WO2024237365A1 - Initial access method and apparatus in wireless communication system - Google Patents

Abstract

According to various embodiments of the present disclosure, a method performed by a user equipment in a wireless communication system includes the steps of: receiving first reference signals from a plurality of devices; selecting a first device from among the plurality of devices by measuring the first reference signals; acquiring a synchronization signal block (SSB) on the basis of the first reference signal received from the first device, from among the first reference signals; acquiring information about pre-scheduled resources on the basis of the SSB; selecting second devices from among the plurality of devices on the basis of the information about the pre-scheduled resources; and transmitting, to the first device, information about the second devices.

Description

Initial connection method and device in wireless communication system

The present disclosure relates to a wireless communication system. Specifically, the present disclosure relates to an initial connection method and device in a wireless communication system.

Wireless access systems are being widely deployed to provide various types of communication services such as voice and data. In general, wireless access systems are multiple access systems that can support communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include CDMA (code division multiple access) systems, FDMA (frequency division multiple access) systems, TDMA (time division multiple access) systems, OFDMA (orthogonal frequency division multiple access) systems, and SC-FDMA (single carrier frequency division multiple access) systems.

In particular, as many communication devices require large communication capacity, enhanced mobile broadband (eMBB) communication technology is being proposed compared to the existing radio access technology (RAT). In addition, a communication system that considers reliability and latency-sensitive services/UE (user equipment) as well as mMTC (massive machine type communications) that connects a large number of devices and objects to provide various services anytime and anywhere is being proposed. Various technology configurations are being proposed for this.

In order to solve the above-described problem, the present disclosure provides an initial connection method and device for determining the approximate location of a terminal without the aid of a Global Positioning System (GPS) in a D-MIMO (Distributed massive Multiple Input Multiple Output) system and limiting the range of a beam that each AP must transmit for beam alignment between the terminal and the AP.

To address the above-described problems, the present disclosure proposes a method for signaling the number of resources to be measured without affecting existing terminals.

According to one embodiment of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system, wherein the UE operates in the wireless communication system, may include: receiving first reference signals from a plurality of devices; selecting a first device among the plurality of devices by performing measurement on the first reference signals; obtaining a Synchronization Signal Block (SSB) based on the first reference signal received from the first device among the first reference signals; obtaining information about pre-scheduled resources based on the SSB; selecting second devices among the plurality of devices based on the information about the pre-scheduled resources; and transmitting information about the second devices to the first device.

The step of obtaining information about the pre-scheduled resources based on the SSB may include the steps of obtaining a primary synchronization signal (PSS), a secondary synchronization signal (SSS) and a physical broadcast channel (PBCH) from the SSB, obtaining a phase difference value between the PSS and the SSS, obtaining a phase modulation value of the PBCH based on the phase difference value, and obtaining information about the number of the pre-scheduled resources based on the phase modulation value.

The step of obtaining information about the pre-scheduled resources based on the SSB may include the steps of obtaining a primary synchronization signal (PSS), a secondary synchronization signal (SSS) and a first physical broadcast channel (PBCH) and a second PBCH from the SSB, the step of obtaining a phase difference value of a demodulation reference signal (DMRS) of the first PBCH and a DMRS of the second PBCH, and the step of obtaining information about the number of the pre-scheduled resources based on the phase difference value.

The step of selecting the second devices among the plurality of devices based on the information about the pre-scheduled resources may include the steps of receiving a second reference signal from the plurality of devices through the pre-scheduled resources, performing a measurement about the second reference signals, and selecting the second devices among the plurality of devices based on a result of performing the measurement about the second reference signals.

The step of transmitting information about the second devices to the first device may include the steps of transmitting a random access request message to the first device, receiving a random access response message from the first device, and transmitting Msg3 including information about the second devices to the first device.

According to one embodiment of the present disclosure, a user equipment (UE) operating in a wireless communication system may include one or more transceivers, one or more processors controlling the one or more transceivers, and a memory including one or more instructions to be executed by the one or more processors, wherein the one or more instructions may include: receiving a first reference signal from a plurality of devices; selecting a first device among the plurality of devices by performing a measurement on the first reference signals; obtaining a Synchronization Signal Block (SSB) based on the first reference signal received from the first device among the first reference signals; obtaining information about pre-scheduled resources based on the SSB; selecting second devices among the plurality of devices based on the information about the pre-scheduled resources; and transmitting information about the second devices to the first device.

A method of operating a first device in a wireless communication system according to one embodiment of the present disclosure may include the steps of transmitting a reference signal to a user equipment (UE) in a first band, receiving information about second devices from the UE in the first band, obtaining location information of the UE based on a location of the first device and locations of the second devices, determining third devices and a beam sweep range of the third devices based on the location information of the UE, and transmitting a beam sweep request message including information about the beam sweep range to the third devices.

The above reference signal may include a Synchronization Signal Block (SSB) composed of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), and a Physical Broadcast Channel (PBCH), and the SSS may be phase modulated.

The above reference signal includes a Synchronization Signal Block (SSB) composed of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a First Physical Broadcast Channel (PBCH), and a Second PBCH, and a phase difference between a Demodulation Reference Signal (DMRS) of the First PBCH and a DMRS of the Second PBCH may be related to a phase modulation value of the First PBCH or the Second PBCH.

The step of receiving information about the second devices from the terminal in the first band may include the step of receiving a random access request message from the terminal in the first band, the step of transmitting a random access response message to the terminal in the first band, and the step of receiving, from the terminal in the first band, Msg3 including information about the second devices.

If the first device is included in the third devices, the step of transmitting the beam sweep request message including information about the beam sweep range to the third devices may include the step of transmitting the beam sweep request message including information about the beam sweep range to the remaining third devices among the third devices excluding the first device, and the step of performing a beam sweep in the second band based on the determined beam sweep range.

The first band may include a B6G (Below ^6th generation, Below 6G) band, and the second band may include at least one of a mmWave band or a THz (TeraHertz) band.

The step of transmitting the beam sweep request message including information about the beam sweep range to the third devices may include the step of transmitting the beam sweep request message to the third devices via an Xn interface.

In accordance with one embodiment of the present disclosure, a first device operating in a wireless communication system includes one or more transceivers, one or more processors controlling the one or more transceivers, and a memory including one or more instructions to be executed by the one or more processors, wherein the one or more instructions may include: transmitting a reference signal to a user equipment (UE) in a first band; receiving information about second devices from the UE in the first band; acquiring location information of the UE based on a location of the first device and locations of the second devices; determining third devices and a beam sweep range of the third devices based on the location information of the UE; and transmitting a beam sweep request message including information about the beam sweep range to the third devices.

According to one embodiment of the present disclosure, a first node including one or more memories and one or more processors functionally connected to the one or more memories, wherein the one or more processors are operable to cause the first node to receive first reference signals from a plurality of devices, perform measurements on the first reference signals to select a first device among the plurality of devices, obtain a Synchronization Signal Block (SSB) based on the first reference signal received from the first device among the first reference signals, obtain information about pre-scheduled resources based on the SSB, select second devices among the plurality of devices based on the information about the pre-scheduled resources, and transmit the information about the second devices to the first device.

One or more non-transitory computer-readable media storing one or more commands according to one embodiment of the present disclosure, the instructions being operable to: receive first reference signals from a plurality of devices, perform measurements on the first reference signals to select a first device among the plurality of devices, obtain a Synchronization Signal Block (SSB) based on the first reference signal received from the first device among the first reference signals, obtain information about pre-scheduled resources based on the SSB, select second devices among the plurality of devices based on the information about the pre-scheduled resources, and transmit information about the second devices to the first device.

According to the present disclosure, in the initial access stage of a mmWave/THz D-MIMO system, the initial access delay and system overhead can be reduced by identifying the approximate location of the terminal, selecting a candidate AP to serve the terminal, and limiting the beam sweep range of each AP.

According to the present disclosure, the number of measurement resources of a D-MIMO system can be signaled without affecting existing terminals by performing signaling by performing phase modulation on a synchronization signal block (SSB).

The drawings attached below are intended to aid in understanding the present disclosure and may provide embodiments of the present disclosure together with detailed descriptions. However, the technical features of the present disclosure are not limited to specific drawings, and the features disclosed in each drawing may be combined with each other to form a new embodiment. Reference numerals in each drawing may mean structural elements.

Figure 1 is a drawing showing an example of a communication system applicable to this specification.

FIG. 2 is a drawing showing an example of a wireless device applicable to this specification.

FIG. 3 is a diagram illustrating a method for processing a transmission signal applicable to the present specification.

FIG. 4 is a drawing showing another example of a wireless device applicable to this specification.

FIG. 5 is a drawing showing an example of a portable device applicable to this specification.

Figure 6 is a diagram showing physical channels applicable to this specification and a signal transmission method using them.

Figure 7 is a diagram showing the structure of a wireless frame applicable to this specification.

Figure 8 is a drawing showing a slot structure applicable to this specification.

FIG. 9 is a diagram showing an example of a communication structure that can be provided in a 6G system applicable to this specification.

Figure 10 shows an example of a perceptron structure.

Figure 11 shows an example of a multilayer perceptron structure.

Figure 12 shows an example of a deep neural network.

Figure 13 shows an example of a convolutional neural network.

Figure 14 is a diagram showing an example of a filter operation in a convolutional neural network.

Figure 15 shows an example of a neural network structure in which a recurrent loop exists.

Figure 16 shows an example of the operational structure of a recurrent neural network.

Figure 17 is a diagram showing an electromagnetic spectrum applicable to this specification.

Fig. 18 is a diagram showing a THz communication method applicable to this specification.

FIG. 19 is a diagram illustrating a THz wireless communication transceiver applicable to the present specification.

FIG. 20 is a diagram illustrating a THz signal generation method applicable to the present specification.

FIG. 21 is a diagram illustrating a wireless communication transceiver applicable to this specification.

Figure 22 is a drawing showing a transmitter structure applicable to this specification.

Figure 23 is a drawing showing a modulator structure applicable to this specification.

FIG. 24 is a diagram illustrating an example of a D-MIMO system applicable to the present disclosure.

FIG. 25 is a diagram illustrating an example of a frame structure in a D-MIMO system applicable to the present disclosure.

FIG. 26 is a diagram illustrating an example of terminal-centric AP clustering applicable to the present disclosure.

FIG. 27 is a diagram illustrating an example of initial connection in a D-MIMO system applicable to the present disclosure.

FIG. 28 is a diagram illustrating an example of an initial connection method according to one embodiment of the present disclosure.

FIG. 29 is a diagram illustrating an example of pre-scheduled resources according to one embodiment of the present disclosure.

FIG. 30 is a flowchart of a beam search method according to one embodiment of the present disclosure.

FIG. 31 is a flowchart of a beam search method according to another embodiment of the present disclosure.

FIG. 32 is a flowchart of a beam search method according to another embodiment of the present disclosure.

FIG. 33 is a diagram illustrating an example of a signaling method according to one embodiment of the present disclosure.

FIG. 34 is a diagram illustrating an example of a signaling method according to another embodiment of the present disclosure.

FIG. 35 is a flowchart of a beam search method according to one embodiment of the present disclosure.

FIG. 36 is a flowchart of a beam search method according to another embodiment of the present disclosure.

The following embodiments combine the components and features of the present specification in a predetermined form. Each component or feature may be considered optional unless otherwise explicitly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some components and/or features may be combined to form an embodiment of the present specification. The order of operations described in the embodiments of the present specification may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment.

In the description of the drawings, procedures or steps that may obscure the gist of the present specification are not described, and procedures or steps that can be understood by those skilled in the art are also not described.

Throughout the specification, when a part is said to "comprising" (or including) a certain component, this does not mean that other components are excluded, but rather that other components can be included, unless otherwise specifically stated. In addition, terms such as "part," "unit," "module," etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software. In addition, "a" or "an," "one," "the," and similar related words may be used in the context of describing this specification (especially in the context of the claims below) to include both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context.

The embodiments of this specification have been described with a focus on the data transmission and reception relationship between a base station and a mobile station. Here, the base station is meant as a terminal node of a network that directly communicates with a mobile station. A specific operation described as being performed by the base station in this specification may in some cases be performed by an upper node of the base station.

That is, in a network consisting of a plurality of network nodes including a base station, various operations performed for communication with a mobile station may be performed by the base station or other network nodes other than the base station. In this case, the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), a gNode B (gNB), an ng-eNB, an advanced base station (ABS), or an access point.

Additionally, in the embodiments of the present specification, the term terminal may be replaced with terms such as user equipment (UE), mobile station (MS), subscriber station (SS), mobile subscriber station (MSS), mobile terminal, or advanced mobile station (AMS).

In addition, the transmitter refers to a fixed and/or mobile node that provides data service or voice service, and the receiver refers to a fixed and/or mobile node that receives data service or voice service. Accordingly, in the case of uplink, a mobile station can be a transmitter and a base station can be a receiver. Similarly, in the case of downlink, a mobile station can be a receiver and a base station can be a transmitter.

Embodiments of the present specification may be supported by standard documents disclosed in at least one of wireless access systems, namely IEEE 802.xx system, 3rd Generation Partnership Project (3GPP) system, 3GPP Long Term Evolution (LTE) system, 3GPP 5G (5th generation) NR (New Radio) system and 3GPP2 system, and in particular, embodiments of the present specification may be supported by 3GPP TS (technical specification) 38.211, 3GPP TS 38.212, 3GPP TS 38.213, 3GPP TS 38.321 and 3GPP TS 38.331 documents.

