Apparatus and method for centimeter positioning of a mobile object

Abstract

The positioning system (9) comprises a device (10) and a number of fixed base stations (12) each equipped with a counter that periodically retrieves n pointer positions. The device comprises an emitter configured to emit a request comprising at least one pattern of dots such that a value read at the pointer modulates a carrier wave. Each receiving base station a) the base station repeats the pattern received from the device, and / or b) a first temporal pattern offset measured by the base station between the received pattern and the same pattern stored in the base station's memory; Emit the response. The device is - means for measuring a second temporal pattern offset between the value of the pattern point received in each response and a value stored in the memory of the device; -The distance between the device and each base station a) the total pattern offset between the pattern emitted by the device and the repeated pattern received by the device from the base station; and / or b) the second pattern offset and the first pattern offset measured by the base station; as a function of Equipped with.

Description

[Technical field]

[0001] The present invention relates to an apparatus and a method for centimeter positioning of mobile objects in outdoor or indoor environments, in particular for vehicle positioning in urban areas, autonomous driving of vehicles and mobile objects, assistance for people with visual impairments or impaired motor functions, parking position verification for self-service vehicles, travel or advertising information. [Background technology]

[0002] Estimating the vehicle's position in its lane by detecting improper paths is a key factor not only for autonomous mobility but also for safety. The current trend is towards using a number of sensors mounted on the vehicle, for example satellite positioning systems, cameras, radar and lidar, to perceive the vehicle's surroundings and position the vehicle in a digital map. However, these systems are not very accurate and are subject to many preconceptions. Solutions based on satellite positioning suffer from electromagnetic multipath in towns, resulting in a positioning accuracy of a few meters.

[0003] Other systems use cameras to detect the sides of roads or signs, for example ground reflections, or use lidar. Cameras and lidar are hindered by parked vehicles masking landmarks, and by time-varying conditions that blur the perception factor due to the computing power required.

[0004] Another approach is collaboration between vehicles and fixed infrastructure, where the infrastructure and the vehicles communicate to ensure the quality of the information provided. As a result, the work of the on-board systems is reduced and reliability and robustness are increased. However, this requires significant investment in the infrastructure.

[0005] Systems are known that comprise sensors mounted on vehicles, capable of detecting passive elements positioned on the road surface and determining the distance from the passive elements to the vehicle. These passive elements thus serve as simple and accurate passive reference points and are not very costly. However, this technology, which is well suited to roads, cannot be directly applied to problems in towns or private places, for example for parking in underground car parks. This is because in towns, road markings with passive elements are not always present and the sides of the road are often blocked, thereby hindering a direct route and therefore an accurate positioning. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to remedy all or some of these drawbacks. [Means for solving the problem]

[0007] To this end, the invention according to a first aspect envisages a system as claimed in claim 1.

[0008] By providing these, the accuracy of the positioning system is very high. As a minimum, when the offset measurement is an integer number of points of the pattern, for example a measurement by autocorrelation, it is the product of twice the time taken between the emission of two points of the pattern and the propagation speed of the signal. When the measurement of the offset of the points of the pattern is continuous, for example because it is based on a frequency analysis by means of a Fourier transform, the accuracy of the positioning can be much higher.

[0009] In some embodiments, the equipment, and each base station if each base station is equipped with means for measuring the pattern offset, comprises means for measuring the phase shift of the carrier of the received signal relative to the phase of a sinusoidal signal generated by a clock of the equipment, and by a clock of each base station if each base station is equipped with means for measuring the offset, and means for measuring the distance from the equipment to each base station by adding the measured phase shift to the measured offset to determine the distance of the equipment.

[0010] By providing these, the accuracy of the positioning system is twice the ability to discriminate between signal phase shifts times the propagation speed of the signal.

[0011] In some embodiments, the signals emitted by the device and the base station are in IQ quadrature, with the signal on the I channel being constant and the signal on the Q channel carrying an amplitude modulation of the pattern emitted by the device, with respect to at least one predefined phase shift of the carrier of this signal.

[0012] In some embodiments, to measure the first and second offsets, the base station and the device comprise means for performing a linear fit of the points of the received pattern in the IQ plane, each measured offset being equal to the sum of the pattern offset and a measured phase shift, the measured pattern shift being: - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift is equal to the difference between

[0013] In some embodiments, c) each base station comprises means for performing a straight line fit of the points of the received pattern in the IQ plane and means for measuring a phase shift, the measured phase shift being - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift is equal to the difference between each base station emitter is configured to emit an IQ signal with a negative phase shift of twice the measured phase shift such that the phase of the base station emitted signal relative to the received signal is in phase with the device emitted signal; d) the apparatus comprises means for performing a straight line fit of the points of the received pattern in the IQ plane and means for measuring a phase shift, the measured phase shift being - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift is equal to the difference between The total offset used by the instrument to measure the difference is the sum of the total pattern offsets plus the phase shift measured by the instrument's measurement means.

[0014] As a result of these respective arrangements, the accuracy of the positioning system is twice the ability to discriminate the phase shift of the points of a multiple n collinear pattern in the IQ plane times the signal propagation speed. Because there are multiple n points in the pattern, this accuracy is even higher than that obtained by measuring the phase shift of an amplitude modulated sine wave.

[0015] In some embodiments, the counter period is greater than twice the maximum flight time corresponding to a predefined maximum distance between the device and a base station likely to respond to a request from the device.

[0016] In some embodiments, the pattern of n points is the inverse Fourier transform of a spectrum with constant amplitude and random or pseudorandom phase.

[0017] By providing these, the pattern comparisons used to determine the pattern time shifts are more reliable.

[0018] In some embodiments, each emitter of the device and the base station is configured to emit signals on multiple carriers having different frequencies.

[0019] The ambiguity of the distance measurement modulo another distance associated with the carrier can be resolved.

[0020] In some embodiments, the emitting patterns of all devices and all base stations are identical.

[0021] By providing these, the implementation of the present invention becomes easier at the stage of means for measuring the pattern time shift.

[0022] In some embodiments, the patterns emitted by at least two different devices are different, and the signal emitted by each device comprises data identifying or representative of the pattern emitted by that device.

[0023] By providing these, the base station can identify the device, or the device itself can identify its own pattern in order to measure the pattern time shift.

[0024] In some embodiments, the patterns emitted by at least two different base stations are different and the signal emitted by each base station comprises data identifying or representative of the pattern emitted by that base station.

[0025] Providing these allows the device to identify each base station by the patterns it receives.

[0026] In some embodiments, each signal emitted by a base station comprises an identifier of this base station, and the determination means of the device are arranged to determine the position of this base station using the identifier of this base station.

[0027] In some embodiments, the identifier of the base station comprises a geographic location of the base station.

[0028] By providing these, the device does not need to store an up-to-date database of the locations of different base stations, as the base stations inform the device of their latest locations, thus simplifying the device and making positioning more reliable.

[0029] In some embodiments, the frequencies of the signals emitted by all devices and all base stations are in the ISM (industrial, scientific, and medical) bands.

[0030] According to a second aspect, the invention contemplates an apparatus of the system that is the subject of the invention.

[0031] According to a third aspect, the invention envisages a base station of the system that is the subject of the invention.

[0032] In some particular embodiments of this base station, the base station may be configured to receive from other It is configured to act like a device pointing towards a base station, and the emitter is configured to emit a displacement message if the determined position differs from an already stored position of this base station.

[0033] In this way, the base station can verify and, if necessary, update its cadastral map position.

[0034] The advantages are as follows: Geographic calibration of the network of distances between base stations is easy to implement, not time-consuming and not labor-intensive. This calibration is therefore inexpensive. By periodically measuring the distance network, it is possible to check that the distance network is functioning and thus to constantly verify this, to detect malfunctions and to rapidly correct errors.

[0035] In some embodiments, at least one base station is configured to act as a pointing device to other base stations relative to a point on a cadastral map from which it determines its own position.

[0036] According to a fourth aspect, the present invention envisages a method according to claim 18.

[0037] In some embodiments, the method that is the subject of the present invention comprises a step of allocating time intervals or time slots to the fixed base stations according to their geographical location, such that two fixed base stations exchanging signals with the same fixed base station are not assigned the same time interval to each of the two fixed base stations and to this same base station.

[0038] In this way, the risk of colliding with a second signal is greatly reduced.

[0039] In some embodiments the method comprises positioning the fixed base station relative to other base stations associated with a point on the cadastral map.

[0040] According to a fifth aspect, the present invention contemplates the use of the method which is the subject of the present invention, the system which is the subject of the present invention, the device which is the subject of the present invention and / or the base station which is the subject of the present invention for guiding ground or aircraft vehicles, guiding pedestrians indoors or outdoors, indicating parking errors for self-vehicles, geolocating elements in an environment, determining the position and orientation of a visualization system comprising several devices for augmented reality purposes for civil engineering, leisure and travel applications, determining gestures for gesture interfaces, or motion capture, for example.

[0041] Since certain objects, advantages and features of the apparatus, base stations, methods and uses which are the subject of the present invention are similar to those of the system which is the subject of the present invention, they will not be repeated here.

