KR100846867B1 - Method for compensating location estimation in beamforming based system - Google Patents

Abstract

The present invention relates to a method for compensating for a location estimation error generated by a repeater in a beamforming-based system, and after estimating the position of a terminal by a time difference of arrival (TDOA) method, an Angle of arrival The presence or absence of a repeater path is detected in the method to correct the estimated position of the terminal. In a beamforming-based system in which a repeater is located between a base station and a terminal, the position correction method according to the present invention comprises the steps of: converting and transmitting the angle of arrival of the terminal signal at each repeater; Estimating the angle of arrival by detecting an uplink channel at the base station; Determining the presence or absence of a repeater path using the estimated arrival angle; Compensating for the position estimate in the system according to the determined repeater path.

Beamforming based system, UE location estimation, angle of arrival, TDOA, repeater.

Description

Error Estimation Method for Position Estimation in Beamforming-based System {METHOD FOR COMPENSATING LOCATION ESTIMATION IN BEAMFORMING BASED SYSTEM}

1 is a view showing a position estimation method using the OTDOA method

2 is a diagram showing an error in position estimation of the OTDOA method when a repeater is present.

3 is a diagram showing a cell structure for calculating a position estimation error by a repeater.

4 is a diagram showing the structure of a multidrop optical repeater.

5 is a flowchart illustrating a method of compensating for a location estimation error according to the present invention.

6 shows the structure of an adaptive beamformer.

7 is a structure of an optical repeater applied to the present invention

8 and 9 illustrate simulation results of estimating a spatial spectrum of a path in a fading environment.

10 is a diagram illustrating an OTDOA signaling operation.

******* Description of the symbols for the main parts of the drawing ********

20: mixer

The present invention relates to a location based service of a beamforming-based system, and more particularly, to a method capable of compensating for a location estimation error of a terminal by an optical repeater.

DESCRIPTION OF THE BACKGROUND ART

In the mobile communication system, a service that provides various information related to a user's location through wired / wireless communication to a mobile user is called a location based service (LBS). In particular, the U.S. Federal Communications Commission (FCC) is a system that enables wireless network service providers such as Cellular, PCS, and Special Mobile Radio (SMR) to automatically inform the system of the location of E911 (Emergency 911) subscribers using mobile phones. It is compulsory to provide emergency caller location tracking service, and Korea is currently seeking legislation and activation plans related to location-based services. In the US and Europe, the LBS market is already active in the country, and the establishment of a system related to location information and the number of LBS-related companies are rapidly increasing.

Standardization organizations for location-based services around the world include the International Standard Organization (ISO), the Open GIS Consurtium (OGC), the 3rd Generation Partnership Project (3GPP), the Location Interoperability Forum (LIF), and the Wireless Application Protocol (WAP) forum. In addition, many location estimation techniques have been studied by the standardization bodies.                         

The location estimation method is largely divided into a handset-based or UE-based mode and a network-based mode or UE-assisted mode. The terminal-based method is a technique for estimating the position of the terminal using a GPS signal, and the network-based method is a technique for estimating the position using the arrival time of the signal, the arrival direction of the signal and the three of the signal.

The terminal-based method requires accurate time synchronization between the base station and the terminal and requires a global positioning system (GPS). However, incorporating GPS antennas and receivers in all terminals for the terminal-based method is disadvantageous in terms of cost, and in particular, in an environment in which satellite signals cannot be received, location tracking is difficult. In addition, in order to protect personal privacy, GPS is not legalized yet.

The network-based method does not require an additional device in the terminal, there is an advantage that the current terminal can be used as it is. The method of estimating the location by measuring the arrival time of a radio wave (signal) among network-based methods includes a method of measuring a time of arrival (TOA) between a terminal and a base station at a terminal, and a propagation time from two base stations. There is a method of measuring the time difference of arrival (TDOA). There is also a method of determining the direction of the signal source in the receiver by measuring the direction of arrival (DOA) or the angle of arrival (AOA) of the signal transmitted from the terminal. However, since the method using the direction of the signal assumes a line of sight (LOS), the accuracy of the estimation is inferior in a multipath environment.

Recommendations relating to terminal location estimation in 3G asynchronous systems suggest three methods as the standard for location estimation techniques. That is, the recommendation suggests cell ID based method, OTDOA method and Network-assisted GPS method as the location estimation method provided by UTRAN.

The cell ID based method has a disadvantage in that precision is too low because the location estimation error is in a cell unit. In addition, since GPS is not considered, this patent basically describes position estimation based on an Observed Time Difference Of Arrival (OTDOA) scheme.

