Patent Description:
TOA estimations may have a resolution (e.g., expressed in meters) limited by the sampling rate. The higher the sampling rate, the higher the resolution. As the sampling rate cannot be infinite, the maximum resolution is limited.

<CIT> discloses a method for performing a TOA measurement. According thereto, a correlation is first identified by comparing the received correlation profile with different reference correlation functions. On the basis of the comparison, the TOA is corrected by an estimated phase delay.

<CIT> discloses a method for performing a TOA measurement from the inflection edge of a correlation profile.

<CIT> discloses a method for performing a TOA measurement using square-root raised-cosine pulse shaping and chip matched filters on direct sequence spreading waveforms.

<CIT> discloses a method for time of arrival, TOA, measurements, comprising a measurement session in which a TOA is determined on the basis of correlation data.

<CIT> discloses a high resolution ranging method using multicarrier signals.

<CIT> discloses a method for operating a wireless communication network for enabling quality estimation of a measurement that is time-based.

<CIT> discloses a method for improving time of arrival, TOA, measurements in a wireless communication network.

<CIT> discloses a system for improving the accuracy of time of arrival, TOA, measurements in wireless communication networks.

A method for calculating a cross-correlation between the received and sample signal at a time continuous Barker code sequence to determine a measurement associated to the TOA is disclosed by <NPL>.

According to an aspect, there is provided a method for time of arrival, TOA, measurements of transmissions transmitted by a transmitter in a transmission channel, the transmission channel being the environment, comprising a configuration session and a measurement session wherein the configuration session comprises:
performing a plurality of correlation processes for a plurality of configuration signals to obtain multiple configuration correlation functions associated to known different distances at a subsample resolution, the plurality of configuration signals being received in the transmission channel from a transmitter; for each configuration correlation process, determining the peak sample and data of one sample immediately preceding and one sample immediately following the peak sample for each correlation; and determining, from the determined peak sample and the data of the one sample immediately preceding and the one sample immediately following the peak sample, pre-assigned configuration data associated to the transmission channel; and wherein the measurement session comprises: performing, at a sample resolution, a correlation process on a received measurement signal to obtain a measurement correlation function, the subsample resolution being higher than the sample resolution; determining a peak sample and correlation data of one additional sample immediately preceding and one additional sample immediately following the peak sample in the measurement correlation function; determining a TOA and/or distance associated with the TOA on the basis of the peak sample and correction data obtained by at least the correlation data of the additional samples immediately preceding and following the peak sample and pre-assigned configuration data associated to the transmission channel obtained at a subsample resolution.

The correlation data (e.g., correlation values) of the samples immediately preceding and following the peak sample have information regarding the TOA and/or distance which is even more accurate that the information that may be obtained by simply identifying the peak in the correlation function. The correlation data may be adapted to the environment using pre-assigned configuration data. A "subsample" resolution may be obtained, i.e., a resolution (e.g., in terms of distances that may be determined) that goes beyond the maximum resolution possible with the sampling rate of receiver when sampling the received signal.

According to an aspect, the pre-assigned configuration data vary according to the distance.

Accordingly, it is possible to adapt the correction data to the transmission channel. According to the invention, there is provided the configuration session obtaining a plurality of data from the configuration signals received from a plurality of different distances, to obtain pre-assigned configuration data in association to distances or time delays. Accordingly, the pre-assigned data are extremely precise.

According to the invention, the pre-assigned configuration data have a resolution greater than the resolution of the determining step to estimate the TOA and/or distance.

Accordingly, precision is further increased. Notably, as the correlation data on the samples close to the peak sample provide information at a subsample resolution, the pre-assigned configuration data may also have a subsample resolution, which permits to increase the accuracy of the distance data obtained by the correlation data of the samples close to the peak sample.

Accordingly, precise configuration data are obtained from the configuration session, the configuration data being at a subsample resolution.

According to an aspect, a configuration session has a simulation session, e.g., in which the received signals are simulated over a simulated channel simulating the features of the transmission channel.

According to an aspect, there is provided (in the configuration session and in the operation session) comparing and/or measuring the difference between the correlation value of a sample immediately preceding the peak sample with the correlation value of a sample immediately following the peak sample, and/or comparing or calculating a ratio between:- the difference between the correlation value of a sample immediately preceding the peak sample immediately and the correlation value of a sample following the peak sample; and.

The quotient: <MAT> provides accurate information on the real distance and/or TOA of the received signal. This quotient may be calculated, in the measurement session, in the step of determining the TOA and/or the distance. This quotient may additionally or alternatively calculated in the configuration session, to obtain accurate information on the transmission channel.

According to an aspect, there is provided a method for performing difference time of arrival measurements, TDOA, comprising measuring a first TOA for a first transmission, a second TOA for a second transmission, and measuring a distance by subtracting the first TOA from the second TOA, wherein at least one of the measurements are performed with a method according to examples above and/or below.

According to an aspect, there is provided a method for performing round trip time, RTT, measurements, comprising transmitting a first signal from a first device to a second device, transmitting a second signal from the second device to the first device, and performing the method one of the examples above and/or below for calculating the distance between the first and the second devices for at least the first and/or the second signals.

According to an aspect, the first and the second devices are user equipment, UEs, the method further comprising performing RTT measurements according to a device to device, D2D, or vehicle to vehicle, V2V, protocol to obtain the mutual distance between the two UEs, wherein at least one UE performs the steps of performing in the measurement session and determining the peak sample and the correlation data in the measurement session.

According to an aspect, there is provided a device comprising:.

According to an aspect, the device performs one of the methods discussed above and/or below.

According to an aspect, there is provided a storage device containing pre-assigned configuration data to be combined to the correlation data of the samples immediately preceding and following the sample with the peak to adapt a measurement to the transmission channel.

According to an aspect, there is provided a system comprising a transmitter and a receiver (e.g., one of the devices above and/or below) and is to measure a TOA of a signal received from the transmitter at least in the determining step or in the configuration session.

Accordingly, the examples above and below have low complexity (e.g., in terms of resource utilization, such as the number of additions, multiplications, and so on, which are to be processed) with respect to methods according to the prior art.

Further, no correlation data are distorted, hence accuracy is increased.

In some examples, the sampling rate of the signals transmitted/received in the configuration session is the same of the sampling rate of the signals transmitted/received in the measurement (operation) session. Notwithstanding, information may be obtained at a subsample resolution by performing a great number of configuration measurements in the configuration session.

According to an example, it is possible to perform real configuration measurements in the configuration session using a hardware chain for the transceiver. Cables of different length may be used for this configuration session to get a correlation profile at each length. The cable may directly connect the transmitter to the receiver output. The exact signal propagation time for each cable may be controlled with a measurement instrument set at the defined carrier frequency. The transmitter and the receiver may be synchronized. The number of cables used may be related to the number of subsamples (K). Accordingly, pre-assigned configuration data may be calculated for each measurement with a different cable length. Knowing the exact signal propagation time for each cable.

In some examples, there is provided when determining the correlation data of the sample immediately preceding and the sample immediately following the peak sample, comparing and/or measuring the difference between the correlation value of a sample preceding the peak sample with the correlation value of a sample following the peak sample with the correlation value of the sample immediately following the peak sample and/or
calculating ratio between:.

In some examples, there is provided, in the configuration session performed at a subsample resolution comparing and/or measuring the difference between the correlation value of the sample immediately preceding the peak sample with the correlation value of the sample immediately following the peak sample, and/or
calculating a ratio between calculating a ratio between:.

In some examples, there is provided obtaining the pre-assigned configuration data from a fitting function.

In some examples, there is provided obtaining the pre-assigned configuration data from a linear function.

In some examples, there is provided configuration data using a quadratic function.

In some examples, there is provided collecting the pre-assigned configuration data from a plurality of TOAs and/or distances at mutual distances smaller than the measurement resolution associated to the sampling rate, to adapt to the transmission channel to the correlation data associated to the samples immediately preceding and following the peak sample.

In some examples, there is provided adapting data obtained by the samples immediately preceding and/or following the peak sample with data associated to the transmission channel obtained at a subsampling resolution.

In some examples, there is provided the linear or quadratic function transforms data from a measurement correlation function into data which keep into account the features of the environment.

In some examples, the configuration data comprise a slope of a linear function.

In some examples, there is provided obtaining a quotient associated to a sample immediately preceding the peak sample and the sample immediately following the peak sample in the correlation function, and adapting the quotient to the channel conditions.