[0042] Other advantages, objects and particular features of the present invention will become apparent from the non-limiting description of at least one particular embodiment of the device and method that is the subject of the invention, with reference to the drawings contained in the Appendix. [Brief description of the drawings]

[0043] [Figure 1] 1 shows a schematic representation of a mobile device mounted in a vehicle and two base stations in communication with the device. [Diagram 2]A particular phase shift measurement is represented diagrammatically in the form of a signal. [Diagram 3] Another particular phase shift measurement is represented diagrammatically by a signal wave. [Figure 4] It represents the offset of the 64-point fixed periodic pattern emitted by the device relative to the offset of the base station, and the amplitude spectrum of the signal emitted by the device. [Diagram 5] 13 shows a measurement example of the first embodiment when the frequencies of the device and the base station are not completely equal. [Figure 6] The communication between a device and a base station, or between two base stations, is represented diagrammatically in the form of a data frame. [Figure 7] 1 illustrates a schematic representation of a layout of a network of fixed base stations on a road network. [Figure 8] 1 shows a schematic representation of an electronic circuit for implementing the invention in a device or in a base station. [Figure 9] 13 shows a graph of distance estimates for an embodiment of the device. [Figure 10] 4 shows the error in estimating the offset at the points of two 64-point fixed periodic patterns as a function of the noise level relative to the signal, calculated over one period of the pattern and over 100 periods of the pattern. [Figure 11] The steps in a particular embodiment of the method that is the subject of the present invention are represented generally in the form of a logic diagram. [Figure 12] It is a time series representation of the cyclical repetition of a pattern. [Figure 13] The emitted signal representing the pattern is represented in the IQ plane. [Figure 14] The received signal corresponding to the example emitted signal in FIG. 13 is represented in the IQ plane. [Figure 15] A time series representation of the transmission and receipt of requests with repetition between one and two of the patterns. [Figure 16] 16 is a timeline of the transmission and reception of a response to the request illustrated in FIG. 15. [Figure 17] The steps in a particular embodiment of the method that is the subject of this invention are depicted in the form of a logic diagram. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] The present description is presented in a non-limiting manner, in which each feature of an embodiment can be combined in an advantageous manner with any other feature of any other embodiment.

[0045] Throughout this specification, the term "equipment" refers to an item of equipment that emits a positioning request, and the term "base station" refers to each item of equipment that responds to a positioning request. As described herein, each base station preferably comprises an item of equipment similar to, or even identical to, the equipment, so that each base station can determine its own geographical position relative to other base stations. Throughout this specification, the equipment is considered to be mobile and the base stations are considered to be fixed, except in cases where a fixed base station serves as the equipment that determines its own geographical position, as described with reference to FIG. 7. In some embodiments, at least one base station is mobile, thereby enabling positioning of each mobile object with a mobile base station mounted on board.

[0046] Please note that the figure is not to scale.

[0047] 1 shows diagrammatically the environment of a positioning device 10, which in this case is integrated into a vehicle 11. The mobile device 10 communicates with a fixed base station 12, which is preferably mounted at a high position, for example on a lamppost, a road sign, a specific pillar or on the wall of a building. The device 10 and the fixed base station 12 form a positioning system 9. The mobile device 10 and the fixed base station 12 each comprise a fixed electromagnetic wave emitter / receiver device 13 coupled to a computing unit.

[0048] Positioning is achieved by measuring the time of flight (TOF, an acronym) of electromagnetic waves between the mobile device 10 and the fixed base station 12. To determine the location of the mobile device 10, the conventional state of the art requires the use of several fixed base stations 12, as well as at least three distance measurements that require precise synchronization of the frequency and phase of all the emitters / receivers of the fixed base stations 12 or the mobile device 10 mounted on board. Although frequency synchronization is relatively simple, ,phase synchronization requires an absolute clock. In satellite positioning systems, this absolute clock is obtained by ultra-stable atomic clocks, which are not feasible in the case of dense ground-based networks required for positioning inside towns or buildings. The object of the invention is to perform distance measurements without using such absolute clocks.

[0049] For informational purposes, it is assumed that the oscillators of the fixed base station 12 and the emitter / receiver of the mobile device 10 mounted on board the vehicle have substantially the same frequency f, but the phase of one is unknown to the other and vice versa. The fact of having exactly the same frequency f means that these unknown phases are constant over time. If the frequencies of the device and the base station were only substantially equal, but not equal, the unknown phase would change slowly over time, but as will be shown later, this does not limit the accuracy of the positioning. To eliminate this unknown phase shift, we use raw (I,Q) signals obtained from IQ modulators / demodulators installed in the fixed base station 12 and the emitter / receiver of the mobile device 10 on board the mobile 11.

[0050] Quadrature Amplitude Modulation ("I / Q", "IQ" or "QAM") is a form of modulating a carrier wave by modifying the amplitude of itself and a quadrature wave (a wave shifted 90 degrees in phase from the carrier wave) according to the information carried by two input signals.

[0051] This means simultaneously modifying the amplitude and phase of the carrier wave depending on the information to be emitted.

[0052] When emitting two analog signals using QAM type modulation, the emitted signals are s(t)=I(t)cos(2πf0t)+Q(t)cos(2πf0t+π / 2) It takes the form of where I(t) and Q(t) are the modulating signals and f0 is the carrier frequency.

[0053] At the receiver stage, the two modulated signals can be demodulated by using a coherent demodulator. Such a modulator multiplies the separately received signals first by a cosine and second by a cosine phase-shifted by π / 2. The two multiplications produce estimates of the I(t) and Q(t) channels, respectively. Thanks to the orthogonal nature of the two carriers used, the two modulated signals can be extracted independently.

[0054] In an ideal scenario, the I(t) channel is demodulated by multiplying the received signal with a cosine signal. r i (t) = s(t) cos(2πf0t) r i (t)=I(t)cos(2πf0t)cos(2πf0t)+Q(t)cos(2πf0t+π / 2)cos(2πf0t)

[0055] By using trigonometric identities r i (t)=(1 / 2)I(t)[1+cos(4πf0t)]+1 / 2Q(t)cos(4πf0t+π / 2) r i (t)=(1 / 2)I(t)+1 / 2[I(t)cos(4πf0t)+Q(t)cos(4πf0t+π / 2)] is obtained.

[0056] signal r iWe apply a low-pass filter to (t), thereby removing the high frequency component (4πf0t), leaving only the (1 / 2)I(t) term. It is noted that this signal is not affected by the Q(t) channel, which illustrates that the I(t) channel can be received independently of the Q(t) channel. In a similar way, we apply a residual phase shift of π / 2 to the received signal s(t), The Q(t) channel is received by multiplying the string signal.

[0057] In terms of IQ phase convention, the terms "I component" (or "I channel") and "Q component" (or "Q channel") are common ways of referring to the in-phase and quadrature-phase signals, respectively. The two signals generally comprise a high-frequency (or carrier) sinusoidal amplitude modulated by a relatively low-frequency function that carries some information. The two carriers are in quadrature, with I being 1 / 4 cycle out of phase with respect to Q, or equivalently, leading Q by 3 / 4 cycle.

[0058] In Figures 2 and 3, only one of these quadrature sine waves is shown to explain the phase shifting and distance measurement operations, which corresponds to a constant I and / or Q component in the IQ quadrature signal.

[0059] The device 10 emits a first sinusoidal signal 21. Due to the time of flight for this signal 21 to reach the base station 12, the signal 22 received by the base station 12 is phase shifted with respect to signal 21 and has a phase delay 23. The base station 12 has a clock that provides a signal 24 having a frequency substantially equal to that of signal 21, but having a phase shifted with respect to signal 21 by an unknown phase difference.

[0060] In the embodiment shown in Figure 2, the base station 12 receiving the signal 22 measures the phase delay 25 of the signal 22 relative to its own clock 24. The base station 12 then emits to the device 10 that emitted the signal 21 a signal 26 synchronized with the clock signal 24, and a message representing the phase delay 25. Due to the time of flight for the signal 26 to reach the device 10 that emitted the signal 21, the signal 27 received by the device 10 is phase shifted with respect to the signal 26, with a phase delay 28 equal to the phase delay 23.

[0061] The device 10 measures the phase delay 29 of the signal 27 relative to the signal 21. The device 10 extracts the value of the phase delay 25 of the message received from the base station 12 and adds the phase delay 25 to the phase delay 29. In this way, the device 10 obtains twice the phase delay 23 and from this deduces the distance d between the device 10 and the base station 12 that responded by sending back a signal 26. This is because twice the phase delay 23 is equal to 4×π×d / λ, where λ is the wavelength of the wave 21.

[0062] In other words, when the wave 22 arrives at the receiver of the base station 12, this receiver has no information about when this wave was emitted by the emitter of the device 10. The base station 12 can only determine the phase 25 of this wave relative to the phase of its own local oscillator. This phase, referred to below as φ12, is given by: φ12=Angle(Q2 / I2)=φ2-(φ1-2×π×d / λ) (1) is measured directly using the signal (I1, Q2) obtained at the output of the IQ demodulator of the base station 12, During the ceremony, -φ1 is the unknown phase of the local oscillator of the emitter of the device 10; -φ2 is the phase of the local oscillator of the base station 12 receiver; -d is the distance between the device 10 and the base station 12, −λ is the wavelength of the wave emitted by the device 10.

