Electronic device and method for obtaining narrowband random access signal

Abstract

According to an embodiment, a method performed by a device of a base station is provided. The method may include an operation of obtaining signals corresponding to a plurality of symbol groups of a narrowband random access channel (NPRACH) transmission. The method may include an operation of determining inter-symbol correlation information for at least one symbol group of the plurality of symbol groups. The method may include an operation of determining a frequency offset based on inter-symbol correlation information. The method may include an operation of obtaining a random access signal corresponding to the signal based on the frequency offset. The symbols in a predetermined symbol group of the plurality of symbol groups may correspond to the same subcarrier.

Description

Technical Field

[0001] The following description relates to electronic devices and methods for receiving narrowband random access signals. Background Art

[0002] Mobile communication networks utilize narrowband (NB) Internet of Things (IoT) technology. NB-IoT technology has low transmission speeds due to its limited bandwidth, but it offers wide coverage. NB-IoT technology enables low-cost IoT devices with improved coverage and long battery life. Furthermore, NB-IoT technology can collect information data from many IoT devices using less power.

[0003] The above information may be provided as related art for the purpose of assisting in understanding the present disclosure. No statement or determination is made as to whether any of the above may be applied as prior art related to the present disclosure. Summary of the Invention

[0004] Technical Solution

[0005] In an embodiment, a method performed by a base station device is provided. The method may include obtaining a signal corresponding to a plurality of symbol groups transmitted via a narrowband random access channel (NPRACH). The method may include determining inter-symbol correlation information for at least one of the plurality of symbol groups. The method may include determining a frequency offset based on the inter-symbol correlation information. The method may include obtaining a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier.

[0006] In an embodiment, a base station device is provided. The device may include a memory, at least one transceiver, and at least one processor coupled to the memory and the at least one transceiver. The at least one processor may be configured to obtain a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH). The at least one processor may be configured to determine inter-symbol correlation information for at least one of the plurality of symbol groups. The at least one processor may be configured to determine a frequency offset based on the inter-symbol correlation information. The at least one processor may be configured to obtain a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier.

[0007] In an embodiment, a digital unit (DU) is provided. The DU may include a memory storing instructions, at least one transceiver, and at least one processor. When executed by the at least one processor, the instructions may cause the DU to obtain a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH), determine inter-symbol correlation information for at least one symbol group in the plurality of symbol groups, determine a frequency offset based on the inter-symbol correlation information, and obtain a random access signal corresponding to the signal based on the frequency offset, wherein symbols in each symbol group in the plurality of symbol groups may correspond to the same subcarrier.

[0008] In an embodiment, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium may store instructions that, when executed by a processor of a digital unit (DU), cause the DU to perform operations including obtaining a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH), determining inter-symbol correlation information for at least one of the plurality of symbol groups, determining a frequency offset based on the inter-symbol correlation information, and obtaining a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A wireless communication system is shown.

[0010] Figure 2 The fronthaul interface is shown.

[0011] Figure 3 Examples of resource structures in the time and frequency domains are shown.

[0012] Figure 4 An example of a random access procedure is shown.

[0013] Figure 5 An example of a narrowband physical random access channel (NPRACH) transmission is shown.

[0014] Figure 6 An example of frequency offset compensation is shown.

[0015] Figures 7a and 7b An example of inter-symbol correlation information is shown.

[0016] Figure 8 An example of a calculation unit for calculating inter-symbol correlation information is shown.

[0017] Figure 9 Functional blocks for determining a frequency offset based on inter-symbol correlation information are shown.

[0018] Figure 10 The operation flow of a base station device for obtaining a random access signal is shown.

[0019] Figure 11a A functional configuration of a distributed unit (DU) according to an embodiment is shown.

[0020] Figure 11b A functional configuration of a radio unit (RU) according to an embodiment is shown. DETAILED DESCRIPTION

[0021] The terms used in this disclosure are only used to describe specific embodiments and may not be intended to limit the scope of another embodiment. Unless the context clearly indicates otherwise, a singular expression may include a plural expression. The terms used herein (including technical or scientific terms) may have the same meaning as that generally understood by those of ordinary skill in the art described in this disclosure. Among the terms used in this disclosure, the terms defined in general dictionaries may be interpreted as having the same or similar meaning as the contextual meaning of the relevant technology, and unless clearly defined in this disclosure, are not interpreted as ideal or overly formal meanings. In some cases, even the terms defined in this disclosure cannot be interpreted as excluding embodiments of the present disclosure.

[0022] In the various embodiments of the present disclosure described below, a hardware method will be described as an example. However, since the various embodiments of the present disclosure include technologies using both hardware and software, the various embodiments of the present disclosure do not exclude software-based methods.

[0023] In the following description, for the convenience of description, terms referring to signals (e.g., signal, information, message, and signaling), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), and opportunity), terms used for computing states (e.g., steps, operations, and procedures), terms referring to data (e.g., packet, user stream, information, bit, symbol, and codeword), terms referring to channels, terms referring to network entities, terms referring to components of a device, etc. are shown. Therefore, the present disclosure is not limited to the terms described below, and other terms having the same technical meaning may be used.

[0024] In addition, in the present disclosure, the terms "greater than" or "less than" may be used to determine whether a specific condition is satisfied or achieved, but this is merely an example description and does not exclude the description of "greater than or equal to" or "less than or equal to." A condition described as "greater than or equal to" can be replaced with "greater than," a condition described as "less than or equal to" can be replaced with "less than," and a condition described as "greater than or equal to and less than" can be replaced with "greater than and less than or equal to." In addition, hereinafter, 'A' to 'B' refers to at least one of the elements A (inclusive) to B (inclusive). hereinafter, 'C' and / or 'D' refers to at least one of 'C' or 'D', i.e., {'C', 'D', and 'C' and 'D'}.

[0025] This disclosure uses terminology used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP), Scalable Radio Access Network (xRAN), and Open Radio Access Network (O-RAN)) to describe various embodiments. However, this is merely an example for explanation. Various embodiments of the present disclosure may also be applied to other communication systems.

[0026] Figure 1 An example of a wireless communication system is shown.

[0027] refer to Figure 1 , Figure 1 1 and 2. A base station 110 and a terminal 120 are shown as a part of a node using a wireless channel in a wireless communication system. Figure 1 Only one base station is shown, but the wireless communication system may further include another base station that is the same as or similar to the base station 110 .

[0028] Base station 110 is a network infrastructure for providing wireless access to terminal 120. Base station 110 has coverage defined by the distance over which it can transmit signals. In addition to being a base station, base station 110 may also be referred to as an "access point (AP)," "eNode B (eNB)," "fifth generation node," "next generation Node B (gNB)," "radio point," "transmission / reception point (TRP)," or another technically equivalent term.

[0029] The terminal 120, which is a device used by a user, communicates with the base station 110 through a wireless channel. The link from the base station 110 to the terminal 120 is called a downlink (DL), and the link from the terminal 120 to the base station 110 is called an uplink (UL). Figure 1Although not shown in FIG, terminal 120 and another terminal may communicate with each other via a wireless channel. In this case, the device-to-device link (D2D) between terminal 120 and another terminal is referred to as a sidelink, and sidelink can be used interchangeably with the PC5 interface. In some other embodiments, terminal 120 can be operated without user involvement. Depending on the embodiment, terminal 120, as a device performing machine-type communication (MTC), may not be carried by the user. Furthermore, depending on the embodiment, terminal 120 may be a narrowband (NB)-Internet of Things (IoT) device.

[0030] In addition to the terminal, the terminal 120 may also be referred to as “user equipment (UE)”, “customer premises equipment (CPE)”, “mobile station”, “subscriber station”, “remote terminal”, “wireless terminal”, “electronic device” or another term having the equivalent technical meaning.

[0031] Base station 110 and terminal 120 can perform beamforming. Base station 110 and terminal 120 can transmit and receive wireless signals in relatively low frequency bands, such as Frequency Range 1 (FR1) for NR. Furthermore, base station 110 and terminal 120 can transmit and receive wireless signals in relatively high frequency bands, such as FR2 (or FR2-1, FR2-2, FR2-3), or FR3 for NR, and mmWave bands (e.g., 28 GHz, 30 GHz, 38 GHz, or 60 GHz). To improve channel gain, base station 110 and terminal 120 can perform beamforming. Beamforming can include transmit beamforming and receive beamforming. Base station 110 and terminal 120 can assign directionality to transmitted or received signals. To this end, base station 110 and terminal 120 can select a serving beam through beam searching or beam management procedures. After selecting a serving beam, subsequent communications can be performed using resources that are in a QCL relationship with the resource to which the serving beam was transmitted.

[0032] If large-scale characteristics of a channel through which symbols are transmitted on a first antenna port can be estimated from a channel through which symbols are transmitted on a second antenna port, then the first antenna port and the second antenna port may be estimated to be in a QCL relationship. For example, the large-scale characteristics may include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, and spatial receiver parameters.

[0033] exist Figure 1In the description above, both base station 110 and terminal 120 have been described as performing beamforming, but the embodiments of the present disclosure are not necessarily limited to this. In some embodiments, the terminal may or may not perform beamforming. Furthermore, the base station may or may not perform beamforming. In other words, only one of the base station and the terminal may perform beamforming, or both the base station and the terminal may not perform beamforming.

[0034] In this disclosure, a beam, which refers to a spatial stream of a signal in a wireless channel, may be formed by one or more antennas (or antenna elements), and this formation process may be referred to as beamforming. Beamforming may include at least one of analog beamforming or digital beamforming (e.g., precoding). Reference signals transmitted based on beamforming may include, for example, a demodulation reference signal (DM-RS), a channel state information reference signal (CSI-RS), a synchronization signal / physical broadcast channel (SS / PBCH), and a sounding reference signal (SRS). Furthermore, information about each reference signal, such as CSI-RS resources or SRS resources, may be used as a configuration for each reference signal, and this configuration may include information associated with the beam. This information associated with the beam may include whether a corresponding configuration (e.g., a CSI-RS resource) uses the same spatial domain filter as another configuration (e.g., another CSI-RS resource within the same CSI-RS resource set) or a different spatial domain filter, or whether it is quasi-co-located (QCL) with a reference signal, and if so, its QCL type (e.g., QCL type A, B, C, or D).

[0035] Figure 2 An example of a base station is shown. Figure 2 In the , DU and RU are described, where the functions of the base station are divided and implemented by different entities. The fronthaul interface can be used for communication between DU and RU. Fronthaul refers to the communication between entities between the wireless RAN and the base station, which is different from the backhaul between the base station and the core network. Figure 2 , it shows an example of a fronthaul structure between DU 210 and one RU 220, but this is only for ease of explanation and the present disclosure is not limited thereto. In other words, embodiments of the present disclosure can also be applied to a fronthaul structure between one DU and multiple RUs. For example, embodiments of the present disclosure can be applied to a fronthaul structure between one DU and two RUs. In addition, embodiments of the present disclosure can be applied to a fronthaul structure between one DU and three RUs.

