KR20180130875A - The method for generating positioning reference signal based on a positioning reference signal pattern to improve positioning performance - Google Patents

Abstract

A base station or a terminal, in a process of generating a positioning reference signal transmitted in a plurality of subframes, uses a positioning reference signal pattern where the position of a PRS symbol is shifted along a subcarrier for each of a plurality of subframes, instead of using the same positioning reference signal pattern for each of the plurality of subframes. Accordingly, the PRS symbol can be evenly allocated to all subcarriers. Therefore, a phenomenon in which some subcarriers are not used can be prevented. So, a phenomenon caused by unnecessary frequency components can be prevented in calculating correlation between a side-peak-received positioning reference signal and a previously stored positioning reference signal. A method for generating a positioning reference signal includes: a step of determining a position positioning signal pattern; and a step of generating a positioning reference signal.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to an apparatus and a method for generating a position reference signal based on a position reference signal pattern for improving position measurement performance,

The present invention relates to a wireless communication system.

Recently, the United States Federal Communications Commission (US FCC) has introduced new regulatory requirements for indoor positioning in cellular systems for some emergency services (eg, Enhanced 911 (E911, Enhanced 911)). requirements. According to the regulatory requirement, the cellular system should more accurately measure the vertical position and the horizontal position. For example, a cellular system would have to measure 70% of calls within 50 meters of horizontal accuracy out of all wireless 911 calls by 2020, and 80% of wireless users by 2021 would have a reasonable accuracy of z - Provide z-axis technology.

Accordingly, the Third Generation Partnership Project (3GPP) has launched a research item for improvement of indoor positioning in an LTE (Advanced Terminology) -Advanced system (Release 13). (CID), enhanced CID, angle of arrival (AoA), time difference of arrival (OTDOA), observed TDOA (OTDOA), uplink TDOA (UTDOA), assisted- GNSS), RF ngerprint, and so on. To more accurately measure the location of a target device (e.g., a terminal), some of the location methods may be applied together (e.g., CID and OTDOA).

The present invention proposes a method of generating a position reference signal used for measuring a position of a terminal using a position reference signal pattern and a wireless communication system to which the method is applied.

For a plurality of subframes to which a position reference signal is transmitted, the present invention changes the position reference signal pattern for each subframe so that the terminal receiving the position reference signal can more accurately measure the distance between the terminal and the base station, A method of generating a signal is proposed.

According to an embodiment, there is provided a method of generating a position reference signal (PRS) performed by a base station, the method comprising: transmitting a symbol of a position reference signal used for determining a distance between the terminal and the base station, Determining a position reference signal pattern indicating how to allocate subcarriers that are used frequencies, in units of subframes, which is a time unit for transmitting symbols; And allocating a symbol of the position reference signal to the subcarriers based on the position reference signal pattern to generate a position reference signal transmitted to the terminal using a plurality of subframes, A position reference signal generation method for changing the position reference signal pattern for each of the plurality of subframes is provided.

According to an embodiment, the generating step may include shifting a position of a symbol of the position reference signal according to the number allocated to each of the plurality of subframes along the subcarriers to change the position reference signal pattern A method of generating a position reference signal is provided.

According to another embodiment of the present invention, the generating of the position reference signal includes changing the position reference signal pattern so that the number of symbols of the position reference signal allocated to each of the subcarriers is the same.

According to an embodiment, the generating step is provided with a position reference signal generating method for changing the position reference signal pattern so that symbols of the same number of the position reference signals are allocated to each of the plurality of subframes.

According to an embodiment, the number of symbols of the position reference signal included in the position reference signal pattern is determined based on a period of a cyclic prefix (CP) added between the symbols to eliminate intersymbol interference A method of transmitting a position reference signal is provided.

According to an embodiment of the present invention, a position reference signal used to measure a position of a terminal can be generated using a position reference signal pattern.

According to an embodiment of the present invention, a position reference signal is generated in accordance with a position reference signal pattern changed for each subframe for a plurality of subframes in which a position reference signal is transmitted, And the distance between the base stations can be more accurately measured.