[0063] Therefore, when the phase of the local oscillator of the device 10 is not known, it is not possible to determine the distance d by its own received phase 25 .

[0064] The base station 12 that received the wave sends a message containing the value φ12 to the device 10 that emitted the wave. Thus, device 10 receives a signal (I1, Q1) at the output from its IQ modulator, which φ21=Angle(Q1 / I1)=φ1-(φ2-2×π×d / λ) (2) The phase φ21 can be calculated as follows:

[0065] In this equation (2), everything is known except for the distance d, which is therefore φ12+φ21=4×π×d / λ (3) Therefore, it can be determined modulo half the wavelength λ.

[0066] The modulus uncertainty can be resolved by using several frequencies f for the electromagnetic wave, and therefore several wavelengths, for example λ=c / f, where c is the speed of light, or by using known frame correlation techniques (see FIG. 6).

[0067] In the embodiment shown in FIG. 4, the modulus uncertainty is determined by a signal I(t) that is constant over time, and a maximum frequency f(t) whose period corresponds to the round trip time of an electromagnetic wave in the desired distance range and whose spectrum is maximum and is determined by the bandwidth of the communication system employed. maxThis is solved by using a signal Q(t) corresponding to a fixed periodic pattern up to 100 ms. For example, an inverse Fourier transform of a spectrum 77 with constant amplitude but random phase gives a pattern over a given number of points (see FIG. 4). When the signal received by the base station is IQ demodulated, the base station also records a fixed periodic signal generated by itself, which has the same pattern as the one emitted by the equipment. Thus, the base station determines the phase 25 by rotating its IQ plane by an angle such that the I component is constant. This angle is therefore the inverse of the desired phase 25, and the Q component obtained after the rotation can be compared with the fixed periodic pattern recorded by the base station on reception, which allows the base station to obtain the offset of each relative to the other by using the phase relationship or by using the properties of the Fourier transform on the offset signal. Knowledge of the phase 25, and of the offset calculated by the base station for the outgoing signal and by the equipment for the return signal, allows the distance to be obtained with high accuracy over a wide distance range. FIG. 4 shows the offset by 4,123 points of a 64-point fixed periodic pattern 75 (s1) emitted by a device relative to a base station fixed periodic pattern 76 (s2) that is identical to pattern 75.

[0068] In the embodiment shown in Fig. 4, the device 10 transmits not a signal oscillating at a single frequency, but a signal 75 oscillating at the frequency of a first clock modulated by a known fixed periodic pattern 77 whose frequency support is limited to an authorized bandwidth. When the base station 12 receives the signal from the device 10, it measures the phase between the carrier of the received signal and its own local oscillator as described above, and also measures the time shift between the fixed periodic pattern received from the device 10 and the same fixed periodic pattern generated by the base station 12. The base station 12 then transmits to the device 10 not only a signal oscillating at a second frequency modulated by the fixed periodic pattern of the base station 12, but also information about the phase shift between the clock and the offset between the measured patterns. When the device 10 receives this information, the device 10 can also measure the phase shift between the carrier of the received signal and its own local oscillator, and also the offset between the received pattern and its local fixed periodic pattern.

[0069] Furthermore, when similar information about the base station 12 is received by message, this, combined with the addition of a phase shift, gives the distance between the device 10 and the base station 12 modulo the wavelength. Combined with the addition of an offset, gives the distance between the device 10 and the base station 12 modulo the wavelength corresponding to the repetition frequency of the fixed periodic pattern. Thus, combined with a pattern offset 77, a large distance range is possible with an accuracy limited by the bandwidth of the pattern, while combined with a phase shift gives sub-wavelength accuracy. In one variant, the base station 12 receives the received pattern in phase with The base station 12 transmits a signal oscillating at the frequency of the second clock, phase shifted so that it is in phase with the received carrier, modulated with a pattern offset such that: . Thus, there is no need to transmit phase shift and offset information, and the phase shift and offset received back at the device 10 stage is directly proportional to the distance between the device 10 and the base station 12.

[0070] In the embodiment shown in Figure 3, a base station 12 receiving a signal 22 measures the phase lag 25 of the signal 22 with respect to its own clock. This base station 12 then emits a signal 31 to the device 10 that emitted the signal 21, synchronized with the clock signal 24, with a phase lead 32 equal to the phase lag 25. Thus, the signal 31 is in phase with the signal 22 received by this base station 12.

[0071] Due to the time of flight of signal 31 to reach device 10 which emitted signal 21, signal 33 received by device 10 is phase shifted with respect to signal 31, with a phase delay 34 equal to phase delay 23. Device 10 measures the phase delay 36 between signal 21 and signal 33. Device 10 thus obtains phase delay 23 and from this deduces the distance d between device 10 and base station 12 which responded by sending back signal 26. This is because twice the phase delay 23 is equal to 4×π×d / λ, where λ is the wavelength of wave 21.

[0072] In other words, the base station 12 transmits to the device 10 what it receives, where I=I2 and Q=Q2. This is equivalent to transmitting a wave in phase with what it receives, as shown by signals 22 and 31 in Figure 3. In reality, the device transmits the signal I×cos(2πf0t+φ1) If you send The base station receives the signal due to propagation delays. I×cos(2πf0(td / c)+φ1) After demodulation and filtering, the I and Q components measured by the base station are respectively ×cos(-2πf0d / c+φ1-φ2) and I×cos(-2πf0d / c+φ1-φ2-π / 2) is proportional to.

[0073] The base station then calculates the same IQ point, or a proportional IQ point, i.e., the signal I×cos(-2πf0d / c+φ1-φ2)×cos(2πf0t+φ2)+ I×cos(-2πf0d / c+φ1-φ2-π / 2)×cos(2πf0t+φ2+π / 2) Send. The device receives this signal after a propagation delay, i.e. I×cos(-2πf0d / c+φ1-φ2)×cos(2πf0(td / c)+φ2)+ I×cos(-2πf0d / c+φ1-φ2-π / 2)×cos(2πf0(td / c)+φ2+π / 2) Receive.

[0074] After demodulation and filtering, the I and Q components measured by the instrument are I×cos(-2πf0d / c+φ1-φ2)×cos(-2πf0d / c+φ2-φ1)+ I×cos(-2πf0d / c+φ1-φ2-π / 2)×cos(2πf0d / c+φ2-φ1+π / 2) and I×cos(-2πf0d / c+φ1-φ2)×cos(-2πf0d / c+φ2-φ 1-π / 2)+ I×cos(-2πf0d / c+φ1-φ2-π / 2)×cos(-2πf0d / c+φ2+π / 2-φ1-π / 2) which, using the rules of trigonometry, can be expressed as, for the I and Q components, I×cos(4πf0d / c) and I×cos(4πf0d / c+π / 2) which shows that the phase 4×π×d / λ=4πf0d / c can be obtained independently of the unknown phases φ1 and φ2 of the device and base station clocks.

[0075] In some embodiments, it is possible to combine the use of two frequencies with the use of a fixed periodic pattern, especially if the bandwidth of the pattern is not sufficient to resolve the uncertainty modulo the first frequency.

[0076] It should be noted that the different embodiments of the invention also work well when the two oscillators do not have exactly the same frequency f. Figure 5 shows an example of a real measurement between the device 10 and the base station 12 when the frequencies of the local oscillators of the device 10 and the base station 12 are only substantially equal, but not exactly the same. The phase between the two oscillators therefore varies over time, as shown here by the arrows 37 and 38 of the IQ points shown in the complex plane, with respect to the device 10 and with respect to the remote base station 12. Even if this phase changes over time, it does so in the opposite direction, to the arrow 37 according to the point of view of the device 10, or to the arrow 38 according to the point of view of the remote base station 12. Thus, according to the first embodiment, by combining the two measurements through the summation of the phases at each instant, a theoretically fixed point in the complex phase plane is created, with an accuracy of 6.4° due to the measurement noise, which corresponds to 4 x π x d / λ according to equation (3). In the second embodiment, FIG. 3, it is sufficient to transmit waves I=I2(t) and Q=Q2(t).

[0077] In this way, the turnaround time creates a fixed phase that is easy to account for.

[0078] In a degraded operating mode, where the device has very limited computing power, the location of the device can be calculated by the base station using the phases measured simultaneously by at least five surrounding base stations. In this embodiment, the device emits a first signal that is received by several surrounding base stations. Each of these base stations transmits the measured IQ point in its own time slot, but recognizes that it is operating in a degraded mode due to the identifier transmitted by the first device, and the returned signal is measured by each of these surrounding base stations, not by the device. These surrounding base stations can then combine the phases measured by each of the other base stations, which allows the determination of different paths of the device's electromagnetic waves, either directly towards one base station or via another. Since the base station knows the distances that separate the base stations, the different measured distances allow the device to determine its location without the device having to calculate. The location of the device can be made available by the communication network and therefore with longer or shorter latency. This is therefore particularly suitable for devices that do not require real-time information, for example for the validation of parking of self-service vehicles.

