Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO 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
  • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
  • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
  • G01S5/0252—Radio frequency fingerprinting
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO 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
  • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
  • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
  • G01S11/06—Systems for determining distance or velocity not using reflection or reradiation using radio waves using intensity measurements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO 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
  • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
  • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
  • G01S5/0205—Details
  • G01S5/0218—Multipath in signal reception

Definitions

• the present invention relates to the technical field of proximity detection methods and systems of a target radio transmitter, and more particularly to the location and radio guidance to this target radio transmitter.
• a number of methods and systems are known for locating a target connected object and guiding a user provided with a user equipment from its current position to that target connected object.
• satellite geolocation GPS, GLONASS, GALILEO, or BeiDou
• terrestrial geolocation using a network of sensors and / or cellular cellular network and / or access points of a local wireless network
• the location of the connected object and the user equipment is obtained separately from their respective exchanges with the deployed infrastructure.
• the user equipment makes it possible to inform from its current position on a path to the connected object.
• the techniques of the second category use parameters related to propagation of the radio signal transmitted by the connected object and received by the user equipment. These parameters, determined from the received signal, comprise information that is a function of the spatial disposition of the user equipment with respect to the connected object, making it possible to detect the proximity or distance of the latter, and possibly locate it. These techniques have the advantages, on the one hand, to do without costly means of resources and energy and other resources to be implemented and, on the other hand, to allow localization in indoor environment as in outdoor environment .
• the power of the received signal is the power of the signal measured by the user equipment.
• the RSSI is an indication of the power level of the received signal on a predefined scale ranging from a first value (no signal) to a second higher value (maximum signal).
• the values of the RSSI are generally provided by the radio layer of the user equipment and are between zero (no signal) and a maximum non-zero value of the RSSI (maximum signal).
• the variation in the power of the received signal is a function, according to a predefined model specific to the propagation environment, of the distance traveled by the electromagnetic wave and of the various obstacles that it has encountered.
• the Friis model indicates that the signal strength decreases as a function of the square of the distance to the transmitter.
• the power of the received signal thus comprises an indicator of the distance separating the user equipment from the connected object, so that it can be used to detect the proximity or distance of the connected object. It is generally accepted that a distance-increasing RSS means that we are getting closer to the target connected object, whereas a decreasing distance-based RSS means that we are getting closer to the target connected object. away from the target connected object.
• the variation of the power of the received signal as a function of the distance can thus be used to deduce an orientation / direction in which the source of the received radio signal would be located.
• the source of the signal would be in the direction of displacement when the RSS grows, and in the opposite direction on the other hand.
• a distance between the target connected object and the user equipment can be estimated from the received signal power. Estimating this distance from the power of the received signal at different positions allows, by trilateration, an approximate location of the target connected object.
• the SNR parameter quantifies the extent to which a signal is affected by the noise.
• the signal-to-noise ratio is defined by the ratio of the powers between the received signal and the noise measured in the absence of this signal.
• the values of the SNR are generally provided by the radio layer of the user equipment and are most often between two values, namely a lower bound designating a signal embedded in the noise, either because the signal is weak or because the noise is strong, and an upper bound designating a signal emerging clearly above the noise.
• the parameter SNR includes information concerning the distance separating the equipment. user of the connected object source target of the transmitted signal.
• the SNR is used for localization purposes in an indoor environment including wireless LAN (WLAN).
• WLAN wireless LAN
• the relevance of such a parameter is related to the level of the transmission power, to the detriment of the energy expended by the target connected object.
• the document Borenovic et al. (“Comparative analysis of RSSI, SNR and Noise level applicability parameters for WLAN positioning purposes", Borenovic, MN, Neskovic, AM, EUROCON 2009, DOI: 10.1109 / EURCON.2009.5167905) presents an experimental analysis of the value of using the RSSI alone, the SNR alone and the RSSI together with the SNR, by a location method based on formal neural networks, in an environment covered by a wireless local area network.
• the location method is, in this document, based on the prior registration of the radioprint (called, in English, "fingerprint”) of the signal transmitted in the location environment characterized in advance.
• a disadvantage of the known methods and systems is that they are in the majority intended for configurations where the receiver and the radio transmitter to be located are in the same environment, of interior type or outside. However, they are often in two different environments, semi-interior or semi-outdoor (one in an indoor environment and the other in an outdoor environment). Indeed, the position of a target connected object can, a priori, be unknown beforehand for the user equipment responsible for locating it and guide the user to the position of this object.
• the connected object to be located can, for example, be in an indoor or confined environment (for example, a garage, a basement parking or an apartment on a higher floor), while the equipment user is in an outdoor environment (for example, in a street in a suburban, urban, dense urban, peri-urban, or rural environment), or vice versa.
