Method and electronic module for detecting the internal or external position of an electronic device

Abstract

In a method for detecting the internal or external position of an electronic device exchanging a signal carried by electromagnetic waves with a remote telecommunications system, the following steps are provided: - measurement of a value (Lk) of a quantity characteristic of the exchanged signal; - application of the measured value (Lk) to the input of a Kalman filter (5) producing at the output a filtered estimate (Ek) of said quantity; - comparison of a statistical value (Tk2) determined as a function of said filtered estimate (Ek) to a threshold (γ) in order to detect the internal or external position of the electronic device (M). An associated electronic module is also described. Figure for the abstract: Figure 2

Description

Title of the invention: Method and electronic module for detecting the internal or external position of an electronic device Technical field of the invention

[0001] The present invention relates to the technical field of telecommunications.

[0002] The invention relates in particular to a method for detecting the internal or external position of an electronic device and an associated electronic module. State of the art

[0003] We have already sought, for example in the article "Indoor outdoor user discrimination in mobile wireless networks" by E. Villebrun, A. Ben Hadj Alaya, Y. Boursier and N. Noisette, in IEEE Vehicular Technology Conference, September 2006, to detect the indoor or outdoor position of a mobile terminal, in order for example to allocate particular resources of the telecommunications network to it according to the estimated position.

[0004] Such techniques are relatively simple to implement, but their reliability is limited, which reduces their practical interest.

[0005] Artificial intelligence-based solutions have been proposed, but they require significant computing resources, which also makes them difficult to use in practice. Presentation of the invention

[0006] In this context, the invention proposes a method for detecting the internal or external position of an electronic device (for example, a mobile terminal) exchanging a signal carried by electromagnetic waves with a remote telecommunications system, the method comprising the following steps:

[0007] - measurement of a value of a characteristic quantity of the exchanged signal;

[0008] - application of the measured value at the input of a Kalman filter producing in output a filtered estimate of said quantity;

[0009] - comparison of a statistical value determined according to said estimate filtered at a threshold in order to detect the internal or external position of the electronic device.

[0010] The Kalman filter can be implemented easily and improves the robustness of detection.

[0011] The statistical value may depend, for example, on a likelihood ratio of two statistical hypotheses respectively representative of the internal and external positions of the electronic device.

[0012] The aforementioned quantity may be a logarithm of a ratio between a useful signal power and a disturbance power affecting that signal. This quantity is, for example, a logarithm of a signal-to-interference-to-noise ratio, or of a signal-to-noise ratio. According to other embodiments, the quantity may be a power of the received signal, or the received power of a reference signal, or even the logarithm of one of these quantities.

[0013] The aforementioned comparison can in practice use a generalized likelihood ratio test.

[0014] As explained in the description below, the statistical value can in some embodiments be calculated by squaring the difference between the filtered estimate and a predetermined value, which allows for a very simple implementation.

[0015] The threshold can be determined according to a desired false alarm rate.

[0016] The method may include a step in which resources from a telecommunications network, including the remote telecommunications system, are allocated to the electronic device according to the estimated position.

[0017] The invention also proposes an electronic module for detecting the internal or external position of an electronic device exchanging a signal carried by electromagnetic waves with a remote telecommunications system, characterized by:

[0018] - a Kalman filter configured to receive (as input) a value of a quantity characteristic of the exchanged signal and produce (at output) a filtered estimate of said quantity;

[0019] - a comparison unit configured to compare a statistical value determined based on said estimate filtered at a threshold in order to detect the internal or external position of the electronic device.

[0020] The comparison unit can be configured to calculate the statistical value by squaring the difference between the aforementioned filtered estimate and a predetermined value, as is the case in the example described below.

[0021] The electronic module can be integrated into the electronic device or the remote telecommunications system, or even into another electronic device. Detailed description of the invention

[0022] In addition, various other features of the invention become apparent from the attached description made with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0023] [Fig-1] is a diagram representing a context of use of the invention;

[0024] [Fig.2] represents elements of an electronic module enabling the detection of the internal or external position of an electronic device;

[0025] [Fig.3] is a flowchart showing the steps of a method for detecting this indoor or outdoor position;

[0026] [Fig.4] represents the evolution of a statistical value used within the module electronics of [Fig. 2], which includes a Kalman filter; and

[0027] [Fig.5] represents the evolution of the same statistical value in the absence of the filter of Kalman.

[0028] A possible context for implementing the invention has been schematically represented in [Fig.1].