[0079] In all these cases, the advantages of using the present invention are: -Measurements are almost instantaneous, -High spatial accuracy, for example less than a centimeter for the 2.4GHz frequency, a frequency band not used for this type of application; the possibility of carrying out measurements at the level of fixed base stations (useful for operators who manage or use the infrastructure) or at the level of the mobile unit 10 mounted on board the vehicle (useful at the mobile unit, especially when the mobile unit is autonomous, since this avoids network latencies); -There are no major technological breakthroughs, just the adoption of existing systems to facilitate industrial development and limit costs. Equipped with.

[0080] The invention allows a reliable and inexpensive way to obtain a position quickly, to within centimetres, in an environment, in particular in a city or indoors, for example in a train station, by mobile / infrastructure cooperation. The invention involves the measurement of the time of flight of electromagnetic waves between fixed base stations 12, called references, and a mobile device 10 embedded in the mobile. The measurement of the distance of the device 10 to each fixed base station 12 is reliable and fast, with an accuracy of less than 5 centimetres (typically 1 centimetre).

[0081] The operation of the phase, the transmission of a phase shift in the message in FIG. 2, or the phase shift of the return signal 31 in FIG. 3, is performed by the responding base station 12 to preclude the determination of the time synchronization distance between the clock of the equipment 10 and the clock of the remote base station 12.

[0082] In practice, to determine its position, the device 10 must be able to identify each associated base station 12 to which it measures its distance d. Likewise, downstream collisions between signals 26 or 31 must be avoided. For these two reasons, the signals exchanged between the device 10 and each base station 12 are structured as frames 42, 45 and 49, as shown in Figure 6. The upstream facing frame 42 is for example Carrier 41 frequency, - device identifier, - a request that may require a response, possibly indicating the implementation to be used; and - Possibly codes for error detection and / or correction Carries a message representing.

[0083] The device 10 then switches to a listening mode of operation.

[0084] Each remote base station 12 is initially in listening mode. As described with reference to Figures 2 and 3, a first base station 12 receives a frame 42 on a carrier 43 that is phase shifted relative to the carrier 41 due to the time of flight of the frame between the device 10 and this first base station 12. This first base station 12 responds to this message in its assigned time slot after a predefined time interval 44 and then returns to listening mode. A second base station 12 receives a frame 42 on a carrier 47 that is phase shifted relative to the carrier 41 due to the time of flight of the frame between the device 10 and this second base station 12. This second base station 12 responds to this message in its assigned time slot after a predefined time interval 48 and then returns to listening mode.

[0085] The downstream frames 45 and 49 are e.g. - Carrier 41 frequency, - an identifier of the base station 12, - Response to a request, for example phase 25, - the identifier of the device 10 that sent the request, and - Possibly codes for error detection and / or correction Carries a message representing.

[0086] Another advantage of communicating via frames is that this communication allows measurement of frame offsets that resolve the uncertainty in the measurement of distance d, particularly over long distances d, approximately modulo half a wavelength depending on the embodiment. Frames and carriers are also advantageously quantized as described above. By taking advantage of the independent nature of the I and Q components of the device and base station, they can be emitted simultaneously.

[0087] In some embodiments, the means for determining the distance of the device 10 relative to the fixed base station 12 is configured to determine the location of the base station 12 using an identifier of the base station 12, for example because the device 10 maintains a database of the geographic locations of the base stations 12.

[0088] In some embodiments, the identifier of the base station 12 comprises its geographic location. Thus, the device 10 does not need to store an up-to-date database of the locations of different base stations 12, as these base stations 12 inform the device of their up-to-date locations. The device 10 is simplified and positioning is more reliable and faster.

[0089] As shown in FIG. 7, the automatic measurement of the distance between base stations 51, represented by black disks, and the recognition of several cadastral map points 52, represented by white disks, allows for rapid calibration, inspection, and detection of incidents.

[0090] In reality, precise positioning requires equally precise reference points.

[0091] The electronic circuits, for example the circuits 60 of the fixed base stations 51 and the on-board equipment 10, can be completely similar. Thus, determining the distance between the fixed base stations 51 and the mobile body with the on-board equipment 10 is just as easy as determining the distance between the fixed base stations 51. The distances between the fixed base stations 51 can be measured periodically and any differences with respect to the previous situation, for example due to an accident or malicious activity on the mast holding the fixed base stations 51, are quickly detected and known. The network 50 of base stations 51 can therefore be quickly reacted to by taking the corresponding fixed base station 51 out of service or by recalculating the exact position of the corresponding fixed base station 51. This introduces a high robustness to this network 50. Also, since the distances between the base stations 51 are known, a dense network of distances is thereby formed. The absolute positioning of these points therefore requires at least three absolute reference points, for example created by points 52 on a cadastral map whose geographic coordinates are fully defined.

[0092] It should be noted that the fixed devices 51 are recognized by their identifiers. In order to match this distance network with geographical points, during the calibration phase: - the technician places a mobile base station at a known geographic point, e.g., at a point on a cadastral map; - the distance of the known geographic point from surrounding base stations constrains the distance network to be associated with the known coordinates; - the technician performs this operation at least twice using other known geographic locations, preferably widely separated; -A minimum of three geographical points are required to fully constrain the distance network, and using more geographical points allows for redundancy which improves accuracy across the network of fixed base stations 51.

[0093] Calibration therefore consists in automatically building a network of interconnections between the fixed base stations 51 and then adding by the technician the mobile base stations located at points 52 on the cadastral map. It is therefore possible to completely constrain the network of distances 50 with just a few actions by the technician and therefore in a short period of time.

[0094] Due to the time slot allocation according to the distance between the fixed base stations 51, which can be automated (see FIG. 7), the risk of collision with secondary signals and downstream bound frames is significantly reduced.

[0095] When using more than two base stations 51, it must have a geographical point, which in turn acts as a device and queries the surrounding base stations 51. When the distance between this device 51 and a sufficient number of base stations 51 is known, the device 51 calculates its geographical position and makes this data item available via a network connection directly using the base station's microwave system (this system can preferably coexist with Wi-Fi in the 2.4 GHz band) or via an additional cellular connection, for example.

[0096] Each base station 51 can also transmit raw distance data to a central computer system (not shown) which determines the geolocation of each base station belonging to the network of base stations. Distances to at least four reference base stations are needed to determine the geolocation, since a distance to one reference base station defines a sphere of possible positions. With two distances, the intersection of the two spheres restricts the possible positions to a circle. With three distances, only two possible points remain for the intersection of the three spheres. Four distances resolve all uncertainties. In addition, it is preferable that the fixed base stations are not all aligned with respect to the four base stations considered, in order to improve the accuracy of the intersection between the spheres.

[0097] In the case of autonomous mobiles, the mobile device 10 is autonomous so that it has direct access to the distance and can therefore calculate its position without additional waiting periods. The accuracy obtained for the phase is less than 10°, i.e. 6.4°, in the example of Fig. 5, which allows the distance to be estimated with an accuracy of 3 to 4 mm for the 2.4 GHz frequency at a range of 5 meters by using two frequencies separated by 60 MHz, for example frequencies 2.42 GHz and 2.48 GHz. Beyond this range of 5 meters, frame delay detection is used, which only requires an accuracy of about 15 ns, or the accuracy of a 60 MHz bandwidth, which is directly within the range of the transducer of each device.

[0098] therefore, Calibration is easy to implement, quick and not labor intensive, therefore calibration is inexpensive. By periodically measuring the distance network, it is possible to check the equipment and thus constantly verify that the distance network is functioning, detect malfunctions and, if necessary, correct errors.

[0099] In some embodiments, to assign time intervals or time slots to fixed base stations 51, the geographical location of the fixed base stations 51 is taken into consideration, so that two fixed base stations 51 exchanging signals with the same fixed base station 51 are not assigned the same time intervals to these base stations 51 and to the same base station. In FIG. 7, the reference S "X" indicates the time slot number "X" between 1 and 8 assigned in this way (only a portion of the time slots assigned to the base stations is shown). Naturally, the constraint can be extended to more than two communication ranges between base stations, if one base station has a larger time slot number, for example 16. For example, two fixed base stations 51 exchanging signals with the same fixed base station 51, either directly or through an intermediate fixed base station, are not assigned the same time intervals to these base stations 51, to the same fixed base station and to the intermediate base station.

[0100] Figure 8 shows an example of an electronic implementation of the device or base station that is the subject of the invention. This circuit comprises a microwave IQ transmission / reception headend operating, for example, in the ISM band at 2.4 GHz. This transmission / reception headend comprises an oscillator, also called clock 72, a quarter-wave phase shifter 73, a low-pass filter 66, a mixer 67, an adder 74 and amplifiers 68 and 69. A transmitting antenna 70 and a receiving antenna 71 complete the analog part. The digital part comprises the DA converters 64 and 65, the AD converters 62 and 63 and a calculation unit 61 that handles the signals and the communication between the device and the base station and between the base stations. The calculation unit 61 reads the IQ points from the receiving module, performs calculations and writes the IQ points to the emitting module. The calculation unit 61 also comprises a memory (not shown) of programs and data, more particularly of the pattern described below.

