KR102857564B1 - Apparatus and method for detecting interference between base stations in wireless communication system - Google Patents

Abstract

The present disclosure relates to a 5G ( ^5th generation) or pre-5G communication system for supporting a higher data transmission rate than a 4G ( ^4th generation) communication system such as LTE (Long Term Evolution). The present disclosure relates to a method for detecting interference between base stations in a wireless communication system, and an operating method of a base station may include a process of receiving signals through resources allocated for RSs (reference signals) for interference measurement, a process of detecting at least one RS based on the signals, and a process of determining at least one of the at least one RS as received based on cross-correlation values between candidate RSs.

Description

{APPARATUS AND METHOD FOR DETECTING INTERFERENCE BETWEEN BASE STATIONS IN WIRELESS COMMUNICATION SYSTEM}

The present disclosure relates generally to wireless communication systems, and more particularly to devices and methods for detecting interference between base stations in a wireless communication system.

To meet the growing demand for wireless data traffic following the commercialization of 4G ( ^4th generation) communication systems, efforts are being made to develop improved 5G ( ^5th generation) communication systems, or pre-5G communication systems. For this reason, 5G communication systems, or pre-5G communication systems, are also referred to as "Beyond 4G Network" communication systems or "Post-LTE" systems.

To achieve high data rates, 5G communication systems are being considered for implementation in ultra-high frequency (mmWave) bands (e.g., the 60 GHz band). To mitigate radio path loss and increase the transmission range of radio waves in ultra-high frequency bands, beamforming, massive MIMO (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antenna technologies are being discussed in 5G communication systems.

Additionally, to improve the network of the system, technologies such as evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, moving networks, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation are being developed in 5G communication systems.

In addition, advanced coding modulation (ACM) methods such as Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), as well as advanced access technologies such as Filter Bank Multi Carrier (FBMC), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA), are being developed in 5G systems.

In various wireless communication systems, including 5G systems, interference between devices performing wireless communication (e.g., base stations, terminals) can occur at any time. The type of interference can be defined in various ways depending on the relationship between the devices in an indirect relationship. Since interference degrades communication quality, it is desirable to appropriately control it.

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

Additionally, the present disclosure provides a device and method for improving interference detection performance in a wireless communication system.

Additionally, the present disclosure provides a device and method for reducing the probability of false judgment 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 may include a process of receiving signals through resources allocated for RSs (reference signals) for interference measurement, a process of detecting at least one RS based on the signals, and a process of determining at least one of the at least one RS as received based on cross-correlation values between candidate RSs.

According to various embodiments of the present disclosure, a base station in a wireless communication system includes a transceiver and at least one processor connected to the transceiver. The at least one processor may receive signals through resources allocated for RSs (reference signals) for interference measurement, detect at least one RS based on the signals, and determine at least one of the at least one RS as received based on cross-correlation values between candidate RSs.

The devices and methods according to various embodiments of the present disclosure can reduce the probability of false judgment for interference signals.

The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

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

The terms used in this disclosure are used only to describe specific embodiments and may not be intended to limit the scope of other embodiments. The singular expression 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 those of ordinary skill in the art described in this disclosure. Terms defined in general dictionaries among the terms used in this disclosure may be interpreted as having the same or similar meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined in this disclosure. In some cases, even if a term is defined in this disclosure, it cannot be interpreted to exclude embodiments of the present disclosure.

The various embodiments of the present disclosure described below illustrate a hardware-based approach as an example. However, since the various embodiments of the present disclosure include techniques utilizing both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

The present disclosure relates to a device and method for detecting interference between base stations in a wireless communication system. Specifically, the present disclosure describes a technique for reducing the probability of falsely determining the presence or absence of a signal for measuring interference in a wireless communication system.

The terms used in the following description, including terms referring to signals, channels, control information, network entities, and device components, are provided for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

Additionally, in the present disclosure, expressions such as "more than" and "less than" are used to determine whether a specific condition is satisfied or fulfilled. However, this is merely a description to express an example and does not exclude descriptions of more than or less than. Conditions described as "more than" may be replaced with "more than," conditions described as "less than" may be replaced with "less than," and conditions described as "more than and less than" may be replaced with "more than and less than."

Additionally, while this disclosure describes various embodiments using terminology used in certain communication standards (e.g., 3rd Generation Partnership Project (3GPP)), these are merely illustrative examples. The various embodiments of this disclosure can be easily modified and applied to other communication systems.

FIG. 1 illustrates a wireless communication system according to various embodiments of the present disclosure. Referring to FIG. 1, the wireless communication system includes a base station (110) and a base station (120). FIG. 1 illustrates the base station (110) and the base station (120), but other base stations may be 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 geographical area based on the distance at which a signal can be transmitted. The base station (110) and the base station (120) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', '5th generation node', 'next generation nodeB (gNB)', 'wireless point', 'transmission/reception point (TRP)', or other terms having equivalent technical meanings, in addition to the base station. In some cases, the base station may be referred to as a 'cell'.

The base station (110) can transmit or receive signals according to frames (112). The base station (120) can transmit or receive signals according to 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 section may include at least one downlink subframe, slot, or symbol, and the uplink section may include at least one uplink subframe, slot, or symbol. The gap section may be understood as at least one symbol remaining in a flexible slot or symbol, or a special subframe, excluding a downlink pilot time slot (DwPTS) and an uplink pilot time slot (UpPTS).

Under certain climatic conditions, the Earth's atmosphere at high altitudes has a low density and therefore a low refractive index, which causes signals to bend toward the Earth. In these situations, refraction and reflection occur across the low-refractive index atmosphere, forcing the signal to propagate along a layer of relatively high refractive index. This propagation mechanism, called atmospheric waveguide, causes radio signals to experience small attenuation and reach long distances far beyond their normal radiative range. This phenomenon typically occurs during seasonal transitions between spring and summer and summer and fall on continents, and can occur in winter along coastal areas. This phenomenon is known to occur across the frequency range of 0.3 GHz to 30 GHz.

