KR20120047694A - Methods of position tracking of mobile terminal using observed time difference of arrival and mobile terminal using the same - Google Patents

Abstract

PURPOSE: A portable terminal location tracing method and a portable terminal using the same are provided to add weighted value to a signal which is received to the portable terminal without a location tracing module and to trace the location of the portable terminal. CONSTITUTION: A portable terminal presumes a CIR(Channel Impulse Response) based on a received signal(1210). The portable terminal adds weight value to the presumed CIR value(1220). The portable terminal determines the location of the portable terminal by using the added CIR value(1230).

Description

Mobile terminal location tracking method using observed time difference of arrival and mobile terminal using such method {METHODS OF POSITION TRACKING OF MOBILE TERMINAL USING OBSERVED TIME DIFFERENCE OF ARRIVAL AND MOBILE TERMINAL USING THE SAME}

The present invention relates to a mobile terminal location tracking method using the observed time difference (OBSERVED TIME DIFFERENCE OF ARRIVAL, OTDOA) method and a mobile terminal using such a method, more specifically, the location of the mobile terminal using a plurality of base stations The present invention relates to a method for accurately tracking the location of a mobile terminal using a plurality of base stations.

The classification system of the wireless positioning technology used to measure the location of a mobile terminal uses mobile communication signals, positioning methods using satellite signals, and mobile communication signals and satellite signals. There are three ways to measure.

First, the mobile communication signal positioning technology (WN-Based LDT) is a technology for measuring the position of a wireless terminal using mobile communication signals such as IS-95, cdma2000, WCDMA, LTE, etc. It may be classified into a mobile-based mode and a mobile-assisted mode.

The terminal location determination mode (Mobile-Based Mode) is a positioning mode of the wireless terminal. The final positioning or confirmation is performed in the wireless terminal, and additional information on location measurement and calculation may be provided from the network. Radio location techniques such as Cell ID, Time of Arrival (TOA), and Time Difference of Arrival (TDOA) may operate in a terminal positioning mode.

The terminal information providing mode (Mobile-Assisted Mode) is a positioning mode of a wireless terminal, in which a final position determination or confirmation is performed in a network. Information for calculating and determining a position in a terminal (for example, in the case of TDOA, a service base station In this mode, the signal arrival time difference of the base station signal is provided to the network and the final position is determined by the network. Radio positioning technologies such as Angle of Arrival (AOA), Cell ID, Enhanced Cell ID, RF Pattern Matching, TOA and TDOA / OTDOA can operate in a terminal information providing mode.

Next, satellite-based positioning technology (SV-Based LDT) is a technology that uses satellite signals such as GPS, GLONASS, and Galileo. Currently commercialized technology includes GPS positioning technology using a GPS satellite network in the United States. According to the method of determining the final position, it is divided into two modes, a mobile-based mode and a mobile-assisted mode.

Mobile-Based Mode is a positioning mode of a wireless terminal, in which a final position determination or confirmation is performed in a wireless terminal, and may receive additional information about position measurement and calculation from a network. Radio positioning techniques such as Assisted Global Positioning System (AGPS) may operate in a terminal positioning mode.

The terminal information providing mode (Mobile-Assisted Mode) is a positioning mode of a wireless terminal in which a final position determination or confirmation is performed in a network, and a terminal transmits a pseudo-range to a network. In this case, the terminal may receive additional information from the network for calculating the pseudo distance. Radio positioning technology such as Assisted Global Positioning System (AGPS) may operate in a terminal information providing mode.

Finally, hybrid positioning technology (Hybrid LDT) is a wireless positioning technology that combines two or more technologies to improve the accuracy and reliability of the method using a mobile communication signal and the positioning method using a satellite signal. The commonly used method is to increase the availability of information that can be used for location measurement by using satellite signals and mobile communication signals simultaneously. An example is a mix of AGPS technology and TDOA or OTDOA technology.

When the OTDOA method, which is a location estimation method available in the 3rd Generation Partnership Project (3GPP) Long Time Evolution (LTE) system, is used in the above-described location estimation method, due to the relative distance difference between the UE and the eNodeB, Due to a near-far problem in which a path loss caused by the signal is increased and a reception SNR is degraded, a problem in which a UE does not receive a signal transmitted from a neighboring eNodeB (eNodeB) occurs.

In order to solve this problem, a discussion on RS (Reference Signal) design has been conducted at the standardization meeting, and in 3GPP LTE Release 9, PRS (Positioning) for location tracking other than the existing cell-specific RS, MBSFN RS, and UE-Specific RS The use and specification of the Reference Symbol has been determined.

When GPS is used for location tracking as in a conventional mobile terminal, location tracking is not well performed in an internal environment such as a building, and the cost of the portable terminal is increased because the GPS receiver must be provided in the individual portable terminal.

In addition, when using a conventional location tracking method using the OTDOA method, the strength of the signal is attenuated as the distance of the portable terminal from the neighboring base station is far away, thereby reducing the accuracy of the position estimation of the portable terminal.

Accordingly, a first object of the present invention is to provide a portable terminal location tracking method using an observed time difference of arrival (OTDOA), which enables accurate location estimation without additional modules even when the portable terminal is far from a neighboring base station. will be.

In addition, a second object of the present invention is a portable terminal capable of location tracking using an observed time difference of arrival (OTDOA), which enables accurate location estimation without additional modules even when the portable terminal is far from a neighboring base station. To provide.