In addition, the embodiments of the present specification may be applied to other wireless access systems and are not limited to the above-described system. For example, they may be applied to systems applied after the 3GPP 5G NR system and are not limited to a specific system.

That is, obvious steps or parts that are not described in the embodiments of this specification can be described by referring to the above documents. In addition, all terms disclosed in this specification can be described by the above standard documents.

Hereinafter, preferred embodiments according to the present specification will be described in detail with reference to the accompanying drawings. The detailed description set forth below together with the accompanying drawings is intended to explain exemplary embodiments of the present specification and is not intended to represent the only embodiments in which the technical configuration of the present specification may be implemented.

In addition, specific terms used in the embodiments of this specification are provided to help understanding of this specification, and the use of such specific terms may be changed to other forms without departing from the technical spirit of this specification.

The following technology can be applied to various wireless access systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access).

In the following, for the purpose of clarity, the description is based on a 3GPP communication system (e.g., LTE, NR, etc.), but the technical spirit of the present invention is not limited thereto. LTE may refer to technology after 3GPP TS 36.xxx Release 8. Specifically, LTE technology after 3GPP TS 36.xxx Release 10 may be referred to as LTE-A, and LTE technology after 3GPP TS 36.xxx Release 13 may be referred to as LTE-A pro. 3GPP NR may refer to technology after TS 38.xxx Release 15. 3GPP 6G may refer to technology after TS Release 17 and/or Release 18. “xxx” refers to a standard document detail number. LTE/NR/6G may be collectively referred to as a 3GPP system.

For background information, terms, abbreviations, etc. used in this specification, reference may be made to standard documents published prior to the invention of the present invention. For example, reference may be made to standard documents 36.xxx and 38.xxx.

Communication systems applicable to this specification

Although not limited thereto, the various descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein may be applied to various fields requiring wireless communication/connectivity (e.g., 5G) between devices.

Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings/descriptions below, the same drawing symbols may illustrate identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

FIG. 1 is a diagram illustrating an example of a communication system applied to the present specification. Referring to FIG. 1, a communication system (100) applied to the present specification includes a wireless device, a base station, and a network. Here, the wireless device means a device that performs communication using a wireless access technology (e.g., 5G NR, LTE) and may be referred to as a communication/wireless/5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (extended reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Thing) device (100f), and an AI (artificial intelligence) device/server (100g). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicles (100b-1, 100b-2) may include unmanned aerial vehicles (UAVs) (e.g., drones). The XR devices (100c) include augmented reality (AR)/virtual reality (VR)/mixed reality (MR) devices, and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) equipped in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance, digital signage, a vehicle, a robot, etc. The portable devices (100d) may include a smartphone, a smart pad, a wearable device (e.g., a smart watch, smart glasses), a computer (e.g., a laptop, etc.), etc. The home appliances (100e) may include a TV, a refrigerator, a washing machine, etc. The IoT devices (100f) may include sensors, smart meters, etc. For example, the base station (120) and network (130) may also be implemented as wireless devices, and a specific wireless device (120a) may act as a base station/network node to other wireless devices.

Wireless devices (100a to 100f) can be connected to a network (130) via a base station (120). AI technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (100g) via a network (130). The network (130) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (120)/network (130), but can also communicate directly (e.g., sidelink communication) without going through the base station (120)/network (130). For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (vehicle to vehicle)/V2X (vehicle to everything) communication). Additionally, an IoT device (100f) (e.g., a sensor) can communicate directly with another IoT device (e.g., a sensor) or another wireless device (100a to 100f).

Wireless communication/connection (150a, 150b, 150c) can be established between wireless devices (100a to 100f)/base stations (120), and base stations (120)/base stations (120). Here, the wireless communication/connection can be established through various wireless access technologies (e.g., 5G NR) such as uplink/downlink communication (150a), sidelink communication (150b) (or, D2D communication), and communication between base stations (150c) (e.g., relay, IAB (integrated access backhaul)). Through the wireless communication/connection (150a, 150b, 150c), the wireless device and base station/wireless device, and the base station and base station can transmit/receive wireless signals to each other. For example, the wireless communication/connection (150a, 150b, 150c) can transmit/receive signals through various physical channels. To this end, at least some of the various configuration information setting processes for transmitting/receiving wireless signals, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, resource mapping/demapping, etc.), and resource allocation processes may be performed based on various proposals of this specification.

Communication systems applicable to this specification

FIG. 2 is a drawing illustrating an example of a wireless device to which the present specification can be applied.

Referring to FIG. 2, the first wireless device (200a) and the second wireless device (200b) can transmit and receive wireless signals through various wireless access technologies (e.g., LTE, NR). Here, {the first wireless device (200a), the second wireless device (200b)} can correspond to {the wireless device (100x), the base station (120)} and/or {the wireless device (100x), the wireless device (100x)} of FIG. 1.

A first wireless device (200a) includes one or more processors (202a) and one or more memories (204a), and may additionally include one or more transceivers (206a) and/or one or more antennas (208a). The processor (202a) controls the memory (204a) and/or the transceiver (206a), and may be configured to implement the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein. For example, the processor (202a) may process information in the memory (204a) to generate first information/signal, and then transmit a wireless signal including the first information/signal via the transceiver (206a). In addition, the processor (202a) may receive a wireless signal including second information/signal via the transceiver (206a), and then store information obtained from signal processing of the second information/signal in the memory (204a). The memory (204a) may be connected to the processor (202a) and may store various information related to the operation of the processor (202a). For example, the memory (204a) may perform some or all of the processes controlled by the processor (202a), or may store software codes including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein. Here, the processor (202a) and the memory (204a) may be part of a communication modem/circuit/chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206a) may be connected to the processor (202a) and may transmit and/or receive wireless signals via one or more antennas (208a). The transceiver (206a) may include a transmitter and/or a receiver. The transceiver (206a) may be used interchangeably with an RF (radio frequency) unit. In this specification, wireless device may also mean a communication modem/circuit/chip.

The second wireless device (200b) includes one or more processors (202b), one or more memories (204b), and may additionally include one or more transceivers (206b) and/or one or more antennas (208b). The processor (202b) may control the memory (204b) and/or the transceiver (206b), and may be configured to implement the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein. For example, the processor (202b) may process information in the memory (204b) to generate third information/signal, and then transmit a wireless signal including the third information/signal via the transceiver (206b). In addition, the processor (202b) may receive a wireless signal including fourth information/signal via the transceiver (206b), and then store information obtained from signal processing of the fourth information/signal in the memory (204b). The memory (204b) may be connected to the processor (202b) and may store various information related to the operation of the processor (202b). For example, the memory (204b) may perform some or all of the processes controlled by the processor (202b), or may store software codes including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein. Here, the processor (202b) and the memory (204b) may be part of a communication modem/circuit/chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206b) may be connected to the processor (202b) and may transmit and/or receive wireless signals via one or more antennas (208b). The transceiver (206b) may include a transmitter and/or a receiver. The transceiver (206b) may be used interchangeably with an RF unit. In this specification, wireless device may also mean a communication modem/circuit/chip.

Hereinafter, hardware elements of the wireless device (200a, 200b) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (202a, 202b). For example, one or more processors (202a, 202b) may implement one or more layers (e.g., functional layers such as physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), radio resource control (RRC), service data adaptation protocol (SDAP)). One or more processors (202a, 202b) may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein. One or more processors (202a, 202b) may generate messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and/or operational flowcharts disclosed herein. One or more processors (202a, 202b) may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, functions, procedures, proposals and/or methods disclosed herein and provide the signals to one or more transceivers (206a, 206b). One or more processors (202a, 202b) may receive signals (e.g., baseband signals) from one or more transceivers (206a, 206b) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and/or operational flowcharts disclosed herein.

The one or more processors (202a, 202b) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The one or more processors (202a, 202b) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors (202a, 202b). The descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this specification may be implemented using firmware or software configured to perform one or more of the processors (202a, 202b), or may be stored in one or more memories (204a, 204b) and executed by one or more of the processors (202a, 202b). The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this specification may be implemented using firmware or software in the form of codes, instructions and/or sets of instructions.

One or more memories (204a, 204b) may be coupled to one or more processors (202a, 202b) and may store various forms of data, signals, messages, information, programs, codes, instructions, and/or commands. The one or more memories (204a, 204b) may be comprised of read only memory (ROM), random access memory (RAM), erasable programmable read only memory (EPROM), flash memory, hard drives, registers, cache memory, computer readable storage media, and/or combinations thereof. The one or more memories (204a, 204b) may be located internally and/or externally to the one or more processors (202a, 202b). Additionally, the one or more memories (204a, 204b) may be coupled to the one or more processors (202a, 202b) via various technologies, such as wired or wireless connections.

One or more transceivers (206a, 206b) can transmit user data, control information, wireless signals/channels, etc., as described in the methods and/or flowcharts of this specification, to one or more other devices. One or more transceivers (206a, 206b) can receive user data, control information, wireless signals/channels, etc., as described in the descriptions, functions, procedures, suggestions, methods and/or flowcharts of this specification, from one or more other devices. For example, one or more transceivers (206a, 206b) can be coupled to one or more processors (202a, 202b) and can transmit and receive wireless signals. For example, one or more processors (202a, 202b) can control one or more transceivers (206a, 206b) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (202a, 202b) may control one or more transceivers (206a, 206b) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (206a, 206b) may be coupled to one or more antennas (208a, 208b), and one or more transceivers (206a, 206b) may be configured to transmit and receive user data, control information, wireless signals/channels, and the like, as referred to in the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein, via one or more antennas (208a, 208b). In the present specification, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (206a, 206b) may convert received user data, control information, wireless signals/channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals/channels, etc. using one or more processors (202a, 202b). One or more transceivers (206a, 206b) may convert processed user data, control information, wireless signals/channels, etc. from baseband signals to RF band signals using one or more processors (202a, 202b). For this purpose, one or more transceivers (206a, 206b) may include an (analog) oscillator and/or filter.

FIG. 3 is a diagram illustrating a method for processing a transmission signal applied to the present specification. For example, the transmission signal may be processed by a signal processing circuit. At this time, the signal processing circuit (300) may include a scrambler (310), a modulator (320), a layer mapper (330), a precoder (340), a resource mapper (350), and a signal generator (360). At this time, as an example, the operation/function of FIG. 3 may be performed in the processor (202a, 202b) and/or the transceiver (206a, 206b) of FIG. 2. In addition, as an example, the hardware elements of FIG. 3 may be implemented in the processor (202a, 202b) and/or the transceiver (206a, 206b) of FIG. 2. For example, blocks 310 to 350 may be implemented in the processor (202a, 202b) of FIG. 2, and block 360 may be implemented in the transceiver (206a, 206b) of FIG. 2, and are not limited to the above-described embodiments.

The codeword can be converted into a wireless signal through the signal processing circuit (300) of FIG. 3. Here, the codeword is an encoded bit sequence of an information block. The information block can include a transport block (e.g., a UL-SCH transport block, a DL-SCH transport block). The wireless signal can be transmitted through various physical channels (e.g., a PUSCH, a PDSCH) of FIG. 6. Specifically, the codeword can be converted into a bit sequence scrambled by a scrambler (310). The scramble sequence used for scrambling is generated based on an initialization value, and the initialization value can include ID information of a wireless device, etc. The scrambled bit sequence can be modulated into a modulation symbol sequence by a modulator (320). The modulation scheme can include pi/2-BPSK (pi/2-binary phase shift keying), m-PSK (m-phase shift keying), m-QAM (m-quadrature amplitude modulation), etc.

The complex modulation symbol sequence can be mapped to one or more transmission layers by the layer mapper (330). The modulation symbols of each transmission layer can be mapped to the corresponding antenna port(s) by the precoder (340) (precoding). The output z of the precoder (340) can be obtained by multiplying the output y of the layer mapper (330) by a precoding matrix W of N*M. Here, N is the number of antenna ports, and M is the number of transmission layers. Here, the precoder (340) can perform precoding after performing transform precoding (e.g., DFT (discrete Fourier transform) transform) on the complex modulation symbols. In addition, the precoder (340) can perform precoding without performing transform precoding.

The resource mapper (350) can map modulation symbols of each antenna port to time-frequency resources. The time-frequency resources can include a plurality of symbols (e.g., CP-OFDMA symbols, DFT-s-OFDMA symbols) in the time domain and a plurality of subcarriers in the frequency domain. The signal generator (360) generates a wireless signal from the mapped modulation symbols, and the generated wireless signal can be transmitted to another device through each antenna. To this end, the signal generator (360) can include an inverse fast fourier transform (IFFT) module, a cyclic prefix (CP) inserter, a digital-to-analog converter (DAC), a frequency uplink converter, etc.

The signal processing process for receiving signals in a wireless device can be configured in reverse order of the signal processing process (310 to 360) of FIG. 3. For example, a wireless device (e.g., 200a and 200b of FIG. 2) can receive a wireless signal from the outside through an antenna port/transceiver. The received wireless signal can be converted into a baseband signal through a signal restorer. To this end, the signal restorer can include a frequency downlink converter, an analog-to-digital converter (ADC), a CP remover, and a fast Fourier transform (FFT) module. Thereafter, the baseband signal can be restored to a codeword through a resource demapper process, a postcoding process, a demodulation process, and a descramble process. The codeword can be restored to an original information block through decoding. Accordingly, a signal processing circuit (not shown) for a received signal may include a signal restorer, a resource de-mapper, a postcoder, a demodulator, a de-scrambler and a decoder.