Although the present invention is not limited to the third generation asynchronous system, since the contents of the OTDOA based location estimation are basically included, the third generation asynchronous system in which the OTDOA method is proposed in the standard will be described as an example.

The OTDOA method basically requires a terminal and three or more base stations for position estimation. The base station estimates the position of the terminal by receiving a measurement value of "SFN-SFN observed time difference" from the terminal, measuring the relative difference in propagation time to several base stations, and then checking the intersection of the hyperbola due to the distance difference. In this case, the SFN is a cell system frame number counter and is a unique counter for classifying frames of physical channels in a cell, and the SFN value may have a range of 0 to 4095.

Since the base station transmits an SFN through a broadcast channel (BCH), when the UE searches for neighboring base stations using an IPDL interval, the terminal may receive an SFN value for each. After all, since the difference between these values can be the relative distance information between the terminal and the various base stations, the SFN-SFN time difference is the basis of the position estimation.

1 is a diagram illustrating an OTDOA location estimation technique.

As shown in FIG. 1, one base station can estimate the position of the terminal at the intersection of hyperbola only when there is time difference information about two or more base stations. Although FIG. 1 assumes a two-dimensional cell structure for convenience, it is apparent that the position of the terminal is estimated by the intersection of a hyperboloid in a three-dimensional space.

)을 측정하면 계산할 수 있으며, 실제로 상기 시간차(

)는 단말이 측정한 SFN-SFN 시간차에 의해 결정된다.First, the relative distance difference R _{i, j} between the user equipment and the two base stations (i, _j ) is a propagation time difference between the base stations as shown in Equation (1).

) Can be calculated and actually the time difference (

) Is determined by the SFN-SFN time difference measured by the UE.

----------------------식(1)

---------------------- Equation (1)

가 되는 모든 가능한 위치이며, R₁-R₃쌍곡선은 SFN 시간차가

가 될 수 있는 위치이다. 따라서, 상기 두 쌍곡선이 만나는 위치에 단말이 위치하는 것으로 추정할 수 있다. Here, the R ₁ -R ₂ hyperbola has a time difference of SFN ₁ -SFN ₂

Where all possible positions R ₁ -R ₃ hyperbola have a SFN time difference

This is where we can be. Therefore, it can be estimated that the terminal is located at the position where the two hyperbolas meet.

In the OTDOA method, since no absolute time synchronization is required between the base station and the terminal, no additional hardware or software is required for the terminal. Therefore, the Radio Network Controller (RNC) can estimate the position of the terminal only by calculating the intersection point of the hyperbola based on the measurement value of the terminal.

On the other hand, the repeater is a device that can provide a higher quality service to the user by amplifying the weak radio between the base station and the terminal. The repeater developed as a substitute for the base station improves the coverage of the system and improves the call quality in the area and basement where the base station signal cannot reach or in the poor radio environment. In particular, the repeater is a device that can minimize the investment cost of mobile operators because the installation and maintenance cost is cheaper than the base station and easy to secure the site.

However, in general, the system cannot determine whether the signal received from the terminal has passed through the repeater or is directly received from the terminal. Accordingly, when the location estimation is performed using the OTDOA method, the base station actually determines the signal received from the repeater as a signal directly received from the terminal, which may cause an error in the location estimation.

2 is a diagram illustrating an error in OTDOA position estimation when a repeater is present.

쌍곡면과

쌍곡면이 만나는 지점에 존재한다고 추정할 수 밖에 없다. Since the environment shown in FIG. 2 assumes that the terminal receives the signal of the base station 1 through the repeater 1, the actual position of the terminal is considered as the center of the repeater R ₁ -R ₂ hyperbolic surface and R ₁ -R ₃ hyperbolic. It is the point where the faces meet. However, since the base station assumes that the received signal has arrived directly without passing through the repeater,

Hyperbolic

We can only assume that the hyperbolic surface exists at the point where it meets.

In general, since a repeater is used near most base stations, if the terminal signal via the repeater is not corrected, an error is always generated in the position estimation, and the accuracy of the position estimation is greatly deteriorated. The location estimation error depends on the relative position between base stations, base station-base station distance, base station-relay period distance, and repeater support radius.

Therefore, the structure as shown in FIG. 3 is assumed to find out how much the position estimation error is. Figure 3 is a cell structure for calculating the position estimation error for the repeater, it was modeled in two dimensions to simplify the analysis. First, each parameter for calculating a position estimation error is defined as follows.