In some examples, there is provided scaling a quotient associated to the sample immediately preceding the peak sample and the sample immediately following the peak sample in the correlation function by a preassigned configuration data "a".

In some examples, there is provided obtaining a value a quotient corrlndex associated to the sample immediately preceding the peak sample and the sample immediately following the peak sample in the correlation function obtaining the correction data on the basis of <MAT> where "a" and "b" are pre-assigned configuration data.

In some examples, "a" and "b" are coefficients obtained from a fitting function obtained in the configuration session.

In some examples, there is provided determining a TOA by <MAT> where estimated_TOA is the estimated TOA, Correction is the correction data, and K is a constant associated to the number of subsamples of the configuration session.

In some examples, there is provided, in the configuration session, performing configuration session correlations associated to different subsamples "k", and, for each configuration session obtaining a quotient corrIndex(k) associated to the at least one sample immediately preceding the peak sample and the at least one sample immediately following the peak sample; and
projecting different corrlndex(k) to obtain a fitting function which approximates the different data obtained in the configuration session.

In some examples, there is provided obtaining pre-assigned configuration data as coefficients "a" and "b" from the fitting function.

In some examples, the subsample resolution is so that the pre-assigned configuration data are obtained at different positions which are within the sample resolution.

In some examples, the received measurement signal is a signal transmitted in an long term evolution, LTE, network or a <NUM> or <NUM> network.

In some examples, the received measurement signal is a signal received from a satellite and/or a Galileo system.

In some examples, the steps of performing and determining a peak sample and correlation data of additional samples immediately preceding and following the peak sample in the measurement correlation function are performed by a first device, and
the steps of determining a TOA and/or distance is performed by a remote device.

In some examples, the first device is a user equipment, UE, and the second device is a location server, or a base station, or an evolved node, eNB, or a gNB (next Generation NodeB in <NUM>). In some examples, there is provided measuring TDOAs obtained by transmissions received from a plurality of base stations.

In some examples, there is provided using a full-duplex communication device, the method comprising, before the step of performing:
transmitting and receiving the transmitted signal in a full-duplex operation; and, after the step of determining a TOA, obtaining the delays associated to internal components of the full-duplex communication device.

In some examples, there is provided compensating the internal delays of the full-duplex communication device.

In some examples, there is provided a device configured to obtain the peak sample and data associated to the samples immediately preceding and following the peak sample from a remote device.

In some examples, there is provided a full-duplex device configured to obtain delays associated to its internal components by transmitting and simultaneously receiving the same signal.

In some examples, there is provided a system comprising a transmitter and a receiver, wherein the receiver is to measure a TOA of a signal received from the transmitter at least in the determining step or in the configuration session.

In some examples, there is provided a device comprising non-transitory storage means which contain processor readable instructions which, when performed by a processor, cause the processor to perform any of the methods below or above.

According to an aspect, there is provided a method for configuring a device comprising:.

associating configuration data to the transmission channel.

According to an aspect, there is provided a device for defining configuration data from a received configuration signal, further comprising:.

According to an aspect, there is provided a device as above and/or below, wherein the device is calibrated by:.

According to an aspect, there is provided a method for configuring a device, the method comprising:.

In this document, transmissions and/or signals may be, for example, radio-frequency and/or ultrasound transmission and/or signals.

The transmitter and/or the receiver may be, for example, movable and/or may be engaged to moving means. The transmitter and/or the receiver may be, for example, engaged to a satellite.

<FIG> shows a method <NUM>. The method <NUM> is used to perform measurements using a TOA technique. The method <NUM> uses configuration data which have been obtained in a preceding method, i.e. in a configuration (offline) session <NUM> (shown in <FIG>). Reference numeral <NUM> in <FIG> refers to a sequence of methods <NUM> and <NUM>. The method <NUM> is performed (even days or years) before the start of method <NUM>.

The method <NUM> comprises an operation session during which TOA measurements are performed. The method <NUM> uses pre-assigned configuration data. The configuration data are data obtained using a configuration session such as a session defined by the method <NUM>.

The method <NUM> is performed on a measurement signal which has (when received) a sampling rate (measurement sampling rate). For example, a transmission received from a transmitter is sampled at the sampling rate. The sampling rate is such that a measurement received signal is processed as a succession of discrete samples (each sample associated to a particular time instant). Therefore, a received signal may be represented as a succession of samples (e.g., <NUM>, <NUM>, <NUM>,. , i-<NUM>, i, i+<NUM>,. , l), each of which is associated to a value (which may be connected, for example, to electromagnetic or ultrasound magnitudes), which has been received by the receiver by sampling (the received signal may be physically obtained by an antenna). The received signals are processed, e.g., using a digital signal processor (DSP) or another computing device, to obtain data which permit to obtain a measurement of the TOA (time delay of a transmission), which is connected to the environment (transmission channel).

The sampling time is associated to a resolution. In fact, the time delays and the distances that that may be recognized are discrete in number.

At step <NUM>, a correlation process (cross-correlation) is performed on a received measurement signal. A correlation function (measurement correlation function) is derived. A peak sample is determined in the measurement correlation function to permit an estimation of a TOA and/or a distance associated to the received signal.

An example of correlation (cross-correlation) is provided by the formula <MAT> where "l" is the reference code length in samples and "i" is a value which indicates how far y shall be shifted so that y and x correspond. x* is the complex conjugate of x. Here, the sign R(i) may be used instead of Rxy[i] for simplicity. When the maximum or a peak of the correlation profile is named, reference may be made to the peak of the absolute value (e.g., only a positive value). The correlation function quantifies how y[i+k] and x[k] match and is associated to a probability of the two functions being in phase. In general terms, the correlation may have a sampling rate which may be the same of (or may be associated to) the received measurement signal. A synchronization of the signals may be a prerequisite to perform the correlation.

Notably, the resolution achievable by the correlation processes is bounded to the distance between adjacent samples. If, for example, the distance between sample i-<NUM> (at instant t<NUM>) and i (at instant t<NUM>) is <NUM> ns, information is provided for instants t<NUM> and t<NUM>, but the correlation does not give the same accurate information on different instants (such as, for example, t<NUM><t< t<NUM>).

At step <NUM>, a peak sample is retrieved in the correlation function. The peak sample directly associates the measurement received signal to a distance (e.g., between the antenna of the transmitter and the antenna of the receiver). In particular, it is possible to estimate a TOA by determining the peak sample, which is the sample (in the succession of samples of the correlation profile) which has the maximum value (e.g., the maximum absolute value). The information provided by the correlation (and the estimated TOAs and distances, as well) has a maximum resolution, bounded to the sampling rate of the received measurement signal. The fact that the resolution is limited (maximum achievable resolution) causes a granularity of distances. In general terms:.

For example, when a receiver estimates the distance of a transmitter which moves towards the receiver, at a first instant the peak value in the correlation profile may be retrieved at an ith sample (associated to a particular TOA and/or a particular distance), while at a second instant the peak value may be retrieved at an (i+<NUM>)th sample (associated to another TOA and another distance), but the determination of the peak values, as such, does not give information on the signal time of flight (TOF) at an instant intermediate between the ith sample and the (i+<NUM>)th sample (and, therefore, does not give information on the distance of receiver form the transmitter). Therefore, a peak sample determination, as such, estimates a TOF whose resolution is limited by the sampling rate (coarse estimation). Therefore, at least at step <NUM>, additional data, other than the position of the
peak in the correlation profile, are collected from the correlation profile to correct the estimation that are computed using the peak sample determination.

At step <NUM>, correlation data of one additional sample preceding and of one additional sample following the peak sample in the measurement correlation function is determined. It is determined the sample immediately preceding the peak sample and the sample immediately following the peak sample. The immediately preceding or following sample is the sample which precedes or follows the peak sample of just one sample in the measurement received function (adjacent samples). For example, if a received function is received as a succession of <NUM>, <NUM>,. , i-<NUM>, i, i+<NUM>,. , l, samples, and the peak sample is the ith sample of the succession, the immediately preceding sample is the (i-<NUM>)th sample, while the immediately following sample is the (i+<NUM>)th sample. If the samples of the received function are acquired every <NUM> ns, the time delay from the immediately preceding/following samples and the peak sample is, therefore, <NUM> ns. The correlation values and/or data are also obtained in step <NUM>. For example, the correlation value of the peak and the correlation values of at least one of the samples i-<NUM>, i-<NUM>, i, i+<NUM>, i+<NUM> are collected.