Wireless device structure applicable to this specification

FIG. 4 is a drawing illustrating another example of a wireless device to which the present specification applies.

Referring to FIG. 4, the wireless device (400) corresponds to the wireless device (200a, 200b) of FIG. 2, and may be composed of various elements, components, units/units, and/or modules. For example, the wireless device (400) may include a communication unit (410), a control unit (420), a memory unit (430), and additional elements (440). The communication unit may include a communication circuit (412) and a transceiver(s) (414). For example, the communication circuit (412) may include one or more processors (202a, 202b) and/or one or more memories (204a, 204b) of FIG. 2. For example, the transceiver(s) (414) may include one or more transceivers (206a, 206b) and/or one or more antennas (208a, 208b) of FIG. 2. The control unit (420) is electrically connected to the communication unit (410), the memory unit (430), and the additional elements (440) and controls overall operations of the wireless device. For example, the control unit (420) may control electrical/mechanical operations of the wireless device based on programs/codes/commands/information stored in the memory unit (430). In addition, the control unit (420) may transmit information stored in the memory unit (430) to an external device (e.g., another communication device) via a wireless/wired interface through the communication unit (410), or store information received from an external device (e.g., another communication device) via a wireless/wired interface in the memory unit (430).

The additional element (440) may be configured in various ways depending on the type of the wireless device. For example, the additional element (440) may include at least one of a power unit/battery, an input/output unit, a driving unit, and a computing unit. Although not limited thereto, the wireless device (400) may be implemented in the form of a robot (FIG. 1, 100a), a vehicle (FIG. 1, 100b-1, 100b-2), an XR device (FIG. 1, 100c), a portable device (FIG. 1, 100d), a home appliance (FIG. 1, 100e), an IoT device (FIG. 1, 100f), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate/environmental device, an AI server/device (FIG. 1, 140), a base station (FIG. 1, 120), a network node, etc. Wireless devices may be mobile or stationary, depending on the use/service.

In FIG. 4, various elements, components, units/parts, and/or modules within the wireless device (400) may be entirely interconnected via a wired interface, or at least some may be wirelessly connected via a communication unit (410). For example, within the wireless device (400), the control unit (420) and the communication unit (410) may be wired, and the control unit (420) and the first unit (e.g., 430, 440) may be wirelessly connected via the communication unit (410). In addition, each element, component, unit/part, and/or module within the wireless device (400) may further include one or more elements. For example, the control unit (420) may be composed of one or more processor sets. For example, the control unit (420) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphics processing processor, a memory control processor, etc. As another example, the memory unit (430) may be composed of RAM, DRAM (dynamic RAM), ROM, flash memory, volatile memory, non-volatile memory, and/or a combination thereof.

Mobile devices to which this specification applies

FIG. 5 is a drawing illustrating an example of a portable device to which the present specification applies.

FIG. 5 illustrates an example of a mobile device to which the present specification applies. The mobile device may include a smart phone, a smart pad, a wearable device (e.g., a smart watch, a smart glass), a portable computer (e.g., a laptop, etc.). The mobile device may be referred to as a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), or a wireless terminal (WT).

Referring to FIG. 5, the portable device (500) may include an antenna unit (508), a communication unit (510), a control unit (520), a memory unit (530), a power supply unit (540a), an interface unit (540b), and an input/output unit (540c). The antenna unit (508) may be configured as a part of the communication unit (510). Blocks 510 to 530/540a to 540c correspond to blocks 410 to 430/440 of FIG. 4, respectively.

The communication unit (510) can transmit and receive signals (e.g., data, control signals, etc.) with other wireless devices and base stations. The control unit (520) can control components of the portable device (500) to perform various operations. The control unit (520) can include an AP (application processor). The memory unit (530) can store data/parameters/programs/codes/commands required for operating the portable device (500). In addition, the memory unit (530) can store input/output data/information, etc. The power supply unit (540a) supplies power to the portable device (500) and can include a wired/wireless charging circuit, a battery, etc. The interface unit (540b) can support connection between the portable device (500) and other external devices. The interface unit (540b) can include various ports (e.g., audio input/output ports, video input/output ports) for connection with external devices. The input/output unit (540c) can input or output image information/signals, audio information/signals, data, and/or information input from a user. The input/output unit (540c) can include a camera, a microphone, a user input unit, a display unit (540d), a speaker, and/or a haptic module.

For example, in the case of data communication, the input/output unit (540c) obtains information/signals (e.g., touch, text, voice, image, video) input by the user, and the obtained information/signals can be stored in the memory unit (530). The communication unit (510) converts the information/signals stored in the memory into wireless signals, and can directly transmit the converted wireless signals to other wireless devices or to a base station. In addition, the communication unit (510) can receive wireless signals from other wireless devices or base stations, and then restore the received wireless signals to the original information/signals. The restored information/signals can be stored in the memory unit (530) and then output in various forms (e.g., text, voice, image, video, haptic) through the input/output unit (540c).

Physical channels and general signal transmission

In a wireless access system, a terminal can receive information from a base station through the downlink (DL) and transmit information to the base station through the uplink (UL). The information transmitted and received by the base station and the terminal includes general data information and various control information, and various physical channels exist depending on the type/purpose of the information they transmit and receive.

FIG. 6 is a diagram illustrating physical channels applicable to this specification and a signal transmission method using them.

When a terminal is powered on again from a powered-off state or enters a new cell, it performs an initial cell search task such as synchronizing with the base station at step S611. To do this, the terminal can receive a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the base station to synchronize with the base station and obtain information such as a cell ID.

Thereafter, the terminal can receive a physical broadcast channel (PBCH) signal from the base station to obtain broadcast information within the cell. Meanwhile, the terminal can receive a downlink reference signal (DL RS: Downlink Reference Signal) in the initial cell search phase to check the downlink channel status. After completing the initial cell search, the terminal can receive a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) according to the physical downlink control channel information in step S612 to obtain more specific system information.

Thereafter, the terminal may perform a random access procedure such as steps S613 to S616 to complete connection to the base station. To this end, the terminal may transmit a preamble through a physical random access channel (PRACH) (S613), and receive a random access response (RAR) for the preamble through a physical downlink control channel and a physical downlink shared channel corresponding thereto (S614). The terminal may transmit a physical uplink shared channel (PUSCH) using scheduling information in the RAR (S615), and perform a contention resolution procedure such as receiving a physical downlink control channel signal and a physical downlink shared channel signal corresponding thereto (S616).

A terminal that has performed the procedure described above can then perform reception of a physical downlink control channel signal and/or a physical downlink shared channel signal (S617) and transmission of a physical uplink shared channel (PUSCH) signal and/or a physical uplink control channel (PUCCH) signal (S618) as a general uplink/downlink signal transmission procedure.

Control information transmitted from a terminal to a base station is collectively referred to as uplink control information (UCI). UCI includes hybrid automatic repeat and request acknowledgement/negative-ACK (HARQ-ACK/NACK), scheduling request (SR), channel quality indication (CQI), precoding matrix indication (PMI), rank indication (RI), beam indication (BI) information, etc. In this case, UCI is generally transmitted periodically through PUCCH, but depending on the embodiment (e.g., when control information and traffic data must be transmitted simultaneously), it may be transmitted through PUSCH. In addition, the terminal may aperiodically transmit UCI through PUSCH upon request/instruction from the network.

Figure 7 is a diagram illustrating the structure of a wireless frame applicable to this specification.

Uplink and downlink transmission based on the NR system can be based on frames such as those in FIG. 7. At this time, one radio frame has a length of 10 ms and can be defined by two 5 ms half-frames (half-frames, HF). One half-frame can be defined by five 1 ms subframes (subframes, SF). One subframe is divided into one or more slots, and the number of slots in a subframe can depend on subcarrier spacing (SCS). At this time, each slot can include 12 or 14 OFDM (A) symbols depending on CP (cyclic prefix). When normal CP is used, each slot can include 14 symbols. When extended CP is used, each slot can include 12 symbols. Here, the symbol may include an OFDM symbol (or CP-OFDM symbol), an SC-FDMA symbol (or DFT-s-OFDM symbol).

Table 1 shows the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when a general CP is used, and Table 2 shows the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when an extended CP is used.

In the above Tables 1 and 2, N ^slot _symb may represent the number of symbols in a slot, N ^frame,μ _slot may represent the number of slots in a frame, and N ^subframe,μ _slot may represent the number of slots in a subframe.

In addition, in a system to which the present specification is applicable, OFDM(A) numerologies (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into one terminal. Accordingly, the (absolute time) section of a time resource (e.g., SF, slot or TTI) (conveniently, collectively called TU (time unit)) consisting of the same number of symbols may be set differently between the merged cells.

NR can support multiple numerologies (or subcarrier spacing (SCS)) to support various 5G services. For example, when the SCS is 15 kHz, it supports wide area in traditional cellular bands, when the SCS is 30 kHz/60 kHz, it supports dense-urban, lower latency and wider carrier bandwidth, and when the SCS is 60 kHz or higher, it can support bandwidths larger than 24.25 GHz to overcome phase noise.

The NR frequency band is defined by two types of frequency ranges (FR1, FR2). FR1 and FR2 can be configured as shown in the table below. In addition, FR2 can mean millimeter wave (mmW).

In addition, as an example, the numerology described above may be set differently in a communication system to which the present specification is applicable. As an example, a Terahertz wave (THz) band may be used as a frequency band higher than the FR2 described above. In the THz band, the SCS may be set larger than in the NR system, and the number of slots may also be set differently, and is not limited to the above-described embodiment. The THz band will be described later.

Figure 8 is a drawing illustrating a slot structure applicable to this specification.

A slot contains multiple symbols in the time domain. For example, in the case of a normal CP, a slot contains 7 symbols, but in the case of an extended CP, a slot may contain 6 symbols. A carrier contains multiple subcarriers in the frequency domain. An RB (Resource Block) can be defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain.

Additionally, a Bandwidth Part (BWP) is defined as multiple consecutive (P)RBs in the frequency domain and can correspond to one numerology (e.g., SCS, CP length, etc.).

A carrier can contain up to N (e.g., 5) BWPs. Data communication is performed through activated BWPs, and only one BWP can be activated for one terminal. Each element in the resource grid is referred to as a resource element (RE), and one complex symbol can be mapped.

6G communication system

The 6G (wireless communication) system aims at (i) very high data rates per device, (ii) a very large number of connected devices, (iii) global connectivity, (iv) very low latency, (v) lower energy consumption of battery-free IoT devices, (vi) ultra-reliable connectivity, and (vii) connected intelligence with machine learning capabilities. The vision of the 6G system can be divided into four aspects: "intelligent connectivity", "deep connectivity", "holographic connectivity", and "ubiquitous connectivity", and the 6G system can satisfy the requirements as shown in Table 4 below. That is, Table 4 is a table showing the requirements of the 6G system.

At this time, 6G systems may have key factors such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), massive machine type communications (mMTC), AI integrated communication, tactile internet, high throughput, high network capacity, high energy efficiency, low backhaul and access network congestion, and enhanced data security.

FIG. 9 is a diagram illustrating an example of a communication structure that can be provided in a 6G system applicable to this specification.

Referring to Fig. 9, the 6G system is expected to have 50 times higher simultaneous wireless communication connectivity than the 5G wireless communication system. URLLC, a key feature of 5G, is expected to become a more important technology in 6G communication by providing end-to-end delay of less than 1 ms. At this time, the 6G system will have much better volumetric spectral efficiency than the frequently used area spectral efficiency. The 6G system can provide very long battery life and advanced battery technology for energy harvesting, so that mobile devices in the 6G system may not need to be charged separately. In addition, new network characteristics in 6G may be as follows.

- Satellite integrated network: 6G is expected to be integrated with satellites to provide a global mobile constellation. The integration of terrestrial, satellite and airborne networks into a single wireless communication system could be crucial for 6G.

- Connected intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary and will update the wireless evolution from “connected things” to “connected intelligence.” AI can be applied at each stage of the communication process (or at each stage of signal processing, as described below).

- Seamless integration of wireless information and energy transfer: 6G wireless networks will transfer power to charge the batteries of devices such as smartphones and sensors. Therefore, wireless information and energy transfer (WIET) will be integrated.

- Ubiquitous super 3-dimemtion connectivity: Access to networks and core network functions of drones and very low Earth orbit satellites will create super 3-dimemtion connectivity in 6G ubiquitous.

Some general requirements from the new network characteristics of 6G as mentioned above can be as follows:

- Small cell networks: The idea of small cell networks was introduced to improve the quality of received signals as a result of increased throughput, energy efficiency, and spectrum efficiency in cellular systems. As a result, small cell networks are an essential feature for 5G and beyond 5G (5GB) communication systems. Accordingly, 6G communication systems also adopt the characteristics of small cell networks.

- Ultra-dense heterogeneous network: Ultra-dense heterogeneous networks will be another important feature of 6G communication systems. A multi-tier network composed of heterogeneous networks improves overall QoS and reduces costs.

- High-capacity backhaul: Backhaul connections are characterized by high-capacity backhaul networks to support high-capacity traffic. High-speed fiber optics and free-space optics (FSO) systems may be possible solutions to this problem.

- Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communication is one of the functions of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

- Softwarization and virtualization: Softwarization and virtualization are two important features that are fundamental to the design process in 5GB networks to ensure flexibility, reconfigurability, and programmability. In addition, billions of devices can be shared on a shared physical infrastructure.

Core implementation technology of 6G system

- Artificial Intelligence (AI)

The most important and newly introduced technology in the 6G system is AI. The 4G system did not involve AI. The 5G system will support partial or very limited AI. However, the 6G system will be fully AI-supported for automation. Advances in machine learning will create more intelligent networks for real-time communications in 6G. Introducing AI in communications can simplify and improve real-time data transmission. AI can use numerous analyses to determine how complex target tasks are performed. In other words, AI can increase efficiency and reduce processing delays.

Time-consuming tasks such as handover, network selection, and resource scheduling can be performed instantly using AI. AI can also play a significant role in M2M, machine-to-human, and human-to-machine communication. AI can also be a rapid communication in brain computer interface (BCI). AI-based communication systems can be supported by metamaterials, intelligent structures, intelligent networks, intelligent devices, intelligent cognitive radios, self-sustaining wireless networks, and machine learning.

Recently, there have been attempts to integrate AI with wireless communication systems, but these have been focused on the application layer, network layer, and especially deep learning in the field of wireless resource management and allocation. However, these studies are gradually developing into the MAC layer and physical layer, and in particular, there are attempts to combine deep learning with wireless transmission in the physical layer. AI-based physical layer transmission means applying signal processing and communication mechanisms based on AI drivers rather than traditional communication frameworks in terms of fundamental signal processing and communication mechanisms. For example, it can include deep learning-based channel coding and decoding, deep learning-based signal estimation and detection, deep learning-based multiple input multiple output (MIMO) mechanisms, and AI-based resource scheduling and allocation.

Machine learning can be used for channel estimation and channel tracking, and power allocation, interference cancellation, etc. in the physical layer of the downlink (DL). Machine learning can also be used for antenna selection, power control, and symbol detection in MIMO systems.

However, the application of DNN for transmission in the physical layer may have the following problems.

Deep learning-based AI algorithms require a large amount of training data to optimize training parameters. However, due to limitations in obtaining data in a specific channel environment as training data, a large amount of training data is used offline. This is because static training on training data in a specific channel environment can cause a conflict between the dynamic characteristics and diversity of the wireless channel.

In addition, current deep learning mainly targets real signals. However, the signals of the physical layer of wireless communication are complex signals. In order to match the characteristics of wireless communication signals, more research is needed on neural networks that detect complex domain signals.

Below, we will look at machine learning in more detail.

Machine learning refers to a series of operations that teach machines to create machines that can perform tasks that people can or cannot do. Machine learning requires data and a learning model. In machine learning, data learning methods can be broadly divided into three: supervised learning, unsupervised learning, and reinforcement learning.

Neural network learning is to minimize the error of the output. Neural network learning is a process of repeatedly inputting learning data into the neural network, calculating the neural network output and target error for the learning data, and backpropagating the neural network error from the output layer of the neural network to the input layer in the direction of reducing the error, thereby updating the weights of each node of the neural network.

Supervised learning uses training data with correct answers labeled in the training data, while unsupervised learning may not have correct answers labeled in the training data. That is, for example, in the case of supervised learning for data classification, the training data may be data in which each category is labeled in the training data. The labeled training data is input to the neural network, and the error can be calculated by comparing the output (category) of the neural network with the label of the training data. The calculated error is backpropagated in the neural network in the reverse direction (i.e., from the output layer to the input layer), and the connection weights of each node in each layer of the neural network can be updated according to the backpropagation. The amount of change in the connection weights of each node that is updated can be determined according to the learning rate. The neural network's calculation of the input data and the backpropagation of the error can constitute a learning cycle (epoch). The learning rate can be applied differently depending on the number of repetitions of the learning cycle of the neural network. For example, in the early stages of learning a neural network, a high learning rate can be used to allow the network to quickly achieve a certain level of performance, thereby increasing efficiency, while in the later stages of learning, a low learning rate can be used to increase accuracy.

Depending on the characteristics of the data, the learning method may vary. For example, if the goal is to accurately predict data transmitted from the transmitter to the receiver in a communication system, it is preferable to perform learning using supervised learning rather than unsupervised learning or reinforcement learning.

The learning model corresponds to the human brain, and the most basic linear model can be thought of, but the machine learning paradigm that uses highly complex neural network structures, such as artificial neural networks, as learning models is called deep learning.

The neural network cores used in learning methods can be broadly divided into deep neural networks (DNN), convolutional deep neural networks (CNN), and recurrent Boltzmann machines (RNN), and these learning models can be applied.

An artificial neural network is an example of multiple perceptrons connected together.

Figure 10 shows an example of a perceptron structure.

Referring to Fig. 10, when an input vector x=(x1,x2,...,xd) is input, the entire process of multiplying each component by a weight (W1,W2,...,Wd), adding up all the results, and then applying the activation function σ() is called a perceptron. A large artificial neural network structure can extend the simplified perceptron structure illustrated in Fig. 10 to apply the input vector to perceptrons of different dimensions. For convenience of explanation, input values or output values are called nodes.

Meanwhile, the perceptron structure illustrated in Fig. 10 can be explained as consisting of a total of three layers based on input and output values. An artificial neural network in which there are H perceptrons of (d+1) dimensions between the 1st layer and the 2nd layer, and K perceptrons of (H+1) dimensions between the 2nd layer and the 3rd layer can be expressed as in Fig. 4. Fig. 11 shows an example of a multilayer perceptron structure.

The layer where the input vector is located is called the input layer, the layer where the final output value is located is called the output layer, and all layers located between the input layer and the output layer are called hidden layers. The example in Fig. 4 shows three layers, but when counting the number of actual artificial neural network layers, the input layer is excluded, so it can be viewed as a total of two layers. The artificial neural network is composed of perceptrons of basic blocks connected in two dimensions.

The above-mentioned input layer, hidden layer, and output layer can be applied jointly not only to multilayer perceptron but also to various artificial neural network structures such as CNN and RNN, which will be described later. The more hidden layers there are, the deeper the artificial neural network becomes, and the machine learning paradigm that uses a sufficiently deep artificial neural network as a learning model is called deep learning. In addition, the artificial neural network used for deep learning is called a deep neural network (DNN: Deep neural network).

The deep neural network illustrated in Fig. 12 is a multilayer perceptron composed of eight hidden layers and eight output layers. The multilayer perceptron structure is expressed as a fully-connected neural network. In a fully-connected neural network, there is no connection relationship between nodes located in the same layer, and there is a connection relationship only between nodes located in adjacent layers. DNN has a fully-connected neural network structure and is composed of a combination of multiple hidden layers and activation functions, and can be usefully applied to identify correlation characteristics between inputs and outputs. Here, the correlation characteristic can mean the joint probability of inputs and outputs.

Meanwhile, depending on how multiple perceptrons are connected to each other, various artificial neural network structures different from the aforementioned DNN can be formed.

In DNN, nodes located within a single layer are arranged in a one-dimensional vertical direction. However, Fig. 13 can assume a case where nodes are arranged two-dimensionally, with w nodes in width and h nodes in height (convolutional neural network structure of Fig. 6). In this case, since a weight is added to each connection in the connection process from one input node to the hidden layer, a total of h×w weights must be considered. Since there are h×w nodes in the input layer, a total of h2w2 weights are required between two adjacent layers.

The convolutional neural network of Fig. 13 has a problem in that the number of weights increases exponentially according to the number of connections. Therefore, instead of considering the connections of all modes between adjacent layers, it assumes that there is a small filter, and performs weighted sum and activation function operations on the overlapping portions of the filters, as in Fig. 7.

One filter has a weight corresponding to the number of its size, and learning of the weight can be performed so that a specific feature on the image can be extracted as a factor and output. In Fig. 14, a 3×3 sized filter is applied to the 3×3 area at the upper left of the input layer, and the output value resulting from performing weighted sum and activation function operations for the corresponding node is stored in z22.

The above filter performs weighted sum and activation function operations while moving horizontally and vertically at a certain interval while scanning the input layer, and places the output value at the current filter position. This operation method is similar to the convolution operation for images in the field of computer vision, so a deep neural network with this structure is called a convolutional neural network (CNN), and the hidden layer generated as a result of the convolution operation is called a convolutional layer. In addition, a neural network with multiple convolutional layers is called a deep convolutional neural network (DCNN).

In the convolution layer, the number of weights can be reduced by calculating the weighted sum by including only the nodes located in the area covered by the filter at the node where the current filter is located. As a result, one filter can be used to focus on features for a local area. Accordingly, CNN can be effectively applied to image data processing where physical distance in a two-dimensional area is an important judgment criterion. Meanwhile, CNN can apply multiple filters immediately before the convolution layer, and can also generate multiple output results through the convolution operation of each filter.

On the other hand, there may be data for which sequence characteristics are important depending on the data properties. Considering the length variability and chronological relationship of these sequence data, the structure that applies the method of inputting one element of the data sequence at each time step and inputting the output vector (hidden vector) of the hidden layer output at a specific time together with the next element in the sequence to an artificial neural network is called a recurrent neural network structure.

Figure 15 shows an example of a neural network structure in which a recurrent loop exists.

Referring to Fig. 15, a recurrent neural network (RNN) is a structure that inputs elements (x1(t), x2(t), ,..., xd(t)) of a certain time point t in a data sequence into a fully connected neural network, and applies a weighted sum and an activation function along with the hidden vector (z1(t-1), z2(t-1),..., zH(t-1)) of the immediately previous time point t-1. The reason for transmitting the hidden vector to the next time point in this way is because the information in the input vectors of the previous time points is considered to be accumulated in the hidden vector of the current time point.

Figure 16 shows an example of the operational structure of a recurrent neural network.

Referring to Figure 16, the recurrent neural network operates in a predetermined time order on the input data sequence.

When the input vector (x1(t), x2(t), ,..., xd(t)) at time point 1 is input to the recurrent neural network, the hidden vector (z1(1), z2(1),..., zH(1)) is input together with the input vector (x1(2), x2(2),..., xd(2)) at time point 2, and the hidden layer vector (z1(2), z2(2),..., zH(2)) is determined through the weighted sum and activation function. This process is repeatedly performed until time points 2, 3, ,,, and T.

Meanwhile, when multiple hidden layers are arranged in a recurrent neural network, it is called a deep recurrent neural network (DRNN). Recurrent neural networks are designed to be usefully applied to sequence data (e.g. natural language processing).

It is a neural network core used in a learning manner, and includes various deep learning techniques such as DNN, CNN, RNN, Restricted Boltzmann Machine (RBM), Deep Belief Network (DBN), and Deep Q-Network, and can be applied to fields such as computer vision, speech recognition, natural language processing, and speech/signal processing.

Recently, there have been attempts to integrate AI with wireless communication systems, but these have been focused on the application layer, network layer, and especially deep learning in the field of wireless resource management and allocation. However, these studies are gradually developing into the MAC layer and the Physical layer, and in particular, there are attempts to combine deep learning with wireless transmission in the Physical layer. AI-based physical layer transmission means applying signal processing and communication mechanisms based on AI drivers, rather than traditional communication frameworks, in terms of fundamental signal processing and communication mechanisms. For example, it can include deep learning-based channel coding and decoding, deep learning-based signal estimation and detection, deep learning-based MIMO mechanism, and AI-based resource scheduling and allocation.

THz(Terahertz) communication

THz communication can be applied in 6G systems. For example, the data transmission rate can be increased by increasing the bandwidth. This can be done by using sub-THz communication with a wide bandwidth and applying advanced massive MIMO technology.

FIG. 17 is a diagram illustrating an electromagnetic spectrum applicable to the present specification. As an example, referring to FIG. 17, THz waves, also known as sub-millimeter radiation, generally represent a frequency band between 0.1 THz and 10 THz with a corresponding wavelength in the range of 0.03 mm-3 mm. The 100 GHz-300 GHz band range (Sub THz band) is considered to be a major part of the THz band for cellular communications. Adding the Sub-THz band to the mmWave band will increase the capacity of 6G cellular communications. Among the defined THz bands, 300 GHz-3 THz is in the far infrared (IR) frequency band. The 300 GHz-3 THz band is a part of the optical band, but is at the boundary of the optical band, just behind the RF band. Therefore, this 300 GHz-3 THz band exhibits similarities with RF.

Key characteristics of THz communications include (i) widely available bandwidth to support very high data rates, and (ii) high path loss at high frequencies (highly directional antennas are essential). The narrow beam widths generated by highly directional antennas reduce interference. The small wavelength of THz signals allows a much larger number of antenna elements to be integrated into devices and BSs operating in this band. This allows the use of advanced adaptive array techniques to overcome range limitations.

optical wireless technology

OWC (optical wireless communication) technology is planned for 6G communication in addition to RF-based communication for all possible device-to-access networks. These networks connect to network-to-backhaul/fronthaul network connections. OWC technology has already been used since 4G communication systems, but it will be used more widely to meet the needs of 6G communication systems. OWC technologies such as light fidelity, visible light communication, optical camera communication, and free space optical (FSO) communication based on optical bands are already well known technologies. Optical wireless technology-based communication can provide very high data rates, low latency, and secure communication. LiDAR (light detection and ranging) can also be used for ultra-high-resolution 3D mapping in 6G communication based on optical bands.

