a person for location-dependent personalized advertisement and other location-based services;

b) location-determination of a person in a conference hall, for example to seeking a specific stand;

c) location-determination of a person in an exhibit, for example to provide content related to the exhibit;

d) location-determination of a supermarket trolley to know where and how long a person is found at a specific display in a supermarket;

e) location-determination of a sports-person during a competition (e.g., to determine offsides, a winner or to allow accurate display of clever tactics);

f) location-determination of a rescue worker in low-visibility conditions (e.g., firepersons, search-teams);

g) location-determination of a mechanical device (e.g., robot) or person (e.g., a visually impaired person), for example along a track or in a specified area; and

h) monitoring of livestock and other farming products (e.g., beehives).

The principles, uses and implementations of the teachings of the invention may be better understood with reference to the accompanying description and figures. Upon perusal of the description and figures present herein, one skilled in the art is able to implement the teachings of the invention without undue effort or experimentation. In the figures, like reference numerals refer to like parts throughout.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth herein. The invention is capable of other embodiments or of being practiced or carried out in various ways. The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting.

As discussed in the introduction, indoor positioning systems using time of flight to determine position often require complex synchronization mechanisms in order to provide accurate results. Reference is now made to Figure 1A, which is a schematic depiction of an embodiment of a sound-source according to the teachings herein.

As seen in Figure 1A, and ultrasonic sound-source 10 comprises a receiver 12, a processor 14, and a sound emitter 16, such as a speaker. In some embodiments, sound-source 10 also includes a clock 18.

As will be described in further detail hereinbelow with reference to Figure 3, for use, receiver 12 of sound-source 10 is configured to receive a synchronizing signal. Processor 14 of sound-source 10 waits a predetermined delay duration, measured using clock 18, after receipt of the synchronizing signal, following which sound- source 10 uses sound emitter 16 to transmit a discrete sound signal indicated by reference numeral 19.

Sound signal 19 has a defined base frequency and is transmitted at a well defined start time, which may be defined independently, but in some embodiments is defined with respect to a time of receipt of the synchronizing signal, i.e., a predetermined delay duration after receipt of the synchronizing signal. In some embodiments, the predetermined delay duration is zero, that is, the sound signal is transmitted substantially immediately upon receipt of the synchronizing signal.

In some embodiments when multiple sound-sources 10 are deployed in the same area, as described with reference to Figure 3, each sound- source 10 generates a sound-signal 19 at a predetermined delay duration after receipt of the synchronizing signal. In some such embodiments, at least two sound-sources 10 deployed in the same area have the same predetermined delay duration. That said, in some such embodiments, at least one sound- source 10 has a predetermined delay duration different from at least one other sound- source 10 deployed in the same area. In some embodiments, all sound- sources 10 deployed in the same area have the same predetermined delay duration. In some embodiments, each sound- source 10 deployed in the same area has a unique predetermined delay duration different from the predetermined delay duration of all the other sound -sources deployed in the same area.

In some embodiments when multiple sound-sources 10 are deployed in the same area, as described with reference to Figure 3, a sound signal transmitted from each sound-source 10 has characteristics identifying from which sound- source 10 the sound signal 19 was transmitted. In some embodiments, an identifying characteristic comprises a base frequency, in some embodiments a unique base frequency. In some embodiments, an identifying characteristic comprises a modulation, in some embodiments a unique modulation. In some embodiments, an identifying characteristic is a signal duration, in some embodiments a unique signal duration. In some embodiments, an identifying characteristic comprises a combination of at least two of a base frequency, a modulation and a signal duration.

The base frequency is any suitable base frequency. That said, in order to avoid causing distress or nuisance, it is preferred that a base frequency be higher than normally detectable to a human, e.g. at least 18 kHz. For practical reasons, including the availability of cheap off-the shelf components as opposed to expensive dedicated components, the base frequency is typically between 18 kHz and 24 kHz, more typically between 21 kHz and 24 kHz.

As mentioned above, in some embodiments when multiple sound- sources 10 are deployed in the same area, as described with reference to Figure 3, each sound-source 10 generates a sound-signal at a unique base frequency, which is different from the base frequency of other sound- sources 10. In some embodiments, sound- source 10 transmits a sound-signal at a specified base frequency that does not change. In some embodiments, the base-frequency of sound- signals generated by sound-source 10 changes with time.

The duration of a specific discrete sound-signal is any suitable duration. That said, it is preferred that the duration be short to reduce distress or nuisance. Accordingly, the duration of a specific discrete sound-signal is typically not more than about 100 microseconds, not more than about 50 microseconds, and even not more than about 20 microseconds. In some embodiments, the duration is between 1 and 10 microseconds.

As mentioned above, in some embodiments when multiple sound-sources are deployed in the same area, as described with reference to Figure 3, each sound-source 10 generates a sound-signal having a unique duration different from the duration of sound- signals of other sound-sources 10. In some embodiments, sound- source 10 generates a sound- signal having a duration that does not change. In some embodiments, the duration of sound- signals generated by a given sound-source 10 changes with time.

As noted above, a single sound-source recurrently generates a discrete sound-signal. In some embodiments, generation is intermittent. For simplicity and practical reasons, in some embodiments sound-signal generation is periodic. In some embodiments, the actual repetition rate is typically less frequent than a certain maximum repetition rate that is determined as a function of sound- signal duration and maximal range from a sound-source: it is preferred to ensure that a sound-receiver at the furthest range from a sound-source receives a sound-signal before a succeeding sound-signal is generated in order to avoid possible confusion between two succeeding signals and also possible echoes. A typical maximal repetition rate is about 5 Hz (5 sound-signals per second). That said, to reduce distress or nuisance, an actual repetition rate is typically slower than 5 Hz and determined by the practical needs of a specific embodiments. For example, in some livestock monitoring embodiments the actual repetition rate is around 1 minute"1. For example, in some embodiments where the location of a supermarket trolley is monitored, the actual repetition rate is around 1 Hz. For example, in some embodiments where the location of sportspersons is monitored, the actual repetition rate is preferably the maximal repetition rate around 5 Hz, or even more frequent.