1 is a diagram illustrating a structure of a wireless communication system according to an embodiment.
2 is a diagram illustrating an example of a position reference signal pattern determined by the position reference signal generating method according to an embodiment.
3 is a diagram illustrating position reference signal patterns applied to successive PRS subframes in one embodiment of a wireless communication system using a conventional CP.
4 is a diagram illustrating position reference signal patterns applied to successive PRS subframes in one embodiment of a wireless communication system using an extended CP.
5 is a flowchart illustrating an operation performed by a UE and a Node B to which the position reference signal generating method according to an embodiment is applied.

It is to be understood that the specific structural or functional descriptions of embodiments of the present invention disclosed herein are presented for the purpose of describing embodiments only in accordance with the concepts of the present invention, May be embodied in various forms and are not limited to the embodiments described herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. However, it is not intended to limit the embodiments according to the concepts of the present invention to the specific disclosure forms, but includes changes, equivalents, or alternatives falling within the spirit and scope of the present invention.

The terms first, second, or the like may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example without departing from the scope of the right according to the concept of the present invention, the first element being referred to as the second element, Similarly, the second component may also be referred to as the first component.

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 an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Expressions that describe the relationship between components, for example, "between" and "immediately" or "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms " comprises ", or " having ", and the like, are used to specify one or more of the features, numbers, steps, operations, elements, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, the scope of the patent application is not limited or limited by these embodiments. Like reference symbols in the drawings denote like elements.

1 is a diagram illustrating a structure of a wireless communication system according to an embodiment. Referring to FIG. 1, a wireless communication system may include one or more terminals 110 or one or more base stations 120, 130, 140. The terminal 110 is a device that a user of a wireless communication system carries to access a wireless communication system and is a device such as a smart phone, a smart pad, a PDA (Personal Digital Assistance), a laptop computer, a desktop, Lt; / RTI > The terminal 110 can transmit and receive a radio signal of a sub carrier, which is a frequency supported by the wireless communication system. A wireless communication system may support one or more subcarriers.

The base stations 120, 130 and 140 are devices for connecting the terminal 110 to the wireless communication system and may receive a radio signal of the terminal 110 or transmit a radio signal to the terminal 110. The base stations 120, 130, and 140 may be eNodeBs (enhanced NodeBs).

The position reference signal (PRS) is a radio signal used for estimating or determining the position of the UE 110. The base stations 120, 130 and 140 of the wireless communication system according to an exemplary embodiment may transmit the position reference signals along the downlink from the base stations 120, 130 and 140 to the terminal 110. According to another embodiment, the terminal 110 of the wireless communication system may transmit a position reference signal along the uplink from the terminal 110 to the base station 120, 130, 140.

The position of the UE 110 can be determined using the time delay generated when the position reference signal is transmitted (time delay estimation method). Assume that a position reference signal is transmitted along the downlink. Referring to FIG. 1, the BS 120 may transmit a data symbol, which is a symbol of a previously allocated position reference signal, to the UE 110. A symbol is an information unit of a radio signal, and is a basic unit of modulation, coding, transmission, and detection.

The UE 110 time-correlates a subcarrier and a subframe of a symbol of a received position reference signal with a reference pattern to generate a received signal time difference (RSTD) Can be calculated. The UE 110 may perform the operation of calculating the RSTD for the remaining base stations 130 and 140 as well. That is, the terminal 110 can calculate the RSTD of each of the neighboring base stations 120, 130, and 140. Based on the multilateration technique, which is a method of determining the geometric location from the intersection of multiple surfaces, the RSTD for each of the measured base stations 120, 130, As shown in FIG.

Thus, accurately estimating the time delay information (e.g., RSTD) of each of the base stations 120, 130, and 140 can affect the positioning accuracy of the terminal 110. [ In order to more accurately measure the time delay of the position reference signal, the base stations 120, 130, 140 may perform a position reference signal generation method according to one embodiment or may include a position reference signal generation device according to an embodiment .