FSO Backhaul Network

The characteristics of the transmitter and receiver of the FSO system are similar to those of the optical fiber network. Therefore, the data transmission of the FSO system is similar to that of the optical fiber system. Therefore, FSO can be a good technology to provide backhaul connections in 6G systems together with optical fiber networks. With FSO, very long-distance communication is possible even at distances of more than 10,000 km. FSO supports large-capacity backhaul connections for remote and non-remote areas such as the ocean, space, underwater, and isolated islands. FSO also supports cellular base station connections.

Massive MIMO technology

One of the key technologies to improve spectral efficiency is the application of MIMO technology. As MIMO technology improves, spectral efficiency also improves. Therefore, massive MIMO technology will be important in 6G systems. Since MIMO technology utilizes multiple paths, multiplexing technology and beam generation and operation technology suitable for the THz band must also be considered so that data signals can be transmitted through more than one path.

Blockchain

Blockchain will be an important technology for managing large amounts of data in future communication systems. Blockchain is a form of distributed ledger technology, where a distributed ledger is a database distributed across a large number of nodes or computing devices. Each node replicates and stores an identical copy of the ledger. Blockchain is managed by a peer-to-peer (P2P) network. It can exist without being managed by a central authority or server. Data in a blockchain is collected together and organized into blocks. Blocks are linked together and protected using cryptography. Blockchain perfectly complements large-scale IoT with its inherently enhanced interoperability, security, privacy, reliability, and scalability. Thus, blockchain technology offers several features such as interoperability between devices, traceability of large amounts of data, autonomous interaction of other IoT systems, and large-scale connection stability of 6G communication systems.

3D Networking

6G systems support vertical expansion of user communications by integrating terrestrial and air networks. 3D BS will be provided via low-orbit satellites and UAVs. Adding a new dimension in terms of altitude and associated degrees of freedom makes 3D connections significantly different from existing 2D networks.

Quantum Communication

In the context of 6G networks, unsupervised reinforcement learning of networks is promising. Supervised learning methods cannot label the massive amount of data generated by 6G. Unsupervised learning does not require labeling. Therefore, this technology can be used to autonomously build representations of complex networks. Combining reinforcement learning and unsupervised learning can allow networks to operate in a truly autonomous manner.

unmanned aerial vehicle

Unmanned aerial vehicles (UAVs) or drones will be a key element in 6G wireless communications. In most cases, high-speed data wireless connectivity is provided using UAV technology. Base station entities are installed on UAVs to provide cellular connectivity. UAVs have certain features that are not found in fixed base station infrastructure such as easy deployment, robust line-of-sight links, and freedom of movement with controlled mobility. During emergency situations such as natural disasters, deployment of terrestrial communication infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle such situations. UAVs will be a new paradigm in wireless communications. This technology facilitates three basic requirements of wireless networks namely eMBB, URLLC, and mMTC. UAVs can also support several purposes such as enhancing network connectivity, fire detection, disaster emergency services, security and surveillance, pollution monitoring, parking monitoring, and accident monitoring. Therefore, UAV technology is recognized as one of the most important technologies for 6G communications.

Cell-free Communication

Tight integration of multiple frequencies and heterogeneous communication technologies is crucial in 6G systems. As a result, users can seamlessly move from one network to another without having to make any manual configuration on their devices. The best network among the available communication technologies will be automatically selected. This will break the limitations of the cell concept in wireless communications. Currently, user movement from one cell to another causes too many handovers in dense networks, resulting in handover failures, handover delays, data loss, and ping-pong effects. 6G cell-free communications will overcome all these and provide better QoS. Cell-free communications will be achieved through multi-connectivity and multi-tier hybrid technologies and different heterogeneous radios in the devices.

Integrated wireless information and energy transfer (WIET)

WIET uses the same fields and waves as wireless communication systems. In particular, sensors and smartphones will be charged using wireless power transfer during communication. WIET is a promising technology for extending the life of battery-powered wireless systems. Therefore, battery-less devices will be supported in 6G communications.

Integration of sensing and communication

Autonomous wireless networks are capable of continuously sensing dynamically changing environmental conditions and exchanging information between different nodes. In 6G, sensing will be tightly integrated with communications to support autonomous systems.

Integration of Access Backhaul Networks

In 6G, the density of access networks will be enormous. Each access network will be connected to backhaul connections such as fiber and FSO networks. To cope with the very large number of access networks, there will be tight integration between access and backhaul networks.

Holographic Beamforming

Beamforming is a signal processing procedure that adjusts an array of antennas to transmit a wireless signal in a specific direction. It is a subset of smart antennas or advanced antenna systems. Beamforming technology has several advantages such as high signal-to-noise ratio, interference avoidance and rejection, and high network efficiency. Hologram beamforming (HBF) is a new beamforming method that is quite different from MIMO systems because it uses software-defined antennas. HBF will be a very effective approach for efficient and flexible transmission and reception of signals in multi-antenna communication devices in 6G.

Big Data Analysis

Big data analytics is a complex process for analyzing a variety of large data sets or big data. This process ensures complete data management by finding information such as hidden data, unknown correlations, and customer tendencies. Big data is collected from various sources such as video, social networks, images, and sensors. This technology is widely used to process massive data in 6G systems.

large intelligent surface (LIS)

In the case of THz band signals, since the straightness is strong, many shadow areas may be created due to obstacles. LIS technology becomes important because it can expand the communication area, enhance communication stability, and provide additional value-added services by installing LIS near these shadow areas. LIS is an artificial surface made of electromagnetic materials and can change the propagation of incoming and outgoing radio waves. LIS can be seen as an extension of massive MIMO, but it has different array structures and operating mechanisms from massive MIMO. In addition, LIS has the advantage of low power consumption because it operates as a reconfigurable reflector with passive elements, that is, it passively reflects signals without using an active RF chain. In addition, since each passive reflector of LIS must independently adjust the phase shift of the incident signal, it can be advantageous for wireless communication channels. By appropriately adjusting the phase shift via the LIS controller, the reflected signal can be collected at the target receiver to boost the received signal power.

Terahertz (THz) wireless communications

FIG. 18 is a diagram illustrating a THz communication method applicable to this specification.

Referring to Fig. 18, THz wireless communication is a wireless communication using THz waves having a frequency of approximately 0.1 to 10 THz (1 THz = 1012 Hz), and may refer to terahertz (THz) band wireless communication using a very high carrier frequency of 100 GHz or higher. THz waves are located between the RF (Radio Frequency)/millimeter (mm) and infrared bands, and (i) compared to visible light/infrared rays, they penetrate non-metallic/non-polarizable materials well, and compared to RF/millimeter waves, they have a shorter wavelength, so they have high straightness and can enable beam focusing.

In addition, since the photon energy of THz waves is only a few meV, it has the characteristic of being harmless to the human body. The frequency band expected to be used for THz wireless communication may be the D-band (110 GHz to 170 GHz) or H-band (220 GHz to 325 GHz) bands where propagation loss due to absorption of molecules in the air is small. In addition to 3GPP, standardization discussions for THz wireless communication are being centered around the IEEE 802.15 THz WG (working group), and standard documents issued by the TG (task group) of IEEE 802.15 (e.g., TG3d, TG3e) can specify or supplement the contents described in this specification. THz wireless communication can be applied to wireless cognition, sensing, imaging, wireless communication, THz navigation, etc.

Specifically, referring to FIG. 18, THz wireless communication scenarios can be classified into a macro network, a micro network, and a nanoscale network. In a macro network, THz wireless communication can be applied to vehicle-to-vehicle (V2V) connections and backhaul/fronthaul connections. In a micro network, THz wireless communication can be applied to fixed point-to-point or multi-point connections such as indoor small cells, wireless connections in data centers, and near-field communications such as kiosk downloading. Table 5 below is a table showing examples of technologies that can be used in THz waves.

FIG. 19 is a diagram illustrating a THz wireless communication transceiver applicable to the present specification.

Referring to Figure 19, THz wireless communication can be classified based on the method for THz generation and reception. THz generation methods can be classified into optical device or electronic device-based technologies.

At this time, methods for generating THz using electronic components include a method using a semiconductor component such as a resonant tunneling diode (RTD), a method using a local oscillator and a multiplier, a MMIC (monolithic microwave integrated circuits) method using an integrated circuit based on a compound semiconductor HEMT (high electron mobility transistor), and a method using a Si-CMOS-based integrated circuit. In the case of Fig. 19, a doubler (tripler, multiplier, multiplier) is applied to increase the frequency, and it passes through a subharmonic mixer and is radiated by an antenna. Since the THz band forms a high frequency, a doubler is essential. Here, the multiplier is a circuit that has an output frequency that is N times that of the input, and matches it to a desired harmonic frequency and filters out all remaining frequencies. In addition, beamforming can be implemented by applying an array antenna, etc. to the antenna of Fig. 19. In Figure 19, IF represents intermediate frequency, tripler and multipler represent multipliers, PA represents a power amplifier, LNA represents a low noise amplifier, and PLL represents a phase-locked loop.

FIG. 20 is a diagram illustrating a THz signal generation method applicable to the present specification. In addition, FIG. 21 is a diagram illustrating a wireless communication transceiver applicable to the present specification.

Referring to FIGS. 20 and 21, the optical device-based THz wireless communication technology refers to a method of generating and modulating a THz signal using an optical device. The optical device-based THz signal generation technology is a technology that generates an ultra-high-speed optical signal using a laser and an optical modulator, and converts it into a THz signal using an ultra-high-speed optical detector. Compared to a technology that uses only electronic devices, this technology makes it easy to increase the frequency, enables high-power signal generation, and obtains flat response characteristics in a wide frequency band. In order to generate a THz signal based on an optical device, a laser diode, a wideband optical modulator, and an ultra-high-speed optical detector are required, as illustrated in FIG. 20. In the case of FIG. 20, light signals of two lasers with different wavelengths are combined to generate a THz signal corresponding to the wavelength difference between the lasers. In Fig. 20, an optical coupler refers to a semiconductor device that transmits an electrical signal using optical waves to provide electrical isolation and coupling between circuits or systems, and a uni-travelling carrier photo-detector (UTC-PD) is one of the photodetectors, which uses electrons as active carriers and is a device that reduces the travel time of electrons by bandgap grading. UTC-PD is capable of detecting light at 150 GHz or higher. In Fig. 20, EDFA (erbium-doped fiber amplifier) represents an erbium-doped fiber amplifier, PD (photo detector) represents a semiconductor device that can convert an optical signal into an electrical signal, OSA represents an optical sub assembly that modularizes various optical communication functions (e.g., photoelectric conversion, electro-optical conversion, etc.) into a single component, and DSO represents a digital storage oscilloscope.

Fig. 22 is a drawing illustrating a transmitter structure applicable to the present specification. In addition, Fig. 23 is a drawing illustrating a modulator structure applicable to the present specification.

Referring to FIGS. 22 and 23, a general optical source of a laser can be passed through an optical wave guide to change the phase of a signal, etc. At this time, data is loaded by changing the electrical characteristics through a microwave contact, etc. Therefore, the optical modulator output is formed as a modulated waveform. An optical/electrical modulator (O/E converter) can generate a THz pulse according to an optical rectification operation by a nonlinear crystal, an optical/electrical conversion by a photoconductive antenna, an emission from a bunch of relativistic electrons, etc. A terahertz pulse (THz pulse) generated in the above manner can have a length in the unit of femto second to pico second. An optical/electronic converter (O/E converter) performs down conversion by utilizing the non-linearity of the device.

Considering the THz spectrum usage, it is likely that multiple contiguous GHz bands will be used for THz systems, either fixed or for mobile service. Based on an outdoor scenario, the available bandwidth can be classified based on an oxygen attenuation of 10^2 dB/km in the spectrum up to 1 THz. Accordingly, a framework may be considered in which the available bandwidth is composed of multiple band chunks. As an example of the framework, if the length of a THz pulse for one carrier is set to 50 ps, the bandwidth (BW) becomes approximately 20 GHz.

Effective down conversion from the infrared band to the terahertz band (THz band) depends on how to utilize the nonlinearity of the optical/electrical converter (O/E converter). That is, in order to down convert to a desired terahertz band (THz band), it is required to design an optical/electrical converter (O/E converter) that has the most ideal nonlinearity for moving to the terahertz band (THz band). If an optical/electrical converter (O/E converter) that does not match the target frequency band is used, there is a high possibility that errors will occur in the amplitude and phase of the pulse.

In a single carrier system, a terahertz transmit/receive system can be implemented using one optical-to-electrical converter. Depending on the channel environment, in a multi-carrier system, the number of optical-to-electrical converters may be required as many as the number of carriers. In particular, in the case of a multi-carrier system that utilizes multiple widebands according to a plan related to the aforementioned spectrum usage, this phenomenon will be prominent. In this regard, a frame structure for the multi-carrier system can be considered. A signal down-converted based on an optical-to-electrical converter can be transmitted in a specific resource area (e.g., a specific frame). The frequency area of the specific resource area can include a plurality of chunks. Each chunk can be composed of at least one component carrier (CC).

Here, the wireless communication technology implemented in the wireless device (200a, 200b) of the present specification may include not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. At this time, for example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology, and may be implemented with standards such as LTE Cat NB1 and/or LTE Cat NB2, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may perform communication based on LTE-M technology. At this time, for example, LTE-M technology may be an example of LPWAN technology, and may be called by various names such as eMTC (enhanced Machine Type Communication). For example, the LTE-M technology can be implemented by at least one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and/or 7) LTE M, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (200a, 200b) of the present specification can include at least one of ZigBee, Bluetooth, and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-described names. For example, the ZigBee technology can create PAN (personal area networks) related to small/low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

The symbols/abbreviations/terms used in this disclosure are as follows.