[0036] Reference Figure 2, the base station 110 may include a DU 210 and a RU 220. Fronthaul 215 between the DU 210 and the RU 220 may be operated via an Fx interface. For the operation of the fronthaul 215, for example, interfaces such as an enhanced common public radio interface (eCPRI) and radio over Ethernet (ROE) may be used.

[0037] With the development of communication technology, mobile data traffic has increased, and accordingly, the bandwidth demand required for fronthaul between digital units and wireless units has increased significantly. In deployments such as centralized / cloud radio access networks (C-RAN), the DU can be implemented to perform functions related to the packet data convergence protocol (PDCP), radio link control (RLC), medium access control (MAC), and physical (PHY), and the RU can be implemented to perform more functions related to the PHY layer in addition to radio frequency (RF) functions.

[0038] The DU 210 can handle upper-layer functions of the wireless network. For example, it can perform functions of the MAC layer and portions of the PHY layer. Herein, the portion of the PHY layer is performed at a higher level among the PHY layer functions, and may include, for example, channel coding (or channel decoding), scrambling (or descrambling), modulation (or demodulation), and layer mapping (or layer demapping). According to embodiments, if the DU 210 complies with the O-RAN standard, it may be referred to as an O-RAN DU (O-DU). In embodiments of the present disclosure, the DU 210 can be replaced with the first network entity of a base station (e.g., a gNB), as needed.

[0039] The RU 220 can handle lower-layer functions of the wireless network. For example, it can perform portions of the PHY layer and RF functions. Herein, the PHY layer portion, which is performed at a relatively lower level than the DU 210, may include, for example, iFFT conversion (or FFT conversion), CP insertion (or removal), and digital beamforming. The RU 220 may be referred to as an "access unit (AU)," "access point (AP)," "transmit / receive point (TRP)," "remote radio head (RRH)," "radio unit (RU)," or another technically equivalent term. Depending on the embodiment, if the RU 220 complies with the O-RAN standard, it may be referred to as an O-RAN RU (O-RU). In embodiments of the present disclosure, the RU 220 may be replaced with a second network entity, such as a base station (e.g., a gNB), as needed.

[0040] exist Figure 2 , the base station 110 is shown to include a DU 210 and a RU 220, but the embodiments of the present disclosure are not limited thereto. The base station according to the embodiment may be implemented as a distributed deployment according to a centralized unit (CU) configured to perform functions of an upper layer of an access network (e.g., Packet Data Convergence Protocol (PDCP) or Radio Resource Control (RRC)) and a distributed unit (DU) configured to perform functions of a lower layer. As an example, the distributed unit (DU) may include Figure 2 The DU and RU are divided into a digital unit (DU) and a radio unit (RU). As another example, the DU can be referred to as a node implemented to execute the protocols of the CU and DU based on functional division. Also, as an example, between the core network (e.g., 5G core or next-generation core (NGC)) and the radio network (RAN), the base station can be implemented with a structure in which the CU, DU, and RU are arranged in this order. The interface between the CU and the distributed unit (DU) can be referred to as the F1 interface.

[0041] The centralized unit (CU) can process functions of a higher layer than the DU by connecting to one or more DUs. For example, the CU can process functions of the radio resource control (RRC) and packet data convergence protocol (PDCP) layers, and the DU and RU can process functions of the lower layers. The DU can perform some functions of the radio link control (RLC), medium access control (MAC), and physical (PHY) layers (high PHY), and the RU can process the remaining functions of the PHY layer (low PHY). In addition, as an example, the digital unit (DU) can be included in the distributed unit (DU) according to the distributed deployment implementation scheme of the base station. Hereinafter, unless otherwise defined, it will be described as the operation of the digital unit (DU) and the RU, but various embodiments of the present disclosure can be applied to a base station deployment including a CU, or a deployment in which the DU is directly connected to the core network (i.e., implemented by a base station (e.g., an NG-RAN node) in which the CU and DU are integrated as one entity).

[0042] Figure 3 Examples of resource structures in the time region and the frequency region are shown. Figure 3 The basic structure of a time-frequency region is shown, which is a radio resource region for transmitting data or control channels in downlink or uplink.

[0043] refer to Figure 3 , the horizontal axis indicates the time region, and the vertical axis indicates the frequency region. The minimum transmission unit in the time region is an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and N symbOFDM symbols 302 constitute one time slot 306. The length of a subframe is defined as 1.0 ms, and the length of a radio frame 314 is defined as 10 ms. The minimum transmission unit in the frequency region is a subcarrier, and the carrier bandwidth constituting the resource grid is represented by N. RB DL (in case of downlink) or N RB UL The RF link consists of 304 (in the case of uplink) subcarriers.

[0044] The basic unit of resources in the time-frequency domain is a resource element (hereinafter referred to as "RE") 312, which can be indicated by an OFDM symbol index and a subcarrier index. A resource block can include multiple resource elements. In the LTE system, a resource block (RB) (or physical resource block, hereinafter referred to as "PRB") is defined as N in the time domain. symb N consecutive OFDM symbols and frequency regions SC RB In the NR system, a resource block (RB) 308 may be defined as N consecutive subcarriers in a frequency region. SC RB One RB 308 includes N consecutive subcarriers 310 on the frequency axis. SC RB RE 312. Generally, the minimum unit of data transmission is RB, and the number of subcarriers N SC RB The number of CRBs is 12. A frequency region may include common resource blocks (CRBs). Physical resource blocks (PRBs) may be defined in a bandwidth part (BWP) on the frequency region. CRB and PRB numbers may be determined based on the subcarrier spacing. The data rate may increase in proportion to the number of RBs scheduled for a terminal.

[0045] In a NR system, in the case of a frequency division duplex (FDD) system operating by separating downlink and uplink transmissions by frequency, the downlink transmission bandwidth and uplink transmission bandwidth can be different. The channel bandwidth indicates the radio frequency (RF) bandwidth corresponding to the system transmission bandwidth. Table 1 shows a portion of the correspondence between the system transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in NR systems for frequency ranges below x GHz (e.g., frequency range (FR) 1 (310 MHz to 7125 MHz)). Table 2 shows a portion of the correspondence between the transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in NR systems for frequency ranges above y GHz (e.g., FR2 (24250 MHz-52600 MHz) or FR2-2 (52600 MHz to 71000 MHz)). For example, in an NR system with a 100 MHz channel bandwidth and 30 kHz subcarrier spacing, the transmission bandwidth consists of 273 RBs. In Tables 1 and 2, "N / A" indicates a bandwidth-subcarrier combination not supported in the NR system.

[0046] [Table 1]

[0047]

[0048] [Table 2]

[0049]

[0050] Figure 4 An example of a random access procedure is shown. The random access procedure may include signaling between a base station (eg, base station 110) and a terminal (eg, terminal 120). Figure 4 The operations of base station 110 are described in

[15] , but such description does not preclude at least some of the operations of base station 110 from being performed by DU 210 and at least some other operations from being performed by RU 220. That is, depending on the implementation method of base station 110, for example, all operations described below may be performed by a single network entity, or, as another example, the operations described below may be divided and performed by multiple network entities (e.g., DU 210 and RU 220). Terminal 120 may utilize NB-IoT technology, which is a technology for transmitting signals over a narrowband (e.g., 180 kHz). NB-IoT may also be referred to as cellular IoT (cIoT) or a term with equivalent technical meaning.

[0051] refer to Figure 4In operation 401, terminal 120 may transmit a random access signal to base station 110. The random access signal may be transmitted on a narrowband physical random access channel (NPRACH). Terminal 120 may receive system information related to the NPRACH from the base station. Based on the system information, terminal 120 may transmit a random access preamble to base station 110. The random access signal may be referred to as message 1 (MSG 1), PRACH, NPRACH, preamble, random access channel (RACH) preamble, RACH signal, random access preamble, or technically equivalent terms. Depending on the configuration of base station 110, terminal 120 may repeatedly transmit the random access signal. The number of repetitions of the random access signal may be configured based on the RRC configuration of base station 110 or system information.

[0052] In operation 402, base station 110 may send a random access response (RAR) to terminal 120. The random access response may be sent on a narrowband physical downlink shared channel (NPDSCH). The message including the random access response may include message 2 (MSG 2). In response to a random access preamble received from terminal 120, base station 110 may send this message to terminal 120. Downlink scheduling information for this message may be CRC-masked with a random access-radio network temporary identifier (random access-RNTI, RA-RNTI) and sent on a Layer 1 / L2 control channel (e.g., a narrowband physical control channel (NPDCCH)). Terminal 120, receiving the downlink scheduling signal masked with the RA-RNTI, may obtain and decode the random access response on the NPDSCH. For example, the random access response may include scheduling information for an uplink message described below. Furthermore, for example, the random access response may include information regarding repetitions of the uplink message.

[0053] In operation 403, terminal 120 may transmit an uplink message to base station 110. The uplink message may be transmitted on the narrowband physical uplink shared channel (NPUSCH). The uplink message may correspond to a scheduled transmission. Terminal 120 may transmit the uplink message to base station 110 based on the radio resource allocation information included in the random access response. The uplink message may be referred to as message 3 (MSG 3). Terminal 120 may repeat transmission of this uplink message as many times as received based on the random access response.

[0054] In operation 404, the base station 110 may send a contention resolution message to the terminal 120. The contention resolution message may be sent on the NPDSCH. The contention resolution message may be referred to as message 4 (MSG 4). For example, the contention resolution message may include an RRC connection establishment message. Although not in Figure 4, but the terminal 120 may send a connection establishment complete message to the base station after receiving the contention resolution message from the base station 110.

[0055] although Figure 4 A contention-based random access procedure has been described, but the embodiments of the present disclosure are not limited thereto. The operations related to the reception of a random access signal by an NB-IoT terminal of the present disclosure may also be applied to a non-contention-based random access procedure. In a non-contention-based random access procedure, base station 110 and terminal 120 may not perform operations 403 and 404.

[0056] As reference Figure 4 As described, base station 110 and terminal 120 can implement the Internet of Things using a narrowband (i.e., NB-IoT). For example, the narrowband can be 180 kHz. Terminal 120 using NB-IoT technology can be referred to as an NB-IoT UE. NB-IoT UEs can communicate in areas with poor channel conditions, such as under bridges, underwater, or at sea. To compensate for poor channel conditions, techniques such as channel-specific repetition and power boosting can be used. For example, power boosting techniques can include further reducing the frequency resource area to be transmitted within a specific frequency band, concentrating power per unit time on specific resources. As an example, when transmitting a specific signal via a resource block (RB) consisting of 12 resource elements (REs), a power allocation method can be used to allocate power, originally distributed throughout the RB, to specific REs, rather than allocating REs per RB. This method of performing communication by concentrating data and power on a single RE within an RB is referred to as a single-tone transmission method.

