Method and apparatus for estimating channel in wireless communication system

Abstract

A method performed by a receiver in a wireless communication system, according to various embodiments of the present disclosure, may comprise the operations of: determining a first channel estimation value on the basis of a demodulation reference signal (DM-RS) symbol in a resource block; detecting a data symbol on the basis of the first channel estimation value; deciding, on the basis of the first data symbol, whether to determine a second channel estimation value; detecting a second data symbol on the basis of the second channel estimation value if it is decided that the second channel estimation value is determined; and performing channel decoding on the second data symbol. Other various embodiments identified through the specification are possible.

Description

Method and device for estimating a channel in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for estimating a channel in a wireless communication system.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz (THz) band (for example, 3 THz band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

[0004] Currently, discussions are underway to improve and enhance the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, and physical layer standardization is in progress for technologies such as V2X (Vehicle-to-Everything) to help autonomous vehicles make driving decisions and increase user convenience based on their own location and status information transmitted by vehicles, NR-U (New Radio Unlicensed) for the purpose of system operation that complies with various regulatory requirements in unlicensed bands, NR terminal low power consumption technology (UE Power Saving), Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, and Positioning.

[0005] In addition, standardization of wireless interface architecture / protocols is in progress for technologies such as intelligent factories (Industrial Internet of Things, IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) that provides nodes for expanding network service areas by integrating wireless backhaul links and access links, Mobility Enhancement technology including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step random access (2-step RACH for NR) that simplifies random access procedures. Standardization is also in progress for system architecture / services such as 5G baseline architecture (e.g., Service-based Architecture, Service-based Interface) for grafting Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) that provides services based on the location of the terminal.

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] According to one embodiment disclosed in the present document, a method performed by a receiver in a wireless communication system may include an operation of determining a first channel estimate value based on a demodulation reference signal (DM-RS) symbol within a resource block, an operation of detecting a first data symbol based on the first channel estimate value, an operation of determining whether to determine a second channel estimate value based on the first data symbol, an operation of detecting a second data symbol based on the second channel estimate value when it is determined to determine the second channel estimate value, and an operation of performing channel decoding on the second data symbol.

[0009] According to one embodiment disclosed in the present document, a device of a receiver in a wireless communication system may include at least one processor, and the at least one processor may be configured to determine a first channel estimation value based on a demodulation reference signal (DM-RS) symbol within a resource block, detect a first data symbol based on the first channel estimation value, determine whether to determine a second channel estimation value based on the first data symbol, detect a second data symbol based on the second channel estimation value when it is determined to determine the second channel estimation value, and perform channel decoding on the second data symbol.

[0010] FIG. 1 illustrates a resource block according to one embodiment of the present disclosure.

[0011] FIG. 2 illustrates the structure of a receiver in a wireless communication system according to one embodiment of the present disclosure.

[0012] FIG. 3 illustrates an operation of a receiver estimating a channel according to one embodiment of the present disclosure.

[0013] FIG. 4 illustrates an operation of a receiver estimating a channel according to one embodiment of the present disclosure.

[0014] FIG. 5 illustrates an operation of a receiver estimating a channel according to one embodiment of the present disclosure.

[0015] FIG. 6 illustrates an operation of a receiver estimating a channel according to one embodiment of the present disclosure.

[0016] FIG. 7 illustrates a frame error rate versus signal-to-noise ratio according to one embodiment of the present disclosure.

[0017] FIG. 8 illustrates a frame error rate versus signal-to-noise ratio according to one embodiment of the present disclosure.

[0018] In connection with the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0019] Various aspects of the claimed subject matter are described with reference to the drawings, wherein like reference numerals are used to designate similar elements. In the following description, for purposes of explanation, specific details are set forth to provide a thorough understanding of one or more embodiments. However, it may be apparent that the embodiments may be practiced without these specific details.

[0020] 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.

[0021] In the following description, terms referring to signals (e.g., message, signal, signaling, sequence, stream), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms for operations (e.g., step, method, process, procedure), terms referring to data (e.g., information, parameter, variable, value, bit, symbol, codeword), terms referring to channels, terms referring to control information (e.g., downlink control information (DCI), medium access control code word element (MAC CE), radio resource control (RRC) signaling), terms referring to network entities, terms referring to components of devices, etc. are used in the description. These terms are provided for convenience. Therefore, the present disclosure is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

[0022] The embodiment disclosed in this document describes the operation of estimating a channel of a receiver in a wireless communication system. For a specific description of the receiver operation, N t N transmitting antenna ports and rAssume a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) or multiple-input multiple-output orthogonal frequency division multiple access (OFDMA) communication system using two receive antenna ports.

[0023] Multiple-Input Multiple-Output (MIMO) communication systems are a technology that can dramatically increase the transmission speed and stability of wireless communications, and are being utilized as a core element technology in various wireless communication systems. To ensure high communication stability in MIMO communication systems, the receiver must accurately understand MIMO channel information. A representative conventional approach for this purpose is RS-based channel estimation using Demodulation Reference Signals (DM-RSs). In this method, the transmitter utilizes some of the wireless resources to transmit DM-RSs already known to the receiver, and the receiver uses this information to estimate the MIMO channel. In general, the accuracy of MIMO channel information obtained through RS-based channel estimation methods improves as the number of DM-RSs increases.

[0024] In MIMO-OFDM communication systems that utilize orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA), accurate MIMO channel estimation must be performed for the time-frequency domain, which consists of multiple subcarriers and OFDM symbols. However, in typical MIMO-OFDM communication systems, DM-RSs are allocated only to a limited number of subcarriers and OFDM symbols. Furthermore, increasing the number of DM-RSs reduces the resources available for data transmission, resulting in a decrease in data transmission capacity. Therefore, arbitrary increases in the number of DM-RSs should be avoided. Consequently, when conventional RS-based channel estimation methods are applied in MIMO-OFDM communication systems, the accuracy of channel information that can be obtained by the receiver is limited. In particular, when the channel varies significantly in the time-frequency domain, the channel estimation accuracy of RS-based channel estimation methods is further reduced. Therefore, in a MIMO-OFDM communication system with a limited DM-RS quantity, there is a need to develop a receiving method and device that can achieve high channel estimation performance even in various channel environments.

[0025] FIG. 1 illustrates a resource block (100) according to one embodiment of the present disclosure. Specifically, FIG. 1 is a diagram illustrating a resource block that illustrates locations of a demodulation reference signal (DM-RS) received by a receiver.

[0026] Referring to FIG. 1, a resource block (100) is composed of K adjacent subcarriers and N adjacent OFDM symbols. A fixed value may be used for the resource block (100) depending on the number of K and N constituting the resource block, and may also be a unit that is adaptively set according to the time domain correlation and frequency domain correlation of the channel. For example, a resource block may be composed of 12 subcarriers and 14 OFDM symbols, wherein K=12 and N=14. In the present disclosure, for the sake of detailed description, the kth subcarrier of the nth OFDM symbol in a resource block is defined as the (n, k)th resource element. Accordingly, each resource block is composed of N×K resource elements.

[0027] In this disclosure, we consider a MIMO-OFDM system employing code division multiplexing (CDM) as a signal multiplexing scheme. Furthermore, this disclosure assumes that demodulation reference signals (DM-RSs), which are already known to the receiver, are transmitted through D resource elements within a resource block to estimate the channel of each CDM group. That is, DM-RSs for different antenna ports located on the same time-frequency resource can be distinguished from each other by orthogonal codes.

[0028] Referring to FIG. 1, a resource block (100) may include CDM group 1 (110) and CDM group 2 (120) for DM-RS. According to one embodiment of the present disclosure, when the number of CDM groups is J, N tThe transmit antenna ports of the dog can be assigned to one of J CDM groups. When code division multiplexing is applied to a resource block, the channel matrix of the (n, k)th resource element can be expressed as in [Mathematical Formula 1] below.

[0029]

[0030] In mathematical equation 1, For the (n,k)th resource element, the transmit antenna ports belonging to the jth CDM group and N r represents a channel matrix formed between the receiving antenna ports of the jth CDM group. According to one embodiment of the present disclosure, the i-th DM-RS transmitted for the j-th CDM group channel estimation is (n j,i ,k j,i ) is transmitted through the th resource element, and at this time, the transmitted DM-RS is can be expressed as . Also, t[n j,i ,k j,i ] of N t All signals transmitted from the transmit antenna ports that do not belong to the jth CDM group among the elements of the dog can have a zero value.