[0029] An electronic device M (here a mobile terminal, or "user equipment" according to the terminology used in some standards) and a telecommunications system S (here a base station of a mobile telecommunications network), distant relative to the electronic device M, exchange signals carried by electromagnetic waves emitted by the telecommunications system S and received by the electronic device M, or, conversely, emitted by the electronic device M and received by the telecommunications system S.

[0030] As explained below, we seek here to determine whether the electronic device M is located inside a (any) building B (i.e. in an indoor environment) or outside any building (i.e. in an outdoor environment), in other words to detect the indoor position I or outdoor position O of the electronic device M.

[0031] Such detection is carried out by an electronic module as described below with reference to [Fig.2] on the basis of a value (obtained by measurement) of a quantity characteristic of a signal exchanged between the electronic device M and the telecommunication system S.

[0032] This characteristic quantity is, for example, a ratio between a useful signal power and a disturbance power affecting that signal, such as the signal-to-interference-plus-noise ratio (SINR), or, in practice, the logarithm of such a ratio. Other quantities can also be used (as well as the logarithm of these quantities), such as the difference between the uplink SINR and the downlink SINR, or the signal-to-noise ratio (SNR), or the received signal power (RSSI), or the received signal power of a reference signal (RSRP). Thus will emerge from the following, we preferably use a quantity whose values ​​follow a Gaussian (or normal) probability law (or distribution).

[0033] Such an electronic module may be part of the telecommunications system S, or of the electronic device M, or of another electronic device (distinct from the telecommunications system S and the electronic device M).

[0034] The measurement of the characteristic magnitude of the exchanged signal can be carried out by the electronic entity (telecommunication system S, or electronic device M, or other electronic device) which integrates the electronic module within itself.

[0035] For example, when the electronic device M emits a signal to the telecommunications system S and the telecommunications system S integrates the electronic module, the telecommunications system S can measure the characteristic magnitude of the signal received from the electronic device M, so that the electronic module (made for example in accordance with [Fig.2] described below) can detect the internal or external position of the electronic device M on the basis of the measured values.

[0036] Alternatively, the measurement of the characteristic magnitude of the exchanged signal can be carried out by an electronic entity other than the electronic unit which integrates the electronic module within itself, in which case this other electronic entity transmits the measured values ​​to the electronic entity integrating the electronic module.

[0037] For example, in the event of the emission of a signal by the telecommunication system S and the reception of this signal by the electronic device M, the electronic device M can measure a quantity characteristic of the received signal and transmit the measured values ​​to the telecommunication system S so that an electronic module integrated into the telecommunication system S and made in accordance with what is described below with reference to [Fig.2] detects the internal or external position of this electronic device M on the basis of the measured values ​​received by the telecommunication system S.

[0038] Fig. 2 represents the elements of an electronic module for detecting the internal or external position of an electronic device.

[0039] This electronic module includes a Kalman filter 5 and a comparator unit 10.

[0040] The Kalman filter 5 receives at input successive values ​​Lk (respectively associated with different measurement instants) of a quantity characteristic of the exchanged signal in order to produce at output (for each of these measurement instants) a filtered estimate Ek of this characteristic quantity.

[0041] This characteristic quantity is here the logarithm of the signal-to-interference-to-noise ratio (SINR).

[0042] For each measurement instant (or in other words for each Lk value of the characteristic quantity), the Kalman filter 5 performs:

[0043] - a prediction phase during which the filtered estimate Ek.i is used obtained for the previous instant as prediction Epk of the state for the current instant (Epk = Ek_i) and during which the prediction Ppk of the variance of the state for the current instant is obtained by adding an evolution variance Q (or "process variance"') to the variance of the state estimated at the previous instant Pk_b i i Ppk = Pk i + Q (the evolution variance Q being for example determined as a function of the variance of the measurement noise R, with here Q = 0.1.R);

[0044] - an update phase during which the Kalman gain K is determined such as the ratio between the prediction Ppk of the variance of the state and the sum of this prediction Ppk and the variance of the measurement noise R (K=Ppk / (Ppk+R)), in which the filtered estimate Ek is obtained by adding to the prediction Epk of the state the product of the Kalman gain K and the difference obtained by subtracting the prediction Ep k of the state from the value Lk received at the input of the Kalman filter 5 (Ek = Epk + K.(Lk - Epk)), and in which the variance Pk of the state is estimated by multiplying the prediction Ppk of the variance of the state by a factor obtained by subtracting the Kalman gain from the number 1: Pk = (lK).Ppk (all these values ​​being relative to the current time, identified by the index k).

[0045] The estimated state in this Kalman filter 5 is therefore the characteristic quantity itself.

