Patent Description:
In LTE network, localization is based on Positioning Reference Sequences (PRS) sequences transmitted in the PDSCH, see [<NUM>][<NUM>].

Other data can be used, e.g. DoA (Direction of Arrival) measurement. Drawbacks are:.

Timing Advance, Observed Time Difference of Arrival (ODToA), Uplink Time Difference of Arrival UDToA based positioning are currently limited by.

Therefore, accuracies in the range of <NUM> can't be achieved.

<CIT> teaches a communications device which is configured to transmit signals to and/or receive signals from an infrastructure equipment of a mobile communications network. The communications device comprises a receiver configured to receive signals transmitted by an infrastructure equipment of a mobile communications network, the signals being transmitted in accordance with a wireless access interface and including at least one positioning reference signal transmitted in each of a plurality of time units. The communications device includes at least one antenna connected to the receiver, a motion detector configured to determine a relative local position of the communications device, and a controller configured to generate a measurement data set comprising a plurality of measurement samples of at least a phase of the positioning reference signal according to a sampling rate, and a location of the communications device at which the phase of the positioning reference signal was determined.

<CIT> (a document comprised in the art according to Art <NUM>(<NUM>) EPC) discloses a method by which a terminal performs location measurement on the basis of a PDOA in a wireless communication system, wherein a UE may report, to a location server, a signal indicating information as to whether the UE has a capability of performing measurement of a phase difference of a signal corresponding to each path by distinguishing between signals received from a plurality of paths using spatial filtering or an antenna array.

In view of the above, there exists a desire for an improved concept to localize user mobile devices, e.g. with a higher precision.

The invention is defined by the independent claims, with particular embodiments comprised in the dependent claims.

In this section, embodiments are embodiments of the disclosure, and may not reflect the embodiments of invention as defined by the claims.

An embodiment provides a communication apparatus of a cellular communication network. The communication apparatus is configured to receive a reference signal, to estimate a phase estimate based on the received reference signal and to provide a (time difference of arrival (TDOA), time of arrival (TOA) or angle of arrival (AOA) based) localization module with the phase estimate.

The described embodiment is based on the idea that a localization using a phase estimate (e.g. a carrier phase measurement or a phase difference measurement) can provide a higher precision for localization. In other words, using a phase-based localization can achieve a better localization result compared to only using time measurements for localization. Moreover, usage of a phase-based estimation in a mobile communication apparatus is especially useful e.g. for precise localization of people in emergency situations. For example, in natural disaster areas it is of paramount importance to be able to localize and rescue people fast.

The communication apparatus is part of a user equipment of the cellular communication network. Having the communication apparatus may enable localization by the user equipment itself, which in turn may communicate its location to a base station.

In embodiments, the communication apparatus may comprise the localization module, and wherein the localization module is configured to determine a position of the user equipment. The described embodiment allows for an independent localization of the user equipment without the need of computational resources of a base station or the cellular network (aside from reception of the reference signal).

In embodiments, the communication apparatus may be configured to transmit a phase estimate capability flag to a base station, wherein the phase estimate capability flag indicates that the communication apparatus is capable of performing a phase estimate. The described embodiment can communicate to a base station or the cellular network that it is able to perform phase measurement, such that a high precision localization based in the phase estimate can be performed.

In embodiments, the communication apparatus may be configured to communicate via a base station of the cellular communication network the phase estimate to the localization module for use in determination of the position of the user equipment. The described embodiment allows for the localization to be performed outside of the user equipment although performing the phase estimation in the user equipment. Thereby, the described embodiment allows for flexible task assignment.

In embodiments the communication apparatus may be configured to transmit antenna port information of the communication apparatus to a base station, wherein the antenna port information indicates which antenna is used to receive the reference signal. Knowledge about which antenna can be useful e.g. in MIMO setting where multiple antennas are located close to each other. However, small distances between the antennas lead to large phase differences, due to a comparably small wavelength.