When a TDD (time division duplex) method with uplink and downlink in a single spectrum is used, a gap period exists to avoid interference between the uplink and downlink. However, when the aforementioned wave propagation phenomenon occurs, the wireless signal can travel a very long distance, and the propagation delay time of the wireless signal can be longer than the length of the gap period. In this case, the downlink signal of the base station (110) causing interference (hereinafter referred to as the "aggressor") can interfere with the uplink period of a distant base station (120) (hereinafter referred to as the "victim"). This interference can be referred to as remote interference. The farther away the aggressor is from the victim, the more delayed the uplink symbols are received by the victim after the gap period, so more uplink symbols of the victim are affected by the interference.

To determine which base station is transmitting the interference signal, base stations transmit a signal for measurement in the downlink section and simultaneously receive a signal in the uplink section to determine which base station is the source of the interference. The signal for measuring interference between base stations can be referred to as a "RIM (remote interference management) reference signal (RS)." Therefore, a technique is needed for the receiving base station to detect which RIM RS has been received.

A RIM RS may include one sequence among a set of candidate sequences including a plurality of sequences. Here, the fact that the RIM RS includes a sequence means that the RIM RS is generated based on the sequence, and for example, the RIM RS may be obtained by modulating the sequence (e.g., quadrature phase shift keying (QPSK) modulation). For example, the sequences may be defined based on a gold sequence having a robust alignment characteristic. Therefore, the operation of detecting a RIM RS means the operation of determining which sequence among the candidate sequences the transmitter transmitted the RIM RS including. That is, the detection of a RIM RS is the operation of determining the index k of the sequence included in the received RIM RS. In the present disclosure, 'detecting a RIM RS' and 'detecting a sequence' may be used interchangeably with each other as having the same meaning. 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'.

FIG. 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 may be understood as a configuration of a base station (110 or 120). Terms such as "... unit" and "... unit" used hereinafter refer to a unit that processes at least one function or operation, which may be implemented by hardware, 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 via a wireless channel. For example, the wireless communication unit (210) performs a conversion function between baseband signals and bit streams according to the physical layer specifications of the system. For example, when transmitting data, the wireless communication unit (210) encodes and modulates the transmitted bit stream to generate complex symbols. Additionally, when receiving data, the wireless communication unit (210) restores the received bit stream by demodulating and decoding the baseband signal.

In addition, the wireless communication unit (210) upconverts a baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts an 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), etc. In addition, the wireless communication unit (210) may include a plurality of transmission and reception paths. Furthermore, 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 may be composed of a plurality of sub-units depending on operating power, operating frequency, etc. The digital unit may be implemented with at least one processor (e.g., 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." Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean that the wireless communication unit (210) performs the processing described above.

The backhaul communication unit (220) provides an interface for performing communication with other nodes within the network. That is, the backhaul communication unit (220) converts a bit string transmitted from a base station to another node, such as 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 into a bit string.

The storage unit (230) stores data such as basic programs, application programs, and setting information for the operation of the base station. The storage unit (230) may be composed of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. In addition, the storage unit (230) provides stored data upon request from the control unit (240).

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

According to one embodiment, the control unit (240) detects whether a RIM RS is received and the index of the sequence included in the received RIM RS. The control unit (240) can determine which sequence of the RIM RS has been received using signals extracted from the resource to which the RIM RS is mapped. For example, the control unit (240) can calculate the channel power and noise power corresponding to each sequence candidate, confirm the sequence of at least one received RIM RS based on the channel power and noise power, and perform verification to determine whether the final reception of at least one confirmed sequence has been performed.

For convenience of explanation below, the base station transmitting the RIM RS is referred to as a 'sender', and the base station determining the source of interference through the RIM RS is referred to as a 'detector'.

According to various embodiments of the present disclosure, the RIM RS transmitted and received can be designed as follows. FIG. 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 the bandwidth (BW) of the transmitter are defined. FIG. 3 exemplifies a first case (310) in which the bandwidth of the transmitter is 20 MHz, and a second case (320) in which the bandwidth of the transmitter is 10 MHz. 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 a low frequency region within the bandwidth, and one RIM RS is mapped to 44 RBs in a high frequency region. In the second case (320) in which 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 central frequency range.

The RIM RS, as shown in Fig. 3, is designed to take into account various combinations of the center frequencies and bandwidths of the transmitter and detector. The RS designed as shown in Fig. 3 can be detected as shown in Figs. 4a to 4c, depending on the center frequency and bandwidth.

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

FIG. 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 a detector in the band having a center frequency of 2310 MHz to detect a signal transmitted at a center frequency of 2320 MHz, a RIM RS is mapped to a lower band having a center frequency of 2320 MHz. In order to maximize the number of RBs to which the RIM RS is mapped, it is preferable that the received signal be located at the frequency of the RB to which the tone corresponding to the lowest frequency of 2311 MHz belongs to the highest frequency tone of the center frequency of 2310 MHz. Accordingly, the number of RBs can be selected as 44. Conversely, in order for a detector in the band having a center frequency of 2320 MHz to detect a signal transmitted at a center frequency of 2310 MHz, a RIM RS is mapped to a higher band having a center frequency of 2310 MHz. To maximize the number of RBs in the RIM RS, it is desirable to map to the RIM RS from the lowest frequency tone of 2311.095 MHz to the highest frequency tone with a center frequency of 2310 MHz. Therefore, the number of RBs can be selected as 44.