D _BB : distance between base station 1 and base station 2 and distance between base station 1 and base station 3

D _BR : y ₁ -y _R: Distance between base station 1 and repeater 1

● d _MR : Repeater Support Radius

Base station location

● repeater position                         

If it is assumed that the terminal exists within the radius of the repeater 1 connected to the base station 1, the position P (x, y) of the terminal satisfies Equation (1.2).

-------------------------------식(2)

------------------------------- Equation (2)

는 식(3),(4)의 교점으로 구할 수 있다.Deriving the hyperbolic equation from the SFN-SFN time difference measured by the terminal without knowing the presence or absence of a repeater, it is shown in the following equations (3) and (4).

Can be found by the intersection of equations (3) and (4).

------------식(3)

------------ Formula (3)

----------식(4)

---------- Equation (4)

)은 다음의 식(5)와 같이 x, y의 함수로 표현할 수 있다.Intersection that satisfies both equations (3) and (4)

) Can be expressed as a function of x and y as in the following equation (5).

---------------------식(5)

--------------------- Equation (5)

간의 거리

를 최대화하는 P(x, y)에서 최대 추정오차가 발생하며 이를 식으로 나타내면 다음 식(6)과 같이 표현된다. Thus, with P

Distance between

The maximum estimation error occurs at P (x, y) that maximizes, and is expressed as the following equation (6).

------------식(6)

------------ Equation (6)

In Equation (6), the maximum value exists in the maximum radius where the position P (x, y) of the terminal satisfies the equal sign of Equation (2), and simplifies Equation (6) on the assumption that the equal sign of Equation (2) holds. If the following equation (7).

---------------식(7)

--------------- Equation (7)

이다. here,

to be.

위치에 있을 때로서 도 3의 P_max위치에 해당한다. 이 경우 최대 오차는 식(8)과 같이 된다. In the equation (7), the maximum error within the range of y means that the UE

When in position, it corresponds to the position of P _max in FIG. 3. In this case, the maximum error is as shown in equation (8).

-------------------------식(8)

------------------------- Equation (8)

Looking at Equation (8), it can be seen that the position estimation error added by the repeater when the distance between the base stations is constant is proportional to the distance between the base station and the relay period and the repeater support radius. In addition, in the environment where the ratio of d _BR and d _BB is 1/4, the repeater support radius is the maximum error, and in the optical repeater having a large support radius, an error of several km may be additionally generated.

3 is a maximum estimation error obtained only in a specific case, the position estimation error actually depends on how the cell design is made, and the cell structure must be expanded in three dimensions for more accurate analysis. However, even if the cell structure is extended in three dimensions, the maximum estimation error obtained by Equation (8) is almost the same, so that the error range will be large in an optical repeater environment having a large base station-to-medium instrument distance and repeater support radius. It is easy to predict. In addition, when a multi drop type repeater is installed, the error range is further increased.

4 shows a multidrop repeater having a structure in which multiple repeaters can be connected to the repeater.

Referring to FIG. 4, the base station converts the multiple sector signals and the multiple frequency (FA) signals into time signals by converting them into optical signals, and then transmits the received optical signals to the optical repeaters through the optical cables. It is separated, converted to RF signal, amplified high power and transmitted to subscribers. On the contrary, the signal received from the terminal is converted into an optical signal by the optical repeater and transmitted to the base station. In the optical repeater, the system operating sector can be variably assigned and operated, but once the optical repeater is installed, it is fixedly operated as one sector. In a structure in which branches of a multistage branch are connected to a repeater as shown in FIG. 4, lower repeaters may support the same sector as the upper repeater or may support other sectors.

Therefore, in the environment in which the multidrop type repeater is installed, the location estimation error by the OTDOA is larger than the maximum estimation error obtained by Equation (8), which can be a big obstacle in providing the location-based service.

Accordingly, it is an object of the present invention to provide a method for compensating for a location error that can be performed more accurately by compensating for a location error generated by a repeater in a beamforming based system.

In order to achieve the above object, in a beamforming-based system in which a repeater is located between a base station and a terminal, a method for compensating for a position estimation error according to the present invention includes converting and transmitting an angle of arrival of a terminal signal in each repeater. Steps; Estimating the angle of arrival by detecting an uplink channel at the base station; Determining the presence or absence of a repeater path using the estimated arrival angle; Compensating for the position estimate in the system according to the determined repeater path.

Preferably, each repeater converts the angle of arrival of the terminal signal by adjusting the phase for each antenna of the terminal signal.