[0031] According to one embodiment of the present disclosure, a receiver (n j,i ,k j,i ) Received signal y[n] detected (or observed) in the th resource element j,i ,k j,i ] can be expressed as in <Mathematical Formula 2> below.

[0032]

[0033] In mathematical expression 2, represents the noise signal received at the (n,k)th resource element.

[0034] In the present disclosure, it is assumed that data symbols are transmitted through resource elements in a resource block in which DM-RS is not transmitted. For example, in FIG. 1, a resource element (130) in which DM-RS is not transmitted among resource elements in a resource block can be a data symbol, and a transmitter can transmit a signal for data to a receiver on the data symbol. According to one embodiment of the present disclosure, a data symbol transmitted through the (n, k)th resource element can be expressed as . Here, A represents a symbol constellation shared in advance between the transmitter and the receiver. The received signal y[n,k], which the receiver detects (or observes) through the (n,k)th resource element where the data symbol is transmitted, can be expressed as in [Mathematical Formula 3].

[0035]

[0036] In mathematical expression 3, represents the frequency domain channel matrix formed for the kth subcarrier of the nth OFDM symbol, and v[n,k]∈ represents the noise signal observed in the kth subcarrier of the nth OFDM symbol.

[0037] According to one embodiment of the present disclosure, a receiver can estimate a channel based on resource elements in which DM-RS and data symbols are transmitted within the resource block of FIG. 1. The specific operation of the receiver estimating the channel is described below with reference to FIG. 2.

[0038] FIG. 2 illustrates the structure (200) of a receiver in a wireless communication system according to one embodiment of the present disclosure. It is assumed that the operations of components within the receiver in FIG. 2 are applied in units of resource blocks as illustrated in FIG. 1. However, it should be noted that the resource block units illustrated in FIG. 1 may be freely defined depending on the system.

[0039] Referring to FIG. 2, the receiver may include an RS-based channel estimation selector (205), an RS group-based channel estimator (210), and an RS-based representative channel estimator (215) to estimate a channel based on DM-RS. In addition, the receiver may include a data symbol detector (220), a data symbol-based channel estimation controller (225), and a data symbol-based channel estimator (230) to estimate a channel based on data symbols. Finally, the receiver may include a channel decoder (235) to recover information bits based on the detected data symbols.

[0040] According to one embodiment of the present disclosure, an RS-based channel estimation selector (205) included in a receiver may determine which channel estimation method to use when the receiver determines a channel estimation value using DM-RSs received from a plurality of antenna ports. For example, the RS-based channel estimation selector (205) may determine which method to use among a method of determining a channel estimation value using an RS group-based channel estimator (210) and a method of determining a representative channel estimation value using an RS-based representative channel estimator (215). Various channel estimation methods may be used as a method of determining a channel estimation value using the RS group-based channel estimator (210) or the RS-based representative channel estimator (215). For example, a method of determining a channel estimation value for each DM-RS group using the RS group-based channel estimator (210) may be represented as a first method. In addition, a method of determining a representative channel estimation value for all DM-RSs using the RS-based representative channel estimator (215) may be represented as a second method.

[0041] The RS-based channel estimation selector (205) can select a channel estimation method with the best performance by comparing the mean squared error (MSE) of the channel estimation values ​​of each channel estimator (210, 215) and selecting a method with a lower MSE as a channel estimation method among the first method for determining a channel estimation value based on an RS group and the second method for determining a representative channel estimation value.

[0042] According to one embodiment of the present disclosure, when the RS-based channel estimation selector (205) selects the first method of determining a channel estimation value using an RS group-based channel estimator (210) as a channel estimation method, the MSE of the RS group-based channel estimation method can be approximated as in [Mathematical Expression 4] below. [Mathematical Expression 4] can represent a value obtained by estimating a channel of a resource element representing a group by grouping adjacent DM-RSs among DM-RSs by applying a least squares technique.

[0043]

[0044] In mathematical equation 4, is the average of the time-frequency correlations between the channel of the (n,k)th resource element and the channels through which DM-RSs used to estimate the channel of the resource element are transmitted, and σ 2 refers to the variance of the noise signal.

[0045] also, represents the square operation of the Frobenius norm, represents the trace matrix operation.

[0046] According to one embodiment of the present disclosure, when a channel estimation value is determined using an RS-based representative channel estimator (215), the MSE of the corresponding channel estimation method can be approximated as in [Mathematical Formula 5] below. [Mathematical Formula 5] can represent a value obtained by determining a channel estimation value representing the entire resource block by simultaneously utilizing all DM-RSs that are not adjacent in the time domain within the resource block for each CDM group by applying the least squares technique.

[0047]

[0048] In mathematical expression 5, means the average value of the time-frequency correlations between the channel of the (n,k)th resource element and the channels through which DM-RSs are transmitted.

[0049] The RS-based channel estimation selector (205) can compare the MSE values ​​calculated according to [Mathematical Equation 4] and [Mathematical Equation 5] to determine the channel method of the channel estimator with the lower MSE as the DM-RS-based channel estimation method. According to one embodiment of the present disclosure, when there are multiple CDM groups, the RS-based channel estimation selector (205) can also determine an RS-based channel estimation method to be used separately for each CDM group.

[0050] According to another embodiment, the RS-based channel estimation selector may determine an RS-based channel estimation method to be commonly used by all CDM groups by summing and comparing the MSE values ​​of all CDM groups. In addition, in addition to the method of determining the channel estimation value of each channel estimator, the RS-based channel estimation selector (205) may also apply an external determination method to predetermine the RS-based channel estimation method to be used by each CDM group.

[0051] When the RS-based channel estimation selector (205) determines to estimate the channel through the RS group-based channel estimator (210), the RS group-based channel estimator (210) can derive a channel estimation value based on the DM-RSs received by the receiver from multiple antenna ports. According to one embodiment of the present disclosure, the RS group-based channel estimator (210) can group the DM-RSs into multiple groups and calculate a channel estimation value for each group to determine the channel estimation value. For example, the RS group-based channel estimator (210) can consider a method of grouping adjacent DM-RSs on a radio resource grid among D DM-RSs into one group and estimating the channel of a resource element representing the group. When the resource element representing a specific DM-RS group is the (n, k)th resource element, the channel estimation value of the (n, k)th resource element estimated using the least squares technique can be expressed as in [Mathematical Formula 6] below.

[0052]

[0053] In mathematical expression 6, is a matrix whose rows are DM-RSs used to estimate the channel of the (n,k)th resource element in the jth CDM group, represents a matrix whose rows are the received signals of DM-RSs used to estimate the channel of the (n,k)th resource element in the jth CDM group. In addition, (·) H represents the Hermitian operation, (·) -1 represents an inverse matrix operation. The RS group-based channel estimator (210) completes channel estimation of resource elements representing each DM-RS group according to the above method, and then applies a linear interpolation technique to the channel estimation values ​​of the DM-RS groups to determine channel estimation values ​​for the remaining resource elements within the resource block.

[0054] When using a method of grouping adjacent DM-RSs into a single group, such as an RS group-based channel estimator (210), and estimating the channel of a representative resource element for each group, changes in channels formed differently for each resource element within a resource block can be reflected. However, this method has a problem in that the number of DM-RSs belonging to each DM-RS group is limited, and this may result in a decrease in the accuracy of channel estimation for each group.

[0055] If the channel estimation selector (205) decides to estimate the channel through the RS-based representative channel estimator (215), the RS-based representative channel estimator (215) can derive a representative channel estimation value that takes into account all DM-RSs received by the receiver from multiple antenna ports. That is, the RS-based representative channel estimator (215) can derive a channel estimation value by determining channel estimation values ​​that represent the entire resource block.

