KR20210006839A - Apparatus and method for detecting interference between base stations in wireless communication system - Google Patents

Abstract

The present invention relates to a fifth-generation (5G) or pre-5G communication system for supporting a higher data transmission rate after a fourth-generation (4G) communication system such as long term evolution (LTE). The present invention is provided to detect interference between base stations in a wireless communication system. According to the present invention, a method for operating a base station comprises the following processes: receiving signals through resources allocated for reference signals (RSs) for interference measurement; detecting at least one RS based on the signals; and determining reception of at least one of the at least one RS based on cross-correlation values between the candidate RSs.

Description

Apparatus and method for detecting interference between base stations in a wireless communication system {APPARATUS AND METHOD FOR DETECTING INTERFERENCE BETWEEN BASE STATIONS IN WIRELESS COMMUNICATION SYSTEM}

The present disclosure generally relates to a wireless communication system, and more particularly, to an apparatus and method for detecting interference between base stations in a wireless communication system.

4G (4 ^th generation) to meet the traffic demand in the radio data communication system increases since the commercialization trend, efforts to develop improved 5G (5 ^th generation) communication system, or pre-5G communication system have been made. For this reason, the 5G communication system or the pre-5G communication system is called a Beyond 4G Network communication system or a Long Term Evolution (LTE) system (Post LTE) system.

In order to achieve a high data rate, the 5G communication system is being considered for implementation in the ultra-high frequency (mmWave) band (for example, the 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, in 5G communication systems, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, in order to improve the network of the system, in 5G communication system, advanced small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation And other technologies are being developed.

In addition, in the 5G system, the advanced coding modulation (Advanced Coding Modulation, ACM) method of FQAM (Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation) and SWSC (Sliding Window Superposition Coding), and advanced access technology, FBMC (Filter Bank Multi Carrier) ), NOMA (Non Orthogonal Multiple Access), and SCMA (Sparse Code Multiple Access) are being developed.

In various wireless communication systems including 5G systems, interference between devices (eg, base stations and terminals) performing wireless communication may occur at any time. The type of interference may be variously defined according to the relationship between devices in an indirect relationship. Since interference causes deterioration of communication quality, it is desirable that the interference is properly controlled.

Based on the above discussion, the present disclosure provides an apparatus and method for effectively detecting interference between base stations in a wireless communication system.

Further, the present disclosure provides an apparatus and method for improving interference detection performance in a wireless communication system.

In addition, the present disclosure provides an apparatus and method for reducing a probability of erroneous determination of a signal for interference detection in a wireless communication system.

According to various embodiments of the present disclosure, a method of operating a base station in a wireless communication system includes a process of receiving signals through resources allocated for RS (reference signals) for interference measurement, and at least one based on the signals. A process of detecting an RS of and a process of determining that at least one of the at least one RS has been received based on cross-correlation values between candidate RSs.

According to various embodiments of the present disclosure, in a wireless communication system, a base station includes a transceiver and at least one processor connected to the transceiver. The at least one processor receives signals through resources allocated for RS (reference signals) for interference measurement, detects at least one RS based on the signals, and calculates cross-correlation values between candidate RSs. Based on, it may be determined that at least one of the at least one RS has been received.

The apparatus and method according to various embodiments of the present disclosure may reduce a probability of erroneous determination of an interference signal.

The effects obtainable in the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the technical field to which the present disclosure belongs from the following description. will be.

1 illustrates a wireless communication system according to various embodiments of the present disclosure.
2 illustrates a configuration of a base station in a wireless communication system according to various embodiments of the present disclosure.
3 illustrates an example of mapping a remote interference management (RIM) reference signal (RS) signal in a wireless communication system according to various embodiments of the present disclosure.
4A to 4C illustrate examples of relative positions of RIM RSs according to carrier frequencies in a wireless communication system according to various embodiments of the present disclosure.
5 illustrates an example of a reception window for detecting a RIM RS in a wireless communication system according to various embodiments of the present disclosure.
6 illustrates a functional configuration of a base station for detecting RIM RS in a wireless communication system according to various embodiments of the present disclosure.
7A illustrates a false alarm (FA) probability when performing a peak to average power ratio (PAPR) test in an environment using one candidate RIM RS.
7B shows a probability of a detection failure when receiving a RIM RS in an environment in which one candidate RIM RS is used.
FIG. 8A shows an FA probability and an error detection probability according to a PAPR test when one RIM RS is received in an environment using 8 candidate RIM RSs.
8B shows a probability of a detection failure according to a PAPR check when one RIM RS is received in an environment using 8 candidate RIM RSs.
9A shows an FA probability and an error detection probability according to a PAPR check when two RIM RSs are received in an environment using 8 candidate RIM RSs.
9B shows a probability of a detection failure according to a PAPR test when two RIM RSs are received in an environment using 8 candidate RIM RSs.
10 is a flowchart illustrating a RIM RS detection of a base station in a wireless communication system according to various embodiments of the present disclosure.
11 is a flowchart illustrating a pruning test of a base station in a wireless communication system according to various embodiments of the present disclosure.
12A illustrates an FA probability and an error detection probability according to a pruning test performed when one RIM RS is received in an environment using 8 candidate RIM RSs.
12B shows a probability of a detection error according to a pruning test performed when one RIM RS is received in an environment using 8 candidate RIM RSs.
13A shows an FA probability and an error detection probability according to a pruning check when two RIM RSs are received in an environment using eight candidate RIM RSs.
13B shows a probability of a detection error according to a pruning check when two RIM RSs are received in an environment using 8 candidate RIM RSs.
14 illustrates a functional configuration of a base station for detecting RIM RS in a wireless communication system according to various embodiments of the present disclosure.
15 is a flowchart illustrating a space whitening performed by a base station in a wireless communication system according to various embodiments of the present disclosure.
16A shows an error detection probability according to spatial whitening performance when one RIM RS is received in an environment using 8 candidate RIM RSs.
16B shows the probability of a detection failure according to spatial whitening when one RIM RS is received in an environment using 8 candidate RIM RSs.

Terms used in the present disclosure are used only to describe a specific embodiment, and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the technical field described in the present disclosure. Among the terms used in the present disclosure, terms defined in a general dictionary may be interpreted as having the same or similar meaning as the meaning in the context of the related technology, and unless explicitly defined in the present disclosure, an ideal or excessively formal meaning Is not interpreted as. In some cases, even terms defined in the present disclosure cannot be interpreted to exclude embodiments of the present disclosure.

In various embodiments of the present disclosure described below, a hardware approach is described as an example. However, since various embodiments of the present disclosure include technology using both hardware and software, various embodiments of the present disclosure do not exclude a software-based approach.

Hereinafter, the present disclosure relates to an apparatus and method for detecting interference between base stations in a wireless communication system. Specifically, the present disclosure describes a technique for reducing a probability of erroneous determination of the presence or absence of a signal for measuring interference in a wireless communication system.

In the following description, a term referring to a signal, a term referring to a channel, a term referring to control information, a term referring to network entities, a term referring to a component of a device, etc. are for convenience of description. It is illustrated. Accordingly, the present disclosure is not limited to terms to be described later, and other terms having an equivalent technical meaning may be used.

In addition, in the present disclosure, in order to determine whether a specific condition is satisfied or satisfied, an expression exceeding or less than is used, but this is only a description for expressing an example, and more or less descriptions are excluded. Not to do. Conditions described as'greater than' may be replaced with'greater than', conditions described as'less than' may be replaced with'less than', and conditions described as'more and less' may be replaced with'greater than and less than'.

In addition, the present disclosure describes various embodiments using terms used in some communication standards (eg, 3rd Generation Partnership Project (3GPP)), but this is only an example for description. Various embodiments of the present disclosure may be easily modified and applied to other communication systems.

1 illustrates a wireless communication system according to various embodiments of the present disclosure. Referring to FIG. 1, a wireless communication system includes a base station 110 and a base station 120. 1 illustrates the base station 110 and the base station 120, but other base stations may be further included.