At step <NUM>, values associated to the correlation values of the samples immediately preceding and following the peak sample are retrieved. A value (or modified versions thereof, such as a normalized value) of the correlation function at the additional sample immediately preceding and the additional sample immediately following the peak sample is retrieved. A difference between a correlation value of a sample immediately preceding the peak value and a correlation value of a sample immediately following the peak value may be obtained. The difference may be an algebraic difference, so as the sign ("+" or "-") may be taken in account. A sum of a correlation value of a sample preceding the peak value and a correlation value of a sample immediately following the peak value may be performed. A quotient (e.g., of a difference between the correlation value of a sample preceding the peak value and a correlation value of a sample immediately following the peak value at the numerator, divided by a sum of a correlation value of a sample preceding the peak value and a correlation value of a sample following the peak value at the denominator) may be calculated. For example, if a correlation value is R(i) at the peak sample i, the quotient (which may be named corrlndex in the present document) may be: <MAT>.

Hence, at step <NUM>, besides the determination of a peak sample which gives a first information on the TOA, data associated to other samples (e.g., data associated to correlation values of the samples adjacent to the peak sample) are obtained.

At step <NUM>, a TOA and/or a distance are calculated on the basis of the peak sample and correction data derived by the additional samples. A coarse estimation of the TOA or distance is performed from the peak sample in the correlation profile (e.g., the sample with the maximum absolute value). This estimation is corrected using a correction data derived at least by the correlation data of additional samples immediately preceding and following the peak sample. For example, the quotient discussed above (corrIndex) may be used to correct the estimation obtained from the peak sample.

The correlation values close to the maximum of the correlation function (i.e., the values of the correlation profile measured at the samples which are adjacent to the peak sample) carry additional information on the signal TOF (which provides information on the distance of the transmitter). By using the values of the correlation function at the samples which are close to the maximum value, the determination of the TOA or distance values is more accurate (at least, it reaches an accuracy level which is similar to an accuracy level that would be achieved with an increased sampling rate). Reference can be made, for example, to the above-discussed quotient (the ith sample being the peak sample): <MAT>.

Here, the correlation value R(i-<NUM>) at the sample immediately preceding the peak sample i is compared to the correlation value R(i+<NUM>) at the sample immediately following the peak sample i. If R(i-<NUM>) > R(i+<NUM>), it is possible to derive additional information on the position of the transmitter. For example, it is possible to derive the probability of the transmitter being actually closer to the receiver than estimated by simply retrieving the peak sample. R(i-<NUM>) > R(i+<NUM>) gives the idea that, with a better resolution (higher sampling rate), the peak value would not be retrieved at the time instant associated to the ith sample, but in a sample associated to a preceding time instant. Analogously, if R(i-<NUM>) < R(i+<NUM>), there is a high probability for the real distance to be greater than estimated when simply retrieving the peak sample. R(i-<NUM>) < R(i+<NUM>) gives the idea that, with a better resolution (higher sampling rate), the peak value would be identified after the time instant associated to the ith sample.

Therefore, data obtained by the correlation data of additional samples preceding and following the peak sample permit to derive correction data for a TOA measurement.

At step <NUM>, the estimated TOA or distance are corrected using the correction data. For example, a transformation (such as, for example, a linear combination) is performed to transform the estimated TOA into a corrected measurement through a composition with a value associated to a correction data (e.g., a transformed value).

At step <NUM>, correction data adapted (e.g., calibrated) to the transmission channel are obtained using pre-assigned configuration data. The pre-assigned configuration data have been defined in a configuration session (e.g., using method <NUM>). The pre-assigned configuration data give information about the environment. The pre-assigned configuration data permit to increase the accuracy of the TOA measurement, so that the correction data obtained by the correlation data of additional samples immediately preceding and following the peak sample are processed to be adapted to the specific environmental conditions of the transmit channel. The pre-assigned configuration data may be in the form of functions (e.g., linear functions) which may transform a first correction data into a second correction data which keeps in account the situation of the place onto which TOA measurements are carried out. The pre-assigned configuration data may comprise a function obtained by inference or interpolation from data signals obtained in a configuration session data (e.g., with method <NUM>). Fitting functions, (e.g., linear fitting function, quadratic fitting functions, or others) may be used.

Each correction data may be associated to a particular TOA value, range, distance range, or TOA range, e.g., after having adapted the data from the correlation function (e.g., peak sample, value on the samples close to the peak sample). As the determination of distances and TOAs as by retrieving the peak value permits to obtain, at best, discrete estimations, each discrete TOA value (or distance) which may be estimated may be pre-assigned (e.g., in a configuration session) to at least one configuration data.

By using correction data based on the data (e.g., value) of the additional samples immediately preceding and following the peak sample in combination to the pre-assigned configuration data, the measurement resolution of time delays and distances is increased beyond the maximum resolution bounded to the sampling rate. It is therefore possible to conclude that the present examples reach a subsample resolution (subsample accuracy).

<FIG> shows a method <NUM> (which performs a configuration session) used to obtain configuration data (plurality of configuration data) from configuration signals received from a plurality of different locations (from a transmitter which moves through different locations, so that the locations are known, or the distance from the location is known). The configuration data comprise, for example, data obtained from TOA data achieved by performing correlations on the received configuration signals. The configuration data provide information on the transmission channel. The configuration data are used, in the subsequent operation session(s), to better estimate the TOA or distance.

<FIG> shows a device <NUM>. The device <NUM> is a device for measuring a TOA and/or a distance. The device <NUM> performs the method <NUM>. The device <NUM> is configured by using the method <NUM>. The device <NUM> is part of a receiver device which receives transmissions sent by a transmitter whose distance is to be calculated.

In operation, a received measurement signal <NUM> (sampled at a particular sampling rate) is provided to a correlation unit <NUM>. The received measurement signal <NUM> is correlated (cross-correlated) with a reference signal <NUM> (which may be stored in a memory) to obtain a measurement correlation function <NUM>. The measurement correlation function <NUM> is provided as an absolute value (e.g., with only positive numeric values), as a normalized value (e.g., by dividing values by a particular value), or similar. By correlating a received function with a pre-stored function, a maximum is determined in the correlation profile, the sample having the maximum value being related to the TOA of the received measurement signal (and to the distance of the transmitter).

The measurement correlation function <NUM> is provided to a sample determination unit <NUM>. The sample determination unit <NUM> determines the peak sample <NUM> of the measurement correlation function <NUM>. The peak sample is the sample which has
the maximum value (e.g., between the absolute values and/or normalized values) of the correlation function. The sample determination unit <NUM> recognizes other samples, such as a sample immediately preceding the peak sample <NUM> and a sample immediately following the peak sample <NUM>. The peak sample <NUM> is input to a TOA or distance estimation unit <NUM>, which estimates a TOA (and/or a distance associated to the TOA) <NUM>. The TOA may be coarsely estimated on the basis of the position of the peak in the correlation function (the position of the peak being associated to a particular TOA, the TOA being associated to a particular distance).

In general terms, the estimation performed by the estimation unit <NUM> has a limited resolution: in a radio-frequency (RF) signal, for example, the maximum distance resolution of some meters may be achievable, e.g., when the sampling time is in the tens of nanoseconds (approximately, electromagnetic waves travel at the speed of three meters in ten nanoseconds).

A correction data determination unit <NUM> may be provided. The correction data determination unit <NUM> makes use of the correlation data (e.g., value) <NUM> of the sample(s) immediately before and after the peak sample <NUM> in the measurement correlation function <NUM> and/or the estimated TOA or distance <NUM>. From the data of the close samples information of the position of a transmitter is derived which is even more accurate than the information inferred by the position of the peak sample.

The correction data determination unit <NUM> may be input with data associated to the measurement correlation function <NUM> (e.g., peak sample <NUM> and/or correlation data <NUM> associated to the samples immediately close to the peak sample <NUM>, the estimated TOA or distance <NUM>).

