WO2019034252A1

WO2019034252A1 - Techniques for determining localization of a mobile device

Info

Publication number: WO2019034252A1
Application number: PCT/EP2017/070798
Authority: WO
Inventors: Wen Xu; Saeed SHOAJEE; Konstantinos MANOLAKIS
Original assignee: Huawei Technologies Duesseldorf Gmbh
Priority date: 2017-08-17
Filing date: 2017-08-17
Publication date: 2019-02-21

Abstract

The disclosure relates to a mobile device (1010), comprising: a receiver (1011), configured to receive at least one radio signal (1025, 1035, 1045) from a corresponding radio transceiver, in particular a base station (1020, 1030, 1040), wherein the at least one radio signal comprises at least one carrier component (401, 402), CC, comprising a set of pilot symbols for localizing the mobile device (1010); and a processor (1012), configured to determine localization information (1013), in particular a time of arrival, TOA, of the at least one radio signal (1025, 1035, 1045), based on the set of pilot symbols of the at least one CC (401, 402).

Description

Techniques for determining localization of a mobile device

TECHNICAL FIELD

The present disclosure relates to mobile devices and base stations in a radio communication system. In particular the disclosure relates to techniques for determining localization of a mobile device, in particular high accuracy localization with multiple carrier bands, also referred to as Carrier Aggregated Timing Estimation (CATE).

BACKGROUND

In mobile radio communication networks 100 as illustrated in Figure 1 , e.g. according to 3GPP standardization, several cellular-based localization techniques can be applied. Observed time difference of arrival (OTDOA) is a positioning method, e.g. used in the Long Term Evolution (LTE) system. It specifies a multi-lateration method in which the User Equipment (UE) 1 10 measures the time of arrival (TOA) of signals received from multiple base stations (eNodeB's) 101 , 102 and 103. The TOAs from several neighbor eNodeB's are subtracted from a TOA of a reference eNodeB to form OTDOAs. Each time difference maps to a geometrical hyperbola which relates to the location of the desired UE. At least three timing measurements are required to find the position of the UE 1 10 in two coordinates (latitude/longitude). Figure 1 illustrates this OTDOA positioning method: The UE 1 10 measures three TOA's (τ1 , τ2, τ3), relative to the UE's 1 10 internal time base. This method reduces the dependency on the UE's internal clock, which may have less accuracy than the base stations' clocks.

Accurate TOA TDOA estimation is a challenging task in mobile communication due to the fast varying channel and low Signal-to-Noise Ratio (SNR). Therefore, 3GPP has specified the Positioning Reference Signal (PRS) for the LTE system. 3GPP specified a Reference Signal Time Difference measurement (RSTD), to measure TOA and TDOA by UE 1 10. The RSTD is defined as the relative timing difference between two cells calculated as the smallest time difference between subframe boundaries received from two different cells.

In the LTE system, the Positioning Reference Signals (PRSs) in a carrier band (e.g. of 2.1 GHz) have been used for the purpose of UE positioning. It can have an accuracy of several tens or hundreds of meters, as shown by W. Xu, M. Huang, C. Zhu and A. Dammann: "Maximum likelihood TOA and OTDOA estimation with first arriving path detection for 3GPP LTE system," Transactions on Emerging Telecommunications Technologies (ETT), 2014. This accuracy is not adequate for many applications like vehicular-to-anything (V2X) communication, device-to-device (D2D) communication, etc.

SUMMARY

It is the object of the invention to provide an efficient technique for localizing a mobile device.

It is a further object of the invention to improve the accuracy of the User Equipment (UE) localization significantly, in particular to an accuracy within the centimeter level, e.g. for a mobile communications standard such as Long Term Evolution (LTE).

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. A main idea of the invention is that for achieving higher accuracy localization, one or more parameters, such as signal bandwidth of the reference signal, receiver signal-to-noise-ratio (SNR), pilot density, or the acquisition time needs to be increased. In LTE, though the positioning reference signal uses up to the whole available bandwidth the accuracy of the localization would be lower bounded by several meters. Although increasing transmit power results in higher SNR at the receiver and therefore increases the accuracy of the positioning, to achieve centimeter level accuracy, the eNodeB would have to increase its transmit power up to 90dB, which is usually not achievable in practice.

Studies show that the lower bound of the accuracy is not only dependent on the receiver SNR, but also on the power distribution of the reference signal spectrum. That is, a reference signal at the edges of the carrier band will result in better positioning rather than a reference signal in the middle of the carrier band. Hence, the main concept according to this disclosure is to use multiple carrier bands jointly for the positioning. In the following, this concept is referred to as "Carrier Aggregated Timing Estimation (CATE)" as described in this disclosure.

The disjoint use of two carrier bands, i.e. using the two carrier bands separately, improves the accuracy by about 3dB, however, the joint carrier positioning, i.e. using the two carrier bands jointly for positioning as if they were one wide band, improves the positioning accuracy by a significantly larger factor. This is due to the larger bandwidth of the overall multiple-carrier signal and the fact that reference signals occupy edges of a larger spectrum in frequency domain. According to CATE, multiple carrier bands are utilized in a joint manner for positioning applications, i.e. as if they were one wide band, in which two or more carrier bands need to be synchronized. This increases the effective mean square bandwidth of the reference signal and therefore decreases the achievable variance of the positioning error, according to the Cramer- Rao Lower Bound (CRLB). As CRLB scales inversely with the effective bandwidth of the positioning signal, significant improvement in positioning accuracy can be obtained through CATE. In order to enable such joint position estimation, this disclosure presents the framework including required signaling, pilot design and user equipment (UE) implementation aspects. In order to describe the invention in detail, the following terms, abbreviations and notations will be used:

LTE: Long Term Evolution

BS, eNodeB: Base Station, or Access Point

UE: User Equipment or mobile device

CATE: Carrier Aggregated Timing Estimation

TOA: Time of Arrival

TDOA: Time Difference of Arrival

PRS: Positioning Reference Signal

RSTD: Reference Signal Time Difference

OTDOA: Observed Time Difference of Arrival

SNR: Signal to Noise Ratio

CRLB: Cramer-Rao Lower Bound

LPF: low pass filter

RF radio frequency

IFFT: inverse Fast Fourier transform

PA: power amplifier

D/A: digital to analog converter

BB: baseband

CC: Carrier Component

According to a first aspect, the invention relates to a mobile device, comprising: a receiver, configured to receive at least one radio signal from a corresponding radio transmitter, in particular a base station, wherein the at least one radio signal comprises at least one carrier component (CC), comprising a set of pilot symbols for localizing the mobile device; and a processor, configured to determine localization information, in particular a time of arrival, TOA, of the at least one radio signal, based on the set of pilot symbols of the at least one CC. A CC as described hereinafter represents a specific frequency band which is transmitted based on a specific carrier frequency. The carrier frequency may specify a middle frequency of the frequency band, i.e. the CC. In this invention, a CC, may be a carrier band of a radio system (e.g. WiFi, 2G, 3G, 4G, 5G, etc). For multiple CCs, the CCs may be from the same radio system (e.g. 4G) or from different radio systems (e.g. one CC from GSM and another from WiFi, one CC from 4G and another CC from 3G, ...), or their mixture thereof. Normally, the carrier frequency of multiple CCs are different from each other. Such a mobile device (e.g. a handset, a vehicle, ) may implement the CATE concept according to this disclosure. This means, the mobile device can utilize multiple carrier bands to increase the effective bandwidth of the aggregated signal used for localization. Multiple carrier bands sent from a single base station can be combined. Such a mobile device can use higher sampling rate to process and/or larger FFT to down-convert multiple carrier band signals. The mobile device can in fact increase the square bandwidth term in denominator of CRLB, resulting in a higher accuracy of localization estimation. Direct benefits of CATE are the following: Existing pilots in multiple carriers can be jointly used at the receiver side, as if they were pilots of a single (aggregated) wideband carrier. Due to higher overall bandwidth with pilots at the edges of the wideband carrier, the CRLB is significantly improved (lower). Using a maximum likelihood (ML)-like detection method which can achieve the CRLB leads consequently to a significantly higher timing estimation. Besides, no additional hardware components are needed.

In a possible implementation form of the mobile device, at least two CCs of the same radio signal or of different radio signals are transmitted on different carrier frequencies with respect to each other.

When using different CCs, higher accuracy can be achieved. These different CCs can be either transmitted by the same radio signal or by different radio signals, e.g. a first radio signal from a first base station and a second radio signal from a second radio station. I.e., the mobile device provides flexibility with respect to the choice of the CCs.