In accordance with an aspect of the present invention for achieving the first object of the present invention described above, the method for estimating the position of a portable terminal using the observed time difference (OBDOED) is received by the portable terminal from the portable terminal. Obtaining a channel impulse response (CIR) based on the received signal, weighting the obtained channel impulse response, and estimating the position of the portable terminal based on the weighted channel impulse response; It may include the step. The acquiring a channel impulse response based on the signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response may include removing a guard interval of the signal and the guard. Estimating the channel impulse response using at least one of an FFT / IFFT operation and a correlation operation. The acquiring the channel impulse response based on the signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response may include obtaining an average value and a variance value of the estimated channel impulse response; And assigning the weight to the channel impulse response based on the average value and the variance of the estimated channel impulse response. The step of assigning the weight to the channel impulse response based on the average value and the variance of the estimated channel impulse response may include a variance between an average channel impulse response value obtained by using a differential accumulation method and a channel impulse response value of each symbol. The variance at each sample position is normalized to the average weight and then applied to the average channel impulse response obtained through the existing simple accumulation. The estimating of the location of the portable terminal based on the weighted channel impulse response may include adjusting a first arriving path (FAP) detection threshold in consideration of the weight, and calculating a FAP based on the adjusted FAP detection threshold. And detecting the location of the portable terminal based on the OTDOA estimated through the FAP detection. Estimating the location of the portable terminal based on the weighted channel impulse response may be performed in the portable terminal or the base station. Acquiring a channel impulse response based on the signal received by the portable terminal in the portable terminal, and assigning a weight to the obtained channel impulse response may be one of a simple accumulation method and a differential accumulation method. The channel impulse response may be estimated using at least one. Acquiring a channel impulse response based on the signal received by the portable terminal in the portable terminal, and assigning a weight to the obtained channel impulse response may include at least one Positioning Reference Symbol (PRS) received by the portable terminal. The channel impulse response can be estimated using

In addition, the portable terminal for performing the position estimation using the observed time difference of arrival according to an aspect of the present invention for achieving the second object of the present invention to obtain a channel impulse response based on the signal received by the portable terminal Based on a channel impulse response obtaining unit, a weight applying unit applying weights to the obtained channel impulse response, and a channel impulse response weighted from the weight applying unit, a new threshold value is set and a FAP (First Arriving Path) is detected. It may include a FAP detection unit. The portable terminal for estimating the location using the observed arrival time difference may further include a position estimating unit estimating the position of the portable terminal based on the FAP detected by the FAP detector. A channel impulse response obtaining unit for obtaining a channel impulse response based on the signal received by the portable terminal, a guard interval removing unit for removing a guard interval included in the received signal, to the signal from which the guard interval has been removed Performing an FFT operation and performing an IFFT operation on the basis of the channel frequency response estimated through the additional channel estimation and the initial channel estimating unit performing initial channel estimation at the position of the PRS signal to be demodulated. It may include an IFFT operation unit for obtaining a channel impulse response. The channel impulse response obtaining unit obtaining the channel impulse response based on the signal received by the portable terminal may obtain the channel impulse response through a correlation operation. The channel impulse response obtaining unit for obtaining a channel impulse response based on the signal received by the portable terminal may estimate the channel impulse response using at least one of a simple accumulation method and a differential accumulation method on the signal received by the portable terminal. have. The channel impulse response obtaining unit obtaining the CIR based on the signal received by the portable terminal may estimate the channel impulse response using at least one Positioning Reference Symbol (PRS) received by the portable terminal. A weight applying unit applying a weight to the obtained channel impulse response buffer stores the obtained channel impulse response until all successive subframes are transmitted, and a channel for calculating an average of the obtained channel impulse response stored in the buffer. An impulse response average value calculator and a channel impulse response variance calculator for calculating the variance of the obtained channel impulse response stored in the buffer may be included. The channel impulse response variance calculator may calculate a variance between an average channel impulse response value obtained by using a differential accumulation method and a channel impulse response value of each symbol.

According to the portable terminal location tracking method using the observed time difference of arrival (OTDOA) according to the embodiment of the present invention and the portable terminal using such a method, a signal received at the portable terminal without additional module for tracking location Add weights to the.

Therefore, even if the GPS module is not installed in the portable terminal, accurate location tracking of the portable terminal can be performed through a method of processing a signal received by the portable terminal in software.

1 is a conceptual diagram illustrating a location estimation method using observed arrival time differences (OTDOA).
Figure 2 shows the change in the channel impulse response (CIR) value by the observed arrival time difference (OTDOA).
FIG. 3 shows a structure of a subframe using a normal CP (Cyclic Prefix) including a Position Reference Signal (PRS) of a 3GPP LTE system used for channel impulse response (CIR) detection.
FIG. 4 illustrates a structure of an extended CP (Cyclic Prefix) subframe including a Position Reference Signal (PRS) of a 3GPP LTE system used for channel impulse response (CIR) detection.
FIG. 5 is a graph illustrating observed root mean square (OTDEA) estimated root mean square (OTDOA) performance of a simple accumulation method and a differential accumulation method.
FIG. 6 is a graph illustrating observed root mean square (OTSEA) estimated root mean square (OTDOA) performance of a simple accumulation method and a differential accumulation method.
7 is a graph to which weights based on dispersion of channel impulse response (CIR) values according to an embodiment of the present invention are applied.
8 is a graph illustrating observed root mean square (OTDOA) estimated root mean square (OTDOA) performance when estimating a channel impulse response (CIR) value using a simple cumulative weighted method according to an embodiment of the present invention. to be.
FIG. 9 is a graph illustrating observed performance of estimated OTDOA root mean square (RMSE) performance between a simple accumulation method and a differential accumulation method.
FIG. 10 is a graph illustrating the performance of a position estimation cumulative distribution function (CDF) when a weight is applied according to an embodiment of the present invention.
FIG. 11 is a graph illustrating the performance of a position estimate cumulative distribution function (CDF) when a weight is applied according to an embodiment of the present invention.
12 is a flowchart illustrating a method of estimating a location using an observed arrival time difference (OTDOA) according to an embodiment of the present invention.
FIG. 13 is a conceptual diagram of a portable terminal for performing location estimation using an observed arrival time difference (OTDOA) according to an embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

Hereinafter, a channel impulse response (CIR) used in an embodiment of the present invention is a signal transmitted from a transmitting terminal in an environment covered by many buildings such as an urban environment when transmitting a signal from a transmitting end to a receiving end. Rather than going directly to the building, it refers to a plurality of impulse responses detected at the receiving end because they are reflected from a place such as a building.

In the following embodiment of the present invention, the term “arrival time difference observed” may be used in the same sense as OBDOED TIME DIFFERENCE OF ARRIVAL (OTDOA).