More specifically, a position reference signal may be generated by assigning symbols of a position reference signal to subcarriers. For a subframe that is a time unit for transmitting a symbol, the operation of assigning symbols of a position reference signal to subcarriers may be performed for a plurality of subframes. When allocating the symbols of the position reference signal to the subcarriers, a position reference signal pattern may be used in which the symbols of the position reference signals are allocated to the subcarriers in units of subframes. Since the position reference signal pattern indicates the symbol allocation in units of subframes, the position reference signal pattern can be applied to each of a plurality of subframes in which the position reference signal is transmitted.

In particular, the base stations 120, 130, and 140 may apply a position reference signal pattern applied to each of a plurality of subframes for each subframe. Thus, the symbols of the position reference signal may be assigned to subcarriers in different patterns in a plurality of subframes. Hereinafter, how a position reference signal pattern in a subframe unit is generated or determined will be described. Next, how a position reference signal pattern is changed in each subframe will be described.

2 is a diagram illustrating an example of a position reference signal pattern determined by the position reference signal generating method according to an embodiment. 2, a symbol allocation of a position reference signal (i.e., a position reference signal pattern) in a resource block (RB) of a single subframe for each of a normal CP (normal cyclic prefix) and an extended CP (extended CP) Lt; / RTI > The horizontal axis of the position reference signal pattern 210 and the position reference signal pattern 220 represents two slots (n _slot ) and an OFDM symbol number (l) included in the resource block, .

The cyclic prefix (CP) is added between symbols to eliminate inter-symbol interference (ISI). An extended CP having a longer CP period than that of a normal CP is used to eliminate intersymbol interference . The position reference signal pattern 210 indicates a pattern in which a symbol of a position reference signal (hereinafter referred to as PRS symbol) is arranged in a general CP. The position reference signal pattern 220 indicates a pattern in which the PRS symbol is arranged in the extended CP. The number of PRS symbols of the position reference signal pattern 220 is larger than the number of PRS symbols of the position reference signal pattern 210 because the CP period of the extended CP is longer than the CP. Lt; RTI ID = 0.0 > PRS < / RTI >

In order to reduce interference with neighbor cells, that is, interference with a radio signal of a neighboring base station, a subframe including a position reference signal (hereinafter referred to as a PRS subframe) may not include PDSCH data. The PRS subframe may include Physical Downlink Control Channel (PDCCH) data. Referring to FIG. 2, a CRS symbol (hereinafter referred to as a CRS symbol) used for identifying a base station may be allocated to a PRS subframe.

Depending on whether the wireless communication system uses a normal CP or an extended CP, the PRS symbol and the CRS symbol are allocated to the subcarriers according to the position reference signal pattern 210 or the position reference signal pattern 220 in a single subframe . Referring to FIG. 2, PRS symbols may be arranged in a diagonal way between CRS symbols.

A cell-specific frequency shift can be applied to the position reference signal patterns 210 and 220 so that the position reference signals generated at different base stations do not collide with each other in the time domain and the frequency domain. The cell specific frequency shift is to shift the frequency using a remainder (PCI modulo 6) that divides the physical cell identifier (PCI) by six. In other words, the position of the PRS symbol and the CRS symbol in the position reference signal pattern 210, 220 can be determined based on the identifier of the base station. Therefore, since the remainder obtained by dividing the identifier of the base station by six is used, up to six adjacent base stations can generate the position reference signals of different patterns. (PRS muting) as well as cell specific frequency shift so that position reference signals generated at different base stations do not collide with each other in the time domain and the frequency domain when the BSs generating the position reference signals are dense ) Can be used. PRS muting can reduce interference between adjacent cells by muting the position reference signal based on a periodic muting pattern.

The position reference signal may comprise a plurality of consecutive PRS subframes and may be periodically transmitted. For example, one position reference signal may consist of six consecutive PRS subframes and the position reference signal may be transmitted every 160, 320, 640 and 1280 milliseconds. In Time Division Duplex (TDD) mode, the uplink subframe and other special frames may not include the PRS.

Assume that the base station uses a normal CP. In a single subframe, the base station may use the position reference signal pattern 210 to assign PRS symbols and CRS symbols to subcarriers. If the position reference signal includes consecutive PRS subframes, the base station performs the operation of assigning PRS symbols and CRS symbols to subcarriers using the position reference signal pattern 210 for successive PRS subframes . In particular, when the operation of assigning the PRS symbol and the CRS symbol to the subcarriers in the current PRS subframe is completed, the base station can change the position reference signal pattern 210 to be applied to the next PRS subframe. Thus, the position at which the PRS symbol is allocated to the subcarriers may be different for each successive PRS subframe.