[0101] In one implementation of this circuit, the microwave headend consists of an ADRF6720 circuit (a wideband (700 MHz to 3 GHz) quadrature modulator incorporating a fractional (PLL / VCO) oscillator) for emission and an ADRF6820 (a wideband (695 MHz to 2700 MHz) quadrature modulator incorporating a fractional (PLL / VCO) oscillator) for reception. These two circuits use the same local oscillator 72 for emission and reception. Of course, any other circuit that allows access to the IQ signal at least after demodulation or digitization can be used. Also, a battery or mains power (not shown) is required for the circuit to operate. It is noted that this equipment is entirely conventional and the IQ signal is simply made available to the computation unit 61 to perform the operations necessary to determine the phase and therefore the distance and then the position.

[0102] In a single phase of communication between two circuits 60A (of the equipment) and B (of the base station), the distance separating these circuits is determined. Circuit B is in listening mode and circuit A is in emission mode. - Circuit A in emission mode emits a short period of time, typically 1 microsecond, at a fixed frequency, then a message, typically a command, for example the start of a distance measurement, and an item of data, for example an identifier of circuit A. - Circuit B, in listening mode, receives the signal, records the (I,Q) point and decodes the message. In the case of distance measurement according to the embodiment illustrated in FIG. 3, circuit B, which was in listening mode, switches to emission mode and then transmits a signal comprising not only the (I,Q) point already received but also a response message, e.g. an identifier of circuit B. At the same time, circuit A, which was in emission mode, switches to listening mode and waits for a response. - When circuit A receives a response it records the (I,Q) point of the received signal and determines the phase and then the distance modulo the wavelength that separates circuits A and B. - To resolve the uncertainty modulo the wavelength, the procedure then begins again with another frequency f, or measure the frame offset. - If at least three distances for three circuits B have been obtained in this way, circuit A determines its own geographical position.

[0103] In circuit B, the calculation unit 61 forms means for measuring a first phase shift between, on the one hand, an oscillating signal derived from a first clock of circuit A on signal 22, and, on the other hand, an oscillating signal derived from a second clock of circuit B.

[0104] In circuit A, means are formed for measuring a second phase shift between an oscillating signal derived from a first clock of circuit A and an oscillating signal derived from a second clock of circuit B, and for determining the distance of a device comprising circuit A relative to a base station comprising circuit B based on the first phase shift and the second phase shift.

[0105] Figure 9 shows a graph of experimental measurements with error bars for different distances for an apparatus and base station with the circuitry already shown, resolving uncertainties modulo the frequencies 2.4 GHz and 2.46 GHz. The y-axis of the graph corresponds to the actual distance and the x-axis corresponds to the calculated distance based on the flight times resulting from the two frequencies. In this example, the relationship between the calculated distance y and the actual distance x is y=x+25.7 centimeters.

[0106] The systematic offset of 25.7 centimeters corresponds to the time required by the components to amplify and demodulate the signal. Since this time length is fixed, it is easy to calibrate this time length and to deduce it systematically. It should be noted that if the frequencies of the equipment and the base station are equal, the round trip time has no influence at all on the determination of the distance. If these frequencies are not perfectly equal (Figure 5), the acquisition of the signal (22 at the remote base station side, and 27 or 33 at the equipment side) must be performed with a similar controlled time length between the moment the signal arrives at the antenna and the moment it is sampled by the calculation unit. The accuracy of the distance estimate in Figure 9 is between 1 millimeter and 3.25 millimeters depending on the distance.

[0107] FIG. 10 shows the error in estimating the offset at the points of two 64-point fixed periodic patterns as a function of the noise level on the signal, calculated over one and 100 periods of the pattern, namely error 78 and error 79. This error is measured by fast Fourier transform (FFT) and allows a better positioning accuracy than correlation. Thus, using a fixed periodic pattern that increases the range of available distances. In this case, FIG. 10 shows the effect of noise on the estimate of the offset when the fixed periodic pattern consists of 64 points, calculated using the Fourier transform of a 64-point spectrum with frequency 31 having constant amplitude and random phase. In this case, the sampling of the pattern is 20 MHz, and the error in estimating the offset is less than 1% of the sampling time with a noise of 0.63% of the signal when considering a fixed periodic pattern of a single period, and with a noise of 6.3% of the signal when considering a fixed periodic pattern of 100 periods. Thus, the error increases proportionally to the level of noise on the signal and decreases proportionally to the square root of the number of periods considered.

[0108] Fig. 11 describes the steps of an embodiment 80 of the method that is the subject of the present invention. During a step 81, circuit A emits a first signal 21. During a step 82, circuit B receives signal 22. During a step 83, circuit B determines the phase shift between signal 22 and the signal of its clock 72. During a step 84, circuit B includes a first phase shift in the response signal 26 or 31 depending on the operating mode (see Fig. 2 and Fig. 3). During a step 85, circuit B emits a response signal. During a step 86, circuit A receives the response signal. During a step 87, circuit A measures the phase shift between the received signal and its clock 72. Optionally, during a step 88, circuit A performs a resolution of the distance uncertainty. During a step 89, circuit A determines whether it has obtained at least four distances using four different base stations. If so, during a step 90, circuit A accesses the positions of the associated base stations from which it obtained its distances and determines the geolocation of the base stations. It can be seen that this position may also depend on information received from an internal unit attached to circuit A, and if at least five distances are received using a fixed base station, an algorithm can be used to determine the most probable position.

[0109] During a step 91, for example during low traffic periods, in particular at night, or when detecting an impact revealed by an internal sensor (not shown) contained in the base station, which may be the cause of an unexpected operation of this base station, the circuits B of the base stations update each other, performing steps 81 to 91, their respective positions. Periodically, for example annually, during a step 92, the circuits B of the base stations update each other and with the mobile base station, which is mobile and positioned at a point on the cadastral map, their respective positions, performing steps 81 to 90. During a step 93, they allocate time intervals (time slots) to the fixed base stations according to their respective positions, reducing the risk of collision downstream.

[0110] FIG. 12 shows an example of a pattern 101 with eight dots repeated three times, with no time gap between the repetitions.

[0111] For its positioning, the device 10 transmits a request to the base station 12, which preferably comprises at least one complete periodic pattern 101, for example between one and two periods 100 of this pattern 101. A request comprising more than one complete periodic pattern 101 is preferred, since when received, the sampling is perfectly synchronous and therefore it is possible to miss one point 103 of the transmitted signal. By transmitting not only at least one point 103 of the pattern 101 but also the complete pattern 101, this ensures that the complete pattern 101 is acquired. However, acquiring one complete period 100 allows a more accurate time shift calculation than would be the case with a simple correlation.

[0112] In some embodiments, the counter period is greater than twice the maximum flight time corresponding to a predefined maximum distance between the device 10 and a base station 12 that is likely to respond to a request from the device 10.

[0113] It should be noted that to meet this condition of avoiding the distance measurement being modulo the product of the counter half period and the signal propagation speed, a fixed length pattern or a variable length pattern 101 can be provided, for example by supplementing the pattern stored in memory with identical pattern segments (not shown) for all devices 10 and all base stations 12.

[0114] The device 10 and any base station 12 each include a counter that periodically scans n positions of pointers that point to memory areas where the values ​​of successive points of the pattern can be recorded and read out. These pointers are reset to zero when the last sample or point of the pattern has been read out. The periodicity of searching the n positions of the pattern is substantially equal in the device 10 and the base station 12, and these counters and pointers are not synchronized.

[0115] Below are described different embodiments of the invention that utilize these patterns 101. In the embodiments referenced below by A / and B / , the base station 12 acts like a repeater by re-emitting the patterns 101 that it receives, and therefore does not need to have the same repeating patterns as the device 10.

[0116] A / In some embodiments, upon receiving a fixed periodic pattern emitted by device 10, base station 12 records the fixed periodic pattern for at least one period and then re-emits the fixed periodic pattern to device 10 after a given integer number of periods 100 of the periodic pattern 101 in the order in which it was received.

[0117] This integer depends on the round trip time and therefore on the computation speed of the base station 12 and also on the time slots available to respond (some base stations can respond to a single request). Thus, at each period 100, it is as if the counter had been turned over to the starting point, and the value of the given number is not critical, provided that it is an integer. Nevertheless, this time before re-emission must be compatible with frequency drifts, for example, for 1 second with a frequency of 20 MHz and a 64-point pattern, the maximum integer being 312500. The integer used is preferably the number corresponding to the first time slot available.

[0118] When the device 10 receives the pattern re-emitted by the base station 12, it compares this pattern with its own fixed periodic pattern (e.g. by correlation or Fourier transformation) and deduce from this a time shift between the two emitted and received patterns, where the time shift is proportional to the distance between the device 10 and the base station 12 and inversely proportional to the speed of the electromagnetic waves.

[0119] B / In some embodiments, upon receiving the fixed periodic pattern emitted by the device 10, the base station 12 records the fixed periodic pattern for at least one complete period 100 and then re-emits the fixed periodic pattern in the order of reception starting from the nth sample, after the last sample received, until the n-1th sample received. Re-emission is thus performed after integer periods of the periodic pattern and fractions of a period, which fractions correspond to the ratio of the number n to the number of samples in the period 100 of the fixed periodic pattern 101, e.g. 8 for the pattern 101 shown in Fig. 12. Figs. 15 and 16 correspond to these embodiments.