Preferably, each repeater includes a multi-drop repeater consisting of a plurality of repeaters.

Preferably, the angle of arrival is set to a value that can distinguish each repeater, and the angle of arrival is estimated by a parameter-based spectrum estimation method.

Preferably, the uplink channel is a random access channel (RACH) or a dedicated physical channel (DPCH).

Preferably, the system is a radio network controller (RNC), and performs position estimation of a terminal by using a relative difference (OTDOA) of propagation time from two base stations and then corrects the position estimation.

Hereinafter, preferred embodiments of the present invention will be described in detail.                     

The present invention is applied in an array antenna system in which beamforming is supported. In addition, the present invention basically estimates the position of the terminal using the TDOA method, and additionally performs location estimation by detecting the presence or absence of a repeater path using the AOA estimation technique. The present invention can be applied to any beamforming supported system regardless of the multiplexing scheme (CDMA or TDMA). For the sake of convenience, the third generation asynchronous system will be described as an example.

Provides a method and system for more accurate location estimation by compensating for the location error of the terminal by the repeater when providing a location-based service in an array antenna system that supports beam-forming do.

In the 3rd generation asynchronous system, the terminal periodically performs a location update to update the location, and the location registration is performed through a RACH (Random Access Channel) channel. Accordingly, the UE periodically transmits an RACH signal through an uplink channel, which corresponds to a physical random access channel (PRACH) of a physical channel. The same concept exists in the IS-95 family of services for access channels. Since the base station always detects the RACH channel, if it is possible to determine whether the corresponding signal (RACH signal) is received through a specific repeater, it is possible to predict the path of the uplink signal of the terminal. Of course, if the call is successful and the dedicated physical channel (DPCH) is connected, the DPCH channel may be received to predict the repeater path for the UE signal.

In the present invention, the angle of arrival is estimated through the DPCH channel when the call is connected using the above characteristics, and the angle of arrival is estimated through the access channel (RACH channel) which is periodically transmitted when the terminal is powered on. The present invention proposes a method for determining which repeater a terminal has been through.

When the network design is completed and the base station system is installed, the base station and repeater are located in a fixed place. That is, the base station may store the position of the repeater connected to itself in a database form in advance. The digital optical repeater has a structure that greatly increases the relay distance by converting the IF signal of the base station into a digital signal and transmitting it through the optical cable.

The base station performs time division multiplexing (TDM) on IF signals corresponding to several sectors and antennas and transmits them sequentially to the repeater through an optical cable, and the repeater amplifies the corresponding signals and relays them to the shadow area of the terminal. On the contrary, the signal transmitted from the terminal of the shadow area is converted to digital at the IF terminal of the repeater and is also time division multiplexed (TDM) and transmitted to the base station through the optical cable.

The present invention is to multiply the uplink signal digitally converted from the repeater by the inherent phase so that the angle of arrival of the received signal always has a specific range to detect which repeater terminal signal is passed to the base station Suggest.

The present invention may be specifically implemented through four steps. That is, as shown in FIG. 5, the method for compensating for a position estimation error according to the present invention includes converting an IF signal of a sector in charge in each repeater into a specific AOA range unique to the repeater (S10), Estimating the angle of arrival using the received signal at the base station (S11), determining whether the received signal has passed through the repeater based on the estimated angle of arrival (S12), and the position estimation error according to the determination result Compensating for may include a step (S13). Before describing the individual steps of the present invention, a simple concept of an adaptive beamformer will be introduced and terms will be defined.

6 is a general adaptive beamformer structure for obtaining the beam weight of the beamformer. In FIG. 6, a uniform linear array antenna is assumed, and an angle between a plane perpendicular to the antenna column and a receiving plane wave is defined as Φ. In addition, when the wavelength of the radio wave is λ and the distance between the antennas is d, the electrical angle θ defined by the direction of arrival (DOA) is expressed by the following equation (9).

------------식(9)

------------ Equation (9)

At this time, since the number of antennas is M, M × 1 steering vector s (θ) is defined as in Equation (10).

-----------------식(10)

Equation (10)

If u (n) is a signal transmitted from a transmitter and x (n) is a received signal, M × 1 vector x (n) can be expressed as Equation (11).

---------식(11)

--------- Equation (11)

인 AWGN 잡음신호이다. 또한, 빔포머 출력신호 y(n)은 식 (12)과 같이 표현되며, w(n)은 M×1 빔계 수 벡터이다.In this case, z (n) is an M × 1 noise vector, and each element has a variance

AWGN noise signal. Further, the beamformer output signal y (n) is expressed as in Equation (12), where w (n) is an M × 1 beam coefficient vector.

