Abstract: Systems and methods for determining a direction and range, at a predetermined level of granularity, for a transmitting device in a communications system are presented. Determinations, based on indicia related to the signal conditions, information contained in the received signals, and/or inferences surrounding the transmission conditions can be employed in identifying a transmitter, determining the range and direction of a transmitter and/or identifying a relative location of a transmitter without relaying, retransmitting, and/or conveying the transmitted and received signal across a supporting communications network. These determinations can be formed centrally at the transmitting or receiving user equipment or mobile device or formed in a distributed manner between the transmitting and receiving user equipment or mobile devices across a communications system.

Abstract: A method for estimating the distance between a transmitter and at least one receiver. The transmitter has radio transmission circuitry, at least part of which is operable in a first operation mode for transmitting a first signal type within a first bandwidth and in a second operation mode for transmitting a second signal type including at least a ranging component which occupies a second bandwidth which encompasses and exceeds the first bandwidth. The method includes the steps of: (i) operating part of the radio transmission circuitry in a second operation mode, (ii) transmitting a signal of a second signal type, (iii) receiving a signal on one receiver and (iv) estimating the distance between the transmitter and a receiver from the ranging component in each received signal. A suitable transmitter and receiver for implementing the method are described.

Abstract: Apparatus for determining an estimated value for a location of a receiving element within a reference system which may receive signals of a signal source movable to different measuring positions, it being possible to measure—on the basis of the signals received—localization data which indicate a relative location of the receiving element with respect to the movable signal source, the apparatus being configured to determine the estimated value on the basis of at least two different measuring positions and localization data corresponding thereto by means of an evolutionary algorithm. On the basis of the localization data measured, a fitness function of the evolutionary algorithm is formed, the localization data having an angle of arrival of the received signals on the receiving element, and/or a signal arrival time from which a distance from the signal source may be determined.

Abstract: A radio frequency (RF) positioning system for positioning an RF device on a surface is provided. The RF positioning system utilizes the property of the RF device generating a response signal upon receiving an RF signal to perform positioning. The RF positioning system includes an antenna set, a switch unit, an RF module and micro-controller unit (MCU). The antenna set has a plurality of antennas in different sizes. The RF module is coupled to the switch unit. The MCU, coupled to the switch unit and the RF module, controls the switch unit to select one antenna from the antenna set and controls the RF module to generate the RF signal. The MCU further estimates a distance between the RF device and the RF positioning system according to whether the RF positioning system receives the response signal through the selected antenna.

Abstract: A mobile device in a cellular communication network collects three or more round-trip time (RTT) measurements for a single active cell. The collected RTT measurements are transmitted to a location server. The location server uses the transmitted RTT measurements to calculate a GNSS position of the single active cell. One or more of the transmitted RTT measurements are taken by the mobile device, and/or are collected from other mobile devices in the single active cell. The transmitted RTT measurements are collected at different GNSS fixes in the same single active cell. The mobile device location stamps the collected RTT measurements using corresponding GNSS fixes, and transmits to the location server using a NML. The location server calculates the GNSS position of the single active cell using location stamped RTT measurements in the received NMLR to refine an associated reference database periodically or aperiodically.

Abstract: A passive tag receiving a reader signal provided by a reader is disclosed. The passive tag includes an antenna, an oscillator circuit, and an internal chip. The antenna receives the reader signal. The reader signal is within an operation frequency band. The oscillator circuit is coupled to the antenna and generates a frequency signal. The internal chip processes the reader signal according to power provided by the reader signal and the frequency signal when the reader signal is received and the frequency signal is generated.

Abstract: An apparatus and method for determining real time location of assets by calculating the relative position of a plurality of GPS enabled devices transported together, taking advantage of multiple GPS enable devices being transported together including dual band GPS and averaging location data between US and European GPS data. Additionally, an IMB acts to receive GPS data from multiple devices in a shipment and IMB combines and averages data from both GPS systems to create more liable location determination.

Abstract: A frequency generation unit (FGU) in a communication device includes a voltage controlled oscillator (VCO), an adjustable filter having a capacitive element for wideband operation, a current source with variable gain, and chirp generation control circuitry (CGC) that is used to generate location signals. The FGU receives, from a reference device, at least one location signal control parameter that defines linear frequency slope characteristics for a location signal. The CGC configures, based on the at least one location signal control parameter, the gain and a polarity of the current source to generate a first current during a first time period for charging the capacitive element to generate a control signal that is coupled to the VCO to generate a first part of the location signal having the defined linear frequency slope characteristics, wherein the first part of the location signal is transmitted using a transceiver of the communication device.