The base station 110 and the base station 120 are network infrastructures that provide wireless access to terminals. The base station 110 and the base station 120 have coverage defined as a certain geographic area based on a distance at which signals can be transmitted. In addition to the base station, the base station 110 and the base station 120 are'access points (APs)','eNodeBs (eNBs)', '5G nodes (5th generation nodes)', and'genodes. It may be referred to as'next generation nodeB (gNB)','wireless point','transmission/reception point (TRP)', or other terms having an equivalent technical meaning. In some cases, the base station may be referred to as a'cell'.

The base station 110 may transmit or receive signals according to the frames 112. The base station 120 may transmit or receive signals according to the frames 122. In the frames 112 or 122,'D' is a downlink section,'G' is a gap section, and'U' is an uplink section. The downlink period may include at least one downlink subframe, slot or symbol, and the uplink period may include at least one uplink subframe, slot or symbol. The gap period may be understood as at least one symbol other than a downlink pilot time slot (DwPTS) and an uplink pilot time slot (UpPTS) in a flexible slot or symbol, or a special subframe.

Under certain climatic conditions, the high-altitude Earth's atmosphere exhibits a low density due to its low refractive index, which causes the signal to bend toward the Earth. In this situation, refraction and reflection occur at the boundary of the atmosphere having a low refractive index, so that a signal is transmitted along a layer having a relatively high refractive index. Due to this transmission method called atmospheric waveguide, the radio signal experiences small attenuation and reaches a long distance far beyond the normal radiation range. This usually occurs during the spring and summer transitions on continents and during the summer and autumn transitions, and may occur in winter on the beach. It is known that this phenomenon occurs over a frequency range of 0.3GHz to 30GHz.

When a time division duplex (TDD) scheme having uplink and downlink is used in one spectrum, a gap section exists to avoid interference between uplink and downlink. However, when the above-described waveguide phenomenon occurs, the radio signal may move a very long distance, and the propagation delay time of the radio signal may be greater than the length of the gap section. In this case, the base station 110 causing interference (hereinafter referred to as'attacker') aggressor)') may act as interference in the uplink section of the far-distant base station 120 (hereinafter, referred to as'victim'). This interference may be referred to as remote interference. The further away the attacker is from the victim, the more delayed the uplink symbol after the gap period is received by the victim, so that the more uplink symbols of the victim are subject to interference.

In order to determine from which base station an interference signal has been transmitted, the base stations transmit a signal for measurement in a downlink interval and at the same time receive a signal in an uplink interval to determine which base station is an interference source. A signal for measuring interference between base stations may be referred to as a “remote interference management (RIM) reference signal (RS)”. Therefore, there is a need for a technique for detecting which RIM RS has been received from the viewpoint of the receiving base station.

The RIM RS may include one sequence among a set of candidate sequences including a plurality of sequences. Here, that the RIM RS includes the sequence means that the RIM RS is generated based on the sequence, and for example, the RIM RS can be obtained by modulating the sequence (eg, QPSK (qudrature phase shift keying) modulation). For example, sequences may be defined based on a gold sequence having a robust alignment characteristic. Accordingly, the operation of detecting the RIM RS refers to an operation of determining whether the sender has transmitted the RIM RS including which of the candidate sequences. That is, detection of the RIM RS is an operation of determining the index k of the sequence included in the received RIM RS, and in the present disclosure,'detecting RIM RS' and'detecting a sequence' may be used interchangeably with each other. have. Here, if the index of the plurality of candidate sequences is k, the RIM RS including the sequence of the index k may be referred to as'RIM RS k'.

2 illustrates a configuration of a base station in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 2 can be understood as the configuration of the base station 110 or 120. Used below'… Wealth','… The term'group' refers to a unit that processes at least one function or operation, which may be implemented by hardware or software, or a combination of hardware and software.

Referring to FIG. 2, the base station includes a wireless communication unit 210, a backhaul communication unit 220, a storage unit 230, and a control unit 240.

The wireless communication unit 210 performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication unit 210 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the wireless communication unit 210 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the wireless communication unit 210 restores the received bit stream through demodulation and decoding of the baseband signal.

In addition, the wireless communication unit 210 up-converts the baseband signal into a radio frequency (RF) band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. To this end, the wireless communication unit 210 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. In addition, the wireless communication unit 210 may include a plurality of transmission/reception paths. Further, the wireless communication unit 210 may include at least one antenna array composed of a plurality of antenna elements.

In terms of hardware, the wireless communication unit 210 may be composed of a digital unit and an analog unit, and the analog unit includes a plurality of sub-units according to operating power, operating frequency, etc. It can be composed of. The digital unit may be implemented with at least one processor (eg, a digital signal processor (DSP)).

The wireless communication unit 210 transmits and receives signals as described above. Accordingly, all or part of the wireless communication unit 210 may be referred to as a'transmitter', a'receiver', or a'transceiver'. In addition, in the following description, transmission and reception performed through a wireless channel are used to mean that the above-described processing is performed by the wireless communication unit 210.

The backhaul communication unit 220 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 220 converts the bit stream transmitted from the base station to another node, for example, another access node, another base station, an upper node, a core network, etc., into a physical signal, and converts a physical signal received from another node. Convert to bit string.

The storage unit 230 stores data such as a basic program, an application program, and setting information for the operation of the base station. The storage unit 230 may be formed of a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. In addition, the storage unit 230 provides stored data according to the request of the control unit 240.

The controller 240 controls overall operations of the base station. For example, the control unit 240 transmits and receives signals through the wireless communication unit 210 or through the backhaul communication unit 220. In addition, the control unit 240 writes and reads data in the storage unit 230. In addition, the control unit 240 may perform functions of a protocol stack required by a communication standard. According to another implementation example, the protocol stack may be included in the wireless communication unit 210. To this end, the control unit 240 may include at least one processor. According to various embodiments, the controller 240 may control the base station to perform operations according to various embodiments to be described later.

According to an embodiment, the control unit 240 detects whether a RIM RS is received, and an index of a sequence included in the received RIM RS. The control unit 240 may determine which sequence of RIM RSs are received using signals extracted from the resources to which the RIM RSs are mapped. For example, the control unit 240 calculates channel power and noise power corresponding to each sequence candidate, checks the sequence of at least one RIM RS received based on the channel power and noise power, and checks at least one Verification may be performed to determine whether the sequence is finally received.

For convenience of description below, a base station that transmits the RIM RS is referred to as a'sender', and a base station that determines an interference source through the RIM RS is referred to as a'detector'.

The RIM RS transmitted and received according to various embodiments of the present disclosure may be designed as follows. 3 illustrates an example of mapping a RIM RS signal in a wireless communication system according to various embodiments of the present disclosure. Referring to FIG. 3, resources occupied by the RIM RS within a sender's bandwidth (BW) are defined. 3 illustrates a first case 310 in which the sender's bandwidth is 20 MHz, and a second case in which the sender's bandwidth is 10 MHz (320). In the first case 310 in which the bandwidth is 20 MHz, the number of available resource blocks (RBs) is 100. In this case, one RIM RS is mapped to 44 RBs in the low frequency domain within the bandwidth, and one RIM RS is mapped to 44 RBs in the high frequency domain. In the second case 320 where the bandwidth is 10 MHz, the number of available RBs is 50. In this case, one RIM RS is mapped to 44 RBs in the center frequency domain.

The RIM RS as shown in FIG. 3 is designed in consideration of various combinations of center frequencies and bandwidths of the sender and the detector. The RS designed as shown in FIG. 3 may be detected as shown in FIGS. 4A to 4C according to the center frequency and bandwidth.

4A to 4C illustrate examples of relative positions of RIM RSs according to carrier frequencies in a wireless communication system according to various embodiments of the present disclosure.