[0057] Figure 5 An example of narrowband physical random access channel (NPRACH) transmission is shown. NPRACH refers to the physical channel through which the random access signal of the NB-IoT UE is transmitted.

[0058] refer to Figure 5 Resource grid 500 indicates the time and frequency resources used to transmit random access signals. The horizontal axis of resource grid 500 indicates time, and the vertical axis indicates frequency. Random access signals can be transmitted in a narrowband. For example, the narrowband can be 180 kHz. One RE can correspond to 15 kHz, and 12 REs can form one RB, which can be narrowband.

[0059] The NB-IoT UE (e.g., terminal 120) may transmit a random access signal. For example, the NB-IoT UE may transmit the random access signal based on a repetition number. The repetition number may be indicated by configuration information received through RRC signaling of a base station (e.g., base station 110). The NB-IoT UE may repeat the transmission of the random access signal as many times as the repetition number. For example, when the repetition number is 1, the NB-IoT UE may transmit the random access signal. For another example, when the repetition number is 4, the NB-IoT UE may transmit the random access signal four times. For yet another example, when the repetition number is 16, the NB-IoT UE may transmit the random access signal sixteen times.

[0060] The random access signal used as a repeated reference may include four symbol groups. One symbol group 520 of the four symbol groups may include a cyclic prefix (CP) and five symbols. The four symbol groups may be set without a time gap between the symbol groups. Each of the four symbol groups may have an independent tone. For example, each of the four symbol groups may correspond to a specific subcarrier that is different from the subcarrier of another symbol group. The four symbol groups may sequentially include a first symbol group, a second symbol group, a third symbol group, and a fourth symbol group in one period. The length of the CP may vary according to the preamble format. For example, the length of the CP (T CP ) and the total length of the five symbols (T SEQ ) can be configured as shown in the following table. Here, the basic time unit is .

[0061] [Table 3]

[0062]

[0063] For example, assuming a repetition count of 4, the NB-IoT UE may transmit a random access signal during a first time interval 511 (e.g., 6.4 milliseconds). During the first time interval 511, the NB-IoT UE may transmit a preamble of a first symbol group on subcarrier #0. During the first time interval 511, the NB-IoT UE may transmit a preamble of a second symbol group on subcarrier #1. During the first time interval 511, the NB-IoT UE may transmit a preamble of a third symbol group on subcarrier #7. During the first time interval 511, the NB-IoT UE may transmit a preamble of a fourth symbol group on subcarrier #6. The NB-IoT UE may transmit the preamble corresponding to the random access signal in a narrowband (e.g., 180 kHz) and in the first time interval 511 corresponding to the first period through frequency hopping.

[0064] The NB-IoT UE may transmit a random access signal during a second time interval 512. The random access signal in the second time interval 512 is the same as the random access signal in the first time interval 511, but the frequency position may be changed. During the second time interval 512, the NB-IoT UE may transmit a preamble of a first symbol group on subcarrier #2. During the second time interval 512, the NB-IoT UE may transmit a preamble of a second symbol group on subcarrier #3. During the second time interval 512, the NB-IoT UE may transmit a preamble of a third symbol group on subcarrier #9. During the second time interval 512, the NB-IoT UE may transmit a preamble of a fourth symbol group on subcarrier #8. The NB-IoT UE may transmit the preamble corresponding to the random access signal in a narrowband (e.g., 180 kHz) and in the second time interval 512 corresponding to the second period through frequency hopping.

[0065] The NB-IoT UE may transmit a random access signal during a third time interval 513. During the third time interval 513, the NB-IoT UE may transmit a preamble of a first symbol group on subcarrier #10. During the third time interval 513, the NB-IoT UE may transmit a preamble of a second symbol group on subcarrier #11. During the third time interval 513, the NB-IoT UE may transmit a preamble of a third symbol group on subcarrier #5. During the third time interval 513, the NB-IoT UE may transmit a preamble of a fourth symbol group on subcarrier #4. The NB-IoT UE may transmit a preamble corresponding to the random access signal in a narrowband (e.g., 180 kHz) and in a third time interval 513 corresponding to a third period through frequency hopping.

[0066] The NB-IoT UE may transmit a random access signal during a fourth time interval 514. During the fourth time interval 514, the NB-IoT UE may transmit a preamble of a first symbol group on subcarrier #8. During the fourth time interval 514, the NB-IoT UE may transmit a preamble of a second symbol group on subcarrier #9. During the fourth time interval 514, the NB-IoT UE may transmit a preamble of a third symbol group on subcarrier #3. During the fourth time interval 514, the NB-IoT UE may transmit a preamble of a fourth symbol group on subcarrier #2. The NB-IoT UE may transmit a preamble corresponding to the random access signal in a narrowband (e.g., 180 kHz) and in a fourth time interval 514 corresponding to a fourth period through frequency hopping.

[0067] As reference Figure 5As described above, the NB-IoT UE can send a random access preamble using a single-tone transmission method within the same symbol group in one transmission. At the same time, because the symbol group is designed with a small subcarrier spacing and a long CP, the detection performance of the random access signal is more sensitive to frequency offset than to time offset. In the single-tone transmission method, when the residual frequency offset relative to the subcarrier spacing (SCS) is large, the power of the received NPRACH preamble may leak to adjacent subcarriers, thereby increasing interference with other preambles. The increased interference causes the detection performance on the receiver side to degrade. Therefore, in order to compensate for the above-mentioned frequency offset, the base station (e.g., base station 110) or the base station's equipment (e.g., DU 210) can estimate the frequency offset.

[0068] One approach to achieving good reception performance in NB-IoT systems is to detect random access signals by jointly estimating uplink timing and frequency offset (i.e., through joint estimation). While jointly estimating uplink timing and frequency offset provides optimal performance when detecting random access signals, it also suffers from high implementation complexity. This is discussed below.

[0069] The random access signal may include multiple OFDM symbols. The random access signal may include M symbol groups, and each symbol group may include L symbols. As an example, a received signal at the lth symbol of the mth symbol group among the M symbol groups may be expressed as follows.

[0070] [Equation 1]

[0071]

[0072] here, indicates the subcarrier corresponding to the mth symbol group, and Indicates the received signal at the lth symbol of the mth symbol group. indicates the channel coefficient at the lth symbol of the mth symbol group, Indicates the number of samples of CP, indicates the number of samples of a symbol, D indicates the time offset (i.e., the timing advance (TA) of the uplink timing), and Indicates frequency offset.

[0073] In this equation, it is assumed that the channel coefficient The phase change of the random access signal is equal to the period of the NPRACH random access signal, and the phase change of the random access signal is determined by the time offset D and the frequency offset Sure.

[0074] A base station (eg, base station 110) or a DU of a base station (eg, DU 210) may generate a signal with a time offset D and a frequency offset The base station or DU 210 can identify the correlation between the local sequence, symbol group m, and symbol index l within the symbol group based on the local sequence. When the signal is located at a position corresponding to the actual time offset and frequency offset, the base station 110 can obtain the peak energy based on the correlation. For example, the peak energy can be obtained based on the following equation.

[0075] Equation 2

[0076]

[0077] Based on Equations 1 and 2, the correlation between the time offset and the frequency offset can be configured based on the following equation: By jointly estimating a given time offset and frequency offset, the time offset and frequency offset that maximize the correlation value (ie, have the maximum peak energy) can be estimated.

[0078] Equation 3

[0079]

[0080] A two-dimensional FFT can be used to estimate the time offset and frequency offset that provide the maximum correlation based on Equation 3. For example, the right side of Equation 3 can be transformed into the following equation.

[0081] Equation 4

[0082]

[0083] Based on the equation 4 , you can get The estimated results of time offset within the range and The estimated result of the frequency offset (e.g., normalized frequency offset) within the range.

[0084] 3GPP NB-IoT's random access signal uses a single tone and employs a multi-level frequency hopping method, in which the tone changes at regular intervals. As mentioned above, estimating both uplink timing and frequency offset simultaneously poses a problem of high implementation complexity when detecting random access signals. To address this issue, embodiments of the present disclosure describe a technique for identifying frequency offsets within a symbol group corresponding to a specific time period by using correlation combinations between symbols.

[0085] Figure 6 An example of frequency offset compensation is shown. Figure 6, functional blocks for processing signals received through antennas are described. Each functional block can be understood as an operation at a network entity (eg, base station 110, DU 210, or RU 220).

[0086] Reference Figure 6 In operation 611, the base station 110 may perform gap and CP removal. According to the 3GPP NB-IoT standard, gaps and CPs may be removed from the random access signal received from each antenna.

[0087] The base station 110 may perform frequency shift in operation 613. The base station 110 may perform frequency shift on the signal from which the gap and the CP have been removed.

[0088] In operation 615 , the base station 110 may perform automatic gain control (AGC). The base station may determine the gain and phase to be applied to the signal obtained in operation 613 through AGC.

[0089] In operation 617, the base station 110 may perform FFT. The base station 110 may perform FFT on the signal obtained through operation 615 to change the signal from the time domain to the frequency domain.

[0090] In operation 619, the base station 110 may perform subcarrier demapping. For example, the base station 110 may demap the output signal of operation 617 to subcarriers used in the random access signal (eg, 48=12×4 subcarriers).

[0091] In operation 621, the base station 110 may perform subcarrier buffering. The demapped signal may be buffered until the result of the frequency offset estimation is derived.

[0092] In operation 623, base station 110 may estimate a frequency offset. Base station 110 may estimate the frequency offset based on an inter-symbol correlation calculation. The estimated frequency offset may be used to compensate for frequency differences in the random access signal. For example, the functional block corresponding to operation 623 (i.e., a frequency offset estimator) may include a total noise estimator, a frequency correlator, and a frequency offset determination block.

[0093] The base station 110 may perform frequency offset compensation in operation 625. The base station 110 may perform frequency offset compensation by applying the estimated frequency offset result to the demapped signal.

[0094] although Figure 6 Operations 601 to 625 in FIG. 6 are described as operations of the base station 110 , but embodiments of the present disclosure are not limited thereto. Figure 6The operations described in the figure can be divided into multiple network entities (e.g., DU 210 and RU 220), and each network entity can be configured to perform the corresponding operation. In other words, in order to reduce the transmission capacity of the wired network and reduce the installation cost of the wired network, "function split" can be used, in which some functions of the DU's modem are offloaded to the RU to reduce the transmission capacity of the fronthaul. In order to reduce the load on the DU, the role of the RU, which usually only handles RF functions, can be extended to some functions of the physical layer. As the RU performs higher-layer functions, the throughput of the RU increases, which increases the transmission bandwidth in the fronthaul, and at the same time, the latency requirement constraints due to response processing may be reduced. At the same time, as the RU performs higher-layer functions, the virtualization gain decreases, and the size, weight, and cost of the RU increase. Considering the trade-off between the above-mentioned advantages and disadvantages, it is necessary to achieve optimal function split.