Fig. 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. It is confirmed that it is preferable that no RIM RS is mapped to three RBs in the high band of the 2325 MHz center frequency in order for a detector in the 2320 MHz band to detect a signal transmitted at a center frequency of 2325 MHz. Fig. 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. It is confirmed that it is preferable that no RIM RS is mapped to three RBs in the low band of the 2305 MHz center frequency in order for a detector in the 2310 MHz band to detect a signal transmitted at a center frequency of 2305 MHz. Referring to FIGS. 4b and 4c, it is confirmed that it is desirable for a base station using a 10 MHz bandwidth to map RIM RSs to the 44 RBs in the middle.

FIG. 5 illustrates an example of a receiving 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) (e.g., two normal CPs) is added to two net OFDM symbols. Specifically, the Ncp samples (519) at the rear of the first net OFDM symbol are added as the CP (511) of the first net OFDM symbol, and the Ncp samples (529) at the rear of the second net OFDM symbol are added as the CP (521) of the second net OFDM symbol. Here, the Ncp samples (512) at the front of the first net OFDM symbol are identical to the CP (521) of the second net OFDM symbol. In addition, the Ncp samples (512) of the first sequential OFDM symbol and the Ncp samples (513) following it are identical to the CP (521) of the second sequential OFDM symbol and the Ncp samples (522) of the second sequential OFDM symbol. Consequently, the structure of the RIM RS can be understood as being identical to adding a CP of 2×Ncp length to a sequential OFDM symbol of double length.

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

As described above, a detector can detect a RIM RS transmitted by a transmitter. To detect a RIM RS, the detector estimates the channel power and noise power in the resources (e.g., RBs) to which the RIM RS is mapped for each sequence, and then compares the ratio of the channel power and noise power for each sequence with a threshold (e.g., T _PAPR ), thereby determining whether the sequence has been transmitted.

Although detection performance for a specific RIM RS is important, a false alarm can be made due to noise reception even when no RIM RS is received. A situation where a false alarm occurs can be referred to as a 'false alarm (FA)'. For example, if the detector determines that a specific sequence has been received even though the sender has not transmitted any sequence, this is a situation where an FA has occurred. Alternatively, if the detector determines that two or more sequences have been received even though the sender has transmitted one sequence, this is also a situation where an FA has occurred. The probability of an FA occurring, i.e., the probability that a sequence that was not transmitted is incorrectly determined to have been detected, can be referred to as the 'FA probability'.

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

It is necessary to improve detection performance while maintaining the FA probability below a certain level. Simultaneously, it is necessary to improve detection performance while maintaining the probability of error detection (determining that RIM RS q (≠k) is received when RIM RS k is received) below a certain level. In other words, it is necessary to improve detection performance while maintaining the detection probability above a certain level.

FIG. 6 illustrates the 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 part of the wireless communication unit (210) and 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 transmitter and the center frequency of the detector may not be an integer multiple of the tone spacing (e.g., 15 kHz in FIGS. 4A, 4B, and 4C). Therefore, an operation is required to align the received signal to a frequency grid corresponding to the tone spacing of the detector. Accordingly, the frequency shifting unit (602a) aligns the signal passing through the receiving antenna to the frequency grid. The grid mismatch may occur because the transmitter 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 shifting, but the terminal upshifts the uplink signal by 7.25 kHz, so the base station receiving the uplink signal performs a -7.25 kHz downshift to compensate for the shift, which may cause the grid mismatch. Additionally, grid mismatch may occur because the width and center frequency of the transmitter's channel spectrum and the receiver's channel spectrum may differ. However, if no frequency shift is applied between the uplink and downlink signals, the frequency shifting section (602a) may be omitted.

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

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

The power calculation unit (608a) calculates power for the RIM RS. The power calculation unit (608a) can calculate power using the magnitude of signals extracted from REs to which the RIM RS is mapped. Information about the calculated power is provided to the scaling unit (610a).

The scaling unit (610a) adjusts the power value for the RIM RS considering the combination. For example, the scaling unit (610a) can divide the power value by a small number if the power value is small, and can divide the power value by a large number if the power value is large. The values for the RIM RS processed for each antenna are then added together. When the noise power of the signal received for each antenna is not uniform, the operation of the scaling unit (610a) is required to combine the signals with the same noise power level.

The aforementioned frequency shifting unit (602a), FFT operation unit (604a), RE demapping unit (606a), power calculation unit (608a), and scaling unit (610a) process a signal received through one antenna. Accordingly, the frequency shifting unit (602b), FFT operation unit (604b), RE demapping unit (606b), power calculation unit (608b), and scaling unit (610b), which process a signal received through another antenna, can perform the same operations as the frequency shifting unit (602a), FFT operation unit (604a), RE demapping unit (606a), power calculation unit (608a), and scaling unit (610a). In FIG. 6, the frequency shifting unit (602b), the FFT operation unit (604b), the RE demapping unit (606b), the power calculation unit (608b), and the scaling unit (610b) are depicted as separate component groups from the frequency shifting unit (602a), the FFT operation unit (604a), the RE demapping unit (606a), the power calculation unit (608a), and the scaling unit (610a), but this is merely a functional representation, and may actually be implemented as separate component groups, or one component group may repeatedly process signals received through multiple 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 operations after scaling are repeatedly performed on K candidate sequences. For convenience of explanation, operations related to a single sequence, for example, sequence with index 1, are described as a representative example.

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

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

The square operation unit (616a-1) can calculate the square of the absolute value of a time-domain signal. By the square operation unit (616a-1), a signal representing power is obtained as the square of the absolute value of the time-domain signal.

As described above, the RIM RS-1 removal unit (612a-1), the IFFT operation unit (614a-1), and the squaring operation unit (616a-1) perform preprocessing operations to detect RIM RS 1 in a signal received through one antenna. Similar operations may be performed by the RIM RS-K removal unit (612a-K), the IFFT operation unit (614a-K), and the squaring operation unit (616a-K) to detect RIM RS K. In addition, for signals received through other antennas, similar operations may be performed by the RIM RS-1 removal unit (612b-1), the IFFT operation unit (614b-1), the squaring operation unit (616b-1), and by the RIM RS-K removal unit (612b-K), the IFFT operation unit (614b-K), and the squaring operation unit (616b-K). The following operations are performed for each sequence index. For convenience of explanation, operations related to a single sequence, for example, sequence index 1, are described as representative.