The correction data determination unit <NUM> is input with pre-assigned configuration data <NUM> (obtained with method <NUM>). The configuration data <NUM> may be stored, for example, in a memory and be at disposal of the correction data determination unit <NUM>. The configuration data <NUM> may comprise look-up tables and/or functions (e.g., fitting functions). The configuration data <NUM> may contain information on the environment (transmission channel), as they may have been obtained from actual measurements (e.g., in the configuration session and/or with method <NUM>). The actual measurements have been obtained at a subsample resolution with respect to the maximum resolution of the measurement (e.g., the resolution associated to the sampling rate). The configuration data
<NUM> permit to perform transformations so that sample information associated to the peaks <NUM> and correlation data <NUM> associated to the samples close to the peaks is transformed into correction data which take into account the conditions of the transmission channel. Therefore, there is accurate data (e.g., at the subsample accuracy) at disposal of the correction data determination unit <NUM> for modifying the estimated TOA (or distance) <NUM>.

By using the configuration data <NUM>, the correlation data (e.g., correlation values) <NUM> of the samples immediately before and after the peak sample <NUM> are transformed to adapt the estimated TOA (or distance) <NUM> to high resolution corrected TOA or distance values <NUM>. A correction unit <NUM> is used to modify the estimated TOA or distances with the correction data. Notably, not only is the TOA (or distance) <NUM> corrected, but it also keep into account the conditions of the transmission channel.

For example, in the correction unit <NUM>, there is the possibility of correcting the TOA or distance <NUM> by composition with (e.g., addition of) a value <NUM> associated to the correction data, the value <NUM> being in the subsample resolution.

<FIG> shows a device <NUM> which may be a TOA or distance calculation system <NUM>. The device <NUM> may comprise an antenna <NUM>. The device <NUM> may comprise a receiving transceiver <NUM>, which may be connected to the antenna <NUM>. The device <NUM> may comprise the device <NUM>. The device <NUM> may comprise a filter <NUM>. The device <NUM> may also comprise a I/O unit <NUM>, which may provide as an output to a user or to an external device a calculation of the TOA (or a distance), e.g., the value <NUM>.

<FIG> shows a transmitter device <NUM> whose distance D<NUM> at instant t<NUM> is to be determined by the device <NUM> or <NUM>. The transmitter device <NUM> may be moved to have a distance D<NUM> from the device <NUM> or <NUM> at instant t<NUM>. Reference numeral <NUM> refers to a system which comprises the transmitter <NUM> and a receiver <NUM> or <NUM> for calculating the distance (e.g., in real time). Transmitter device <NUM> may be, for example, a Galileo system or satellite.

In general terms, TOA measurements based on retrieving the sample peak in the correlation function are limited in the accuracy by virtue of the maximum sampling time (which has a finite value). If, in an RF environment, the sampling time is <NUM> ns, the maximum accuracy of a TOA measurement based only on retrieving the peak sample may have a resolution of approximately <NUM>. Therefore, by sampling at <NUM> ns, only
distances which are approximately multiple of <NUM> would be detectable without approximation.

In some examples, <FIG> may concern a simulated receiver, a simulated transmitter, and a simulated channel.

A comparative example is provided by <FIG> and <FIG>. In <FIG>, an ideal profile <NUM> for a correlation on a signal received from a distance of <NUM> is aligned with the reference signal (<NUM>°) and provides a correct peak. However, with <NUM>° phase difference as shown in <FIG> (which refer to an estimation without correction, e.g., by simply retrieving the maximum in the correlation profile), a detected maximum <NUM> deviates from the ideal maximum <NUM> with a Δd which is <NUM> in this case. In <FIG> and <FIG>, the abscissa is provided in meters (as a consequence of the distance being associated to the peak position in the correlation sample). A correlation filter that computes the correlation may be used.

In systems which do not have correction data, only when a transmitter (e.g., <NUM>) transmits a signal from a position at a distance which is a multiple of the distance travelled by the waves, the TOA measurement may be, at best, correct. When the transmitter transmits from a different position, a certain amount of error may be present.

Notwithstanding, the deviation of the TOA measurements is corrected, by implementing the method <NUM> and/or using the device <NUM> or <NUM>. <FIG> shows a first correlation profile (function) <NUM> (which may represent a measurement correlation function <NUM>) of a first received signal received in a measurement session from a distance which is exactly detectable by retrieving the peak sample when correlating a received function (i.e., the transmitter is placed at a distance which is multiple to approximately <NUM> for a <NUM> ns sample time). A peak <NUM> is identified (e.g., by the sample determination unit <NUM> or step <NUM>). Accordingly, the peak sample is identified (in <FIG> the peak sample is in the <NUM>th sample), and the TOA and/or distance is coarsely estimated (e.g., by unit <NUM>). Two other samples, associated to the correlation values <NUM>', are identified as the samples immediately before and after the sample with the peak <NUM>.

<FIG> also shows a second correlation profile (function) <NUM> of a second received signal received in the same measurement session, but after that the transmitter has moved of half meter (e.g., the distance is now approximately <NUM>). By performing the second correlation (e.g., by repeating step <NUM> for a new signal), a second peak is retrieved. In this case, the peak of the second correlation profile <NUM> is at the position of the peak of the first correlation <NUM>. This is due to the fact that the first and second received signals are received from distances which are too close to each other to be distinguished at the resolution of the present sampling rate. However, the positions of the samples immediately before and after the peak sample in the second correlation profile <NUM> are different from the samples <NUM>' of the first correlation profile <NUM>. Therefore, even if, from the position of the peaks <NUM> the distance of the transmitter would not be measured with a great precision, it is notwithstanding possible to use samples close to the peak sample (samples <NUM>") to reconstruct a more exact location of the transmitter at a subsample resolution. Using the correction data <NUM> obtained by the data carried by the samples <NUM>" (e.g., values <NUM>), the results of the estimation are corrected.

However, it has been noted that even using the values of the samples preceding and following the peak sample, it is still possible to increase accuracy, by using the pre-assigned configuration data <NUM>. As the pre-assigned configuration data have been collected from a plurality of TOAs and/or distances which have distances smaller than the measurement resolution associated to the sampling rate, the pre-assigned configuration data are suitable for adapting to the transmission channel (e.g., calibrating) the correlation data associated to the samples preceding and following the peak sample.

For samples <NUM>", the correlation value R(i-<NUM>) (which is the <NUM>th sample) is higher than the correlation value R(i+<NUM>) (which is the <NUM>th sample). It is therefore possible to infer that, with an increased resolution (e.g., with a much better higher sampling rate), the "real peak" would be retrieved before the instant associated to the peak sample. Therefore, the above-identified quotient corrlndex <MAT> provides a more accurate information on the position of the transmitter with respect to the estimation based on simply retrieving the peak value in the correlation function.

However, by adapting data obtained from the samples close to the peak sample (e.g., from the quotient corrIndex) using pre-assigned data at a higher resolution (subsampling.

However, by adapting data obtained from the samples close to the peak sample (e.g., from the quotient corrlndex) using pre-assigned data at a higher resolution (subsampling resolution), the accuracy of the corrected TOA and/or distances <NUM> is further increased.

The correction data to be used for measuring the distance (or TOA) are obtained by adapting the data obtained by the samples immediately preceding and following the peak sample with data associated to the transmission channel, these data having being obtained at a subsampling resolution (the subsampling resolution being higher than the sampling resolution of the measurements performed by the sample determination unit <NUM>, for example). An example of pre-assigned configuration data <NUM> (obtained with method <NUM>) is provided in <FIG>. The pre-assigned configuration data <NUM> (e.g., correction index) may take the form of a linear function <NUM>. The linear function <NUM> may have been obtained, for example, by inference, interpolation, least square method, or other statistical methods. The linear function <NUM> may be used to transform data from a measurement correlation function (e.g., data associated to the peak preceding and/or following the peak sample) into data which keep into account the features of the environment (transmission channel). Different environments, therefore, may be associated to different linear functions (e.g., different slopes).

In <FIG>, a quadratic function is shown. The quadratic function may be expressed, for example as y=ax<NUM>+bx+c. In one case, for example, it may be: <MAT>.

<FIG> shows a method <NUM> which may be performed as an embodiment of method <NUM> and/or by the device <NUM> or <NUM>.

At step <NUM> (embodying step <NUM>), a correlation R is computed, e.g., by obtaining the measurement correlation function <NUM>. The correlation R has a sample resolution (resolution associated to the sampling rate of the received signal and/or the sampling rate of the correlation function).

At step <NUM>, an initial coarse TOA (e.g., TOA <NUM>) or a coarse distance is identified (e.g., through units <NUM> and <NUM>).