Similarly, a base station using an extended CP may assign a PRS symbol and a CRS symbol to subcarriers using a position reference signal pattern 220. [ In addition, when the operation of assigning the PRS symbol and the CRS symbol to the subcarriers in the current PRS subframe is completed, the base station can change the position reference signal pattern 220 to be applied to the next PRS subframe.

Hereinafter, how the position of a PRS symbol is allocated to subcarriers varies according to successive PRS subframes. FIG. 3 is a diagram illustrating position reference signal patterns 310, 320, 330, 340, 350, 360 applied to successive PRS subframes in an embodiment of a wireless communication system using a conventional CP. The abscissa, ordinate, and symbols of the position reference signal patterns 310, 320, 330, 340, 350, 360 have the same meanings as those of FIG. Hereinafter, it is assumed that the position reference signal is transmitted along the downlink in six consecutive PRS subframes.

3, the position reference signal pattern 310 of the first PRS sub-frame (n _s = 0) to the position reference signal pattern 360 of the last PRS sub-frame (n _s = 5) is shown. The position reference signal patterns 310, 320, 330, 340, 350, and 360 may be generated by shifting a preset position reference signal pattern by an identifier of a base station. Further, the PRS symbol can be shifted by one subcarrier in the frequency domain for each subframe. A comparison of the position reference signal pattern 310 applied to the first PRS subframe and the position reference signal pattern 320 applied to the second PRS subframe shows that the position of the PRS symbol in the same slot is changed along the subcarrier have.

The position of the PRS symbol may be changed sequentially along successive PRS subframes. The location of the PRS symbol may be cycled along the subcarriers supported by the wireless communication system. When the position of a particular PRS symbol reaches the highest or lowest subcarrier of the subcarriers in a particular PRS subframe, the position of a particular PRS symbol in the next subframe can be changed to the lowest subcarrier or highest carrier have. Because the position of the PRS symbol is rotated along the subcarriers, the number of PRS symbols in each of the PRS subframes may be the same. Referring to FIG. 3, the number of PRS symbols of each of the position reference signal patterns 310, 320, 330, 340, 350, and 360 may be the same.

Referring to FIG. 3, the PRS symbol 311 of the first PRS subframe may be allocated to the highest subcarrier among the subcarriers. As the position of the PRS symbol is cycled along the subcarriers, the PRS symbol 322 of the second PRS subframe corresponding to the PRS symbol 311 can be assigned to the lowest subcarrier.

Since the positions of the PRS symbols are rotated along the subcarriers, the number of PRS symbols allocated to each of the subcarriers may be the same. 3, the total number of PRS symbols 311, 321, 331, 332, 351, 352, 361, and 362 allocated to the highest subcarrier among the subcarriers is eight, It can be seen that the number of allocated PRS symbols is also equal to all eight. Thus, when a position reference signal generated by a method or apparatus for generating a position reference signal according to an embodiment is transmitted, all subcarriers can be used equally. Referring to FIG. 3, eight PRS symbols are allocated to a total of 12 subcarriers, so that the total number of PRS symbols may be 12x8 = 96.

Since all subcarriers are used equally in the transmission of the position reference signal, the time correlation property of the position reference signal can be improved. In particular, in the temporal correlation property of the position reference signal, side peaks can be improved. When a single position reference signal pattern is used for successive PRS subframes, i.e., when the positions of the PRS symbol and the CRS symbol of PRS subframes are all the same, unnecessary frequency components are included in the position reference signal due to unused subcarriers . For example, when generating six PRS subframes using only the position reference signal pattern 340, neither symbol may be assigned to two subcarriers including the highest subcarrier. This can cause high side peaks when the position reference signal is frequency-transformed. On the other hand, the position reference signal generated by the position reference signal generation method according to an embodiment utilizes all the subcarriers equally, so that the side peak can be improved.