The summing unit (618-1) sums the results of preprocessing operations applied to detect RIM RS 1 for signals received through each antenna. That is, signals corresponding to each antenna are summed after preprocessing related to the same candidate sequence by the summing unit (618-1).

The peak detector (620-1) detects at least one peak value in the summed signal. The peak value can be interpreted as channel power. For example, if the size of the IFFT is 1024, the sample with the largest value among the 1024 samples of the summed signal, i.e., the sample with the peak value (hereinafter, referred to as the 'peak sample'), can be regarded as the channel power. Since the channel power spreads around the sample with the peak value, the peak detector (620-1) can set a window of a certain size around the sample with the peak value and estimate the channel power. In the case of a multipath channel, in order to collect channel power for multiple paths, the peak detector (620-1) can find the second peak value, the third peak value, etc. around the peak sample identified above within the window and add them to the channel power component. The location 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 noise power based on the location of the peak value. Since channel power spreads around the sample with the peak value, the noise estimation unit (622-1) can set a window of a certain size around the sample with the peak value and select noise samples without a channel power component. Specifically, the noise estimation unit (622-1) can estimate noise power by averaging the values of samples located outside the window.

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

The judgment on whether RIM RS 1 is received by the peak detection unit (620-1), the noise estimation unit (622-1), and the comparison unit (624-1) is a primary, temporary, or preliminary judgment/detection, and may be referred to as a 'PAPR test', a 'SNR test', a 'first test', or a 'primary test'. Thereafter, the final judgment on whether detection is made may be made by the judgment unit (626). The peak detection unit (620-1), the noise estimation unit (622-1), and the comparison unit (624-1) perform judgment operations for RIM RS 1, and similar operations for other RIM RSs may be performed by the peak detection unit (620-k), the noise estimation unit (622-k), and the comparison unit (624-k).

The judgment unit (626) determines whether at least one RIM RS determined through the PAPR test is finally detected. If one RIM RS is detected through the PAPR test, the judgment unit (626) can finally determine reception of the detected one RIM RS. However, if multiple RIM RSs are detected through the PAPR test, an operation is performed to exclude at least one RIM RS corresponding to FA in consideration of the possibility of occurrence of FA. According to various embodiments, the judgment unit (626) can identify detections that are incorrectly determined due to distortion, i.e., detections corresponding to FA, by considering cross-correlation values between sequences. According to one embodiment, the judgment unit (626) can determine thresholds corresponding to each of the plurality of detected sequences based on the cross-correlation values, and determine whether the final reception of each of the plurality of sequences is performed using the thresholds.

Figure 7a illustrates the FA (false alarm) probability when performing a PAPR test in an environment using one candidate RIM RS. That is, Figure 7a illustrates the FA probability when there is one candidate RIM RS and no RIM RS is actually received. Referring to Figure 7a, when there is one candidate RIM RS, i.e., when the number of available sequences is one, the FA probability is approximately 0.01. When defining a sequence or designing a detection algorithm, it is desirable to maximize the detection probability while maintaining the FA probability below a specific value (e.g., 0.01 in Figure 7).

Fig. 7b illustrates the detection failure probability when receiving a RIM RS in an environment using one candidate RIM RS. That is, Fig. 7b illustrates the detection failure probability (=1-detection probability), or in other words, the missing probability, when a threshold value in the PAPR inspection is used to maintain the FA probability below 0.01 when there is one candidate RIM RS and one received RIM RS. Referring to Fig. 7b, it is confirmed that as the number of receiving antennas increases, the missing probability decreases due to the non-coherent coupling gain at a given SNR (signal to noise ratio).

Unlike the FA probability and detection probability, the error detection probability refers to the probability that n (n > 0) RIM RSs are received, but a different RIM RS is determined to have been received instead of the actually received RIM RS. For example, the error detection probability refers to the probability that RIM RS k is actually received, but RIM RS q (≠k) is determined to have been received. Therefore, the error detection probability can be expressed as a function of the number n of RIM RSs actually received, and the error detection probability value can vary depending on the value of n.

Figure 8a illustrates the FA probability and error detection probability according to PAPR inspection when receiving a single RIM RS in an environment using eight candidate RIM RSs. Referring to Figure 8a, it is confirmed that the FA probability is maintained below 0.01, while the error detection probability increases to a value closer to 1 as the number of receiving antennas increases and the SNR increases.

Figure 8b illustrates the detection failure probability according to PAPR inspection when receiving a single RIM RS in an environment using eight candidate RIM RSs. Referring to Figure 8b, the worst detection probability and the average detection probability do not show a large difference, but it is confirmed that as the number of receiving antennas increases, the missing probability decreases due to non-coherent combining gain at a given SNR.

Figure 9a illustrates the FA probability and error detection probability according to PAPR inspection when receiving two RIM RSs in an environment using eight candidate RIM RSs. Referring to Figure 9a, it is confirmed that the FA probability is maintained below 0.01, while the error detection probability increases to a value closer to 1 as the number of receiving antennas increases and the SNR increases.

Figure 9b illustrates the detection failure probability according to PAPR inspection when receiving a single RIM RS in an environment using eight candidate RIM RSs. Referring to Figure 9b, the worst detection probability and the average detection probability do not show a large difference, but it is confirmed that as the number of receiving antennas increases, the missing probability decreases due to non-coherent combining gain at a given SNR.