[0046] To determine the current filtered estimate Ek, the Kalman filter 5 here uses only values ​​relative to the previous time and the current time, and the electronic module therefore does not need to store a history of past values ​​(as might be the case using other filtering solutions).

[0047] The comparison unit 10 is designed to compare a statistical value Tk2 determined according to the filtered estimate Ek to a threshold in order to detect the inside or outside position of the electronic device M.

[0048] Here, we consider that the values ​​of the filtered estimate Ek can conform to two distinct probability distributions depending on whether the electronic device M has an interior or an exterior position:

[0049] - in the assumption Ho where the electronic device M is outside, the values ​​of the filtered estimate Ek conforms to a Gaussian distribution of mean value (or expectation) q0 and standard deviation o0 (or, in other words, of variance o02);

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[0066] - in the hypothesis Hi where the electronic device M is inside, the values ​​of the filtered estimate Ek conform to a Gaussian distribution with mean value (or expectation) qi and standard deviation <q (ou, autrement dit, de variance gi2). on introduit la métrique statistique tk - q0 (cette est ainsi différence entre l’estimation filtrée ek et valeur moyenne q0). les densités probabilités des distributions gaussiennes peuvent alors s’écrire : pour l’hypothèse ho (dispositif électronique m à l’extérieur) i tjhnl="T^^expi" j \ y 7              -af>i - for hypothesis Hi (electronic device M inside): L|M t 1T AH, = 7^^ exn - —77— with Aq = [q - q0. To detect the internal (hypothesis Hi) or external (hypothesis Ho) position of the electronic device M, the comparison unit 10 uses the Neyman-Pearson decision criterion: where q is a threshold regulating the false alarm rate and A is the likelihood ratio: A eXO, 2.0-2 - 2cr2 J Comparison unit 10 here uses the generalized likelihood ratio test (or GLRT for "Generalized Likelihood Ratio Test") which takes the criterion defined above and sets certain parameters to estimated values ​​of these parameters, here the parameters Aq, o0 and o, : - the parameter is estimated by the maximum likelihood estimator (or MLE stands for "Maximum Likelihood Estimate") in the Hi assumption: A fi- argmax-i= exd - -730- = Tk - standard deviations are considered equal to each other and to have the same estimated value; o0 = Oi = &. The values ​​$ and q0 can be estimated by preliminary tests or during a calibration phase.

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[0081] In other words, the comparison unit 10 applies the Neyman-Pearson criterion defined above with o0 = ch = $ and Au = Tk, so that the likelihood ratio can be written: yt = exp(^j and the test performed by the comparison unit 10 amounts to the following comparison: Tl J 2ô-2ln The statistical variable Tk2 follows a chi-squared distribution with one degree of freedom under the assumption Ho: and the test performed by the comparison unit 10 can therefore be written: where a is the false alarm rate and 2M corresponds to the (la)-quantile of the chi-square distribution with one degree of freedom. The comparison unit 10 includes a subtraction block 12 which subtracts the value q0 from the filtered estimate Ek received as input to the comparison unit 10 in order to obtain the value Tk of the metric introduced above. The comparison unit 10 also includes a squaring block 14 which receives the value Tk produced by the subtraction block 12 and outputs the statistical value Tk2. The comparison unit 10 finally includes a comparison block 16 which receives the statistical value Tk2 produced by the squaring block 14, compares this statistical value Tk2 to a threshold y and produces as output the estimated position P as a function of the result of the comparison performed: - if the statistical value Tk2 is greater than the threshold y, the estimated position P indicates that the electronic device M is located inside a building; - if the statistical value Tk2 is less than the threshold y, the estimated position P indicates that the electronic device M is located outside. As explained above, the threshold value y used here is the product of the estimated standard deviation $ and the value 2 M of the (1- a)-quantile of the chi-squared distribution ^ï-aV / with one degree of freedom, where a is the false alarm rate. The threshold y therefore depends here on the desired false alarm rate.

[0082] Fig. 3 is a flowchart showing the steps of a method for detecting this internal or external position.

[0083] This process is partly implemented here in the electronic module just described with reference to [Fig. 2]. Specifically, steps E6 to E10 described below are implemented by the electronic module of [Fig. 2].

[0084] The process begins with a step E2 of measuring a value Lk of a quantity characteristic of the exchanged signal.

[0085] We are considering, for example, the case where the electronic device M receives a signal carried by an electromagnetic wave emitted by the telecommunication system S and where the electronic device M measures (at different successive times) a value Lk of the logarithm of the signal-to-interference-to-noise ratio (or SINR) of the received signal.