The BS performing the position reference signal generation method according to an exemplary embodiment may determine a parameter v _shift indicating the degree to which the position reference signal pattern is shifted for each PRS subframe based on Equation (1).

는 기지국의 식별자(cell ID)를 의미한다. mod는 modulo 연산을 의미한다. 일실시예에 따른 위치 참조 신호 생성 방법 또는 장치는 기존의 무선 통신 시스템에 비교적 용이하게 적용될 수 있다.Referring to Equation 1, n _s as a variable is determined in accordance with the slots in the sequence and the PRS sub-frame of the PRS sub-frame, PRS code of the sub-frame _{n sub -frame (n sub -frame =} 0, 1, 2, 3 , ... 5) and with respect to the _slot number n (n = 0 or 1 _slot) of the PRS slots in the subframe can be determined by _{n s = 2 × n sub -frame} + n slot.

(Cell ID) of the base station. mod means modulo operation. The method or apparatus for generating a position reference signal according to an exemplary embodiment may be applied to an existing wireless communication system relatively easily.

4 is a diagram illustrating position reference signal patterns 410, 420, 430, 440, 450, 460 applied to successive PRS subframes in one embodiment of a wireless communication system using an extended CP. The abscissa, ordinate, and symbols of the position reference signal patterns 410, 420, 430, 440, 450, and 460 have the same meanings as those of FIG.

The position reference signal may be generated in a manner similar to a normal CP in an extended CP. Referring to FIG. 4, the position reference signal patterns 410, 420, 430, 440, 450, and 460 are shifted along the subcarrier for each PRS subframe as described with reference to FIG. For example, when the PRS symbol 411 of the first PRS subframe is allocated to the lowest subcarrier among the subcarriers, the PRS symbol 421 of the second PRS subframe corresponding to the PRS symbol 411 is the lowest sub- Can be shifted by one from the carrier. The base station can determine the parameter v _shift indicating the degree to which the position reference signal pattern is shifted for each PRS subframe based on Equation (1).

As described above, an extended CP having a CP period longer than a normal CP may be applied to a wireless communication system to eliminate inter-symbol interference (ISI). Since the CP period is longer, the number of PRS symbols that can be allocated per subframe can be reduced. 4, the total number of PRS symbols 411, 412, 431, 441, 461, and 462 allocated to the lowest subcarrier among the subcarriers is six, and each of the remaining subcarriers It can be seen that the number of allocated PRS symbols is all six. Therefore, since six PRS symbols are allocated to each of the 12 subcarriers in total, the total number of PRS symbols can be 12 x 6 = 72. This is less than the number of PRS symbols of the normal CP of FIG.

If a single position reference signal pattern is used in successive PRS subframes, the number of unused subcarriers may be greater than that of a normal CP because the number of PRS symbols that can be allocated per subframe is reduced have. For example, when six PRS subframes are generated using only the position reference signal pattern 410, none of the symbols may be allocated to four subcarriers. Therefore, the side peak obtained by frequency-converting the position reference signal generated using only one position reference signal pattern may be higher than the side peak obtained by frequency-converting the position reference signal generated using the single position reference signal pattern in the general CP have. Thus, the performance of measuring the time delay using the position reference signal may be degraded.

On the other hand, the position reference signal generated by the position reference signal generation method according to an embodiment utilizes all the subcarriers equally, so that the side peak can be improved. Referring to FIG. 4, since PRS symbols are allocated to subcarriers by different position reference signal patterns 411, 412, 431, 441, 461, and 462 for every PRS subframe, It can be seen that the PRS symbol is allocated. Therefore, since all the subcarriers are used equally, the time correlation characteristic of the position reference signal can be improved.

5 is a flowchart illustrating operations performed by the UE 510 and the BS 520 to which the position reference signal generating method according to an embodiment is applied. A computer-readable recording medium on which a program for executing the position reference signal generating method according to an embodiment is recorded may be provided. The program may include at least one of an application program, a device driver, a firmware, a middleware, a dynamic link library (DLL), and an applet storing a location reference signal generation method. According to one embodiment, the terminal 510 and the base station 520 include a processor, and the processor can perform the position reference signal generation method by reading the recording medium on which the position reference signal generation method is recorded.