• an indoor or confined environment for example, a garage, a basement parking or an apartment on a higher floor
• the equipment user is in an outdoor environment (for example, in a street in a suburban, urban, dense urban, peri-urban, or rural environment), or vice versa.
• An object of the present invention is to provide positioning and positioning methods and systems based on proximity detection.
• Another object of the present invention is to improve the stability of the accuracy in the traffic guidance to the source of the received signal based on the power of the received signal.
• Another object of the present invention is to improve the accuracy of the location, in different types of environment, of a target connected object.
• Another object of the present invention is to provide a user equipment capable of guiding / orienting the user from his current position in an external environment to a target connected object arranged in an indoor environment.
• Another object of the present invention is to reduce the margin of error of the methods and systems of radio guidance and location based on the metric RSSI.
• Another object of the present invention is to propose a combination of metrics for the effect of a better estimate of the distance, or more generally of the proximity, of a mobile radio receiver of a target radio transmitter.
• Another object of the present invention is to provide methods and systems for radio guidance and location based on measurements of the received signal power level (RSSI) and the SNR.
• RSSI received signal power level
• ⁇ a first signal modulated by a first modulation, the first signal being transmitted with a first transmission power; ⁇ a second signal modulated by a second modulation different from the first modulation, the second signal being transmitted with a second transmission power;
• the first modulation is a spread spectrum modulation with a first spreading factor
• the second modulation is a spread spectrum modulation with a second spreading factor different from the first spreading factor
• the first modulation is a frequency swept spectrum modulation
• the first statistical value is the maximum value of the normalized power levels measured at this first distance;
• the first statistical value is the minimum value of the normalized power levels measured at that second distance;
• the first weighting coefficient is greater than the second weighting coefficient.
• this proximity index being equal to the sum of the first value weighted statistic by a first predefined nonzero weighting coefficient and the second weighted statistical value by a second predefined nonzero weighting coefficient.
• the proximity index is determined by the method of determining the variation as a function of the distance of a proximity index presented above;
• the proximity detection method further comprises a step of calculating, from the proximity index, a distance separating the target position from said predefined position, according to the following formula where k is a
• the method of proximity detection further comprises a step of locating the radio transmitter integrating:
• a radio transmitter adapted to emit a plurality of signals integrating:
• a user equipment suitable for:
• this proximity index being equal to the sum of the first statistical value weighted by a first non-zero weighting coefficient predefined and the second statistical value weighted by a second weighting coefficient non-zero predefined.
• the system further comprises a tracking server configured to define a radio guidance command for the radio transmitter, this command comprising a spread spectrum factor for modulating the first signal by a spread spectrum modulation with this signal factor. spreading;
• control further comprises a frequency of recurrence of the transmission of said plurality of signals.
• FIG. 1 schematically illustrates a user provided with a user equipment configured to detect, according to various embodiments, the proximity of a radio transmitter;
• FIG. 2 schematically illustrates the sequencing in time of a plurality of signals transmitted by radio transmitter, according to various embodiments
• FIG. 3 shows two curves illustrating the variation as a function of the distance to the target radio transmitter from the standardized power level (RSSI), respectively, of a first signal received and a second signal received, according to various modes of production ;
• RSSI standardized power level
• FIG. 4 shows two curves illustrating the variation as a function of the distance to the target radio transmitter from the normalized signal-to-noise ratio and the standardized power level of the same received signal, according to various embodiments;
• FIG. 5 shows curves illustrating the variation as a function of the distance to the target radio transmitter from a proximity index, the maximum value of a plurality of standardized power levels of received signals, and the maximum value. a plurality of normalized SNRs relating to received signals, according to various embodiments;
• FIG. 6 schematically illustrates steps of a method of proximity detection and location of a target radio transmitter, according to various embodiments.
• a radio transmitter 1 is displayed. This radio transmitter 1 is able to transmit a signal modulated by a predefined modulation. The type and / or the parameters of this modulation are, in one embodiment, remotely configurable.
• This modulation can be of different types such as amplitude modulation, frequency modulation, phase modulation, amplitude jump modulation, frequency hopping modulation, phase jump modulation. , spread spectrum modulation, multi-carrier modulation, or a combination of these modulations.
• the parameters of a modulation include, depending on the type of this modulation, for example, the carrier frequency, the spread spectrum factor, the bandwidth, the number of subcarriers.
• the modulation used by the radio transmitter 1 is, in one embodiment, a spread spectrum modulation of a predefined factor.
• the spreading factor of the transmitted signal is, in one embodiment, remotely configurable.
• a spread spectrum signal can be obtained by various techniques, such as by direct sequence, frequency hopping, or time jump, by frequency sweep, or by a combination of these techniques.