--------------식(12)

-------------- Formula (12)

The adaptive beamformer has a structure in which a beam coefficient is adaptively formed on the input signal of the receiver by using the reference signal d (n) and the beamformer output. There are various algorithms for obtaining the coefficient.

Step of converting the angle of arrival in the repeater (S10)

Repeaters connected to beamforming systems are equipped with array antennas, just like base stations. Since the base station is located at the center of several sectors as shown in FIG. 1, one base station is responsible for several sectors. In the three-sector system, the array antenna of each sector covers the signal of -60 ^° ~ 60 ^° based on the direction perpendicular to the antenna string. In the case of the six-sector system, the signal of -30 ^° ~ 30 ^° is applied. Cover it.

은 식 (13)으로 표현된다. In the six-sector system, the angle of arrival can be converted as if the angle of arrival is different from the range of -30 ^° to 30 ^° by adjusting the phase of each antenna of the received signal inside the digital optical repeater connected to each sector. This is because the optical repeater can process the digital IF signal so that the phase of the signal can be rotated for each antenna. For example, 30 ^° ~ 90 ^° or -90 ^° ~ 180 ^° is possible. That is, a unique arrival angle can be assigned to up to five optical repeaters per sector of a base station, which means that a unique arrival angle can be set in the repeater. Steering vector of the kth repeater connected to a particular sector of the base station

Is represented by equation (13).

---------------식(13)

--------------- Equation (13)

In Eq. (13), o is not a normal vector product, but a product of vector elements. Therefore, for the six-sector system, the angle of arrival range of the repeater is as shown in Eq. (14).

----------------------식(14)

Equation (14)

로서 중계기 고유의 도래각을 만드는 기준이 된다. in this case

It is a standard to make the angle of arrival unique to the repeater.

7 is a structure of an optical repeater applied to the present invention.

를 곱하여 섹터의 IF신호를 중계기 고유의 특정 도래각으로 변환한다. 만약 3섹터 시스템의 경우라면 기지국 1개의 섹터당 2개의 중계기를 구분할 수 있으며, 기지국 1개 단위로 계산하면 6개의 중계기를 구분할 수 있다. 왜냐하면 기지국에서는 기하학적으로 어떤 섹터에 어떤 중계기가 연결되어 있는지 미리 알고 있기 때문이다. 그런데, 때로는 기지국 1개의 섹터에 2개 이상의 중계기가 연결될 수 있는데, 이런 환경에서는 모든 중계기를 구분할 수 없는 경우가 발생한다. 이런 환경에서는 위치추정의 오류를 제일 많이 유발하는 위치의 중계기를 우선하여 선택한다. Referring to FIG. 7, the mixer 20 may apply a digital IF signal converted from an ADC.

Multiply by to convert the sector's IF signal to a repeater specific specific angle of arrival. In the case of a three-sector system, two repeaters can be distinguished per sector of one base station, and six repeaters can be distinguished when calculated in units of one base station. This is because the base station knows in advance which relay is connected to which sector. However, sometimes two or more repeaters may be connected to one sector of a base station. In such an environment, all repeaters cannot be distinguished. In this environment, the position relay that gives the most error in position estimation is selected first.

Estimate the angle of arrival at the base station (S11)

In general, there are many algorithms for estimating angle of arrival. In addition, if adaptive beamforming is used, it may be possible to convert the angle of arrival with a beam weight vector derived from the beamforming algorithm itself. Of course, if the beamforming algorithm is used as it is without a separate angle of arrival estimation algorithm, it is possible to estimate only the DPCH channel. This is because the beamforming algorithm is generally applied to the DPCH channel. Therefore, when performing location-based services in the RACH channel, a separate angle of arrival estimation algorithm should be used when receiving the RACH preamble.

Arrival angle estimation algorithms that can be used in array antennas include the classic method, parametric spectrum estimation technique, minimum variance distortionless response (MVDR), multiple signal classification (MUSIC), and minimum norm algorithm. The present invention briefly introduces such a spatial spectrum estimation algorithm and shows the simulation results in a fading environment.

In all four methods, as shown in Equation (15), a correlation matrix R _xx between M × M antennas for the received signal x (n) should be obtained.

-----------------------식(15)

----------------------- Equation (15)

Equation (15) is a theoretical value defined as the ensemble mean, and in practice, R _xx should be estimated from the received signal of each antenna, and generally, the sample average is taken as in Equation (16).