[0056] According to one embodiment of the present disclosure, a method for estimating a channel by determining a representative channel estimate value by an RS-based representative channel estimator (215) may be a method for determining a channel estimate value representing the entire resource block by simultaneously utilizing all DM-RSs that are not adjacent in the time domain within a resource block for each CDM group. For example, with respect to a method for determining a representative channel estimate value using a least squares technique, a representative channel estimate value obtained from the jth CDM group may be expressed as in [Mathematical Formula 7] below.

[0057]

[0058] In mathematical expression 7, is a matrix having all D DM-RSs transmitted for the j-th CDM group channel estimation as rows, represents a matrix having received signals for the corresponding DM-RSs as rows. For another example, if the RS-based representative channel estimator (215) can know the time-frequency correlation information of the channel, if the least squares technique utilizing the correlation information is applied, the representative channel estimation value obtained from the jth CDM group can be expressed as in [Mathematical Formula 8] below.

[0059]

[0060] In mathematical equation 8, , Δn j,i =n j,i -n c , Δk j,i =k j,i -k c And, represents the time-frequency correlation coefficient between the channel of the (n,k)th resource element and the channel of the (n+Δn,k+Δk)th resource element. In addition, n c Wow c Indicate the OFDM symbol position and subcarrier position of the resource element located at the center of the resource block, respectively. When the RS-based representative channel estimator determines the representative channel estimate value and estimates the channel, various estimation techniques can be utilized or applied in addition to the least squares technique to estimate the channel. After that, the RS-based representative channel estimator calculates a channel estimate value representing the entire resource block, and then the channel estimate values ​​of all resource elements within the resource block can be set to the same value as the representative channel estimate value. The method in which the receiver determines the representative channel estimate value through the RS-based representative channel estimator (215) and estimates the channel can accurately obtain the channel estimate value representing the resource block by simultaneously utilizing all DM-RSs available within the resource block.

[0061] A data symbol detector (220) can detect data symbols using a reference signal-based channel estimation value according to one of the first or second methods described above, for resource elements in which data symbols are transmitted. The resource elements in which data symbols are transmitted may refer to, for example, resource elements within a resource block in which a DM-RS is not transmitted.

[0062] According to one embodiment of the present disclosure, the data symbol detector (220) can detect a data symbol based on a channel estimate value derived from a channel estimator selected by the RS-based channel estimation selector (205). The data symbol detected by the data symbol detector (220) based on the channel estimate value derived from the RS-based channel estimator (210, 215) can be referred to as a first data symbol. The channel estimate value for the (n, k)th resource element derived from the reference signal-based channel estimator selected according to the decision of the reference signal-based channel estimation selector can be expressed as in [Mathematical Formula 9]. The channel estimate value expressed by <Mathematical Formula 9> can be, for example, a channel estimate value derived through the RS group-based channel estimator (210) or can also be a channel estimate value derived through the RS-based representative channel estimator (215).

[0063]

[0064] In mathematical expression 9, the data symbol detected by the data symbol detector (220) from the reception signal y[n,k] of the (n,k)th resource element by utilizing the channel estimation value of [mathematical expression 9] is can be expressed as . In the data symbol detection process, various conventional MIMO symbol detection or MIMO data detection techniques can be utilized. For example, when the maximum likelihood detection technique is utilized as a data symbol detection method, the detected data symbol ( for the (n, k)th resource element ) can be expressed as in [Mathematical Formula 10].

[0065]

[0066] In mathematical equation 10, represents a channel estimate value for the (n,k)th resource element. The channel estimate value may mean a channel estimate value determined by a reference signal-based channel estimator (e.g., 210 or 215) or a channel estimate value calculated by a data symbol-based channel estimator (e.g., 230).

[0067] For another example, when the linear least mean square error technique is used as a data symbol detection method, the detected data symbol for the (n,k)th resource element ( ) can be expressed as in [Mathematical Formula 11] below.

[0068]

[0069] In mathematical expression 11, is the identity matrix, represents the variance of each data symbol. If the elements of the detected data symbol are not represented by one of the elements of the symbol constellation, an additional process of corresponding them to the nearest element among the elements of the symbol constellation may be included.

[0070] According to one embodiment of the present disclosure, the data symbol detector (220) can re-detect the data symbol based on the channel estimate value derived from the data symbol by the DS-based channel estimator (230). The re-detected data symbol may be referred to as, for example, a second data symbol. When the DS-based channel estimation controller (225) determines to activate the DS-based channel estimator (230), the DS-based channel estimator (230) can derive a channel estimate value using the data symbol detected by the data symbol detector (220) based on the channel estimate value based on the DM-RS. At this time, the data symbol detector (220) can re-detect the data symbol based on the channel estimate value derived from the data symbol by the DS-based channel estimator (230).

[0071] The DS-based channel estimation controller (225) can determine whether to activate the DS-based channel estimator (230) using the data symbols detected by the data symbol detector (220). For example, the DS-based channel estimation controller (225) can determine an optimal sub-block size for the DS-based channel estimator (230) based on the data symbols, and determine whether to activate the DS-based channel estimator (230) based on the determined sub-block.

[0072] According to one embodiment of the present disclosure, a DS-based channel estimation controller (225) determines an optimal sub-block size by determining an optimal number of OFDM symbols that minimizes the MSE of a channel estimate value that a DS channel estimator (230) can derive. ) and the number of subcarriers ( ) can be used to determine the sub-block. For example, the DS-based channel estimation controller (225) can determine the sub-block through [Mathematical Formula 12].

[0073]

[0074] In mathematical expression 12, is the average value of the time-frequency correlations between the channel of the (n,k)th resource element and the channels of the resource elements within the sub-block to which the channel belongs. According to [Mathematical Formula 12], the optimal number of OFDM symbols ( ) and the number of subcarriers ( ), the MSE of the channel estimate value derived by the DS-based channel estimator (230) when the optimal sub-block size is used can be calculated.

[0075] The DS-based channel estimation controller (225) may compare the MSE of the channel estimation method of the DS-based channel estimator (230) with the MSE of the channel estimation method based on DM-RS to determine whether to activate the DS-based channel estimator (230). According to one embodiment of the present disclosure, if the MSE of the channel estimation method of the DS-based channel estimator (230) is lower than the MSE of the channel estimation method based on DM-RS, the DS-based channel estimation controller (225) may activate the DS-based channel estimator. In this case, since there is a high practical benefit of updating the channel estimation value based on DM-RS to the channel estimation value using the DS-based channel estimator (230), the DS-based channel estimation controller (225) may determine to activate the DS-based channel estimator. However, if the MSE of the channel estimation method of the DS-based channel estimator (230) is higher than the MSE of the channel estimation method based on DM-RS, the DS-based channel estimation controller (225) may deactivate the DS-based channel estimator (230). If the MSE of the channel estimation method of the DS-based channel estimator is higher than the MSE of the channel estimation method based on DM-RS, there is little practical benefit in updating the channel estimation value based on DM-RS to the channel estimation value using the DS-based channel estimator. Meanwhile, the MSE of the RS-based channel estimation method, which the DS-based channel estimation controller compares, may mean, for example, the MSE of the channel estimation method based on DM-RS selected by the RS-based channel selector. For example, the MSE of the RS-based channel estimation method may mean the MSE selected by the RS-based channel selector among the MSEs of [Mathematical Formula 4] or [Mathematical Formula 5].

[0076] When the DS-based channel estimation controller (225) determines to activate the DS-based channel estimator (230), the DS-based channel estimator (230) can update the channel estimation value calculated by the RS-based channel estimator (210 or 215). For example, the DS-based channel estimator (230) can divide a resource block into sub-blocks each consisting of P OFDM symbols and Q sub-carriers, and then utilize the detected symbols for the resource elements in each sub-block as virtual DM-RSs to determine a channel estimation value representing the channels of the resource elements in the corresponding sub-block. At this time, the size of the sub-block can be a value determined by the DS-based channel estimation controller (225) or can be a fixed value determined in advance.

[0077] According to one embodiment of the present disclosure, a method in which a DS-based channel estimator (230) determines a channel estimation value based on a data symbol detected by a data symbol detector (220) may have a difference in that, unlike a method in which a channel estimation value is derived based on an RS, in which each CDM group individually estimates only the channel formed in its own CDM group, the entire channel formed across all CDM groups is estimated at once. In the DS-based channel estimator (230), a data symbol-based channel estimation value that can represent the i-th sub-block can be defined as follows. For example, when a DS-based channel estimator (230) determines a data symbol-based channel estimation value using a least squares technique, the estimation value for the representative channel of the i-th sub-block can be expressed as in [Mathematical Formula 13] below.