The intensity of a discrete sound-signal is any suitable intensity. Typically the intensity is as low as possible to reduce distress or nuisance, but must be sufficient so as to be detectable at a desired maximal range. Typical base frequencies are such that it is unlikely that background noise drowns-out the sound- signals. That said, in some embodiments, interfering background noise may be a factor to consider when determining a suitable intensity.

In some embodiments, as shown in Figure IB, the sound-source 10 also includes a transmitter 20 for transmission of electromagnetic radiation signals. As seen in Figure IB, the sound-source 10 is implemented using Wi-Fi infrastructure. Although non-intuitive, the use of Wi-Fi infrastructure allows simple implementation of the teachings herein using readily- available hardware components without requiring investment in a dedicated infrastructure.

In the illustrated embodiment, the sound-source 10 is a modified Wi-Fi access point 22. When deployed, sound-source 10 functions as a standard access point managing and maintaining Wi-Fi sessions as known in the art, including the recurrent transmission of beacon frames 24. Additionally, functionally associated speaker 16, such as a piezoelectric speaker, is configured to be triggered to generate a sound-signal 19 as described in reference to Figure 1A.

Modified access point 22 is also configured to add information necessary and/or useful for implementing the teachings herein to the transmitted beacon frames 24, for example using beacon stuffing as described in "Beacon-Stuffing: Wi-Fi Without Associations" published on the Internet by Microsoft Research, authored by R. Chandra, J. Padhye, L. Ravindranath, A. Wolman, 2007. Beacon stuffing may be carried out, for example, by SSID concatenation, BSSID concatenation, or by overloading a beacon frame Information Element (IE). It is appreciated that it is possible to overload IEEE 802.11 beacon frames without breaking the standard. The information included in a beacon frame 24 used in implementing the teachings herein typically includes:

an identifier of sound-source 10, often indicating that the sound-source is implementing aspects of the teachings herein,

the physical coordinates, typically including height, of sound-source 10, when deployed, and more specifically, the physical coordinates of speaker 16,

the base-frequency of a sound-signal 19 that speaker 16 generates,

the duration of such a sound-signal 19,

the modulation of such a sound-signal 19, and

a start-time schedule of start times of transmission of the next sound-signals, for example, for generation of the next three sound-signals, which start time may be expressed as an offset in milliseconds relative to the sound-source internal clock, an offset in milliseconds relative to a previously transmitted sound-signal, or an offset in milliseconds relative to receipt of a synchronizing signal.

Turning to the specifics of operation of sound-source 10 as a modified Wi-Fi access point 22, beacon frames 24 are broadcast according to a Beacon Interval Parameter specified in a Wi-Fi configuration 26 forming part of processor 14, typically in the form of a configuration file.

In some embodiments, a Beacon Synchronizer 28 forming part of processor 14 is implemented as a Linux kernel service or as a designated module within an open source router (e.g. Click Modular Router) that accesses Wi-Fi configuration 26 to retrieve the Beacon Interval Parameter. Alternatively, in some embodiment Beacon Synchronizer 28 is unaware of the Beacon Interval Parameter.

In some embodiments, a Wi-Fi Interface 30 software driver of sound-source 10 may be modified so that services and threads are able to enlist themselves to receive callbacks whenever a beacon frame 24 is broadcast from Wi-Fi Interface 30. In such embodiments, Beacon Synchronizer 28 calculates the Beacon Interval Parameter and performs various tasks subsequent to broadcast of a beacon frame 24. In some embodiments, in which a sound-signal is transmitted after each beacon frame broadcast, upon receiving a callback, indicating that a beacon frame 24 was broadcast or is about to be broadcast, Beacon Synchronizer 28 activates speaker 16 to transmit a sound-signal, as indicated at reference numeral 31.

As mentioned above, in embodiments where there is more than one sound-source 10, Beacon Synchronizer 28 optionally embeds information concerning characteristics of sound- signal 19 generated by sound-source 10 in broadcast beacon frames 24, in accordance with the teachings herein.

Reference is now made to Figure 2, which is a schematic depiction of an embodiment of a sound-receiver according to the teachings herein.

A sound-receiver according to the teachings herein is a device comprising a microphone, a radio-receiver, a processor and a clock. In some embodiments such a device is custom-made to implement the teachings herein. In some embodiments, such as that illustrated in Figure 2, the device is a suitably-modified known device, for example, a mobile communication device (Wi-Fi enabled cellphone, PDA, smartphone, mobile computer, Bluetooth® earphone), typically only software-modified (not hardware -modified) allowing simple and advantageous implementation of the teachings herein with the use of a preexisting and ubiquitous hardware infrastructure.

As seen in Figure 2, a sound-receiver 200, here illustrated as a suitably modified smart phone, such as a Ϊ7500 "Galaxy" smartphone by Samsung Inc, of Seoul, South Korea, which includes a sound-signal sensor 202, a radio receiver 204, a processor 206, and a clock 208.

However, any suitably-configured device that can detect a generated sound-signal and can receive radiofrequency transmission may take advantage of the teachings herein as a sound-receiver to determine an own location. Preferably, the sound-receiver is a Wi-Fi enabled device including a microphone such as a smartphone, cellular telephone, computer or PDA that is software-modified to implement the teachings herein, in some embodiments including a GNSS receiver.

In some embodiments, the radio receiver 204 comprises a Wi-Fi Interface to a network card, configured for Wi-Fi communication according to the IEEE 802.11 standard. For example, the Wi-Fi interface may be an open source software driver, modified by a person having ordinary skilled in the art to perform various tasks when a broadcast beacon frame, such as a beacon frame 24 of Figure IB, is received.

In some embodiments the sound-signal sensor 202, which may be, for example, a software driver to a microphone of sound-receiver 200, is modified to receive sound signals transmitted by sound- sources according to the teachings herein, such as sound- sources 10 of Figures 1A and IB, and specifically to receive sound signals having a frequency in the range of 18kHz - 24 kHz.