Referring to FIG. 5, in step 530, the BS 520 may determine a position reference signal pattern indicating, in subframe units, how to assign the PRS symbol and the CRS symbol to the subcarriers. As described above, the position reference signal may include one or more CRS symbols and PRS symbols. If CRS symbols and PRS symbols are arranged along a position reference signal pattern on a subcarrier and a slot-based coordinate space, PRS symbols can be diagonally placed between CRS symbols. The location reference signal pattern may be generated according to the identifier of the base station 520. Accordingly, neighbor base stations can generate different position reference signal patterns.

Referring to FIG. 5, in step 540, the base station 520 may generate a position reference signal by assigning PRS symbols and CRS symbols to subcarriers based on the determined position reference signal pattern. The position reference signal may be transmitted in a plurality of subframes (i.e., a PRS subframe). For each PRS sub-frame in which the position reference signal is transmitted, the base station 520 may change the position reference signal pattern. The location reference signal pattern may be changed based on the identifier of the base station 520 or the number of the PRS subframe. For example, the position reference signal pattern may be changed based on Equation (1).

Referring to FIG. 5, the BS 520 may transmit the generated position reference signal to the UE 510 in PRS subframes. As described above, the position reference signal may be transmitted through six PRS subframes every 160, 320, 640 and 1280 msec.

Referring to FIG. 5, in step 550, the terminal 510 calculates the time delay of the position reference signal, the time difference of the position reference signal (e.g., RSTD) The distance of at least one of < / RTI > Hereinafter, an operation of determining the distance to the base station 520 by calculating the time of arrival (TOA) of the received position reference signal will be described.

The terminal 510 may calculate the arrival time of the received position reference signal based on the correlation of the sequence of the received position reference signal and the previously stored sequence of position reference signals. The sequence of the QPSK-modulated position reference signal can be expressed by Equation (2).

이고,

은 위치 참조 신호에 대해 할당된 다운 링크 자원 블록의 최대값이다. n_slot은 서브 프레임 내의 슬롯 번호이고, l은 슬롯에서의 OFDM 심볼 번호(OFDM symbol number)이다. c[ ]은 length-31 Gold sequence에 의해 생성된 pseudo-random sequence를 의미한다.Referring to Equation (2)

ego,

Is the maximum value of the downlink resource block allocated for the position reference signal. n _slot is the slot number in the subframe and l is the OFDM symbol number in the slot. c [] denotes a pseudo-random sequence generated by a length-31 Gold sequence.

라 할 때,

는 수학식 3과 같이 나타낼 수 있다.According to a PRS mapping criterion, a complex symbol can be mapped to resource elements (REs). The transmitted mapped transmitted signal sequence in the frequency domain

In other words,

Can be expressed by Equation (3).

이고,

은 패스트 푸리에 변환(FFT, fast Fourier transform) 사이즈를 의미한다. 수학식 3에 주파수 축의 심볼이 생성될 수 있다. 주파수 축의 심볼은 수학식 4에 의해 시간 축 신호로 변경될 수 있다. 여기에서, OFDM 변조된 위치 참조 신호를 패스트 푸리에 역변환(IFFT, inverse FFT)에 의해 변환한 시간 영역에서의 신호는 수학식 4와 같다.Referring to Equation (3), m represents a frequency subcarrier index,

ego,

Quot; means a fast Fourier transform (FFT) size. A symbol of a frequency axis can be generated in Equation (3). The symbol of the frequency axis can be changed to the time axis signal by Equation (4). Here, the signal in the time domain obtained by transforming the OFDM-modulated position reference signal by an inverse fast Fourier transform (IFFT) is expressed by Equation (4).