-----------------------식(16)

----------------------- Equation (16)

는 A에 의한 샘플평균 개념의 M×M 상관행렬이다. 상기

행렬의 원소가 되는 안테나간 상관값은 각각 N-M개 샘플의 평균효과가 있다.Here, A is a matrix produced by the received signal samples as shown in equation (17),

Is the M × M correlation matrix of the sample mean concept by A. remind

The inter-antenna correlation value, which is an element of the matrix, has an average effect of NM samples.

-----------식(17)

----------- Equation (17)

Classic method

일 때(표현에 따라서는

일 수도 있음) 빔포머 출력 전력이 최대가 되고, 다른 방향으로 w가 형성되면 출력전력이 작아진다는 성질을 이용하여 다음 식(18)과 같이 공간 스펙트럼을 정의한다.The classical method, also known as the delay-and-sum method, calculates the most basic spectral estimates. If the signal is received in the direction, the beam coefficient w

When (depending on expression

The spatial spectrum is defined as shown in Equation (18) by using the property that the beamformer output power is maximum and the output power is small when w is formed in another direction.

--------------------식(18)

-------------------- Equation (18)

2.MVDR method

값이 1이라는 제한조건을 가지고 전체 출력전력을 최소화하는 계수를 구한 다음 다시 출력전력을 구하면 그 값은 공간상의 스펙트럼 추정치가 될 수 있다. 왜냐하면 계수를

방향으로 최적화한 후에 입력 신호의 DOA를 바꾸어 보면 DOA가

일 때 출력전력이 최대가 되며 다른 방향의 DOA에 대해서는 출력전력이 작아지기 때문이다. 결과적으로 MVDR 스펙트럼은 식 (19)과 같이 된다.Output of signal direction under the assumption that the signal is in the DOA direction

With a constraint of 1, obtain a coefficient that minimizes the total output power, then find the output power again, which can be a spatial spectral estimate. Because the coefficient

After optimizing in the direction, changing the DOA of the input signal

This is because the output power becomes the maximum when the output power decreases for DOA in the other direction. As a result, the MVDR spectrum becomes as shown in equation (19).

-----------------------식(19)

----------------------- Equation (19)

3.MUSIC method

는 M×M상관행렬(

)의 고유값(eigenvalue)이고,

는

의 고유벡터(eigenvector)라 가정하자. 만약 안테나 개수 M보다 작은 값인 L개의 독립적인 신호원이 존재하여 각각이 고유의 DOA를 갖는다고 하면, V의 고유벡터들이 생성(span)하는 공간은 다음과 같이 두 개의 부공간(subspace)로 나눌 수 있다. 하나는 L차원의 신호+잡음 부공간이고, 또 하나는 잡음 부공간으로 M-L 차원이 된다. 다시 말하면 L개의 신호원에 해당하는 steering 벡터

에 의해 생성되는 부공간과 크기가 작은 M-L개의 고유값에 해당하는 고유벡터(

)로 생성되는 잡음 부공간으로 분리할 수 있음을 의미한다. 그리고 두 부공간은 서로 직교(orthogonal)하다는 것이 증명되어 있으므로, 이 특성을 이용하면 새로운 공간 스펙트럼의 추정치를 만들 수 있으며 이것이 식(20)에 도시된 MUSIC 스펙트럼이다.first,

Is the M × M correlation matrix (

) Is the eigenvalue of

Is

Suppose that is the eigenvector of. If there are L independent signal sources that are smaller than the number of antennas M and each has its own DOA, the space generated by the eigenvectors of V is divided into two subspaces as follows. Can be. One is the L-dimensional signal + noise subspace, and the other is the noise subspace in ML dimension. In other words, a steering vector corresponding to L signal sources

Eigenvectors corresponding to the small spaces and small ML eigenvalues generated by

It can be separated into the noise subspace generated by). And since the two subspaces have been proved to be orthogonal to each other, this property can be used to make an estimate of the new spatial spectrum, which is the MUSIC spectrum shown in equation (20).

------------식(20)

------------ Equation (20)

4.Minimum-norm method

에 속하는 벡터여야 하며, 첫번째 원소의 값이 1이면서 이런 조건을 만족하는 벡터 중 norm이 최소가 되어야 한다.