As discussed with reference to FIGS. 8B and 9B, in an environment where K candidate RIM RSs are used, even if the detector uses a threshold for PAPR testing that can maintain an appropriate FA probability, a sufficient error detection probability may not be secured using only the PAPR testing technique. Accordingly, the present disclosure describes various embodiments for verifying or pruning RIM RSs determined to have been received through PAPR testing. Through the pruning operation, it is expected that the error detection probability can be reduced without reducing the detection performance. The pruning operation may be referred to as a 'pruning test', a 'second test', or 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, a high pruning performance may be obtained by comparing the ratio of channel power for RIM RS k with the threshold.

FIG. 10 illustrates a flowchart for RIM RS detection of a base station in a wireless communication system according to various embodiments of the present disclosure. FIG. 10 illustrates an operating method of a base station (120).

Referring to FIG. 10, in step 1001, the base station receives a signal through resources allocated for RSs for interference measurement. The RSs for interference measurement may include RIM RSs. The resources allocated for RSs for interference measurement may be identified according to predefined rules. For example, resources (e.g., 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 resources allocated for RSs may include at least one RE within the middle 44 RBs. As another example, when the bandwidth is 20 MHz, the resources allocated for RSs may include at least one RE within the bottom 44 RBs of the lower 10 MHz band or at least one RE within the top 44 RBs of the upper 20 MHz band.

In step 1003, the base station detects at least one RS based on the signals. That is, the base station performs a PAPR test. To detect a sequence, the base station can extract signals from resources allocated for RSs and detect at least one RS from the extracted signals. For example, the base station can determine decision indices corresponding to each candidate sequence based on the extracted signals and each candidate sequence, and detect at least one RS based on the determined decision indices. In this case, when the base station uses multiple receiving antennas, the signals for each antenna are preprocessed and then summed for each candidate RS used for preprocessing. According to one embodiment, the base station can remove a signal sequence corresponding to each candidate RS from the extracted signals, convert them to time-domain signals, determine the magnitude of the time-domain signals, determine channel power and noise power from the magnitude of the time-domain signals, and identify multiple candidate RSs whose ratio of the channel power to the noise power exceeds a threshold. In other words, the base station performs a correlation operation using the signal sequence corresponding to each candidate RS from the extracted signals and converts them to time-domain signals. Thereafter, the base station can sort the time domain signals in order of magnitude, determine the sample value with the largest value as the channel power, or determine the sum of the sample values around the sample with the largest value as the channel power. In addition, a window of a certain size can be set around the sample with the largest value, and the average of the sample values located outside the window can be determined as the noise power. According to another embodiment, the base station can calculate the correlation values between the extracted signals and each candidate RS, and then identify 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 candidate RSs is received based on the cross-correlation values between the candidate RSs. That is, the base station performs a pruning check. The decision indicator corresponding to the RS that is not received may be distorted due to the cross-correlation values between the candidate RSs. Therefore, the base station can check the detection that is incorrectly judged due to the distortion, i.e., the detection corresponding to FA, by considering the cross-correlation values between the RSs. According to one embodiment, the base station can determine thresholds corresponding to each of the plurality of detected RSs based on the cross-correlation values, and determine the final reception status for each of the plurality of RSs using the thresholds. For example, the thresholds can be determined based on the channel power of the RS with the largest channel power among the plurality of detected RSs and the ratio of the channel power of each RS. According to another embodiment, the base station can compensate (e.g., subtract) the decision indicator of each of the plurality of RSs using the cross-correlation values, and determine the detection status again based on the compensated decision indicator, thereby determining the final reception status for each of the plurality of RSs. For example, the base station can re-determine whether the RS is detected by removing the contribution due to the cross-correlation value from the channel power value determined in step 1003 and then comparing the ratio of the channel power and noise power with a threshold. If only one RS is detected in step 1003, step 1005 may be omitted.

As described with reference to FIG. 10, the base station can make a final determination on whether or not an RS is received by performing a primary check based on channel power and noise power and a secondary check based on cross-correlation values. In other words, the base station can make a final determination on whether or not an RS is received based on the cross-correlation value between sequences. Accordingly, the base station can obtain information on an attacker causing interference. For example, the obtained information may include at least one of the following: identification information of the attacker, resources affected by the interference, propagation delay of the interference signal, and intensity of the interference.

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

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

In <Mathematical Formula 1>, m is a RE index, v _k,k' (m) is a signal value with RIM RS k' removed corresponding to the RE of index m, σ _k (m) is a signal value mapped to the RE of index m, and σ _k' (m) means a value mapped to the RE of index m among the 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 with the lowest frequency is 0, and the index m of the 528th (=44×12) RE is 527. A time domain signal can be obtained through an IFFT operation with a size greater than the length of the RIMS RS. The time domain signal can be expressed as in <Mathematical Formula 2> below.

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

If the DC (direct current) tone is a null carrier and the transmitter's RIM RS includes the DC tone, the time domain signal can be expressed as in <Mathematical Formula 3> below.

In <Mathematical Formula 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 removed signal value of the RIM RS k' corresponding to the RE of index m, and N' _RS is the number of REs of the RIM RS having an index smaller than the DC tone.

A cross-correlation peak value can be determined from a time-domain signal. The cross-correlation peak value can be expressed as in <Mathematical Formula 4> below.

In <Mathematical Formula 4>, ρ(k,k') represents the cross-correlation peak value, and y _k,k' (n) represents the nth sample of the time domain signal. ρ(k,k') is identical to ρ(k',k).

Cross-correlation peak values for pairs of combinable candidate RIM RSs can be determined by the operations described with reference to <Mathematical Equations 1> to <Mathematical Equations 4>. The determined cross-correlation peak values are stored in the base station and can be used for subsequent RIM RS detection. The cross-correlation peak values are used to determine a threshold for pruning testing. For example, the threshold can be determined as shown in <Mathematical Equation 5> below.

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

A pruning test using a threshold value such as <Mathematical Formula 5> can be performed as shown in Fig. 11 below.