4A illustrates a signal in a band having a center frequency of 2310 MHz and a bandwidth of 20 MHz and a signal in a band having a center frequency of 2320 MHz and a bandwidth of 20 MHz. In order for the detector of the center frequency 2310 MHz band to detect the signal transmitted at the center frequency 2320 MHz, the RIM RS is mapped to the lower band of the center frequency 2320 MHz. In order to maximize the number of RBs to which the RIM RS is mapped, it is preferable that the received signal is located at the frequency of the RB to which the tone corresponding to the lowest frequency 2311 MHz belongs to the highest frequency tone of the center frequency 2310 MHz. Therefore, the number of RBs may be selected as 44. Conversely, in order for the detector of the center frequency 2320 MHz band to detect the signal transmitted at the center frequency 2310 MHz, the RIM RS is mapped to the high band at the center frequency 2310 MHz. In order to maximize the number of RBs of the RIM RS, it is preferable to map the RIM RS from the tone corresponding to the lowest frequency of 2311.095 MHz to the highest frequency tone of the center frequency 2310 MHz. Therefore, the number of RBs may be selected as 44.

4B illustrates a signal in a band having a center frequency of 2320 MHz and a bandwidth of 20 MHz and a signal in a band having a center frequency of 2325 MHz and a bandwidth of 10 MHz. In order for the detector of the center frequency 2320 MHz band to detect the signal transmitted at the center frequency 2325 MHz, it is confirmed that it is preferable that the RIM RS is not mapped to the three RBs of the high band of the center frequency 2325 MHz. 4C illustrates a signal in a band having a center frequency of 2305 MHz and a bandwidth of 10 MHz and a signal in a band having a center frequency of 2310 MHz and a bandwidth of 20 MHz. In order for the detector of the center frequency 2310 MHz band to detect the signal transmitted at the center frequency 2305 MHz, it is confirmed that it is preferable that the RIM RS is not mapped to the three RBs in the lower band of the center frequency 2305 MHz. Referring to FIGS. 4B and 4C, it is confirmed that a base station using a 10 MHz bandwidth is preferable to map RIM RSs to 44 RBs among them.

5 illustrates an example of a reception window for detecting a RIM RS in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 5, the RIM RS has a circular characteristic in which a long cyclic prefix (CP) (eg, two normal CPs) is added to two net OFDM symbols. . Specifically, Ncp samples 519 at the rear end of the first pure OFDM symbol are added as the CP 511 of the first pure OFDM symbol, and Ncp samples 529 at the rear end of the second pure OFDM symbol are the second pure OFDM symbol It is added as the CP 521 of. Here, the Ncp samples 512 preceding the first forward OFDM symbol are the same as the CP 521 of the second forward OFDM symbol. Further, the Ncp samples 512 of the front end of the first forward OFDM symbol and the subsequent Ncp samples 513 are the CP 521 of the second forward OFDM symbol and the Ncp samples 522 of the front end of the second forward OFDM symbol. ) Is the same. As a result, the structure of the RIM RS can be understood in the same way as adding a CP having a length of 2×Ncp to a pure OFDM symbol having a length of twice.

According to the above-described structure, when the bandwidth is 20 MHz and is received with 0 to 2192 sample delay, the RIM RS can be detected without inter symbol interference (ISI) within the reception window. The detector may detect the RIM RS by receiving the first OFDM symbol or the second OFDM symbol through a reception window and removing Ncp samples of the front end from the received OFDM symbol. For example, if the first OFDM symbol is received within the reception window with zero delay, that is, without delay, that is, when the detector completely receives the first symbol in the reception window, the RIM RS may be detected with a reception delay of zero. As another example, when the detector completely receives the second symbol in the reception window, the RIM RS may be detected with a reception delay of -Ncp or a delay of Nfft (=FFT size)-Ncp.

As described above, the detector can detect the RIM RS transmitted by the sender. To detect the RIM RS, the detector estimates the channel power and noise power of the resource (e.g., RBs) to which the RIM RS is mapped for each sequence, and then sets the ratio of the channel power and noise power for each sequence to a threshold (e.g., T _PAPR ) can be compared to determine whether the sequence has been transmitted.

Although the detection performance for a specific RIM RS is important, even though no RIM RS is received, an erroneous determination may be made by noise reception. A situation in which an erroneous judgment occurs may be referred to as a'false alarm (FA)'. For example, when the detector determines to receive a specific sequence even though the sender does not transmit any sequence, this is a situation in which an FA has occurred. Or, even though the sender has transmitted one sequence, if the detector determines to receive two or more sequences, this is also a situation in which an FA has occurred. The probability of occurrence of an FA, that is, a probability that it is incorrectly determined that a sequence that has not been transmitted is detected may be referred to as a'FA probability'.

In addition, in detecting the RIM RS, the probability that the sequence transmitted by the sender is correctly detected by the detector may be referred to as a'detection probability'. The probability of detection for RIM RS k may be expressed _{as'P det} (k)'. The detection probability may be defined as a worst case detection probability and an average detection probability. The worst detection probability is the smallest value among P _det (k), and the average detection probability is the average value of P _det (k). The probability of detection can be expressed as a function for a specific sequence.

It is necessary to improve the detection performance while maintaining the FA probability below a certain level. At the same time, when RIM RS k is received, detection performance while maintaining the probability of error detection that determines that RIM RS q (≠ k) has been received is below a specific level, in other words, while maintaining the detection probability above a specific level. It is necessary to improve.

6 illustrates a functional configuration of a base station for detecting RIM RS in a wireless communication system according to various embodiments of the present disclosure. The components illustrated in FIG. 6 may be understood as a part of the wireless communication unit 210 and the control unit 240 illustrated in FIG. 2.

The frequency shifting unit 602a adjusts the frequency of the signal received through the antenna. The center frequency of the sender and the center frequency of the detector may not be an integer multiple of the tone interval (eg, 15 kHz in the case of FIGS. 4A, 4B, and 4C). Therefore, it is necessary to align the received signals on a frequency grid corresponding to the tone interval of the detector. Accordingly, the frequency shifting unit 602a aligns the signal that has passed through the reception antenna on the frequency grid. Grid mismatch may occur because the sender transmits the RIM RS as a downlink signal and the detector processes the RIM RS as an uplink signal. The base station transmits the downlink signal without frequency shift, but the terminal shifts the uplink signal by 7.25 kHz up (up), so the base station receiving the uplink signal performs a -7.25 kHz down shift as compensation for the shift. Because of this, inconsistency of the grid may occur. In addition, since the width and center frequency of the channel spectrum of the sender and the channel spectrum of the receiver may be different, a grid mismatch may occur. However, if there is no application of the frequency shift between the uplink signal and the downlink signal, the frequency shifting unit 602a may be omitted.

The FFT calculator 604a performs an FFT operation on a signal. That is, the FFT operation unit 604a converts a signal in the time domain into a signal in the frequency domain through the FFT operation. In this case, the number of samples for which the FFT operation is performed is Nfft. Although not shown, before the FFT operation, an operation of removing samples corresponding to CP may be further performed.

The RE (resource element) demapping unit 606a extracts RIM RSs. In other words, the RE demapping unit 606a demaps the signal from the REs (eg, 44 RBs * 12 RE/RB = 528 REs) to which the RIM RS is mapped in the frequency domain signal.

The power calculation unit 608a calculates power for the RIM RS. The power calculator 608a may calculate power by using the magnitudes of signals extracted from REs to which the RIM RS is mapped. Information on the calculated power is provided to the scaling unit 610a.

The scaling unit 610a adjusts the power value for the RIM RS in consideration of the combination. For example, the scaling unit 610a may divide the power value by a small number when the power value is small, and may divide the power value by a large number when the power value is large. The values of the RIM RS processed for each antenna are then summed. When the noise power of the received signal for each antenna is not uniform, the operation of the scaling unit 610a is required to combine the signals at the same noise power level.