을 편의상 식 (21)과 같이 부분행렬로 나타낸다고 가정하면 minimum norm 스펙트럼은 식 (22)과 같이 표현할 수 있다.In the MUSIC algorithm, DOA was estimated by finding all the ML vectors underlying the noise subspace and the steering vector near zero, but the minimum norm algorithm selects only one suitable vector ( a) from the basis of the noise subspace. do. a is the noise subspace

It must be a vector belonging to, and the first element must have a value of 1 and norm must be the minimum among the vectors satisfying this condition.

For convenience, assuming that the sub-matrix is represented as in (21), the minimum norm spectrum can be expressed as in (22).

-------------------------------식(21)

------------------------------- Equation (21)

은 M×(M-L) 행렬,

은 1×(M-L) 행열이며,

은 (M-1)×(M-L) 향렬이다. here,

Is an M × (ML) matrix,

Is a 1 × (ML) matrix,

Is (M-1) x (ML) alignment.

, where

---------식(22)

, where

--------- Equation (22)

The MUSIC and Mimimum norm algorithms are spectral estimation methods with relatively good signal resolution. Of course, as mentioned above, the DPCH channel can be converted to the angle of arrival using a weight vector derived by any adaptive beamforming method as well as the above-mentioned spectrum estimation-based angle of arrival estimation method. In order to do this, either method may be used.

5. Simulation Results

The simulation was performed in a WCDMA based 3G asynchronous system environment. The environment (condition) of the simulation is shown in [Table 1]. Especially, the simulation was performed for 3GPP uplink DPCH channel. The channel environment of the experiment was a case 1 fading channel, which is part of a channel defined for base station performance test in 3GPP, and the channel profile of case 1 is shown in the following [Table 2]. There are two multipaths and the second multipath has 10dB less power relative to the main path.

Table 1

Contents Remarks Antenna number 4  DPDCH Physical Channel Bit Rate 60 kbps Uncoded simulation Diffusion Factor (SF) 64 Source data patterns Random  DPCCH Slot format 0 DPCCH non-pilot field All 0 Number of Pilots: 6 Number of TPCs: 2 Number of TFCIs: 2 Amplitude ratio of DPCCH / DPDCH 11/15 Power Ratio = -2.69dB

[Table 2]

Case 1, speed 3km / h Relative delay [ns] Average power [dB] 0 0 976 -10

8 and 9 show spatial spectra estimated by the above four algorithms when the angles of arrival are 10 °, 20 °, 30 °, and 40 °, respectively, in an environment with a channel EbNo of 0 dB.

In particular, FIG. 8 is a diagram illustrating the spatial spectrum of the first path (0 dB) in case 1 fading environment, and FIG. 9 is a diagram illustrating the spatial spectrum of the second path (-10 dB). That is, FIG. 8 estimates a spatial spectrum using dispreading data for each antenna from the first finger, and FIG. 9 estimates the angle of arrival for each algorithm using the despreading data from the second finger. .

As can be seen in FIG. 8, the first finger has a relatively large reception EbNo, resulting in a difference in resolution capability of the Classic and MVDR schemes, and also a difference in resolution capability of the MUSIC and Minimum norm algorithms. As shown in FIG. 9, the MUSIC algorithm has a lower resolution for a finger having a very low EbNo. However, the results of several independent trials show that the estimation value is smaller and the dispersion characteristics of the estimation are better.

Determining a repeater path at the base station based on the estimated angle of arrival

As described above, since the repeaters are divided into the ranges of the angles of arrival that each repeater can have, it is possible to know through which relay paths the received signals naturally arrive by estimating the angles of arrival at each sector antenna of the base station. In the six-sector base station, if the angle of arrival of the signal received through the array antenna for each sector is -30 ^° to 30 ^° , it may be determined that the signal does not go through the repeater, and if it is 30 ^° to 90 ^° , the repeater 1, 150 ^° to If it is 210 ^°, it can be predicted as a signal via repeater 3.

The method of estimating the position of the original arrival angle was not widely used because there is a possibility of incorrectly determining the direction of the terminal in the absence of LOS. However, if the angle of arrival estimation is applied to determine only the presence or absence of a repeater path as in the present invention, there is no problem even if there is no LOS with the terminal within a radius supported by the repeater. This is because both LOS paths and multipaths will be within the inherent angle of arrival range of the repeater.

Once the signal path of the user is determined, the base station transmits the measurement data to the radio network controller (RNC) to provide additional information to help estimate the OTDOA location.

Terminal location estimation and correction step

10 is a diagram illustrating signaling when using the OTDOA location estimation method.