[0086] It is also considered here that the electronic module of [Fig.2] is part of the telecommunication system S.

[0087] The process then includes a step E4 (carried out here by the electronic device M) of transmitting the value Lk to the telecommunication system S so that this value Lk is available for processing by the electronic module of the [Fig.2].

[0088] This electronic module can thus apply the value Lk to the input of the Kalman filter 5, which makes it possible to produce the corresponding filtered estimate Ek at the output of the Kalman filter 5 (step E6).

[0089] The comparison module 10 determines (using the subtraction block 12 and the squaring block 14) the statistical value Tk2 as a function of the filtered estimate Ek (step E8).

[0090] As explained above, the statistical value Tk2 is calculated here by squaring the difference between the filtered estimate Ek and the value q0-

[0091] The comparison module 10 then compares the statistical value Tk2 to the threshold y defined above (step E10) in order to determine the estimated position P (inside or outside) of the electronic device M.

[0092] The process of [Fig.3] may optionally then include a step E12 of allocating resources (supplied by a telecommunications network including the communication system S) to the electronic device M, this allocation being carried out according to the estimated position P.

[0093] In order to clearly illustrate the advantage of using the Kalman filter in the electronic module of [Fig. 2], Figures 4 and 5 show the evolution of the statistical value Tk2 respectively during the use of this electronic module. and when using a similar electronic module but without a Kalman filter.

[0094] Specifically, each of Figures 4 and 5 represents the statistical values ​​Tk2 successively obtained for 1000 measurement times (i.e., k varying from 1 to 1000) while the electronic device M passes through external environments (detected by Tk2 < y) and internal environments (detected by Tk2 > y). In these figures, the threshold y used is that obtained from the formulas given above for a false alarm rate of 0.1%.

[0095] As can be seen from Figures 4 and 5, the presence of the Kalman filter in the electronic module of [Fig.2] significantly improves the robustness of the detection.

[0096] The preceding description is only one possible way of implementing the invention.

[0097] In particular, in order to further improve robustness, it is possible to use an aggregate statistical value obtained by summing n successive Tk2 values ​​and to compare this aggregate statistical value V to a threshold to determine the inside or outside position of the electronic device M. The threshold is in this case based on the chi-square distribution with n degrees of freedom / 2(n).< / q>

Claims

Demands

1. Method for detecting the internal (I) or external (0) position of an electronic device (M) exchanging a signal carried by electromagnetic waves with a remote telecommunication system (S), the method comprising the following steps: - measurement (E2) of a value (Lk) of a quantity characteristic of the exchanged signal; - application (E6) of the measured value (Lk) to the input of a Kalman filter (5) producing at the output a filtered estimate (Ek) of said quantity; - comparison (E10) of a statistical value (Tk2) determined as a function of said filtered estimate (Ek) to a threshold (y) in order to detect the internal (I) or external (0) position of the electronic device (M).

2. A method according to claim 1, wherein the statistical value (Tk2) depends on a likelihood ratio of two statistical hypotheses respectively representative of the internal and external positions of the electronic device (M).

3. A method according to claim 1 or 2, wherein said quantity is a logarithm of a ratio between a useful power of the signal and a power of disturbances affecting this signal.

4. Method according to claim 3, wherein said quantity is a logarithm of a signal-to-interference-to-noise ratio.

5. A method according to any one of claims 1 to 4, wherein said comparison uses a generalized likelihood ratio test.

6. A method according to any one of claims 1 to 5, wherein the threshold (y) is determined as a function of a desired false alarm rate.

7. A method according to any one of claims 1 to 6, comprising a step (E12) in which resources of a telecommunications network comprising the remote telecommunications system (S) are allocated to the electronic device (M) according to the estimated position.

8. Electronic module for detecting the internal (I) or external (O) position of an electronic device (M) exchanging a signal carried by electromagnetic waves with a remote telecommunications system (S), characterized by: - a Kalman filter (5) configured to receive a value (Lk) of a quantity characteristic of the exchanged signal and produce a filtered estimate (Ek) of said quantity; - a comparison unit (10) configured to compare a statistical value (Tk2) determined as a function of said filtered estimate (Ek) to a threshold in order to detect the inside (I) or outside (0) position of the electronic device (M).

9. Electronic module according to claim 8, wherein the statistical value (Tk2) depends on a likelihood ratio of two statistical hypotheses respectively representative of the internal and external positions of the electronic device.

10. Electronic module according to claim 8 or 9, integrated into said electronic device (M).

11. Electronic module according to claim 8 or 9, integrated into said remote telecommunication system (S).

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