In a possible implementation form of the mobile device, the processor is configured to determine the localization information based on a joint processing of the set of pilot symbols of at least two CCs. By applying joint processing of the set of pilot signals of the component carriers a higher accuracy can be provided.

In a possible implementation form of the mobile device, at least two CCs are contiguously arranged within a frequency band of the at least one radio signal.

Contiguous CCs are seen - from localization standpoint - as a single band, where CCs are multiplexed and passed through a single IFFT. This can reduce computational complexity of the mobile device.

In a possible alternative implementation form of the mobile device, at least two CCs are noncontiguous^ arranged within a frequency band of the at least one radio signal.

Further gains can be observed for non-contiguous CC, due to the higher total bandwidth of the aggregated multi-CC signal.

In a possible implementation form of the mobile device, a frequency band for joint processing of the set of pilot symbols of at least two CCs is chosen in a way that at least one CC is located at an edge of the frequency band.

Joint processing as described in this disclosure specifies joint processing with respect to different CCs, i.e. multiple CCs.

Accuracy of localization can be enhanced by distribution of transmit power towards the edges of bandwidth.

In a possible implementation form of the mobile device, the receiver comprises a plurality of single processing chains, each single processing chain associated with a respective CC. This provides the advantage that no architectural changes or additional hardware components are needed at the receiver.

In a possible implementation form of the mobile device, each single processing chain comprises a down-converter configured to down-convert the respective CC to baseband.

This provides the advantage that each CC can be individually processed and optimized. In a possible implementation form of the mobile device, the processor is configured to determine the localization information based on a combination of separate localization estimations per CC. This provides the advantage that the separate localization estimations per CC can be individually processed and optimized.

In a possible implementation form of the mobile device, the receiver comprises at least one joint processing chain, wherein the at least one joint processing chain is associated with at least two CCs.

This provides the advantages that existing pilots in multiple carriers can be jointly used at the receiver side. Due to higher overall bandwidth with pilots at the edges of the occupied bandwidth, CRLB is significantly improved (lower). Using a maximum likelihood (ML)-like detection method which can achieve the CRLB leads consequently to a significantly higher timing estimation.

In a possible implementation form of the mobile device, the at least one joint processing chain comprises a down-converter configured to jointly down-convert the at least two CCs to baseband.

This provides the advantages that a single down-converter instead of multiple down-converters can be implemented resulting in reduced computational complexity. In a possible implementation form of the mobile device, the processor is configured to determine the localization information based on a joint processing with respect to the set of pilot symbols comprised in the at least two CCs.

This provides the advantages that a joint processing with more than one CC can improve the estimation accuracy of the localization information.

In a possible implementation form of the mobile device, the at least one joint processing chain is implemented in time domain having a higher sampling rate than each of a plurality of single processing chains associated with respective CCs; and/or the at least one joint processing chain is implemented in frequency domain considering a larger frequency band than each of a plurality of single processing chains associated with respective CCs. This provides flexibility to implement the processing chain in frequency or time domain. Using the aggregated signal as a single wideband signal instead of a CC signal can increase the timing estimation accuracy by up to a factor of 100, for example. Since m-level (meter-level) accuracy can be obtained with the single CC signal, cm-level (centimeter-level) accuracy can be achieved by using the aggregated signal.

In a possible implementation form of the mobile device, the processor is configured to adjust local replicas of the set of pilot symbols, wherein adjusting the local replicas includes a phase adjustment of the pilot symbols.

Applying such a phase adjustment can increase the accuracy of localization estimation.

In a possible implementation form of the mobile device, the processor is configured to jointly detect the set of pilot symbols and estimate the localization information based on the jointly detected pilot symbols.

Jointly detecting the set of pilot symbols and estimating the localization information based on the jointly detected pilot symbols increases the detection and estimation accuracy. In a possible implementation form of the mobile device, the processor is configured to perform band-pass filtering to suppress signal components between the CCs.

This provides the advantages that signal components between the CCs can be suppressed by the filtering.

In a possible implementation form of the mobile device, the receiver is configured to receive signaling information from a base station, the signaling information indicating the CCs to be considered for joint estimation and related information, in particular their carrier frequency and bandwidth, as well as the (usually pre-defined) structure of the set of pilot symbols per CC, in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC.

This provides the advantage that the mobile device can adjust the receiver based on the signaling information from the base station, i.e. accuracy can be improved.

In a possible implementation form of the mobile device, the receiver is configured to feed back the localization information obtained by separate localization estimations per CC and/or the localization information obtained by joint processing of at least two CCs to at least one radio transceiver.

This provides the advantage that the mobile device can feedback the calculated localization information to the base station which can adjust the timing of the transmission signal to improve overall accuracy of localization computation.

According to a second aspect, the invention relates to a radio transceiver, in particular a base station, comprising: a transmitter, configured to: transmit a radio signal, wherein the radio signal comprises at least one CC, comprising a set of pilot symbols for localization of a mobile device, wherein the CCs are transmitted on different carrier frequencies with respect to each other; and transmit signaling information, the signaling information indicating the CCs to be considered for joint estimation and related information, in particular their carrier frequency and bandwidth, as well as the structure of the set of pilot symbols per CC, in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC; a receiver, configured to receive feedback information from the mobile device, the feedback information comprising localization information determined by the mobile device based on different radio signals and/or different CCs; and a processor, configured to adjust a transmission time of the transmitter for the at least one radio signal and/or the at least one CC, in order to time-align the CCs and/or the radio signals.

Such a radio transceiver may implement the CATE concept according to this disclosure. This means, the radio transceiver can utilize multiple carrier bands to increase the effective bandwidth of the aggregated signal used for localization at the mobile device. Multiple carrier bands sent from the radio transceiver can be combined.

According to a third aspect, the invention relates to a communication system, comprising: a plurality of radio transceivers, in particular base stations configured to transmit a corresponding plurality of radio signals, each radio signal comprising at least one CC, the at least one CC comprising a set of pilot symbols; and a mobile device, configured to receive at least one radio signal of the plurality of radio signals, the at least one radio signal comprising at least two CCs, wherein the mobile device is configured to determine for each of the at least two CCs of the same radio signal or of different radio signals respective localization information, in particular a respective time of arrival, TOA, based on the set of pilot symbols of the at least one CC of the respective radio signal and to feedback the determined localization information to the corresponding radio transceivers. Such a communication system may implement the CATE concept according to this disclosure. This means, the mobile device can utilize multiple carrier bands to increase the effective bandwidth of the aggregated signal used for localization. Multiple carrier bands sent from a single base station can be combined. Such a mobile device can use higher sampling rate to process and/or larger FFT to down-convert multiple carrier band signals. The mobile device can increase the square bandwidth term in denominator of CRLB resulting in a higher accuracy of localization estimation. Direct benefits of CATE are the following: Existing pilots in multiple carriers can be jointly used at the receiver side. Due to higher overall bandwidth with pilots at the edges of the occupied bandwidth, CRLB is significantly improved (lower). Using a maximum likelihood (ML)-like detection method which can achieve the CRLB leads consequently to a significantly higher timing estimation. Besides, no additional hardware components are needed.

In a possible implementation form of the communication system, the mobile device is configured to determine the localization information based on a joint processing of the set of pilot symbols in the at least two CCs transmitted in the at least one radio signal.

In a possible implementation form of the communication system, the corresponding radio transceivers are configured to adjust their transmission times for at least one CC, based on the feedback from the mobile device such that the at least two CCs from the at least one radio signal are time-aligned.

This provides the advantage that by adjusting the transmission time, a more precise estimation of the position of the mobile device can be implemented.

According to a fourth aspect, the invention relates to a method for localizing a position of a mobile device, the method comprising: receiving, by a mobile device, at least one radio signal from a corresponding radio transceiver, in particular a base station, wherein the at least one radio signal comprises at least one CC, comprising a set of pilot symbols for localizing the mobile device; and determining localization information, in particular a time of arrival, TOA, of the at least one radio signal, based on the set of pilot symbols of the at least one CC. Such a method provides an efficient mechanism for localizing the position of a mobile device. In particular, the method improves the accuracy of localization estimation below the centimeter range. Accuracy to centimeter range can be achieved. According to a fifth aspect the invention relates to a computer program product comprising program code for performing the method according to the fourth aspect of the invention, when executed on a computer or a processor.