• the radio transmitter 1 uses a frequency-sweeping spread spectrum modulation (known as CSS for "Chirp Spread Spectrum”).
• Frequency-sweeping spectrum (CSS) modulation is relatively inexpensive in terms of energy, promotes good penetration of the modulated signal in indoor environments, especially buildings, and enhances the immunity of the modulated signal to the environment. Doppler effect (ie at relative speeds) and multipath attenuation.
• the principle of spread spectrum regardless of the technique used, is that the modulated output signal occupies a much larger transmission bandwidth than the bandwidth of the bandwidth information requires. based. The spectrum of the baseband information signal is thus broadened to the spectrum of the spread signal over a larger bandwidth than strictly necessary.
• the spreading factor (referred to as "Spreading Factor") is then defined as the ratio of the signal bandwidths after and before spreading.
• the radio transmitter 1 is also able to successively transmit a plurality of distinct signals, at predefined time intervals and with predefined respective transmission powers.
• the transmission power of the transmitted signal is, in one embodiment, remotely configurable.
• the time interval between two successive transmissions is, in one embodiment, configurable remotely.
• the radio transmitter 1 is able to transmit periodically in the time a sequence (or series) of signals 11-14.
• the period of time between two successive transmissions of a signal sequence 11-14 is, in one embodiment, remotely configurable.
• the sequence of signals is repeated a certain time, which is capped by the occupancy rate of the band.
• the frequency band of the radio transmitter 1 is any of the wireless communication standards (eg Wi-Fi, ZigBee, Bluetooth, mobile phone standards) or any of the "free bands”.
• the number of signals 11-14 included in the same sequence 10 as well as the parameters of each of these signals 11-14 are, in one embodiment, remotely configurable. More generally, the content of a signal sequence 11-14, as well as its duration and recurrence frequency are remotely configurable.
• the radio transmitter 1 adapts, on request, its emissions. The number, the order, the duration, and the level of the transmission power of the signals 11-14 indicated in FIG. 2 are therefore given for illustrative purposes only.
• the signal sequence 11-14 comprises signals 11-14 whose respective transmission powers are different.
• the signal sequence 11-14 comprises a plurality of spread (i.e., spread spectrum) signals 11-14 whose respective spreading factors are different.
• the plurality of signals 11-14 comprises at least two signals modulated by two different modulations (of different type or of the same type but of different parameters), and transmitted with two different respective transmission powers.
• the plurality of signals 11-14 comprises at least two spread spectrum signals with two respective different spreading factors, and transmitted with two different respective transmit powers.
• the signal sequence 11-14 comprises:
• the second spreading factor, the third spreading factor and the fourth spreading factor are substantially identical.
• the first spreading factor is different from the other three spreading factors.
• the signals 11-14 thus have a modulation diversity.
• the first spreading factor is greater, respectively, than the second spreading factor, the third spreading factor, and the fourth spreading factor so that the emitted signals 11-14 have a modulation diversity.
• the second spreading factor, the third spreading factor and the fourth spreading factor are reduced, relative to the first spreading factor.
• the second signal 12, the third signal 13 and the fourth signal 14 are transmitted in narrow band, that is to say without spread spectrum (only the first signal 11 being spread).
• the first spreading factor is substantially twice each of the other spreading factors, the latter being substantially identical.
• the first transmission power and the second transmission power are, in one embodiment, identical. Each of the third transmission power and the fourth transmission power is less than the first transmission power.
• the fourth transmission power is very small compared to the first transmission power.
• the signals 11-14 thus have a diversity in transmission power to discriminate the exact position of the target if it is invisible.
• the first transmission power, the second transmission power, the third transmission power, The emission and the fourth transmission power are, respectively, 25 mW (milliwatt), 25 mW, 3 mW and 0.5 mW.
• the second transmission power and the third transmission power are chosen so that the range of the second signal 12 emitted is substantially twice that of the third signal 13 emitted.
• the first spreading factor and the second spreading factor are chosen so that the range of the first signal 11 emitted is greater than half that of the second signal 12 emitted.
• the resolution of the position is five times thinner by passing from the first signal 11 to the fourth signal 14 and reaches the metric scale.
• the signal sequence 11-14 comprises a spreading factor spread spectrum signal 11 (for example, larger than) of at least one other signal 12-14 and, optionally, at least one transmission power signal 14 which is relatively different from at least that of another signal 11-13 (for example, lower).
• the diversity in modulation (such as spread spectrum diversity) and the diversity in transmission power that the signals 11-14 of the sequence 10 exhibit improves the resistance of all the transmitted signals ( ie as a whole) to the various causes of fading (multipath propagation, obstacles, interference, noise, or scrambling for example), and is suitable for reception-side discrimination needs.