1 is a conceptual diagram illustrating a location estimation method using observed arrival time differences (OTDOA).

Referring to FIG. 1, the observed time difference of arrival (OTDOA) measures a signal arrival time difference between signals transmitted from a plurality of eNodeBs.

The measured difference in arrival time of the received signal is converted into respective hyperbolas, and the position estimation using the observed time difference of arrival (OTDOA) uses a method of estimating the intersection point between the hyperbolas as the position of the portable terminal. Here, the arrival time difference is expressed as a timing offset of a neighboring cell signal based on a serving cell signal, and the estimation of the timing offset is a phase of a frequency-domain Positioning Reference Symbol (PRS) signal. It can be estimated using the rotation and time domain channel impulse response (CIR) values. When estimating OTDOA using frequency-domain phase rotation, the first path of the time-domain CIR value cannot be guaranteed because the receiver estimates the components due to the multipath delay of the channel and the OTDOA together to ensure accurate estimation performance. ) Can be prevented from performance degradation due to the multipath delay of the channel.

In the OTDOA estimation method using the channel impulse response (CIR), the CIR is detected by obtaining a channel frequency response (CFR) using a PRS signal after the FFT, and then detecting the channel impulse response (CIR) through an IFFT operation. Alternatively, detection of CIR through cross-correlation with a time domain PRS signal is possible.

Hereinafter, an embodiment of the present invention discloses a method for detecting CIR using FFT operation for convenience of description, but a method for detecting CIR using correlation is also provided, unless it is departed from the essence of the present invention. It is included in the scope of right.

번째 심볼의

번째 부반송파 신호는 수학식 1과 같이 나타낼 수 있다. After receiving end FFT

Of the first symbol

The first subcarrier signal may be represented by Equation 1.

는 서빙 셀 PRS를 나타내고,

는 휴대용 단말기와 서빙 셀 사이의 CFR(Channel Frequency Response)를 의미한다. 또한,

는

번째 인접 셀 PRS를 나타내고

는 휴대용 단말기와

번째 인접 셀 간의 CFR을 의미한다.

는 위치 추정에 이용되는 인접 셀의 수이다. here

Represents the serving cell PRS,

Means channel frequency response (CFR) between the mobile terminal and the serving cell. Also,

Is

Represents the first adjacent cell PRS

With a portable terminal

CFR between the first adjacent cell.

Is the number of neighbor cells used for position estimation.

번째 인접셀 PRS 위치로부터 초기 LS(Least Square) 채널 추정은 아래의 수학식 2와 같이 나타낼 수 있다.

The initial LS channel estimation from the first neighbor cell PRS location may be expressed by Equation 2 below.

는

번째 인접 셀 PRS의 위치 집합이다. here

Is

The position set of the first neighbor cell PRS.

번째 인접 셀 사이의 CIR을 얻을 수 있다. Therefore, the UE and the N-point IFFT operation as shown in Equation 3 below

The CIR between the first adjacent cell can be obtained.

Figure 2 shows the change in the channel impulse response (CIR) value by the observed arrival time difference (OTDOA).

Referring to FIG. 2, when the OTDOA between the PRS signal of the serving eNodeB and the PRS signal of the neighboring eNodeB is 9, the CIR value is shifted to the right by 9 samples as compared with the case where the OTDOA is 0. Therefore, OTDOA can be estimated by the degree of movement of the CIR value of the PRS signal of the adjacent cell.

The determination of the degree to which the CIR is moved can be performed by detecting a path having the maximum power and a method of detecting a CIR position exceeding a threshold by setting an appropriate threshold value. Since the performance depends on the path channel environment characteristics, the present invention applies a FAR (First Arriving Path) detection method by setting a threshold according to a path to noise power ratio (PNR). The detection of the FAP determines the first CIR value exceeding the threshold as the FAP, and the threshold for detecting the FAP can be expressed by Equation 4 below.

는 PRS 신호의 총 전력,

는 zero-th order Bessel function of first kind를 의미하며,

는 최대 도플러 주파수,

는 심볼 길이,

는 누적된 심벌 수,

은 누적된 심볼간 간격을 의미한다.
here

Is the total power of the PRS signal,

Means zero-th order Bessel function of first kind,

Is the maximum Doppler frequency,

Is the symbol length,

Is the cumulative number of symbols,

Is the accumulated inter-symbol spacing.

FIG. 3 shows a structure of a subframe using a normal CP (Cyclic Prefix) including a Position Reference Signal (PRS) of a 3GPP LTE system used for channel impulse response (CIR) detection.

3 illustrates a distribution of slots and subcarriers of a PRS symbol when transmitting a subframe using a normal CP using a number of one or two physical broadcast channel (PBCH) transmit antenna ports. 3 shows a distribution in slots and subcarriers of a PRS symbol when four physical broadcast channel (PBCH) transmit antenna port numbers are used.

Referring to FIG. 3, when a normal CP is used, eight PRS symbols are included in six subcarriers.

FIG. 4 illustrates a structure of an extended CP (Cyclic Prefix) subframe including a Position Reference Signal (PRS) of a 3GPP LTE system used for channel impulse response (CIR) detection.

4 shows a distribution of slots and subcarriers of a PRS symbol when transmitting a subframe using an extended CP (cyclic prefix) using one or two physical broadcast channel (PBCH) transmit antenna port numbers. 4 illustrates a distribution of slots and subcarriers of a PRS symbol using four physical broadcast channel (PBCH) transmit antenna port numbers.

Referring to FIG. 4, when the extended CP is used, six PRS symbols are included in eight subcarriers.

In general, an extended CP is inefficient in terms of overhead of a CP, but may be used in an environment in which a delay spread in which a signal spreads in time is large, such as a large cell.

는 아래의 수학식 5와 같이 CRS와 동일한 PRBS(Pseudo Random Binary Sequence) 생성기를 이용하여 생성될 수 있다. PRS Sequence in 3GPP LTE System

May be generated using a Pseudo Random Binary Sequence (PRBS) generator identical to the CRS as shown in Equation 5 below.