Abstract: A system for enhancing location estimates by movable rovers including one or more base stations that engage in two way time transfer (TWTT) with the rovers. Each TWTT operation between a given base station and a given rover provides range measurements and clock differences between the base station and rover. The range measurements are based on the travel time of return TWTT signals and the clock differences are based on a phase offset of a code in the return TWTT signal and/or timing information included in the return TWTT signals.

Abstract: A proximity probe, for use in determining a distance to a probe target, includes a first antenna configured to wirelessly receive a radio-frequency signal at a first predetermined frequency and a converter configured to convert the received signal to a driving signal and to an electrical signal. The proximity probe also includes a second antenna configured to receive power via the driving signal and to generate a signal indicative of a distance from the proximity probe to the probe target, and a third antenna configured to transmit the generated signal.

Abstract: The disclosed subject matter generally relates to hybrid positioning systems and methods and, more specifically, systems and methods of detecting moved WLAN assess points using a wireless local area network based positioning system (WLAN-PS) and a satellite-based positioning system (SPS) with at least two satellites measurement.

Abstract: Methods having corresponding apparatus and tangible computer-readable media comprise: determining a plurality of first pseudoranges based on a plurality of respective wireless television signals received by an apparatus and a clock signal generated by the apparatus, wherein each of the first pseudoranges represent a difference between a time of transmission of the respective wireless television signal from a respective transmitter and a time of reception of the respective wireless television signal at the apparatus and a time offset of the clock signal; determining a plurality of first estimates of frequency offsets of the wireless television signals received by the apparatus; and determining a first estimate of a location of the apparatus based on the first pseudoranges, the first frequency offsets of the wireless television signals, and locations of the transmitters.

Abstract: The invention relates to methods and systems for accurate ranging and geo-locationing using coherent multicarrier (CM) signals and based on a high-resolution estimation of a receiver timing offset in a signal receiver that receives ranging CM signals. A transmitter transmits a ranging CM signal having a known subcarrier modulation pattern. The receiver samples the ranging CM signal it receives reflected back from an object or from the remote transmitter, and processes the sampled signal that preserves relative subcarrier phases using a high-resolution model channel response function to determine the receiver timing offset with resolution much better than the receiver sampling period. The receiver timing offset is used to determine a flight time for the ranging CM signal with high accuracy.

Abstract: The invention relates to an apparatus and method for estimating the distance between a transmitter and a receiver. A method comprising obtaining a signal from a receiver; determining whether the signal more likely propagated through a line-of-sight (LOS) radio channel or a non lme-of-sight (NLOS) radio channel; using a model including parameters selected according to the radio channel to estimate the distance between the receiver and a transmitter which sent the signal.

Abstract: A set of device parameters consisting of clock bias and position of a mobile device is determined without previous knowledge of the week number (WN) in that solutions of a set of equations derived from a least squares type weight function involving pseudoranges related to the device parameters via basic equations are attempted with a time of week (TOW) extracted from satellite signals and various week number candidates. A solution algorithm which iteratively solves the set of equations is used, each iteration step involving a linearization of the latter and resulting in corrections of the device parameters. After elimination of week numbers where the solution algorithm does not yield a solution a valid week number is selected from the remaining week numbers in that a deviation value is determined which reflects differential terms, i.e., differences between pseudorange values as measured and as derived from the set of device parameters according to the solution, e.g., by evaluation of the weight function.

Abstract: A method for monitoring and tracking the position of a subject comprises, in an exemplary embodiment, the steps of embedding a transponder into an article to be worn by the subject and installing software in a GPS-enabled receiver, such as a cell phone or the like, for synchronizing and communicating with the transponder. The receiver is to be maintained by a user, such as a guardian or the like, and stores a unique transponder code, allowing the receiver to synchronize with the transponder. The receiver may remotely activate the transponder manually or automatically, at which point the receiver triangulates the geographic position of the transponder and determines distance and direction of the transponder from the receiver in order to guide the user in the direction of the transponder. In further embodiments, the receiver communicates the subject's information and tracking code to other subscribing receivers to increase the number of searchers.

Abstract: The disclosed subject matter generally relates to hybrid positioning systems and methods and, more specifically, systems and methods of detecting moved WLAN assess points using a wireless local area network based positioning system (WLAN-PS) and a satellite-based positioning system (SPS) with at least two satellites measurement.