[0120] By using a fraction of a period, one avoids responding at the instant indicated by an integer period of pattern 101. For example, if the response time slot was not precisely defined relative to the round trip time of base station 12, base station 12 could adjust its response time by simply waiting a fraction of this number rather than an integer period.

[0121] When the device 10 receives the pattern re-emitted by the base station 12, it compares this pattern with its own fixed periodic pattern 101 and deduce from this the time shift between the two emitted and received patterns, the time shift being proportional to the distance between the device 10 and the base station 12 and inversely proportional to the speed of the electromagnetic waves.

[0122] C / In some embodiments, upon receiving the fixed periodic pattern emitted by the device 10, the base station 12 compares this received pattern with its own fixed periodic pattern and deduces from this a first time shift between the device and the base station. The base station 12 then emits to the device 10 an item of information representing this first time shift as digital data for at least one period of its fixed periodic pattern 101. Upon receiving the fixed periodic pattern emitted by the base station 12, the device 10 compares this received pattern with its own fixed periodic pattern and deduces from this a second time shift. By reading the first time shift in the emitted data and adding these two time shifts to eliminate the absolute synchronization between the device 10 and the base station 12, the device 10 deduces the distance between itself and the base station 12.

[0123] D / In some embodiments, when the base station 12 receives the fixed periodic pattern emitted by the device 10, it stores the fixed periodic pattern in memory and then reads the fixed periodic pattern using a pointer. When it reads a point of the pattern 101, the device 10 emits the fixed periodic pattern to the base station 12, which in turn emits the fixed periodic pattern to the device 10. When the device 10 has emitted at least one period of the fixed periodic pattern, it sets its pointer to zero, reads the data using its pointer, and makes the data available to its IQ emission system, for example on the Q channel, while the I channel remains constant with respect to the phase measurement, as shown in FIG. 13.

[0124] When the base station 12 detects the receipt of a request, it stores the value of its own pointer when it receives the first IQ sample, and then, at the time of re-emission, periodically re-emits the fixed periodic pattern starting from the sample corresponding to the value of the pointer. Thus, when the device 10 detects the signal re-emitted by the base station 12, it can detect the phase due to the rotation of the IQ plane (FIG. 14), and then, upon realignment, it compares the transmitted pattern with its own fixed periodic pattern and from this deduce the time shift between the two patterns 101. Measuring the phase shift in the IQ plane makes it possible to improve the accuracy of the distance estimated by the pattern, particularly in the presence of significant noise in microwave communications.

[0125] In any of the embodiments described above, the sequence of steps may, in one variant, include using two separate communication channels simultaneously or sequentially, particularly when communication noise is high. The formula is repeated to

[0126] 12 shows a repeating period 100 of a pattern 101. Clocks in each device and each base station perform pattern memory and pointer synchronization to retrieve this pattern 101 with the same period 100.

[0127] 13 shows in the IQ plane an emitted signal 102 representing a pattern. The different possible values ​​of the pattern are indicated by points 103.

[0128] Figure 14 shows the received signal 104 in the IQ plane corresponding to the emitted signal 102. This received signal 104 comprises a point 108 for each point 103 of the emission pattern 102. The receiver of this signal, i.e. the base station in the case of a request and the device in the case of a response to a request, determines a linear fit 105 of the received points, then a line 106 perpendicular to the linear fit line 105, passing through the origin of the IQ plane, and then the phase 107 of the line 106. The difference between the phase 107 and the phase at reception (which is zero in the example of figure 13) corresponds to the phase shift between the emission of this signal and its reception, measured with the phase-shifted pointer itself. By using the present invention, it is possible to eliminate the phase shift of this pointer and measure the phase shift only by the time of flight (TOF) of the outgoing signal (from the device to the base station) and the return signal (from the base station to the device).

[0129] Thus, the emitter (which may be the device 10 or the base station 12 depending on the direction of communication) transmits a constant on the I channel and at least one period of its fixed periodic pattern on the Q channel, resulting in an IQ diagram where I on the x-axis is constant while Q on the y-axis varies, resulting in a series of vertically aligned points. During emission, the propagation delay rotates the IQ plane through one complete revolution per wavelength. Thus, upon reception, the received IQ points are aligned in the IQ plane of the receiver, but on a line tilted from the vertical at an angle corresponding to the fraction of a wavelength that separates the emitter from the receiver. It is a simple way to determine the information and thus estimate, for example after regression, a straight line fit 105, i.e. the slope of the line on which the received IQ points are aligned. From this line 105, we extrapolate the distance to the origin of the IQ plane that corresponds to the constant I transmitted and gives a reference point on the line, and the rotation angle whose cotangent is simply the slope of the line.

[0130] The phase shift obtained in this way provides fine-scale information about the distance between the emitter and receiver.

[0131] Of course, the value carried by the I channel does not have to be constant, and the pattern 101 does not have to be carried by the Q channel. The emitted signal may be phase shifted at the time of emission, for example as shown with reference to Fig. 14, and knowledge of the phase at the time of emission is sufficient for the instrument to determine the total phase shift due to the time of flight of the outgoing and return signals. By measuring the phase over the entire pattern after the linear fit 105, the accuracy of the estimated distance can be improved, in particular when the noise is too large.

[0132] 15 and 16 show a complete round trip sequence for a pattern with eight samples. The optional use of carrier phase shift measurements to increase the accuracy of the distance determination will not be detailed again.

[0133] Figure 15 shows a transmission, i.e. the emission (top) and reception (bottom) of a request signal modulated by a pattern 101. The top line shows the position 110 of a pointer 10. This pointer periodically scans the eight values ​​of the pattern 101 (indexed 0 to 7) stored in memory. When a signal is emitted, it stores the value of the pattern 101 for at least one period 100 at the memory location pointed to by the pointer for modulating the emitted signal 111. Due to the distance between the device 10 and the base station 12, the signal 112 received by the base station 12 is shifted in time with respect to the emitted signal by a delay 113. In the remainder of the description of FIG. 15, the base station 12 sets its pointer to zero when it receives the first sample representing a point of the pattern carried by the received signal 112, as indicated by the pointer value 114. Of course, it is not necessary to reset the pointer to zero, as will be described with reference to FIG. 16. For example, the position of the pointer when the first sample is received can be stored by the base station 12 and used as a starting position for transmitting the pattern to the device.

[0134] The time length 115 is the time for sampling the received signal 112 and for storing the value of the pattern that the signal carries.

[0135] FIG. 16 illustrates the transmission, ie the emission (bottom) and reception (top) of a response signal 119 in response to the request 112 shown in FIG.

[0136] After the base station 12 receives the first sample of the received signal 112, the base station pointer 114 therefore becomes - to the value "0" if this pointer was reset to zero when this first sample of the pattern was received, or - the value this pointer had when this first sample was received Upon return, it will start sending the pattern after 100 integer periods.

[0137] During at least one period 100, points of a pattern 111 are emitted by the base station 12 to the device 10. Due to the distance between the base station 12 and the device 10, the signal 119 received by the device is shifted in time by a delay 118 equal to the delay 113 relative to the signal emitted by the base station. By measuring the time shift between the pattern read by the pointer 110 of the device 10 and the pattern 119 received from the base station 12, the device 10 can determine the total time of flight of the outgoing and return signals and from this estimate the distance between the device 10 and the base station 12.

[0138] Note that the periodic emission pattern does not need to be common to all devices 10 and all base stations 12, nor does it need to persist beyond the time required to determine the distance between the device 10 and the base station 12.

[0139] In particular, in embodiments A and B, the pattern does not need to be known to the base station 12 that is used as a repeater.

[0140] However, the times between two points in the pattern 101 must be known by the base station 12 so that the samples of the received signal correspond to these points.

[0141] The point in the pattern to which the counter of the instrument 10 is pointing must be known by the base station 12 if the base station 12 is to make an offset or phase shift measurement.

[0142] As can be understood from reading the above description, a system 9 for locating a device 10 comprises said device 10 and a number of fixed base stations 12. The device 10 comprises an emitter configured to emit a request comprising at least one pattern of points whose values ​​are read with a pointer of the device searching for a location in a pattern memory, the emitter of the device amplitude- and / or phase-modulating a carrier wave with the values ​​of the points of the pattern read out in sequence.

[0143] Each base station 12 comprises an emitter configured to respond to requests with responses corresponding to the implementation fluids AD described above.

[0144] In embodiments A and B, the response repeats the pattern that the base station 12 received from the device 10, and a pointer in the base station searches memory locations, writing there the values ​​of the points of the received pattern, and then searches these memory locations and reading therefrom the values ​​of the points of the pattern to be emitted, so that each point in the pattern is offset in time by multiples of the period of the base station's counter relative to the time the base station received the pattern.