[0095] When transmitting downlink (DL) signals to terminal 120 via the wireless network, network entities may sequentially perform channel coding / scrambling, modulation, layer mapping, antenna mapping, RE mapping, digital beamforming (e.g., precoding), iFFT conversion / CP insertion, and RF conversion. When receiving uplink (UL) signals from terminal 120 via the wireless network, network entities may sequentially perform RF conversion, FFT conversion / CP removal, digital beamforming (pre-combining), RE demapping, channel estimation, layer demapping, demodulation, and decoding / descrambling. Based on the aforementioned trade-offs, the separation of uplink and downlink functions may be defined in various ways, depending on requirements and discussions within standards, between vendors, and so on. According to embodiments, in certain functional splits (e.g., Option 7-2x), RU 220 may perform iFFT conversion / CP insertion in the DL PHY functions and FFT conversion / CP removal in the UL PHY functions, while DU 210 may perform the remaining PHY functions. For example, operations 601 to 617 may be performed in the RU 220, and operations 619 to 625 may be performed in the DU 210. According to another embodiment, in a specific functional split (e.g., option 7-2), the RU 220 may perform RE mapping (or RE demapping) in both the DL and UL, and the DU 210 may perform higher PHY functions after RE mapping (or RE demapping). For example, operations 601 to 621 may be performed in the RU 220, and operations 623 to 625 may be performed in the DU 210. According to yet another embodiment, in a specific functional split (e.g., option 6), the RU 220 may perform encoding / scrambling (or decoding / descrambling) in both the DL and UL, and the DU 210 may perform higher PHY functions after modulation (or demodulation). For example, operations 601 to 625 may be performed in the RU 220.

[0096] For each receiving antenna, the signal received at the kth symbol of the lth group can be expressed as shown in the following equation.

[0097] Equation 5

[0098]

[0099] It means the signal received at the kth symbol of the i-th symbol group. K is 5, . Indicates the symbol interval ( ) during the period according to the frequency offset ( ) is the phase change amount. For example, the phase change amount can be expressed as shown in the following equation.

[0100] Equation 6

[0101]

[0102] When an unknown constant phase component and frequency offset exist within a time slot, the power density function (PDF) can be expressed as shown in the following equation.

[0103] Equation 7

[0104]

[0105] Indicates the received signal of group l ( ) PDF, any parameter of group l ( ) and the phase change . Indicates the variance of group 1. For example, the phase change amount and the received signal can be expressed as shown in the following equation.

[0106] Equation 8

[0107]

[0108] Indicates the received signal of group l ( ) PDF, any of the lth group parameter( ) and the amount of phase change. Indicates the variance of group 1. For example, the phase change amount and the received signal can be expressed as shown in the following equation.

[0109] Since any parameter ( ) is an undetermined parameter, so it can be determined as an estimate that can obtain a high PDF (e.g., maximize the PDF).

[0110] Equation 9

[0111]

[0112] Since any parameter ( ) is an undetermined parameter, so it can be determined as an estimate that achieves a high PDF (e.g., maximizes the PDF). Taking the logarithm of Equation 7, the following expansion can be derived.

[0113] Equation 10

[0114]

[0115] To find any parameter that maximizes Equation 10 ( ), differentiation can be performed on both sides. For example, the result of differentiation can be expressed as shown in the following equation.

[0116] Equation 11

[0117]

[0118] By replacing any parameter of Equation 11 ( ) into Equation 10, Equation 10 can be simplified as follows.

[0119] Equation 12

[0120]

[0121] By replacing any parameter of Equation 11 ( ) into Equation 10, Equation 10 can be simplified as follows.

[0122] Since Equation 10 is an arbitrary parameter of the first group ( ), so the log-likelihood of a total of l groups can be shown as the following equation.

[0123] Equation 13

[0124]

[0125] To find the phase change amount having the maximum value, the following equation can be used.

[0126] Equation 14

[0127]

[0128] The frequency offset may be derived using the phase change value estimated by Equation 14. For example, the frequency offset may be expressed as the following equation based on Equation 6.

[0129] Equation 15

[0130]

[0131] Indicates the estimated frequency offset.

[0132] Equation 13 can be expressed in the form of a correlation calculation as shown in the following equation.

[0133] Equation 16

[0134]

[0135] In Equation 16, if correlation calculations for the same symbol within a symbol group are grouped and organized, Equation 16 can be expressed as the following equation.

[0136] Equation 17

[0137]

[0138] Equation 18

[0139]

[0140] Assumptions , identify the largest PDF can be understood as identifying the maximum PDF that can be provided Identify the largest PDF file that can be used to provide It can be implemented in the form of FFT. For example, Equation 14 can be expressed as the following equation.

[0141] Equation 19

[0142]

[0143] Considering that the length of a symbol is T u (=1 / 3750), the estimated range of possible frequency offsets may be from -1875 Hz to 1875 Hz.

[0144] According to a specified technique (e.g., Luise algorithm), identify It can be approximated by the following equation.

[0145] Equation 20

[0146]

[0147] Equation 21

[0148]

[0149] Indicates the number of correlations between symbols. For example, in the inter-symbol correlation calculation, if there is a correlation calculation with a distance of 1 between symbols and a correlation calculation with a distance of 2 between symbols, It can be 2. The random access signal of NB-IoT sent on NPRACH can include four symbol groups, and each symbol group can include a total of five symbols. Therefore, the number of correlations between symbols in a symbol group can be less than or equal to 4.

[0150] For example, in which When is 4, the estimated range of the frequency offset in Equation 20 can be expressed as the following equation.

[0151] Equation 22

[0152]

[0153] Based on the above equation, the present disclosure describes a technique for achieving high-performance frequency offset estimation with simplified implementation complexity. As described in Equation 20, the frequency offset can be estimated using correlation calculations between symbols within a symbol group corresponding to the same subcarrier. Hereinafter, information regarding correlation calculations between symbols may be referred to as inter-symbol correlation information.

[0154] Figures 7a and 7b An example of inter-symbol correlation information is shown. The inter-symbol correlation information can be obtained for each symbol group.

[0155] refer to Figure 7a and Figure 7b , the symbol group 700 may include a CP 710 , a first symbol 721 , a second symbol 722 , a third symbol 723 , a fourth symbol 724 , and a fifth symbol 725 .

[0156] The first correlation information 751 may include correlation values between adjacent symbols. For example, the correlation value may include a correlation value between the first symbol 721 and the second symbol 722. The correlation value may include a correlation value between the second symbol 722 and the third symbol 723. The correlation value may include a correlation value between the third symbol 723 and the fourth symbol 724. The correlation value may include a correlation value between the fourth symbol 724 and the fifth symbol 725. The first correlation information 751 may be determined based on the correlation values. For example, the first correlation information 751 may include a sum of the correlation values.

[0157] The second correlation information 752 may include correlation values between symbols having a one-symbol interval. For example, the correlation value may include a correlation value between the first symbol 721 and the third symbol 723. The correlation value may include a correlation value between the second symbol 722 and the fourth symbol 724. The correlation value may include a correlation value between the third symbol 723 and the fifth symbol 725. The second correlation information 752 may be determined based on the correlation values. For example, the second correlation information 752 may include the sum of the correlation values.

[0158] The third correlation information 753 may include correlation values between symbols having a symbol interval corresponding to two symbols. For example, the correlation value may include a correlation value between the first symbol 721 and the fourth symbol 724. The correlation value may include a correlation value between the second symbol 722 and the fifth symbol 725. The third correlation information 753 may be determined based on the correlation value. For example, the third correlation information 753 may include the sum of the correlation values.

[0159] The fourth correlation information 754 may include a correlation value having a symbol interval corresponding to three symbols. For example, the correlation value may include a correlation value between the first symbol 721 and the fifth symbol 725.

[0160] Figure 8 An example of a calculation unit for calculating inter-symbol correlation information is illustrated. The calculation unit can be used to derive Figure 7a and Figure 7b The inter-symbol correlation information.

[0161] refer to Figure 8 , the symbol group 700 may be input to the calculation unit. The calculation unit may include a selection block 801. The calculation unit may be configured to select an antenna and a subcarrier corresponding to the symbol group 700. The calculation unit may obtain a signal x(n) corresponding to the selected subcarrier. The calculation unit may include a correlator. The correlator may perform correlation between symbols separated by a certain symbol interval (e.g., 0 symbols, 1 symbol, 2 symbols, and 3 symbols) of the demapped signal. The correlation calculation operation of the calculation unit may include obtaining operation. This can correspond to the relevant calculations of equations 18 to 21.

[0162] Equation 23

[0163]

[0164] Here, x(n) represents the signal of the symbol group unit selected for each subcarrier of each antenna. k indicates the symbol distance (for example, the symbol distance between the first symbol 721 and the third symbol 723 is 2), and n indicates the symbol position (for example, n = 0 corresponds to the first symbol 721). A different time delay can be applied for each k.

[0165] For example, the calculation unit may obtain a first delayed signal by inputting the signal into the first delay unit 811. The calculation unit may obtain a correlation value by performing a conjugate calculation between the signal and the first delayed signal. The calculation unit may obtain the first correlation information 751 by adding the correlation values via the first adder 821. For example, the first adder 821 may be configured to output the first correlation information 751 by adding the correlation value between the first symbol 721 and the second symbol 722, the correlation value between the second symbol 722 and the third symbol 723, the correlation value between the third symbol 723 and the fourth symbol 724, and the correlation value between the fourth symbol 724 and the fifth symbol 725.

[0166] For example, the calculation unit may obtain the second delayed signal by inputting the signal into the second delay unit 812. The calculation unit may obtain a correlation value by performing a conjugate calculation between the signal and the second delayed signal. The calculation unit may obtain the second correlation information 752 by adding the correlation values via the second adder 822. For example, the second adder 822 may be configured to output the second correlation information 752 by adding the correlation value between the first symbol 721 and the third symbol 723, the correlation value between the second symbol 722 and the fourth symbol 724, and the correlation value between the third symbol 723 and the fifth symbol 725.

[0167] For example, the calculation unit may obtain a third delayed signal by inputting the signal into the third delay unit 813. The calculation unit may obtain a correlation value by performing a conjugate calculation between the signal and the third delayed signal. The calculation unit may obtain third correlation information 753 by adding the correlation values via the third adder 823. For example, the third adder 823 may be configured to output the third correlation information 753 by adding the correlation value between the first symbol 721 and the fourth symbol 724 and the correlation value between the second symbol 722 and the fifth symbol 725.