• a modulation diversity makes it possible to combat, among other things, small-scale fading caused by multiple paths.
• the signals 11-14 emitted successively are subject to different conditions by their own characteristics, as well as by their staggering (frequencies, type and parameter (s) of modulation, power, content). At their reception at different positions, these signals 11-14 are affected to different degrees by the different causes of fading of the propagation channel, and produce an average result where the harmful effects (distortion or degradation of the signal) are damped. This advantageously has the effect of reducing fluctuations in the power of the received signal and in the signal-to-noise ratio as a function of distance.
• a user 3 equipped with a user equipment 2 is within the radio range of the radio transmitter 1.
• the example of a human user 3 traveling on foot, as shown in Figure 1, is in no way limiting in the sense that the user 3 provided with the user equipment 2 may be a human user or not (robot or drone for example) and can move by any other mode (vehicle, bicycle, motorcycle, boat, or airplane for example).
• the user equipment 2 comprises, in one embodiment, a radio receiver (or, a radio transmitter-receiver hereinafter referred to as a radio receiver), able to capture and measure various parameters of a received radio signal and a computer application configured to process the measured parameters.
• a radio receiver or, a radio transmitter-receiver hereinafter referred to as a radio receiver
• a computer application configured to process the measured parameters.
• the user equipment 2 comprises, in one embodiment, a smart phone (smartphone) integrating a computer application and a radio receiver / transmitter type Wi-Fi, HiperLAN, ZigBee, or cellular (that of a network of mobile communications).
• the radio receiver is, in one embodiment, a transceiver at 868 MHz, 915 MHz, 2450 MHz, or any other frequency band also used by the radio transmitter 1.
• this radio receiver is included in a communicating module (via Bluetooth, for example) with said computer application installed in a smart phone or in any other computer terminal (laptop, tablet or phablette).
• the user equipment 2 is configured to detect the proximity of the radio transmitter 1.
• the user equipment 2 is able to capture and measure the power level of the received signal RSSI (or, in an equivalent way, the RSS from which an RSSI is determined) of each of the signals 11 to 14.
• the measured power level of the received signal 11-14 varies within a predefined interval of the type [RSSI_Min, RSSI_Max] where RSSI_Min denotes the absence of the signal 11- 14 and RSSI_Max denotes a maximum power level.
• RSSI_Min denotes the absence of the signal 11- 14
• RSSI_Max denotes a maximum power level.
• the measured power level (RSSI) of a signal 11-14 received at a predefined distance (i.e., at a predefined position) from the radio transmitter 1 is normalized ( ie, scaled) in the range [0, 1].
• RSSI_mesence - RSSI_Min a minimum value
• RSSI_Max a maximum value
• User equipment 2 is further configured to measure the signal-to-noise ratio relative to each of the received signals 11-14.
• the measured signal-to-noise ratio SNR relative to each of the signals 11-14 varies in a predefined interval of the type [SNR_Min, SNR_Max] where SNR_Min denotes a signal whose power is little different from that of the noise and SNR_Max denotes a signal whose power contrast sharply with that of noise.
• SNR_Min denotes a signal whose power is little different from that of the noise
• SNR_Max denotes a signal whose power contrast sharply with that of noise.
• the signal-to-noise ratio SNR relating to a signal 11-14 received at a predefined distance (i.e. at a predefined position) from the radio transmitter 1 is normalized (c. A. scaled) in the range [0, 1]. To do this, suppose that the measured signal-to-noise ratio SNR varies between a minimum value SNR_Min and a maximum value SNR_Max, then the normalized signal-to-noise ratio is given by (SNR_mesence - SNR_Min) / (SNR_Max - SNR_Min).
• the RSSI power level and the signal-to-noise ratio SNR relating to a signal 11-14 received at a predefined distance from the radio transmitter 1 are normalized in the same interval.
• This interval can be the interval [0, 1] or any other interval.
• the SNR signal-to-noise ratios measured and the measured RSSI power levels are thus reduced to the same interval (or scale), for example the interval [0,1].
• SNR signal-to-noise ratios and RSSI power levels of a signal 11-14 received at successive positions of the radio transmitter 1 are normalized within the same range [0, 1] .
• the period of time between two successive sequences (i.e., the recurrence frequency of the sequence 10) is chosen in relation to the speed of movement of the user equipment 2 (assumed to be 1, 5 meters per second, when the user 3 moves on foot, 10 meters per second when the user 3 moves by car, 35 meters per second when the user 3 moves overhead).
• the period of time between two successive transmissions of the same signal 11, 12, 13 or 14 (or, the frequency of recurrence of the emission of each of the signals 11-14) is chosen according to the speed of 2.