Embodiments of the invention can be implemented in hardware and/or software.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram of a mobile radio communication system 100 illustrating location measurement based on time-of-arrival (TOA); Fig. 2 shows a schematic diagram illustrating an exemplary Carrier Aggregated Timing Estimation (CATE) transmitter device 200 for contiguous CCs according to the disclosure;

Fig. 3 shows a schematic diagram illustrating an exemplary CATE transmitter device 300 for non-contiguous CCs according to the disclosure;

Fig. 4 shows a schematic diagram illustrating an exemplary CATE receiver device 400 for disjoint carriers according to the disclosure;

Fig. 5 shows a schematic diagram illustrating an exemplary CATE transmitter and receiver system 500 using multiple carrier positioning reference signals according to the disclosure;

Fig. 6 shows a schematic diagram illustrating an exemplary CATE receiver device 600 using multiple carrier bands which are jointly processed as a single composite band according to the disclosure;

Fig. 7 shows a schematic diagram illustrating an exemplary CATE transmitter and receiver system 700 using multiple carrier positioning reference signals according to the disclosure; Fig. 8 shows a performance diagram 800 illustrating exemplary performance of different localization methods; Fig. 9 shows a performance diagram 900 illustrating exemplary performance of the localization methods according to the disclosure when two carriers are used jointly for localization;

Fig. 10 shows a schematic diagram of a mobile radio communication system 1000 with a mobile device 1010 and an exemplary number of three base stations 1020, 1030, 1040 illustrating location measurement according to the disclosure;

Fig. 1 1 shows a schematic diagram illustrating an exemplary CATE receiver device 1 100 with common pilot error correction according to the disclosure; and Fig. 12 shows a schematic diagram illustrating an exemplary CATE receiver device 1200 with pilot adjustment according to the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise. The methods and devices described herein may also be implemented in wireless communication networks based on mobile communication standards such as LTE, in particular 4.5G, 5G and beyond. The methods and devices described herein may also be implemented in wireless communication networks, in particular communication networks based on WiFi communication standards according to IEEE 802.1 1. The described devices may include integrated circuits and/or passives and may be manufactured according to various technologies. For example, the circuits may be designed as logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, optical circuits, memory circuits and/or integrated passives.

The devices described herein may be configured to transmit and/or receive radio signals. Radio signals may be or may include radio frequency signals radiated by a radio transmitting device (or radio transmitter or sender) with a radio frequency in a range of about 3 kHz to 300 GHz. The frequency range may correspond to frequencies of alternating current electrical signals used to produce and detect radio waves.

The devices and systems described herein may include processors, memories and transceivers, i.e. transmitters and/or receivers. In the following description, the term "processor" describes any device that can be utilized for processing specific tasks (or blocks or steps). A processor can be a single processor or a multi-core processor or can include a set of processors or can include means for processing. A processor can process software or firmware or applications etc.

Localization techniques may be based on time of arrival (TOA) and/or time difference of arrival (TDOA), for example. Accuracy of these localization techniques depends on power distribution within signal bandwidth, acquisition time and signal-to-noise ratio (SNR) at the receiver. Accuracy of localization can be enhanced by: Distribution of transmit power towards the edges of bandwidth; higher bandwidth utilization; shorter acquisition times (i.e. less number of measurements needed for a given measurement accuracy, thanks to the increased effective bandwidth); and increased transmit power to achieve higher receiver SNR. Accuracy can further be enhanced by exploiting carrier aggregation as described hereinafter. Different architectures and signal power spectra apply for contiguous carrier component (CC), e.g. as described below with respect to Fig. 2 and non-contiguous CCs, e.g. as described below with respect to Fig. 3. Devices according to the disclosure may apply Carrier Aggregated Timing Estimation (CATE). Two concepts can be implemented: disjoint estimation per CC; and joint estimation for all CCs.

Accuracy can be described by the Cramer-Rao Lower Bound (CRLB). For disjoint estimation using N_cc CCs, the variance of the estimation can be expressed as:

The sum in denominator of above equation indicates that more CCs can increase estimator accuracy. For joint estimation for all CC, the variance of the estimation can be expressed as:

The additional gain from joint estimation comes from the factor k

In the following sections, the concept of CATE and joint estimation is described which forms the basis for the implementation forms described below with respect to Figures 2 to 12.

It is shown that Cramer-Rao Lower Band (CRLB) for TOA (Time Of Arrival) estimation in strictly dependent on the Signal bandwidth. In LTE-Advanced aggregation of several carrier bands is allowed. Independent time delay estimation of two carrier bands, provide 3 dB gain over the estimation of single carrier band. Joint estimation of delay can provide much bigger gain compare to former one. The gain of joint delay estimation in case of aggregated carriers is described in the following.

The time domain transmitted n-th sample basebase OFDM symbol can be expressed as:

x_; (n) , n e [-G, N - l], l e [0, N_sym - l] (1 )

where G is the length of cyclic prefix (CP), N is the size of FFT, and N_sym is the number of OFDM symbols.

If we denote the channel impulse response of the multipath channel as /i; (0),^■■■ , hi (L - 1), then the received signal y_; (n) can be expressed as

L-l

yii nT_s) = ^ h_s(i)x_s( n - i)T_s - T_;) + Μ _; (ηΓ₅)

ί=ο

n e [-G, N + L + T - 1] (2) where z_t is the propagation delay of the signal in the i-th path, and w_; (n) ~ CN(0, σ²) is the additive complex Gaussian noise. Note that the channel taps are not necessarily a multiple of symbol duration. The received signal (vector) has complex Gaussian distribution, that is γ~βΝ(μ, Cyy); where μ and C_yy are mean vector and covariance matrix of the received signal y, respectively. For OFDM, the signal X](t) can be separated into pilot part sj(t) and data part di( as xi (t) = s_I(t) + d_I( -

In the following, CRLB of single carrier component transmission is described.

To estimate TOA, maximum likelihood estimator can result in optimal result. Using the likelihood function between received signal and the reference signals; The beginning of the received signal can be detected and used for TOA estimation. For single carrier component the likelihood function can be simply written as probability of the additive noise. The likelihood function in presence of additive white Guassian noise is

1

p(y|r) = exp[- y - μ)^Η ' y y - μ)]

n)^Ndet C_yy)

(3)

For a static AWGN channel, h_t (0) = 1 and h_t (i) = 0 for i≠ 0,

yi ( iT_s) = Xi (nT_s - τ) + w_l (nT_s). (4)

Mean and covariance of the received signal for this case are

Hs(nT_s) = E{yi (nT_s)} = E{xi (nT_s - τ) + wi (nT_s)}

= Xi (nT_s - τ),

Cyy = E{(y - μ) γ - μ)^Η] = E{ww^H)} = σ²Ι where w is the noise vector and J is the identity matriy. The likelihood function simplifies to

A baseband OFDM symbol xi (nT_s - τ) can be written as N/2-1

_Xl(nT_s - τ = 1 /N > X^e 2nkAf(nT_s-r)

k=-N/2 (6) where Af = 1/(NT_S), is the subcarrier spacing, and ^/c) is the signal allocated on the/c-th subcarrier of the Z-th OFDM symbol. Since only reference subcarriers are used in ML estimation, we assume Xi(k_d) = 0 for k_d being the non-reference subcarriers indices. Therefore, d_;(t) = 0 and x_;(t) = s_;(t). we replace x_;(t) with s_;(t) to emphasis on the pilot signal, similarly we have

(7)

The Fisher Information (Fl) for this system is derived as

Nsym^~ 1 iV— 1

² V V dsxinTs-τ)

^F1^ = ² Σ Σ δτ

1=0 n=0 (8)

and

1

var(f) > CRLB =

? τ) (9)

We can obtain the Fl from (8) with replacing si(nT_s— τ) with (7) according to W. Xu et al, "Maximum likelihood TOA and OTDOA estiamtion with first arriving path detection for 3GPP LTE system," 2014.

r sym— 1

8π²Δ ²

σ² -Ν

1=0 k m

N-l

gj2nAf(m-k)T _gj2nAf (k-m)nT_s

n=0

^~-NS_mk (10) where S_mk is the Kronecker delta function defined as

m^~ 0 otherwise (11)

Therefore the Cramer-Rao bound for the variance of delay estimation equals to

In the following, CLRB of multiple carrier components is described.

The results from last section suggests that the Cramer-Rao bound is a function of the bandwidth of OFDM signal. In LTE advanced one cell can serve a User Equipment (UE) with several carrier components; which are not necessarily adjacent channels. In the presence of Line Of Sight (LOS), different carrier bands are prone to the same delay in the LOS communication. In this section we investigate the analytic lower bound for the delay estimation in the present of multiple carrier components. Baseband equivalent signal model and Cramer- rao Lower Bound of different receiver architecture are described below.