For use, sound-receiver 200 is activated to implement the teachings herein, scans the Wi-Fi radio frequencies in the usual way for beacon frames, and monitors the microphone input for sound signals. Upon receipt of a beacon frame by radio receiver 204 or of a sound signal by sound signal sensor 202 in accordance with the teachings herein, processor 206 activates a time-stamper 210 to associate a time stamp, determined using clock 208, with the received beacon frame or sound signal.

In some embodiments, processor 206 stores the time stamps in an Arrival Dataset 212 of a sound-receiver database 214, implemented, for example, as a SQL relational database, where Arrival Dataset 212 is implemented as one or more database tables.

In some embodiments, sound-receiver database 214 is populated with information regarding the characteristics of sound signals received from different sound-sources prior to use of sound-receiver 202. In some such embodiments, upon receipt of a sound signal and identification of its characteristics, such as frequency, modulation, and/or duration, a sound- source identifier 216 extracts information from database 214 for association of the specific sound signal with a sound-source which transmitted the sound signal.

In some embodiment, in which information regarding the sound signal is transmitted in a beacon frame, as described hereinabove with reference to Figure IB, sound-receiver 200 applies an inverse decoding mechanism of a Beacon-Stuffing Interpreter 218 to extract information included in the beacon frame, thereby allowing sound-source identifier 216 to associate a received sound-signal with a respective beacon frame and/or with a respective sound-source.

For example, upon receiving a beacon frame by the Wi-Fi Interface, Beacon-Stuffing Interpreter 218 may extract characteristics of the associated sound- signal encoded in the beacon frame.

It is appreciated that received beacon frames may be interrogated for information included therein without establishing a Wi-Fi session. It is important to note, that in some embodiments a suitably configured sound received 200 is able to optionally establish a Wi-Fi session if desired, unrelated to the teachings herein.

In general, following receipt of a sound-signal transmitted by a specific sound-source, having knowledge of the start time of that sound-signal and being synchronized with the sound-source, sound-receiver 200 can accurately calculate the distance to the sound-source based on the speed of sound. In some embodiments, the distance is reported. In some embodiments, the distance, taken together with an available known location of the sound- receiver and/or an available map is used to determine the location of the sound-receiver and reported. Specifically, in some embodiments, following association of a sound signal with a beacon frame and/or a sound-source, processor 206 stores an entry indicating such association in Arrival Dataset 212 in Sound-Receiver Database 214. Sound-receiver database 214 allows for retrieval of the time stamp of receipt of a specific sound signal as well as retrieval of sound-source information for that sound signal and beacon frame data associated with that sound signal. Such information, allows for computation of the distance between the sound-receiver 200 and a sound-source from which a sound signal was received.

Specifically, using such information, finding the time difference between receipt of a beacon frame and receipt of a corresponding sound signal is trivial. Additionally, information regarding the sound-source indicates how long after broadcast of the beacon frame the sound- source transmits a signal, which number can be subtracted from the time difference between receipt of the beacon frame and receipt of the sound signal, thereby providing the time of flight of the sound signal.

Since the frequency of the sound-signal and the speed of sound are known, a distance calculator 220, for example implemented as a separate process or thread running in processor 206 calculates the distance of sound-receiver 200 from a sound-source transmitting the sound signal using the formula dt*vs, where dt is the time difference and vs is the speed of sound.

In some embodiments, sound-receiver 200 includes a velocity calculating process 222 configured to calculate the velocity of sound-receiver 200 relative to a sound-source using Doppler shift of a received sound-signal as follows: f = fO *(vs + vr) / vs , where vr is the relative velocity, f is the received frequency and fO is the base-frequency of the sound signal. Since f is measurable by Sound-Signal Sensor 212 and fO can be obtained as part of the information obtained from the beacon frame or from sound-receiver database 214, calculating vr is simple.

To continuously update the current location of sound-receiver 200, in some embodiments, processor 206 runs a location calculator 224, for example implemented as a separate process or thread, which periodically receives updated distances of the sound- receiver from a corresponding sound-source as calculated by the distance calculator.

Location calculator 224 may implement any suitable method known in the art, for example, trilateration, weighted average or other methods. Upon completing a location calculation, location calculator 224 stores the output for immediate use, for example, by a location-based service application running on sound-receiver 200. Alternatively or additionally, location calculator 224 attaches a timestamp and stores the location in sound-receiver database 214, for use by location-dependent applications, such as an application showing the sound-receiver 200 path superimposed on a map.

It is appreciated that in some embodiments, the location of the sound-receiver may be calculated using methods other than time-of-flight calculations, such as Time Difference of Arrival (TDOA) calculations and radiolocation calculations.

The determined location of the signal sound sensor 202 of sound-receiver 200 is optionally reported to the user of sound-receiver 200, for example on display screen 225, or to some external location, e.g., using a Wi-Fi session, Bluetooth® or cellular telephony.

In some embodiments, sound-receiver 200 includes a transmitter 226, configured to transmit time stamp information relating to receipt of beacon frames and/or sound signals, to a remote server. In some such embodiments, some or all of the calculations, such as time of flight, distance, and/or location calculations, are carried out by the remote server.

In some embodiments, in which sound-receiver 200 receives a sound signal schedule for one or more sound-sources, such as by extracting a sound signal schedule from beacon frame or by such information being included in database 214, sound-receiver 200 calculates a reception schedule of times of expected sound-signal reception, where each entry in the schedule may include any or all of the start time of the sound-signal, the base frequency, the duration of the sound-signal and the coordinates of the sound-source that generates the sound-signal, depending on information available to sound server 200. The start time of a given discrete sound-signal in the reception schedule is calculated relative to internal clock 208 of sound-receiver 200 with reference to the start times listed in the sound signal schedule.

In some such embodiments, the sound schedule references a GNSS clock, and the reception schedule is calculated by sound-receiver 200 relative to the GNSS clock.

In parallel, sound-receiver 200 monitors sound signal sensor 202 with reference to the reception schedule. Specifically, sound signal sensor 202 is monitored at expected times for sound-signals that appears in the reception schedule. The distance to each sound-source is calculated by the difference in the start time of a given discrete sound-signal as listed in the reception schedule and the actual time the sound-signal was received by sound signal sensor 202. The identity of which sound- source generated a received sound- signal is determined with reference to reception time, frequency (e.g., base frequency±30Hz), modulation, and duration (e.g., expected duration ±10%), as described hereinabove. Reference is now made to Figure 3, which is a schematic depiction of an embodiment of a method for determining the location of a sound-receiver using Wi-Fi and ultrasound infrastructure according to the teachings herein.