At step <NUM>, calculations associated to the correlation function <NUM> (e.g., to the correlation data of at least one additional sample preceding and/or following the peak sample <NUM>") are performed (e.g., at the correction data determination unit <NUM>). For example, it is possible to calculate values such as: <MAT> <MAT> <MAT>.

Hence, the value corrlndex may embody the quotient discussed above and may give an idea of the "real position" of the peak. Notably, if the real distance (or TOA) is greater than the distance estimated by retrieving the peak sample in the correlation profile, then the value diff_R = R(i + <NUM>) - R(i - <NUM>) is greater than zero.

At step <NUM> (which may be performed by the correction data determination unit <NUM> and/or in step <NUM>), the correction data <NUM> are calculated, e.g., by adapting the corrlndex to the environment conditions. For example, the correction may be performed using a linear transformation which may translate corrlndex by a pre-assigned configuration data "b" and scale by a pre-assigned configuration data "a" according a formula such as: <MAT>.

The term "b" may be related to the number of correlations, for example. This term "b" may be used to adjust, in some cases, for slight deviations when linear fitting is performed (e.g., when a linear equation may approximately fit corrlndex but error margin is acceptable). It is also possible to choose a higher degree fitting function (e.g., a quadratic fitting function).

The quotient corrlndex, calculated on the basis of the correlation values of the samples close to the peak sample, may therefore be scaled by a quantity "a". Basically, "a" and "b" may be the coefficients of a linear transformation which keeps in account the conditions of the transmission channel. Other ways of adapting the correction data to the particular transmission channel may be defined (e.g., using a quadratic transformation, and so on). Data such as, "a" and "b", which are pre-assigned, may have been obtained in a configuration method (e.g., method <NUM>). Basically, data "a" and "b" provide a modeled profile which permit to correct the imprecise TOA estimated by simply searching for the peak sample in the correlation profile.

At step <NUM> (which are embodied by correction unit <NUM> and/or performed in step <NUM>), the correction data may be composed (e.g., algebraically summed) to the initial TOA or distance estimated at step <NUM> (e.g., by unit <NUM>).

Therefore, the final TOA may be a linear combination between an estimated TOA and a correction value, for example: <MAT>.

K may be a fixed number. K may be associated to the number of subsamples of the configuration session, for example (i.e., the number of configuration signals, received by different distances in the configuration, for which the correlations have been performed).

The pre-assigned configuration data <NUM> may be the same for all the TOAs (or distances). As can be seen from <FIG>, for example, the data a, b may be constant, as they are coefficients of a linear function. Also the parameter K (number of subsamples) may in general be fixed.

Examples of a configuration session are here discussed. In some examples, it is possible to use a transmitter such as the transmitter device <NUM>, which, as shown in <FIG>, may move between different positions in different time instants. For example, the transmitter may move from a distance D<NUM> to a distance D<NUM> between time instants t<NUM> and t<NUM>. The transmitter and/or the receiver may have units (e.g., GPS unit, clock unit, storage device, calculation unit etc.) which permit to keep into account data associated to the position (e.g., coordinate data, geographical data, and so on) or the receiver is capable of taking the relative distances into account without the need for a synchronization scheme. The transmitter and/or the receiver may be engaged to a moving device, which may transport it along different positions (e.g., geographical locations). The transmitter and/or the receiver may be engaged to a satellite, for example.

<FIG> shows a receiver <NUM> which may be, for example, the device <NUM> and/or <NUM>. The receiver <NUM> defines the configuration data <NUM>. <FIG> shows the scheme of the device <NUM>, with units which may be the same of the units of <FIG> (the same units may be retrieved by substituting "<NUM>" with "<NUM>" in the first digit of the reference numerals). A received configuration signal <NUM> may be input to a correlation unit <NUM>. The received
configuration signal <NUM> is correlated with a reference signal <NUM> (which may be stored in a memory) to obtain a configuration correlation function <NUM>. The measurement correlation function <NUM> is provided to a sample determination unit <NUM>. The sample determination unit <NUM> determines the peak sample <NUM> of the measurement correlation function <NUM>. The sample determination unit <NUM> also determines data (correlation values) from other samples, i.e., a sample preceding the peak sample <NUM> and a sample immediately following the peak sample <NUM>. The peak sample <NUM> and the other samples are provided to a configuration data definition unit <NUM> to provide (and/or save in a memory) configuration data which, in operation, will provide the pre-assigned configuration data <NUM>. An example of the configuration data <NUM> defined by the configuration data definition unit <NUM> may be, for example the coefficients "a" and "b" discussed above.

During the configuration session (method <NUM>), the distance separating the transmitter (e.g., <NUM>) and the receiver may be changed (the receiver and/or the transmitter may change the position). Therefore, the receiver <NUM> may receive a configuration signal from each of a plurality of distances. The configuration signal may be a continuous or burst electromagnetic or ultrasound transmission, which may notwithstanding be taken at different distances separating the transmitter and receiver during different time instants. Therefore, the receiver <NUM> obtains data from a plurality of received configuration signals, each of which is processed (e.g., using different correlations). In some examples, it is possible to use a single correlator, where measurements are carried at different time instants. The receiver <NUM> may correlate each of the received configuration signals, and for each of them determine the peak sample <NUM> and correlation data (such as correlation values) associated to the at least one additional sample <NUM> preceding and/or following the peak sample <NUM>. At least some of these operations may be performed not in real time (e.g., after having received and stored all the signals received by the transmitter), such as offline.

In the configuration session, the transmitter or receiver may spatially move while sending a configuration transmission, so that the receiver receives in different time instants signals at different distances.

In some examples, the configuration session may be performed on a simulation level. The distance displacement at the simulation may be performed for example with a simulated channel and software transceiver modules.

When performing real configuration measurements in the configuration session, a hardware chain for the transceiver may be used. Reference may be made to <FIG>, where a cable is not shown but may be provided between the devices <NUM> and <NUM>/<NUM>. Cables of different length may be used for this configuration session to get a correlation profile at each length. <FIG> shows measurements performed for different cable lengths (<NUM>: <NUM>; <NUM>: <NUM>; <NUM>: <NUM>). The cable may directly connect the transmitter to the receiver output. The exact signal propagation time for each cable may be controlled with a measurement instrument set at the defined carrier frequency (for example a network analyser). The transmitter (<NUM> in <FIG>) and receiver (e.g., <NUM>, <NUM>, <NUM>) should be synchronized in this step otherwise it will not be possible to measure the relative propagation time at different instants due to the frequency offsets. The number of cables used may be related to the number of subsamples (K). Following the steps in <NUM> the value of corrlndex may be calculated for each measurement with a different cable length. Knowing the exact signal propagation time for each cable, the profile in <FIG> may be then obtained with real data. The number of corrIndex(k) values is equal to the number of measurements taken within one sample (i.e. the relative propagation time from the cable length is in subsamples).

With respect to the measurement session (method <NUM>), the configuration session has a resolution which is greater (subsample resolution). If, for example, the sampling rate to be used at the measurement session is <NUM> ns (associated to a maximum resolution of approximately <NUM>), the configuration session may be so that the receiver collects configuration signals when the transmitter has travelled a distance less than <NUM> (e.g., every <NUM>, to obtain a configuration resolution <NUM> times greater than that achievable with the simple detection of the peak value in the correlation). Hence, in the configuration session, the received configuration signals are received from a succession of distances which with a resolution better than the resolution of a TOA measurement when only based on retrieving the peak sample. Therefore, information at subsample resolution is obtained which is used to adapt, in the measurement sessions, the data obtained from the correlation values of the samples close to the peak sample to the environment.

Reference may be made to <FIG>. The receiver <NUM> may receive two different signals which provide different correlation profiles <NUM> and <NUM> which may have been transmitted by the transmitter from different positions (e.g., from distances of half meter). The distance between the different positions (e.g., the half meter) is within the maximum resolution (notably, the correlation profiles <NUM> and <NUM> have the same maximum <NUM>). However, information from correlation data (e.g., <NUM>) of additional samples immediately preceding and following the peak sample (e.g., data R(i-<NUM>) and R(i+<NUM>) ) is obtained. These data may permit to calculate the configuration data <NUM> (e.g., the coefficients "a" and "b") which will be used in the measurement session.