The above-described frequency shifting unit 602a, FFT calculating unit 604a, RE demapping unit 606a, power calculating unit 608a, and scaling unit 610a process signals received through one antenna. Therefore, the frequency shifting unit 602b, the FFT calculating unit 604b, the RE demapping unit 606b, the power calculating unit 608b, and the scaling unit 610b processing signals received through other antennas are frequency shifting units ( 602a), the FFT calculating unit 604a, the RE demapping unit 606a, the power calculating unit 608a, and the scaling unit 610a may perform the same operations. In FIG. 6, the frequency shifting unit 602b, the FFT calculation unit 604b, the RE demapping unit 606b, the power calculation unit 608b, and the scaling unit 610b are frequency shifting unit 602a, FFT calculation unit 604a, Although shown as separate component groups from the RE demapping unit 606a, the power calculation unit 608a, and the scaling unit 610a, these are merely functional expressions, and may actually be implemented as separate component groups. Alternatively, one component group may repeatedly process signals received through a plurality of antennas.

If the number of candidate sequences that can be included in the considered RIM RS is K, the detector attempts to detect K RIM RSs. Accordingly, the operation after scaling is repeatedly performed for K candidate sequences. For convenience of description, operations related to one, for example, a sequence of index 1 are representatively described.

The RIM RS-1 removing unit 612a-1 removes the index 1 sequence from the scaled received signal. Accordingly, the RIM RS is removed from the scaled received signal, and the sum of the channel component and noise and interference components is obtained. For example, when RIM RS k is received, a signal from which RIM RS k is removed will have a high channel power, but a signal from which RIM RS q (≠ k) is removed is expected to have a relatively small channel power. Here, removing the RIM RS k refers to an operation of dividing the RIM RS k from the received signal on the frequency axis, and corresponds to the operation of multiplying the conjugated RIM RS k during the time axis correlation operation. In the case of the correlation operation, when RIM RS k is received, the result of the correlation operation with RIM RS k will have a high value, but the result of the correlation operation with RIM RS q(≠k) will have a relatively small value. will be.

The IFFT calculator 614a-1 performs an IFFT operation on the signal from which the RIM RS has been removed. The signal from which the RIM RS has been removed is converted into a signal in the time domain through IFFT operation. Here, in order to reduce channel power loss in the time domain and to facilitate implementation, an IFFT size having a size larger than the number of REs of the RIM RS (eg, a power of 2 corresponding to 2 to 4 times) may be adopted.

The square calculator 616a-1 may calculate a square value of an absolute value of a signal in the time domain. A signal indicating power is obtained as the square of the absolute value of the signal in the time domain by the square calculating unit 616a-1.

As above, the RIM RS-1 removal unit 612a-1, the IFFT operation unit 614a-1, and the square operation unit 616a-1 are preprocessing for detecting RIM RS 1 from a signal received through one antenna. ) Perform actions. Similar operations may be performed by the RIM RS-K removal unit 612a-K, the IFFT operation unit 614a-K, and the square operation unit 616a-K to detect RIM RS K. Also, for signals received through different antennas, similar operations are performed by the RIM RS-1 removal unit 612b-1, the IFFT operation unit 614b-1, the square operation unit 616b-1, and the RIM RS. It may be performed by the -K removal unit 612b-K, the IFFT operation unit 614b-K, and the square operation unit 616b-K. Subsequent operations are performed for each sequence index. For convenience of description, for convenience of description, operations related to a sequence of one, for example, index 1 are representatively described.

The summing unit 618-1 sums the results of pre-processing operations for detecting RIM RS 1 to the signal received through each antenna. That is, by the summing unit 618-1, signals corresponding to each antenna are added after preprocessing related to the same candidate sequence.

The peak detector 620-1 detects at least one peak value from the summed signal. The peak value can be interpreted as the channel power. For example, if the size of the IFFT is 1024, a sample having the largest value among 1024 samples of the summed signal, that is, a sample having a peak value (hereinafter,'peak sample') may be considered as the channel power. . Since the channel power is spread around the sample having the peak value, the peak detector 620-1 may set a window of a predetermined size around the sample having the peak value and estimate the channel power. In the case of a multipath channel, in order to collect channel power for a plurality of paths, the peak detector 620-1 includes a second peak value, a third peak value, etc. around the peak sample identified above within the window. Can be found and added to the channel power component. The position of the peak value is provided to the noise estimation unit 622-1, and the peak value is provided to the comparison unit 624-1.

The noise estimation unit 622-1 estimates the noise power based on the position of the peak value. Since the channel power is spread around the sample having the peak value, the noise estimating unit 622-1 may set a window of a predetermined size around the sample having the peak value and select noise samples without the channel power component. Specifically, the noise estimating unit 622-1 may estimate the power of the noise by averaging the values of samples located outside the window.

The comparison unit 624-1 compares the ratio of the channel power and the noise power with a threshold (eg, T _PAPR ). That is, the comparison unit 624-1 compares the ratio of the channel power related to RIM RS 1 obtained from the peak detection unit 620-1 and the noise power from the noise estimating unit 622-1 with a threshold value. As a result of the comparison, if the ratio is greater than the threshold, it may be determined that RIM RS 1 is received.

The peak detection unit 620-1, the noise estimation unit 622-1, and the comparison unit 624-1 determine whether the RIM RS 1 is received or not is a primary, temporary or preliminary determination/detection, and'PAPR test It may be referred to as'(test)','SNR test','first test', and'first test'. Thereafter, the determination unit 626 may determine whether to be finally detected. The peak detection unit 620-1, the noise estimation unit 622-1, and the comparison unit 624-1 perform determination operations for RIM RS 1, and similar operations for other RIM RSs are performed by the peak detection unit 620-k. ), the noise estimation unit 622-k, and the comparison unit 624-k.

The determination unit 626 determines whether or not the at least one RIM RS determined through the PAPR test is finally detected. When one RIM RS is detected by the PAPR test, the determination unit 626 may finally determine the reception of the detected one RIM RS. However, when a plurality of RIM RSs are detected by the PAPR test, an operation for excluding at least one RIM RS corresponding to the FA is performed in consideration of the possibility of occurrence of the FA. According to various embodiments, the determination unit 626 may determine a detection that is erroneously determined by distortion, that is, a detection corresponding to an FA, in consideration of a cross correlation value between sequences. According to an embodiment, the determination unit 626 determines threshold values corresponding to each of a plurality of detected sequences based on a cross correlation value, and determines whether or not to receive a final reception for each of the plurality of sequences using the threshold values. can do.

7A shows the probability of a false alarm (FA) when performing a PAPR check in an environment using one candidate RIM RS. That is, FIG. 7A shows the FA probability when there is one candidate RIM RS and there is no actually received RIM RS. Referring to FIG. 7A, when there is one candidate RIM RS, that is, the number of available sequences is one, the FA probability is about 0.01. In the definition of the sequence or the design of the detection algorithm, it is desirable to maximize the detection probability while keeping the FA probability below a specific value (eg, 0.01 in FIG. 7).

7B shows a probability of a detection failure when receiving a RIM RS in an environment in which one candidate RIM RS is used. That is, FIG. 7B shows that when the number of candidate RIM RSs is 1 and the number of received RIM RSs is 1, the detection failure probability (=1-detection probability ), that is, the probability of missing. Referring to FIG. 7B, it is confirmed that as the number of reception antennas increases, the loss probability decreases due to a non-coherent coupling gain at a given signal to noise ratio (SNR).

Unlike the FA probability and detection probability, the error detection probability refers to a probability that n (n>0) RIM RSs are received, but it is determined that RIM RSs other than the actually received RIM RSs are received. For example, the error detection probability refers to a probability that RIM RS k is actually received, but it is determined that RIM RS q (≠k) is received. Therefore, the error detection probability may be expressed as a function of the number n of the actually received RIM RSs, and the error detection probability value may vary according to the value of n.