As seen in Figure 3, a user 300 holding a sound-receiver 302, similar to sound- receiver 200 of Figure 2, is located in a room 304, such as a conference hall or exhibit room. In some embodiments, the size of the specified area in which the object is located, which in the illustrated embodiment is room 304, is between 1 m2 to 10000 m2.

It is appreciated that a sound-receiver 302 may be mounted onto any object for which location determination is desired. In some embodiments, the size of the object for which location is determined is in the order of 1 cm - 200 cm.

In some embodiments, the object, here shown as user 300, moves within the specified area with a velocity of up to about 10 km/h (2.8 m/sec).

Also located in room 304 are a plurality of sound-sources 306, similar to sound- sources 10 described hereinabove in reference to Figures 1 A and IB, and a synchronizer 308.

The synchronizer 308 may be an electromagnetic frequency transmitter, which typically transmits radiation having radiofrequency, but in some embodiments transmits other frequencies such as infrared frequencies. The synchronizer 308 recurrently (in some embodiments intermittently, in some embodiments periodically) transmits a synchronizing signal allowing a sound-receiver 302 to be synchronized with the one or more sound-sources 306. The synchronizing signal is typically transmitted in a synchronizing rate.

It is appreciated that the synchronizing signal is selected so that it will be received by all the sound-sources 306 substantially instantaneously, so that the distances between sound- sources 306 and synchronizer 308 would not affect the time the synchronizing signal was received.

In some embodiments, the synchronizing signal comprises an electromagnetic radiation transmission, such as an infrared radiation transmission or a radiofrequency transmission. In some embodiments, the synchronizing signal comprises a change of phase in the electrical current supplying power to sound-sources 306. In some embodiments, the synchronizing signal comprises a signal transmitted as a 3G or 4G telephony system beacon.

In the illustrated embodiment, synchronizer 308 comprises a Wi-Fi access point, and transmits a Wi-Fi beacon frame 310 as the synchronizing signal. It is appreciated that radio frequency transmissions, such as Wi-Fi beacon frames that travel substantially at the speed of light, 10 meters in 33 nanoseconds. Thus, the Wi-Fi beacon frame 310 is considered to be received instantaneously at all the sound-sources 306 and at sound-receiver 302, thereby synchronizing the sound-sources with the sound-receiver and with each other. Upon receipt of the Wi-Fi synchronizing signal, sound-receiver 302 time-stamps the time of receipt of the synchronizing signal.

In some embodiments, information necessary and/or useful for implementing the teachings herein is added to the transmitted beacon frame 310, for example using beacon stuffing, as mentioned hereinabove. The information included in a beacon frame 310, for implementing the teachings herein, typically includes:

the physical coordinates, typically including height, of sound-sources 306, and more specifically, the physical coordinates of the speaker of each such sound-source,

the base-frequency of a sound-signal transmitted by each of sound-sources 306 the duration of a sound-signal transmitted by each of sound-sources 306,

the modulation of a sound-signal transmitted by each of sound-sources 306,

a sound-signal schedule for sound signals transmitted by each of sound-sources 306, and

the predetermined delay duration between receipt of the synchronizing signal and transmission of a sound signal with respect to each of sound-sources 306.

In some embodiments, the location information for sound-sources 306 comprises absolute location information, and in other embodiments the location information comprises relative location information. For example, the location of a sound-source 306 may be indicated relative to the location of synchronizer 308 or relative to a predetermined point in room 304, e.g. the door.

In some embodiments, the sound signal schedule is relative to a local clock, e.g. a clock of one or more of sound-sources 306 or of synchronizer 308.

In some embodiments, the synchronization information is relative to an external clock, e.g., UTC (coordinated universal time), TAI (International Atomic Time), PTP according to the IEEE 1588 standard (accuracy of better than 1 microsecond), or a GNSS clock, in outdoors-embodiments received from one or more satellites or a reference clock (e.g., atomic clock) received, for example, through a Wi-Fi protocol or a telephony protocol (GPRS, 2G, 3G, 4G, NITZ).

It is important to note that the greater the accuracy of synchronization, the more accurately the distance between a sound-receiver and sound-source can be calculated. Similarly, the more accurately the start-time is defined (that is to say, the closer the sound- source generates the signal to the scheduled start-time) the more accurately the distance between a sound-receiver and sound-source can be calculated. For example, to achieve a distance accuracy of ~1 cm, it is necessary that the synchronization be ~30 microseconds.

As discussed hereinabove with reference to Figures 1A and IB, upon receipt of a synchronizing signal from synchronizer 308, each of sound-sources 306 waits a predetermined delay duration, and then transmits a sound signal 312. As discussed hereinabove, the delay duration may be unique to each sound-source 306, or may be common to two or more sound- sources, and may be of any duration, including duration zero.

Sound-receiver 302 receives sound signals 312 transmitted by some or all of sound- sources 306, and time-stamps the time at which the sound signals were received. In the illustrated embodiment, sound-receiver 302 receives sound signals transmitted by sound- sources 306a, 306b, and 306c, but does not receive sound signals transmitted by sound- sources 306d and 306e. As discussed hereinabove with reference to Figures 1A and IB, each sound signal 312 transmitted by each of the sound-sources 306 has one or more unique characteristics which enable sound-receiver 302, upon receipt of a specific sound signal 312 and, in some cases, access to additional data, to identify which of the sound-sources 306 transmitted the received signal. The identification may be based on the duration of the sound signal, the modulation of the sound signal, the base frequency of the sound signal or combinations thereof.

In some embodiments, the additional data indicating the association between one or more signal characteristics and the sound-source that transmits signals having those characteristics is obtained from a pre-populated dataset included in sound-receiver 302.