Other than in the measurement session, in the configuration session the position of the transmitter is in general known for each signal that is received by the receiver: the transmitter may have the knowledge of the position, e.g., an absolute position and may store or transmit data relating to the position, so as to permit to associate a particular configuration signal, as received by the receiver, to the transmitter's position. Even if the absolute position is not known, the relative distance between different measurements is sufficient. For this step a number of measurements related to subsamples may be taken. Even if the absolute TOA is not known, the configuration data can be extracted from the correlation profiles taken at several instants within one sample. Hence, in the configuration session, it is possible to associate the distance of the receiver from the transmitter with values (<NUM>") of the correlation data (e.g., R(i-<NUM>) and/or R(i+<NUM>)) of at additional samples (i-<NUM> and i+<NUM>) immediately preceding and following the peak sample. It is possible to determine, as a feedback, the behaviour of the transmission channel on the basis of the transmitted data. The configuration therefore provides pre-assigned configuration data (calibration data) which will be used, in the operation session, to adapt the correction data to the environment.

If the configuration signals <NUM> are received from distances which are less than the maximum resolution which is normally achievable with a simple determination of the peak sample, the collected configuration data <NUM> may be considered to be at a subsampling rate, as they have a precision which goes beyond the resolution provided by the sampling rate.

<FIG> shows a method <NUM>' for performing a configuration session (e.g., to implement method <NUM> and/or performed by the device <NUM>).

At step <NUM>, a plurality of correlation processes for a plurality of configuration signals are performed to obtain multiple configuration correlation functions at different distances (e.g., associated to different subsamples). The distance between the signals is at a subsample resolution with respect to the sample resolution of the measurement method <NUM>, for example (e.g., the time distance between two consecutive samples of the measurement received signal <NUM> is associated to a distance which is greater than the distances for which the correlations are calculated in the configuration session). The configuration signals from which the calculations are made may be either obtained through actual measurements or simulated.

At step <NUM>, for each configuration correlation process performed at step <NUM>, the peak sample and data samples immediately preceding and following the peak sample for each configuration are determined.

At step <NUM>, configuration data (data <NUM>) are associated to the transmission channel. The configuration data have a subsample resolution and, therefore, are used to obtain the correction data for correcting the estimated TOA and/or distance.

An example of configuration session is provided by the method <NUM> in <FIG>, which embodies a step <NUM>, for example, and which may embodied, for example, the operations of the device <NUM>, for receiving transmissions performed, for example, by the transmitter <NUM>.

At step <NUM>, a transmission is started by the transmitter (the transmission will continue in the subsequent steps). According to examples, the transmission may be at baseband. A sequence code <NUM> of <NUM> length shaped with an RRC filter with <NUM> between <NUM> (e.g., <NUM>) samples per symbol at the transmitter is shown in <FIG>. However, other pulse shaped filters may be used.

At step <NUM>, the transmission is actually performed on the transmission channel. The transmission is received as a single signal <NUM> in <FIG> (it may be sampled, filtered and so on).

At step <NUM>, correlations R() are performed, e.g., using the correlation unit <NUM>. Each received signal may be understood as relating to a subsample "k". The reference to subsamples is justified in that information is provided on data which would not be achievable by simply estimating a distance or a TOA retrieving the peak sample. Further, using the sample determination unit <NUM>, the peak sample and correlation data of the additional samples immediately preceding and following the peak sample is acquired.

At step <NUM> (which may be performed, for example, by the configuration data definition unit <NUM>), configuration data are obtained for a subsample "k". For example, if the peak sample in the kth correlation profile is sample "i", the following calculations may be performed: <MAT> <MAT> <MAT>.

Notably, in this case, a corrlndex(k) value may be calculated for each subsample "k".

At step <NUM>, a projection of corrIndex(k) may be made over a finite number (e.g., K) of subsamples (e.g., of received configuration signals <NUM>). The number of subsamples may be, for example, the number of received configuration signals that are received by the receiver in the configuration session.

Projection of different corrlndex(k) for k=<NUM>. K may reflect the fact that, while the k values "corrlndex(k)" are samples (e.g., they are obtained as a succession of values), it is possible to obtain a continuous function which approximates the different data obtained by the different configuration signals.

At step <NUM>, a regression technique (e.g., linear regression) may be used to obtain a continuous function. A linear fitting function (or a quadratic fitting function) may be calculated from the multiple sample data. For example, coefficients a, b for a linear fitting function and/or coefficients a, b, c, for a quadratic function may be calculated.

<FIG> shows a graph <NUM> (abscissa: subsamples k; ordinate: amplitude) in which multiple points (each point associated to data obtained from a correlation to a configuration signal received by the receiver during a configuration session) have been used to approximate a linear function (e.g., using a linear fitting, linear regression) by a single line <NUM>. A least square method may be used to calculate the line <NUM>. The linear function may be described as: <MAT>.

The coefficients a and b may be the values a and b to be used in step <NUM> to embody the pre-assigned configuration data <NUM>. As it can be understood, the pre-assigned configuration data <NUM> may be easily obtained in the configuration session in the subsample resolution.

The configuration data <NUM> may be defined for each discrete value (TOA or distance) or for each possible peak sample which will be identifiable by performing correlations.

Accordingly, during the measurement session (operation session) a TOA from the estimated TOA is calculated and the function estimated by the corrlndex on the basis of the data obtained by the at least one sample close to the peak sample. The following three cases may be taken in account:
For example, in the measurement method <NUM>, after having identified the TOA at <NUM>, the having computed the corrlndex at <NUM>, having calculated the subsample correction as corrlndex/a-b/a with the pre-assigned configuration values a and b (obtained in the configuration session), the final TOA is calculated as a linear combination of the estimated TOA and a correction value. For example: <MAT>.

Correction may be, for example, obtained as: <MAT>.

<FIG> has a graph <NUM> showing in ordinate errors <NUM> in calculating the TOA after having applied the fitting method with a sampling time of <NUM> ns (abscissa: distance transmitter-receiver). It is possible to see that the error may be less than <NUM>, where in <FIG> the error could have been <NUM>,<NUM>. The error increase in the middle occurs when R(i-<NUM>) and R(i+<NUM>) are close to each other.

<FIG>shows a time difference of arrival, TDOA, localization system <NUM> comprising a transmitter <NUM> (which may be, for example, a mobile phone, a mobile terminal, a smartphone, a localization device, or a similar apparatus) which has to be localized (e.g., its distance has to be determined) and at least three synchronized receivers Rx1 <NUM>, Rx2 <NUM>, and Rx3 <NUM> (which may be base stations, e.g., of a mobile communication network, such as a GSM network or similar, or devices at known positions). The transmitter <NUM> is, for example, the transmitter <NUM>; at least one of the receivers Rx1 <NUM>, Rx2 <NUM>, and Rx3 <NUM> may be one of the device <NUM>, <NUM>, <NUM>. The distances d1, d2, d3 of the transmitter <NUM> from the receivers Rx1 <NUM>, Rx2 <NUM>, and Rx3 <NUM> are calculated using one of the methods <NUM>, <NUM> and/or <NUM>. By calculating the difference between TOAs (and, for example, by determining curves <NUM>, <NUM> for which the difference of the distances from two receivers is constant), the transmitter <NUM> is localized in a coordinate system (e.g., a geographical coordinate system). A configuration session (using the method <NUM> and/or <NUM> and /or the device <NUM>) may be performed. It is not strictly necessary that the transmitter that has performed the configuration session is the same of the transmitter <NUM> which is actually localized in the measurement session. The localization of the transmitter <NUM> may be performed, for example, by exchanging data (e.g., distances d1, d2, d3) between the receivers <NUM>-<NUM> and/or the transmitter <NUM>. By calculating the correction data (preferably on the basis of the pre-assigned configuration data <NUM>), the accuracy of the measurements is increased.

<FIG> shows a positioning system <NUM> which is a TOA positioning system. A receiver <NUM> (which may be, for example, a mobile phone, a mobile terminal, a smartphone, a localization device, or a similar apparatus) is to be localized. For example, the distances (e.g., indicated with <NUM>, <NUM>, <NUM>) of the receiver <NUM> from at least three (preferably at least four) transmitters Tx1 <NUM>, Tx2 <NUM>, Tx3 <NUM> (which may be base station or devices at known positions, or in any case transmitters with known position) are calculated. Accordingly, the position (e.g., in geographical coordinates) of the receiver is retrieved. The receiver <NUM> may be, for example, one of the devices <NUM>, <NUM>, or <NUM>, and/or may perform any of the methods <NUM>,<NUM>, and <NUM>. It is not necessary, in some examples, for the receiver <NUM> to also be the same receiver that has performed the configuration session. By calculating the correction data (on the basis of the pre-assigned configuration data <NUM> at a subsample resolution), the accuracy of the measurements is increased.