For independent receiver in each carrier components, CRLB is

σ²

var( )≥

8π ΑΡ∑¾ ∑¾^m∑^N _ki²_-_N)₂ fc . |_Si,_c (/t) | 2 (13) where k is the subcarrier indice, c is the carrier component indice, and I is the symbol indice. In caparison to the single carrier component, it provides 101og( _cc) dB gain, while the other architecture, Single down conversion provides much higher gain, which depends on the frequency spacing between carrier components.

the following, maximum likelihood estimation is described.

It is well known that, the ML delay estimator is asymptotically the minimum variance unbiased for static channel, for a single carrier transmission. Therefore, The likelihood function has a peak maximum at propagation delay, τ₀ = τ₀. In this section we will show that the ML estimator is unbiased for the multi carrier components transmission, if the channel is AWGN. Consider the received signal y(t) = h₀x(t - T₀) + w(t) (15)

For OFDM, the signal x(i) can be separated into pilot part s(c) and data part d(i) as x(i) = s(c) + d(i) . Assuming they are uncorrelated pseudo noise sequences, and fulfill E{d(t)s*(t)} = 0, and E{w(t)s*(t - τ)) = 0. The cross-correlation becomes ff (τ) = E{y(t)s*(t - T)} = E{h₀s(t - T₀)s*(t - T)}

= oRo( ^{~ T}o) (1g) where ϋ₀(τ— τ₀) defined as R₀( — τ₀) =: E{s(t— T₀)S*(£ - τ)) , using Cauchy-Schwarz inequality it can be proven than R₀( )≤ R_o( ), hence, f₀ = argmax R( ) = argmax R₀( —

τ τ τ₀), is a unbiased estimation, and £^"{τ₀) = τ₀.

For multi carrier components, y(t) =∑^ y_c( - by denoting ff₀,c(^T) =-E{s_c(t)s*(t - τ)), and R_c( ) =: E{y_c(t)s_c*(t - τ)), we have

With respect to cross-correlation for independent receiver in each carrier band, the following holds: model for the received signal in case of static channel, we have

y_c t) = h_c(0)x(t - τ) + w_c(i) (18) and therefore, R_c r) =

^{~ τ}ο ·

Since R_0IC = l,---,N_cc , we have

and τ = argmax β(τ) is unbiased.

τ

With respect to cross-correlation for single down-conversion, the following holds:

The model for static channel is

y_C( = ho_iCx t - T₀) ·

+ _Wc(_t) . _ej2nAf_ct

(20) we construct the cross-correlation as

= E{h_0iC X_c{t - T₀) · S*(t - T) ·

+E{w_c (t) · s* (t - T) · β'^{2πΑ τ}} (21 )

Since noise w_c(t), and pilot signal s_c(t) are uncorrelated £^"{w_c(t) · s*(t - τ) · _β^^2πΑ^^τ} = 0 we have

ff _C (T) = μ_0ι€ E{s_c (t - To) · s* (t - T)} · _eV2

= /¼c ff₀,c(T - To) -e^J'27rA ^-^T") To make sure that the estimator is unbiased we need to show that R_c( ) has a maximum at τ₀. This can be proven using Couchy-Schwarz inequality

N-l

I s_c (ηΓ,) · s_c* (nr_s - (τ - τ₀)) ·

n=0

N-l N-l

≤ \s_c(nT_s - T₀) I² · \s_c(nT_s - τ) · _e^A

(22)

when the delay τ₀ and τ are smaller than cyclic prefix length E{s_c(nT_s— τ₀) · s*(nT_s— τ₀)) = f?o,_c(0) and E{s_c(nT_s - τ) · s*(nT_s - τ)} = ff₀,c(°)_> therefore,

I— ff_c(T)|² < ff₀,c(0)²

o,c (23) by taking the square root from both sides we have

Iffc I < cffo,c(0)| (24)

and we have R( ) =∑_c R_c( ), therefore f₀ = argmax R( ), is unbiased, Ε{τ₀] = τ₀.

In the following, a baseband equivalent is described.

In general, the received signal in the receiver is the super position of different carrier components, for one symbol we have

where a¾_c(t) is the Z-th transmit symbol in the c-th carrier components, and h_lc( ;t) is the multipath channel affecting the Z-th symbol in the c-th transmission carrier band. Assuming each hi c r; t) consists of I multipath components, then we can rewrite (25) yi (nT_s) =

Here we investigate the baseband equivalent model for different receiver structure. For independent receivers for each carrier band, the following holds:

Figure 5 described below shows the architecture of the conventional receivers, each carrier components is down-converted separately and used for estimation independently. To derive the Cramer-Rao bound of the delay estimation, first we require to model the equivalent baseband of the system.

For the sake of simplicity we drop the subscript I from (26), and derive the baseband equivalent model for one symbol, but it can be generalized for several symbols.

We assume N_cc carrier components are simultaneously transmitted, where subscript c = 1, . . , N_cc corresponds to the c-th carrier component.

We can derive the baseband equivalent of the system by replacing the transmit signal x_c(t) with Λ/2 Re{x_{b c}(t) ^■ ei²⁷¹^} and the received signal y(t) with∑¾ 2 Re{y_{b c} ^■ e'²⁷¹^*} in (26), where x_biC(t) is the baseband signal of the c-th carrier components, and it is up-converted with f_Cc. And y_b<c is complex baseband received signal in the c-th carrier component. It can be written as y[2Re{y_biC(nT_s) ^■ e^_c

=

+

=

• β>^{2πί ηΤ}*} + V2i?e{w_c(nr_s) · _β>^2π^^ηΤ*} (27)

Similarly, one can obtain Im{y_b>c nT_s)■ β ^π^_}

L- l

= /m{( h_c(i)x_biC{(n - i)T_s - · ^π/^+τ+ί))

i = 0

• e^j27lfcc^nTs } + Im{w_c(nT_s)■ _e ^j27lfcc^nTs} (28) where Re{-} and Im{-} are representing the real part and imaginary part of the signal, and w_c(nT_s is baseband equivalent of the noise. Hence, the baseband equivalent model of the transmission is

L- l

(nT_s = ^■ Xb,c .(n - ^Ts - Ti) + w_c(nT_s)

i = 0 (29) where h_c i) is the base band equivalent of the channel and it equals to

For static AWGN channel, h_c(0) = 1 and h_c(i) = 0, for i≠ 0 and c = 1,2,— , N_CC, (29) is written as

Vb.c ( iT_s) = x_b>c (nT_s - T₀) + w_c (nT_s) (31 ) and the likelihood function as

Since the white Gaussian noise added to each carrier components is independent to the noise of the other carrier components we have

Ncc

Ρθ|τ) = P (J¾_C |T)

I (33)

and the Fisher information equals to

NNcccc NN-l

² V V d^xb,c (^nTs - ^T) 2

c=i n=o ^^T (34)

Considering only the reference signal, we replace the signal x_b,_c(t) with the pilot signal s_{b c}(t) . Using OFDM signal representation (7), we can calculate Cramer-Rao bound for this receiver architecture as

σ²

var(f) > 77- .

8^^_∑¾ _∑J/2_-i_{2 fc}2. |5_c(A:)|2 ₍₃₆₎

For single down-conversion to baseband the following holds:

Figure 7 described below represents the architect of a receiver with single down conversion, this model requires a largerfft in the receiver side and therefore higher sampling rate. To derive the equivalent baseband model we start with (26), and substitute x_c(t) with 2 Re{x_bc(i)^■ _ej2nf_Cct^ _{and the rece}j_vec| signal y t) with ^flRe{y_b■ e^i2nf^ in (26). Where x_biC t) is the baseband signal of the c-th carrier components, and it is up-converted with f_Cc, and y_b is complex baseband received signal, and f_Co is the frequency of the down conversion. Consequently, the equivalent baseband signal can be written as

^Re{y_b(nT_s)^■ _e ^j27tfco^nTs}

Ncc L-1

= ^ ^ h_c(i)^■ V2 · Re{x_{b c}( n

c=l i=0

Ncc L-1

V2ffe{^ h_c(t)x_biC((n

c=l i=0

. _e-j2nfc₀(iT_s+Ti) . _ej2n&fc((n-i)T_s- _l)^ . _ej2nf_CQ (nT_s) j

which is similar to it's imaginary part, and Af_c = f_Cc— f_Co. Therefore received the equivalent baseband signal is

L-1

y_b,c(nT_s) = ii)^■ ¾_,c((n - - TJ) · _e^A/_e((n-Qr_s-_T)

i=o

+w_c(nT_s)^■ e^{j27l f}c^nTs (38) and

Ncc

V_b(nT_s = y_b>c

(39) where w_c(nT_s) is the baseband equivalent of the noise added to the c-th carrier component, and h_c(i) is the base band equivalent of the c-th carrier component channel and it equals to