In some embodiments, the additional data indicating the association between one or more signal characteristics and the sound-source that transmits signals having those characteristics is embedded in a beacon frame, such as beacon frame 310 transmitted by synchronizer 308, or a beacon frame transmitted by a sound-source as described hereinabove with reference to Figure IB, and is retrieved by sound-receiver 302 as described hereinabove in reference to Figure 2.

In some embodiments, the additional data indicating the association between one or more signal characteristics and the sound-source that transmits signals having those characteristics is obtained from a database at a remote location from the sound-receiver 302, by sound-receiver 302 communicating with a remote server housing the database using any suitable communication method such as a Wi-Fi protocol or a telephony protocol (GPRS, 2G, 3G, 4G, NITZ). In some embodiments, as discussed hereinabove with reference to Figure 2, once sound-receiver 302 identifies a sound-source 306 from which each received sound signal 312 was transmitted, sound-receiver 302 accesses additional data regarding that sound-source 306. The additional information typically includes the coordinates of sound-source 306 and the predetermined delay duration of sound-source 306. As mentioned hereinabove, the additional data may be obtained from a pre-populated database included in sound-receiver 302, from a beacon frame, or from a remote database.

Subsequently, the time of flight of each sound signal received by sound-receiver 302 is computed. Since the time at which the synchronizing signal was received (Tsynch), the time at which the sound signal was received (TSOUnd), and the predetermined delay duration (D) are all known, the time of flight (ToF) of the sound signal is given by the formula:

ToF = T synch + D - T sound-

Since the frequency of the sound-signal and the speed of sound are known, once the time of flight of a given sound signal is known, the distance between the sound-source 306 from which the sound signal was transmitted and sound-receiver 302 is calculated using the formula dt*vs, where dt is the time of flight, and vs is the speed of sound. In some embodiments, the determination of distance between a sound-source and a sound-receiver is recurrent, e.g., in some embodiments at a rate of 10 Hz to 0.01 Hz.

An aspect of some embodiments described herein is that synchronization signal 310 and a sound-signals 312 travel through the air at different speeds (speed of light vs. speed of sound) and therefore are received by sound-receiver 302 at different times. Thus, even if the clocks of sound-source 306 and sound-receiver 302 are not synchronized, the time required for a generated sound-signal 312 to reach sound-receiver 302, and thus the distance between sound-source 306 and sound-receiver 302 can be calculated with great accuracy.

In embodiments including at least two sound-sources, such as the illustrated embodiment, the distances to the at least two sound-sources are determined in the same way. The location of the sound-receiver is determined from the at least two (preferably at least three) determined distances using trilateration, and in some embodiments, taken together with an available known location of the sound-receivers and/or an available map. In some embodiments, the location is reported. Methods for implementing trilateration are well known, see for example, Manolakis, D.E. IEEE Trans Aerospace Elec Sys 1996, 32(4), 1239 or "Understanding GPS: Principles and Applications, Kaplan E and Hegraty C (editors) 2006 Artech House Inc. (ISBN 1-58053-894-0) Typically, the speed of sound for distance calculations is taken at some standard value. In some embodiments, the speed of sound in the area is monitored and used for calculations. In some embodiments, factors such as ambient temperature, pressure and altitude are measured and the speed of sound for distance calculations is corrected accordingly.

The distance taken together with knowledge of the location (physical coordinates) of the sound-sources 306, allows the location of sound-receiver 302 to be accurately determined, in some embodiments, within 10 cm, within 5 cm and even within 1 cm.

In some embodiments, the time of flight calculations, distance calculations, and location calculation are all carried out at sound-receiver 302.

In some embodiments, sound-receiver 302 transmits information regarding the received synchronizing signal and the received sound signals, such as a time stamp of receipt of the synchronizing signal, time stamp of receipt of the sound signals, and duration, modulation, and frequencies of the sound signals, to a remote server, for example using a Wi- Fi communication protocol or a telephony communication protocol. In some such embodiments, the time of flight calculations, distance calculations, and location calculations are all carried out at the remote server.

In some embodiments, some of the time of flight, distance, and location calculations are carried out at sound-receiver 302, and calculations not carried out at the sound-receiver are carried out at the remote server.

It is appreciated that in some embodiments, there is only a single deployed sound- source so that the location determined in accordance with the teachings herein is a range from the sound-source. Such embodiments are useful, for example, for determining location in a substantially linear area (e.g., buildings with hallways or well-defined passageways, in tunnels). Such embodiments are also useful, for determining proximity location, for example, in the field of livestock control where the sound-receivers are secured to livestock confined in an area in some way (e.g., by the presence of a fence) and the location as determined in accordance with the teachings herein primarily to ensure that the sound-receivers do not leave (or are taken) from the area.

As discussed hereinabove with reference to Figure 2, in some embodiments, the calculated position may be stored in sound-receiver 302 for future use.

In some embodiments, the calculated location is displayed to user 300 on a display, such as screen 314 of sound-receiver 302, and may be displayed as overlayed on a map for user 300 to more easily identify his location. In some embodiments, the calculated location is transmitted to a remote location, such as a server. For example, in an embodiment in which user 300 is located in a supermarket, the calculated location may be transmitted to the supermarket management for use in their advertising and decisions regarding placement of products.

It is appreciated that in some embodiments, some or all of sound-sources 306 are mobile, for example, are fixed to motor vehicles or other movable objects, and the exact area in which the location of a sound-receiver is determined, is defined ad hoc. Such embodiments are useful, for example, in emergency and civil defense implementations. For example, sound-sources 306 are mounted on fire-engines, ambulances, police cars and other official vehicles, sound-receivers such as 302 are carried by rescue personnel, and the teachings herein are used to monitor the position of the rescue personnel.

Embodiment using multiple synchronizers

In some embodiments, the area in which location determination is desired is too large for a single synchronizer to synchronize all the sound-sources and the sound-receiver. This may occur for example in an airport, or in an indoor location with multiple floors, such as a mall or a hotel.

In such embodiments, multiple synchronizers are used, where one of the synchronizers is a control, or "master" synchronizer, and the other synchronizers are "slave" synchronizers.