[0078]

[0079] In mathematical expression 13, is a matrix whose rows contain the received signals observed in the resource elements within the i-th sub-block, is a matrix having rows of DM-RSs or detected data symbols transmitted in resource elements within the i-th sub-block, and α i is a correction constant. Meanwhile, as an example to reduce the complexity of calculating the channel estimation value, the DS-based channel estimator (230) may calculate the channel estimation value using the average received signal when there are multiple received signals with the same detected data symbol. As another example, when the average channel size of the resource elements in the i-th sub-block can be estimated through a separate process, the DS-based channel estimator (230) may calculate the correction constant (α i ) is the channel estimation value ( ) can be determined so that the size can be adjusted to match the estimated channel size value. However, if the average channel size of the resource elements within the i-th sub-block cannot be estimated, α i It is also possible to set it to =1.

[0080] After calculating the representative channel estimate value for each sub-block unit, the channel estimate values ​​of all resource elements within the sub-block may be set to the same value as the representative channel estimate value.

[0081] The updated channel estimate values ​​through the DS-based channel estimator (230) can be transmitted to the data symbol detector (220). The data symbol detector (220) can re-detect data symbols within the resource block based on the updated channel estimate values ​​received from the DS-based channel estimator (230). The data symbol detector (220) can transmit the re-detected data symbols to the channel decoder (235). At this time, the re-detected data symbols can be referred to as second data symbols.

[0082] The channel decoder (235) can recover information bits based on data symbols detected by the data symbol detector (220). According to one embodiment of the present disclosure, when the DS-based channel estimator (230) is deactivated, the channel decoder (235) can recover information bits based on initially detected data symbols or log-likelihood ratio (LLR) values ​​for the corresponding symbols using a channel estimation value based on RS. On the other hand, when the DS-based channel estimator (230) is activated, the channel decoder (235) can recover information bits based on redetected data symbols or LLR values ​​for the redetected symbols based on a channel estimation value based on data symbols.

[0083] According to one embodiment of the present disclosure, as one method for improving the channel estimation performance of a DS-based channel estimator (230), data symbols may be regenerated (e.g., 535 of FIG. 5) based on information bits determined by a channel decoder (235), and then data symbol-based channel estimation may be performed by utilizing the regenerated data symbols as virtual demodulation reference signals. In this case, the regenerated data symbols may be referred to as third data symbols.

[0084] FIG. 3 illustrates an operation (300) for estimating a channel by a receiver according to one embodiment of the present disclosure. Specifically, FIG. 3 illustrates an operation for estimating a channel based on detected data symbols. It is assumed that the channel estimate value derived based on the RS described in FIG. 3 is a channel estimate value derived through an RS-based representative channel estimator (e.g., 215 of FIG. 2 ).

[0085] Referring to FIG. 3, the receiver can determine a data symbol based on a representative channel estimate value that considers all DM-RSs within a resource block using a data symbol detector (e.g., 220 of FIG. 2). The representative channel estimate value that considers all DM-RSs within a resource block may be a channel estimate value derived through an RS-based representative channel estimator (e.g., 215 of FIG. 2). The channel estimate value derived by the RS-based representative channel estimator may be, for example, a representative channel estimate value calculated in [Mathematical Formula 6]. If the RS-based representative channel estimator can know the time-frequency correlation information of the channel, the channel estimation value is the representative channel estimation value calculated in [Mathematical Formula 7]. It can be. The data symbol detector can detect data symbols using a reference signal-based channel estimation value for resource elements in which data symbols are transmitted. The resource elements in which data symbols are transmitted may refer to, for example, resource elements within a resource block in which a DM-RS is not transmitted.

[0086] According to one embodiment of the present disclosure, various conventional MIMO symbol detection or MIMO data detection techniques may be utilized in the data symbol detection process. For example, when the maximum likelihood detection technique is utilized as a data symbol detection method, the detected data symbol ( for the (n, k)th resource element) ) can be expressed as [Mathematical Formula 10] described in Fig. 2. For another example, when the linear least mean square error technique is used as a data symbol detection method, the data symbol ( detected for the (n, k)th resource element ) can be expressed as in [Mathematical Formula 11] described in Fig. 2.

[0087] A DS-based channel estimation controller (e.g., 225 in FIG. 2) can determine whether to activate a DS-based channel estimator (e.g., 230 in FIG. 2) using data symbols detected by a data symbol detector. For example, the DS-based channel estimation controller can determine an optimal sub-block size for the DS-based channel estimator based on data symbols, and determine whether to activate the DS-based channel estimator based on the determined sub-block. According to one embodiment of the present disclosure, as a method for the DS-based channel estimation controller to determine an optimal sub-block size, an optimal number of OFDM symbols ( according to [Mathematical Formula 12] described in FIG. 2) ) and the number of subcarriers ( ), there may be a way to calculate the MSE of the channel estimate derived by the DS-based channel estimator when the optimal sub-block size is used.

[0088] The DS-based channel estimation controller may compare the MSE of the channel estimation method of the DS-based channel estimator with the MSE of the channel estimation method based on the DM-RS to determine whether to activate the DS-based channel estimator. According to one embodiment of the present disclosure, if the MSE of the channel estimation method of the DS-based channel estimator is lower than the MSE of the channel estimation method based on the DM-RS, the DS-based channel estimation controller may activate the DS-based channel estimator. In this case, since there is a high practical benefit of updating the channel estimation value based on the DM-RS to the channel estimation value using the DS-based channel estimator, the DS-based channel estimation controller may determine to activate the DS-based channel estimator. However, if the MSE of the channel estimation method of the DS-based channel estimator is higher than the MSE of the channel estimation method based on the DM-RS, the DS-based channel estimation controller may deactivate the DS-based channel estimator. If the MSE of the channel estimation method of the DS-based channel estimator is higher than the MSE of the channel estimation method of the DM-RS-based channel estimator, there is little practical benefit in updating the channel estimation value based on the DM-RS to the channel estimation value using the DS-based channel estimator. Meanwhile, the MSE of the RS-based channel estimation method, which the DS-based channel estimation controller compares with, may refer to, for example, the MSE of the channel estimation method based on the DM-RS selected by the RS-based channel selector. For example, the MSE of the RS-based channel estimation method may refer to the MSE selected by the RS-based channel selector among the MSEs of [Mathematical Formula 4] or [Mathematical Formula 5].

[0089] When the DS-based channel estimation controller determines to activate the DS-based channel estimator, the DS-based channel estimator can update the channel estimation value calculated by the RS-based channel estimator. For example, the DS-based channel estimator can divide a resource block into sub-blocks each consisting of P OFDM symbols and Q sub-carriers, and then use the detected symbols for resource elements in each sub-block as virtual DM-RSs to determine a channel estimation value representing the channels of the resource elements in the corresponding sub-block. At this time, the P and Q values ​​for determining the size of the sub-block may be values ​​determined by the DS-based channel estimation controller or may be fixed values ​​determined in advance.

[0090] According to one embodiment of the present disclosure, in a DS-based channel estimator, a data symbol-based channel estimation value representing the i-th sub-block is can be defined as follows. For example, if a DS-based channel estimator determines a data symbol-based channel estimate value using a least squares technique, the estimate value for the representative channel of the i-th sub-block can be expressed as in <Mathematical Formula 13> described in Fig. 2.

[0091] Meanwhile, as an example of how a DS-based channel estimator can reduce the complexity of calculating a channel estimate value, if there are multiple received signals with the same detected data symbol, the channel estimate value can be calculated using the average received signal. As another example, if the average channel size of resource elements within the i-th sub-block can be estimated through a separate process, the DS-based channel estimator can calculate a correction constant (α i ) as the channel estimation value ( ) can be determined so that the size of the resource elements can be adjusted to the estimated channel size value. However, if the average channel size of the resource elements within the i-th sub-block cannot be estimated, α i It is also possible to set it to =1.