¾_c( = ( ^■ e-^i2nfco(^iTs^+T (40) For static AWGN channel, h_c 0) = 1 and h_c(i) = 0 , for i≠ 0 and c = 1,2,— , N_CC , (38) is written as y_b,c{nTs) = {x_b,c{nTs - TO) · e^~'²ⁿ^ + w_c{nT_s)) ^■ _Β^Λ/_ε(^η _¾

The likelihood function equals to p (yb,c \ ^T~) =

-x_b>c(nT_s - T) · e>²ⁿ^{nT

We replace the transmit signal x_biC(t) with its pilots part s_{b c}(i) , assuming the data part d_{b c}(i) = 0. Therefore, we can write the Fisher information as

where Af is the subcarrier spacing. Therefore, the CRLB equals to

σ²

var( )≤

8^²Δ/² Σ¾∑ΐ₌ ²:_Ν)₂ (k -^Y\S_c(k) \²

(44)

Fig. 2 shows a schematic diagram illustrating an exemplary Carrier Aggregated Timing Estimation (CATE) transmitter device 200 for contiguous CCs according to the disclosure. The baseband signal 210 which is provided to the transmitter device 200 includes two contiguous component carriers (CCs) 21 1 , 212 as can be seen from the spectrum. The CATE transmitter device 200 includes a multiplex stage 210 for multiplexing the baseband signal 210, an I FFT (inverse Fast Fourier transform) stage 202 for transforming the baseband signal 210 to time domain, a digital-to-analog (D/A) converter 203 for providing the continuous-time signal, a multiplier 204 for multiplying the continuous-time signal with a factor L, 205 (e.g. indicating a frequency band for transmission) and a radio frequency (RF) power amplifier (PA) 206 and an RF filter 207. The baseband signal 210 having passed these stages is provided at an antenna port 208 for radio transmission. Fig. 3 shows a schematic diagram illustrating an exemplary CATE transmitter device 300 for non-contiguous CCs according to the disclosure.

The signal 330 to be transmitted at antenna port 319 includes a first CC 331 located around first carrier frequency fc1 , 333 and a second CC 334 located around second carrier frequency fc2, 334. This signal 330 is generated from a first baseband signal X1 (f) and a second baseband signal X2(f) by passing through the CATE transmitter device 300.

The transmitter device 300 includes two signal paths. A first signal path includes a first multiplex stage 31 1 applied to the first baseband signal X1 (f), a first IFFT stage 312, a first D/A converter 313 and a first multiplier for multiplying the first baseband signal X1 (f) processed by these stages 31 1 , 312, 313 with the first carrier frequency L1 , 315 to generate the first carrier component 331 . A second signal path includes a second multiplex stage 321 applied to the second baseband signal X2(f), a second IFFT stage 322, a second D/A converter 323 and a second multiplier 324 for multiplying the second baseband signal X2(f) processed by these stages 321 , 322, 323 with the second carrier frequency L2, 325 to generate the second carrier component 332. An adder 316 adds both carrier components 331 , 332 to a common signal which is passed through a radio frequency (RF) power amplifier (PA) 317 and an RF filter 318 before being transmitted by transmit antenna port 319.

Fig. 4 shows a schematic diagram illustrating an exemplary CATE receiver device 400 for disjoint carriers according to the disclosure.

Fig. 4 shows the principle of the CATE for disjoint multiple carriers. Here, a received signal 410 with two or more carrier bands 401 , 402, which include localization reference signals, is received by a UE. The first carrier band, also referred to as first component carrier, CC1 , 401 has a bandwidth BW1 , 405 and is located around the first carrier frequency fc1 , 403. The Ncc- th carrier band, also referred to as Ncc-th component carrier, 402 has a bandwidth BW_Ncc, 405 and is located around the Ncc-th carrier frequency fc_Ncc, 404. The first component carrier, CC1 , 401 may e.g. correspond to the first component carrier, CC1 , 331 described above with respect to Fig. 3. The Ncc-th component carrier, 402 may e.g. correspond to the second component carrier, CC2, 332 described above with respect to Fig. 3. The CATE receiver device 400 may for example receive the signal 330 transmitted by the CATE transmitter device 300 shown in Fig. 3.

The UE receives and down-converts each carrier band 401 , 402 separately by the receiver down-conversion stage 420, which includes a plurality of low pass filter and down-conversion stages 422, 423, and applies disjoint location estimation in the baseband. The received baseband signals 430 with component carriers 401 , 402 transformed to baseband are depicted on the right side of Fig. 4. In general, the estimation can be performed in the time or frequency domain. The estimates from different bands 401 , 402 can be combined to increase the overall accuracy. This is similar to the localization procedure a legacy LTE UE would potentially perform when receiving multiple carrier signals. Fig. 5 shows a schematic diagram illustrating an exemplary CATE transmitter and receiver system 500 using multiple carrier positioning reference signals according to the disclosure.

The system 500 is configured for multi-CC transmission, where the transmitter 510 includes multiple transmitter stages 51 1 , 512 providing the individual signal components which are added 519 to a composite signal y(t) for transmission. In the receiver 520, each CC has its separate receiver chain 521 , 522.

Each transmitter stage, for example transmitter stage 512, includes two multipliers 513, 515 and an adding unit 516 for mixing the in-phase signal component and the quadrature signal component of the input signal, wherein the quadrature signal component is shifted by a phase shift 514 of π/2, with the carrier frequency fc_Ncc and adding both frequency shifted signal components to a component carrier signal x_Ncc(t) which is passed through a filter h_Ncc(x,t) 517. A weight component w_Ncc(t) is added to the output of the filter 517 to form the individual signal component of the transmitter stage 512.

Each receiver stage, for example receiver stage 522, includes two multipliers 523, 525 for mixing the received signal y(t) with the carrier frequency fc_Ncc or the carrier frequency shifted 524 by π/2, respectively to obtain in-phase and quadrature components, respectively. Both, in-phase and quadrature components, are passed through a respective low pass filter (LPF) 526, 527 to generate the signal components of the various component carrier components received at the receiver 520. This processing at the receiver 520 corresponds to a down- conversion and low pass filtering.

I.e., at the receiver 520, CC signals are down-converted and positioning estimation is performed separately per CC. Cross-correlation with local replicas of pilots can be used to identify sequences and to estimate the TOA. Estimation and compensation of common phase difference between CCs may be needed, e.g. as described below with respect to Fig. 1 1 . Usage of different LOs may lead to different frequency offsets between the CCs. In this receiver structure 520, no architectural changes or additional hardware components are required.

Fig. 6 shows a schematic diagram illustrating an exemplary CATE receiver device 600 using multiple carrier bands which are jointly processed as a single composite band according to the disclosure.

Multiple carrier signals, which are transmitted in a time-synchronized way are received and are jointly down-converted as a single composite band with a significant larger bandwidth, as shown in Fig. 6. Estimation is then performed based on the composite signal either in the time domain, after the signal has been oversampled with the required sampling rate, or in the frequency domain, after utilizing a correspondingly larger FFT. Either for time or frequency domain estimation, the disclosed CATE concept increases the mean square bandwidth of the signal, which represents the distribution of the power on frequency spectrum, and hence, increases the accuracy of the localization estimation.

Fig. 6 shows the principle of the CATE using joint multiple carrier positioning reference signals for joint multiple carriers. Here, a received signal 610 with two or more carrier bands 401 , 402, which include localization reference signals, and which may correspond to the received signal 410 as described above with respect to Fig. 4 is received by a UE. The first carrier band, also referred to as first component carrier, CC1 , 401 has a bandwidth BW1 , 405 and is located around the first carrier frequency fc1 , 403. The Ncc-th carrier band, also referred to as Ncc-th component carrier, 402 has a bandwidth BW_Ncc, 405 and is located around the Ncc-th carrier frequency fc_Ncc, 404. The first component carrier, CC1 , 401 may e.g. correspond to the first component carrier, CC1 , 331 described above with respect to Fig. 3. The Ncc-th component carrier, 402 may e.g. correspond to the second component carrier, CC2, 332 described above with respect to Fig. 3. The CATE receiver device 600 may for example receive the signal 330 transmitted by the CATE transmitter device 300 shown in Fig. 3. The UE receives and jointly down-converts each carrier band 401 , 402 by the common receiver down-conversion stage 620, and applies joint location estimation in the baseband. The received baseband signal 630 with component carriers 401 , 402 transformed to baseband are depicted on the right side of Fig. 6.