• This transmission recurrence frequency is, in one embodiment, remotely configurable.
• the duration of a sequence 10 is defined in relation to the speed of movement of the user 3. In one embodiment, the duration of the sequence 10 is eight seconds when the user 3 moves on foot .
• the solid line curve of FIG. 3 illustrates the variation of the normalized RSSI power level in the interval [0, 1] of the first signal 11 received, as a function of the distance between the radio transmitter 1 and the User equipment 2.
• the dashed line curve of FIG. 3 illustrates the variation of the normalized RSSI power level in the interval [0, 1] of the second signal 12 received, as a function of the distance between the radio transmitter 1 and the user equipment 2.
• the solid line curve of FIG. 4 illustrates the variation of the normalized RSSI power level in the interval [0, 1] of the first received signal 11, as a function of the distance between the radio transmitter 1 and the user equipment 2.
• the dashed line curve of FIG. 4 illustrates the variation of the normal SNR signal-to-noise ratio in the interval [0, 1] relative to this same first signal 11, as a function of the distance between the radio transmitter 1 and the user equipment 2.
• These data are obtained by measuring, by the user equipment 2, at a plurality of different distances from the radio transmitter 1, the received signal power level and the signal-to-noise ratio relative to each of the signals 11-14. issued by the radio transmitter 1.
• the received signal power levels (RSSI) measured at different distances from the radio transmitter 1 are, in FIGS. 3 and 4, normalized in the interval [0, 1], so that the power level maximum of the received signal is equal to unity.
• the values of the SNR measured at different distances from the radio transmitter 1 are normalized in the interval [0, 1], so that the maximum value of the SNR is equal to unity.
• normalized SNR signal-to-noise ratio values for the received signals 11-14 are smoothed for values below a predefined threshold.
• This threshold is, for example, 0.25 (this threshold not being applied to the example of FIG. 4).
• the user equipment 2 calculates a statistical value of the normalized power levels of the received signals 11-14, measured substantially at the same distance from the radio transmitter 1 (ie substantially at the same position of the radio). user equipment 2 with respect to the radio transmitter 1). Similarly, the user equipment 2 calculates a statistical value of the normalized signal-to-noise ratios for the received signals 11-14, measured substantially at the same distance from the radio transmitter (ie substantially at the same position of the user equipment 2 with respect to the radio transmitter 1).
• the calculated statistical value may be, for example, an average value (arithmetic, geometric, harmonic or any other type of average), the median value, the maximum value, the minimum value, a weighted average value (c. assigning different weights to the SNRs and / or RSSIs of the received signals 11-14, the sum of these weights being equal to unity).
• the statistical operator used to calculate a statistical value of the SNR and / or standardized RSSI is chosen according to the distance separating the user equipment 2 from the For example, the statistical value is the maximum value when this distance is greater than a predefined distance and, is the value minimum when this distance is less than the predefined distance. In another embodiment, a statistical operator is used by distance interval.
• a first statistical value (e.g., the minimum value) is computed at distances less than a first threshold distance
• a second statistical value e.g., the average
• a third statistical value e.g., the maximum value
• the statistical operator applied to the SNRs may be different from that applied to the RSSIs.
• the maximum value and the average value can be calculated, respectively, for the power levels and the signal-to-noise ratios relating to the different signals 11-14 received at this distance.
• the user equipment 2 calculates the envelope (ie the maximum value) and applies all other operations (filtering, weighting differently the RSSIs and / or the standardized SNR of the signals 11-14) applied to the different normalized values of the RSSI and the SNR relating to the different signals 11-14 received in the same (or substantially the same) position of the user equipment 2 with respect to the radio transmitter 1.
• the curves of FIG. 5 illustrate the variation, as a function of distance, of the maximum value of the normalized power levels in the interval [0, 1] of the signals 11-14 successively received (curve in dashed line). , and the maximum value of the signal reports on noise normalized in the range [0, 1] and smoothed relative to these signals 11-14 (dotted line).
• the variation as a function of the distance of the normalized power level of the received signal and the normalized signal-to-noise ratio relate to two functions of different shape.
• Each of these two functions of the received signal power and the signal-to-noise ratio is an algebraic expression different from the distance variable separating the user equipment 2 from the source radio transmitter 1 of the received signal so that the observation of these two parameters of the received signal makes it possible to improve the accuracy of the location of the radio transmitter 1.
• a combination of these two functions can therefore be used as a proximity indicator of the radio transmitter 1, or also as an indicator on the distance separating the user equipment 2 from the radio transmitter 1.
• the proximity of the radio transmitter 1 is estimated by using together the variation as a function of the distance, the normalized power level of the received signal and the variation as a function of the distance of the signal-to-signal ratio. normalized noise.