Abstract: The disclosed subject matter generally relates to hybrid positioning systems and methods and, more specifically, systems and methods of detecting moved WLAN assess points using a wireless local area network based positioning system (WLAN-PS) and a satellite-based positioning system (SPS) with at least two satellites measurement.

Abstract: A cooperative position location device (CPLD) that integrates a broadcast digital transmission (BDT) receiver, a data link transceiver, and a displacement sensor; a computer program product tangibly stored in computer-readable media; and associated methods for receiving and processing special codes embedded in BDT signals from a plurality of transmitters to produce time of arrival (TOA) measurements thereof; for sending and receiving special messages between cooperative position location devices (CPLDs) to produce time difference of arrival (TDOA) of common events of BDT at and time of flight (TOF) measurements between the CPLDs; and for integrating differential and relative ranges between CPLDs to a plurality of BDT transmitters and displacement measurements to yield a joint position solution of the CPLDs.

Abstract: A method localizes a set of nodes in a wireless network that includes a target node having unknown location and a set of anchor nodes having known locations. The set of anchor nodes is partitioned into subsets of anchor nodes, wherein each subset has at least three anchor nodes. A distance from the target node to each of anchor nodes in each subset is measured, to estimate possible locations of the target node. A geometric constraint is applied to each estimated location to determine valid locations, which are then filtered to determine filtered locations. The filtered locations are averaged to determine an initial estimate of the location.

Abstract: A system and method for positioning using signal transmit power, SNR of the signal receiving unit, signal receive PER or PLR, and distance relationship between the signal source and receiving unit. The system includes a ranging signal transmitting unit and receiving unit. The transmitting unit continuously transmits a fixed number of ranging signal packets using different transmit powers, and the receiving unit receives the ranging signal packets, collect statistics for the PLR at each transmit power, and calculates the distance between the transmitting unit and itself using the distance relationship. The present invention uses the reference signal source and the method for calculating relative distance to reduce the impact from the noise and environment changes on the positioning, and introduces the critical transmit power to further enhance positioning precision. With the method provided in the present invention, using a common active RFID tag achieves high precision and effective positioning.

Abstract: A method and system are disclosed for providing an estimate of a location of a user receiver device. The method and system involve emitting from at least one vehicle at least one spot beam on Earth, and receiving with the user receiver device a signal from at least one spot beam. In one or more embodiments, at least one vehicle may be a satellite and/or a pseudolite. The method and system further involve calculating with the user receiver device the estimate of the location of the user receiver device according to the user receiver device's location within at least one spot beam. In some embodiments, when the user receiver device receives signals from at least two spot beams, the user receiver device calculates the estimate of the location of the user receiver device to be located in the center of the intersection of at least two spot beams.

Abstract: An apparatus includes a transmitter and a receiver device, which includes a receiver section and a processing module. The transmitter transmits a high carrier frequency signal. The receiver section includes first and second antennas that have an antenna radiation relationship for receiving the high carrier frequency signal. A receiver module of the receiver section determines first and second signal properties of the received high carrier frequency signal. The processing module determines a position of the receiver device with respect to the transmitter based on the first and second signal properties and maps the position to a coordinate system.

Abstract: A radial-shaped wireless fence system is provided that contains one or more dogs in a user-defined area without the need for a physical fence or underground wire. The system includes a base unit and at least one collar, and is easy to set up and use. Through improved filtering of consecutive distance measurement values taken between the base unit and the collar, errant measurement values are discounted in terms of their contribution to the current estimate of the dog's distance from the base unit. These filtering techniques, in combination with improved signal strength and antenna diversity in the communication between the base unit and the collar, improve the accuracy and consistency with which the dog's distance from the base unit is tracked so that unwanted corrections are not administered to the dog.

Abstract: The disclosed subject matter generally relates to hybrid positioning systems and methods and, more specifically, systems and methods of detecting moved WLAN assess points using a wireless local area network based positioning system (WLAN-PS) and a satellite-based positioning system (SPS) with at least two satellites measurement.

Abstract: A method for efficiently performing ranging in a wireless communication network may be implemented by a mobile station. The method may include sending a ranging code to a base station. The method may also include receiving a ranging response message from the base station. The method may also include determining whether a ranging failure condition is satisfied. The ranging failure condition may relate to something other than a duration of time. The method may further include re-sending the ranging code to the base station if the ranging failure condition is satisfied.