FIG. 11 illustrates a flowchart for pruning inspection of a base station in a wireless communication system according to various embodiments of the present disclosure. FIG. 11 illustrates an operating method of a base station (120).

Referring to Figure 11, in step 1101, the base station determines whether multiple RSs have passed the PAPR test. The PAPR test assumes reception of a candidate RS and is based on the ratio of estimated channel power to noise power. The PAPR test can be performed on all candidate RSs.

If multiple RSs do not pass the PAPR check, i.e., only one RS passes the PAPR check, then in step 1103, the base station finally determines reception of the one RS that passed the PAPR check. In other words, since multiple RSs were not detected, the pruning check can be omitted.

If multiple RSs pass the PAPR check, in step 1105, the base station determines the index of the RS with the maximum channel power value among the RSs that passed the PAPR check. Since the channel power values of each candidate RS are calculated by the PAPR check, the base station searches for the maximum value among the channel power values of the RSs that passed the PAPR check and determines the index of the sequence included in the RS corresponding to the maximum value.

At step 1107, the base station finally determines reception of the RS with the maximum value. In other words, the base station determines that the detection of the RS with the maximum channel power value among the RSs that passed the PAPR test is not an FA. This is because even if there is channel power distortion due to cross-correlation between RSs, it is expected that the distortion will not increase the channel power of the RS that was not received more than the channel power of the RS that was received.

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

In step 1111, the base station determines whether the ratio of the channel power value of the nth RS to the maximum channel power value is less than or equal to a pruning threshold. The comparison of channel power values is performed because the pruning threshold is defined as a ratio of correlation values. Therefore, if the form of the pruning threshold changes, the values to be compared may also change.

If the ratio of the channel power value and the maximum channel power value of the nth RS is less than or equal to the pruning threshold, then in step 1113, the base station determines that the detection of the nth RS is FA. In other words, it determines that the PAPR test of the nth RS passes FA. Accordingly, the nth RS is excluded from the final detection decision.

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

In step 1117, the base station checks whether the judgment for all remaining RSs has been completed. In other words, the base station checks whether any RSs remain that have not undergone the pruning check. If the judgment for all remaining RSs has not been completed, the base station increments n by 1 and returns to step 1109.

In the embodiment described with reference to FIG. 11, the judgment of step 1111 can be expressed as in <Mathematical Formula 6> below.

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

If the values used for the judgment of step 1111 are expressed in the dB domain, <Mathematical Formula 6> can be expressed as <Mathematical Formula 7>.

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

In the embodiment described with reference to FIG. 11, the decision at step 1111 is performed based on channel power. In other embodiments, noise power may be further utilized. For example, instead of channel power, the ratio of channel power to noise power may be utilized. In this case, the decision at step 1111 may be expressed as in <Mathematical Formula 6> below.

In <Mathematical Formula 8>, k ^★ is the index of the RIM RS having the maximum SNR among the RIM RSs that passed the PAPR test, P(k) is the channel power value corresponding to RIM RS k, N(k) is the noise power value corresponding to RIM RS k, G_ _PRUNE is the gain value for the pruning test, and ρ(k,k ^★ ) means the cross-correlation peak value between RIM RS k and RIM RS k ^★ .

If the values used for the judgment of step 1111 are expressed in the dB domain, <Mathematical expression 8> can be expressed as <Mathematical expression 9>.

In <Mathematical Formula 9>, k ^★ is the index of the RIM RS having the maximum SNR among the RIM RSs that passed the PAPR test, P(k) is the channel power value corresponding to RIM RS k, N(k) is the noise power value corresponding to RIM RS k, G_ _{PRUNE_DB} is the gain value in dB scale for the pruning test, and ρ(k,k ^★ ) means the cross-correlation peak value between RIM RS k and RIM RS k ^★ .

In the judgment operations expressed in <Mathematical Formula 6> to <Mathematical Formula 9>, the threshold, the pruning threshold, is expressed as a value obtained by multiplying a certain weight by the ratio of 'the cross-correlation value between the nth RS and the RS having the maximum channel power' and 'the autocorrelation value of the RS having the maximum channel power'. However, depending on various embodiments, the threshold may be defined in various ways, and it is obvious that the present invention is not limited to the thresholds expressed in <Mathematical Formula 6> to <Mathematical Formula 9>.

Figure 12a illustrates the FA probability and error detection probability according to the pruning check performed when receiving a single RIM RS in an environment using eight candidate RIM RSs. Referring to Figure 12a, it is confirmed that the FA probability is maintained below 0.01, and the error detection probability is maintained below 0.01 by the pruning check even when the receiving antenna or SNR increases.

Figure 12b illustrates the detection error probability according to the pruning check performed when receiving a single RIM RS in an environment using eight candidate RIM RSs. Referring to Figure 12b, it is confirmed that although the error detection probability is lowered by the pruning check, there is no performance degradation in the worst case detection probability and average detection probability.

Figure 13a illustrates the FA probability and error detection probability according to the pruning check performed when receiving two RIM RSs in an environment using eight candidate RIM RSs. Referring to Figure 13a, it is confirmed that the FA probability is maintained below 0.01, and the error detection probability is maintained below 0.01 by the pruning check even when the receiving antenna or SNR increases.

Figure 13b illustrates the detection error probability according to the pruning check performed when receiving two RIM RSs in an environment using eight candidate RIM RSs. Referring to Figure 13b, it is confirmed that although the error detection probability is lowered by the pruning check, there is no performance degradation in the worst case detection probability and average detection probability.

As discussed above, the pruning check can reduce the error of incorrectly determining that a non-received RIM RS has been received when at least one RIM RS has been received. This allows for a detector using multiple receiving antennas to have excellent RIM RS detection performance.

FIG. 14 illustrates the 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. 14 may be understood as part of the wireless communication unit (210) and control unit (240) illustrated in FIG. 2.