이다. 위치 참조 신호는 복수의 서브 프레임들에서 전송되므로, 서브 프레임들 각각의 신호 시퀀스들은 서로 병합되어야 한다. N_{sub -frame}을 위치 참조 신호가 전송되는 서브 프레임의 개수로, N_slot을 서브 프레임당 슬롯의 개수로, N_symb를 슬롯 당 심볼의 개수라 하자. 수학식 4를 복수의 서브 프레임으로 확장하여, 즉, n_s 번째 서브 프레임의 위치 참조 신호를 IFFT 변환한 시간 영역의 신호를

라 할 때에, CP를 포함하는 전체 위치 참조 신호 시퀀스는 수학식 5로 나타낼 수 있다.Referring to Equation 4,

to be. Since the position reference signal is transmitted in a plurality of subframes, the signal sequences of each of the subframes must be merged with each other. The N _{sub -frame} to the number of subframes transmitted the position reference signal, and the _slot N by the number of slots per sub-frame, Let the number of symbols per slot for N _symb. By extending the equation (4) into a plurality of sub-frames, that is, the n _s signal of a position reference signal of the second sub-frame IFFT converted time domain

, The entire position reference signal sequence including CP can be expressed by Equation (5).

이다. 심볼 인덱스

에서

,

,

이고,

는 시간 샘플의 개수의 관점에서 l번째 심볼에 대한 CP 길이이다. 20 MHz 폭의 일반 CP를 이용하는 무선 통신 시스템에서,

일 수 있다. 20 MHz 폭의 확장 CP를 이용하는 무선 통신 시스템에서,

일 수 있다. 샘플 인덱스

로 정의될 수 있다. CP 삽입으로 인하여,

에 대하여

이 성립할 수 있다.Referring to Equation (5), symbol index

to be. Symbol index

in

,

,

ego,

Is the CP length for the lth symbol in terms of the number of time samples. In a wireless communication system using a general CP of 20 MHz width,

Lt; / RTI > In a wireless communication system using an extended CP of 20 MHz width,

Lt; / RTI > Sample Index

. ≪ / RTI > Due to the CP insertion,

about

Can be established.

Since the CP includes inter-symbol interference after applying the multipath channel, the influence of the CP on the correlation between the received position reference signal and the pre-stored position reference signal needs to be eliminated. Therefore, the CP in the sequence of the position reference signal (i.e., the reference position reference signal) stored in advance from the sequence of the transmitted position reference signal can be replaced with zero. Thus, the sequence r [i] of the reference position reference signal correlated with the received position reference signal can be defined by equation (6).

In Equation (6) to be.

In order to model the indoor multi-path channel, a tapped delay line channel model as shown in Equation (7) can be defined.

이다. 여기서 샘플링 시간 간격은 T_s로써, T_s는 1/BW_SC/N_fft에 의해 결정될 수 있다. BW_SC는 단일 서브 캐리어의 대역폭으로, 예를 들어, LTE 무선 통신 시스템의 경우 15kHz일 수 있다. 결론적으로, 샘플링된 탭핑된 지연 라인 채널 모델은 수학식 8과 같다.Referring to Equation 7, L is the number of multipath tap, a _l is l the size of the second tab, τ _l is a delay of the l-th tap, δ (t) is t = 0 to 1 and the other t Is a delta function that is zero. Since the sampled tap delay in terms of the time index sampled at the terminal 510 receiving the position reference signal is required, the time delay can be adjusted using a rounding operation. In other words,

to be. Where the sampling time interval is T _s , and T _s can be determined by 1 / BW _SC / N _fft . BW _SC is the bandwidth of a single subcarrier, for example, 15 kHz for an LTE wireless communication system. As a result, the sampled tapped delay line channel model is expressed by Equation (8).

The position reference signal transmitted by the base station 520 may be transmitted to the terminal 510 through a delay tapped channel of Equation (8). Therefore, the sequence y [i] of the position reference signal received by the terminal 510 can be expressed by Equation (9).

이고, 연산 '*'는 콘볼루션 연산자를 의미하고, w[i]는 단말(510)의 추가적인 열 노이즈(additive thermal noise)를 의미한다.Referring to Equation 9,

, The operation '*' denotes the convolution operator, and w [i] denotes the additive thermal noise of the terminal 510.

In order to detect the first tap, the terminal 510 can derive the correlation between the sequence of the received position reference signal and the sequence of the reference position reference signal based on Equation (10).