[0092] After calculating the representative channel estimate value for each sub-block unit, the channel estimate values ​​of all resource elements within the sub-block may be set to the same value as the representative channel estimate value.

[0093] According to one embodiment of the present disclosure, when a DS-based channel estimator utilizes a representative channel estimate value for each sub-block, a smoothing filter may be used to determine a channel estimate value at the boundary of the sub-blocks to prevent degradation of the performance of the channel estimate value. When a smoothing filter is applied to the channel estimate values ​​within the entire resource block, the channel estimate value of each resource element may be replaced with a weighted average value of the channel estimate values ​​of each resource element and the channel estimate values ​​of adjacent elements. A Gaussian filter may be used as a representative example of the smoothing filter, and one of various smoothing filters may also be used.

[0094] FIG. 4 illustrates an operation (400) of a receiver estimating a channel according to one embodiment of the present disclosure.

[0095] Referring to FIG. 4, at step 405, the receiver may select one of the RS group-based channel estimation method and the RS-based representative channel estimation method for RS-based channel estimation. For example, the receiver may select a suitable channel estimator among the RS group-based channel estimator (e.g., 210 of FIG. 2) or the RS-based representative channel estimator (e.g., 215 of FIG. 2) through an RS-based channel estimation selector (e.g., 205 of FIG. 2). According to one embodiment of the present disclosure, in order to select a suitable channel estimator for RS-based channel estimation, the receiver may select a channel estimator that minimizes the MSE of a channel estimation value among a channel estimation value through the RS group-based channel estimator or a channel estimation value through the RS-based representative channel estimator.

[0096] At step 410, the receiver can determine whether to determine a representative channel estimate value that can represent the channels of resource elements within a resource block. That is, the receiver can determine whether an RS-based channel estimation selector within the receiver has selected an RS-based representative channel estimator as an estimator for deriving a channel estimate value based on DM-RS. If the RS-based channel estimation selector has selected the RS-based representative channel estimator as an estimator for deriving a channel estimate value based on DM-RS, step 415 may be performed. However, if the RS-based channel estimation selector has selected an RS group-based channel estimator as an estimator for deriving a channel estimate value based on DM-RS, step 420 may be performed.

[0097] At step 415, the receiver can determine a representative channel estimate value that can represent the channels of resource elements within a resource block using an RS-based representative channel estimator.

[0098] At step 420, the receiver can use an RS group-based channel estimator to determine channel estimate values ​​for resource elements within a resource block. For example, the receiver can use an RS group-based estimator to divide the received DM-RSs into CDM groups, derive group-specific channel estimate values, and then determine channel estimate values ​​for resource elements within each group. However, the method by which the RS group-based channel estimator derives channel estimate values ​​is not limited to this, and various embodiments described above can be applied.

[0099] At step 425, the receiver can determine data symbols for the corresponding resource block. Specifically, the receiver can determine data symbols through a data symbol detector (e.g., 220 of FIG. 2 ). For example, the receiver can determine data symbols based on a channel estimate value estimated based on the DM-RS and the received signals. At this time, the data symbol determined by the receiver can be referred to as a first data symbol.

[0100] At step 430, the receiver can determine an optimal sub-block size for the DS-based channel estimator through a DS-based channel estimation controller within the receiver (e.g., 225 in FIG. 2), and can determine whether to activate the DS-based channel estimator. Whether to activate the DS-based channel estimator can be determined by comparing the MSE of the channel estimation method of the DS-based channel estimator with the MSE of the channel estimation method based on DM-RS. For example, if the MSE of the channel estimation method of the DS-based channel estimator is lower than the MSE of the channel estimation method based on DM-RS, the DS-based channel estimation controller can activate the DS-based channel estimator. However, if the MSE of the channel estimation method of the DS-based channel estimator is higher than the MSE of the channel estimation method based on DM-RS, the DS-based channel estimation controller can deactivate the DS-based channel estimator.

[0101] At step 435, the receiver may determine whether to enable the DS-based channel estimation method. For example, the receiver may determine whether to enable the DS-based channel estimator. If the DS-based channel estimation controller within the receiver determines to enable the DS-based channel estimator, step 440 may be performed. However, if the DS-based channel estimation controller within the receiver determines to disable the DS-based channel estimator, and thus the DS-based channel estimator is not enabled, step 450 may be performed.

[0102] In step 440, the receiver can determine a channel estimate value based on the data symbols detected in step 425 using a DS-based channel estimator within the receiver. If a DS-based channel estimation controller included in the receiver (e.g., 225 of FIG. 2) determines to activate the DS-based channel estimator (e.g., 230 of FIG. 2), the receiver can update the channel estimate value calculated by the RS-based channel estimator using the DS-based channel estimator. For example, the receiver divides a resource block into sub-blocks consisting of P OFDM symbols and Q subcarriers.

[0103] After dividing into units, the detected symbols for resource elements within each sub-block can be used as virtual DM-RSs to determine channel estimation values ​​representing the channels of the resource elements within the corresponding sub-block. At this time, the channel estimation value calculated by the RS-based channel estimator may refer to a channel estimation value based on the DM-RS determined in step 415 or 420. In addition, the size of the sub-block may be a value determined by the DS-based channel estimation controller or may be a value determined in advance.

[0104] According to one embodiment of the present disclosure, a method for determining a channel estimation value based on a detected data symbol by a receiver is provided in which, when a data symbol-based channel estimation value is determined using a least squares technique, an estimation value for a representative channel of an i-th sub-block can be expressed as in the above-described <Mathematical Formula 13>.

[0105] According to one embodiment of the present disclosure, the channel estimate value based on the DM-RS determined in step 415 or step 420 can be updated with a channel estimate value based on the data symbol determined using a DS-based channel estimator.

[0106] In step 445, the receiver can redetermine data symbols based on a channel estimate value based on the data symbols determined in step 440. For example, a data symbol detector in the receiver can update a channel estimate value derived from an RS-based channel estimator to a channel estimate value derived from a DS-based channel estimator, and re-detect data symbols based on the updated channel estimate value. At this time, the data symbols re-detected by the receiver may be referred to as, for example, second data symbols. Meanwhile, if the DS-based channel estimator is not activated, the DS-based channel estimator does not perform channel estimation, and therefore, the data symbol detector may not re-detect data symbols.

[0107] At step 450, the receiver can perform channel decoding on data symbols of a resource block based on the detected data symbols or LLR values ​​for the data symbols using a channel decoder (e.g., 235 of FIG. 2). The receiver can recover information bits by performing channel decoding. The detected data symbols may refer to data symbols that the data symbol detector re-detected based on a channel estimate value derived through the DS-based channel estimator, for example, when the DS-based channel estimator is activated. Furthermore, the detected data symbols may refer to data symbols that the data symbol detector detected based on a channel estimate value derived through the RS-based channel estimator, when the DS-based channel estimator is deactivated. According to one embodiment of the present disclosure, when the DS-based channel estimator is deactivated, the receiver can perform channel decoding on the detected data symbols using a channel estimate value determined based on the DM-RS at step 425.

[0108] FIG. 5 illustrates an operation (500) of a receiver estimating a channel according to one embodiment of the present disclosure. Steps 505 to 525 of FIG. 5 may correspond to steps 405 to 425 of FIG. 4.

[0109] Referring to FIG. 5, in step 505, the receiver may select one of the RS group-based channel estimation method and the RS-based representative channel estimation method for RS-based channel estimation. For example, the receiver may select a suitable channel estimator among the RS group-based channel estimator (e.g., 210 of FIG. 2) or the RS-based representative channel estimator (e.g., 215 of FIG. 2) through an RS-based channel estimation selector (e.g., 205 of FIG. 2). According to one embodiment of the present disclosure, in order to select a suitable channel estimator for RS-based channel estimation, the receiver may select a channel estimator that minimizes the MSE of a channel estimation value among a channel estimation value through the RS group-based channel estimator or a channel estimation value through the RS-based representative channel estimator.