In general, the estimation can be performed in the time or frequency domain. The common processing of different bands 401 , 402 increase the overall accuracy. Fig. 7 shows a schematic diagram illustrating an exemplary CATE transmitter and receiver system 700 using multiple carrier positioning reference signals according to the disclosure. Fig. 7 shows the transmitter and receiver architecture of the CATE using joint multiple carrier positioning reference signals.

The system 700 is configured for multi-CC transmission, where the transmitter 710 includes multiple transmitter stages 51 1 , 512 providing the individual signal components which are added 519 to a composite signal y(t) for transmission. In the receiver 520, the CCs are processed by a common receiver chain 720.

The transmitter 710 may correspond to the transmitter 510 described above with respect to Fig. 5. The common receiver chain 720 may correspond to any of the receiver stages, for example receiver stage 522, as described above with respect to Fig. 5. However, a common carrier frequency fc_0 is applied for the mixing, i.e. down-conversion, of the received signal y(t) to baseband.

In particular, at the receiver 720, a multi-CC signal is down-converted to baseband. This may require the following signal processing: A local oscillator (LO) with adjusted carrier frequency, or an adjustment of the existing LO frequency. Higher sampling rate may be required according to the bandwidth (BW) and a larger FFT for transformation into frequency domain. Pass-band filtering of signal components between CCs may be required to avoid interference. Joint estimation based on the pilots in all CCs may be performed. Phase adjustment may be applied to pilots due to frequency shift. Cross-correlation can then performed with a local replica of the full pilot set including all CCs to identify sequences and estimate TOA. Estimation/compensation of common phase difference between CCs is recommended, if different LOs are used at the transmit side for different CCs. An exemplary implementation of common phase estimation/compensation is described below with respect to Fig. 1 1. Time synchronization (of known time offsets) between multiple CC transmission may be needed. Fig. 8 shows a performance diagram 800 illustrating exemplary performance of different localization methods. First solid line 801 describes the scenario of single CC; second solid line 802 describesl the scenario of double CC disjoint estimation; third solid line 803 describes the scenario of double CC joint estimation with single down converter (d.c). First dashed line 81 1 describes the CLRB for single CC; second dashed line 812 describes the CLRB for double CC disjoint estimation (dis. est.); third dashed line 813 describes the CLRB for double CC joint estimation with single d.c. In Fig. 8, both methods are shown and the performance gain of joint estimation method is depicted. As an example, two carrier bands are used for estimation. The first dashed line 81 1 is a single carrier positioning reference signal Cramer-Rao lower bound (CRLB), whereas the first solid line 801 is the variance of the estimation error using the maximum-likelihood based methods, e.g. as described by W. Xu, M. Huang, C. Zhu and A. Dammann, "Maximum likelihood TOA and OTDOA estimation with first arriving path detection for 3GPP LTE system," Transactions on Emerging Telecommunications Technologies (ETT), 2014, which is obtained through Monte Carlo simulations. The second solid line 802 shows the error variance in location estimation with two disjoint carrier bands, revealing a gain of around 2-3 dB compared to single-carrier estimation. Fig. 8 shows that to achieve 3 meters accuracy, using single carrier band, required SNR is about 13dB. While the disjoint carrier bands, as shown by lines 803, 813, can achieve the same level accuracy at approximately 10dB. It is worth mentioning that the CRLB is defined without any respect to the user position. In a normal system an additional factor will be added to the error due to the Delusion of the precision (DOP). That is, the actual UE location error variance is the calculated CRLB times DOP for the given location. For instance user at the center of three eNodeBs has lowest DOP.

Fig. 8 further shows the benefit of the disclosed approach over single and multiple disjoint localization methods. The third solid line 803 represents the performance of joint estimation method, when two carrier bands are separated with a 500kHz spacing. The 3 meter level of accuracy can be now achieved with -2dB, which is 15dB lower than for single carrier and 12dB lower than for two disjoint carriers. The gain can be improved further when the carrier bands are further apart. Fig. 9 shows a performance diagram 900 illustrating exemplary performance of the localization methods according to the disclosure when two carriers are used jointly for localization. First solid line 901 describes the scenario of two CC, 2MHz spacing; second solid line 902 describes the scenario of two CCs, 500KHz spacing; third solid line 903 describes the scenario of single CC.

Fig. 9 shows measurements when two carriers are used jointly for localization. As spacing between two carriers increases, the CRLB decreases as well and estimation improves. The CRLB can be achieved, e.g. by using the maximum-likelihood based methods, e.g. as described by W. Xu, M. Huang, C. Zhu and A. Dammann, "Maximum likelihood TOA and OTDOA estimation with first arriving path detection for 3GPP LTE system," Transactions on Emerging Telecommunications Technologies (ETT), 2014. Fig. 10 shows a schematic diagram of a mobile radio communication system 1000 with a mobile device 1010 and an exemplary number of three base stations 1020, 103, 1040 illustrating location measurement according to the disclosure. The mobile radio communication system 1000 includes a plurality of radio transceivers 1020, 1030, 1040, in particular base stations BS1 , BS2, BS3 configured to transmit a corresponding plurality of radio signals 1025, 1035, 1045. Each radio signal 1025, 1035, 1045 comprises at least one carrier component, CC 401 , 402. The at least one CC 401 , 402 comprises a set of pilot symbols. The system 100 further includes a mobile device 1010 which is configured to receive at least one radio signal 1025 of the plurality of radio signals 1025, 1035, 1045. This radio signal 1025 comprises at least two carrier components, CCs 401 , 402. The mobile device 1010 is configured to determine for each of the at least two CCs 401 , 402 of the same radio signal 1025 or of different radio signals 1025, 1035, 1045 respective localization information 1013, in particular a respective time of arrival, TOA, based on the set of pilot symbols of the at least one CC 401 , 402 of the respective radio signal 1025, 1035, 1045 and to feedback the determined localization information 1013 to the corresponding radio transceivers 1020, 1030, 1040.

The mobile device 1010 may be configured to determine the localization information 1013 based on a joint processing of the set of pilot symbols in the at least two CCs 401 , 402 transmitted in the at least one radio signal 1025, e.g. a joint processing of the CCs 401 , 403 as described above with respect to Figures 6 and 7.

The corresponding radio transceivers 1020, 1030, 1040 may be configured to adjust their transmission times for at least one CC 401 , 402, based on the feedback from the mobile device 1010 such that the at least two CCs 401 , 402 from the at least one radio signal 1025 are time- aligned.

Each of the radio transceivers 1020, 1030, 1040 which may be implemented as base stations, includes a transmitter 1022, a receiver 1023 and a processor 1021 as shown in Fig. 10.

The transmitter 1022 is configured to transmit a radio signal 1025, wherein the radio signal 1025 comprises at least one carrier component, CC 401 , 402, e.g. as described above with respect to Fig. 4, comprising a set of pilot symbols for localization of a mobile device 1010. The CCs 401 , 402 are transmitted on different carrier frequencies 403, 404 with respect to each other. The transmitter 1022 is further configured to transmit signaling information which indicates the CCs 401 , 402 to be considered for joint estimation and related information, in particular their carrier frequency 403, 404 and bandwidth 405, 406, e.g. as depicted in Figs. 4 and 6, as well as the structure of the set of pilot symbols per CC, in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC 401 , 402. The receiver 1023 is configured to receive feedback information from the mobile device 1010. The feedback information comprises localization information 1013 determined by the mobile device 1010 based on different radio signals 1025, 1035, 1045 and/or different CCs 401 , 402.

The processor 1021 is configured to adjust a transmission time of the transmitter 1022 for the at least one radio signal 1025 and/or the at least one CC 401 , 402, in order to time-align the CCs 401 , 402 and/or the radio signals 1025, 1035, 1045.

The mobile radio communication system 1000 may include one or more mobile device, e.g. UEs, as described in the following. These mobile devices 1010 may communicate with each other or with base stations 1020, 103, 1040 for providing localization information. Such mobile device 1010 includes a receiver 101 1 and a processor 1012.

The receiver 101 1 is configured to receive at least one radio signal 1025, 1035, 1045 from a corresponding radio transceiver, e.g. a base station 1020, 1030, 1040. The at least one radio signal comprises at least one CC 401 , 402, e.g. as described above with respect to Figures 2 to 7, comprising a set of pilot symbols for localizing the mobile device 1010.

The processor 1012 is configured to determine localization information 1013, in particular a time of arrival, TOA, of the at least one radio signal 1025, 1035, 1045, based on the set of pilot symbols of the at least one CC 401 , 402. TOA may be determined as described above with respect to Fig. 1.