In embodiments, the communication apparatus may be configured to receive a plurality of reference signals from a plurality of transmitters, to estimate a plurality of phase estimates from the plurality of reference signals and to receive from the plurality of transmitters synchronicity information indicating a measure of synchronicity among the plurality of transmitters. Moreover, the communication apparatus may be configured to, if the synchronicity measure fulfills a predetermined criterion, perform the estimation and provide the plurality of phase estimates to the localization module, or if the synchronicity measure does not fulfill the predetermined criterion, refrain from at least the providing the plurality of phase estimates to the localization module. The described embodiment can flexibly decide if received reference signals may be useful in a localization based on the phase estimate, e.g. if the transmitters are transmitting sufficiently synchronous for phase-based localization. Moreover, the transmitters may have a common clock source to achieve synchronization.

In embodiments, the communication apparatus may be configured to derive a plurality of time measurements from the reference signals or further reference signals from the plurality of transmitters and to provide the plurality of time measurements in addition to the plurality of phase estimates to the localization module if the synchronicity measure fulfills the predetermined criterion. Alternatively, the communication apparatus may be configured to provide the plurality of time measurements to the localization module if the synchronicity measure does not fulfill the predetermined criterion. The described embodiments can beneficial combine time measurements (e.g. using a cross correlation) and phase estimate to obtain a precise location estimate of the user equipment, for example, more precise than using phase estimate or time measurements alone for localization. Moreover, the transmitters may have a common clock source to achieve synchronization.

In embodiments, the communication apparatus may be configured to determine a quality measure according to a first mode and to accompany the plurality of phase estimates and the time measurement with the quality measure if the synchronicity measure fulfills the predetermined criterion. Alternatively, the communication apparatus may be configured to determine the quality measure according to a second mode differing from the first mode and to accompany the plurality of time measurements with the quality measure if the synchronicity measure does not fulfill the predetermined criterion. The described embodiment can indicate a quality of the received reference signals, wherein a low quality may not be useable for localization using phase estimates. In other words, having bad quality phase estimates, e.g. due to multipath propagation, the localization can be performed more precisely using only the time measurements.

In embodiments, the localization module may be configured to selectively enable phase estimate-based localization if two or more reference signals are received from a number of synchronized transmission points ( e.g. eNBs (eNodeBs) or RRHs (remote radio heads)). If the transmission are sufficiently well-synchronized the reference signals received therefrom can be easily used for precise localization of a UE. Moreover, the transmitters may have a common clock source to achieve synchronization.

In embodiments, the communication apparatus may comprise the localization module, and the localization module may be configured to determine a position of the user equipment using the phase estimate. Alternatively, the localization module may reside outside of the communication apparatus and the communication apparatus may be configured to communicate the phase estimate to the localization module for use in the determination of the position of the user equipment. The described embodiment allows for flexible assignment of computational tasks, depending on where the localization module resides.

In embodiment, the user equipment may comprise the localization module, and the communication apparatus may be configured to provide the localization module of the user equipment with the phase estimate for use in the determination of the position of the user equipment. Thereby, the described embodiment allows for a high degree of flexibility, where the localization is performed.

In embodiments, the communication apparatus may be configured to receive antenna port information, wherein the antenna port information indicates from which antenna of transmitter the reference signal is transmitted. Having information about a used antenna can be used for precise localization, as transmitters may have multiple antennas which may be slightly distanced, resulting in a large phase difference.

In embodiments, the communication apparatus may be configured to receive a second reference signal, to estimate a second phase estimate based on the second reference signal and to provide the localization module with the second phase estimate. Having a higher number of phase estimates may be useful to obtain a more precise localization.

In embodiments, the second reference signal may be transmitted from a different transmitter than the reference signal; thereby, a second pseudorange or relative distance may be obtained useful for triangulation.

In embodiments, the apparatus may be configured to estimate a time measurement (e.g. useful for TDOA or TOA) based on the received reference signal and to provide the localization module with the time measurement. Further, the localization module may be configured to determine a position using the phase estimate and the time measurement. Using a combination of time measurement and phase estimate allows to enable a more precise localization than using either one individually.

In embodiments, the localization module may be configured to determine the position by combining at least one of time difference of arrival (TDOA) measurement, time of arrival (TOA) measurement and angle of arrival (AoA) measurement with the phase estimate. The described embodiment allows for combining various time or angle based approaches with a phase estimate to achieve localization.