는 슬롯 넘버(Slot Number),

은 심볼 넘버(Symbol Number)를 의미한다.

Is the slot number,

Means a symbol number.

는 공액 복소 심벌

로 아래의 수학식 6과 같이 매핑되며, 도 3 또는 4와 같이 Cell/UE Specific RS(Reference Symbol)와 중첩을 피한 대각선(Diagonal)형태를 가진다. PRS sequence

The conjugate complex symbol

It is mapped as shown in Equation 6 below, and has a diagonal form avoiding overlapping with a Cell / UE Specific RS (Reference Symbol) as shown in FIG. 3 or 4.

는 상위 계층(Layer)에 의해 결정되며, Cell-Specific Frequency Shift

는

로 정의 된다. Where bandwidth for PRS

Is determined by the upper layer, Cell-Specific Frequency Shift

Is

Is defined as

 In OTDOA estimation, since the minimum signal to interference and noise ratio (SINR) of the received signal is considered to be -14 dB, serious OTDOA estimation performance degradation may occur when using a single subframe. Accordingly, an estimation method of accumulating signals by transmitting a plurality of PRS subframes may be used for accurate OTDOA estimation.

The number of subframes that can be continuously transmitted is determined by an upper layer and can transmit 1, 2, 4, or 6 subframes. When the CIRs of consecutive PRS subframes are used for OTDOA estimation, it is possible to obtain an improved estimation performance due to accumulation, but the maximum number of PRS subframes that can be transmitted is limited to six. There are limitations in improving performance, so we need a way to overcome them.

In the general communication environment, the change in the path delay of the multipath channel of the signal is slower than the change in amplitude and phase, thereby improving noise performance by accumulating the estimated CIR values for each symbol. Accumulation of CIR values is a simple cumulative method of calculating the average estimated value by adding the CIR values of each symbol and dividing by the number of symbols, and the CIR values of previous symbols proposed by Mingqi Li to prevent distortion of the CIR values by Doppler frequency. It can be distinguished by a differential cumulative method that accumulates after a conjugate complex product. In the case of simple accumulation, the performance degradation is large because the change in the CIR value increases as a high-speed environment having a large change in the CIR value or as the number of accumulated symbols increases. On the other hand, the method of accumulating the conjugate complex product result between adjacent CIR values has the advantage that it is possible to accurately estimate the CIR value even in a high-speed environment and a large number of cumulative symbols by limiting the change of the CIR value through the conjugate complex product operation. The disadvantage is that the noise power increases during the conjugate complex product operation.

번째 neighboring eNodeB간의 CIR 값 은 아래의 수학식 7과 같이 나타낼 수 있다.UEs estimated by simple cumulative

The CIR value between the first neighboring eNodeBs may be represented by Equation 7 below.

은 서브프레임 인덱스,

는 연속적으로 전송된 PRS 서브프레임의 수,

는 PRS 심벌 인덱스, 그리고

는 단일 PRS 서브프레임 내의 PRS 심볼의 수를 의미한다.here

Is the subframe index,

Is the number of consecutively transmitted PRS subframes,

Is the PRS symbol index, and

Denotes the number of PRS symbols in a single PRS subframe.

The CIR value between the UE and the j th neighboring eNodeB estimated by the differential accumulation is expressed by Equation 8 below.

FIG. 5 is a graph illustrating observed root mean square (OTDEA) estimated root mean square (OTDOA) performance of a simple accumulation method and a differential accumulation method.

인 경우를 가정한 것이다. In an extended typical urban (ETU) channel environment, a subframe using a normal CP with an FFT size of 1024 is transmitted and the speed of a mobile station (UE) is 3

Is assumed.

Referring to FIG. 5, assuming that a differential accumulation scheme is used, a graph when one PRS subframe is transmitted, a graph when two PRS subframes are transmitted, and four PRS subframes that are transmitted are shown. Graph, graph when six PRS subframes are transmitted and graph when one PRS subframe is transmitted, graph when two PRS subframes are transmitted, and PRS transmitted under the assumption that a simple accumulation method is used. The graph when four subframes are shown and the graph when six PRS subframes are transmitted are shown.

축은 서빙 셀의 기지국으로부터의 거리를 나타내고, 그래프의

축은 OTDOA의 추정 RMSE(Root Mean Square Error)를 나타낸다. Graph

The axis represents the distance from the base station of the serving cell,

The axis represents the estimated root mean square error (RMS) of OTDOA.

Referring to FIG. 5, as the number of accumulated subframes increases, the OTDOA may be accurately estimated. As the distance from the base station of the serving cell increases, the OTDOA may be relatively closer to the neighboring cell base station.

인 경우, 단순 누적 방식이 차동 누적 방식보다 정확한 추정 성능을 보임을 알 수 있다.
Mobile Speed 3

In this case, it can be seen that the simple accumulation method shows more accurate estimation performance than the differential accumulation method.

FIG. 6 is a graph illustrating observed root mean square (OTSEA) estimated root mean square (OTDOA) performance of a simple accumulation method and a differential accumulation method.

인 경우를 가정한 것이다. In an ETU (Extended Typical Urban) channel environment, a subframe using a normal CP with an FFT size of 1024 is transmitted and the speed of a mobile station (UE) is 30

Is assumed.

Referring to FIG. 6, assuming that a differential accumulation scheme is used, a graph when one PRS subframe is transmitted, a graph when two PRS subframes are transmitted, and four PRS subframes that are transmitted are shown. Graph, graph when six PRS subframes are transmitted and graph when one PRS subframe is transmitted, graph when two PRS subframes are transmitted, and PRS transmitted under the assumption that a simple cumulative method is used. The graph when four subframes are shown and the graph when six PRS subframes are transmitted are shown.

축은 서빙 셀의 기지국으로부터의 거리를 나타내고, 그래프의

축은 OTDOA의 추정 RMSE(Root Mean Square Error)를 나타낸다. Graph

The axis represents the distance from the base station of the serving cell,

The axis represents the estimated root mean square error (RMS) of OTDOA.