<FIG> shows a round trip time (RTT) system <NUM> for measuring the distance between two devices <NUM> and <NUM> (e.g. mounted on satellites or at least one being mounted on a satellite). As can be seen from <FIG>, the round trip time troundt may be obtained at least by a first transmission time tp for transmitting a first signal <NUM> from the device <NUM> to the device <NUM>. A time delay treply may elapse for permitting the processing to the device <NUM>.

A second transmission time tp for transmitting a second signal <NUM> from the device <NUM> to the device <NUM> (e.g., in response to the first signal <NUM>) may also be calculated. tp is calculated from troundt and treply (e.g., by subtracting treply from troundt and subsequently dividing by <NUM>) to obtain a time proportional to the distance between the devices <NUM> and <NUM>. When calculating the distance between the devices <NUM> and <NUM>, method <NUM>, <NUM>, or <NUM> is used. Therefore, when the first signal <NUM> is transmitted, the device <NUM> may be embodied by the device <NUM> and/or <NUM>. Additionally or alternatively, when the second signal is transmitted, the device <NUM> may be embodied by the device <NUM> and/or <NUM>. A configuration session has been performed at a subsample resolution to prepare the configuration data for the devices <NUM>, <NUM>. By calculating the correction data (on the basis of the pre-assigned configuration data <NUM>), the accuracy of the measurements is increased.

<FIG> shows a device <NUM> (which may implement at least one of the devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>, <NUM>) comprising a processor <NUM> which executesinstructions. The device <NUM> comprises a memory <NUM> which comprises processor readable instructions <NUM> which, when performed by the processor <NUM>, cause the processor <NUM> to perform one of the methods above (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>). The memory <NUM> also contains data <NUM>. The data <NUM> contains, for example pre-assigned configuration data (data <NUM>). When the device <NUM> implements a transmitter in the configuration session, the data <NUM> may contain location data, to be used for performing the configuration at a subsample resolution. The device <NUM> may comprise a transmission/reception unit <NUM> and an antenna <NUM>, e.g., to perform the signal transmissions or receptions discussed above. The device <NUM> may comprise an input/output (I/O) device for communication of data to an external device (e.g., a communication network and/or a display device to communicate a result to a user) and/or for receiving selections from a user.

In view of the above, it is possible to see that a particular example may comprise:.

It is possible to implement any of methods and apparatus disclosed here in the context of a long term evolution, LTE, network, <NUM>, <NUM>, etc (but which may be also used in other environments). In examples, the receiver <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> may be a user equipment (UE), which is connected to a base station (BS) which may be an evolved node (eNB) and/or a gNB.

<FIG> shows an example of method <NUM> based on at least one of LTE, <NUM>, <NUM> or another environment. The example is based on an OTDOA (observed time difference of arrival) strategy. LTE currently supports reporting within a sample. The highest RSTD resolution reporting is set to <NUM>*Ts which is equivalent to around <NUM> ns [<NUM>].

With the present example, a user equipment, UE, <NUM> (e.g., with respect to the location server <NUM>) is localized in subsample resolution.

The location server <NUM> (e.g., base station, eNB, gNB, etc.) may signal, at <NUM>, a request, such as "LPP request capabilities" (LTE Positioning Protocol=LPP, even if other protocols may be used). The UE <NUM> may reply, e.g., by signalling an "LPP provide capabilities", at <NUM>. The location server <NUM> may signal, at <NUM>, a request, such as "LPP provide assistance data". The location server <NUM> may signal, at <NUM>, a request, such as "LPP request location information". In <NUM> the location server may provide assistance information to the UE (for example which eNBs are in the UE region). In <NUM>, the server may request the location information, depending on the request options the UE sends it measurements. In <NUM> (Location server provides assistance data to UE), the server can update or provide the UE with configuration data. In our case, the UE may provide the location server in <NUM> that it is capable of performing high resolution measurements. If the UE is capable of making these measurements, the location server can request in <NUM> that the UE provides the location information in subsample accuracy.

The UE <NUM> may perform measurements at <NUM> regarding its position and, at <NUM>, signal a communication such as an "LPP provide location information", which may be as schema <NUM> of <FIG> any which may comprise data <NUM> "OTDOA signal measurement information", among which there may be, for example, the physical identifier <NUM> of the eNB, and/or the respective TOA <NUM> in sample accuracy (e.g., the estimated TOA <NUM>), and/or the value corrlndex <NUM> (or other information regarding the data from other samples, such as the sample preceding and the sample following the peak sample). In examples, the TOA may be measured for each eNB (or each location server or each base station), and the UE may report the ID of the base station which the TOA belongs to.

At <NUM>, the UE <NUM> may obtain data as above, by implementing steps <NUM>, <NUM> (and, in case, also <NUM>). The UE <NUM> operates, for example, as the device <NUM> (or at least as the components <NUM>-<NUM>), <NUM>, and/or <NUM>. In some examples, the UE <NUM> operates by measuring TDOAs obtained by transmissions received from a plurality of base stations <NUM>', <NUM>', <NUM>' as in <FIG> (in some examples, the location server <NUM> is one of the base stations <NUM>', <NUM>', <NUM>'). In some examples, TOAs (and not TDOAs) are transmitted. The location server <NUM> can build TDOAs from the TOA measurements reported from the UE. The TOA corresponding to the distances d1, d2, d3 in <FIG> may be obtained by using one of the methods <NUM>, <NUM>, <NUM> and/or one of its steps. By obtaining the difference between TOAs (and, for example, by determining curves <NUM>, <NUM> for which the difference of the distances from two receivers is constant), the receiver <NUM> is localized in a coordinate system (e.g., a geographical coordinate system). A configuration session (using the method <NUM> and/or <NUM> and/or the device <NUM>) may have been previously performed offline (also with different equipment and/or by simulation).

Accordingly, the UE <NUM> reports its location, at <NUM>, e.g., in subsample resolution. The UE <NUM> may measure the TOA from different base stations <NUM>', <NUM>', <NUM>'. One base station is chosen as reference and the TOA may be obtained in subsample accuracy on the basis of the signal transmitted by the based station.

Other examples may be based also with signaling procedure which differ, at least partially, from at least some of the communications at <NUM>, and in particular the communications at <NUM>-<NUM>.

Therefore, a UE <NUM> requiring a high accuracy mode for ranging or positioning applications, may:.

With reference to the example <NUM>), the UE <NUM> operates as the device <NUM> or <NUM> and/or perform all the steps of method <NUM> or <NUM>, so as to provide the TOA measurement <NUM> in the subsample accuracy.

With reference to the example <NUM>), the UE <NUM> transmits at least one (or a combination of):.

Then, the location server <NUM> (in LTE or <NUM>, for example) can compute the TOA <NUM> based on the reports (e.g., the values <NUM> and/or <NUM> provided by the UE <NUM>) and prior information (such as the pre-assigned configuration data <NUM> obtained through a configuration session performed offline), the location server <NUM> may estimate in subsamples the TOA. Therefore, in the example <NUM>), at least some of the components <NUM>, <NUM> and/or <NUM> of the device <NUM> may be in the location server <NUM>, while at least some of the components <NUM> and <NUM> may be in the UE <NUM> (other configurations are possible). The example <NUM>) is an example of the device <NUM> subdivided into two remote subdevices (the UE <NUM> being a first subdevice and the location server <NUM> being the second subdevice). Other different configurations are possible. In examples according to protocols such as D2D (device-to-device) and/or V2V (vehicle-to-vehicle) or similar techniques, two different UEs (which may be the devices <NUM> and <NUM> of <FIG>) may obtain their mutual distance and report it to a base station. We need just one of the two devices capable of reporting the measurements in subsample resolution to the Location Server (<NUM>). The reporting UE may send the peak sample or additional correlation values.

For ranging between two devices (D2D, V2V. ), the ranging devices can report the measurements to the location server, in coverage/RRC connected mode, that computes the range in high accuracy. For ranging between two devices (D2D, V2V. ), the ranging devices can report the measurements to the location server, in coverage/ RRC connected mode, that computes the range in high accuracy.