[0110] In step 510, the receiver can determine whether to determine a representative channel estimate value that can represent the channels of resource elements within a resource block. That is, the receiver can determine whether an RS-based channel estimation selector within the receiver has selected an RS-based representative channel estimator as an estimator for deriving a channel estimate value based on DM-RS. If the RS-based channel estimation selector has selected the RS-based representative channel estimator as an estimator for deriving a channel estimate value based on DM-RS, step 515 may be performed. However, if the RS-based channel estimation selector has selected an RS group-based channel estimator as an estimator for deriving a channel estimate value based on DM-RS, step 520 may be performed.

[0111] At step 515, the receiver can determine a representative channel estimate value that can represent the channels of resource elements within a resource block using an RS-based representative channel estimator.

[0112] At step 520, the receiver can use an RS group-based channel estimator to determine channel estimate values ​​for resource elements within a resource block. For example, the receiver can use an RS group-based estimator to divide the received DM-RSs into CDM groups, derive group-specific channel estimate values, and then determine channel estimate values ​​for resource elements within each group. However, the method by which the RS group-based channel estimator derives channel estimate values ​​is not limited to this, and various embodiments described above can be applied.

[0113] At step 525, the receiver can determine data symbols for the corresponding resource block. Specifically, the data symbols can be determined through a receiver data symbol detector (e.g., 220 of FIG. 2 ). For example, the receiver can detect data symbols based on a channel estimate value estimated based on the DM-RS and the received signals. At this time, the data symbol determined by the receiver can be referred to as a first data symbol.

[0114] In step 530, the receiver may perform channel decoding based on the detected data symbols or LLR values ​​for the detected data symbols using a data symbol detector. The receiver may perform channel decoding to recover information bits. The detected data symbols may refer to data symbols detected by the data symbol detector based on a channel estimate value derived through RS-based channel extraction, for example.

[0115] In step 535, the receiver can regenerate data symbols based on the information bits recovered by performing channel decoding in step 530. The regenerated data symbols can be used in a DS-based channel estimation controller and a DS-based channel estimator. The operations of channel decoding and regenerating data symbols in the receiver in steps 530 and 535 can be optionally performed and may be omitted. Meanwhile, the regenerated data symbols can be referred to as third data symbols.

[0116] In step 540, the receiver can determine an optimal sub-block size for the DS-based channel estimator through a DS-based channel estimation controller within the receiver (e.g., 225 in FIG. 2), and can determine whether to activate the DS-based channel estimator. Whether to activate the DS-based channel estimator can be determined by comparing the MSE of the channel estimation method of the DS-based channel estimator with the MSE of the channel estimation method based on DM-RS. In this case, the MSE of the channel estimation value derived through the DS-based channel estimator can be a value calculated based on the data symbols regenerated in step 535.

[0117] According to one embodiment of the present disclosure, if the MSE of the channel estimation method of the DS-based channel estimator is lower than the MSE of the channel estimation method of the DM-RS-based channel estimation method, the DS-based channel estimation controller may activate the DS-based channel estimator. However, if the MSE of the channel estimation method of the DS-based channel estimator is higher than the MSE of the channel estimation method of the DM-RS-based channel estimation method, the DS-based channel estimation controller may deactivate the DS-based channel estimator.

[0118] At step 545, the receiver may determine whether to enable the DS-based channel estimation method. For example, the receiver may determine whether to enable the DS-based channel estimator. If the DS-based channel estimation controller within the receiver determines to enable the DS-based channel estimator, step 550 may be performed. However, if the DS-based channel estimation controller within the receiver determines to disable the DS-based channel estimator, and thus the DS-based channel estimator is not enabled, step 560 may be performed.

[0119] In step 550, the receiver can determine a channel estimate value based on the data symbols regenerated in step 535 using a DS-based channel estimator within the receiver. If a DS-based channel estimation controller (e.g., 225 of FIG. 2) included in the receiver determines to activate the DS-based channel estimator (e.g., 230 of FIG. 2), the receiver can update the channel estimate value calculated by the RS-based channel estimator using the DS-based channel estimator. For example, the receiver can divide a resource block into sub-blocks each consisting of P OFDM symbols and Q sub-carriers, and then use the detected symbols for resource elements within each sub-block as virtual DM-RSs to determine a channel estimate value representing the channels of the resource elements within the corresponding sub-block. In this case, the channel estimate value calculated by the RS-based channel estimator may mean a channel estimate value based on the DM-RS determined in step 515 or 520. Additionally, the size of a sub-block may be a value determined by a DS-based channel estimation controller, or may be a predetermined fixed value.

[0120] In step 555, the receiver can redetermine data symbols based on a channel estimate value based on the data symbols determined in step 550. For example, a data symbol detector in the receiver can update a channel estimate value derived from an RS-based channel estimator to a channel estimate value derived from a DS-based channel estimator, and re-detect data symbols based on the updated channel estimate value. At this time, the data symbols re-detected by the receiver may be referred to as, for example, second data symbols. Meanwhile, if the DS-based channel estimator is not activated, the DS-based channel estimator does not perform channel estimation, and thus the data symbol detector may not re-detect data symbols.

[0121] At step 560, the receiver may perform channel decoding on data symbols of a resource block based on the detected data symbols or LLR values ​​for the data symbols using a channel decoder. The receiver may recover information bits by performing channel decoding. The detected data symbols may refer to data symbols that are re-detected by a data symbol detector based on a channel estimate value derived through a DS-based channel estimator, for example, when a DS-based channel estimator is enabled. Furthermore, the detected data symbols may refer to data symbols that are detected by a data symbol detector based on a channel estimate value derived through an RS-based channel estimator, when the DS-based channel estimator is disabled. According to one embodiment of the present disclosure, when the DS-based channel estimator is disabled, the receiver may perform channel decoding on the detected data symbols using a channel estimate value determined based on a DM-RS at step 525.

[0122] FIG. 6 illustrates an operation (600) of a receiver estimating a channel according to one embodiment of the present disclosure.

[0123] Referring to FIG. 6, at step 610, the receiver may determine a first channel estimate value based on a demodulation reference signal within a resource block. According to one embodiment of the present disclosure, the first channel estimate value may refer to a channel estimate value that exhibits the lowest mean square error (MSE) among channel estimate values ​​based on DM-RSs within a plurality of resource blocks, as determined by an RS-based channel selector included in the receiver. For example, the first channel estimate value may refer to a representative channel estimate value determined based on all DM-RSs within the resource block. Specifically, the first channel estimate value may correspond to a channel estimate value derived by the receiver using an RS-based representative channel estimator (215 of FIG. 2). In addition, the first channel estimate value may be determined based on time and frequency correlation information of a channel of a resource element to which a DM-RS is applied within the resource block. In this case, the resource block may refer to a resource in a MIMO-OFDM network to which code division multiplexing is applied.

[0124] In step 620, the receiver may determine a first data symbol of a resource block based on the first channel estimate value determined in step 610. At this time, the first data symbol may be transmitted through resource elements within the resource block on which a DM-RS is not transmitted.

[0125] According to one embodiment of the present disclosure, after detecting a first data symbol, the receiver may perform channel decoding based on the additionally detected data symbol and regenerate the data symbol based on the result of the channel decoding. The regenerated data symbol may be used when the receiver determines whether to derive a channel estimate value based on the DM-RS.

[0126] In step 630, the receiver may determine whether to determine a second channel estimate value based on the detected data symbols. The second channel estimate value may refer to a channel estimate value derived based on the data symbols. For example, the second channel estimate value may refer to a value obtained by estimating a channel using the detected data symbols by a DS-based channel estimator included in the receiver of FIG. 2. According to one embodiment of the present disclosure, the receiver may determine whether to update the first channel estimate value determined based on the detected data symbols in step 620 to a second channel estimate value.

[0127] If the receiver determines not to determine the second channel estimate, the receiver may decode the data symbols of the resource block based on the data symbols detected based on the first channel estimate. On the other hand, if the receiver determines to determine the second channel estimate, the receiver may determine the second channel estimate according to the following operations.

[0128] According to one embodiment of the present disclosure, the operation of determining whether the receiver determines a second channel estimate value based on the detected data symbol may correspond to the operation of the DS-based channel estimation controller included in the receiver in FIG. 2 in which the DS-based channel estimation controller determines whether to activate the DS-based channel estimator. For example, the operation of determining whether the receiver determines a second channel estimate value may compare a mean square error MSE of the first channel estimate value with the MSE of the second channel estimate value, and if the MSE of the second channel estimate value is lower than the MSE of the first channel estimate value, the receiver may determine to determine the second channel estimate value.