Referring to FIG. 6, as the number of accumulated subframes increases, the OTDOA may be accurately estimated. As the distance from the base station of the serving cell increases, the OTDOA may be relatively closer to the neighboring cell base station.

인 경우, 4개 이하의 연속적인 PRS 서브프레임을 전송하는 경우에는 단순 누적 방식이 차동 누적 방식보다 정확한 OTDOA 추정성능을 가지나, 6개의 연속적인 서브프레임을 전송하는 경우, 차동 누적방식이 단순 누적 방식보다 정확한 OTDOA 추정 성능을 가진다. Mobile Speed 30

In the case of transmitting 4 or less consecutive PRS subframes, the simple accumulation scheme has more accurate OTDOA estimation performance than the differential accumulation scheme. However, when the six consecutive subframes are transmitted, the differential accumulation scheme is a simple accumulation scheme. Has more accurate OTDOA estimation performance.

In conventional general OFDM systems, the cumulative estimation of CIR values is based on simple accumulation, which is suitable for low-speed environments in which the temporal change of the channel due to the accumulated Doppler frequency is not large, or in the environment where the temporal change between accumulated CIRs is large. The differential accumulation method, which is designed to improve the noise performance by fixing the change of the CIR in the high speed environment.

에서 30

)를 고려하고 있기 때문에 단순 누적 방식이 차동 누적 방식보다 OTDOA 추정에 적합하다 하지만 최대로 이용 가능한 PRS 서브프레임의 수가 제한적일 뿐만 아니라 단순 누적 방식의 고속 환경에서의 성능 열화로 인해 다수의 PRS 서브프레임을 이용하는 경우에도 추정 성능 개선의 한계가 발생한다. Relatively low moving vehicle speed in location service using OTDOA of LTE system (3

From 30

), But the simple accumulation scheme is more suitable for OTDOA estimation than the differential accumulation scheme.However, the maximum number of PRS subframes available is not only limited, but also due to the performance degradation in the high-speed environment of the simple accumulation scheme. Even when used, there is a limit of improving the estimated performance.

 According to an embodiment of the present invention, by applying weights according to the temporal variance of each CIR value to the accumulated CIR values, not only the performance deterioration of the general accumulation method according to the increase of the moving body speed but also the OTDOA estimation accuracy can be improved. A weighting method based on the dispersion of the CIR may be used.

The reason for accumulating CIR in OTDOA estimation according to an embodiment of the present invention is not to estimate an accurate CIR value, but to estimate an accurate first arriving path (FAP) location, thereby improving CIR detection capability. The weight setting method according to the variance value of may be used.

The estimated CIR in the time-varying channel environment may be represented by dividing the location including the multipath component and the location where only other noise components exist as shown in Equation (9).

값에 대해 일정하다고 가정한다면, 시변 채널 환경에서

이 시간에 따라 변화하기 때문에 CIR 값의 위치에 따른 시간적 분산은 다중 경로 위치에서의 분산이 잡음 위치에서의 분산보다 크다. 따라서 누적된 CIR 값에 분산에 따른 가중치를 적용함으로써 FAP 검출 성능을 향상 시킬 수 있다.
Noise power all

Assuming constant values, in a time-varying channel environment

Because it changes over time, the temporal variance according to the position of the CIR value is larger than the variance at the noisy position. Therefore, FAP detection performance can be improved by applying weights according to variance to the accumulated CIR values.

및 가중치 적용에 따른 임계값

은 아래의 수학식 10과 같이 나타낼 수 있다.Weighted CIR over time variance

And threshold values

May be represented by Equation 10 below.

은 정규화된 분산에 따른 가중치,

은 계산된 가중치를 의미하고,

는 차동 누적 방식을 사용하여 얻은 평균 CIR값을 의미한다. 단순 누적 평균값이 고속 환경에서 CIR의 변화로 인해 왜곡되기 때문에 차동 누적을 이용하여 얻은 평균 CIR을 사용할 수 있다.

Is the weight according to the normalized variance,

Means the calculated weight,

Is the average CIR value obtained using the differential cumulative method. Since the simple cumulative mean value is distorted due to the change in the CIR in a high speed environment, the average CIR obtained using differential accumulation can be used.

에 적용할 수 있다. 이때 적용된 가중치에 의해 전체 CIR의 레벨이 변화하기 때문에 기존의 FAP 검출에서의 임계값을 전체 CIR의 크기가 변화한만큼(

) 다시 재설정해준 뒤, FAP 검출을 수행할 수 있다.
In order to determine the variance, the variance is calculated by calculating the variance between the average CIR value obtained by using the differential cumulative method and the CIR value of each symbol, normalizing the variance value at each sample position (normalized by the average weight), and then Average CIR obtained through simple accumulation of

Applicable to In this case, since the level of the total CIR changes according to the applied weight, the threshold value in the conventional FAP detection is changed as the magnitude of the total CIR changes (

After resetting, FAP detection can be performed.

7 is a graph to which weights based on dispersion of channel impulse response (CIR) values according to an embodiment of the present invention are applied.

축 값으로 시간 도메인 인덱스값을 가지고

축 값으로 CIR의 크기(전력)를 나타내는 좌표 평면 상에 도시되어 있다. Referring to FIG. 7, a graph representing a variance value according to a CIR value, a graph before applying a weight, and a graph after applying a weight are shown.

Take a time domain index as an axis value

It is shown on a coordinate plane that represents the magnitude (power) of the CIR as the axis value.

Even when the weight is applied, the position of the CIR does not change but the size changes. According to the above formula, the weight is relatively higher in the section including the CIR than the section including the noise only. Accurate FAP values can be detected.

Because the weights are applied after normalization, the CIR values in the samples below the 40th weight that are lower than the 40th weighted samples are lower than before the weighting, so that the values where relative detection should be increased and errors may occur. Notice that the value decreases at the location.

8 is a graph illustrating observed root mean square (OTDOA) estimated root mean square (OTDOA) performance when estimating a channel impulse response (CIR) value using a simple cumulative weighted method according to an embodiment of the present invention. to be.