FIG. 14 illustrates, as compared to FIG. 6, an exemplary configuration of a base station in which power calculation units (608a, 608b) and scaling units (610a, 610b) are replaced with a covariance matrix calculation unit (1408, covariance matrix estimation unit) and a spatial whitening unit (1410, spatial whitening unit).

Each of the frequency transition unit (1402a), the FFT operation unit (1404a), and the RE demapping unit (1406a) of FIG. 14 may correspond to each of the frequency transition unit (602a), the FFT operation unit (604a), and the RE demapping unit (606a) of FIG. 6.

Each of the frequency transition unit (1402b), the FFT operation unit (1404b), and the RE demapping unit (1406b) of FIG. 14 may correspond to each of the frequency transition unit (602b), the FFT operation unit (604b), and the RE demapping unit (606b) of FIG. 6.

The covariance matrix calculation unit (1408) of FIG. 14 can calculate (estimate) a covariance matrix (C _r ) for RIM RS. In one embodiment, the covariance matrix (C _r ) may also be referred to as a spatial covariance matrix.

In one embodiment, the covariance matrix calculation unit (1408) may calculate a covariance matrix (C _r ) for signals extracted from N _RX * K REs for the RIM RS. Here, N _RX may represent the number of antennas. Here, N _RX may represent the number of receiving antennas. Here, K may represent the number of subcarriers.

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

The spatial whitening unit (1410) of FIG. 14 can perform spatial whitening for the RIM RS. In one embodiment, the spatial whitening unit (1410) can perform spatial whitening for the RIM RS based on the covariance matrix (C _r ) of the covariance matrix calculation unit (1408).

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

In one embodiment, the spatial whitening unit (1410) may perform spatial whitening based on the covariance matrix (C _r ) for the signals (r _k ) for an arbitrary k-th subcarrier. In one embodiment, the spatial whitening unit (1410) may perform spatial whitening by multiplying the signals (r _k ) for an arbitrary k-th subcarrier by the square root inverse matrix of the covariance matrix (C _r ).

In one embodiment, the spatial whitening unit (1410) performs spatial whitening on signals (r _k ) of an arbitrary kth subcarrier, thereby generating a whitened signal ( _k ) can be obtained.

In one embodiment, the space whitening unit (1410) generates a whitening signal ( _k ) can be obtained.

In mathematical equation 10, _k may represent a whitening signal for the kth subcarrier. In one embodiment, _k may be a vector having a dimension of N _RX . In Equation 10, r _k may represent the received signals on the kth subcarrier. In one embodiment, r _k may be a vector having a dimension of N _RX . In Equation 10, can represent the square root inverse matrix for the covariance matrix (C _r ). In one embodiment, may have a size of N _RX * N _RX . In one embodiment, the operation of the square root inverse matrix for the covariance matrix (C _r ) may be performed in the covariance matrix operation unit (1408) or the spatial whitening unit (1410).

In one embodiment, the space whitening unit (1410) can output K whitening signals to the corresponding RIM RS-1 removal unit (1412a-1), RIM RS-K removal unit (1412a-K), RIM RS-1 removal unit (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 may correspond to each of the RIM RS-1 removal unit (612a-1) and the RIM RS-K removal unit (612a-K) of FIG. 6. Each of the RIM RS-1 removal unit (1412b-1) and the RIM RS-K removal unit (1412b-K) of FIG. 14 may correspond to each of the RIM RS-1 removal unit (612b-1) and the RIM RS-K removal unit (612b-K) of FIG. 6. Each of the IFFT operation units (1414a-1, 1414a-K, 1414b-1, 1414b-K) of FIG. 14 may correspond to each of the IFFT operation units (614a-1, 614a-K, 614b-1, 614b-K) of FIG. 14. Each of the square operation units (1416a-1, 1416a-K, 1416b-1, 1416b-K) of FIG. 14 may correspond to each of the square operation units (616a-1, 616a-K, 616b-1, 616b-K) of FIG. 6. Each of the summaries (1418-1, 1418-K) of FIG. 14 may correspond to each of the summaries (618-1, 618-K) of FIG. 6. Each of the peak detection units (1420-1, 1420-K) of FIG. 14 may correspond to each of the peak detection units (620-1, 620-K) of FIG. 6. Each of the noise estimation units (1422-1, 1422-K) of FIG. 14 may correspond to each of the noise estimation units (622-1, 622-K) of FIG. 6. Each of the comparison units (1424-1, 1424-K) of FIG. 14 may correspond to each of the comparison units (624-1, 624-K) of FIG. 146. The judgment unit (1426) of Fig. 14 may correspond to the judgment unit (626) of Fig. 6.

FIG. 15 illustrates a flowchart for performing spatial whitening of a base station in a wireless communication system according to various embodiments of the present disclosure.

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

At step 1520, the base station computes the square _root inverse matrix ( ) can be calculated.

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

At step 1540, the base station extracts the signals (r _k ) from the N _RX REs of the kth subcarrier by the square root inverse matrix ( ) can be multiplied. At step 1540, the base station multiplies the whitened signal of the kth subcarrier ( _k ) can be obtained.

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

At step 1560, the base station can determine whether the subcarrier index k is equal to k ₀ + K.

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

Figure 16a illustrates the probability of error detection when performing spatial whitening upon reception of a single RIM RS in an environment using eight candidate RIM RSs. Figure 16b illustrates the probability of detection failure when performing spatial whitening upon reception of a single RIM RS in an environment using eight candidate RIM RSs.

Referring to Fig. 16a, it is confirmed that the error detection probability (1x2 W, 1x4 W, 1x8 W, 1x16 W, 1x32 W) when performing spatial whitening is maintained at 0.01 or less even when the SNR increases or the number of receiving antennas increases.