- D-MIMO: Distributed massive Multiple Input Multiple Output

- AP: Access Point

- CPU: Central Processing Unit

- CSI: Channel State Information

- UE: User Equipment

- ToA: Time of Arrival

- RSRP: Reference Signals Received Power

- OOB: Out-of-band

- SSB: Synchronization Signal Block

- RSC: Resource

- GPS: Global Positioning System

- B6G: Below 6 GHz

- mmWave: millimeter wave

- THz: terahertz

FIG. 24 is a diagram illustrating an example of a D-MIMO system applicable to the present disclosure. FIG. 25 is a diagram illustrating an example of a frame structure in a D-MIMO system applicable to the present disclosure.

Referring to FIG. 24, a D-MIMO system may be a system in which a plurality of geographically distributed antennas cooperate to serve a small number of terminals using a single time-frequency resource with the help of a fronthaul network and a central processing unit (CPU).

In a D-MIMO system, there is no cell boundary in the traditional sense. Therefore, in a D-MIMO system, all APs in the system operate as if they are in the same cell. When the concept of a D-MIMO system was initially developed, it started with all APs serving all terminals. However, in a D-MIMO system, there is a problem that APs that are far from the terminals do not contribute to improving the signal quality of the terminals, but only use transmission power, thereby reducing the efficiency of the system.

To solve these problems, the concept of a user-centric cluster, in which only APs close to a terminal provide services to the terminal, was introduced into the D-MIMO system. In the D-MIMO system, uplink and downlink can be multiplexed in the time domain. In addition, the D-MIMO system assumes that the number of APs is much larger than the number of terminals.

Referring to FIG. 25, the transmission and reception operations of the D-MIMO system may include three steps: 1) uplink channel estimation, 2) downlink data transmission, and 3) uplink data transmission. The above operations are performed within the coherence time of the channel, and therefore, it is assumed that the channel remains the same while the operations are performed. Here, the coherence time may be a coherence interval. It is also assumed that channel reciprocity, in which the uplink channel and the downlink channel are the same, is established. The steps 1) to 3) are described in detail as follows.

1) Uplink channel estimation

The terminal transmits the reference signal assigned to it to the AP. Each AP receives the reference signal transmitted by the terminal. Each AP estimates the channel between the AP and the terminal.

2) Downlink data transmission

Each AP performs channel-matched precoding on the data to be transmitted using the channel estimated in 1). That is, each AP multiplies the data to be transmitted by the complex conjugate of the channel estimated in the uplink. Each AP transmits the precoded data to the terminal. The data transmitted by each AP is canceled by the channel precoding as it passes through the channel. The terminal receives the data from each AP. In this case, the terminal receives the data transmitted by each AP in-phase.

3) Uplink data transmission

The terminal transmits uplink data to APs. The terminal may not perform precoding on the data. The APs receive data from the terminal. The APs generate an estimate value of the received data using the channel estimated in 1). Each AP transmits the generated estimate value to the CPU. The CPU receives the estimate value from each AP. The CPU may combine the estimate values. The CPU decodes the data based on the combined estimate value.

Joint Transmission

Combined transmission refers to a method in which multiple APs cooperate to transmit data to a terminal. When performing combined transmission, the quality of signals received by a terminal from multiple APs can be improved, and interference from signals transmitted by multiple APs to other terminals can be reduced.

For this operation, sharing of data and panel information (e.g., CSI) to be transmitted to the terminal is required between geographically distributed APs participating in the combined transmission. Therefore, high backhaul connection performance between APs is required. For example, high backhaul connection performance can mean that the transmission delay of the backhaul connection between APs is small and the transmission capacity is large.

The combined transmission method can be divided into a non-coherent combined transmission method and a coherent combined transmission method. In the case of non-coherent combined transmission, each AP transmits the same data, but each AP can independently perform precoding. Therefore, the terminal can obtain only power gain. On the other hand, in the case of coherent combined transmission, the APs can receive channel state information (CSI) from the terminal and perform precoding so that in-phase combining can be performed at the terminal based on the CSI. The terminal can receive signals from each AP and perform coherent combining on the signals. Therefore, the terminal can obtain additional signal gain.

User-centric AP clustering of D-MIMO systems

FIG. 26 is a diagram illustrating an example of terminal-centric AP clustering applicable to the present disclosure.

The biggest difference between the D-MIMO system and the existing cellular system is that in the case of the existing cellular system, the terminal selects and connects to the optimal cell among several cells, and one cell serves one terminal, whereas in the case of the D-MIMO system, multiple APs around the terminal serve the terminal, not one cell.

A set of APs serving terminals is called an AP cluster, and there are two main methods for forming AP clusters: network-centric AP clustering and UE-centric AP clustering. In network-centric clustering, each AP cluster is composed of a set of mutually exclusive APs that do not overlap each other, and the APs that make up the cluster serve the terminals within the cluster.

There are no cell boundaries within a cluster, but there may be inter-cluster interference at the boundaries between clusters. In contrast, terminal-centric clustering forms an AP cluster by having each terminal select the APs that serve it.

In the case of a terminal-centric cluster, serving APs may overlap between adjacent terminals, and thus, clusters of APs may overlap with each other. For example, referring to FIG. 25, since AP1 belongs to the cluster of UE1 (C ₁ ), the cluster of UE2 (C ₂ ), and the cluster of UE3 (C ₃ ), it serves all of UE1, UE2, and UE3. Since terminal-centric clustering always positions a terminal at the center of a cluster, a situation in which a terminal is located at the cluster boundary and is greatly affected by inter-cluster interference can be prevented. In the case of terminal-centric clustering, the concept of cell boundary in the traditional sense disappears, and the connection quality between the terminal and the AP can be periodically checked to update the AP cluster serving the corresponding terminal.

FIG. 27 is a diagram illustrating an example of initial connection in a D-MIMO system applicable to the present disclosure.

Fig. 27 shows an example of beam-formed initial connection in the mmWave/THz band. The biggest problem in mmWave/THz band transmission systems is the signal strength reduction due to path attenuation that increases as the carrier frequency of the transmission signal increases. To overcome this path attenuation, transmission systems in the mmWave/THz band use beamforming using multiple antennas.

That is, by using multiple antenna elements, the phase value of each antenna element can be appropriately set to increase the gain of the antenna so that the transmission signal is concentrated in a specific direction.

This type of antenna beamforming can be used at both the transmitter and receiver, and when terminals and APs use this beamforming, a beam alignment process that matches the beam directions between the terminal and AP is required during the initial connection process.

In the 3GPP NR standard, a method was introduced in which different beamformings are applied to SSBs (Synchronization signal blocks) for beam alignment during the initial connection process, and the terminal finds the optimal beam among the SSBs and makes the initial connection. In this process, the AP transmits all beams that can be served when transmitting SSBs.

If this method is directly introduced into the D-MIMO system, the terminal must search all beams of all APs it wants to connect to, and accordingly, the time required for initial connection increases by the number of APs that can be searched. In addition, since each AP must periodically transmit the entire beam, a very large system overhead may occur.

To solve these problems, methods have been proposed to reduce the range of the beam to be searched. The most representative method is to reduce the beam search range by using the location information of the terminal. GPS (Global Positioning System) information is typically used to determine the location information of the terminal, but GPS has a problem in that it cannot be used in cases where shadows occur due to tall buildings, such as in urban areas, or where the LoS (Line of Sight) with the satellite is blocked, such as indoors.

Specific embodiments of the present disclosure

The present disclosure proposes a method for determining the approximate location of a terminal in a D-MIMO system without the aid of GPS, thereby limiting the range of a beam that each AP must transmit for beam alignment between the terminal and the AP, thereby reducing the overhead of the entire system.

FIG. 28 is a diagram illustrating an example of an initial connection method according to one embodiment of the present disclosure.

FIG. 28 is an example of initial connection of a mmWave/THz band D-MIMO system using out-of-band (OOB) information according to one embodiment of the present disclosure. In the present disclosure, it is assumed that each of the APs and terminals supports both the B6G (below 6G) band and the mmWave/THz band.

Referring to Fig. 28, upon initial connection, the terminal can first find the optimal AP in the B6G band. Here, the optimal AP may be the first AP (AP1). That is, the terminal may attempt to connect to the first AP. At this time, the terminal may perform measurements on surrounding APs (the second AP (AP2) to the seventh AP (AP7)) of the first AP (AP1). The terminal may feed back the measurement results to the network. Alternatively, the terminal may obtain location information from the measurement results and report the location information to the network. Here, the location information may be approximate location information of the terminal.

The network can receive feedback on the measurement results from the terminal. Alternatively, the network can receive location information from the terminal. Based on the measurement results or location information, the network can reduce the range of beams that APs around the terminal (i.e., the first AP (AP1) to the seventh AP (AP7)) will sweep for initial connection.

To this end, the network can pre-schedule resources for performing measurements on surrounding APs based on the SSB of the AP (i.e., serving AP) to which the terminal wishes to connect in the B6G band. For example, when the terminal wishes to connect to the first AP (AP1), the pre-scheduled resources for performing measurements on the second AP (AP2) to the seventh AP (AP7) based on the SSB of the first AP (AP1) may be as follows.

FIG. 29 is a diagram illustrating an example of pre-scheduled resources according to one embodiment of the present disclosure.

Referring to FIG. 29, SSB may be an SSB resource of the first AP (AP1), and RSC2 to RSC7 may be pre-scheduled resources for measuring the second AP (AP2) to the seventh AP (AP7). RSC2 to RSC7 may be resources for the second AP (AP2) to the seventh AP (AP7) to transmit reference signals to the terminals, respectively.

RSC2 may be the first pre-scheduled resource, and RSC3 to RSC7 may be the second to sixth pre-scheduled resources. Here, RSC2 may be pre-scheduled based on a position in a time domain (RSC_offset_time) and a position in a frequency domain (RSC_offset_freq). The position in a time domain (RSC_offset_time) and the position in a frequency domain (RSC_offset_freq) may be preset values. RSC3 to RSC7 may be pre-scheduled based on RSC2 and a preset rule.

Referring again to FIG. 28, the terminal can detect the SSB of the serving AP. The terminal can obtain information about the locations of pre-scheduled resources based on the SSB. The terminal can receive reference signals from surrounding APs through the pre-scheduled resources. For example, the terminal can detect the SSB of the first AP, and obtain information about the locations of pre-scheduled resources (e.g., RSC2 to RSC6 of FIG. 29) based on the SSB of the first AP. The terminal can receive reference signals from the second to seventh APs (AP2 to AP7) through the pre-scheduled resources, respectively.

The terminal can perform measurements on reference signals to obtain location information. Here, the location information can be approximate location information of the terminal. For example, the terminal can measure RSRP (Reference Signals Received Power) or ToA (Time of Arrival) for each of the reference signals. Based on the measurement values, the terminal can select a preferred AP among surrounding APs.

For example, when the number of APs that the terminal can select is 2 and the terminal measures RSRP, the terminal can measure RSRP from RSC2 to RSC7 of FIG. 29, respectively, and select two having the highest measured values. That is, the terminal can measure RSRP of reference signals transmitted by the second to seventh APs (AP2 to AP7) through RSC2 to RSC7 of FIG. 29, and select two reference signals having the highest RSRP values among them. The terminal can select two APs that transmitted each of the two reference signals. The terminal can select the second AP (AP2) and the third AP (AP3) that are close to the terminal.

The terminal can report information about a preferred AP to the serving AP in the B6G band. For example, the terminal can report information about a preferred AP to the serving AP by defining a new 6-bit flag field in msg3 of the RACH (Random Access Channel) to turn on the flag of the preferred AP and turn off the flags of the remaining APs. The serving AP can report information about a preferred AP to the network. The network can receive information about a preferred AP from the serving AP.

For example, a terminal may report information about its preferred APs, the second AP (AP2) and the third AP (AP3), to its serving AP, the first AP (AP1). The serving AP, the first AP (AP1), may report information about its preferred APs, the second AP (AP2) and the third AP (AP3), to the network.

The network may instruct the serving AP and the preferred AP to perform beam sweep for the terminal. The network may instruct the serving AP and the preferred AP to perform beam sweep in the mmWave/THz band. In this case, the remaining APs may not perform beam sweep.

For example, the network can receive information about preferred APs, such as the second AP (AP2) and the third AP (AP3), from the serving AP, the first AP (AP1). The network can instruct the first to third APs (AP1 to AP3) to perform a beam sweep for the terminal. The network can instruct the first to third APs (AP1 to AP3) to perform a beam sweep in the mmWave/THz band. In this case, the fourth to seventh APs (AP4 to AP7) may not perform the beam sweep. Therefore, the overhead of system resources and the time required for beam search can be reduced.

In addition, the approximate location of the terminal can be determined based on the serving AP and the preferred AP. For example, the location of the terminal can be limited between the first AP (AP1) which is the serving AP and the second AP (AP2) and the third AP (AP3) which are the preferred APs. Using this, the beam search range of the first (AP1) in the mmWave/THz band can be limited to a 120 degree area in the direction of the second AP (AP2) and the third AP (AP3), and the beam search ranges of the second AP (AP2) and AP3 (AP3) can be limited to a 60 degree area in the direction of the first AP (AP1). In this case, the beam search range of the first AP (AP1) can be reduced by 66%, and the beam search ranges of the second AP and the third AP are effectively reduced by 84%.