Abstract: A method and apparatus for estimating the position of a mobile device in a multi-path environment. In one example, the method includes receiving a plurality of reference signals from a corresponding plurality of reference devices, for each reference signal, calculating expected time delay boundaries, for each reference signal, estimating a range between the device and the corresponding reference device based on a measured time delay of the reference signal falling within calculated time delay boundaries to produce a plurality of range estimates, and filtering the plurality of range estimates to generate a composite estimate of the position of the device.

Abstract: A wireless network device including: a first RF transceiver module configured to (i) for a predetermined number of times, transmit a data frame to a second RF transceiver module, and (ii) for each data frame transmitted to the second RF transceiver module, receive an acknowledgement frame from the second RF transceiver module after a respective delay period; a timing module configured to generate a timer value corresponding to an accumulated delay period, wherein the accumulated delay period corresponds to each of the respective delay periods; and a control module configured to (i) determine the predetermined number of times that the first RF transceiver transmitted the data frame to the second RF transceiver based on a resolution of the timing module, and, (ii) determine an actual delay period based on (a) the timer value and (b) the predetermined number of times.

Abstract: Distance to a modulated backscatter tag is measured with a RFID reader that measures changes in phase with frequency of modulated backscattered RF signals. Measured distances are linked to a specific tag. The effects of other sources of reflected and interfering signals are mitigated. The techniques eliminate the need for high RF bandwidth used in time-of-flight methods, and may be used with linear, limiting or other types of amplifiers in the reader receiver. Unambiguous distance to a tag may be found using the derivative of phase with RF frequency of the modulated signal backscattered by a tag. The distance to a tag can be measured with an accuracy on the order of a centimeter. The techniques utilize the characteristics of cooperative backscatter tags (transponders, labels, etc.). New readers implement the techniques which may use unmodified tags.

Abstract: In providing a wireless location communication service including a location based service to a user of a mobile device, the mobile device sends information concerning a location of the device relative to a given position in a wireless communication system. The given position may be that of a base station in the system. First information concerning a location of the base station (e.g, GPS information) is communicated to the mobile device, e.g., via broadcast. The mobile device determines second information concerning its location, e.g., based on signals from GPS satellites received thereby. The mobile device then generates relative location information based at least on the first and second information.

Abstract: A time-of-flight ranging system, such as a keyless access Control system, comprises a first part and a second part, e.g., a portable device such as a key fob. Both parts have a transceiver for effecting communication with each other. At least the first part includes a device, e.g., a processor, for determining the distance between the two parts based on time-off-light. To save power, when the two parts are a relatively great distance apart, a time-of-flight measuring device computes the time based on a relatively coarse algorithm, and when the parts are relatively close, the computation is carried-out using a more precise algorithm. The clock frequency may be reduced when the two parts are a relatively great distance apart, and increased when they are closer. Further the transmitter power may be reduced when the two parts are relatively close together and increased when they are a relatively great distance apart.

Abstract: The disclosed embodiments provide for methods and systems for transmitting a number of streams of modulation symbols by a multi-antenna transmitter. In one aspect, a method for transmitting a number of streams of modulation symbols by a multi-antenna transmitter includes the acts of transforming a first number of streams of symbols to a second number of streams of symbols, the first number being smaller than or to the second number; and transmitting the second number of streams of symbols by a transmitter having the second number of antennas.

Abstract: A method and system improves two-way radio ranging accuracy by estimating a relative clock frequency offset between a first clock X of a first transceiver and a second clock Y a second transceiver. The first transceiver transmits a first packet at time t0 received by the second transceiver at a time t1. The second transceiver transmits a second packet at a time t2 received by first transceiver at a time t3. The second transceiver transmits a third packet at a time t4 received at a time t5. The relative clock frequency offset is then ? ? ? f XY ? ? 2 ? ? f ? ( N 24 Y - N 35 X ) N 24 Y + N 35 X , where f is a nominal clock frequency of the first and second clocks, NY24 is a measured first delay between times t2 and t4 of the second clock, NX35 is a measured second delay between times t3 and t5 of the first clock X.

Abstract: A system and method for determining a position of a locus comprising a locator device for disposition at the locus; the locator device configured for receiving an electromagnetic signal from a beacon device, the locator device receiving at a distance from the beacon device within near field range of the electromagnetic signal; the locator device configured for distinguishing at least two characteristics of the electromagnetic signal sensed at the locus; the system employing the at least two characteristics to effect the determining of the position of the locus.