[0145] In embodiment C, the response represents a first pattern time shift measured by the base station 12 between the received pattern and the same pattern stored in the memory of the base station 12 whose values ​​were retrieved by the base station's 12 pointer. This first time shift is inserted into the data, for example in the frame forming the response, together with the accompanying emitted pattern. The values ​​of the points of the response pattern are read sequentially from the device's known position in the memory locations retrieved by the base station's pointer.

[0146] The emitter of the base station 12 also amplitude and / or phase modulates a carrier wave with the values ​​of the points of the sequentially read out pattern.

[0147] The device 10 also includes means 61 for measuring a second time pattern offset between the value of the pattern point received in each response and the value stored in the memory of the device 10 at the position sequentially retrieved by the pointer of the device 10; -The distance between the device and the base station, In embodiments A and B, the total pattern offset between the pattern originally emitted by the device 10 in the request and the pattern repeated by the base station 12 and received by the device 10 from this base station 12; In embodiment C, the second pattern offset measured by the device 10 and the first pattern offset measured by the base station 12 . as a function of Equipped with.

[0148] The device 10 also comprises means 61 for determining the location of the device as a function of the known location of each responding fixed base station and the distance to each of these base stations, as determined by the determining means.

[0149] The accuracy of a positioning system based solely on pattern offset measurements is the product of twice the time length between the emission of two points of the pattern and the propagation speed of the signal.

[0150] In some preferred embodiments, the device 10 comprises means for measuring the phase shift of the carrier of the received signal relative to the phase of the sinusoidal signal generated by its own clock. In the case where the base station 12 comprises means for measuring the pattern offset (embodiment C), this base station 12 also preferably comprises means for measuring the phase shift of the carrier of the signal received from the device relative to the phase of the sinusoidal signal generated by the device 12's clock.

[0151] This phase shift can be measured as described with reference to FIGS.

[0152] The means for determining distance of the device 10 adds the total phase shift measured for the signal round trip to the total phase shift measured for that round trip to determine the distance from the device to each base station.

[0153] As described above, in some embodiments, the signals emitted by the device 10 and each base station 12 are in IQ orthogonal. At least one predefined carrier of the signals is in IQ orthogonal. For a given phase shift, the signal on the I channel is constant and the signal on the Q channel carries an amplitude modulation of the pattern emitted by the device. Preferably, the predefined phase shift is zero, as shown in Figure 13.

[0154] Moreover, to measure the first and second offsets, the base station and the equipment comprise means for performing a linear fit of the points of the received pattern in the IQ plane. The measured phase shift is thus - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift (zero in the case shown in Figure 13) is equal to the difference between

[0155] The measured offset, which is used to measure the distance between the device and the base station, is therefore equal to the sum of the pattern offset and the phase shift measured in this manner.

[0156] In some embodiments, c) each base station comprises means for performing a straight line fit of the points of the received pattern in the IQ plane and means for measuring a phase shift, the measured phase shift being - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift is equal to the difference between each base station emitter is configured to emit an IQ signal with a negative phase shift of twice the measured phase shift with respect to the received signal such that the phase of the signal emitted by the base station is in phase with the signal emitted by the device; d) the apparatus comprises means for performing a straight line fit of the points of the received pattern in the IQ plane and means for measuring a phase shift, the measured phase shift being - the angle between a vertical line in this plane and the line obtained by straight line fitting, -This predefined phase shift is equal to the difference between The total offset used by the instrument to measure the difference is the sum of the total pattern offsets plus the phase shift measured by the instrument's measurement means.

[0157] As a result of each of these arrangements, the accuracy of the positioning system is twice the ability to discriminate the phase shift of a number of n collinear pattern points in the IQ plane times the propagation speed of the signal. Due to the number of n points in the pattern, this accuracy is even higher than can be obtained by measuring the phase shift of a simple sinusoidal signal.

[0158] In some embodiments, the patterns emitted by all devices and all base stations are identical, thus making the implementation of the invention easier at the stage of the means for measuring the temporal pattern offset.

[0159] In some embodiments, the patterns emitted by at least two different devices are different, and the signal emitted by each device comprises data identifying or representative of the pattern emitted by that device. Thus, to measure the pattern offset in time, the base station can identify the device, or the device itself can identify its own pattern.

[0160] In some embodiments, the patterns emitted by at least two different base stations are different, and the signal emitted by each base station comprises data identifying or representative of the pattern emitted by that base station, such that a device can identify each base station by the patterns it receives.

[0161] In some embodiments, each signal emitted by a base station is an identifier for that base station and The determining means of the device is configured to determine the location of the base station using the identifier of the base station.

[0162] In some embodiments, the identifier of the base station comprises a geographic location of the base station.

[0163] According to a second aspect, the invention contemplates an apparatus of the system that is the subject of the invention.

[0164] According to a third aspect, the invention envisages a base station of the system that is the subject of the invention.

[0165] In some particular embodiments of this base station, it acts like an equipment towards other base stations verifying its positioning, and the emitter is configured to emit a displacement message if the determined position differs from an already stored position of this base station.

[0166] In this way the base station can verify and, if necessary, update its cadastral position. - Geographical calibration of the network of distances between base stations is easy to implement, not time-consuming or labor-intensive, and therefore not cost-intensive. By periodically measuring the distance network, it is possible to check that the distance network is functioning and therefore to constantly verify this, to detect malfunctions and, if necessary, to correct errors.

[0167] FIG. 17 illustrates a method for positioning the device 10 in a system including the device 10 and multiple fixed base stations 12.

[0168] This method 130 is a step 131 of emitting, by the device, a request comprising at least one pattern of points whose values ​​are read at a pointer of the device which searches a location in the pattern memory, the emitter of the device modulating a carrier wave with the values ​​of the points of the pattern which are successively read; a step 132 of receiving a first signal by the base station 12; a step 137 of emitting a response by each base station that receives this request; a step 138 of measuring, by the device 10, a second temporal pattern offset between the value of the pattern point received in each response and the value stored in the memory of the device 10 at the position sequentially accessed by the pointer of the device; a step 139 of determining, by the device, distances between the device and at least four base stations 12; a step 140 of determining, by the device, the location of the device as a function of the known locations of each of the responding fixed base stations and of the distance to each of these base stations determined by the determination means; Equipped with.

[0169] Preferably, the first signals are in quadrature as shown in FIG.

[0170] Preferably, - during step 133, a straight line fit is carried out by the base station 12 as described above, in particular with reference to FIG. 14; - during a step 134, a first phase shift measurement is performed, - during a step 135, a first offset measurement is performed by the base station 12, During a step 136, data representative of the measured phase shift and offset are incorporated into a second signal corresponding to a response to a request emitted by the base station 12 on behalf of the device 10. Enter, - Step 138 comprises measuring the phase shift after linear adaptation.

[0171] The method 130 corresponds to embodiment C, and in a variant corresponding to embodiments A and B, the base station 12 acts like a repeater of the pattern received from the device 10. Therefore, the base station 12 does not need to measure the pattern offset. Nevertheless, the base station 12 - the carrier of the reply signal can be in phase with the received pattern and can carry a measurement of the phase shift between the received pattern and its own clock, or The carrier of the response signal can be phase shifted so that it is synchronized with the carrier of the request signal.

[0172] These two alternatives allow the device to measure the total phase shift due to the outgoing request and the return response, and therefore to refine the measurement of the distance between the device 10 and the base station 12.

[0173] It should be noted that the method may not only involve the device repeating the pattern it receives, but may also comprise transmitting measurements of the offset made by the base station.

[0174] Steps 91-93 have already been described in detail with respect to Figure 11. Steps 91 and 92 may utilize distance measurements based on pattern offsets and / or phase shifts of the carrier and / or pattern.

[0175] The invention also relates to the use of the method and / or device that is the subject of the invention for guiding ground or aircraft vehicles, guiding pedestrians, guiding visually impaired or motor impaired persons in indoor or outdoor environments, geolocating elements in indoor or outdoor environments, indicating parking errors for self-driving vehicles, determining the position and orientation of visualization systems with several devices for augmented reality purposes for civil engineering, leisure and travel applications, determining gestures or motion capture, for example for gesture interfaces.