Meanwhile, the network may select APs to perform beam sweep based on location information of the terminal. The APs to perform beam sweep may include at least one of a plurality of APs. For example, the APs to perform beam sweep may include a serving AP and APs preferred by the terminal, or may include some of the remaining APs excluding the serving AP and APs preferred by the terminal among the plurality of APs, or may include some of the serving AP and APs preferred by the terminal and some of the remaining APs excluding the serving AP and the preferred APs. In addition, the network may determine a beam sweep range of the APs to perform beam sweep based on location information of the terminal.

FIG. 30 is a flowchart of a beam search method according to one embodiment of the present disclosure.

Figure 30 is an example of a procedure in which the terminal selects a preferred AP using pre-scheduled resources and reports it to the network to limit the beam search range in the mmWave/THz band.

Referring to FIG. 30, multiple APs can transmit SSB and measurement reference signals to the terminal (S3005). The measurement reference signals may be pre-scheduled. The terminal can receive SSB and measurement reference signals from multiple APs from the terminal (S3005).

The terminal can select a serving AP (S3010). The serving AP may be the optimal AP. The terminal can measure the RSRP of SSBs. The terminal can select an AP that transmits an SSB with the largest RSRP value among multiple APs as the serving AP.

The terminal can select preferred APs (S3015). The preferred APs may be APs preferred by the terminal. The terminal can know the location of the pre-scheduled resource based on the location of the SSB resource transmitted by the serving AP. The relationship between the location of the SSB resource and the location of the pre-scheduled resource may be preset in the standard and may be known to the terminal in advance. The terminal can receive a reference signal from some of the plurality of APs through the pre-scheduled resources. Here, some of the plurality of APs may be APs located around the serving AP among the plurality of APs of S3005. The terminal can select the preferred APs by performing a measurement for the reference signal.

The terminal can transmit a random access request message to the serving AP (S3020). The terminal can transmit a random access request message to the serving AP in the B6G band.

The serving AP can receive a random access request message from the terminal (S3020). The serving AP can receive a random access request message from the terminal in the B6G band.

The serving AP can transmit a random access response message to the terminal (S3025). The serving AP can transmit a random access response message to the terminal in response to the random access request message. The serving AP can transmit the random access response message to the terminal in the B6G band.

The terminal can receive a random access response message from the serving AP (S3025). The terminal can receive a random access response message from the serving AP in the B6G band.

The terminal may transmit Msg3 to the serving AP (S3030). The terminal may transmit Msg3 to the serving AP in response to the random access response message. The terminal may transmit Msg3 to the serving AP in the B6G band. Msg3 may include information about the preferred APs selected by the terminal in step S3015.

The serving AP can receive Msg3 from the terminal (S3030). The serving AP can receive Msg3 from the terminal in the B6G band.

The serving AP can transmit Msg4 to the terminal (S3035). The serving AP can transmit Msg4 to the terminal in response to Msg3. The terminal can receive Msg4 from the serving AP (S3035).

The serving AP can obtain location information of the terminal (S3040). The serving AP can obtain information about preferred APs through Msg3 received in S3030. The serving AP can obtain location information of the terminal based on the location of the serving AP and the locations of the preferred APs. Here, the location information may be approximate location information of the terminal. Alternatively, the serving AP can receive location information of the terminal from the network.

The serving AP can determine beam sweep APs and beam sweep ranges of the beam sweep APs (S3045). The serving AP can determine beam sweep APs, which are APs to perform beam sweep, among a plurality of APs based on location information of the terminal. Here, the beam sweep APs can include at least one of the plurality of APs. The serving AP can determine beam sweep ranges of the beam sweep APs based on location information of the terminal.

Beam sweep APs can perform beam sweep (S3050). The serving AP can transmit information about the beam sweep range acquired in S3040 to the beam sweep APs. The beam sweep APs can perform beam sweep based on the information about the beam sweep range.

In contrast, beam sweep APs can receive information about the beam sweep range from the network and perform beam sweeping based on the information. Beam sweep APs can perform beam sweeping in a limited range. Beam sweep APs can perform beam sweeping in the mmWave/THz band.

FIG. 31 is a flowchart of a beam search method according to another embodiment of the present disclosure.

In Figure 31, the network may include a network controller or a central processor unit (CPU).

Referring to FIG. 31, the terminal may select a serving AP and preferred APs among a plurality of APs (S3105). The serving AP may be an optimal AP. The preferred APs may be APs preferred by the terminal. The terminal may receive SSB and a measurement reference signal from the plurality of APs. The measurement reference signal may be pre-scheduled. The terminal may measure RSRP of SSBs. The terminal may select an AP that transmits a signal having the largest RSRP measurement value among the plurality of APs as a serving AP. The terminal may know the location of the pre-scheduled resource based on the location of the SSB resource transmitted by the serving AP. The relationship between the location of the SSB resource and the location of the pre-scheduled resource may be preset in the standard and may be known to the terminal in advance. The terminal may receive a reference signal from some of the plurality of APs through the pre-scheduled resources. Here, some of the plurality of APs may be APs located around the serving AP among the plurality of APs that transmitted the SSB. The terminal can select preferred APs by performing measurements on reference signals.

The terminal can transmit Msg3 including information about preferred APs to the serving AP (S3110). The terminal can transmit a random access request message to the serving AP and, in response thereto, receive a random access response message from the serving AP. The terminal can transmit Msg3 including information about preferred APs in response to the random access response message. The terminal can transmit information about preferred APs to the serving AP in the B6G band.

The serving AP can receive Msg3 including information about preferred APs from the terminal (S3110). The serving AP can receive information about preferred APs from the terminal in the B6G band. The serving AP can transmit information about preferred APs to the network (S3115).

The network can receive information about preferred APs from the serving AP (S3115). The network can obtain location information of the terminal (S3120). The network can obtain location information of the terminal based on the location of the serving AP and the locations of the preferred APs. Here, the location information may be approximate location information of the terminal.

The network can determine beam sweep APs and beam sweep ranges of the beam sweep APs (S3125). The network can determine beam sweep APs, which are APs to perform beam sweep, among a plurality of APs based on location information of the terminal. Here, the beam sweep APs can include at least one of the plurality of APs. The network can determine beam sweep ranges of the beam sweep APs based on location information of the terminal.

The network may generate a first beam sweep request message and a second beam sweep request message (S3130). The first beam sweep request message may include information about a beam sweep range of a serving AP, and the second beam sweep request message may include information about beam sweep ranges of the first beam sweep APs. Here, the first beam sweep APs may be APs excluding the serving AP among the beam sweep APs determined in step S3125. If the serving AP is not included in the beam sweep APs determined in S3125, the first beam sweep APs may be the same as the beam sweep APs determined in S3125, and the network may not generate the first beam sweep request message.

The network can transmit a first beam sweep request message to the serving AP (S3135). The serving AP can receive the first beam sweep request message from the network (S3135). The serving AP can perform a beam sweep (S3145). The serving AP can perform the beam sweep based on information about a beam sweep range included in the first beam sweep request message. The serving AP can perform the beam sweep in a limited range. The serving AP can perform the beam sweep in the mmWave/THz band. If the first beam sweep request message is not generated in S3130, steps S3135 and S3145 can be omitted.

The network can transmit a second beam sweep request message to the first beam sweep APs (S3140). The first beam sweep APs can receive the second beam sweep request message from the network (S3140). The first beam sweep APs can perform a beam sweep (S1350). The first beam sweep APs can perform the beam sweep based on information about a beam sweep range included in the second beam sweep request message. The first beam sweep APs can perform the beam sweep in a limited range. The first beam sweep APs can perform the beam sweep in a mmWave/THz band.

FIG. 32 is a flowchart of a beam search method according to another embodiment of the present disclosure.

Referring to FIG. 32, the terminal may select a serving AP and preferred APs among a plurality of APs (S3205). The serving AP may be an optimal AP. The preferred APs may be APs preferred by the terminal. The terminal may receive SSB and measurement reference signals from the plurality of APs. The measurement reference signals may be pre-scheduled. The terminal may measure RSRP of SSBs. The terminal may select an AP that transmits a signal having the largest RSRP measurement value among the plurality of APs as a serving AP. The terminal may know the location of the pre-scheduled resource based on the location of the SSB resource transmitted by the serving AP. The relationship between the location of the SSB resource and the location of the pre-scheduled resource may be preset in the standard and may be known to the terminal in advance. The terminal may receive reference signals from some of the plurality of APs through the pre-scheduled resources. Here, some of the plurality of APs may be APs located around the serving AP among the plurality of APs that transmitted the SSB. The terminal can select preferred APs by performing measurements on reference signals.

The terminal can transmit Msg3 including information about preferred APs to the serving AP (S3210). The terminal can transmit a random access request message to the serving AP and, in response thereto, receive a random access response message from the serving AP. The terminal can transmit Msg3 including information about preferred APs in response to the random access response message. The terminal can transmit information about preferred APs to the serving AP in the B6G band.

The serving AP can receive Msg3 including information about preferred APs from the terminal (S3210). The serving AP can receive information about preferred APs in the B6G band from the terminal.

The serving AP can obtain the location information of the terminal (S3215). The serving AP can obtain the location information of the terminal based on the location of the serving AP and the locations of the preferred APs. The location information of the terminal may be approximate location information of the terminal.

The serving AP can determine beam sweep APs and beam sweep ranges (S3220). The serving AP can determine beam sweep APs based on the location information of the terminal acquired in S3215. Here, the beam sweep APs can include at least one of a plurality of APs. In addition, the serving AP can determine the beam sweep ranges of the beam sweep APs based on the location information of the terminal.

The serving AP may generate a beam sweep request message (S3225). The beam sweep request message may include information about the beam sweep range of the first beam sweep APs. Here, the first beam sweep APs may be APs excluding the serving AP among the beam sweep APs determined in step S3220. If the serving AP is not included in the beam sweep APs determined in S3220, the first beam sweep APs may be the same as the beam sweep APs determined in S3120. The beam sweep request message may include information about the beam sweep range of the first beam sweep APs determined in S3220.

The serving AP can transmit a beam sweep request message to the first beam sweep APs (S3230). The serving AP can transmit the beam sweep request message to the first beam sweep APs via the Xn interface.

The first beam sweep APs can receive a beam sweep request message from the serving AP (S3230). The first beam sweep APs can receive the beam sweep request message from the serving AP through the Xn interface.

The serving AP can perform beam sweep (S3235). The serving AP can perform beam sweep based on information about the beam sweep range determined in S3220. The serving AP can perform beam sweep in a limited range. The serving AP can perform beam sweep in the mmWave/THz band. If the serving AP is not included in the beam sweep APs determined in S3220, step S3235 may be omitted.

The first beam sweep APs can perform a beam sweep (S3240). The first beam sweep APs can obtain information about a beam sweep range from a beam sweep request message. The first beam sweep APs can perform a beam sweep based on the information about the beam sweep range. The first beam sweep APs can perform a beam sweep in a limited range. The first beam sweep APs can perform a beam sweep in a mmWave/THz band.

Figures 31 and 32 are procedures that are distinguished based on whether there is a network (e.g., CPU) that controls the entire AP or whether each AP has a certain processing capability and is capable of local processing. In the former case, the network performs the necessary processing, controls each AP, and transmits the necessary information, so there is an advantage that the structure of each AP is simple, but since all procedures first transmit information to the CPU, and then the CPU performs the processing, and then the information and operation instructions are transmitted to each AP again, there may be a delay. On the other hand, in the latter case, the delay in information transmission is reduced, but the processing capability required for each AP is increased, so the complexity of the AP may increase.

The locations of the pre-scheduled resources proposed in this disclosure may be predefined based on the SSB of the first AP (i.e., the serving AP). However, the number of APs around the first AP that the terminal should measure may vary depending on the environment in which the APs are installed. Therefore, a method for signaling the number of APs that the terminal should measure is required. The relevant information can be included in the SIB (system information block), but in this case, the terminal must decode the SIB to measure the resources, which causes a time delay in waiting for the next frame after receiving the SSB. In addition, in the case of the MIB (master information block) transmitted in the PBCH, the capacity may be insufficient because the number of reserved bits is 1 bit in the current NR standard. In this disclosure, a method for signaling the number of resources to be measured without affecting existing terminals is proposed.

FIG. 33 is a diagram illustrating an example of a signaling method according to one embodiment of the present disclosure.

Figure 33 illustrates a method for signaling the number of resources using phase modulation proposed in the present disclosure. SSB defined in 3GPP NR includes PSS, SSS and PBCH. The present invention proposes a method for signaling the number of resources by applying phase modulation to SSS.

If the transmitter applies phase modulation to the SSS and transmits it, the receiver can obtain the phase value multiplied by the SSS by calculating the phase difference between the SSS and the PSS. If the channel is maintained the same within the SSB, that is, if the phases of the PSS and the SSS by the channel are the same, the phase difference between the PSS and the SSS can be the phase value multiplied by the SSS.

For example, when signaling using the phase difference between PSS and SSS, the signaling value can be expressed as in Table 6 below.

The above embodiment operates only when it is assumed that the channels experienced by PSS and SSS are the same. However, even if the actual transmission channels experienced by PSS and SSS are the same, the channels of PSS and SSS received by the terminal are not the same. The reason is because of the physical cell ID transmitted using PSS and SSS. PSS transmits one of cell group 0, 1, and 2 values, and SSS transmits a value between 0 and 335.