[0168] For example, the calculation unit may obtain a fourth delayed signal by inputting the signal into the fourth delay unit 814. The calculation unit may obtain a correlation value by performing a conjugate calculation between the signal and the fourth delayed signal. The correlation value may correspond to the fourth correlation information 754.

[0169] exist Figure 8, an example of outputting correlation information of a symbol group (e.g., first correlation information 751, second correlation information 752, third correlation information 753, and fourth correlation information 754) is described. The base station 110 can obtain the correlation information of each symbol group. The base station 101 can determine the frequency offset based on the correlation information of each symbol group. Figure 9 , describing operations for determining a frequency offset based on correlation information for each symbol group.

[0170] Figure 9 The following illustrates functional blocks for determining a frequency offset based on inter-symbol correlation information. Each functional block can be understood as an operation within a network entity (e.g., base station 110, DU 210, or RU 220). The random access signal on the NPRACH can be repeatedly transmitted. A transmission may include four symbol groups. Each symbol group may be referred to as a preamble unit. The base station may output correlation information corresponding to each group (i.e., each preamble unit).

[0171] Reference Figure 9 , the base station 110 may perform scaling. The base station 110 may perform scaling on the correlation information. In operation 911, the base station 110 may perform scaling on the first correlation information 751. For example, the base station 110 may scale the first correlation information 751 with the equation 20. The corresponding scaling factor is applied to the first correlation information 751. As an example, since K=5 and k of the first correlation information 751 is 1, the base station 110 may apply a scaling of 1 / 4 to the first correlation information 751. Since the first correlation information 751 includes the sum of four correlation values, a scaling value of 1 / 4 may be applied to derive a phase change per unit length (e.g., a length corresponding to one symbol distance). Subsequently, in operation 921, the base station 110 may sum the scaling results of the first correlation information 751 for each symbol group. The base station 110 may sum the values of the first correlation information 751 for all symbol groups corresponding to the repetition. T indicates the total number of all repeated symbol groups. For example, if the number of repetitions is 8, the base station 110 may sum a total of 32 values of the first correlation information 751.

[0172] In operation 912, base station 110 may scale the second correlation information 752. For example, base station 110 may apply a scaling factor of 1 / 3 to the second correlation information 752 based on Equation 20. Since second correlation information 752 includes the sum of three correlation values, the scaling factor of 1 / 3 may be applied to derive a phase change per unit length (e.g., a length corresponding to one symbol distance). Subsequently, in operation 922, base station 110 may sum the scaling results of the second correlation information 752 for each symbol group. Base station 110 may sum the values of the second correlation information 752 for all symbol groups corresponding to the repetition. T indicates the total number of all repeated symbol groups. For example, if the number of repetitions is 8, base station 110 may sum a total of 32 values of the second correlation information 752.

[0173] In operation 913, the base station 110 may scale the third correlation information 753. For example, the base station 110 may apply a scaling factor of 1 / 2 to the third correlation information 753 based on Equation 20. Since the third correlation information 753 includes the sum of two correlation values, the scaling factor of 1 / 2 may be applied to derive a phase change per unit length (e.g., a length corresponding to one symbol distance). Subsequently, in operation 923, the base station 110 may sum the scaling results of the third correlation information 753 for each symbol group. The base station 110 may sum the values of the third correlation information 753 for all symbol groups corresponding to the repetition. T indicates the total number of all repeated symbol groups. For example, if the number of repetitions is 8, the base station 110 may sum a total of 32 values of the third correlation information 753.

[0174] In operation 914, the base station 110 may scale the fourth correlation information 753. For example, the base station 110 may apply a scaling factor of 1 to the fourth correlation information 754 based on Equation 20. According to another embodiment, the scaling block corresponding to operation 914 may be omitted. Subsequently, in operation 924, the base station 110 may sum the scaling results of the fourth correlation information 754 for each symbol group. The base station 110 may sum the values of the fourth correlation information 754 for all symbol groups corresponding to the repetition. T indicates the total number of all repeated symbol groups. For example, when the number of repetitions is 8, the base station 110 may sum a total of 32 values of the fourth correlation information 754.

[0175] In operation 930, the base station 110 may combine the output of operation 921, the output of operation 922, the output of operation 923, and the output of operation 924. The base station 110 may combine the correlation values R(x) corresponding to all repetitions and all symbol groups. For example, operation 930 may correspond to the equation 20. Here, the summation operation of the symbol group may correspond to Equation 21. The base station 110 may store the correlation values over the entire period corresponding to the NPRACH transmission. The base station 110 may add up the accumulated correlation values.

[0176] In operation 940, the base station 110 may determine a frequency offset based on the combined value. The base station 110 may determine an angle based on the combined value. The base station 110 may obtain a phase change amount by scaling the angle. The base station 110 may determine a frequency offset corresponding to the phase change amount. For example, the base station 110 may determine the frequency offset corresponding to the phase change amount by using Equation 20. To determine the angle corresponding to the phase change amount. Base station 110 can determine the phase change amount and frequency offset by applying a scaling corresponding to 2 / (M+1) in Equation 20. Equation 6 may be used to describe the relationship between the phase change amount and the frequency offset. For example, when a random access signal on an NPRACH is received, M may be 4. At operation 940, a frequency offset may be determined for each antenna. The determined frequency offset may be used to remove the frequency offset component of the buffered random access signal (e.g., the buffering in operation 621).

[0177] exist Figure 9 In the description, the inter-symbol correlation values for all repetitions of the NPRACH transmission and all symbol groups within each repetition are summed, and the frequency offset is determined based on the summed results. However, the embodiments of the present disclosure are not limited thereto. To further simplify computational complexity, at least some of the repetitions or symbol groups can be excluded from the summation of the correlation calculations. The accuracy of the NPRACH frequency offset is a trade-off between performance and computational complexity. Even if accuracy is slightly reduced due to approximation, efficient modem operation can be achieved by reducing computational effort.

[0178] According to an embodiment, instead of repeating all NPRACH transmissions, the frequency offset may be determined using inter-symbol correlation information for at least one NPRACH transmission corresponding to a portion of the repetitions. For example, assuming the NPRACH preamble is repeated eight times, base station 110 may determine the frequency offset for the symbol groups of the second, fourth, sixth, and eighth transmissions based on the correlation information for each symbol group. For another example, assuming the NPRACH preamble is repeated 32 times, base station 110 may determine the frequency offset for the symbol groups of the first, ninth, seventeenth, and twenty-fifth transmissions based on the correlation information for each symbol group.

[0179] According to an embodiment, instead of transmitting all symbol groups for the NPRACH, correlation information for one of the four symbol groups may be used to determine the frequency offset. For example, assume that the NPRACH preamble is repeated four times. One transmission of the NPRACH preamble may include transmissions corresponding to the four symbol groups. The correlation information regarding one transmission may include inter-symbol correlation information for the first symbol group of the four symbol groups. The base station 110 may output the inter-symbol correlation information for the first symbol group in each repetition and determine the frequency offset by combining the output correlation information.

[0180] Figure 10 FIG. 2 shows an operation flow of a device (eg, DU 210 ) of a base station (eg, base station 110 ) for obtaining a random access signal.

[0181] refer to Figure 10 In operation 1001, a device may obtain signals corresponding to multiple symbol groups of an NPRACH transmission. The NPRACH transmission may be repeated N times. N may be configured for an NB-IoT UE (e.g., terminal 120) through RRC signaling from a network node. The multiple symbol groups may include symbol groups corresponding to N repetitions (N is an integer greater than or equal to 1) (e.g., N is 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, and 2048). One transmission may include the transmission of four symbol groups. For example, when the number of repetitions (N) is 32, the number of symbol groups may be 128. For another example, when the number of repetitions is 4, the number of symbol groups may be 16. For example, terminal 120 may transmit multiple random access preambles corresponding to the NPRACH transmission to a RU (e.g., RU 220). RU 220 may perform physical layer processing such as CP removal and FFT, and may transmit the processed signals to DU 210 for modem-side calculations.

[0182] In operation 1003, the device may determine inter-symbol correlation information for at least one symbol group. The device may identify at least one symbol group from among a plurality of symbol groups for use in determining a frequency offset. Depending on an embodiment, the device may identify at least one repetition corresponding to a subset among all repetitions. The device may identify a symbol group corresponding to the at least one repetition (four symbol groups per repetition). Additionally, depending on an embodiment, the device may identify a subset (e.g., one symbol group or two symbol groups) among the four symbol groups for each repetition. The device may identify at least one symbol group for each repetition (where the number of at least one symbol group is less than or equal to three). Additionally, depending on an embodiment, the device may identify some symbol groups (e.g., one symbol group or two symbol groups) for some repetitions (e.g., half the total number of repetitions) among all repetitions. Additionally, depending on an embodiment, the device may identify all symbol groups for all repetitions. In other words, for high performance, the device may calculate phase change amounts for all possible symbol groups.

[0183] The device may determine inter-symbol correlation information for at least one symbol group. The symbol group may include five symbols. The device may determine inter-symbol correlation information for each symbol group in the at least one symbol group. The inter-symbol correlation information may be determined based on correlation values between two symbols within the symbol group. For example, the inter-symbol correlation information may include first correlation information, which is a correlation calculation between adjacent symbols (with a symbol distance of 1). The first correlation information may be the sum of correlation values between the adjacent symbols. Furthermore, for example, the inter-symbol correlation information may include second correlation information, which is a correlation calculation between symbols with a symbol distance of 2. The second correlation information may be the sum of correlation values between symbols with a symbol distance of 2. Furthermore, for example, the inter-symbol correlation information may include third correlation information, which is a correlation calculation between symbols with a symbol distance of 3. The third correlation information may be the sum of correlation values between symbols with a symbol distance of 3. Furthermore, for example, the inter-symbol correlation information may include fourth correlation information, which is a correlation calculation between symbols with a symbol distance of 4. The fourth correlation information may be the sum of correlation values between symbols with a symbol distance of 4.

[0184] In operation 1005, the device may determine a frequency offset based on the inter-symbol correlation information. The device may combine values corresponding to first correlation information for a symbol group. The device may determine first cumulative correlation information by adding the values. For example, the symbol group may be the at least one symbol group identified in operation 1003. The device may also combine values corresponding to second correlation information for the symbol group. The device may determine second cumulative correlation information by adding the values corresponding to the second correlation information. The device may also combine values corresponding to third correlation information for the symbol group. The device may determine third cumulative correlation information by adding the values corresponding to the third correlation information. The device may also combine values corresponding to fourth correlation information for the symbol group. The device may determine fourth cumulative correlation information by adding the values corresponding to the fourth correlation information.