[0129] According to one embodiment of the present disclosure, if the receiver determines to determine the second channel estimate value, the receiver may determine sub-blocks into which a resource block is to be divided, divide the resource block according to the size of the determined sub-block, and determine the second channel estimate value based on data symbols included in resource elements within the sub-block. Meanwhile, the size of the sub-block may be determined by using a predetermined size of the sub-block, or by calculating a size of the sub-block that minimizes the MSE of the second channel estimate value. On the other hand, if the receiver determines not to determine the second channel estimate value, the receiver may omit the operation of determining the sub-block and the second channel estimate value, and perform channel decoding based on the data symbols detected in step 620.

[0130] At step 640, if the receiver determines to determine a second channel estimate value, the receiver may re-detect data symbols based on the second channel estimate value. For example, if a DS-based channel estimator included in the receiver determines a channel estimate value based on the detected data symbols, the data symbol detector included in the receiver may re-detect data symbols based on the estimated value of the DS-based channel estimator. In this case, the re-detected data symbols may be referred to as second data symbols.

[0131] At step 650, the receiver can perform channel decoding based on the re-detected data symbols using the second channel estimate value from step 640. For example, a channel decoder within the receiver can recover and obtain information bits for the corresponding resource block based on the re-detected data symbols.

[0132] FIG. 7 illustrates a signal-to-noise ratio (SNR) versus frame error rate (FER) according to an embodiment of the present disclosure. FIG. 7 assumes a situation in which there are two transmit antenna ports and four antenna ports. In addition, FIG. 7 assumes a 4-quadrature amplitude modulation (QAM) situation in which there is a resource block consisting of 12 subcarriers and 14 OFDM symbols and one CDM group, and six DM-RSs are transmitted in each of the 3rd and 12th OFDM symbols within the resource block. In this case, it is assumed that channel estimation based on DM-RS and data symbols uses the least-squares technique, and data symbol detection uses the linear least mean square error method. In addition, it is assumed that the channel changes over time as shown in [Mathematical Equation 14] below.

[0133]

[0134] In mathematical expression 14, represents the time-domain correlation coefficient with the previous channel, and Z[n,k] represents a complex Gaussian random matrix with the same variance as the channel. In Fig. 7. =0.9924. If the carrier frequency is 3.5 GHz and the OFDM symbol period is 71.35 μs, the time-domain correlation coefficient with the previous channel represents the case where the receiver's speed is 120 km / h.

[0135] The conventional channel estimation simulation result (710) of Fig. 7 shows the result of plotting the frame error rate against the signal-to-noise ratio when using the conventional method of estimating the channel using DM-RS. The conventional method of estimating the channel using DM-RS may refer to a method of dividing DM-RS into CDM groups and deriving a channel estimation value for each CDM group to estimate the channel. For example, it may refer to a method of deriving a channel estimation value using the RS group-based channel estimator (210 of Fig. 2) of Fig. 2. However, the conventional channel estimation simulation result (710) may be a channel estimation simulation result that only considers the method of estimating the channel using DM-RS, without considering the method of estimating the channel based on data symbols.

[0136] The proposed channel estimation simulation result (720) shows the simulation result in the case where a channel estimation value is derived based on DM-RS, data is detected based on the derived channel estimation value, and a channel is estimated based on the detected data symbols. For example, the proposed channel estimation simulation result (720) may be the simulation result in which a channel is estimated by deriving a channel estimation value representing all DM-RSs using the RS-based representative channel estimator of FIG. 2, detecting a data symbol based on the derived channel estimation value, and re-detecting the data symbol by deriving a channel estimation value based on the detected data symbol. The perfect channel information simulation result (730) shows the result in which the frame error rate in the case where it is almost the same as the actual channel information is described as a signal-to-noise ratio.

[0137] Referring to Fig. 7, the proposed channel estimation simulation result (720) shows an aspect closer to a perfect channel information simulation result (730) than the conventional channel estimation simulation result (710). In other words, the proposed channel estimation simulation result (720) can indicate that a lower frame error rate can be achieved than the conventional channel estimation simulation result (710) in an environment where the channel changes over time.

[0138] FIG. 8 illustrates a frame error rate versus signal-to-noise ratio according to an embodiment of the present disclosure. FIG. 8 assumes a situation in which there are two transmit antenna ports, four antenna ports, a resource block consisting of 12 subcarriers and 14 OFDM symbols, and one CDM group, and a 4-QAM situation. However, FIG. 8 assumes that six DM-RSs are transmitted only in the third OFDM symbol within the resource block, and does not assume a situation in which DM-RSs are transmitted in the 12th OFDM symbol as in FIG. 7. It is assumed that channel estimation based on DM-RS and data symbols uses the least squares technique, and data symbol detection uses the linear least mean square error method. In addition, it is assumed that the channel changes over time as in [Equation 14] described in FIG. 8 in [Equation 14] =0.9924. If the carrier frequency is 3.5 GHz and the OFDM symbol period is 71.35 μs, the time-domain correlation coefficient with the previous channel represents the case where the receiver's speed is 120 km / h.

[0139] The conventional channel estimation simulation result (810) of Fig. 8 shows the result of plotting the frame error rate in relation to the signal-to-noise ratio when using the conventional method of estimating the channel using DM-RS. The conventional method of estimating the channel using DM-RS may refer to a method of dividing DM-RS into CDM groups and deriving a channel estimation value for each CDM group to estimate the channel. For example, it may refer to a method of deriving a channel estimation value using the RS group-based channel estimator of Fig. 2 (e.g., 210 of Fig. 2). However, the conventional channel estimation simulation result (710) may be a channel estimation simulation result that only considers the method of estimating the channel using DM-RS, without considering the method of estimating the channel based on data symbols.

[0140] The proposed channel estimation simulation result (820) illustrates the simulation result of deriving a channel estimation value based on DM-RS, detecting data based on the derived channel estimation value, and estimating a channel based on the detected data symbols. For example, the proposed channel estimation simulation result (820) may be the simulation result of estimating a channel by deriving a channel estimation value representing all DM-RSs using the RS-based representative channel estimator of FIG. 2, detecting data symbols based on the derived channel estimation value, and re-detecting the data symbols by deriving a channel estimation value based on the detected data symbols. The perfect channel information simulation result (830) illustrates the result of describing the frame error rate in the case where it is almost the same as the actual channel information as a signal-to-noise ratio.

[0141] Referring to Fig. 8, the proposed channel estimation simulation result (820) shows an aspect closer to a perfect channel information simulation result (830) than the conventional channel estimation simulation result (810). That is, the proposed channel estimation simulation result (820) can indicate that a lower frame error rate can be achieved than the conventional channel estimation simulation result (810) in an environment where the channel changes over time.

[0142] Accordingly, it can be seen that when the channel of the received signal is estimated by determining a representative channel estimate value by considering all DM-RSs according to the proposed channel estimation method, detecting data symbols using the representative channel estimate value, and determining a channel estimate value based on the detected data symbols, it can be seen that the channel estimate can be closer to actual channel information than the method of simply estimating the channel based on the channel estimate value derived by considering DM-RSs by CDM group of DM-RSs.

[0143] Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples presented to easily explain the technical content of the present invention and facilitate understanding of the present invention, and are not intended to limit the scope of the present invention. In other words, it will be apparent to those skilled in the art that other modifications based on the technical concept of the present invention are possible. Furthermore, the above-described embodiments can be combined and operated as needed.

[0144] As described above, a method performed by a receiver in a wireless communication system according to various embodiments disclosed in the present document may include an operation of determining a first channel estimate value based on a demodulation reference signal (DM-RS) symbol within a resource block, an operation of detecting a first data symbol based on the first channel estimate value, an operation of determining whether to determine a second channel estimate value based on the first data symbol, an operation of detecting a second data symbol based on the second channel estimate value when it is determined to determine the second channel estimate value, and an operation of performing channel decoding on the second data symbol.

[0145] According to various embodiments disclosed in this document, the first channel estimate value may mean a representative channel estimate value determined based on all DM-RS symbols within a resource block.