일 경우를 전제로 각 그래프는 가중치를 적용하지 않은 단순 누적 방식을 사용할 경우 전송되는 PRS 서브프레임이 1개일 경우의 그래프, 전송되는 PRS 서브프레임이 2개일 경우의 그래프, 전송되는 PRS 서브프레임이 4개일 경우의 그래프, 전송되는 PRS 서브프레임이 6개일 경우의 그래프와 본 발명의 일실시예에 따른 가중치를 적용한 단순 누적 방식을 사용하는 것을 전제하고 전송되는 PRS 서브프레임이 1개일 경우의 그래프, 전송되는 PRS 서브프레임이 2개일 경우의 그래프, 전송되는 PRS 서브프레임이 4개일 경우의 그래프, 전송되는 PRS 서브프레임이 6개일 경우의 그래프이다.Referring to FIG. 8, the speed of the mobile unit UE is 3

In this case, each graph has a graph when one PRS subframe is transmitted, a graph when two PRS subframes are transmitted and 4 PRS subframes are transmitted when a simple cumulative method without weighting is used. Graph, transmission graph of six PRS subframes and transmission of one PRS subframe assuming the use of a simple cumulative method with weights according to an embodiment of the present invention, transmission This is a graph when two PRS subframes are used, a graph when four PRS subframes are transmitted, and a graph when six PRS subframes are transmitted.

축은 서빙 셀의 기지국으로부터의 거리를 나타내고, 그래프의

축은 OTDOA의 추정 RMSE(Root Mean Square Error)를 나타낸다. Graph

The axis represents the distance from the base station of the serving cell,

The axis represents the estimated root mean square error (RMS) of OTDOA.

Referring to FIG. 8, in the case of applying a weight according to an embodiment of the present invention, when transmitting one subframe, the existing weight is not applied except when the distance from the serving base station is within 200 meters. It can be seen that the OTDOA estimation performance is superior to the simple cumulative method.

FIG. 9 is a graph illustrating observed performance of estimated OTDOA root mean square (RMSE) performance between a simple accumulation method and a differential accumulation method.

It is assumed that a subframe using a normal CP having an FFT size of 1024 is transmitted in an ETU (Extended Typical Urban) channel environment and the speed of a mobile station (UE) is 30 km / h.

일 경우를 전제로 각 그래프는 가중치를 적용하지 않은 단순 누적 방식을 사용할 경우 전송되는 PRS 서브프레임이 1개일 경우 의 그래프, 전송되는 PRS 서브프레임이 2개일 경우의 그래프, 전송되는 PRS 서브프레임이 4개일 경우의 그래프, 전송되는 PRS 서브프레임이 6개일 경우의 그래프와 본 발명의 일실시예에 따른 가중치를 적용한 단순 누적 방식을 사용하는 것을 전제하고 전송되는 PRS 서브프레임이 1개일 경우의 그래프, 전송되는 PRS 서브프레임이 2개일 경우의 그래프, 전송되는 PRS 서브프레임이 4개일 경우의 그래프, 전송되는 PRS 서브프레임이 6개일 경우의 그래프)이다.Referring to Figure 9, the speed of the mobile unit (UE) is 30

In this case, each graph has a graph when one PRS subframe is transmitted, a graph when two PRS subframes are transmitted and 4 PRS subframes are transmitted when a simple cumulative method without weighting is used. Graph, transmission graph of six PRS subframes and transmission of one PRS subframe assuming the use of a simple cumulative method with weights according to an embodiment of the present invention, transmission Graph when two PRS subframes are used, graph when four PRS subframes are transmitted, and graph when six PRS subframes are transmitted).

축은 서빙 셀의 기지국으로부터의 거리를 나타내고, 그래프의

축은 OTDOA의 추정 RMSE(Root Mean Square Error)를 나타낸다. Graph

The axis represents the distance from the base station of the serving cell,

The axis represents the estimated root mean square error (RMS) of OTDOA.

9, the speed of the moving body is 30 Even in the case where the method of applying a weight according to an embodiment of the present invention transmits one subframe, except that when the distance to the serving base station is within 200 meters, the simple accumulation without applying the existing weight It can be seen that the OTDOA estimation performance is superior to the method.

FIG. 10 is a graph illustrating the performance of a position estimation cumulative distribution function (CDF) when a weight is applied according to an embodiment of the present invention.

축은 위치 추정을 한 경우, 위치 추정을 한 거리와 실제의 위치에서 떨어진 거리를 나타내고,

축은 누적된 확률 분포를 나타낸다. 10, the coordinate plane

The axis represents the distance from the position estimate and the distance away from the actual position in the case of the position estimate,

The axis represents the cumulative probability distribution.

인 것을 가정하고 기존의 단순 누적 방식을 사용했을 때 추정된 OTDOA값을 기초로 위치 추정 누적 분포 함수를 전송되는 서브 프레임의 개수에 따라 표현한 그래프와 이동체의 속도가 3

인 것을 가정하고 가중치를 부가한 단순 누적 방식을 사용했을 때 추정된 OTDOA값을 기초로 위치 추정 누적 분포 함수를 전송되는 서브 프레임의 개수에 따라 표현한 그래프이다. Each graph has a moving speed of 3

In the case of using the conventional simple cumulative method, the speed of the graph and the moving object expressing the position estimation cumulative distribution function according to the number of subframes transmitted is 3 based on the estimated OTDOA value.

It is a graph that expresses the position estimation cumulative distribution function according to the number of subframes transmitted on the basis of the estimated OTDOA value when a simple cumulative method with weights is assumed.

Referring to the graph, when six consecutive frames are transmitted, the probability that the difference between the actual position of the moving object and the estimated position is within 50 meters is 85.42% when the conventional simple accumulation method is used. The weighted position estimation method has a value of 88.96%. The probability that the difference between the actual position and the estimated position of the moving object is within 100 meters has a value of 94.88% when using the conventional simple cumulative method, whereas a value of 97% is used when weighting the CIR used in the present invention. Have

That is, the method of weighting the CIR value disclosed in the present invention has a higher accuracy of position estimation than the conventional method.

FIG. 11 is a graph illustrating the performance of a position estimate cumulative distribution function (CDF) when a weight is applied according to an embodiment of the present invention.