• the variation as a function of the normalized signal-to-noise ratio (SNR) distance is, in one embodiment, approximated by a high order polynomial.
• the variation as a function of the standardized power level (RSSI) distance of the received signal assumes, for its part, a quadratic form (ie a second order polynomial whose graphic representation is a parabola) until direct view at point - blank of the radio transmitter 1.
• This approximation can also be predominant in the discrimination zone around the radio transmitter 1 source of the radio signals received.
• the exponent of the distance in this constitutive law of the RSSI is generally brought to 2.2.
• the variation as a function of the distance between the radio transmitter 1 and the user equipment 2 of the envelope (or the maximum value) of the normalized power levels of the signals 11-14 received is approximated by a second order polynomial.
• the variation as a function of the distance between the radio transmitter 1 and the user equipment 2 of the envelope (or the maximum value) of the normalized signal-to-noise ratios relating to the different signals 11-14 received is approximated by a high polynomial.
• a first function approximating the variations as a function of the distance of a statistical value (the maximum value, the minimum value, the average, the median or other) of the normalized power levels of the signals received (dashed curve in FIG. 5) and a second function approaching the variations as a function of the distance of a statistical value (the maximum value, the minimum value, the average, the median or other) of the normalized signal-to-noise ratios are determined.
• regression methods multilinear, polynomial, or other
• regression methods can be used to determine the parameters of the function approaching the variation as a function of the distance of the statistical value of the normalized power levels of the different signals 11-14 received and the statistical value of the normalized signal-to-noise ratios for the different signals received 11-14.
• Different curve fitting techniques or state-of-the-art experimental curve analysis can be used for this purpose.
• a proximity index i is formulated by a sum of the first function weighted by a first non-zero weighting coefficient and the second function. weighted by a second non-zero weighting coefficient, the sum of the first weighting coefficient and the second weighting coefficient being equal to one.
• a proximity index i of the radio transmitter 1 is formulated as follows: y ⁇
• a statistical value (in particular, the envelope) of the normalized power levels of the various signals 11-14 received by the user equipment 2 at a distance from the radio transmitter 1;
• a statistical value (in particular, the envelope) of the normalized signal-to-noise ratios relative to the various signals 11-14 received by the user equipment 2 at said certain distance from the radio transmitter 1.
• This illustrative formula of the proximity index i is obtained by linearization of the standardized RSSI (or in an equivalent manner, the RSS) as if it were a parabola and by truncating the approximation polynomial of the normalized SNR.
• the proximity index i is a combination of a first function approaching the variation as a function of the distance of the envelope of the normalized power levels of the signals 11-14 received and a second function approaching the variation in function of the envelope distance of normalized signal SNRs 11-14.
• the index i is constructed on two sequences 10 in order to have more than one observation of the received signals.
• the proximity index i is built on three sequences 10.
• the proximity index i is a function indicative of the distance separating the user equipment 2 from the radio transmitter 1 source of signals 11-14 received by said user equipment 2.
• the weighting coefficient of the RSSI in the calculation of the proximity index i, is greater than the weighting coefficient of the SNR because the RSSI is more related to the distance with respect to the radio transmitter 1 than the SNR, the sum of the two weighting coefficients being equal to unity.
• a weighting coefficient of 2/3 advantageously makes it possible to dampen the variations of the SNR.
• other complementary weights may be used, to weight, respectively, the RSSI and the SNR, such as 3 ⁇ 4 and 1 ⁇ 4, 3/5 and 2/5, or 4/7 and 3/7.
• a weighting coefficient of the RSSI greater than the weighting coefficient of the SNR reflects the dynamic preponderance of the RSSI at intermediate distances and close to the radio transmitter 1.
• the distance between the user equipment 2 and the radio transmitter 1 is estimated from the proximity index i according to the following formula connecting the proximity index i to the distance d:
• the user 2 selects a type of environment from a list of predefined environments that is proposed to him and for which coefficients k are previously associated.
• the type of environment (and consequently the coefficient k) is determined from a satellite geolocation of the user 3 by means of dedicated sensors included in the user equipment 2.
• a proximity index is calculated, according to a pre-established formula of this index. Proximity.
• a distance separating the user equipment 2 from the radio transmitter 1 can also be estimated from this proximity index i.
• a trilateration for the purpose of locating the radio transmitter 1 is, therefore, possible from the estimation of this distance in at least three different positions of the user equipment 2. The intersection of the three circles centered on the three positions of the user equipment 2 and spokes, respectively, the estimated distance at each of these positions makes it possible to locate the radio transmitter 1. In case of ambiguity, additional positions of the user equipment 2 can be used, to refine the estimate of the position of the radio transmitter 1.