Therefore, in the case of PSS, there is a high probability that the same value is being used in adjacent cells, and accordingly, the channel experienced by PSS appears to have more multipath components than SSS. For this reason, the assumption that PSS and SSS experienced the same channel does not hold true, and when restoring the phase value multiplied to SSS from the phase difference between SSS and PSS, performance degradation may occur.

In addition, if there is a residual frequency offset in the received signal, there is a problem that the phase due to this frequency offset and the phase multiplied during transmission cannot be separated. To solve this problem, in the embodiment, phase modulation can be applied to the entire PBCH. This is described in detail as follows.

FIG. 34 is a diagram illustrating an example of a signaling method according to another embodiment of the present disclosure.

If the phase value multiplied to the PBCH is θ and the phase difference between OFDM symbols due to the residual frequency offset is θo, the phase difference between the SSS and the DMRS of the PBCH part 1 can be θo-θ. Also, the phase difference between the PBCH part 2 and the SSS can be θo+θ. When the difference between the two phase differences is obtained, the residual frequency offset θo disappears and only 2θ, which is a phase-modulated component of the PBCH, remains.

For example, when signaling using the phase difference between PBCH and SSS, the signaling value can be expressed as in Table 7 below.

The phase component θ multiplied to the PBCH is multiplied to the entire PBCH, so the phase component by θ is also reflected in the channel estimated from the DMRS of the PBCH, and since the PBCH is decoded using the estimated channel, existing receivers may not be affected.

FIG. 35 is a flowchart of a beam search method according to one embodiment of the present disclosure.

In FIG. 35, the first device may be the serving AP described above, and the second device may be the preferred AP described above.

Referring to FIG. 35, the terminal can receive first reference signals (S3510). The terminal can receive first reference signals from each of the plurality of devices. The first reference signals can include SSB and a pre-scheduled measurement reference signal.

The terminal may select a first device based on the first reference signals (S3520). The terminal may select a first device among a plurality of devices. The terminal may perform measurements for the first reference signals. The terminal may select the first device based on the measurement value. For example, the terminal may measure RSRP for the first reference signals. The terminal may select a device that transmits a first reference signal having the largest RSRP value among the plurality of devices as the first device.

The terminal can obtain SSB (S3530). The terminal can obtain SSB based on the first reference signal received from the first device among the first reference signals obtained in step S3510.

In one embodiment, the SSB may include PSS, SSS and PBCH. The SSS may be phase modulated.

In another embodiment, the SSB may include a PSS, an SSS, a first PBCH and a second PBCH. The phase difference of the first PBCH and the second PBCH may be related to a phase modulation value of the first PBCH or the second PBCH.

The terminal can obtain information about pre-scheduled resources based on SSB (S3530).

In one embodiment, the terminal can obtain a PSS, an SSS and a PBCH from an SSB, obtain a phase difference value between the PSS and the SSS, obtain a phase modulation value of the PBCH based on the phase difference value, and obtain information about the number of the pre-scheduled resources based on the phase modulation value.

In another embodiment, the terminal may obtain the PSS, the SSS, the first PBCH and the second PBCH from the SSB, obtain a phase difference value of the DMRS of the first PBCH and the DMRS of the second PBCH, and obtain information about the number of pre-scheduled resources based on the phase difference value.

The terminal may select second devices (S3540). The terminal may select second devices from among a plurality of devices. The terminal may select at least one second device based on information about pre-scheduled resources acquired in S3530. The terminal may receive second reference signals from the plurality of devices through the pre-scheduled resources. The terminal may perform measurement on the second reference signals. The terminal may select second devices from among the plurality of devices based on a result of the measurement. For example, the terminal may measure RSRP or ToA of the second reference signals and select second devices from among the plurality of devices based on the measurement value.

The terminal can transmit information about the second devices to the first device (S3550). The terminal can transmit information about the second devices selected in S3540 to the first device. The terminal can transmit a random access request message to the first device, receive a random access response message from the first device, transmit Msg3 including information about the second devices to the first device, and receive Msg4 from the first device.

FIG. 36 is a flowchart of a beam search method according to another embodiment of the present disclosure.

In FIG. 36, the first device may be the serving AP described above, the second device may be the preferred AP described above, and the third device may be a beam sweep AP.

The first device can transmit a reference signal to the terminal (S3610). The first device can transmit the reference signal to the terminal in a first band. The first band may be a B6G band. In one embodiment, the reference signal may include an SSB composed of a PSS, an SSS, and a PBCH, and the SSS may be phase modulated. In another embodiment, the reference signal may include an SSB composed of a PSS, an SSS, a first PBCH, and a second PBCH, and a phase difference between a DMRS of the first PBCH and a DMRS of the second PBCH may be related to a phase modulation value of the first PBCH or the second PBCH.

The first device can receive information about the second devices from the terminal (S3620). The information about the second devices can include location information of the second devices. The first device can receive a random access request message from the terminal over the first band, transmit a random access response message to the terminal over the first band, and receive Msg3 including information about the second devices from the terminal over the first band.

The first device can select third devices and determine beam sweep ranges of the third devices (S3630). The first device can obtain location information of the terminal based on location information of the first device and location information of the second devices. Here, the location information of the terminal may be approximate location information of the terminal. The first device can select third devices based on the location information of the terminal. The first device can determine beam sweep ranges of the third devices based on the location information of the terminal.

The first device can determine whether the third devices include the first device (S3640). If the third devices include the first device (example of S3640), the first device can transmit a beam sweep request message to the third devices (S3650). The first device can generate a beam sweep request message including information about the beam sweep range determined in S3630. The first device can transmit the beam sweep request message to the third devices. The first device can transmit the beam sweep request message to the third devices via the Xn interface.

The first device can perform a beam sweep based on the beam sweep range determined in S3630 (3660). The first device can perform the beam sweep in a second band. The second band can include at least one of a mmWave band or a THz band.

If the third device does not include the first device (NO of S3640), the first device can transmit a beam sweep request message to the third devices (S3670). The first device can generate a beam sweep request message including information about the beam sweep range determined in S3630. In this case, the first device may not perform a separate beam sweep. The first device can transmit the beam sweep request message to the third devices. The first device can transmit the beam sweep request message to the third devices via the Xn interface.

The contents discussed above can be applied in combination with the embodiments proposed in this specification to be described later, or can be supplemented to clarify the technical features of the embodiments proposed in this specification. The embodiments described below are distinguished only for the convenience of explanation, and it goes without saying that some components of one embodiment can be substituted for some components of another embodiment, or can be applied in combination with each other.

The embodiments described above are combinations of the components and features of the present specification in a given form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, it is also possible to combine some components and/or features to form an embodiment of the present specification. The order of the operations described in the embodiments of the present specification may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment. It is obvious that claims that do not have an explicit citation relationship in the scope of the patent may be combined to form an embodiment or may be included as a new claim by post-application amendment.

Embodiments according to the present specification may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In case of hardware implementation, an embodiment of the present invention may be implemented by one or more ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present specification may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory and may be driven by a processor. The memory may be located inside or outside the processor and may exchange data with the processor by various means already known.

It will be apparent to those skilled in the art that this specification may be embodied in other specific forms without departing from the essential characteristics of this specification. Accordingly, the above detailed description should not be construed in all respects as restrictive but as illustrative. The scope of this specification should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalency range of this specification are intended to be included in the scope of this specification.

Claims (16)

In a method for operating a user equipment (UE) in a wireless communication system, A step of receiving a first reference signal from a plurality of devices; A step of selecting a first device among the plurality of devices by performing measurements on the first reference signals; A step of obtaining a SSB (Synchronization Signal Block) based on a first reference signal received from the first device among the first reference signals; A step of obtaining information about pre-scheduled resources based on the above SSB; A step of selecting second devices among the plurality of devices based on information about the pre-scheduled resources; and A method comprising the step of transmitting information about the second devices to the first device. In the first paragraph, The step of obtaining information about the pre-scheduled resources based on the above SSB is: A step of obtaining a PSS (Primary Synchronization Signal), an SSS (Secondary Synchronization Signal) and a PBCH (Physical Broadcast Channel) from the above SSB; A step of obtaining a phase difference value between the above PSS and the above SSS; A step of obtaining a phase modulation value of the PBCH based on the phase difference value; and A method comprising the step of obtaining information about the number of the pre-scheduled resources based on the phase modulation value. In the first paragraph, The step of obtaining information about the pre-scheduled resources based on the above SSB is: A step of obtaining a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a first physical broadcast channel (PBCH) and a second PBCH from the above SSB; A step of obtaining a phase difference value of the DMRS (Demodulation Reference Signal) of the first PBCH and the DMRS of the second PBCH; and A method comprising the step of obtaining information about the number of the pre-scheduled resources based on the phase difference value. In the first paragraph, The step of selecting the second devices among the plurality of devices based on information about the pre-scheduled resources is: A step of receiving a second reference signal through the pre-scheduled resources from the plurality of devices; A step of performing measurements on the above second reference signals; and A method comprising the step of selecting the second devices among the plurality of devices based on the results of performing measurements on the second reference signals. In the first paragraph, The step of transmitting information about the second devices to the first device comprises: A step of transmitting a random access request message to the first device; A step of receiving a random access response message from the first device; and A method comprising the step of transmitting Msg3 including information about the second devices to the first device. In a terminal (User equipment, UE) operating in a wireless communication system, One or more transmitters and receivers; one or more processors controlling said one or more transceivers; and A memory comprising one or more instructions to be performed by said one or more processors, One or more of the above commands, A step of receiving a first reference signal from a plurality of devices; A step of selecting a first device among the plurality of devices by performing measurements on the first reference signals; A step of obtaining a SSB (Synchronization Signal Block) based on a first reference signal received from the first device among the first reference signals; A step of obtaining information about pre-scheduled resources based on the above SSB; A step of selecting second devices among the plurality of devices based on information about the pre-scheduled resources; and A terminal comprising a step of transmitting information about the second devices to the first device. In a method of operating a first device in a wireless communication system, A step of transmitting a reference signal to a user equipment (UE) in a first band; A step of receiving information about second devices from the terminal in the first band; A step of obtaining location information of the terminal based on the location of the first device and the locations of the second devices; A step of determining third devices and beam sweep ranges of the third devices based on the location information of the terminal; and A method comprising the step of transmitting a beam sweep request message including information regarding the beam sweep range to the third devices. In Article 7, The above reference signal is, It includes a Synchronization Signal Block (SSB) consisting of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), and a Physical Broadcast Channel (PBCH), The above SSS is a method in which phase modulation is performed. In Article 7, The above reference signal is, It includes a SSB (Synchronization Signal Block) consisting of a PSS (Primary Synchronization Signal), an SSS (Secondary Synchronization Signal), a first PBCH (Physical Broadcast Channel) and a second PBCH, A method wherein the phase difference between the DMRS (Demodulation Reference Signal) of the first PBCH and the DMRS of the second PBCH is related to the phase modulation value of the first PBCH or the second PBCH. In Article 7, The step of receiving information about the second devices from the terminal in the first band is: A step of receiving a random access request message from the terminal in the first band; A step of transmitting a random access response message to the terminal in the first band; and A method comprising the step of receiving, from the terminal, Msg3 including information about the second devices in the first band. In Article 7, If the first device is included in the third devices, The step of transmitting the beam sweep request message including information about the beam sweep range to the third devices is: A step of transmitting the beam sweep request message including information about the beam sweep range to the remaining third devices among the third devices excluding the first device; and A method comprising the step of performing a beam sweep in a second band based on the determined beam sweep range. In Article 11, A method wherein the first band includes a B6G (Below ^6th generation, Below 6G) band, and the second band includes at least one of a mmWave band or a THz (TeraHertz) band. In Article 7, The step of transmitting the beam sweep request message including information about the beam sweep range to the third devices is: A method comprising the step of transmitting the beam sweep request message to the third devices via the Xn interface. In a first device operating in a wireless communication system, One or more transmitters and receivers; one or more processors controlling said one or more transceivers; and A memory comprising one or more instructions to be performed by said one or more processors, One or more of the above commands, A step of transmitting a reference signal to a user equipment (UE) in a first band; A step of receiving information about second devices from the terminal in the first band; A step of obtaining location information of the terminal based on the location of the first device and the locations of the second devices; A step of determining third devices and beam sweep ranges of the third devices based on the location information of the terminal; and A first device comprising a step of transmitting a beam sweep request message including information regarding the beam sweep range to the third devices. In a first node comprising one or more memories and one or more processors functionally connected to the one or more memories, The one or more processors are configured such that the first node, Receive a first reference signal from multiple devices, Selecting a first device among the plurality of devices by performing measurements on the above first reference signals, Obtaining an SSB (Synchronization Signal Block) based on the first reference signal received from the first device among the first reference signals, Obtain information about pre-scheduled resources based on the above SSB, Selecting second devices among the plurality of devices based on information about the above pre-scheduled resources, and A first node operative to transmit information about said second devices to said first device. In one or more non-transitory computer-readable media storing one or more instructions, Receive a first reference signal from multiple devices, Selecting a first device among the plurality of devices by performing measurements on the above first reference signals, Obtaining an SSB (Synchronization Signal Block) based on the first reference signal received from the first device among the first reference signals, Obtain information about pre-scheduled resources based on the above SSB, Selecting second devices among the plurality of devices based on information about the above pre-scheduled resources, and A computer-readable medium operable to transmit information about said second devices to said first device.

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