At least two CCs 331 , 332 of the same radio signal 1025 or of different radio signals 1025, 1035, 1045 may be transmitted on different carrier frequencies 333, 334 with respect to each other, e.g. different CCs 331 , 332 and carrier frequencies 333, 334 according to the description above with respect to Fig. 3.

The processor 1012 may be configured to determine the localization information 1013 based on a joint processing of the set of pilot symbols of at least two CCs 331 , 332, e.g. joint processing as described above with respect to Figures 6 and 7. At least two CCs 21 1 , 212 may be contiguously arranged within a frequency band 210 of the at least one radio signal 1025, e.g. as described above with respect to Figure 2. Alternatively, at least two CCs 331 , 332 may be non-contiguously arranged within a frequency band 330 of the at least one radio signal 1025, e.g. as described above with respect to Figure 3.

A frequency band 330 for joint processing of the set of pilot symbols of at least two CCs 331 , 332 may be chosen in a way that at least one CC 332 is located at an edge of the frequency band 330, e.g. as described above with respect to Figure 3. The receiver 101 1 , 400, 520 may include a plurality of single processing chains 521 , 522, e.g. as described above with respect to Figure 5. Each single processing chain 521 , 522 may be associated with a respective CC 401 , 402, e.g. as described above with respect to Figures 4 and 5. Each single processing chain 521 , 522 may comprise a down-converter 422, 423 configured to down-convert 420 the respective CC 401 , 402 to baseband 430, e.g. as described above with respect to Figures 4 and 5.

The processor 1012 may be configured to determine the localization information 1013 based on a combination of separate localization estimations per CC 401 , 402. The receiver 101 1 may include at least one joint processing chain 720, e.g. as described above with respect to Figures 6 and 7. The at least one joint processing chain 720 may be associated with at least two CCs 401 , 402. The at least one joint processing chain 720 may comprise a down-converter 622 configured to jointly down-convert 620 the at least two CCs 401 , 402 to baseband 630, e.g. as described above with respect to Figures 6 and 7. The processor 1012 may be configured to determine the localization information 1013 based on a joint processing with respect to the set of pilot symbols comprised in the at least two CCs 401 , 402. The at least one joint processing chain 720 may be implemented in time domain having a higher sampling rate than each of a plurality of single processing chains associated with respective CCs 401 , 402 and/or in frequency domain considering a larger frequency band than each of a plurality of single processing chains associated with respective CCs 401 , 402.

The processor 1012 may be configured to adjust local replicas of the set of pilot symbols, e.g. as described below with respect to Figure 12. Adjusting the local replicas may include a phase adjustment of the pilot symbols.

The processor 1012 may be configured to jointly detect the set of pilot symbols and estimate the localization information 1013 based on the jointly detected pilot symbols. The processor 1012 may be configured to perform band-pass filtering to suppress signal components between the CCs 401 , 402.

The receiver 101 1 may be configured to receive signaling information from a base station 1020, 1030, 1040. The signaling information indicate the CCs 401 , 402 to be considered for joint estimation and related information, in particular their carrier frequency 403, 404 and bandwidth 405, 406, as well as the structure of the set of pilot symbols per CC 401 , 402, in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC 401 , 402. The receiver 101 1 may be configured to feed back the localization information 1013 obtained by separate localization estimations per CC 401 , 402 and/or the localization information 1013 obtained by joint processing of at least two CCs 401 , 402 to at least one radio transceiver 1020, 1030, 1040.

The UE 1010 may have a transmitter (not shown in Fig. 10) for transmitting the signaling information in a feedback channel. Further signaling information from the BS 1020, 1030, 1040 may be transmitted in a signaling channel, as described in the following.

The UE 1010 needs to be informed, or it can blindly detect, about which carriers to consider for localization. It is not straightforward that all of (or only some of) the carriers including data for the particular receiver shall be considered for localization by this user. Some bands/carriers may be non-synchronized and thus not suitable for joint estimation. Alternatively, the receiver shall take advantage also of pilots in other carriers than the ones containing own data. For example, carriers sent from a different sector, but the same base station location can be considered. The receiver should be further informed about the pilot scheme used in each carrier (e.g. via a pilot scheme index), i.e. pilot symbols and their allocation in time/frequency/antenna. Based on this information, the receiver can locally generate the exact phase-modified pilot sequences to be used for detection of incoming signals. Two possible allocation concepts of the information are described in the following. A first allocation concept is carrier-based signaling. Information is transmitted in every carrier separately, including: instruction whether the particular carrier shall be used for localization; and the pilot scheme used in the particular carrier, e.g. via a pilot scheme index, informing about pilot symbols and their allocations in time/frequency/antenna. A second allocation concept is centralized signaling in the main carrier. Information regarding localization is sent in the main carrier, including: carrier indices; carrier frequency and bandwidth; and pilot scheme used in particular carrier, e.g. via a pilot scheme index, informing about pilot symbols and their allocation in time/frequency/antenna.

Carrier-based signaling is convenient if only (a subset of) carriers containing data for the UE shall be used for localization. For these carriers the UE will anyway access/read the control channel. Carrier-based signaling is also convenient when carriers without data for the UE can/shall be used for localization. By reading the control channel of the main carrier, the UE can be informed about the carriers to be used and directly access the pilots accordingly. Disjoint estimation per carrier requires estimating the common phase difference between different carriers and to compensate this. However, joint estimation requires synchronization between carriers. Down-conversion of the overall signal applies with an adjusted carrier frequency so that the overall multiple-carrier signal is symmetrically moved to baseband. Moreover, pilot modification may be needed: according to the difference between the carrier's radio frequency and the frequency used for down-conversion, the phase of the pilot symbols has to be adjusted accordingly, e.g. as described below with respect to Figs. 1 1 and 12. Joint estimation will then use the locally generated copy of the adjusted pilot symbols at the receiver.

Fig. 1 1 shows a schematic diagram illustrating an exemplary CATE receiver device 1 100 with common pilot error correction according to the disclosure. The figure illustrates estimation per CC using predefined pilots. Common phase difference is estimated and compensated.

The radio signal received from antenna port 1 101 passes an RF filter 1 102. In this exemplary implementation, the output signal of RF filter 1 102 is divided to two signal paths. In the upper signal path, the RF output signal is multiplied 1 104 with a first carrier frequency fc1 , 1 103 and passed to a first low pass filter (LPF) 1 1 13. In the lower signal path, the RF output signal is multiplied 1 106 with a second carrier frequency fc2, 1 105 and passed to a second low pass filter (LPF) 1 1 14. Both carrier frequencies fc1 , fc2, 1 103, 1 104 may correspond to the carrier frequencies fc1 , fc2, 333, 334 depicted in Fig. 3 or to the carrier frequencies fc1 , fcNcc, 403, 404 depicted in Figs. 4 and 6. A first cross-correlation stage 1 1 15 cross-correlates the output of the first LPF 1 1 13 with the first pilot sequence 1 1 1 1 which may be generated by the receiver device 1 100. A second cross-correlation stage 1 1 16 cross-correlates the output of the second LPF 1 1 14 with the second pilot sequence 1 1 12 which may be generated by the receiver device 1 100. A common phase difference estimator 1 1 17 estimates a common phase difference based on the output signals of first LPF 1 1 13 and second LPF 1 1 14. A common phase error correction stage 1 121 , that may be implemented as a multiplier, corrects common phase error based on the output of the common phase difference estimator 1 1 17, the output of the second cross-correlation stage 1 1 16 and a carrier adjustment frequency Afc, 1 120. The carrier adjustment frequency Afc, 1 120 is the difference of second carrier frequency fc2, 1 105 and first carrier frequency fc1 , 1 103. The output signal of the common phase error correction stage 1 121 is added 1 122 to the output of the first cross-correlation stage 1 1 15 and passed to the peak detector which detects a peak 1 124 in the cross-correlation signal shape to detect the localization information in the received signal from antenna 1 101.

Fig. 12 shows a schematic diagram illustrating an exemplary CATE receiver device 1200 with pilot adjustment according to the disclosure. The figure illustrates receiver-side joint estimation for all CCs. Down-conversion with adjusted Los and pilot modification may be needed.