Referring to Equation (10), N _w is a search window used for measuring a position, and () ^* means a complex number. The terminal 510 measures the delay of the first tap by selecting the fastest peak (first peak) among a plurality of peaks larger than a preset threshold value in the correlation between the sequence of the received position reference signal and the sequence of the reference position reference signal can do. By the maximum likelihood criterion (ML criterion), the first tap for the preset threshold value? Can be measured as shown in Equation (11).

The predetermined threshold? Can be determined in consideration of the multi-path channel in the position measurement. The terminal 510 may calculate the time delay or time difference of the position reference signal based on the determined first tap. Further, the terminal 510 can determine the distance to the base station 520 based on the computed time delay or time difference.

As described above, since the PRS symbol of the position reference signal generated by the position reference signal generating method according to an embodiment is uniformly allocated to all the subcarriers, the terminal 510 calculates the reception In the correlation of the sequence of the position reference reference signal and the sequence of the reference position reference signal, the side peak can be eliminated. In other words, the position reference signal generated by the method of generating a position reference signal according to an embodiment may have improved auto-correlation characteristics. Accordingly, when the terminal 510 time-correlates the received position reference signal and the reference position reference signal, the terminal 510 can more accurately estimate the time delay due to the transmission of the position reference signal. Further, the terminal 510 can accurately determine the geographical position of the terminal 510 by estimating the time delay with a plurality of base stations in the same way.

According to another embodiment, a method of generating a position reference signal can similarly be performed for an uplink. In this case, an operation performed by the base station 520 may be performed by the terminal 510, and an operation performed by the terminal 510 may be performed by the base station 520. That is, the UE 510 determines a pattern of a position reference signal in a single subframe, changes the pattern of the position reference signal in each subframe, and uses the changed position reference signal pattern to convert the PRS symbol into subcarriers The position reference signal can be generated. The base station 520 may correlate a sequence of received position reference signals with a sequence of previously stored reference position reference signals to determine at least one of a time delay, a time difference, and a distance to the terminal 510.

In summary, in a process of generating a position reference signal transmitted in a plurality of subframes, a base station or a terminal to which the position reference signal generation method according to an embodiment is applied, instead of using the same position reference signal pattern for each of a plurality of subframes, A position reference signal pattern in which the position of the PRS symbol is shifted along the subcarrier for each of a plurality of subframes can be used. Thus, the PRS symbol can be evenly allocated to all subcarriers. Therefore, the phenomenon that some subcarriers are not used can be prevented, and unnecessary frequency components can be prevented from being included in the position reference signal. Therefore, the terminal or the base station receiving the position reference signal can measure the time difference by correlating the sequence of the received position reference signal with the previously stored reference position reference signal sequence. At this time, occurrence of a side peak due to an unnecessary frequency component can be prevented. Therefore, the terminal or the base station receiving the position reference signal can more accurately measure the distance to the base station or the terminal that has transmitted the position reference signal.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) , A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

110: terminal
120: base station
130: Base station
140: base station

Claims (5)

A method of generating a position reference signal (PRS) performed by a base station,
A method for determining how to allocate a symbol of a position reference signal used for determining a distance between a terminal and a base station to subcarriers which are frequencies used for communication between the terminal and a base station, Determining a reference signal pattern; And
Allocating a symbol of the position reference signal to the subcarriers based on the position reference signal pattern and generating a position reference signal transmitted to the terminal using a plurality of subframes
Lt; / RTI >
Wherein the generating comprises:
And changing the position reference signal pattern for each of the plurality of subframes. The method according to claim 1,
Wherein the generating comprises:
And shifting a position of a symbol of the position reference signal along the subcarriers to change the position reference signal pattern based on a number assigned to each of the plurality of subframes. The method according to claim 1,
Wherein the generating comprises:
And changing the position reference signal pattern such that the number of symbols of the position reference signal allocated to each of the subcarriers is all the same. The method according to claim 1,
Wherein the generating comprises:
Wherein the position reference signal pattern is changed so that symbols of the same number of the position reference signals are allocated to each of the plurality of subframes. The method according to claim 1,
Wherein the number of symbols of the position reference signal included in the position reference signal pattern is
(CP, Cylic Prefix) added between the symbols to remove inter-symbol interference.

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