Abstract: Provided are a distance measuring device and a distance measuring method which can easily distinguish a reflected signal from a desired tag from an unnecessary wave so as to improve the distance measuring accuracy even when IR-UWB is used for measuring a distance. The method uses a reader ID indicated by a code string formed by P bits (P is a natural number) for identifying a base station and a tag ID indicated by a code string formed by Q bits (Q is a natural number) for identifying a radio terminal. The method generates a unique word containing P pulses, each of which is ON/OFF-modulated depending on whether each of P bits indicating the reader ID is 1 or 0. The method generates a frame containing 2 M unique words and a burst containing Q frames. The method further outputs a transmission signal containing a plurality of bursts. A radio terminal ASK-modulates the transmission signal depending on whether each of the Q bits indicating the tag ID is 1 or 0.

Abstract: The present invention provides a method and system for positioning one or more anchor nodes or one or more non-anchor nodes in one or more communication networks. A non-anchor node may be in communication with two or more anchor nodes. The method comprises determining two or more distance measurements, corresponding to raw distances of the non-anchor node from the two or more anchor nodes, at predetermined intervals of time. An estimated distance is then calculated between the two or more anchor nodes based on the two or more distance measurements. Estimated distances between a plurality of anchor nodes in the one or more communication networks is calculated in a similar manner. A partial distance matrix is then populated using the estimated distance between the plurality of anchor nodes. A plurality of geographic coordinates of the plurality of anchor nodes is reconstructed based on the partial distance matrix.

Abstract: A method for automatically identifying wireless signal quality of a region includes receiving signal quality information associated with wireless signals received by each of a plurality of mobile endpoints and receiving location information identifying locations of each of the plurality of mobile endpoints. The method also includes, based on the received signal quality information and the received location information, identifying a first region of an area, the first region having a first signal quality.

Abstract: A proximity probe, for use in determining a distance to a probe target, includes a first antenna configured to wirelessly receive a radio-frequency signal at a first predetermined frequency and a converter configured to convert the received signal to a driving signal and to an electrical signal. The proximity probe also includes a second antenna configured to receive power via the driving signal and to generate a signal indicative of a distance from the proximity probe to the probe target, and a third antenna configured to transmit the generated signal.

Abstract: A mobile device in a cellular communication network collects three or more round-trip time (RTT) measurements for a single active cell. The collected RTT measurements are transmitted to a location server. The location server uses the transmitted RTT measurements to calculate a GNSS position of the single active cell. One or more of the transmitted RTT measurements are taken by the mobile device, and/or are collected from other mobile devices in the single active cell. The transmitted RTT measurements are collected at different GNSS fixes in the same single active cell. The mobile device location stamps the collected RTT measurements using corresponding GNSS fixes, and transmits to the location server using a NML. The location server calculates the GNSS position of the single active cell using location stamped RTT measurements in the received NMLR to refine an associated reference database periodically or aperiodically.

Abstract: A wireless positioning method of a receiver is provided. Signals are received from a plurality of transmitters, propagation taps of the plurality of transmitters received from the plurality of transmitters are determined, respectively, the distance between the receiver and each of the transmitters is calculated, respectively, the weight of each of the transmitters is calculated by using each of the propagation delay tap, the distance is adjusted by using the weight of each of the transmitters, and an area, in which circles away by the adjusted distances between the receiver and each of the transmitters on the basis of each of the transmitters overlap with each other, is estimated as the location of the receiver. Thus, an error of wireless positioning according to a propagation environment can be reduced.

Abstract: A wireless positioning method of a receiver is provided. Signals are received from a plurality of transmitters, propagation taps of the plurality of transmitters received from the plurality of transmitters are determined, respectively, the distance between the receiver and each of the transmitters is calculated, respectively, the distances are corrected by using propagation delay taps of the respective transmitters to determine final distances between the receiver and each of the transmitters, and an area, in which circles away by the final distances between the receiver and each of the transmitters on the basis of the center of each of the transmitters overlap with each other, is estimated as the location of the receiver. Thus, an error of wireless positioning according to a propagation environment can be reduced.

Abstract: A system and method for determining the position and velocity of a plurality of vehicles relative to a host vehicle using GPS data. The method includes building a graph of the vehicles that define weighted baselines between each of the vehicles and the host vehicle and each of the vehicles where the weighted baselines define a geometric dilution of precision between the vehicles. The method then determines the optimal baseline between the host vehicle and each of the other vehicles using the weighted baselines based on the lowest geometric dilution of precision. The method then computes the relative position and velocity between all of the vehicles and the host vehicle using the optimal baselines.