• the proximity index simultaneously exploits two quantities, namely the power level of the signal 11-14 received and the ratio between the power of this signal 11-14 and the power of the noise.
• a target object 4 is displayed to which a radio transmitter 1 is linked.
• This radio transmitter 1 is connected to a server 5 for monitoring radio transmitters 1 of the type linked to the object. target 4.
• the radio transmitter 1 is linked to the target object 4 so as to enable the location of said target object 4.
• This target object 4 is, for example, a moving object such as a motor vehicle, a carriage, or an animal.
• the target object 4 is a portable object such as example a suitcase, a watch, a keychain, a backpack, a purse, a phone, a wallet, or a toolbox.
• the target object 4 is any object whose location or tracking of its location is desired, such as a merchandise container, a car, a motorcycle, or a bicycle.
• the radio transmitter 1 has, in one embodiment, the shape of a tag, a chip of low electrical power consumption and extreme miniaturization.
• the radio transmitter 1 can be provided as an integral part of the target object 4, or be linked to it later by the end user.
• target objects 4 can be located by the user equipment 2 being within radio range of the radio transmitter 1 they integrate.
• configuration data (identifier, physical address / IP, encryption key, frequency of recurrence of communications, slot of transmission in a TDMA division for example) are exchanged between the server 5 and the radio transmitter 1 allowing the establishment of a subsequent communication between them.
• Communications between the radio transmitter 1 and the monitoring server 5 are preferably established via a public mobile communications network.
• the radio transmitter 1 communicates (step 51) its position to the monitoring server 5, at predefined time intervals.
• the radio transmitter 1 obtains its location from a geolocation device which is arranged there, or from any other device to which it is connected.
• the radio transmitter 1 synchronizes its clock and calculates, in a regular manner, its position from the observation of navigation satellites.
• the radio transmitter 1 stores and dates its last calculated position.
• the radio transmitter 1 communicates (step 51) to the server 5 for tracking its dated position, its state of motion, its synchronization state and the date of this communication.
• the tracking server 5 stores the information communicated to it by the radio transmitter 1.
• the tracking server 5 requires (step 52) a position of the radio transmitter 1 from the public mobile communications network 6.
• the public mobile communications network 6 determines an approximate position of the transmitter, according to the levels received by the receiving stations of this network 6.
• the public mobile communications network 6 then communicates (step 53) the determined position at the server 5 tracking.
• the tracking server 5 stores the position and the date at which it is determined by the public mobile communications network.
• the monitoring server 5 no longer has an up-to-date position of the radio transmitter 1 (or in an equivalent manner, of the target object 4).
• Various reasons may be causing this incident such as, for example, the target object 4 is lost, the target object 4 is stolen, the shutdown or a malfunction in the communication interface of the radio transmitter 1 with the public mobile communications network 6, or the presence of the radio transmitter 1 in a non-cooperative environment preventing its communication with the public mobile communications network.
• the position of the radio transmitter 1 is, in one embodiment, unpredictable (by dissemination, mislaying, diversion or theft, for example).
• the target object 4 is in a confined interior environment, such as a workshop, a warehouse, a garage, or a covered or underground car park, whereas the user equipment 2 is in a external environment (a street / road in a suburban, urban, dense urban, peri-urban, or rural environment). In one embodiment, the target object 4 is in an environment where satellite geolocation is unavailable.
• the monitoring server 5 transmits (step 54), on request or not, the last known dated position of the radio transmitter 1 to the user equipment 2.
• the user 3 of the user equipment 2 decides, when the target object 4 is out of direct view from the last known dated position transmitted to it, to initiate a radio guidance procedure to the transmitter radio 1.
• the starting point of the user equipment is the last GPS position of the known connected object of the tracking server.
• the user equipment 2 sends (step 55) a search frame request to the monitoring server 5.
• the tracking server 5 Following this request, the tracking server 5 generates a traffic control command with a number of arguments which define a sequence of signals 11-14 that the radio transmitter 1 must execute. The tracking server 5 adds the temporary signature of this radio transmitter 1.
• the traffic control control defines transmissions to be executed by the radio transmitter 1 which have diversity in modulation (for example, in spread spectrum) and in power.
• the data of this radio control command are encrypted with a secret key associated with the radio transmitter 1 and with an initialization vector related to the date of elaboration.
• the tracking server 5 elaborates the frame for the radio transmitter, adding to the radio control the header, the initialization vector and the physical address of the radio transmitter 1.
• the monitoring server 5 generates a transmission burst of the frame by the user equipment 2, depending on the desynchronization (light or strong) that can be expected from the radio transmitter 1.
• the monitoring server 5 optimizes the probability of interception according to whether the opening time of the user equipment 2 is quite well known or not.