Referring to FIG. 10, an SFN-SFN difference between various base stations is included in the OTDOA measurement report S20 sent by the UE to the RNC. In addition to the location-based service of the OTDOA method, the present invention uses a method of estimating the angle of arrival through which relay the signal of the user requesting the service has arrived at the base station. Therefore, as shown in FIG. 10, if the base station transmits repeater path information in addition to the measurement data sent to the serving RNC (RNC) through step S21, the RNC may eliminate an error in position estimation by the repeater. There will be. That is, the USER_ID requesting the service and the repeater_ID passed by the signal of the user may be transmitted to the RNC together.

 As described above, the present invention provides a method for more accurate position estimation by compensating for a position estimation error generated by an optical repeater in a beamforming based system. In particular, the present invention performs the step of converting the received signal in each repeater to a specific AOA range unique to the repeater, the base station estimates the arrival angle through the received signal and the repeater of the received signal from the estimated arrival angle By determining the path, it is possible to compensate the position estimation error by the repeater. Therefore, the present invention can greatly improve the accuracy of the location estimation, and there is an effect that can smoothly support location-based services that are rapidly increasing demand.

In addition, although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary and will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (20)

In a beamforming based system in which a repeater is located between a base station and a terminal, Receiving a signal from a terminal through an uplink channel at the repeater; Converting the range of the terminal signal into a unique angle of arrival; Transmitting the terminal signal converted into the unique angle of arrival to a base station through an uplink channel; Wherein the transformed unique angle of arrival is used to correct an error generated by the repeater when estimating the position of the terminal. The method of claim 1, wherein the unique angle of arrival is Position estimation correction method characterized in that it is set to a value that can distinguish each repeater. The method of claim 1, wherein each repeater converts an angle of arrival by adjusting a phase for each antenna of the received signal. A method for estimating a location of a terminal in a beamforming based system in which a repeater is located between a base station and a terminal, Receiving a terminal signal converted into a unique angle of arrival from each repeater through an uplink channel; Determining a repeater path through which the terminal signal passes by estimating the angle of arrival of the terminal signal by detecting the uplink channel at the base station; Compensating for the position estimate in the system based on the determined repeater path. The method of claim 4, wherein the repeater Compensation method for position estimation error, characterized in that the angle of arrival is converted by adjusting the phase of each antenna of the terminal signal. The method of claim 4, wherein the repeater Compensation method for position estimation error, characterized in that it comprises a multi-drop repeater consisting of a plurality of repeaters. 7. The method of claim 6, wherein each repeater is distinguished by a unique angle of arrival. The method of claim 4, wherein the angle of arrival is A method for compensating for position estimation error, characterized in that estimated by a parameter based spectrum estimation method. The method of claim 4, wherein the uplink channel A method of compensating for a location estimation error, characterized in that it is a random access channel (RACH) or a dedicated physical channel (DPCH). The system of claim 4 wherein the system is Compensation method for position estimation error, characterized in that the radio network controller (RNC). The system of claim 4 wherein the system is A method of compensating for a location estimation error, characterized in that the location estimation is corrected using a repeater path after performing a location estimation of a terminal using a relative difference between propagation times from two base stations. The method of claim 4, wherein the determined repeater path is Compensation method for position estimation error, characterized in that the repeater ID. In a beamforming based system in which a repeater is located between a base station and a terminal, Receiving a terminal signal converted into a unique angle of arrival by each repeater from each repeater through an uplink channel; Estimating the angle of arrival at a base station; Determining the presence or absence of a repeater path using the estimated arrival angle; And compensating for the position estimate in the system according to the determined repeater path. The method of claim 13, wherein each repeater Compensation method for position estimation error, characterized in that the angle of arrival of the terminal signal is converted by adjusting the phase of each antenna of the terminal signal. The method of claim 13, wherein each repeater Compensation method for position estimation error, characterized in that it comprises a multi-drop repeater consisting of a plurality of repeaters. 14. The method of claim 13, wherein the angle of arrival is set to a value that can distinguish each repeater. The method of claim 13, wherein the angle of arrival is A method for compensating for position estimation error, characterized in that estimated by a parameter based spectrum estimation method. The method of claim 13, wherein the uplink channel A method of compensating for a location estimation error, characterized in that it is a random access channel (RACH) or a dedicated physical channel (DPCH). The system of claim 13, wherein the system is Compensation method for position estimation error, characterized in that the radio network controller (RNC). The system of claim 13, wherein the system is A method of compensating for a location estimation error, comprising performing location estimation of a terminal by using a relative difference between propagation times from two base stations and then correcting the location estimation.

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