Abstract: The present invention provides a method and system for positioning one or more anchor nodes or one or more non-anchor nodes in one or more communication networks. A non-anchor node may be in communication with two or more anchor nodes. The method comprises determining two or more distance measurements, corresponding to raw distances of the non-anchor node from the two or more anchor nodes, at predetermined intervals of time. An estimated distance is then calculated between the two or more anchor nodes based on the two or more distance measurements. Estimated distances between a plurality of anchor nodes in the one or more communication networks is calculated in a similar manner. A partial distance matrix is then populated using the estimated distance between the plurality of anchor nodes. A plurality of geographic coordinates of the plurality of anchor nodes is reconstructed based on the partial distance matrix.

Abstract: A wireless network device comprises a first RF transceiver module and a control module. The first RF transceiver module transmits a first data frame to a second RF transceiver module and receives a first acknowledgement (ACK) frame from the second RF transceiver module after a first delay period. The first RF transceiver module transmits a second data frame to the second RF transceiver module and receives the second ACK frame from the second RF transceiver module after a second delay period. The control module communicates with the first RF transceiver module and determines a total delay period based on the first and the second delay times. The control module determines an actual delay period between the first and the second RF transceiver modules based on the total delay period.

Abstract: A “synchrolite” or rebroadcasting device allows GPS or GNSS navigation signals received at one or several locations to be processed at a separate location. The signals received by the synchrolite are added to a pilot tone and then encoded with a superimposed spread-spectrum code before being rebroadcast. The superimposed code allows signals from different synchrolites to be distinguished during the navigation process.

Abstract: The present invention comprising: a first local oscillator for generating a first frequency; a second local oscillator for generating a second frequency; phase-difference setting means for setting a first phase difference between a transmission signal and an output of the aforementioned first local oscillator; phase-difference detection means for detecting a second phase difference which is the phase difference between a reception signal and an output of the aforementioned second local oscillator, and calculation means for calculating a distance to a communication counterpart from a third phase difference and a fourth phase difference which are notified by the communication counterpart, and from the aforementioned first phase difference and second phase difference, wherein the third phase difference is set to the second frequency by the communication counterpart, and the fourth phase difference is set to the first frequency by the communication counterpart.

Abstract: Systems and methods for extrapolating GPS coordinates beyond line of sight are disclosed. A coordinate extrapolation system (CES) can include a memory, a processor, and a GPS receiver. The CES can receive GPS signals and determine GPS coordinates corresponding to a location. If GPS signals are unavailable, the CES models the surface of the earth and extrapolates the GPS coordinates corresponding to the location at which GPS signals are unavailable. Methods for extrapolating the GPS coordinates and calibrating the CES are also disclosed.

Abstract: A positioning device includes an antenna, a receiving module, a processing module and an output module. The receiving module receives positioning signals transmitted from positioning satellites and a position signal of another positioning device transmitted from a ground monitoring system using the antenna. The processing module determines a position of the positioning device according to the positioning signals, and calculates a distance between the positioning device and another positioning device according to the position signal of the position device and the position signal of the another positioning device. The output module outputs the distance. A method for measuring the distance between the positioning devices is also provided.

Abstract: An object of the present invention is to achieve a position information detection system with high precision when an obstruction and a reflective object exist. A position information detection system includes a reader/writer whose position is known, a first RF chip whose position is known, and a second RF chip attached to an object to be detected; and calculates a distance between the reader/writer and the second RF chip from a first calculated distance between the reader/writer and the first RF chip, which is calculated from a signal intensity of a communication signal transmitted from the reader/writer, detected by the first RF chip, a second calculated distance between the second RF chip and the reader/writer, which is calculated from a signal intensity of a communication signal transmitted from the reader/writer, detected by the second RF chip, and a distance between the reader/writer and the first RF chip.

Abstract: A system and method for estimating the range between two devices performs two or more ranging estimates with subsequent estimates performed using a clock that is offset in phase with respect to a prior estimate. The subsequent estimate allows estimate uncertainties due to a finite clock resolution to be reduced and can yield a range estimate with a higher degree of confidence. In one embodiment, these additional ranging estimates are performed at n/N (for n=1, . . . N?1, with N>1 and a positive integer) clock-period offset introduced in the device. The clock-period offset can be implemented using a number of approaches, and the effect of clock drift in the devices due to relative clock-frequency offset can also be determined. To eliminate the bias due to clock-frequency offset, a system and method to estimate the clock-frequency offset is also presented.