• the tracking server 5 transmits (step 56) the activation message of the traffic guidance, thus developed, to the user equipment 2.
• the user equipment 2 Upon reception of the traffic control activation message, the user equipment 2 initiates (step 57) the frame transmission burst for the repetition time defined by the monitoring server 5 by creating the agreed broadcasts.
• the user equipment 2 begins with a preamble, which will allow the radio transmitter 1 to recognize a friendly broadcast.
• the user equipment 2 repeats the sending (step 57) of the traffic control command to the radio transmitter 1 until obtaining the latter an acknowledgment of receipt.
• the radio transmitter 1 comprises a receiver configured to receive the signals transmitted by the user equipment 2.
• the radio transmitter 1 periodically opens its receiver during a enough time to capture two symbols at the rate of the spreading factor corresponding to the maximum range of the message.
• the radio transmitter 1 finally intercept the friendly broadcast. If the physical address is not his, he remains in reception. Otherwise, it decodes the entire frame.
• the radio transmitter 1 decrypts the radio control command using its secret key and the initialization vector included in the received frame.
• the radio transmitter 1 then elaborates the contents of the response message (last dated position, state of motion, synchronization status) and the sign.
• the user equipment 2 is placed in permanent listening on the current frequency of the radio transmitter 1.
• the radio transmitter 1 transmits (step 58) the sequence 10 of the signals 11-14 according to the information included in the radio control (type and parameters of the modulation, frequency, spectrum spreading factor, power, frequency of recurrence of emission of the signals), until the expiry of the allotted time. It sends the content in clear (the signature excludes the risk of confusion caused).
• the user equipment 2 receives, at a distance from the radio transmitter 1 (at substantially the same range so that the radio interception can not be missed by the user), the signals emitted by the transmitter radio 1 and measuring, for each of the received signals 11-14, the power level (RSSI) and the signal-to-noise ratio (SNR) relative to each of these signals 11-14 of the sequence 10.
• RSSI power level
• SNR signal-to-noise ratio
• the duration of the sequence 10 is adapted as a function of the relative speed of movement of the user equipment 2 relative to the radio transmitter 1.
• the user equipment 2 calculates a statistical value (the maximum value, the average, the minimum value, the median or other) of the power levels of the signals 11-14 received and a statistical value (the maximum value , the average, the minimum value, the median or other) of the signal-to-noise ratios relative to these signals 11-14 received substantially at the same distance from the radio transmitter 1.
• the user equipment 2 calculates a proximity index i as explained above (in application of the formula of the proximity index i above or any other formula which is equivalent to it).
• the user equipment 2 displays the envelope of the normalized power levels of the signals 11-14 received and the envelope of the normalized and smoothed SNRs relating to each of these signals 11-14 on two gauges. separated and synthetically constructed, as explained above, a proximity indicator i.
• the user equipment 2 associates the proximity indicator i with the position of the user equipment 2 on a card.
• the proximity indicator i is given in the form of a gauge which keeps its extremum in memory.
• the current position of the user equipment 2 is displayed via a color code which varies, with respect to the memorized extremum, from a first color (for example blue, synonymous with "moving away") to a second color (by example, red synonymous with "approaching").
• the value of the composite proximity index i is thus encoded as a color value.
• the path of the user 3 is depicted by a color code, defined according to the index of its proximity with respect to the radio transmitter 1.
• the user equipment 2 can send a request (step 59) to the monitoring server 5, to obtain a more discriminating modulation game in the terminal phase (reduced power and / or tighter spreading factor for example).
• the monitoring server 5 In response to the request of the user equipment 2, the monitoring server 5 elaborates the contents of a new control command of enhanced discrimination guidance.
• the previously described process applies as a new iteration on a narrow scale of a few meters.
• the methods and systems described above are, in one embodiment, used as an alternative to another location technique (for example, satellite and / or terrestrial geolocation), especially when the radio transmitter 1 has very little power or in a non-powered environment cooperative.
• another location technique for example, satellite and / or terrestrial geolocation
• the implementation of the methods described above requires a reduced calculation time, promoting the energy autonomy of the user equipment.
• These methods also have the advantage of covering any radio propagation channel (in particular, semi-inside or semi-outside) linking the radio transmitter 1 to the user equipment 2.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Position Fixing By Use Of Radio Waves (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=63834098

Family Applications (1)

Country Status (3)

Family Cites Families (2)

• 2018
  • 2018-05-21 FR FR1854209A patent/FR3081270B1/fr active Active
• 2019
  • 2019-05-16 EP EP19730208.6A patent/EP3797313A1/de active Pending
  • 2019-05-16 WO PCT/FR2019/051112 patent/WO2019224456A1/fr unknown

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