축은 위치 추정을 한 경우, 위치 추정을 한 거리와 실제의 위치에서 떨어진 거리를 나타내고,

축은 누적된 확률 분포를 나타낸다. Referring to FIG. 11, the coordinate plane

The axis represents the distance from the position estimate and the distance away from the actual position in the case of the position estimate,

The axis represents the cumulative probability distribution.

인 것을 가정하고 기존의 단순 누적 방식을 사용했을 때 추정된 OTDOA값을 기초로 위치 추정 누적 분포 함수를 전송되는 서브 프레임의 개수에 따라 표현한 그래프와 이동체의 속도가 30

인 것을 가정하고 가중치를 부가한 단순 누적 방식을 사용했을 때 추정된 OTDOA값을 기초로 위치 추정 누적 분포 함수를 전송되는 서브 프레임의 개수에 따라 표현한 그래프이다. Each graph has a speed of 30

In the case of using the conventional simple cumulative method, the speed of the graph and the moving object expressing the position estimation cumulative distribution function according to the number of subframes transmitted is 30 based on the estimated OTDOA value.

It is a graph that expresses the position estimation cumulative distribution function according to the number of subframes transmitted on the basis of the estimated OTDOA value when a simple cumulative method with weights is assumed.

Referring to the graph, when six consecutive frames are transmitted, the probability that the difference between the actual position of the moving object and the estimated position is within 50 meters is 79.28% when using the conventional simple cumulative method. The weighted position estimation method has a value of 85.83%. The probability that the difference between the actual position and the estimated position of the moving object is within 100 meters has a value of 91.43% using the conventional simple cumulative method, while a value of 95.63% is used for the weighted method of the CIR used in the present invention. Have

That is, the method of weighting the CIR value disclosed in the present invention has a higher accuracy of position estimation than the conventional method.

12 is a flowchart illustrating a method of estimating a location using an observed arrival time difference (OTDOA) according to an embodiment of the present invention.

Referring to FIG. 12, in the position estimation method using OTDOA, a step 1210 of estimating a CIR based on the received signal, a weighting of the estimated CIR value 1220, and a weighted CIR value are used. In operation 1230, the location of the portable terminal may be determined.

Hereinafter, in one embodiment of the present invention, estimating the CIR based on the received signal is performed through a method of performing an FFT / IFFT operation. However, the CIR is not formed using the correlation but the FIR / IFFT operation. The method of estimating is also included in the scope of the present invention.

Estimating the CIR based on the received signal (step 1210) involves removing the guard interval of the signal (1210-1) to determine the guard interval included in the signal to avoid interference with adjacent channels of the signal. Remove The signal from which the guard interval is removed is converted into a signal in the frequency domain through an FFT operation 1210-3, and the converted signal is subjected to an initial channel estimation step 1210-5 at a PRS signal position to be demodulated. A CIR may be obtained using an IFFT operation from the channel frequency response estimated through the initial channel estimation step 1210-5, at 1210-7.

In order to estimate the CIR, not only an FFT / IFFT operation but also a correlation operation may be used, and the CIR estimation using such a correlation operation is also included in the scope of the present invention.

When performing the correlation process, it is possible to estimate the CIR in the same manner as in Equation 11 below.

는 시간영역 PRS 신호,

은 시간 영역 수신 신호를 의미하고,

는 컨볼루션(convolution)연산을,

는 사이클릭 코릴레이션(cyclic correlation) 연산을 의미한다. here

Is the time domain PRS signal,

Means a time domain received signal,

Is the convolution operation,

Denotes a cyclic correlation operation.

The obtained CIR value may be stored in the buffer until all consecutive subframes are transmitted (1220-1). After all successive subframes are received, a weight may be calculated and applied to the CIR value through steps 1220-3 of obtaining an average value of the CIR values and 1220-5 of obtaining a variance value.

After setting the new threshold value considering the weight based on the weighted CIR value, detecting the first arriving path (FAP) (1230-1), and then detecting the position (1230-3), the UE You can track the location of. This location estimation may be made at the terminal or the base station.

FIG. 13 is a conceptual diagram of a portable terminal for performing location estimation using an observed arrival time difference (OTDOA) according to an embodiment of the present invention.

Referring to FIG. 13, a portable terminal for position estimation using OTDOA includes a signal transceiver 1300, a CIR acquirer 1310, a weight applier 1320, a FAP detector 1330, and a position estimator 1340. May be included.

The signal transceiver 1300 may receive a signal transmitted from a base station and transmit a signal generated by a portable terminal.

The CIR acquirer 1310 may acquire a CIR value based on the PRS included in the signal transmitted from the base station.

The CIR acquirer 1310 may include a guard interval remover 1310-1, an FFT calculator 1310-3, an initial channel estimator 1310-5, and an IFFT calculator 1310-7.

The guard interval removal unit 1310-1 may remove the guard interval included in the signal to avoid interference with the adjacent channel of the signal.

The FFT calculator 1310-3 may perform an FFT operation on the signal from which the guard interval is removed to convert the signal into a signal in the frequency domain.

The initial channel estimator 1310-5 enables initial channel estimation at a PRS signal position to be demodulated by a signal converted into a frequency domain.

The IFFT calculator 1310-7 may obtain a CIR by using an IFFT operation from the channel frequency response estimated through the initial channel estimation.

In order to obtain the CIR, the CIR obtaining unit 1310 may use not only the above-described FFT / IFFT operation but also a correlation (Correlation) operation, and obtaining a CIR using such a correlation operation is also within the scope of the present invention. Included in

The weight applying unit 1320 may apply a weight to the obtained CIR value.

The weight applying unit 1320 may include a buffer 1320-1, an average value calculator 1320-3, and a dispersion value calculator 1320-5.

The buffer 1320-1 may be included in the weighting unit 1320 to be stored until all consecutive subframes of the obtained CIR value are transmitted.

The CIR average value calculator 1320-3 may calculate an average of the CIR values stored in the buffer 1320-1.