Another example (<FIG>) is obtained in the compensation of internal delays of a device <NUM> (e.g., a full-duplex device) which may, for example, compensate for delays of the device. If the device is capable of computing the internal delays (or performing compensation-of-internal-delays), for example in full-duplex mode, the sent is received through the RF receiver chain the device can compute the calibration and report it separately, or report the TOA and subsample measurement, or compensate the TOA calibration measurement and report the subsamples. In alternative or addition, a device may also indicate its capability of calibrating the transceiver delays (calibration capability flag) to the location server, for example.

As can be seen from <FIG>, it is possible to keep into account the delays τantenna due to an antenna switching and beamforming block <NUM>, the delays τRF due to a transceiver <NUM>, the delays τconv due to the analog to a digital conversion and analog to digital conversion block <NUM>. These blocks may be connected in cascade to a digital baseband processor <NUM> (which, in examples, may be the processor which controls the device <NUM> or <NUM>). It is possible to obtain a value associated to τantenna+τRF+τconv by simultaneously transmitting and receiving the same signal.

τantenna, τRF and τconv are transceiver delays. For positioning with one way approaches the difference (TDOA) may be built so that these delays cancel. If two-way ranging is applied the delays add an offset to measured range.

A device <NUM> can use the high sampling accuracy approach to compensate and/or report the delays if the device is capable, for example in full duplex mode the sent is received through the RF receiver chain the device can compute the calibration and report it separately, or report the TOA and subsample measurement, or compensate the TOA calibration measurement (by performing the correction at block <NUM>, for example) and report the subsamples.

Therefore, a full-duplex device performing the compensation-of-internal-delays process implements at the same time the transmitter and the receiver. The steps <NUM>, <NUM>, and <NUM> of the method <NUM> may be based, therefore, on the signal transmitted by the same full-duplex device. In this case, the TOA is not to be understood as being associated to a distance, but to the delays implied by the components (<NUM>, <NUM>, <NUM>) of the full-duplex device <NUM>.

If the full-duplex device <NUM> operates under LTE, <NUM>, etc., the device <NUM> may also signal its internal delay to a base station (e.g., eNB, gNB, location node). In some cases, the full-duplex device <NUM> may only implement the steps <NUM> and <NUM> and/or the elements <NUM> and <NUM>, and signal the peak sample <NUM> and the data from other samples (e.g., the sample preceding and the sample following the peak) to the base station, which may, in turn implement the step <NUM> and/or the blocks <NUM>, <NUM>, and <NUM> (obtaining pre-assigned configuration data).

A receiver according to the invention is independent of the particular pulse shaping technique that it adopted (if any). Gaussian and root raised cosine (RRC) may be used, for example.

Time of arrival (TOA) estimate is fundamental for applications like ranging, positioning and time synchronization applications. The TOA is often derived from the correlation result between the received signal and a reference signal. The TOA can be directly be derived from the correlation peak the accuracy is however limited by the sampling rate. Hence a high resolution approach must be carried after the correlation to obtain sub-sample corrections. The profile of the correlation result is also dependent on the channel
characteristics. These characteristics generate extra errors if not compensated or taken into account.

In addition to accuracy, the computational intensity plays an important role in the choice of the algorithm due to the limited resources on the target platform.

In the presence of a line of sight (LOS) signal reception, the correlation profile carries the required time delay information to calculate the TOA. The correlation maximum provides a coarse TOA estimate in sample accuracy. To achieve higher accuracy, the initial TOA estimate has to be corrected in subsample resolution. <FIG> and <FIG> show the ideal correlation profile in the dashed line and the computed correlation at the receiver side with sampling rate of 10ns. In <FIG> the received signal is aligned with the reference signal (<NUM>°) and the resulting subsampling correction is hence zero. However with <NUM>° phase difference as shown in <FIG> the detected maximum deviates from the ideal maximum with a Δd which is <NUM> in this case.

The method proposed for estimating the subsample corrections operate in two modes (sessions). In the first mode (configuration session) the effects of the channel and transmit sequence on the correlation profile are modeled. The second mode (measurement session) is during the operation: the subsample correction are estimated based on the modeled profile directly from the computed correlation at the receiver side.

The flowchart in <FIG> shows the offline operation in the first mode. A pulse shaped transmit sequence is sent over a channel. <FIG> shows a sequence shaped with an RRC filter (however any pulse shaped filter can be used for this method).

The channel in this scenario emulates the effect of time-delay on the received correlation profile. The next step correlation profile is collected over K subsamples as shown in <FIG> for time delays k<NUM> and k<NUM> within one sample. R(i,k) represents the correlation maximum between the received signal y and the reference signal x. R(i-<NUM>,k) and R(i+<NUM>,k) represents the points in correlation profile before and after the maximum respectively. R (i-<NUM>,k) and R (i+<NUM>,k) are collected over K correlations. For each k correlation diff_R (k) and sum_R (k) are computed, represented by: <MAT> <MAT>.

The index corrlndex(k) is then computed as corrlndex(k) = diff_Rxy(k) / sum_Rxy(k). <FIG> shows the index corrlndex(k) for K=<NUM>. In some cases quadratic fitting might be more suitable.

During operation, or in the second mode (measurement session), the digital receiver can correct the TOA using the coefficients a and b in the above case. The subsample correction is simply computed as <MAT> and lastly the fine TOA measurement is obtained by linearly modifying the correction to the initial coarse TOA. For example, the following formula may be used: <MAT> K may be a fixed value. For example, K may be the number of subsamples (correlations calculated in the configuration session).

Therefore, it is possible to resume that TOA, which is often fundamental for distance for measurements, may be normally estimated by means of a cross-correlation between a received signal and a reference signal. The sample accuracy is often not sufficient for applications like positioning and ranging. The current methods are inaccurate or have a high computational complexity. The present methods target small devices because of the low complexity and the accurate extraction of the TOA form one snapshot given that the correlation profile is not distorted.

Two modes of operations are executed: offline mode (configuration session) and operation mode (measurement session). In the offline mode the mapping of the correlation profile to the corresponding time delay is performed, and later, fitted to an algebraic equation. This procedure may be performed once. In the operation mode (measurement session) the receiver calculates the correlation profile index and solvers the algebraic equations to perform measurement sin the subsample accuracy. A last step in the TOA measurements may be corrected by subsample corrections.

In some examples, some one or more of the most important method steps may be executed by such an apparatus.

Depending on certain implementation requirements, examples can be implemented in hardware or in software.

Some examples comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

Generally, examples can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer.

Other examples comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier.

In other words, an example of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

A further example of the inventive methods is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein.

A further example of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein.

A further example comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein.

A further example comprises a computer having installed thereon the computer program for performing one of the methods described herein.

A further example comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver.

In some examples, a programmable logic device (for example a field programmable gate array) may be used to perform some or all of the functionalities of the methods described herein. In some examples, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein.

Claim 1:
A method (<NUM>) for time of arrival, TOA, measurements of transmissions transmitted by a transmitter in a transmission channel, the transmission channel being the environment, the method comprising a configuration session (<NUM>') and a measurement session (<NUM>),
wherein the configuration session (<NUM>') comprises:
performing (<NUM>) a plurality of correlation processes for a plurality of configuration signals to obtain multiple configuration correlation functions associated to known different distances at a subsample resolution, the plurality of configuration signals being received in the transmission channel from the transmitter;
for each configuration correlation process, determining (<NUM>) the peak sample (<NUM>) and data (<NUM>) of one sample immediately preceding and one sample immediately following the peak sample (<NUM>) for each correlation; and
determining (<NUM>), from the determined peak sample (<NUM>) and the data (<NUM>) of the one sample immediately preceding and the one sample immediately following the peak sample (<NUM>), pre-assigned configuration data associated to the transmission channel; and
wherein the measurement session (<NUM>) comprises:
performing (<NUM>), at a sample resolution, a correlation process on a received measurement signal (<NUM>) to obtain a measurement correlation function (<NUM>), the subsample resolution being higher than the sample resolution;
determining (<NUM>) a peak sample (<NUM>) and correlation data (<NUM>) of one additional sample immediately preceding and one additional sample immediately following the peak sample (<NUM>) in the measurement correlation function (<NUM>); and
determining (<NUM>) a TOA and/or distance (<NUM>) associated to the TOA on the basis of the peak sample (<NUM>) and correction data (<NUM>) obtained by at least the correlation data (<NUM>) of the additional sample immediately preceding and the additional sample immediately following the peak sample (<NUM>) and the pre-assigned configuration data (<NUM>) associated to the transmission channel obtained at the subsample resolution.