In order to provide a synchronizing signal to the sound-sources and sound-receiver, the master synchronizer transmits a synchronizer synchronizing signal to all the slave synchronizers. Immediately upon receipt of the synchronizer synchronizing signal, or at any other uniform, predetermined duration, each of the slave synchronizers transmits a synchronizing signal to the sound-sources and sound-receivers.

It is appreciated that the synchronizer synchronizing signal is selected so that it will be received by all the slave synchronizers substantially instantaneously, so that the distances between the slave synchronizers and the master synchronizer would not affect the time the synchronizer synchronizing signal was received and so that all the slave synchronizers transmit synchronizing signals substantially simultaneously.

In some embodiments, the synchronizer synchronizing signal comprises an electromagnetic radiation transmission, such as an infrared radiation transmission or a radiofrequency transmission. In some such embodiments, each of the synchronizers comprises a Wi-Fi access point, and the synchronizer synchronizing signal, as well as the synchronizing signals transmitted by the slave synchronizers, are Wi-Fi beacon frames.

In some embodiments, it is desired that the synchronizer synchronizing signal will not be received by the sound-sources and sound-receiver, so as to prevent misinterpretation of the synchronizer synchronizing signal which would lead to erroneous location determination. In some such embodiments, the synchronizer synchronizing signal comprises a change of phase in the electrical current supplying power to the slave synchronizers, which change of phase is distinguishable from a synchronizing signal transmitted by the slave synchronizers.

Embodiment using Bluetooth®

In an alternative embodiment, the teachings herein are implemented using a Bluetooth® infrastructure. Although non-intuitive, the use of Bluetooth® infrastructure allows simple implementation of the teachings using readily-available hardware components herein without requiring investment in a dedicated infrastructure.

In one such embodiment, the one or more sound-sources are modified Bluetooth® devices, e.g., five Satellite L735 computers by Toshiba Corporation, Minato, Tokyo, Japan in communication through a Bluetooth® piconet where one computer is the Bluetooth® master and four computers are Bluetooth® slaves. The master recurrently transmits a sound- generation schedule to all the slaves, each entry in the sound-generation schedule including a start time (relative to the master clock with which the slaves are synchronized), an identity of a single slave, the location (coordinates) of that slave, a base frequency and a duration.

Each slave receives the sound-generation schedule and generates sound-signals in accordance therewith.

Any suitably-configured device that can detect a generated sound-signal and access the information in the Bluetooth® piconet may take advantage of the sound-source as a sound-receiver to determine an own location. Preferably, the sound-receiver is a Bluetooth® enabled device including a microphone such as a Bluetooth® enabled smartphone (e.g., Ϊ7500 by Samsung, Seoul, South Korea) or earphone.

For use, the sound-receiver is activated to implement the teachings herein. The sound- receiver identifies and recurrently joins the piconet as a slave, each joining for a short time that is sufficient for downloading the sound-generation schedule.

The sound-receiver uses the information in the sound-generation schedule, as described above, to determine an own location. Motion determination

In some embodiments, the teachings herein are also used to determine the velocity vector (velocity of motion) of the sound-receiver using, for example, Doppler shift. As is known in the art, the frequency of a sound-signal produced by a sound-source detected by a sound-receiver shifts from a transmission frequency to a received frequency, the difference being a function of the relative velocity of the sound-receiver in the direction (towards or away from) the sound-source. Using simple mathematics, it is possible to calculate, for example with the help of an appropriately programmed processor found on a typical smartphone (e.g., Ϊ7500, Ϊ5700, Ϊ5800 by Samsung, Seoul, South Korea), the velocity of the sound-receiver in the direction of each sound-source. When the velocity in the direction of two or more sound-sources is known, the velocity vector of the sound-receiver in the area can be accurately calculated.

Factors allowing sufficiently accurate calculation of velocity of the sound-receiver in the direction of a sound-source using Doppler shift include the base frequency, the sound sampling rate and the expected velocity of the sound-receiver. It has been found that serendipitously, these factors are sufficient in typical consumer electronics allowing simple implementation of Doppler shift velocity determination using sound-receivers such as mobile telephones, smartphones, portable computers and Bluetooth earphones. Specifically, such consumer devices typically have a sound-card configured to sample and process microphone output at a rate of at least 44.1 kHz. Such a sampling rate is sufficient to determine velocities of around 0.3-1.5 m /sec (1-5 km/h) using Doppler shift of base frequencies as used herein (e.g., 18 kHz to 24 kHz), velocities that are relevant to preferred implementations of the teachings herein.

It is important to note that in embodiments where it is desired to determine motion of the sound-receiver using Doppler-shift the duration of a discrete signal must be at least above a certain minimum that is related to the base frequency of the discrete signal. In some such embodiments, duration is not less than about 5 microseconds, and even not less than about 10 microseconds.

In some embodiments, the teachings herein are also used to determine the velocity vector (velocity of motion) of the sound-receiver using by comparing the location determination at two points in time. As is known in the art, the velocity of an object is equal to d/t or the distance traversed / the time in which it was traversed. Thus, once the location of sound-receiver is determined, as described hereinabove, at two different time points, the distance traversed by the sound-receiver may be calculated. The time taken to traverse that distance is also known, and thus, the calculation of velocity of the sound-receiver is straightforward.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.

Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.