Claims

1. A system (9) for positioning a device, comprising the device (10) and a plurality of fixed base stations (12), wherein the device comprises a counter that periodically searches for n pointer positions (110), and each base station comprises a counter that periodically searches for n pointer positions (114) during a period substantially equal to the period for the counter of the device to search for a value of n in a system (9). - The device comprises emitters (66-70, 72, 73) configured to emit a request comprising at least one pattern (101, 110) consisting of points (103) at which values are read by a pointer of the device searching for positions in a pattern memory, and the emitters of the device amplitude modulate and / or phase modulate a carrier wave with the values of the points of the sequentially read pattern. - Each base station that receives this request comprises emitters (66-70, 72, 73) configured to respond to the request with a response (119). a) The response repeats the pattern received by the base station from the device, and the pointer of the base station searches for the memory positions of the pattern to enter the values of the points of the pattern therein, and then searches for these memory positions to read out the values of the points of the pattern to be emitted. Thus, each point of the pattern is temporally offset by a multiple of the period of the counter of the base station with respect to the time when the base station received the pattern. b) The response represents a first temporal pattern offset measured by the base station between the received pattern and the same pattern stored in the memory of the base station whose value was searched by the pointer of the base station. The values of the points of the response pattern are sequentially read from a known position by the device at the memory positions searched by the pointer of the base station, and the emitters of the base station modulate the carrier wave with the values of the points of the sequentially read pattern. The device also comprises - means (61) for measuring a second temporal pattern offset (29, 36) between the values of the points of the pattern received in each response and the values stored in the memory of the device at the positions sequentially searched by the pointer of the device; - the distances between the device and the base stations respectively a) the total pattern offset between the pattern emitted by the device and the repeated pattern received by the device from the base station; b) means (61) for determining as a function of a second pattern offset and a first pattern offset measured by the base station; and - means (61) for determining the position of the device as a function of the known positions of each of the fixed base stations that have responded and the distances to each of these base stations determined by the means for determining; comprising a system (9) characterized in that. **Claim 2** When the device (10) and each base station (12) comprise the means (61) for measuring the pattern offset, each base station (12) measures the phase shift of the carrier wave of the received signal with respect to the clock of the device and, when each base station comprises the means for measuring the offset, the phase of the sine wave signal generated by the clock of each base station. The means (61) for determining the distance of the device adds the measured phase shift to the measured offset to determine the distance from the device to each base station. The system (9) according to claim 1. **Claim 3** The signals (102) emitted by the device (10) and the base station (12) are in an IQ quadrature state. With respect to at least one predefined phase shift of the carrier wave of the signal, the signal on the I channel is constant and the signal on the Q channel carries the amplitude modulation of the pattern (101, 111) emitted by the device. The system (9) according to claim 2. **Claim 4** To measure a first offset and a second offset, the base station (12) and the device (10) comprise means (61) for performing a linear fit (105) of points (108) of the pattern (112, 119) received in the IQ plane. Each measured offset is equal to the sum of the pattern offset and the measured phase shift, and the measured phase shift is - the angle (107) between a perpendicular line in the plane and the line obtained by the linear fit - and the predefined phase shift equal to the difference between. The system (9) according to claim 3. **Claim 5** c) Each of the base stations (12) comprises means (61) for performing the linear fitting (105) of the points (108) of the pattern (112) received in the IQ plane, and means (61) for measuring the phase shift, the measured phase shift being - the angle between a vertical line in said plane and the line obtained by linear fitting - this predefined phase shift equal to the difference between, The emitters (66-70, 72, 74) of each of the base stations are configured to emit an IQ signal phase-shifted by twice the measured phase shift in the negative direction with respect to the received signal such that the phase of the signal emitted by the base station is in phase with the signal (102) emitted by the device (10). d) The device comprises means (61) for performing the linear fitting (105) of the points of the pattern (119) received in the IQ plane, and means (61) for measuring the phase shift, the measured phase shift being - the angle between a vertical line in said plane and the line obtained by linear fitting - this predefined phase shift equal to the difference between, The total offset used by the device to measure the difference is the sum of the total pattern offset and the sum of the phase shifts measured by the means for measuring by the device. The system (9) according to claim 3.

6. The period (100) of the counter is greater than twice the maximum flight time corresponding to a predefined maximum distance between the device (10) and the base station (12) likely to respond to a request from this device, the system (9) according to any one of claims 1-5.

7. The pattern (75) consisting of n points is the inverse Fourier transform (76) of a spectrum (77) having a constant amplitude and a random or pseudo-random phase, the system (9) according to any one of claims 1-5.

8. Each of the emitters (66-70, 72, 73) of the device (10) and the base station (12) is configured to emit signals on a plurality of carriers having different frequencies, the system (9) according to any one of claims 1-5.

9. The patterns (101) emitted by all of the devices (10) and all of the base stations (12) are identical, the system (9) according to any one of claims 1-5.

10. The patterns (101, 111) emitted by at least two different said devices (10) are different, and the signal emitted by each said device comprises data for identifying or representing the pattern emitted by this said device. The system (9) according to any one of claims 1 to 5.

11. The patterns (100, 119) emitted by at least two different said base stations (12) are different, and the signal emitted by each said base station comprises data for identifying or representing the pattern emitted by this said base station. The system (9) according to any one of claims 1 to 5.

12. Each signal (45, 49) emitted by the base station (12) comprises an identifier of this said base station, and the means (61) for determining the device (10) is configured to determine the position of this said base station using the identifier of this said base station. The system (9) according to any one of claims 1 to 5.

13. The identifier of the base station (12) comprises the geographical location of the base station (12). The system (9) according to claim 12.

14. The frequencies of the signals emitted by all said devices (10) and all said base stations (12) are in the ISM (Industrial, Scientific, and Medical) band. The system (9) according to any one of claims 1 to 5.

15. A device (10), which is the device (10) of the system (9) according to any one of claims 1 to 5.

16. A base station (12), which is the base station (12) of the system (9) according to any one of claims 1 to 5.

17. Configured to behave like a device directed to another base station (52) to verify the positioning of the device, and the emitters (66 - 70, 72, 73) are configured to emit a displacement message if the determined position is different from the already stored position of this said base station. The base station (12) according to claim 16.

18. Configured to behave like a device directed to another base station related to a cadastral map point to determine the position of the device. The base station (12) according to claim 16.

19. A method (80, 130) for positioning a device in a system comprising a device (10) and a plurality of fixed base stations (12), wherein the device comprises a counter that periodically searches for n pointer positions (110), and each base station comprises a counter that periodically searches for n pointer positions (114) during a period substantially equal to the period for the counter of the device to search for a value of n, in the method (80, 130). - A step (131) of emitting, by the device, a request comprising at least one pattern (101, 111) consisting of points at which values are read by a pointer of the device searching for positions in a pattern memory, wherein an emitter of the device modulates a carrier wave with the values of the points of the sequentially read pattern in step (131). - A step (136, 137) of emitting, by each base station receiving the request, a response (119). a) The response repeats the pattern received by the base station from the device. The pointer of the base station searches for the memory position of the pattern and enters the values of the points of the pattern therein. Then, these memory positions are searched to read the values of the points of the pattern to be emitted. Thus, each point of the pattern is temporally offset by a multiple of the period of the counter of the base station with respect to the time when the base station received the pattern. b) The response represents a first temporal pattern offset measured by the base station between the received pattern and the same pattern stored in the memory of the base station where values were searched by the pointer of the base station. The values of the points of the response pattern are sequentially read at the memory positions searched by the pointer of the base station from a known position of the device. An emitter of the base station modulates a carrier wave with the values of the points of the sequentially read pattern in steps (136, 137). - A step (138) of measuring, by the device, a second temporal pattern offset between the values of the points of the pattern received in each response and the values stored in the memory of the device at positions sequentially searched by the pointer of the device. - By the device, the distance between the device and the base station is respectively a) the total pattern offset between the pattern emitted by the device and the repeated pattern received by the device from the base station b) determining, as a function of the second pattern offset and the first pattern offset measured by the base station (139); - determining, by the device, the position of the device as a function of the known positions of each of the fixed base stations that responded and the distances to each of these base stations determined by the means for determining (140); - a method (80, 130), characterized in that it comprises: Method (80, 130), characterized by comprising: **Claim 20** A method (80, 130) according to claim 19, comprising allocating a time interval or time slot to the fixed base stations (12) according to the geographical location of the fixed base stations (12) such that two fixed base stations that exchange signals with the same fixed base station are not assigned the same time interval for each of the two fixed base stations and for this same fixed base station (93). **Claim 21** A method (130) according to claim 19 or 20, comprising positioning the fixed base station relative to other base stations associated with points on a cadastral map (92). **Claim 22** A method according to claim 19 or 20 (130), for guiding a ground vehicle (11) or an aircraft, guiding a pedestrian indoors or outdoors, indicating a parking error for a self-driving vehicle, geographically positioning elements in an environment, and determining the position and orientation of visualization systems comprising several devices for the purpose of augmented reality for civil engineering, leisure, and travel applications, for example determining gestures for a gesture interface or motion capture. **Claim 23** A method of using the system (9) according to any one of claims 1 to 5, for guiding a ground vehicle (11) or an aircraft, guiding a pedestrian indoors or outdoors, indicating a parking error for a self-driving vehicle, geographically positioning elements in an environment, and determining the position and orientation of visualization systems comprising several devices for the purpose of augmented reality for civil engineering, leisure, and travel applications, for example determining gestures for a gesture interface or motion capture.

24. A method of using the device (10) according to claim 15, which guides a ground vehicle (11) or an aircraft, guides pedestrians indoors or outdoors, indicates parking errors for a self-vehicle, geographically arranges elements in the environment, determines the position and orientation of a visualization system comprising several devices for the purpose of augmented reality for civil engineering, leisure, and travel applications, and determines gestures, for example for a gesture interface, or motion capture.

25. A method of using the base station (12) according to claim 16, which guides a ground vehicle (11) or an aircraft, guides pedestrians indoors or outdoors, indicates parking errors for a self-vehicle, geographically arranges elements in the environment, determines the position and orientation of a visualization system comprising several devices for the purpose of augmented reality for civil engineering, leisure, and travel applications, and determines gestures, for example for a gesture interface, or motion capture.

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