8A shows an FA probability and an error detection probability according to a PAPR check when one RIM RS is received in an environment using 8 candidate RIM RSs. Referring to FIG. 8A, it is confirmed that the FA probability is maintained below 0.01, while the error detection probability increases to a value close to 1 as the number of reception antennas increases and SNR increases.

8B shows a probability of a detection failure according to a PAPR check when one RIM RS is received in an environment using 8 candidate RIM RSs. Referring to FIG. 8B, the worst detection probability and the average detection probability do not show a significant difference, but as the number of reception antennas increases, the probability of missing due to non-coherent coupling gain at a given SNR This decrease is confirmed.

9A shows an FA probability and an error detection probability according to a PAPR check when two RIM RSs are received in an environment using 8 candidate RIM RSs. Referring to FIG. 9A, it is confirmed that the FA probability is maintained at 0.01 or less, while the error detection probability increases to a value close to 1 as the number of reception antennas increases and SNR increases.

9B shows the probability of a detection failure according to a PAPR check when one RIM RS is received in an environment using 8 candidate RIM RSs. 9B, the worst detection probability and the average detection probability do not show a big difference, but as the number of reception antennas increases, the probability of missing due to non-coherent coupling gain at a given SNR This decrease is confirmed.

As described with reference to FIGS. 8B and 9B, in an environment in which K candidate RIM RSs are used, a sufficient error detection probability is secured with only the PAPR test technique even if the detector uses the threshold of the PAPR test that can maintain an appropriate FA probability. It can not be. Accordingly, the present disclosure describes various embodiments of verifying or pruning the RIM RS determined to be received through the PAPR test. Through the pruning operation, it is expected to decrease the probability of error detection without reducing the detection performance. The pruning operation may be referred to as a'pruning test', a'second test', and a'secondary test'. For the pruning test, cross correlation values between sequences that may be included in the RIM RS may be used. For example, for the pruning test, cross-correlation values between RIM RSs including QPSK symbols based on a gold sequence may be used. For example, high pruning performance may be obtained through comparison with a ratio of channel power to RIM RS k and a threshold.

10 is a flowchart illustrating a RIM RS detection of a base station in a wireless communication system according to various embodiments of the present disclosure. 10 illustrates an operation method of the base station 120.

Referring to FIG. 10, in step 1001, the base station receives signals through resources allocated for RSs for interference measurement. RSs for interference measurement may include RIM RS. Resources allocated for RSs for interference measurement may be identified according to a predefined rule. For example, resources (eg, REs or subcarriers) may be determined according to the bandwidth of the operating frequency of the base station. For example, when the bandwidth is 10 MHz, the resource allocated for RSs may include at least one RE in 44 RBs among them. As another example, when the bandwidth is 20 MHz, the resource allocated for RSs is at least one RE in 44 RBs from the bottom of the lower 10 MHz band or at least one RE in 44 RBs from the top of the upper 20 MHz band. Can include.

In step 1003, the base station detects at least one RS based on the signals. That is, the base station performs a PAPR check. For detection of the sequence, the base station may extract signals from resources allocated for RSs and detect at least one RS from the extracted signals. For example, the base station may determine determination indicators corresponding to each candidate sequence based on the extracted signals and each candidate sequence, and detect at least one RS based on the determined determination indicators. In this case, when the base station uses a plurality of reception antennas, signals for each antenna are preprocessed and then summed for each candidate RS used for preprocessing. According to an embodiment, the base station removes a signal sequence corresponding to each candidate RS from the extracted signals, converts it to a time domain signal, determines the size of the time domain signal, and determines the channel power and noise from the size of the time domain signal. Power may be determined, and a plurality of candidate RSs in which a ratio of channel power and noise power exceeds a threshold value may be identified. In other words, the base station performs a correlation operation using a signal sequence corresponding to each candidate RS from the extracted signals, and converts the extracted signals into signals in the time domain. Thereafter, the base station sorts the time-domain signal in order of magnitude, and determines the sample value having the largest value as the channel power or the sum of the sample values around the sample of the maximum value as the channel power. have. In addition, a window having a predetermined size may be set around the sample having the maximum value, and an average of sample values located outside the window may be determined as noise power. According to another embodiment, after calculating correlation values between the extracted signals and each candidate RS, the base station may check a plurality of candidate RSs corresponding to correlation values exceeding a threshold.

In step 1005, the base station determines that at least one of the at least one RS has been received based on a cross-correlation value between candidate RSs. That is, the base station performs a pruning test. A determination index corresponding to an RS that has not been received may be distorted due to a cross correlation value between candidate RSs. Accordingly, the base station can check the detection that is erroneously determined by distortion, that is, the detection corresponding to the FA, in consideration of the cross-correlation value between RSs. According to an embodiment, the base station may determine threshold values corresponding to each of the detected RSs based on the cross-correlation value, and determine whether to finally receive each of the plurality of RSs using the threshold values. For example, the threshold may be determined based on a ratio of the channel power of the RS having the largest channel power among the plurality of detected RSs and the channel power of each RS. According to another embodiment, the base station compensates the determination index of each of the plurality of RSs using cross-correlation values (e.g., subtracts), and determines whether to detect again based on the compensated determination index, so that each of the plurality of RSs It is possible to determine whether or not to receive the final message. For example, the base station removes the contribution due to the cross-correlation value from the channel power value determined in step 1003, and then compares the ratio of the channel power and noise power with the threshold value again to determine whether the corresponding RS is detected. I can. If only one RS is detected in step 1003, step 1005 may be omitted.

As in the embodiment described with reference to FIG. 10, the base station may finally determine whether to receive an RS by performing a first test based on channel power and noise power and a second test based on cross-correlation values. In other words, the base station may finally determine whether to receive the RS based on the cross-correlation value between sequences. Accordingly, the base station can obtain information on an attacker who interferes. For example, the acquired information may include at least one of an attacker's identification information, a resource affected by interference, a propagation delay of an interference signal, and an interference strength.

According to various embodiments, for a pruning test, a cross-correlation peak value between candidate RIM RSs may be predefined. Since candidate sequences usable for candidate RIM RSs are predefined, peak values between RIM RSs including different sequences may also be predefined. Thereafter, when detecting the RIM RS, if it is determined that two or more RIM RSs have been received by the PAPR test, the detector may determine whether at least one RIM RS has been erroneously detected through the pruning test. The detector determines whether the RIM RS that passed the PAPR test is finally detected based on the comparison of the ratio of the channel power and the threshold value to the detected RIM RSs. This pruning test may be repeated for each RIM RS that passes the PAPR test.

For the pruning test, cross-correlation peak values between K RIM RSs and K RIM RSs may be calculated and stored in advance as follows. For example, the cross-correlation peak value may be calculated as in <Equation 1> to <Equation 4> below. Assuming a frequency flat channel, a signal obtained by removing RIM RS k'from the received signal can be expressed as Equation 1 below.

In <Equation 1>, m is the RE index, v _k,k' (m) is the RIM RS k'removed signal value corresponding to the RE of index m, and σ _k (m) is mapped to the RE of index m. The signal value, σ _k' (m), refers to a value mapped to the RE of the index m among values included in RIM RS k'. Here, the RE index m is sequentially assigned from the lowest frequency. For example, the index m of the RE having the lowest frequency is 0, and the index m of the 528 (=44×12)-th RE is 527. A time domain signal can be obtained through an IFFT operation having a size larger than the length of the RIMS RS. The time domain signal can be expressed as in Equation 2 below.

In <Equation 2>. y _k,k' (n) is the nth sample of the time domain signal, N _IFFT is the size of the IFFT operation, N _RS is the length of the RIM RS, m is the RE index, v _k,k' (m) is the index m RIM RS k'corresponding to RE means the removed signal value.

When the direct current (DC) tone is a null carrier and the RIM RS of the sender includes the DC tone, the time domain signal may be expressed as Equation 3 below.