[0185] The device may determine a total correlation value based on the first cumulative correlation information, the second cumulative correlation information, the third cumulative correlation information, and the fourth cumulative correlation information. The device may determine angle information of the total correlation value. For example, the device may determine the angle information of the total correlation value by the equation corresponding to Equation 20. The device may determine the angle information. The device may obtain the phase change amount based on the number of correlation calculations (eg, M) with different symbol lengths in the inter-symbol correlation information. The device may determine the frequency offset corresponding to the phase change amount.

[0186] In operation 1007, the device may obtain a random access signal based on the frequency offset. The device may obtain a compensated signal in the frequency domain (hereinafter, the compensated signal) by applying the frequency offset to the received signal. The device may identify a sequence that provides a peak value greater than or equal to a threshold value in a correlation calculation with the compensated signal. The device may obtain a random access signal corresponding to the sequence.

[0187] Although not in Figure 10 Although not shown in FIG, the device may estimate the time offset based on the random access signal. The device may determine the timing advance (TA) corresponding to the time offset based on the compensation signal in which the frequency offset is compensated. Furthermore, the device may send a random access response to the NB-IoT UE to notify that the random access signal has been successfully acquired. For example, the device may send the random access response to the NB-IoT UE via RU 220.

[0188] Figure 11a FIG2 shows a functional configuration of a DU (eg, DU 210) according to an embodiment. Figure 11a The configuration illustrated in can be understood as Figure 11aConfiguration of the DU 210. Hereinafter, the terms '... unit' and '... device' used below refer to a unit that processes at least one function or operation, which can be implemented by hardware or software, or a combination of hardware and software.

[0189] refer to Figure 11a , the DU 210 includes a transceiver 1110 , a memory 1120 , and a processor 1130 .

[0190] The transceiver 1110 can perform functions for transmitting and receiving signals in a wired communication environment. The transceiver 1110 may include a wired interface for controlling direct device-to-device connections over a transmission medium (e.g., copper wire, optical fiber). For example, the transceiver 1110 can transmit electrical signals to another device over a copper wire or convert between electrical and optical signals. The DU 210 can communicate with the radio unit (RU) via the transceiver 1110.

[0191] Transceiver 1110 can also perform functions for transmitting and receiving signals in a wireless communication environment. For example, transceiver 1110 can convert between baseband signals and bit strings according to the system's physical layer specifications. For example, when transmitting data, transceiver 1110 generates complex-valued symbols by encoding and modulating the transmitted bit string. Furthermore, when receiving data, transceiver 1110 recovers the received bit string by demodulating and decoding the baseband signal. Furthermore, transceiver 1110 may include multiple transmit / receive paths.

[0192] The transceiver 1110 can send and receive signals. For example, the transceiver 1110 can send a management plane (M-plane) message. For example, the transceiver 1110 can send a synchronization plane (S-plane) message. For example, the transceiver 1110 can send a control plane (C-plane) message. For example, the transceiver 1110 can send a user plane (U-plane) message. For example, the transceiver 1110 can receive a U-plane message. Figure 11a Only the transceiver 1110 is shown in FIG, but according to another embodiment, the DU 210 may include two or more transceivers.

[0193] The transceiver 1110 transmits and receives the signals described above. Therefore, all or some of the transceiver 1110 may be referred to as a "communication unit," a "transmitting unit," a "receiving unit," or a "transmitting / receiving unit." In the following description, transmission and reception via a wireless channel are used to encompass the processing described above performed by the transceiver 1110. Depending on the embodiment, the transceiver 1110 may obtain a signal from a RU (e.g., RU 220) on which physical layer processing has been performed. For example, the transceiver 1110 may obtain a signal (e.g., a frequency domain signal) on which CP removal and FFT have been performed on the received signal.

[0194] Although not in Figure 11a Although not shown in FIG, transceiver 1110 may further include a backhaul transceiver for connecting to a core network or another base station. The backhaul transceiver provides an interface for communicating with other nodes in the network. In other words, the backhaul transceiver converts a bit string sent from the base station to another node (such as another access node, another base station, an upper node, and the core network) into a physical signal, and converts a physical signal received from another node into a bit string.

[0195] Memory 1120 stores basic programs, application programs, and data such as configuration information for the operation of DU 210. Memory 1120 can be referred to as a storage unit. Memory 1120 can be configured with volatile memory, nonvolatile memory, or a combination of volatile and nonvolatile memory. Furthermore, memory 1120 provides stored data upon request from processor 1130. Depending on the embodiment, memory 1120 can store inter-symbol correlation information of the present disclosure. For example, memory 1120 can store first correlation information (e.g., first correlation information 751). Memory 1120 can store second correlation information (e.g., first correlation information 752). Memory 1120 can store third correlation information (e.g., third correlation information 753). Memory 1120 can store fourth correlation information (e.g., fourth correlation information 754).

[0196] The processor 1130 controls the overall operation of the DU 210. The processor 1130 may be referred to as a control unit. For example, the processor 1130 sends and receives signals through the transceiver 1110 (or through the backhaul communication unit). In addition, the processor 1130 writes and reads data in the memory 1120. In addition, the processor 1130 may execute the functions of the protocol stack required in the communication standard. Although in Figure 11a Only the processor 1130 is shown in FIG, but according to another embodiment, the DU 210 may include two or more processors.

[0197] Depending on the embodiment, the processor 1130 may perform physical layer processing on a signal received from a RU (e.g., RU 220). For example, the processor 1130 may perform subcarrier demapping (RE demapping) on the received signal. For example, the processor 1130 may calculate inter-symbol correlation information based on the received signal. Furthermore, for example, the processor 1130 may estimate a frequency offset based on the received signal. The processor 1130 may also perform NPRACH detection on the received signal.

[0198] Figure 11a The configuration of the DU 210 shown in FIG is merely an example, and examples of DUs performing embodiments of the present disclosure are not limited to Figure 11a In some embodiments, certain configurations may be added, deleted, or changed.

[0199] Figure 11b FIG2 shows the functional configuration of a RU (eg, RU 220) according to an embodiment. Figure 11b The configuration illustrated in can be understood as Figure 2 Configuration of RU 220. Hereinafter, the terms '... unit' and '... device' used below refer to a unit that processes at least one function or operation, which can be implemented by hardware or software, or a combination of hardware and software.

[0200] refer to Figure 11b RU 220 includes an RF transceiver 1160 , a fronthaul transceiver 1165 , a memory 1170 , and a processor 1180 .

[0201] The RF transceiver 1160 performs functions for transmitting and receiving signals through wireless channels. For example, the RF transceiver 1160 up-converts a baseband signal to an RF band signal and then transmits it through an antenna, and down-converts the RF band signal received through the antenna to a baseband signal. For example, the RF transceiver 1160 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

[0202] The RF transceiver 1160 may include multiple transmit / receive paths. Furthermore, the RF transceiver 1160 may include an antenna unit. The RF transceiver 1160 may include at least one antenna array consisting of multiple antenna elements. In terms of hardware, the RF transceiver 1160 may include digital circuits and analog circuits (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuits and analog circuits may be implemented in a single package. Furthermore, the RF transceiver 1160 may include multiple RF chains. The RF transceiver 1160 may perform beamforming. To provide directionality to signals to be transmitted and received based on settings of the processor 1180, the RF transceiver 1160 may apply beamforming weights to the signals. Depending on the embodiment, the RF transceiver 1160 may include multiple antennas.

[0203] According to an embodiment, the RF transceiver 1160 can send and receive signals on the radio access network. For example, the RF transceiver 1160 can send downlink signals. The downlink signal may include a synchronization signal (SS), a reference signal (RS) (e.g., a cell-specific reference signal (CRS), a demodulation (DM)-RS), system information (e.g., MIB, SIB, remaining system information (RMSI), other system information (OSI)), a configuration message, control information, or downlink data. In addition, for example, the RF transceiver 1160 can receive an uplink signal. The uplink signal may include a random access-related signal (e.g., NPRACH, NPUSCH). According to an embodiment, the RF transceiver 1160 may receive a signal including a random access signal through a plurality of antennas provided in the RF transceiver 1160. Although in Figure 11b Only the RF transceiver 1160 is shown in FIG, but according to another embodiment, the RU 220 may include two or more RF transceivers.

[0204] The fronthaul transceiver 1165 may transmit and receive signals. According to an embodiment, the fronthaul transceiver 1165 may transmit and receive signals on the fronthaul interface. For example, the fronthaul transceiver 1165 may receive a management plane (M-plane) message. For example, the fronthaul transceiver 1165 may receive a synchronization plane (S-plane) message. For example, the fronthaul transceiver 1165 may receive a control plane (C-plane) message. For example, the fronthaul transceiver 1165 may transmit a user plane (U-plane) message. For example, the fronthaul transceiver 1165 may receive a U-plane message. According to an embodiment, the fronthaul transceiver 1165 may transmit a signal (e.g., a frequency domain signal) on which CP removal and FFT have been performed to the DU (e.g., DU 210). Although in Figure 11b Only the fronthaul transceiver 1165 is shown in FIG, but according to another implementation, the RU 220 may include two or more fronthaul transceivers.

[0205] As described above, the RF transceiver 1160 and the fronthaul transceiver 1165 transmit and receive signals. Therefore, all or some of the RF transceiver 1160 and the fronthaul transceiver 1165 may be referred to as a "communication unit," a "transmitting unit," a "receiving unit," or a "transmitting / receiving unit." In the following description, transmission and reception performed through a wireless channel are used to include the meaning that the RF transceiver 1160 performs the processing described above. In the following description, transmission and reception performed through a wireless channel are used to include the meaning that the RF transceiver 1160 performs the processing described above.

[0206] The memory 1170 stores basic programs, application programs, and data such as configuration information for the operation of the RU 220. The memory 1170 may be referred to as a storage unit. The memory 1170 may be configured with a volatile memory, a nonvolatile memory, or a combination of volatile and nonvolatile memories. In addition, the memory 1170 provides stored data according to a request from the processor 1180.

[0207] The processor 1180 controls the overall operation of the RU 220. The processor 1180 may be referred to as a control unit. For example, the processor 1180 transmits and receives signals through the RF transceiver 1160 or the fronthaul transceiver 1165. In addition, the processor 1180 writes and reads data in the memory 1170. In addition, the processor 1180 may execute the functions of the protocol stack required by the communication standard. Although Figure 11b Only processor 1180 is shown in the figure, but according to another embodiment, RU 220 may include two or more processors. Processor 1180, which is an instruction set or code stored in memory 1170, may be instructions / code that at least temporarily resides in processor 1180 or a memory space storing instructions / code, or may be part of the circuitry of processor 1180. In addition, processor 1180 may include various modules for performing communication. Processor 1180 may control RU 220 to perform operations according to the embodiments described later.