The radio signal received from antenna port 1 101 passes an RF filter 1 102. The RF filter output signal is then multiplied 1 104 with a first carrier frequency fc1 , 1 103, e.g. as described above with respect to Fig. 1 1 , to down-convert the RF filter output signal. The down-converted signal is passed to a cross-correlation and peak detection stage 1220, e.g. corresponding to the first cross-correlation stage 1 1 15 and the peak detector 1 123 as described above with respect to Fig. 1 1 . In a pilot adjustment stage 1210, the carrier adjustment frequency Afc, 1 120 which is the difference of second carrier frequency fc2, 1 105 and first carrier frequency fc1 , 1 103 is multiplied 121 1 with the second pilot sequence 1 1 12 to provide an adjusted pilot sequence which is added 1212 to the first pilot sequence 1 1 1 1 and passed to the cross-correlation and peak detection stage 1220 which detects a peak 1221 in the cross-correlation signal shape to detect the localization information in the received signal from antenna 1 101.

The various transmitter and receiver devices described above may also be described in terms of computation methods. For example, a method for localizing a position of a mobile device may include the following steps: receiving, by a mobile device, at least one radio signal from a corresponding radio transceiver, in particular a base station, wherein the at least one radio signal comprises at least one carrier component, CC, comprising a set of pilot symbols for localizing the mobile device; and determining localization information, in particular a time of arrival, TOA, of the at least one radio signal, based on the set of pilot symbols of the at least one CC. Such a method provides an efficient mechanism for localizing the position of a mobile device. In particular, the method improves the accuracy of localization estimation below the centimeter range. Accuracy up to centimeter range or even to millimeter range can be achieved. The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein, in particular the steps of the method described above. Such a computer program product may include a readable non-transitory storage medium storing program code thereon for use by a computer. The program code may perform the processing and computing steps described herein, in particular the method described above. While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms "coupled" and "connected", along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1 . A mobile device (1010), comprising: a receiver (101 1 ), configured to receive at least one radio signal (1025, 1035, 1045) from a corresponding radio transmitter, in particular a base station (1020, 1030, 1040), wherein the at least one radio signal comprises at least one carrier component (401 , 402), CC, comprising a set of pilot symbols for localizing the mobile device (1010); and a processor (1012), configured to determine localization information (1013), in particular a time of arrival, TOA, of the at least one radio signal (1025, 1035, 1045), based on the set of pilot symbols of the at least one CC (401 , 402).

2. The mobile device (1010) of claim 1 , wherein at least two CCs (331 , 332) of the same radio signal (1025) or of different radio signals (1025, 1035, 1045) are transmitted on different carrier frequencies (333, 334) with respect to each other. 3. The mobile device (1010) of claim 1 or 2, wherein the processor (1012) is configured to determine the localization information (1013) based on a joint processing of the set of pilot symbols of at least two CCs (331 , 332).

4. The mobile device (1010) of one of the preceding claims, wherein at least two CCs (21 1 , 212) are contiguously arranged within a frequency band (210) of the at least one radio signal (1025).

5. The mobile device (1010) of one of claims 1 to 3, wherein at least two CCs (331 , 332) are non-contiguously arranged within a frequency band (330) of the at least one radio signal (1025).

6. The mobile device (1010) of one of the preceding claims, wherein a frequency band (330) for joint processing of the set of pilot symbols of at least two CCs (331 , 332) is chosen in a way that at least one CC (332) is located at an edge of the frequency band (330).

7. The mobile device (1010) of one of the preceding claims, wherein the receiver (101 1 , 400, 520) comprises a plurality of single processing chains (521 , 522), each single processing chain (521 , 522) associated with a respective CC (401 , 402).

8. The mobile device (1010) of claim 7, wherein each single processing chain (521 , 522) comprises a down-converter (422,

423) configured to down-convert (420) the respective CC (401 , 402) to baseband (430).

9. The mobile device (1010) of claim 7 or 8, wherein the processor (1012) is configured to determine the localization information (1013) based on a combination of separate localization estimations per CC (401 , 402). 10. The mobile device (1010) of one of the preceding claims, wherein the receiver (101 1 , 600) comprises at least one joint processing chain (720), wherein the at least one joint processing chain (720) is associated with at least two CCs (401 , 402).

1 1 . The mobile device (1010) of claim 10, wherein the at least one joint processing chain (720) comprises a down-converter

(622) configured to jointly down-convert (620) the at least two CCs (401 , 402) to baseband (630).

12. The mobile device (1010) of claim 10 or 1 1 , wherein the processor (1012) is configured to determine the localization information (1013) based on a joint processing with respect to the set of pilot symbols comprised in the at least two CCs (401 , 402).

13. The mobile device (1010) of one of claims 10 to 12, wherein the at least one joint processing chain (720) is implemented in time domain having a higher sampling rate than each of a plurality of single processing chains associated with respective CCs (401 , 402); and/or wherein the at least one joint processing chain (720) is implemented in frequency domain considering a larger frequency band than each of a plurality of single processing chains associated with respective CCs (401 , 402).

14. The mobile device (1010) of one of the preceding claims, wherein the processor (1012) is configured to adjust local replicas of the set of pilot symbols, wherein adjusting the local replicas includes a phase adjustment of the pilot symbols. 15. The mobile device (1010) of one of the preceding claims, wherein the processor (1012) is configured to jointly detect the set of pilot symbols and estimate the localization information (1013) based on the jointly detected pilot symbols.

16. The mobile device (1010) of one of the preceding claims, wherein the processor (1012) is configured to perform band-pass filtering to suppress signal components between the CCs (401 , 402).

17. The mobile device (1010) of one of the preceding claims, wherein the receiver (101 1 ) is configured to receive signaling information from a base station (1020, 1030, 1040), the signaling information indicating the CCs (401 , 402) to be considered for joint estimation and related information, in particular their carrier frequency (403, 404) and bandwidth (405, 406), as well as the structure of the set of pilot symbols per CC (401 , 402), in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC (401 , 402).

18. The mobile device (1010) of one of the preceding claims, wherein the receiver (101 1 ) is configured to feed back the localization information (1013) obtained by separate localization estimations per CC (401 , 402) and/or the localization information (1013) obtained by joint processing of at least two CCs (401 , 402) to at least one radio transceiver (1020, 1030, 1040).

19. A radio transceiver (1020), in particular a base station, comprising: a transmitter (1022), configured to: transmit a radio signal (1025), wherein the radio signal (1025) comprises at least one carrier component, CC (401 , 402), comprising a set of pilot symbols for localization of a mobile device (1010), wherein the CCs (401 , 402) are transmitted on different carrier frequencies (403, 404) with respect to each other; and transmit signaling information, the signaling information indicating the CCs (401 , 402) to be considered for joint estimation and related information, in particular their carrier frequency (403, 404) and bandwidth (405, 406), as well as the structure of the set of pilot symbols per CC, in particular which allocation of pilots with respect to time, frequency and/or antenna is used per CC (401 , 402); a receiver (1023), configured to receive feedback information from the mobile device (1010), the feedback information comprising localization information (1013) determined by the mobile device (1010) based on different radio signals (1025, 1035, 1045) and/or different CCs (401 , 402); and a processor (1021 ), configured to adjust a transmission time of the transmitter (1022) for the at least one radio signal (1025) and/or the at least one CC (401 , 402), in order to time- align the CCs (401 , 402) and/or the radio signals (1025, 1035, 1045).

20. A communication system (1000), comprising: a plurality of radio transceivers (1020, 1030, 1040), in particular base stations configured to transmit a corresponding plurality of radio signals (1025, 1035, 1045), each radio signal (1025, 1035, 1045) comprising at least one carrier component, CC (401 , 402), the at least one CC (401 , 402) comprising a set of pilot symbols; and a mobile device (1010), configured to receive at least one radio signal (1025) of the plurality of radio signals (1025, 1035, 1045), the at least one radio signal (1025) comprising at least two carrier components, CCs (401 , 402), wherein the mobile device (1010) is configured to determine for each of the at least two CCs (401 , 402) of the same radio signal (1025) or of different radio signals (1025, 1035, 1045) respective localization information (1013), in particular a respective time of arrival, TOA, based on the set of pilot symbols of the at least one CC (401 , 402) of the respective radio signal (1025, 1035, 1045) and to feedback the determined localization information (1013) to the corresponding radio transceivers (1020, 1030, 1040).

21 . The communication system (1000) of claim 20, wherein the mobile device (1010) is configured to determine the localization information (1013) based on a joint processing of the set of pilot symbols in the at least two CCs (401 , 402) transmitted in the at least one radio signal (1025).

22. The communication system (1000) of claim 20 or 21 , wherein the corresponding radio transceivers (1020, 1030, 1040) are configured to adjust their transmission times for at least one CC (401 , 402), based on the feedback from the mobile device (1010) such that the at least two CCs (401 , 402) from the at least one radio signal (1025) are time-aligned.