In <Equation 3>. y _k,k' (n) is the nth sample of the time domain signal, N _IFFT is the size of the IFFT operation, N _RS is the length of the RIM RS, m is the RE index, v _k,k' (m) is the index m RIM RS k 'value of the cancellation signal, N' corresponding to RE _RS is RE number of RIM RS having a small index than the DC tone.

A cross-correlation peak value may be determined from the time domain signal. The cross-correlation peak value may be expressed as in Equation 4 below.

In <Equation 4>, ρ(k,k') denotes a cross-correlation peak value, and y _k,k' (n) denotes an nth sample of a time domain signal. ρ(k,k') is the same as ρ(k',k).

Cross-correlation peak values for pairs between combinable candidate RIM RSs may be determined by the operations described with reference to Equations 1 to 4. The determined cross-correlation peak values are stored in the base station and may be used for detection of the RIM RS afterwards. The cross-correlation peak values are used to determine the threshold for the pruning test. For example, the threshold may be determined as in Equation 5 below.

In <Equation 5>, k ^★ is the index of the RIM RS having the highest channel power among RIM RSs that passed the PAPR test, and T_ _PRUNE (k,k ^★ ) is the threshold for the pruning test for RIM RS k , G_ _PRUNE the gain (gain) value for pruning test, ρ (k, k ^★) refers to the cross-correlation peak value RIM RS k and k RIM RS ^★ between the cross-correlation peak value. Here, the gain G_ _PRUNE may be determined according to the desired probability of error detection as a constant which determines the probability of the error detection check pruning.

The pruning test using the threshold value as shown in Equation 5 may be performed as shown in FIG. 11 below.

11 is a flowchart illustrating a pruning test of a base station in a wireless communication system according to various embodiments of the present disclosure. 11 illustrates an operation method of the base station 120.

Referring to FIG. 11, in step 1101, the base station checks whether a plurality of RSs pass the PAPR check. The PAPR test refers to a test based on the ratio of the estimated channel power and noise power assuming reception of the candidate RS. PAPR test can be performed on all candidate RSs.

If a plurality of RSs do not pass the PAPR check, that is, if only one RS passes the PAPR check, in step 1103, the base station finally determines the reception of one RS that has passed the PAPR check. That is, since a plurality of RSs have not been detected, the pruning test may be omitted.

If the plurality of RSs pass the PAPR test, in step 1105, the base station checks the index of the RS having the maximum channel power value among the RSs that pass the PAPR test. Since the channel power values of each candidate RS are calculated by the PAPR test, the base station searches for a maximum value among channel power values of RSs that have passed the PAPR test, and checks the index of a sequence included in the RS corresponding to the maximum value.

In step 1107, the base station finally determines the reception of the RS having the maximum value. In other words, the base station determines that the detection of the RS having the maximum channel power value among RSs that have passed the PAPR test is not FA. This is because even if there is a distortion of the channel power due to cross-correlation between RSs, it is expected that the channel power of the RS for which the distortion is not received will not be greater than the channel power of the received RS.

In step 1109, the base station determines a pruning threshold for the n-th RS among the remaining RSs. The pruning threshold may be determined based on a cross-correlation value between the n-th RS and the RS having the maximum channel power. Here, the cross correlation value may be one of a peak value, an average value, and a minimum value of the cross correlation, or a combination thereof. The pruning threshold may correspond to a value indicating a degree of distortion generated when estimating the channel power of the n-th RS by reception of the RS having the maximum channel power. For example, the pruning threshold is a value obtained by multiplying the ratio of the'cross-correlation value between the n-th RS and the RS having the maximum channel power' and the'auto correlation value of the RS having the maximum channel power' by a constant weight. Can be determined. Specifically, the pruning threshold may be determined as in <Equation 5>.

In step 1111, the base station checks whether the ratio of the channel power value and the maximum channel power value of the n-th RS is less than or equal to the pruning threshold. The ratio of the channel power values is compared because the pruning threshold is defined as the ratio of correlation values. Therefore, when the shape of the pruning threshold is different, the value to be compared may be different.

If the ratio of the channel power value of the n-th RS and the maximum channel power value is less than or equal to the pruning threshold, in step 1113, the base station determines that the detection of the n-th RS is FA. In other words, it is determined that the pass of the PAPR test of the n-th RS is FA. Accordingly, the n-th RS is excluded from the final detection determination.

If the ratio of the channel power value of the n-th RS and the maximum channel power value is not less than the pruning threshold, the base station finally determines the reception of the n-th RS in step 1115. That is, the base station determines that the estimated channel power for the n-th RS is sufficiently large even if the distortion due to cross-correlation is considered.

In step 1117, the base station checks whether all remaining RSs have been determined. In other words, the base station checks whether an RS that has not undergone a pruning test remains. If the determination of all the remaining RSs is not completed, the base station increases n by 1, and then returns to step 1109.

In the embodiment described with reference to FIG. 11, the determination of step 1111 may be expressed as Equation 6 below.

In <Equation 6>, k ^★ is the index of the RIM RS having the highest channel power among RIM RSs that passed the PAPR test, P(k) is the channel power value corresponding to RIM RS k, and G_ _PRUNE is pruning. The gain value for the test, ρ(k,k ^★ ) means the cross-correlation peak value between the cross-correlation peak values RIM RS k and RIM RS k ^★ .

When the values used for the determination of step 1111 are expressed in the dB domain, Equation 6 can be expressed as Equation 7.

In <Equation 7>, k ^★ is the index of the RIM RS having the largest channel power among RIM RSs that passed the PAPR test, P(k) is the channel power value corresponding to RIM RS k, and G_ _{PRUNE_DB} is pruning. The gain value, ρ(k,k ^★ ) at the dB scale for the test means a cross-correlation peak value between the cross-correlation peak values RIM RS k and RIM RS k ^★ .

In the embodiment described with reference to FIG. 11, the determination of step 1111 is performed based on channel power. According to another embodiment, noise power may be further used. For example, instead of channel power, a ratio of channel power and noise power may be used. In this case, the determination of step 1111 may be expressed as in Equation 6 below.

In <Equation 8>, k ^★ is the index of the RIM RS having the largest SNR among RIM RSs that have passed the PAPR test, P(k) is the channel power value corresponding to RIM RS k, and N(k) is the RIM Noise power value corresponding to RS k, G_ _PRUNE is the gain value for pruning test, ρ(k,k ^★ ) is the cross correlation peak value RIM RS k and RIM RS k ^★ cross correlation peak value do.

When values used for the determination of step 1111 are expressed in the dB domain, Equation 8 can be expressed as Equation 9.

In <Equation 9>, k ^★ is the index of the RIM RS having the largest SNR among RIM RSs that have passed the PAPR test, P(k) is the channel power value corresponding to the RIM RS k, and N(k) is the RIM Noise power value corresponding to RS k, G_ _{PRUNE_DB} is the gain value at dB scale for pruning test, ρ(k,k ^★ ) is the cross-correlation peak value RIM RS k and RIM RS k ^★ Means the cross-correlation peak value.

In the judgment operation expressed in <Equation 6> to <Equation 9>, the threshold is the pruning threshold is'the cross-correlation value between the n-th RS and the RS having the maximum channel power' It was expressed as a value obtained by multiplying the ratio of'correlation value' by a certain weight. However, according to various embodiments, the threshold may be variously defined, and it is obvious that the present invention is not limited to the threshold expressed in Equations 6 to 9.

12A illustrates an FA probability and an error detection probability according to a pruning test performed when one RIM RS is received in an environment using 8 candidate RIM RSs. Referring to FIG. 12A, it is confirmed that the FA probability is maintained at 0.01 or less, and the error detection probability is maintained at 0.01 or less by the pruning test even if the reception antenna or SNR increases.

12B shows a probability of a detection error according to a pruning test performed when one RIM RS is received in an environment using 8 candidate RIM RSs. Referring to FIG. 12B, although the probability of error detection is lowered by the pruning test, it is confirmed that there is no performance degradation for the worst detection probability and the average detection probability.