Claims

CLAIMS:
1. A method for determining the location of a receiver in a specified area, comprising: from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;
at a plurality of sound-sources located in a specified area, receiving said synchronizing signal;
from each of said plurality of sound-sources, at a predetermined delay duration after receipt of said synchronizing signal, transmitting a sound signal having a base frequency; at a sound-receiver located in said specified area, receiving said synchronizing signal and at least two of said sound signals transmitted by said sound-sources;
computing the time of flight of at least some of said received sound signal based on receipt of said received sound signals, receipt of said synchronizing signal, and on a respective said predetermined delay duration; and
using said calculated time of flight and respective said known locations of said sound- sources for which said time of flight is computed, determining the location of said receiver in said defined area.
2. The method of claim 1, also comprising from said synchronizer also transmitting at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
3. The method of claims 2 wherein said synchronizer comprises a Wi-Fi access point and said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said transmitting at least one of said sound signal schedule and said location information comprises embedding said at least one of said sound signal schedule and said location information in said Wi-Fi beacon frame and transmitting said Wi-Fi beacon frame.
4. The method of any of the preceding claims, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
5. The method of any of the preceding claims, wherein said sound-source is a device comprising a speaker, a radio-receiver, a processor and a clock.
6. The method of any of the preceding claims, wherein said sound-receiver is a device comprising a microphone, a radio receiver, a processor, and a clock.
7. The method of any of the preceding claims, also comprising reporting said determined location to a user interface of said sound-receiver.
8. The method of any of the preceding claims, also comprising reporting said determined location to a location remote from said sound-receiver.
9. The method of any of the preceding claims, wherein said determining said location of said receiver comprises trilateration.
10. The method of any of the preceding claims, wherein said at least one synchronizer comprises a plurality of synchronizers, one of said plurality of synchronizers comprising a control synchronizer, and said method also includes:
from said control synchronizer, generating a synchronizer synchronizing signal for synchronizing said plurality of synchronizers;
at each of said plurality of synchronizers, receiving said synchronizer synchronizing signal; and
from each of said plurality of synchronizers, transmitting a said synchronizing signal at a set duration following receipt of said synchronizer synchronizing signal.
11. The method of any of the preceding claims, also comprising said sound-receiver accessing a database to retrieve information relating to a said sound-source from which a said sound signal was received based on at least one characteristic of said sound signal.
12. The method of claim 11, wherein said information comprises at least one of:
physical coordinates of said sound-source from which said sound signal was received; a said base frequency of a said sound-signal transmitted by said sound-source from which said sound signal was received;
a duration of a said sound-signal transmitted by said sound-source from which said sound signal was received; and
a said predetermined delay duration corresponding to said sound-source from which said sound signal was received.
13. The method of any of the preceding claims, also comprising determining a velocity vector of said sound-receiver.
14. A method for providing signals useful in determining the location of a sound-receiver in a specified area, comprising:
from at least one synchronizer, transmitting a synchronizing signal at a synchronizing rate;
at a plurality of sound-sources located in known locations in a specified area, receiving said synchronizing signal; and
from each of said plurality of sound-sources, at a predetermined delay duration after receipt of said synchronizing signal, transmitting a sound signal having a base frequency.
15. The method of claim 14, also comprising from said synchronizer also transmitting at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
16. The method of claim 15 wherein said synchronizer comprises a Wi-Fi access point and said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said transmitting at least one of said sound signal schedule and said location information comprises embedding said at least one of said sound signal schedule and said location information in said Wi-Fi beacon frame and transmitting said Wi-Fi beacon frame.
17. The method of any of claims 14 to 16, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
18. The method of any of claims 14 to 17, wherein said sound-source is a device comprising a speaker, a radio-receiver, a processor and a clock.
19. The method of any of claims 14 to 18, wherein said at least one synchronizer comprises a plurality of synchronizers, one of said plurality of synchronizers comprising a control synchronizer, and said method also includes:
from said control synchronizer, generating a synchronizer synchronizing signal for synchronizing said plurality of synchronizers; at each of said plurality of synchronizers, receiving said synchronizer synchronizing signal; and
from each of said plurality of synchronizers, transmitting a said synchronizing signal at a set duration following receipt of said synchronizer synchronizing signal.
20. A method for determining the location of a sound-receiver in a specified area, comprising:
at a sound-receiver located in a specified area, receiving a synchronizing signal at a synchronizing rate;
at said sound-receiver, receiving at least two sound signals transmitted by sound- sources located in said specified area, each of said at least two sound signals having a base frequency and being transmitted from said sound-sources a predetermined delay duration after said receipt of said synchronizing signal by said sound-sources;
computing the time of flight of at least some of said received sound signals based on receipt of said received sound signals, receipt of said synchronizing signal, and on a respective said predetermined delay duration; and
using said calculated time of flight and respective said known locations of said sound- sources for which said time of flight is computed, determining the location of said sound- receiver in said specified area.
21. The method of claim 20, also comprising, at said sound-receiver also receiving at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
22. The method of claims 21 wherein said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said at least one of said sound signal schedule and said location information is embedded in said Wi-Fi beacon frame and, at said sound-receiver, receiving said Wi-Fi beacon frame.
23. The method of any of claims 20 to 22, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
24. The method of any of claims 20 to 23, wherein said sound-receiver is a device comprising a microphone, a radio receiver, a processor, and a clock.
25. The method of any of claims 20 to 24, also comprising reporting said determined location to a user interface of said sound-receiver.
26. The method of any of claims 20 to 25, also comprising reporting said determined location to a location remote from said sound-receiver.
27. The method of any of claims 20 to 26, wherein said determining said location of said receiver comprises trilateration.
28. The method of any of claims 20 to 27, also comprising said sound-receiver accessing a database to retrieve information relating to a said sound-source from which a said sound signal was received based on at least one characteristic of said sound signal.
29. The method of claim 28, wherein said information comprises at least one of:
physical coordinates of said sound-source from which said sound signal was received; a said base frequency of a said sound-signal transmitted by said sound-source from which said sound signal was received;
a duration of a said sound-signal transmitted by said sound-source from which said sound signal was received; and
a said predetermined delay duration corresponding to said sound-source from which said sound signal was received.
30. The method of any of claims 20 to 29, also comprising determining a velocity vector of said sound-receiver.
31. A device for determining the location of a sound-receiver in a specified area, comprising:
at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate; a plurality of sound-sources located in a specified area, configured to receive said synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of said synchronizing signal;