In embodiments, the communication apparatus may be configured to receive a plurality of reference signals from a plurality of transmitters, to estimate a plurality of phase estimates from the plurality of reference signals and to derive a plurality of time measurements from the reference signals or further reference signals from the plurality of transmitters. Moreover, the communication apparatus may be configured to provide the plurality of time measurements in addition to the plurality of phase estimates to the localization module, to determine a first quality measure indicating a quality of the plurality of phase estimates and a second quality measure indicating a quality of the plurality of time measurements and to accompany the plurality of phase estimates and time measurements with the first and second quality measures. The described embodiment allows for a localization to rely on the time measurements or phase estimates depending on their reliability, e.g. measurements or estimates with high quality over those with worse quality to perform a more precise localization.

In embodiments, the communication apparatus may be configured to receive a plurality of reference signals from a plurality of transmitters, to estimate a plurality of phase estimates from the plurality of reference signals, to derive a plurality of time measurements from the reference signals or further reference signals from the plurality of transmitters and to provide the plurality of time measurements in addition to the plurality of phase estimates to the localization module. Further, the localization module may be configured to determine the position by applying the plurality of phase estimates as phase differences between pairs of the plurality of transmitters. Using phase differences allows for a smoothed result, such that big outlier may be avoided which may be due to estimation errors or ambiguity problems.

In embodiments, the communication apparatus may be configured to receive observed time difference of arrival assistance data associated with a reference signal configuration. Thereby, the communication apparatus can, for example, be informed about which kind of reference signals are used, which antenna port is used for transmission of the reference signal or which time-frequency arrangement is used, i.e. at in which time slot and/or at which frequency slot the reference signal is send. Moreover, integration in existing systems may be simplified, which may already use an observed time difference of arrival based method.

In embodiments, the communication apparatus may be configured to determine a measure indicating as to how strong the received reference signal is subject to multipath propagation, wherein the communication apparatus is configured to accompany the phase estimate with the multipath measure. Having knowledge about multipath propagation of the received signal can be a strong indicator of reliability of the phase estimate for localization. Moreover, in context of phase estimation multipath propagation may have a stronger detrimental effect than, for example, in time measurements.

In embodiments, the apparatus may be configured to estimate the phase estimate using a prediction of the phase estimate, wherein the prediction is based on previously estimated phase estimates. Using prediction of the phase estimate, e.g. based on previously estimated phase estimated, allows for compensating of large outliers which may be due to measurement errors.

In embodiments, the communication apparatus may be configured to transmit a quality indicator to a base station, wherein the quality indicator describes a quality of the phase estimate. Having a quality indicator of the estimate allows the apparatus to decide whether to use the phase estimate for localization or instead provide the localization with other data, e.g. time measurements, for localization.

In embodiments, the communication apparatus may be configured to provide a phase difference estimate based on a previous phase estimate and the received reference signal. Using a phase difference may reduce errors due to phase ambiguities.

In embodiments, the communication apparatus may be configured to provide observed time difference of arrival (OTDOA) location information elements, wherein the OTDOA location information elements comprise the phase estimate, and/or antenna port information, and/or a quality indicator, and/or a time measurement. The described embodiment allows combining the described element as OTDOA location information elements.

In embodiments, the communication apparatus may be configured to estimate the phase estimate based on a complex-valued correlation of the received reference signal, if no multipath propagation has been detected. In other words, an angle of a complex-valued correlation value can be translated to the phase estimate.

Embodiments provide a cellular network comprising a Communication apparatus according to one of the herein described embodiments, and the localization module. Embodiments provide a localization method, e.g. for use in a cellular network, comprising receiving a reference signal, estimating a phase estimate based on the received reference signal and providing a localization module with the phase estimate.

An embodiment provides for a computer program with a program code for performing the method on a computer or a microcontroller.

In the following, embodiments of the present invention will be explained with reference to the accompanying drawings, in which:.