13A shows an FA probability and an error detection probability according to a pruning check when two RIM RSs are received in an environment using eight candidate RIM RSs. Referring to FIG. 13A, it is confirmed that the FA probability is maintained at 0.01 or less, and the error detection probability is maintained at 0.01 or less by the pruning test even if the reception antenna or SNR increases.

13B shows a probability of a detection error according to a pruning check when two RIM RSs are received in an environment using 8 candidate RIM RSs. Referring to FIG. 13B, although the probability of error detection is lowered by the pruning test, it is confirmed that there is no performance degradation for the worst detection probability and the average detection probability.

As described above, when at least one RIM RS is received through the pruning test, an error of erroneously determining that an RIM RS that has not been received may be reduced. For this reason, it is possible to have very good RIM RS detection performance of a detector using a plurality of reception antennas.

14 illustrates a functional configuration of a base station for detecting RIM RS in a wireless communication system according to various embodiments of the present disclosure. Components illustrated in FIG. 14 may be understood as a part of the wireless communication unit 210 and the control unit 240 illustrated in FIG. 2.

14 is compared with FIG. 6, the power calculation units 608a and 608b and the scaling units 610a and 610b are replaced with a covariance matrix estimation unit 1408 and a spatial whitening unit 1410 An exemplary configuration of the base station is shown.

Each of the frequency shifting unit 1402a, the FFT calculation unit 1404a, and the RE demapping unit 1406a of FIG. 14 is a frequency shifting unit 602a, an FFT calculation unit 604a, and a RE demapping unit 606a of FIG. Can correspond to each of ).

Each of the frequency shifting unit 1402b, the FFT calculation unit 1404b, and the RE demapping unit 1406b of FIG. 14 is a frequency shifting unit 602b, an FFT calculation unit 604b, and a RE demapping unit 606b of FIG. Can correspond to each of ).

The covariance matrix operator 1408 of FIG. 14 may calculate a covariance matrix C _r for RIM RS. In an embodiment, the covariance matrix C _r may also be referred to as a spatial covariance matrix.

In an embodiment, the covariance matrix operator 1408 may calculate a covariance matrix C _r for signals extracted from N _RX * K REs for RIM RS. Here, N _RX may represent the number of antennas. Here, N _RX may represent the number of receive antennas. Here, K may represent the number of subcarriers.

In an embodiment, the covariance matrix operator 1408 may calculate a covariance matrix C _r having a size of N _RX * N _RX . In one embodiment, each element of a covariance matrix (C _r ) of size N _RX * N _RX is a covariance between a signal of an antenna corresponding to a row number of the element and a signal of an antenna corresponding to a column number. Can represent a value. In an embodiment, the value of the signal of the antenna may be identified based on values of signals extracted from K REs. In one embodiment, the value of the signal of the antenna may include an average value, a weighted average value, an sum value, or a combination of signals extracted from K REs.

The spatial whitening unit 1410 of FIG. 14 may perform spatial whitening on the RIM RS. In an embodiment, the spatial whitening unit 1410 may perform spatial whitening on the RIM RS based on the covariance matrix C _r of the covariance matrix operator 1408.

In an embodiment, the spatial whitening unit 1410 may perform spatial whitening on signals extracted from N _RX REs for each of K subcarriers. In an embodiment, the spatial whitening unit 1410 may perform spatial whitening on signals r _k extracted from N _RX REs for an arbitrary k-th subcarrier. In an embodiment, k may have an integer value between k ₀ and k ₀ + K-1. In an embodiment, k ₀ may represent the first subcarrier among K subcarriers. In an embodiment, k ₀ + K-1 may represent the last (ie, K-th) subcarrier among K subcarriers.

In an embodiment, the spatial whitening unit 1410 may perform spatial whitening based on a covariance matrix C _r on signals r _k for an arbitrary k-th subcarrier. In one embodiment, the spatial whitening unit 1410 multiplies a square root inverse matrix of a covariance matrix C _r with respect to signals r _k for an arbitrary k-th subcarrier, thereby performing spatial Whitening can be performed.

_k)를 획득할 수 있다. In an embodiment, the spatial whitening unit 1410 performs spatial whitening on the signals r _k of an arbitrary k-th subcarrier, so that a whitened signal (

_k ) can be obtained.

_k)를 획득할 수 있다.In one embodiment, the space whitening unit 1410, based on Equation 10 below, the whitening signal (

_k ) can be obtained.

_k는 k번째 부반송파에 대한 미백 신호를 나타낼 수 있다. 일 실시 예에서,

_k는 N_RX의 차원을 가지는 벡터일 수 있다. 수학식 10에서, r_k는 k번째 부반송파 상의 수신 신호들을 나타낼 수 있다. 일 실시 예에서, r_k는 N_RX의 차원을 가지는 벡터일 수 있다. 수학식 10에서,

는 공분산 행렬(C_r)에 대한 제곱근 역행렬을 나타낼 수 있다. 일 실시 예에서,

는 N_RX * N_RX 크기를 가질 수 있다. 일 실시 예에서, 공분산 행렬(C_r)에 대한 제곱근 역행렬의 연산은, 공분산 행렬 연산부(1408), 또는 공간 미백부(1410)에서 수행될 수 있다. In Equation 10,

_k may represent a whitening signal for the k-th subcarrier. In one embodiment,

_k may be a vector having a dimension of N _RX . In Equation 10, r _k may represent received signals on the k-th subcarrier. In an embodiment, r _k may be a vector having a dimension of N _RX . In Equation 10,

May represent the square root inverse matrix of the covariance matrix (C _r ). In one embodiment,

May have size N _RX * N _RX . In an embodiment, the calculation of the square root inverse matrix on the covariance matrix C _r may be performed by the covariance matrix operation unit 1408 or the spatial whitening unit 1410.

In one embodiment, the spatial whitening unit 1410 is a RIM RS-1 removing unit 1412a-1, RIM RS-K removing unit 1412a-K, and RIM RS-1 removing unit corresponding to K whitening signals (1412b-1) and RIM RS-K removal unit 1412b-K.

Each of the RIM RS-1 removal unit 1412a-1 and the RIM RS-K removal unit 1412a-K of FIG. 14 is a RIM RS-1 removal unit 612a-1 and RIM RS- It may correspond to each of the K removal units 612a-K. Each of the RIM RS-1 removal unit 1412b-1 and the RIM RS-K removal unit 1412b-K in FIG. 14 is a RIM RS-1 removal unit 612b-1 and RIM RS- It can correspond to each of the K removal units 612b-K. Each of the IFFT calculation units 1414a-1, 1414a-K, 1414b-1, and 1414b-K of FIG. 14 is a function of the IFFT calculation units 614a-1, 614a-K, 614b-1, 614b-K of FIG. Can correspond to each. Each of the square operation units 1416a-1, 1416a-K, 1416b-1, and 1416b-K in FIG. 14 is in each of the square operation units 616a-1, 616a-K, 616b-1, and 616b-K in FIG. Can respond. Each of the summing units 1418-1 and 1418-K of FIG. 14 may correspond to each of the summing units 618-1 and 618-K of FIG. 6. Each of the peak detection units 11420-1 and 1420-K of FIG. 14 may correspond to each of the peak detection units 620-1 and 620-K of FIG. 6. Each of the noise estimation units 1422-1 and 1422-K of FIG. 14 may correspond to each of the noise estimation units 622-1 and 622-K of FIG. 6. Each of the comparison units 1424-1 and 1424-K of FIG. 14 may correspond to each of the comparison units 624-1 and 624-K of FIG. 146. The determination unit 1426 of FIG. 14 may correspond to the determination unit 626 of FIG. 6.

15 is a flowchart illustrating a space whitening performed by a base station in a wireless communication system according to various embodiments of the present disclosure.