The CIR variance calculator 1320-5 may calculate a variance of the CIR values stored in the buffer 1320-1.

That is, the weight applying unit 1320 receives all the successive subframes, and then passes through the average value calculating unit 1320-3 for obtaining the average value of the CIR values and the dispersion value calculating unit 1320-5 for obtaining the variance values. The weight to be applied to the value can be calculated and applied to the CIR.

The FAP detector 1330 may set a new threshold value in consideration of the weight based on the weighted CIR value and detect the FAP (First Arriving Path).

The location estimator 1340 may track the location of the portable terminal through a method of detecting a location based on the FAP detected by the FAP detector. For convenience of description, although the location estimator 1340 is illustrated as being located in the portable terminal, the location estimator 1340 may be located in the base station. When the location estimation is performed at the base station, the terminal may perform only the FAP detection process using the FAP detector 1330 and the location estimation may occur at the base station. That is, the form except for the position estimation unit 1340 is also included in the portable terminal according to an embodiment of the present invention.

Unlike the location tracking method according to an embodiment of the present invention, if the location tracking method using the GPS used in the existing portable terminal is used, the location tracking is not easy in an internal environment such as a building, and the GPS in the individual portable terminal Since the receiver must be provided, the cost of the portable terminal increases.

However, according to an embodiment of the present invention, since the GPS module may be installed in the portable terminal, the location tracking method proposed in the present invention may be easily performed in the existing portable terminal. Can be applied.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (16)

In the method of estimating the position of the portable terminal using the observed time difference (OBSERVED TIME DIFFERENCE OF ARRIVAL, OTDOA),
Acquiring a channel impulse response (CIR) based on a signal received by the portable terminal at the portable terminal and weighting the obtained channel impulse response; And
Estimating the position of the portable terminal based on the weighted channel impulse response. The method of claim 1, wherein the acquiring a channel impulse response based on a signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response comprises:
Removing a guard interval of the signal; And
Estimating the channel impulse response using at least one of an FFT / IFFT operation and a correlation operation on the signal from which the guard interval has been removed. The method of claim 1, wherein the acquiring a channel impulse response based on a signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response comprises:
Obtaining an average value and a variance value of the estimated channel impulse response;
And assigning the weight to the channel impulse response based on the average value and the variance of the estimated channel impulse response. The method of claim 3, wherein the assigning the weight to the channel impulse response based on the average value and the variance of the estimated channel impulse response comprises:
Find the variance between the average channel impulse response value obtained by using the differential cumulative method and the channel impulse response value of each symbol, normalize the variance at each sample position with the average weight, and then obtain the average channel obtained through the conventional simple accumulation. A method for estimating a location of a portable terminal using an observed time difference of arrival, which is applied to an impulse response. The method of claim 1, wherein estimating the location of the portable terminal based on the weighted channel impulse response comprises:
Adjusting a first arriving path (FAP) detection threshold in consideration of the weight, and detecting the FAP based on the adjusted FAP detection threshold; and
Estimating the position of the portable terminal based on the OTDOA estimated by the FAP detection. The method of claim 1, wherein estimating the location of the portable terminal based on the weighted channel impulse response comprises:
Method for estimating the position of the portable terminal using the observed arrival time difference, characterized in that made in the portable terminal or the base station.
The method of claim 1, wherein the acquiring a channel impulse response based on a signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response comprises:
And estimating the channel impulse response using at least one of a simple accumulation method and a differential accumulation method on a signal received by the portable terminal. The method of claim 1, wherein the acquiring a channel impulse response based on a signal received by the portable terminal in the portable terminal and weighting the obtained channel impulse response comprises:
And estimating the channel impulse response using at least one Positioning Reference Symbol (PRS) received by the portable terminal. In a portable terminal for estimating the location using the observed arrival time difference,
A channel impulse response obtaining unit obtaining a channel impulse response based on the signal received by the portable terminal;
A weight applying unit applying weights to the obtained channel impulse response; and
And a FAP detector configured to set a new threshold value and detect a FAP (First Arriving Path) based on the weighted channel impulse response from the weight applying unit. The portable terminal of claim 9, wherein the portable terminal estimates the location using the observed arrival time difference.
And a position estimator for estimating the position of the portable terminal based on the FAP detected by the FAP detector. The apparatus of claim 9, wherein the channel impulse response obtaining unit obtains a channel impulse response based on the signal received by the portable terminal.
A guard interval removal unit for removing a guard interval included in the received signal;
An FFT calculator configured to perform an FFT operation on the signal from which the guard interval is removed and convert the signal into a frequency domain signal;
An initial channel estimator for initial channel estimation at a PRS signal position to be demodulated; and
And an IFFT calculation unit for performing a channel impulse response by performing an IFFT operation based on the channel frequency response estimated by the additional channel estimation. The apparatus of claim 9, wherein the channel impulse response obtaining unit obtains a channel impulse response based on the signal received by the portable terminal.
A portable terminal for performing position estimation using the observed time difference of arrival, wherein the channel impulse response is obtained through a correlation operation. The apparatus of claim 9, wherein the channel impulse response obtaining unit obtains a channel impulse response based on the signal received by the portable terminal.
And estimating the channel impulse response using at least one of a simple accumulation method and a differential accumulation method on a signal received by the portable terminal. The apparatus of claim 9, wherein the channel impulse response obtaining unit obtains the CIR based on the signal received by the portable terminal.
And estimating the channel impulse response using at least one Positioning Reference Symbol (PRS) received by the portable terminal. 10. The method of claim 9, wherein the weight applying unit for applying a weight to the obtained channel impulse response,
A buffer for storing the obtained channel impulse response until all successive subframes have been transmitted;
A channel impulse response average value calculator calculating an average of the obtained channel impulse responses stored in the buffer; and
And a channel impulse response variance calculator for calculating a variance of the obtained channel impulse response stored in the buffer. The method of claim 15, wherein the channel impulse response dispersion value calculation unit,
A portable terminal for estimating position by using the observed time difference of arrival, characterized by calculating a variance between an average channel impulse response value obtained by using a differential accumulation method and a channel impulse response value of each symbol.

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