<FIG> shows a schematic block diagram of a communication apparatus <NUM> according to embodiments of the invention. The apparatus <NUM> comprises a phase estimator <NUM> and may optionally comprise a localization module <NUM> which may reside within the communication apparatus <NUM> but may also be residing outside of the communication apparatus <NUM>.

The communication apparatus <NUM> is part of a cellular communication network and is configured to receive a reference signal <NUM>. Based on the reference signal <NUM> the apparatus is configured to estimate a phase estimate <NUM>. Further, the apparatus is configured to provide a (e.g. TDOA-, TOA- or AOA-based) localization module <NUM> with the phase estimate <NUM>.

Further features and functionalities of the communication apparatus <NUM> will be described in more detail with the following embodiments. Further, same reference signs identify identical or similar functionalities. The described embodiment can be supplemented either individually or in combination by any features or functionalities described herein with respect to embodiments which are encompassed by the claims.

<FIG> shows a schematic block diagram of a communication apparatus <NUM> according to embodiments of the disclosure. The apparatus <NUM> comprises a phase estimator <NUM>, an optional quality determiner <NUM>, an optional phase predictor <NUM>, an optional time estimator <NUM> and a localization module <NUM>. The localization module may also be located outside of apparatus <NUM>, e.g. on a server of the cellular network or in the base station.

The communication apparatus <NUM> is provided with a received reference signal <NUM> wherefrom the phase estimator <NUM> derives a phase estimate <NUM>. The phase estimate <NUM> can either be provided directly to the localization module <NUM> or it may be provided to the phase predictor <NUM> which may perform a prediction of the phase. The localization module <NUM> can also be provided with the predicted phase estimate <NUM>. Moreover, the reference signal <NUM> may also be provided to the time estimator <NUM> which can obtain time measurements e.g. using a correlation (TOA, TDOA). The time estimator <NUM> may provide the localization module <NUM> with a time measurement <NUM> usable for localization. Further, the reference signal <NUM> may also be provided to the quality determiner <NUM> which may asses the quality of the received reference signal <NUM>, e.g. if it is subject to multipath propagation or a signal-to-noise ratio.

<FIG> shows a schematic block diagram of cellular network <NUM> according to embodiments of the invention. The cellular network <NUM> comprises a communication apparatus <NUM> and a localization module <NUM>. The communication apparatus <NUM> may be one of the communication apparatus according to <FIG> or <FIG>.

<FIG> shows an illustration of synchronized transmitters <NUM>. In other words, <FIG> shows a cell with multiple remote radio heads/ transmission points [<NUM>]. The synchronized transmitters <NUM> comprise a base station <NUM> (extended NodeB, eNB), which is connected through a wired or wireless link to remote radio heads <NUM> (RRH) which act as extension of the base station <NUM>. Through the link a high degree of synchronization can be achieved which is especially useful for phase-based localization, i.e. when receiving reference signals from multiple remote radio heads <NUM> and using them for phase-based localization.

<FIG> shows a data structure <NUM> used for signaling capabilities of a communication apparatus according to embodiments of the invention. The data structure <NUM> comprises a field labeled phase measurements which can be set as active, to indicate to another communication apparatus (e.g., a base station) that the device is able to perform phase measurements and, thereby, determine the phase estimate or multiple phase estimates.

<FIG> shows an OTDOA location information structure <NUM> according to embodiments of the invention. In other words, <FIG> shows Phase measurement as an additional part of OTDOA Location Information Elements from [<NUM>]. The structure <NUM> may be provided by a communication apparatus (e. g, apparatus <NUM>, <NUM> or <NUM>) according to embodiments to a localization module (e.g. localization module <NUM> or <NUM>). The data structure <NUM> comprises a data structure <NUM> for phase measurements. It can comprise raw phase measurement data <NUM> and/or phase difference measurement data <NUM>. The raw phase measurement data <NUM> may comprise a carrier phase measurement, antenna port information and/or a quality parameter. The phase difference measurement data <NUM> may comprise a phase difference measurement (with respect to reference cell and period), antenna port information and/or a quality parameter. Based on the data structure <NUM> a localization can be performed e.g. by the localization module.