Referring to FIG. 15, in step 1510, the base station may estimate a covariance matrix (C _r ) for signals extracted from N _RX * K REs for RIM RS.

)을 연산할 수 있다.In step 1520, the base station, the square root inverse matrix for the covariance matrix (C _r ) (

) Can be calculated.

In step 1530, the base station may set the subcarrier index k to k ₀ .

)로 승산(multiply)할 수 있다. 1540 단계에서, 기지국은, 승산함으로써, k번째 부반송파의 미백(whitened) 신호(

_k)를 획득할 수 있다.In step 1540, the base station extracts the signals r _k extracted from the N _RX REs of the k-th subcarrier in the square root inverse matrix (

) Can be multiplyed. In step 1540, the base station, by multiplying, the whitened signal of the k-th subcarrier (

_k ) can be obtained.

In step 1550, the base station may increase the subcarrier index k by 1.

In step 1560, the base station may determine whether the subcarrier index k is _equal to k ₀ + K.

If it is determined in step 1560 that the subcarrier index k is equal to k ₀ + K (determining'Yes'), the operation according to FIG. 15 may be terminated. If it is determined in step 1560 that the subcarrier index k is not equal to k ₀ + K (determining'No'), step 1540 may be performed again.

16A shows an error detection probability according to spatial whitening performance when one RIM RS is received in an environment using 8 candidate RIM RSs. 16B shows the probability of a detection failure according to spatial whitening when one RIM RS is received in an environment using 8 candidate RIM RSs.

Referring to FIG. 16A, the probability of error detection when performing spatial whitening (1x2 W, 1x4 W, 1x8 W, 1x16 W, 1x32 W) is maintained below 0.01 even when the SNR increases or the number of receiving antennas increases. Confirmed.

Referring to FIG. 16B, when performing space whitening, the probability of detection failure (1x2 W, 1x4 W, 1x8 W, 1x16 W, 1x32 W) (probability of loss) slightly increases compared to the case where space whitening is not performed. I can. That is, in terms of the probability of detection failure, it can be seen that there is some deterioration in performance when space whitening is performed compared to when space whitening is not performed.

As described above, when at least one RIM RS is received through space whitening, an error of erroneously determining that a RIM RS that has not been received may be reduced. For this reason, it is possible to have very excellent RIM RS detection performance of a detector using a plurality of reception antennas.

The methods according to the embodiments described in the claims or the specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in a computer-readable storage medium are configured to be executable by one or more processors in an electronic device (device). The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

These programs (software modules, software) include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (electrically erasable programmable read only memory, EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of It may be stored in an optical storage device or a magnetic cassette. Alternatively, it may be stored in a memory composed of a combination of some or all of them. In addition, a plurality of configuration memories may be included.

In addition, the program is through a communication network composed of a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. It may be stored in an attachable storage device that can be accessed. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. In addition, a separate storage device on the communication network may access a device performing an embodiment of the present disclosure.

In the above-described specific embodiments of the present disclosure, components included in the disclosure are expressed in the singular or plural according to the presented specific embodiments. However, the singular or plural expression is selected appropriately for the situation presented for convenience of description, and the present disclosure is not limited to the singular or plural constituent elements, and even constituent elements expressed in plural are composed of the singular or in the singular. Even the expressed constituent elements may be composed of pluralities.

Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure is limited to the described embodiments and should not be determined, and should be determined by the scope of the claims as well as the equivalents of the claims to be described later.

Claims (22)

In the method of operating a base station in a wireless communication system,
A process of receiving signals through resources allocated for RS (reference signals) for interference measurement, and
A process of detecting at least one RS based on the signals, and
And determining that at least one of the at least one RS has been received based on cross-correlation values between candidate RSs.
The method according to claim 1,
The process of detecting the at least one RS,
A process of preprocessing signals for each antenna received through a plurality of antennas, and
And summing the preprocessed signals for each candidate RS used for the preprocessing.
The method according to claim 1,
The process of determining that at least one of the at least one RS has been received,
And determining that the RS having the largest channel power value among the at least one RS is received.
The method according to claim 1,
The process of determining that at least one of the at least one RS has been received,
The process of checking the first RS having the largest channel power value among the at least one RS, and
A process of determining a threshold value corresponding to a second RS among the at least one RS based on the cross-correlation values, and
And determining whether the second RS has been received based on the channel power value of the second RS and the threshold value.
The method of claim 4,
The threshold is determined based on a ratio of a cross-correlation value between the first RS and the second RS and an auto-correlation value of the first RS.
The method of claim 4,
The process of determining whether the second RS has been received,
And determining that the second RS has been received when the ratio of the channel power value of the first RS and the channel power value of the second RS exceeds the threshold value.
The method according to claim 1,
The process of determining that at least one of the at least one RS has been received,
The process of checking the first RS having the largest channel power value among the at least one RS, and
And determining whether to detect the second RS based on a cross-correlation value between the second RS and the first RS among the at least one RS.
The method of claim 7,
The process of determining whether the second RS is detected,
Compensating an index for detection of the second RS based on a cross-correlation value between the second RS and the first RS, and
And determining whether the second RS is detected using the compensated indicator.
The method of claim 8,
The process of compensating for the indicator,
And removing a contribution by a cross-correlation value from the channel power value of the second RS.
The method according to claim 1,
The process of detecting the at least one RS based on the signals,
The process of removing the candidate RS from the signals,
A process of converting a signal from which the candidate RS is removed into a time domain signal,
A process of determining channel power and noise power from the magnitude of the time domain signal,
And checking whether a ratio of the channel power and the noise power exceeds a threshold.
In a base station in a wireless communication system,
A transmitting and receiving unit,
Includes at least one processor connected to the transceiver,
The at least one processor,
Receiving signals through resources allocated for RS (reference signals) for interference measurement,
Detecting at least one RS based on the signals,
A base station determining that at least one of the at least one RS has been received based on cross-correlation values between candidate RSs.
The method of claim 11,
The at least one processor,
Pre-processing each antenna signal received through a plurality of antennas,
A base station for summing preprocessed signals for each candidate RS used for the preprocessing.
The method of claim 11,
The at least one processor determines that the RS having the largest channel power value among the at least one RS has been received.
The method of claim 11,
The at least one processor,
Checking the first RS having the largest channel power value among the at least one RS,
Based on the cross-correlation values, a threshold value corresponding to a second RS among the at least one RS is determined,
A base station that determines whether the second RS has been received based on the channel power value of the second RS and the threshold.
The method of claim 14,
The threshold is determined based on a ratio of a cross-correlation value between the first RS and the second RS and an auto-correlation value of the first RS.
The method of claim 14,
The at least one processor determines that the second RS has been received when a ratio of the channel power value of the first RS and the channel power value of the second RS exceeds the threshold value.
The method of claim 11,
The at least one processor,
Checking the first RS having the largest channel power value among the at least one RS,
A base station determining whether to detect the second RS based on a cross-correlation value between the second RS and the first RS among the at least one RS.
The method of claim 17,
The at least one processor,
Compensating an index for detection of the second RS based on a cross-correlation value between the second RS and the first RS,
A base station that determines whether or not the second RS is detected using the compensated indicator.
The method of claim 18,
The at least one processor, in order to compensate for the indicator, removes a contribution by a cross-correlation value from the channel power value of the second RS.
The method of claim 11,
The at least one processor,
Removing the candidate RS from the signals,
Converting the signal from which the candidate RS is removed into a time domain signal,
Determine channel power and noise power from the magnitude of the time domain signal,
The base station checks whether the ratio of the channel power and the noise power exceeds a threshold.
The method according to claim 1,
The process of receiving the signals,
A process of calculating (estimate) a covariance matrix for the signals,
And performing spatial whitening on the signals based on the covariance matrix.
The method of claim 11,
The at least one processor,
Estimate the covariance matrix on the signals,
A base station that performs spatial whitening on the signals based on the covariance matrix.

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