Referring to Fig. 16b, when performing spatial whitening, the detection failure probability (1x2 W, 1x4 W, 1x8 W, 1x16 W, 1x32 W) (missing probability) increases somewhat compared to the case where spatial whitening is not performed. That is, in terms of the detection failure probability, it can be seen that there is some performance degradation when spatial whitening is performed compared to the case where spatial whitening is not performed.

As discussed above, spatial whitening can reduce the error of incorrectly determining that a non-received RIM RS has been received when at least one RIM RS has been received. This allows detectors using multiple receiving antennas to achieve excellent RIM RS detection performance.

The methods according to the embodiments described in the claims or 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. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or may be stored in memories formed by a combination of some or all of these. In addition, each configuration memory may include multiple copies.

Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device performing an embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed in the singular or plural form, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

While the detailed description of this disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the described embodiments, but should be defined not only by the scope of the claims described below, but also by equivalents thereof.

Claims (22)

In a method performed by a base station in a wireless communication system,
A step of identifying signals through resources allocated for RIM (remote interference management) RS (reference signals);
A step of detecting a plurality of candidate RSs based on the channel power and noise power of each of the above signals;
A step of determining that a first candidate RS having the maximum channel power value among the plurality of candidate RSs has been received;
A step of determining threshold values based on cross-correlation values between the first candidate RS having the maximum channel power value and candidate RSs excluding the first candidate RS among the plurality of candidate RSs; and
A method comprising: determining whether at least one of the candidate RSs has been received using ratios of channel power values of the candidate RSs to the maximum channel power value and the threshold values.
In claim 1,
The steps of detecting the above multiple candidate RSs are:
A step of preprocessing the signals identified through multiple antennas; and
A method comprising a step of summing the preprocessed signals for each candidate RS used for preprocessing.

delete In claim 1,
A threshold value corresponding to a second candidate RS among the above candidate RSs is determined based on a cross-correlation value between the first candidate RS and the second candidate RS,
A method in which it is determined whether the second candidate RS has been received based on the channel power value of the second candidate RS and the threshold value.
In claim 4,
A method wherein the threshold value is determined based on a ratio between the cross-correlation value and the auto-correlation value of the first candidate RS.
In claim 4,
A method in which the second candidate RS is determined to have been received if the ratio between the channel power value of the second candidate RS and the maximum channel power value exceeds the threshold value.
In claim 1,
A method comprising the step of identifying the first candidate RS having the maximum channel power value among the plurality of candidate RSs.
In claim 7,
A step of compensating an indicator for detection of the second candidate RS based on a cross-correlation value between the first candidate RS and the second candidate RS; and
A method further comprising a step of determining whether the second candidate RS has been detected using the compensated indicator.
In claim 8,
The steps to compensate for the above indicators are:
A method comprising the step of removing a contribution by the cross-correlation value from the channel power value of the second candidate RS.
In claim 1,
The step of detecting the plurality of candidate RSs based on the channel power and the noise power of each of the above signals is:
A step of removing the plurality of candidate RSs from the above signals,
A step of converting a signal obtained by removing the above plurality of candidate RSs into a time domain signal,
A step of determining a first channel power and a first noise power from the magnitude of the above time domain signal, and
A method comprising the step of identifying whether the ratio between the first channel power and the first noise power exceeds a threshold value.
In a wireless communication system, at a base station,
transceiver; and
A controller coupled with the above transceiver,
The above controller:
Identify signals through resources allocated for RIM (remote interference management) RS (reference signals),
Detecting multiple candidate RSs based on the channel power and noise power of each of the above signals,
It is determined that a first candidate RS having the maximum channel power value among the plurality of candidate RSs has been received,
Determine threshold values based on cross-correlation values between the first candidate RS having the maximum channel power value and candidate RSs excluding the first candidate RS among the plurality of candidate RSs,
A base station configured to determine whether at least one of the candidate RSs has been received using ratios of the channel power values of the candidate RSs to the maximum channel power value and the threshold values.
In claim 11,
The above controller:
Preprocessing the signals identified through multiple antennas,
A base station configured to sum the preprocessed signals for each candidate RS used for preprocessing.

delete In claim 11,
A threshold value corresponding to a second candidate RS among the above candidate RSs is determined based on a cross-correlation value between the first candidate RS and the second candidate RS,
A base station, wherein it is determined whether the second candidate RS has been received based on the channel power value of the second candidate RS and the threshold value.
In claim 14,
A base station, wherein the threshold value is determined based on a ratio between the cross-correlation value and the auto-correlation value of the first candidate RS.
In claim 14,
A base station, wherein the second candidate RS is determined to have been received if the ratio between the channel power value of the second candidate RS and the maximum channel power value exceeds the threshold value.
In claim 11,
The above controller:
A base station configured to identify the first candidate RS having the maximum channel power value among the plurality of candidate RSs.
In claim 17,
The above controller:
Compensating an indicator for detection of the second candidate RS based on the cross-correlation value between the first candidate RS and the second candidate RS,
A base station configured to determine whether the second candidate RS is detected using the above-mentioned compensated indicator.
In claim 18,
The above controller:
A base station configured to remove the contribution by the cross-correlation value from the channel power value of the second candidate RS.
In claim 11,
The above controller:
Remove the plurality of candidate RSs from the above signals,
Converting the signal obtained by removing the above multiple candidate RSs into a time domain signal,
Determine the first channel power and the first noise power from the magnitude of the above time domain signal,
A base station, wherein the base station is configured to identify whether the ratio between the first channel power and the first noise power exceeds a threshold value.
In claim 1,
The steps to identify the above signals are:
A step of estimating a covariance matrix for the above signals; and
A method comprising the step of performing spatial whitening on the signals based on the covariance matrix.
In claim 11,
The above controller:
Estimate the covariance matrix for the above signals,
A base station configured to perform spatial whitening on the signals based on the covariance matrix.