[0208] Figure 11b The configuration of the RU 220 shown in FIG is merely an example, and examples of RUs that implement embodiments of the present disclosure are not limited to Figure 11b In some embodiments, some configurations may be added, deleted, or changed.

[0209] In 3GPP NB-IoT systems, NPRACH transmissions are used to synchronize uplink timing. NPRACH transmissions may include multiple repetitions within a single tone (e.g., repetitions of preamble transmissions and repetitions of symbol groups within the preamble transmissions). To prevent degradation in reception performance due to frequency differences when receiving random access signals on the NPRACH at the base station, this disclosure describes techniques for determining frequency offset. Specifically, instead of estimating both the time offset and the frequency offset (which involves high complexity), computational effort can be reduced by first estimating and compensating for the frequency offset and then estimating the time offset. Furthermore, this disclosure can improve reception efficiency by reducing computational effort on the modem side (e.g., DU 210) and enhancing reception performance based on the characteristics of the NPRACH, which is repeatedly transmitted within a single tone.

[0210] Effects obtainable from the present disclosure are not limited to those described above, and any other effects not mentioned herein will be clearly understood from the following description by a person of ordinary knowledge in the art to which the present disclosure pertains.

[0211] In an embodiment, a method performed by a base station device is provided. The method may include obtaining a signal corresponding to a plurality of symbol groups transmitted via a narrowband random access channel (NPRACH). The method may include determining inter-symbol correlation information for at least one of the plurality of symbol groups. The method may include determining a frequency offset based on the inter-symbol correlation information. The method may include obtaining a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier.

[0212] According to an embodiment, one symbol group in the plurality of symbol groups may include five symbols. The plurality of symbol groups may include four symbol groups corresponding to a preamble and a symbol group corresponding to a repetition of the four symbol groups. Information regarding the number of repetitions of the four symbol groups within the plurality of symbol groups may be configured to a user equipment (UE) for NPRACH transmission.

[0213] According to an embodiment, determining the inter-symbol correlation information may include obtaining first correlation information between adjacent symbols of each symbol group. Determining the inter-symbol correlation information may include obtaining second correlation information between symbols separated by one symbol of each symbol group. Determining the inter-symbol correlation information may include obtaining third correlation information between symbols separated by two symbols of each symbol group. Determining the inter-symbol correlation information may include obtaining fourth correlation information between symbols separated by three symbols of each symbol group.

[0214] According to an embodiment, determining the frequency offset may include obtaining a first cumulative correlation value based on a sum of values of first correlation information between adjacent symbols of a plurality of symbol groups. Determining the frequency offset may include obtaining a second cumulative correlation value based on a sum of values of second correlation information between symbols of the plurality of symbol groups spaced apart by two symbols. Determining the frequency offset may include obtaining a third cumulative correlation value based on a sum of values of third correlation information between symbols of the plurality of symbol groups spaced apart by three symbols. Determining the frequency offset may include obtaining a fourth cumulative correlation value based on a sum of values of fourth correlation information between symbols of the plurality of symbol groups spaced apart by four symbols. Determining the frequency offset may include obtaining a total correlation value based on the first cumulative correlation value, the second cumulative correlation value, the third cumulative correlation value, and the fourth cumulative correlation value.

[0215] According to an embodiment, determining the frequency offset may include obtaining angle information of the total correlation value. Determining the frequency offset may include determining the frequency offset by performing scaling on the angle information. The scaling may be determined based on the number of correlation calculations corresponding to different symbol lengths in the inter-symbol correlation information.

[0216] According to an embodiment, a first scaling value of 1 / 4 of the sum of the first correlation information values may be applied to the first cumulative correlation value. A second scaling value of 1 / 3 of the sum of the second correlation information values may be applied to the second cumulative correlation value. A third scaling value of 1 / 2 of the sum of the third correlation information values may be applied to the third cumulative correlation value.

[0217] According to an embodiment, the plurality of symbol groups may correspond to repetitions according to a number of repetitions configured for NPRACH transmission. The at least one symbol group may correspond to a subset of the repetitions.

[0218] According to an embodiment, the plurality of symbol groups may correspond to repetitions according to a number of repetitions configured for the NPRACH transmission. The at least one symbol group may correspond to a subset of four symbol groups for each of the repetitions.

[0219] According to an embodiment, obtaining the random access signal may include obtaining a compensation signal based on the signal and the frequency offset. Obtaining the random access signal may include identifying a sequence among a plurality of sequences having a peak value greater than or equal to a threshold value in a correlation calculation with the compensation signal. The sequence may correspond to the random access signal.

[0220] According to an embodiment, the device may include a distributed unit (DU). A frequency offset may be determined for each antenna connected to a radio unit (RU) of the device. A signal may be obtained from the RU.

[0221] In an embodiment, a base station device is provided. The device may include a memory, at least one transceiver, and at least one processor coupled to the memory and the at least one transceiver. The at least one processor may be configured to obtain a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH). The at least one processor may be configured to determine inter-symbol correlation information for at least one of the plurality of symbol groups. The at least one processor may be configured to determine a frequency offset based on the inter-symbol correlation information. The at least one processor may be configured to obtain a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier.

[0222] According to an embodiment, one symbol group in the plurality of symbol groups may include five symbols. The plurality of symbol groups may include four symbol groups corresponding to a preamble and a symbol group corresponding to a repetition of the four symbol groups. Information regarding the number of repetitions of the four symbol groups within the plurality of symbol groups may be configured to a user equipment (UE) for NPRACH transmission.

[0223] According to an embodiment, the at least one processor may be configured to obtain first correlation information between adjacent symbols of each symbol group to determine inter-symbol correlation information. The at least one processor may be configured to obtain second correlation information between symbols separated by one symbol of each symbol group to determine the inter-symbol correlation information. The at least one processor may be configured to obtain third correlation information between symbols separated by two symbols of each symbol group to determine the inter-symbol correlation information. The at least one processor may be configured to obtain fourth correlation information between symbols separated by three symbols of each symbol group to determine the inter-symbol correlation information.

[0224] According to an embodiment, the at least one processor may be configured to obtain a first cumulative correlation value based on the sum of values of first correlation information between adjacent symbols of the plurality of symbol groups to determine the frequency offset. The at least one processor may be configured to obtain a second cumulative correlation value based on the sum of values of second correlation information between symbols of the plurality of symbol groups spaced apart by two symbols to determine the frequency offset. The at least one processor may be configured to obtain a third cumulative correlation value based on the sum of values of third correlation information between symbols of the plurality of symbol groups spaced apart by three symbols to determine the frequency offset. The at least one processor may be configured to obtain a fourth cumulative correlation value based on the sum of values of fourth correlation information between symbols of the plurality of symbol groups spaced apart by four symbols to determine the frequency offset. The at least one processor may be configured to obtain a total correlation value based on the first cumulative correlation value, the second cumulative correlation value, the third cumulative correlation value, and the fourth cumulative correlation value to determine the frequency offset.

[0225] According to an embodiment, the at least one processor may be configured to obtain angle information of the total correlation value to determine the frequency offset. The at least one processor may be configured to determine the frequency offset by performing scaling on the angle information to determine the frequency offset. The scaling may be determined based on the number of correlation calculations corresponding to different symbol lengths in the inter-symbol correlation information.

[0226] According to an embodiment, a first scaling value of 1 / 4 of the sum of the first correlation information values may be applied to the first cumulative correlation value. A second scaling value of 1 / 3 of the sum of the second correlation information values may be applied to the second cumulative correlation value. A third scaling value of 1 / 2 of the sum of the third correlation information values may be applied to the third cumulative correlation value.

[0227] According to an embodiment, the plurality of symbol groups may correspond to repetitions according to a number of repetitions configured for NPRACH transmission. The at least one symbol group may correspond to a subset of the repetitions.

[0228] According to an embodiment, the plurality of symbol groups may correspond to repetitions according to a number of repetitions configured for the NPRACH transmission. The at least one symbol group may correspond to a subset of four symbol groups for each of the repetitions.

[0229] According to an embodiment, at least one processor may be configured to obtain a compensation signal based on a signal and a frequency offset to obtain a random access signal. The at least one processor may be configured to identify a sequence from a plurality of sequences having a peak value greater than or equal to a threshold value in a correlation calculation with the compensation signal to obtain the random access signal. The sequence may correspond to the random access signal.

[0230] According to an embodiment, the device may include a distributed unit (DU). A frequency offset may be determined for each antenna connected to a radio unit (RU) of the device. A signal may be obtained from the RU.

[0231] In an embodiment, a digital unit (DU) is provided. The DU may include a memory storing instructions, at least one transceiver, and at least one processor. When executed by the at least one processor, the instructions may cause the DU to obtain a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH), determine inter-symbol correlation information for at least one symbol group in the plurality of symbol groups, determine a frequency offset based on the inter-symbol correlation information, and obtain a random access signal corresponding to the signal based on the frequency offset, wherein symbols in each symbol group in the plurality of symbol groups may correspond to the same subcarrier.

[0232] According to an embodiment, when the instruction is executed by at least one processor, in order to determine the inter-symbol correlation information, the DU can obtain first correlation information between adjacent symbols of each symbol group, obtain second correlation information between symbols separated by one symbol of each symbol group, obtain third correlation information between symbols separated by two symbols of each symbol group, and obtain fourth correlation information between symbols separated by three symbols of each symbol group.

[0233] According to an embodiment, when the instruction is executed by at least one processor, in order to determine the frequency offset, the DU may obtain a first cumulative correlation value based on the sum of the values of the first correlation information between adjacent symbols of multiple symbol groups, obtain a second cumulative correlation value based on the sum of the values of the second correlation information between symbols of multiple symbol groups separated by two symbols, obtain a third cumulative correlation value based on the sum of the values of the third correlation information between symbols of multiple symbol groups separated by three symbols, obtain a fourth cumulative correlation value based on the sum of the values of the fourth correlation information between symbols of multiple symbol groups separated by four symbols, and obtain a total correlation value based on the first cumulative correlation value, the second cumulative correlation value, the third cumulative correlation value and the fourth cumulative correlation value.

[0234] According to an embodiment, when the instruction is executed by at least one processor, in order to determine the frequency offset, the DU can obtain angle information of the total correlation value and determine the frequency offset by performing scaling on the angle information, wherein the scaling can be determined based on the number of correlation calculations corresponding to different symbol lengths in the inter-symbol correlation information.

[0235] According to an embodiment, when the instructions are executed by the at least one processor, in order to obtain the random access signal, the DU may obtain a compensation signal based on the signal and the frequency offset, and identify a sequence having a peak value greater than or equal to a threshold in a correlation calculation with the compensation signal from a plurality of sequences, wherein the sequence may correspond to the random access signal.