<FIG> shows a flow chart of a method <NUM>. The method comprises receiving <NUM> of a reference signal, estimating <NUM> a phase estimate based on the received reference signal and providing <NUM> a localization module with the phase estimate. The described method can be supplemented by any of the features and functionalities described herein with respect to apparatus, individually or in combination.

Some embodiments 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.

In other words, an embodiment of the inventive method is, therefore, a computer program having a program code for performing the method of claim <NUM>, when the computer program runs on a processor of the communication apparatus of claim <NUM>.

A further embodiment is 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 embodiment is a data stream or a sequence of signals representing the computer program for performing one of the methods described herein.

A further embodiment 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.

The above described embodiments are merely illustrative for the principles of the present invention. It is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending patent claims and not by the specific details presented by way of description and explanation of the embodiments herein.

In the following additional features will be described which can be optionally included in any of the above described embodiments.

In conventional concepts GNSS (Global Navigation Satellite System) enhance their position accuracy by not just doing pseudorange measurements (equivalent to TOA), but also doing carrier phase measurements. Phase ambiguities (between satellites and terminals) that naturally arise if you measure phase that repeats every wavelength are resolved by algorithmic approaches like Real Time Kinematic (RTK) or Precise Point Positioning (PPP).

Like explained in Reference [<NUM>], carrier phase measurements are as well employed in terrestrial positioning systems. In the case of [<NUM>], carrier phase ambiguities are not resolved. Here, carrier phase is used to describe relative movements and effectively smooths trajectories that would be noisy if based on TOA only.

In the following aspects underlying embodiments are listed.

In the following smoothing of TOA using phase measurements according to embodiments is discussed.

In the following it is discussed how to resolve ambiguities in phase measurements to smooth TOA.

In the following a special scenario for carrier phase measurements with remote radio heads and distributed antenna systems is discussed, see <FIG>.

In a setup (<FIG>), where eNBs are installed at different sites, phase coherent transmission can hardly be assumed. However, in a setup with multiple remote radio heads (RRHs), Transmission Points (TPs), or with a distributed antenna system, fully coherent transmission can be achieved.

To make use of fully coherent transmission for positioning, signaling to the UE, which performs carrier phase measurements may be helpful:
If a UE has received a set of OTDOA assistance data:
If #TPs associated to single PCI > <NUM>:
If coherent-tp:
Enable support for carrier phase-based positioning for all
TPs associated to a single PCI
else:
No support for carrier-phase based positioning for TPs
associated to PCI.

In the following LPP (LTE positioning protocol) signaling and implementation relevant aspects are discussed.

In the following LPP signaling for phase smoothing is discussed.

No extra signaling may be necessary (it is assumed that eNB reports the antenna port for PRS).

In the following LPP signaling for RRH scenario is discussed.

In the following LPP signaling for phase ambiguity resolution is discussed.

In the example in <FIG>, the phase measurement is shown as an additional part of the OTDOA Location Information Elements from [<NUM>], which includes the two options as already described above:.

Independent of option <NUM> or <NUM> the report may include the antenna port and a quality parameter (to be defined) the different part is:.

In the following aspects of the embodiments of the invention are given as a list.

Embodiments provide an increase of accuracy in an optimal case from <NUM> to cm-range. Further, embodiments signal carrier phase measurements from a UE to a network. Embodiments are services that require (accurate) position information. Moreover, embodiments describe a method to improve positioning in mobile communication networks. Embodiments describe usage of carrier phase for positioning in mobile communication networks.

Claim 1:
Communication apparatus (<NUM>; <NUM>; <NUM>) of a cellular communication network, wherein the communication apparatus is part of a user equipment of the cellular communication network,
wherein the communication apparatus is configured to
receive two or more reference signals from a number of synchronized eNodeBs;
estimate phase estimates based on the received reference signals; and provide a localization module (<NUM>; <NUM>) with the phase estimates;
characterised in that the communication apparatus is configured to transmit a phase estimate capability flag to a communication device, wherein the phase estimate capability flag indicates that the communication apparatus is capable of performing a phase estimate
wherein the communication apparatus is configured to provide the phase estimates to the localization module as part of a data structure which further comprises antenna port information wherein the data structure is comprised in a OTDOA location information structure.