a sound-receiver located in said specified area, configured to receive said synchronizing signal and at least two of said sound signals transmitted by said sound-sources; a time-of-flight computing module, functionally associated with said receiver and configured to compute a time of flight of at least some of said sound signals received by said sound-receiver based on time of receipt of said synchronizing signal, time of receipt of said sound signals, and on a respective said predetermined delay duration; and
a location determining module functionally associated with said time-of-flight computing module and configured to use said calculated time of flight and respective locations in said specified area of said sound-sources in for which said time of flight is computed to determine the location of said sound-receiver in said specified area.
32. The device of claim 31, wherein said synchronizer is also configured to transmit at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
33. The device of claims 32 wherein said synchronizer comprises a Wi-Fi access point and said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said synchronizer is configured to embed said at least one of said sound signal schedule and said location information in said Wi-Fi beacon frame and transmitting said Wi-Fi beacon frame.
34. The device of any of claims 31 to 33, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
35. The device of any of claims 31 to 34, wherein said sound-source comprises a speaker, a radio-receiver, a processor and a clock.
36. The device of any of claims 31 to 35, wherein said sound-receiver comprises a microphone, a radio receiver, a processor, and a clock.
37. The device of any of claims 31 to 36, wherein said sound-receiver comprises a user interface, the device also comprising a reporting module configured to report said determined location to said user interface of said sound-receiver.
38. The device of any of claims 31 to 37, also comprising a reporting module configured to report said determined location to a location remote from said sound-receiver.
39. The device of any of claims 31 to 38, wherein said location determining module is configured to use trilateration to determine said location of said sound-receiver.
40. The device of any of claims 31 to 39, wherein said at least one synchronizer comprises a plurality of synchronizers, one of said plurality of synchronizers comprising a control synchronizer, wherein:
said control synchronizer is configured to generate a synchronizer synchronizing signal for synchronizing said plurality of synchronizers; and
each of said plurality of synchronizers is configured to receive said synchronizer synchronizing signal to transmit a said synchronizing signal at a set duration following receipt of said synchronizer synchronizing signal.
41. The device of any of claims 31 to 40, also comprising a database including data relating to said plurality of sound sources, wherein said sound-receiver is also configured to access said database to retrieve information relating to a said sound-source from which a said sound signal was received based on at least one characteristic of said sound signal.
42. The device of claim 41, wherein said information comprises at least one of:
physical coordinates of said sound-source from which said sound signal was received; a said base frequency of a said sound-signal transmitted by said sound-source from which said sound signal was received;
a duration of a said sound-signal transmitted by said sound-source from which said sound signal was received; and
a said predetermined delay duration corresponding to said sound-source from which said sound signal was received.
43. The device of any of claims 31 to 42, also comprising a velocity determining module configured to determine a velocity vector of said sound-receiver.
44. A device for providing signals useful in determining the location of a receiver in a specified area, comprising:
at least one synchronizer configured to transmit a synchronizing signal at a synchronizing rate; and
a plurality of sound-sources located in a specified area, configured to receive said synchronizing signal and to transmit a sound signal at a predetermined delay duration after receipt of said synchronizing signal.
45. The device of claim 44, wherein said synchronizer is also configured to transmit at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
46. The device of claim 45, wherein said synchronizer comprises a Wi-Fi access point and said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said synchronizer is configured to embed said at least one of said sound signal schedule and said location information in said Wi-Fi beacon frame and transmitting said Wi-Fi beacon frame.
47. The device of any of claims 44 to 46, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
48. The device of any of claims 44 to 47, wherein said sound-source comprises a speaker, a radio-receiver, a processor and a clock.
49. The device of any of claims 44 to 48, wherein said at least one synchronizer comprises a plurality of synchronizers, one of said plurality of synchronizers comprising a control synchronizer, wherein:
said control synchronizer is configured to generate a synchronizer synchronizing signal for synchronizing said plurality of synchronizers; and each of said plurality of synchronizers is configured to receive said synchronizer synchronizing signal to transmit a said synchronizing signal at a set duration following receipt of said synchronizer synchronizing signal.
50. A device for determining the location of a sound-receiver in a specified area, comprising:
a sound-receiver located in a specified area configured to receive a synchronizing signal and at least two sound signals transmitted by at least two sound-sources located in said specified area, each of said at least two sound signals being transmitted a predetermined delay duration after said receipt of said synchronizing signal by said at least two sound- sources;
a time-of-flight computing module, functionally associated with said sound-receiver and configured to compute the time of flight of at least some of said sound signals received by said sound-receiver based on time of receipt of said synchronizing signal, times of receipt of said sound signals, and on a respective said predetermined delay duration; and
a location determining module functionally associated with said time-of-flight computing module and configured to use said calculated time of flight and respective said locations in said specified area of said sound-sources for which said time of flight is computed to determine the location of said sound-receiver in said specified area.
51. The device of claim 50, wherein said synchronizer is also configured to transmit at least one of a sound-signal schedule and location information for at least one of said plurality of sound-sources.
52. The device of claim 51, wherein said synchronizer comprises a Wi-Fi access point and said synchronizing signal comprises a Wi-Fi beacon frame, and wherein said synchronizer is configured to embed said at least one of said sound signal schedule and said location information in said Wi-Fi beacon frame and transmitting said Wi-Fi beacon frame.
53. The device of any of claims 50 to 52, wherein each one of said sound signals has at least one characteristic identifying from which one of said plurality sound-sources said sound signal is transmitted.
54. The device of any of claims 50 to 53, wherein said sound-receiver comprises a microphone, a radio receiver, a processor, and a clock.
55. The device of any of claims 50 to 54, wherein said sound-receiver comprises a user interface, the device also comprising a reporting module configured to report said determined location to said user interface of said sound-receiver.
56. The device of any of claims 50 to 55, also comprising a reporting module configured to report said determined location to a location remote from said sound-receiver.
57. The device of any of claims 50 to 56, wherein said location determining module is configured to use trilateration to determine said location of said sound-receiver.
58. The device of any of claims 50 to 57, also comprising a database including data relating to said plurality of sound sources, wherein said sound-receiver is also configured to access said database to retrieve information relating to a said sound-source from which a said sound signal was received based on at least one characteristic of said sound signal.
59. The device of claim 58, wherein said information comprises at least one of:
physical coordinates of said sound-source from which said sound signal was received; a said base frequency of a said sound-signal transmitted by said sound-source from which said sound signal was received;
a duration of a said sound-signal transmitted by said sound-source from which said sound signal was received; and
a said predetermined delay duration corresponding to said sound-source from which said sound signal was received.
60. The device of any of claims 50 to 59, also comprising a velocity determining module configured to determine a velocity vector of said sound-receiver.
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