[0236] In an embodiment, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium may store instructions that, when executed by a processor of a digital unit (DU), cause the DU to perform operations including obtaining a signal corresponding to a plurality of symbol groups transmitted on a narrowband random access channel (NPRACH), determining inter-symbol correlation information for at least one of the plurality of symbol groups, determining a frequency offset based on the inter-symbol correlation information, and obtaining a random access signal corresponding to the signal based on the frequency offset. Symbols within each of the plurality of symbol groups may correspond to the same subcarrier.

[0237] The electronic device according to various embodiments may be any of various types of electronic devices. The electronic device may include, for example, a portable communication device (e.g., a smartphone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, or a household appliance. According to embodiments of the present disclosure, the electronic device is not limited to the aforementioned electronic devices.

[0238] It should be understood that the various embodiments of the present disclosure and the terms used therein are not intended to limit the technical features set forth herein to specific embodiments, and include various changes, equivalents, or replacements of the corresponding embodiments. With respect to the description of the drawings, similar figure numerals may be used to refer to similar or related elements. It should be understood that, unless otherwise clearly indicated by the relevant context, the singular form of the noun corresponding to an item may include one or more things. As used herein, each of phrases such as "A or B," "at least one of A and B," "at least one of A or B," "A, B or C," "at least one of A, B and C," and "at least one of A, B or C" may include any one or all possible combinations of the items listed together in the corresponding phrase in the phrase. As used herein, terms such as "first" and "second" or "first" and "second" may be used to simply distinguish a corresponding component from another component and do not limit the component in other respects (e.g., importance or order). It should be understood that if an element (e.g., a first element) is referred to as being “coupled” or “connected” to another element (e.g., a second element) with or without the term “operably” or “communicatively”, it means that the element can be coupled to the other element directly (e.g., wired), wirelessly, or via a third element.

[0239] As used in conjunction with various embodiments of the present disclosure, the term "module" may include a unit implemented in hardware, software, or firmware, and may be used interchangeably with other terms (e.g., "logic," "logic block," "portion," or "circuit"). A module may be a single integrated component adapted to perform one or more functions, or its smallest unit or portion. For example, depending on the embodiment, a module may be implemented in the form of an application-specific integrated circuit (ASIC).

[0240] The various embodiments as described herein may be implemented as software comprising one or more instructions stored in a machine-readable storage medium. For example, a processor of a machine may call at least one of the one or more instructions stored in the storage medium and execute it with or without one or more other components under the control of the processor. This allows the machine to be operated to perform at least one function according to the at least one instruction called. The one or more instructions may include code generated by a compiler or code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. The term "non-transitory" simply means that the storage medium is a tangible device and does not include signals (e.g., electromagnetic waves), but the term does not distinguish between situations where data is semi-permanently stored in the storage medium and situations where data is temporarily stored in the storage medium.

[0241] The methods according to the embodiments described in the claims or the specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0242] When implemented as software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to perform the methods according to the embodiments described in the claims or the specification of this disclosure. The one or more programs may be included and provided in a computer program product. The computer program product can be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., a compact disk read-only memory (CD-ROM)), distributed online (e.g., by downloading or uploading) via an app store (e.g., PlayStore™), or distributed directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product may be temporarily generated or at least temporarily stored in a machine-readable storage medium, such as in the memory of a manufacturer's server, an app store's server, or a relay server.

[0243] Such a program (software module, software) may be stored in random access memory, non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk storage, compact disk-ROM (CD-ROM), optical storage (digital versatile disk (DVD) or other formats), or magnetic tape cassettes. Alternatively, it may be stored in a memory configured with a combination of some or all of these. Furthermore, multiple configuration memories may be included.

[0244] In addition, the program may be stored in an attachable storage device that can be accessed via a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. Such a storage device can be connected to the device performing the embodiments of the present disclosure via an external port. In addition, a separate storage device on the communication network can also be connected to the device performing the embodiments of the present disclosure.

[0245] In the above-mentioned specific embodiments of the present disclosure, the components included in the present disclosure are expressed in the singular or plural according to the specific embodiment presented. However, the singular or plural expression is appropriately selected according to the situation presented for the convenience of explanation, and the present disclosure is not limited to singular or plural components, and even components expressed in the plural may be configured in the singular, or components expressed in the singular may be configured in the plural.

[0246] According to various embodiments, one or more components or operations of the above-described components may be omitted, or one or more additional components or operations may be added. Alternatively or additionally, multiple components (e.g., modules or programs) may be integrated into a single component. In this case, the integrated component can still perform one or more functions of each of the multiple components in the same or similar manner as performed by the corresponding one of the multiple components before integration. According to various embodiments, the operations performed by a module, program, or another component may be performed sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations may be performed in a different order or omitted, or one or more additional operations may be added.

[0247] While specific embodiments have been described in the detailed description of the present disclosure, various modifications are possible without departing from the scope of the present disclosure.

Claims

1. A digital unit DU, comprising: Memory, which stores instructions; at least one transceiver; at least one processor; wherein the instructions, when executed by the at least one processor, cause the DU to: Obtaining signals corresponding to a plurality of symbol groups transmitted by a narrowband random access channel NPRACH; determining inter-symbol correlation information for at least one symbol group among the plurality of symbol groups; determining a frequency offset based on the inter-symbol correlation information; and obtaining a random access signal corresponding to the signal based on the frequency offset; The symbols in each symbol group of the multiple symbol groups correspond to the same subcarrier.

2. The DU according to claim 1, in, One of the plurality of symbol groups comprises five symbols, The plurality of symbol groups include four symbol groups corresponding to the preamble and repeated symbol groups corresponding to the four symbol groups, and Information about the number of repetitions of the four symbol groups within the multiple symbol groups is configured to a user equipment UE for the NPRACH transmission.

3. The DU according to claim 1, in, When executed by the at least one processor, the instructions cause the DU to determine the inter-symbol correlation information by: obtaining first correlation information between adjacent symbols of each symbol group; obtaining second correlation information between symbols separated by one symbol in each symbol group; obtaining third correlation information between symbols separated by two symbols in each symbol group; and Fourth correlation information between symbols spaced apart by three symbols for each symbol group is obtained.

4. The DU according to claim 3, in, When executed by the at least one processor, the instructions cause the DU to determine the frequency offset by: obtaining a first cumulative correlation value based on a sum of values of the first correlation information between adjacent symbols of the plurality of symbol groups; obtaining a second cumulative correlation value based on a sum of values of second correlation information between symbols of the plurality of symbol groups spaced apart by two symbols; obtaining a third cumulative correlation value based on a sum of values of third correlation information between symbols of the plurality of symbol groups spaced apart by three symbols; obtaining a fourth cumulative correlation value based on a sum of values of fourth correlation information between symbols of the plurality of symbol groups spaced apart by four symbols; and A total correlation value is obtained based on the first cumulative correlation value, the second cumulative correlation value, the third cumulative correlation value, and the fourth cumulative correlation value.

5. The DU according to claim 4, in, When executed by the at least one processor, the instructions cause the DU to determine the frequency offset by: Obtaining angle information of the total correlation value; and determining the frequency offset by performing scaling on the angle information; The scaling is determined based on the number of correlation calculations corresponding to different symbol lengths in the inter-symbol correlation information.

6. The DU according to claim 4, in, a first scaling factor of 1 / 4 of the sum of the first correlation information values is applied to the first cumulative correlation value, wherein a second scaling factor of 1 / 3 of the sum of the second correlation information values is applied to the second cumulative correlation value, Therein, a third scaling factor of 1 / 2 of the sum of the third correlation information values is applied to the third cumulative correlation value.

7. The DU according to claim 1, in, The plurality of symbol groups corresponds to repetitions according to a number of repetitions configured for the NPRACH transmission, and Wherein, the at least one symbol group corresponds to a subset in the repetition.

8. The DU according to claim 1, in, The plurality of symbol groups corresponds to repetitions according to a number of repetitions configured for the NPRACH transmission, and Wherein, the at least one symbol group corresponds to a subset of four symbol groups of each of the repetitions.

9. The DU according to claim 1, in, When executed by the at least one processor, the instructions cause the DU to obtain the random access signal by: obtaining a compensation signal based on the signal and the frequency offset; and identifying, from a plurality of sequences, a sequence having a peak value greater than or equal to a threshold value in a correlation calculation with the compensation signal; and The sequence corresponds to the random access signal.

10. The DU according to claim 1, in, The frequency offset is determined for each antenna of a radio unit (RU) connected to the device, Wherein, the signal is obtained from the RU.

11. A method performed by a digital unit DU, the method comprising: Obtaining signals corresponding to a plurality of symbol groups transmitted by a narrowband random access channel NPRACH; determining inter-symbol correlation information for at least one symbol group among the plurality of symbol groups; determining a frequency offset based on the inter-symbol correlation information; and obtaining a random access signal corresponding to the signal based on the frequency offset; and The symbols in each symbol group of the multiple symbol groups correspond to the same subcarrier.

12. The method according to claim 11, in, One of the plurality of symbol groups comprises five symbols, wherein the plurality of symbol groups include four symbol groups corresponding to the preamble and a symbol group corresponding to a repetition of the four symbol groups, and Information about the number of repetitions of the four symbol groups within the multiple symbol groups is configured to a user equipment UE for the NPRACH transmission.

13. The method according to claim 11, in, Determining the inter-symbol correlation information includes: obtaining first correlation information between adjacent symbols of each symbol group; obtaining second correlation information between symbols separated by one symbol in each symbol group; obtaining third correlation information between symbols separated by two symbols in each symbol group; and Fourth correlation information between symbols spaced apart by three symbols for each symbol group is obtained.

14. The method according to claim 13, in, Determining the frequency offset includes: obtaining a first cumulative correlation value based on a sum of values of the first correlation information between adjacent symbols of the plurality of symbol groups; obtaining a second cumulative correlation value based on a sum of values of second correlation information between symbols of the plurality of symbol groups spaced apart by two symbols; obtaining a third cumulative correlation value based on a sum of values of third correlation information between symbols of the plurality of symbol groups spaced apart by three symbols; obtaining a fourth cumulative correlation value based on a sum of values of fourth correlation information between symbols of the plurality of symbol groups spaced apart by four symbols; and A total correlation value is obtained based on the first cumulative correlation value, the second cumulative correlation value, the third cumulative correlation value, and the fourth cumulative correlation value.

15. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor of a digital unit (DU), cause the DU to perform operations comprising: Obtaining signals corresponding to a plurality of symbol groups transmitted by a narrowband random access channel NPRACH; determining inter-symbol correlation information for at least one symbol group among the plurality of symbol groups; determining a frequency offset based on the inter-symbol correlation information; and obtaining a random access signal corresponding to the signal based on the frequency offset; The symbols in each symbol group of the multiple symbol groups correspond to the same subcarrier.

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