[0146] According to various embodiments disclosed in the present document, the operation of determining the first channel estimate value may further include the operation of determining, as the first channel estimate value, a channel estimate value having a lowest mean squared error (MSE) among channel estimate values ​​based on a plurality of DM-RS symbols within a resource block.

[0147] According to various embodiments disclosed in the present document, the operation of determining whether to determine a second channel estimation value may further include the operation of comparing a mean squared error (MSE) of the first channel estimation value with an MSE of the second channel estimation value, and determining to determine the second channel estimation value if the MSE of the second channel estimation value is lower than the MSE of the first channel estimation value.

[0148] According to various embodiments disclosed in the present document, the method may further include, when it is determined to determine a second channel estimate value, an operation of determining a size of a sub-block for a resource block, an operation of dividing the resource block into a plurality of sub-blocks according to the sizes of the sub-blocks, and an operation of determining channel estimate values ​​based on data symbols included in the resource element as the second channel estimate value for the plurality of sub-blocks.

[0149] According to various embodiments disclosed in this document, the size of the sub-block may be determined by using a predetermined size of the sub-block, or by calculating a size of the sub-block that minimizes the MSE of the second channel estimate value.

[0150] According to various embodiments disclosed in this document, the method may include performing channel decoding on the first data symbol when it is determined not to determine a second channel estimate value.

[0151] According to various embodiments disclosed in the present document, the method further includes an operation of performing channel decoding on a first data symbol, an operation of regenerating a third data symbol based on a result of the channel decoding on the first data symbol, wherein the third data symbol may be used to determine whether to determine a second channel estimate value.

[0152] According to various embodiments disclosed in this document, the first channel estimate value may be determined based on time and frequency correlation information of a channel of a resource element in which a DM-RS symbol within a resource block is received.

[0153] According to various embodiments disclosed in this document, a resource block may include a decoding unit of a wireless resource for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) with code division multiplexing (CDM).

[0154] As described above, in a wireless communication system according to various embodiments disclosed in the present document, a receiver may include at least one processor, and the at least one processor may be configured to determine a first channel estimation value based on a demodulation reference signal (DM-RS) symbol within a resource block, detect a first data symbol based on the first channel estimation value, determine whether to determine a second channel estimation value based on the first data symbol, detect a second data symbol based on the second channel estimation value when it is determined to determine the second channel estimation value, and perform channel decoding on the second data symbol.

[0155] According to various embodiments disclosed in this document, the first channel estimate value may mean a representative channel estimate value determined based on all DM-RS symbols within a resource block.

[0156] According to various embodiments disclosed in the present document, at least one processor may be configured to determine, as a first channel estimate value, a channel estimate value having a lowest mean squared error (MSE) among channel estimate values ​​based on a plurality of DM-RS symbols within the resource block.

[0157] According to various embodiments disclosed in the present document, at least one processor may be configured to compare a mean squared error (MSE) of a first channel estimate value with an MSE of a second channel estimate value, and determine to determine the second channel estimate value if the MSE of the second channel estimate value is lower than the MSE of the first channel estimate value.

[0158] According to various embodiments disclosed in the present document, at least one processor may be configured to determine a size of a sub-block for a resource block, divide the resource block into a plurality of sub-blocks according to the sizes of the sub-blocks, and determine channel estimation values ​​based on data symbols included in the resource elements for the plurality of sub-blocks as second channel estimation values.

[0159] According to various embodiments disclosed in this document, the size of the sub-block may be determined by using a predetermined size of the sub-block, or by calculating a size of the sub-block that minimizes the MSE of the second channel estimate value.

[0160] According to various embodiments disclosed in this document, at least one processor may be configured to perform channel decoding on the first data symbol if it is determined not to determine a second channel estimate value.

[0161] According to various embodiments disclosed in the present document, at least one processor may be configured to perform channel decoding on a first data symbol and to regenerate a third data symbol based on a result of the channel decoding on the first data symbol, wherein the third data symbol may be used to determine whether to determine a second channel estimate value.

[0162] According to various embodiments disclosed in this document, the first channel estimate value may be determined based on time and frequency correlation information of a channel of a resource element in which a DM-RS symbol within a resource block is received.

[0163] According to various embodiments disclosed in this document, a resource block may include a decoding unit of a wireless resource for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) with code division multiplexing (CDM).

Claims

1. A method performed by a receiver in a wireless communication system, An operation of determining a first channel estimate value based on a demodulation reference signal (DM-RS) symbol within a resource block; An operation of detecting a first data symbol based on the first channel estimate value; An operation for determining whether to determine a second channel estimate value based on the first data symbol; If it is determined to determine the second channel estimate value, an operation of detecting a second data symbol based on the second channel estimate value; and A method comprising an operation of performing channel decoding on the second data symbol.

2. In claim 1, A method wherein the first channel estimate value means a representative channel estimate value determined based on all DM-RS symbols within the resource block.

3. In claim 1, the operation of determining the first channel estimate value comprises: A method further comprising an operation of determining a channel estimate value having a lowest mean squared error (MSE) among channel estimate values ​​based on a plurality of DM-RS symbols within the resource block as the first channel estimate value.

4. In claim 1, the operation of determining whether to determine the second channel estimate value comprises: An operation of comparing the mean squared error (MSE) of the first channel estimate value with the MSE of the second channel estimate value; and A method further comprising an operation of determining the second channel estimate value when the MSE of the second channel estimate value is lower than the MSE of the first channel estimate value.

5. In claim 4, if it is determined to determine the second channel estimate value, the method, An action for determining the size of a sub-block for the above resource block; An operation of dividing the above resource block into a plurality of sub-blocks according to the size of the sub-blocks; and A method further comprising, for the plurality of sub-blocks, an operation of determining channel estimation values ​​based on data symbols included in the resource elements as the second channel estimation values.

6. In claim 1, the method comprises: An operation of performing channel decoding on the first data symbol; and Further comprising an operation of regenerating a third data symbol based on the result of channel decoding for the first data symbol, A method wherein the third data symbol is used to determine whether to determine the second channel estimate value.

7. In a receiver in a wireless communication system, comprising at least one processor, At least one processor of the above, Determine the first channel estimate value based on the demodulation reference signal (DM-RS) symbol within the resource block, Detecting a first data symbol based on the first channel estimate value, Determine whether to determine a second channel estimate value based on the first data symbol, If it is determined to determine the second channel estimate value, a second data symbol is detected based on the second channel estimate value, A receiver configured to perform channel decoding on the second data symbol.

8. In claim 7, A receiver, wherein the first channel estimate value means a representative channel estimate value determined based on all DM-RS symbols within the resource block.

9. In claim 7, At least one processor of the above, A receiver configured to determine a channel estimate value having a lowest mean squared error (MSE) among channel estimate values ​​based on a plurality of DM-RS symbols within the resource block as the first channel estimate value.

10. In claim 7, At least one processor of the above, Compare the mean squared error (MSE) of the first channel estimate value with the MSE of the second channel estimate value, A receiver configured to determine the second channel estimate value when the MSE of the second channel estimate value is lower than the MSE of the first channel estimate value.

11. In claim 10, At least one processor of the above, Determine the size of a sub-block for the above resource block, The above resource block is divided into multiple sub-blocks according to the size of the sub-block, A receiver configured to determine channel estimation values ​​based on data symbols included in resource elements for the plurality of sub-blocks as the second channel estimation values.

12. In claim 11, the size of the sub-block is: A pre-determined sub-block size is used, or A receiver, wherein the size of a sub-block that minimizes the MSE of the second channel estimate value is calculated and determined.

13. In claim 7, At least one processor of the above, A receiver configured to perform channel decoding on the first data symbol if it is determined not to determine the second channel estimate value.

14. In claim 7, At least one processor of the above, Perform channel decoding on the first data symbol, It is set to regenerate a third data symbol based on the result of channel decoding for the first data symbol, A receiver wherein the third data symbol is used to determine whether to determine the second channel estimate value.

15. In claim 7, A receiver, wherein the first channel estimate value is determined based on time and frequency correlation information of a channel of a resource element in which the DM-RS symbol within the resource block is received.

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