HK40009728B - Method and apparatus for transmitting/receiving random access preamble - Google Patents

Description

Method and apparatus for transmitting/receiving a random access preamble

Technical Field

The present invention relates to a wireless communication system, and more particularly to a method and apparatus for transmitting/receiving a random access preamble.

Background Art

With the advent and widespread adoption of machine-to-machine (M2M) communications, various devices such as smartphones and tablets, and technologies requiring large amounts of data transmission, the data throughput required in cellular networks has rapidly increased. To meet this rapid growth, technologies such as carrier aggregation (CA) to efficiently utilize more frequency bands and cognitive radio have been developed. Furthermore, technologies such as multiple-input, multiple-output (MIMO) and multi-base station (BS) collaboration have been developed to increase the data capacity transmitted using limited frequency resources.

Typical wireless communication systems transmit and receive data using a downlink (DL) frequency band and an uplink (UL) frequency band corresponding to the DL frequency band (in frequency division duplex (FDD) mode), or divide a specified radio frame into UL time units and DL time units in the time domain, and then transmit and receive data using the UL/DL time units (in time division duplex (TDD) mode). Base stations (BSs) and user equipment (UEs) transmit and receive data and/or control information scheduled on a specified time unit basis, such as a subframe basis. Data is transmitted and received using the data region allocated within the UL/DL subframe, and control information is transmitted and received using the control region allocated within the UL/DL subframe. To this end, various physical channels carrying radio signals are arranged within the UL/DL subframe. In contrast, carrier aggregation technology utilizes a wider UL/DL bandwidth by aggregating multiple UL/DL frequency blocks, thereby utilizing a wider frequency band and enabling the simultaneous processing of more signals than when using a single carrier.

Furthermore, the communication environment has evolved to increase the density of user-accessible nodes at the periphery of the network. A node is a fixed point capable of transmitting and receiving radio signals to and from a user equipment (UE) via one or more antennas. A communication system with a high density of nodes can provide improved communication services to UEs through collaboration between nodes.

As more and more communication devices require higher communication capacity, there is a need for enhanced mobile broadband (eMBB) communications compared to traditional radio access technologies (RATs). Furthermore, massive machine-type communications (mMTC), which connects multiple devices and objects to provide a variety of services anytime and anywhere, is a major issue to consider in next-generation communications.

Furthermore, discussions are underway to design communication systems that take into account services and UEs that are sensitive to reliability and latency. The introduction of next-generation RATs has been discussed, considering eMBB communication, mMTC, and ultra-reliable and low-latency communication (URLLC).

Summary of the Invention

Technical issues

With the introduction of new radio communication technologies, the number of user equipments (UEs) that a BS should provide services to in a specified resource area has increased, and the amount of data and control information that the BS should transmit to the UEs has also increased. Since the amount of radio resources available for communication between the BS and the UEs is limited, a new method is needed for the BS to efficiently receive/transmit uplink/downlink data and/or uplink/downlink control information using the limited radio resources.

As technology evolves, overcoming latency has become a significant challenge. Applications whose performance is heavily dependent on latency are increasing. Therefore, a method is needed to reduce latency compared to traditional systems.

Also, with the development of smart devices, a new scheme for efficiently transmitting/receiving a small amount of data or efficiently transmitting/receiving data occurring at a low frequency is required.

In addition, a signal transmission/reception method is required in a system supporting a new radio access technology (NR) using a high frequency band.

The technical objectives that can be achieved by the present invention are not limited to those specifically described above, and those skilled in the art will more clearly understand other technical objectives not described herein from the detailed description below.

Technical Solution

According to one aspect of the present disclosure, a method for transmitting a random access channel (RACH) preamble by a user equipment in a wireless communication system is provided. The method includes: generating a RACH preamble; and transmitting the RACH preamble. The length N _RA of the RACH preamble is equal to the total length of an orthogonal frequency division multiplexing (OFDM) symbol used to transmit the RACH preamble, and the RACH preamble includes a sequence portion having a length N _SEQ = N _u *n and a cyclic prefix (CP) having a length N _CP,RA , where N _SEQ and N _CP,RA satisfy N _CP,RA + N _SEQ = N _RA . The sequence portion includes n preambles, each preamble having a length N _u , and n is a positive integer.

According to another aspect of the present invention, a method for receiving a random access channel (RACH) preamble by a base station in a wireless communication system is provided. The method includes: transmitting RACH preamble configuration information; and receiving the RACH preamble according to the RACH preamble configuration information. The length N _RA of the RACH preamble is equal to the total length of an orthogonal frequency division multiplexing (OFDM) symbol used to receive the RACH preamble. The RACH preamble includes a sequence portion having a length N _SEQ = N _u *n and a cyclic prefix (CP) having a length N CP _,RA , satisfying N _CP,RA + N _SEQ = N _RA . The sequence portion includes n preambles, each having a length N _u , where n is a positive integer.

According to another aspect of the present invention, a user equipment for transmitting a random access channel (RACH) preamble in a wireless communication system is provided. The user equipment includes a radio frequency (RF) unit and a processor configured to control the RF unit. The processor can be configured to: generate a RACH preamble; and control the RF unit to transmit the RACH preamble. The length N _RA of the RACH preamble is equal to the total length of an orthogonal frequency division multiplexing (OFDM) symbol used to transmit the RACH preamble, and the RACH preamble includes a sequence portion having a length N _SEQ =N _u *n and a cyclic prefix (CP) having a length N _CP,RA , where N _SEQ and N _CP,RA satisfy N _CP,RA +N _SEQ =N _RA . The sequence portion includes n preambles, each preamble having a length N _u , and n is a positive integer.

According to another aspect of the present invention, a base station for receiving a random access channel (RACH) preamble in a wireless communication system is provided. The base station includes a radio frequency (RF) unit and a processor configured to control the RF unit. The processor is configured to: control the RF unit to transmit RACH preamble configuration information; and control the RF unit to receive the RACH preamble based on the RACH preamble configuration information. The length N _RA of the RACH preamble is equal to the total length of an orthogonal frequency division multiplexing (OFDM) symbol used to receive the RACH preamble, and the RACH preamble includes a sequence portion having a length N _SEQ = _Nu *n and a cyclic prefix (CP) having a length N _CP , _RA , where N SEQ and N _CP,RA satisfy N _CP,RA + N _SEQ = N _RA . The sequence portion includes n preambles, each having a length N _u , and n is a positive integer.

In each aspect of the present invention, the RACH preamble may span an OFDM symbol in the time domain from the beginning to the end of the OFDM symbol.

In each aspect of the present invention, _Nu may be a fixed value.

In each aspect of the present invention, a RACH preamble may be generated to conform to a random access preamble format.

In each aspect of the present invention, information indicating a random access preamble format may be provided from a base station to a user equipment.

In each aspect of the present invention, the wireless communication system may be a system capable of applying beamforming per OFDM symbol.

In each aspect of the present invention, a RACH preamble can be transmitted/received on a cell operating in a high frequency band.

The above technical solutions are only part of the embodiments of the present invention. Those skilled in the art can derive and understand various embodiments including the technical features of the present invention from the following detailed description of the present invention.

Beneficial effects

According to the present invention, radio communication signals can be efficiently transmitted/received, thereby improving the overall throughput of the radio communication system.

According to embodiments of the present invention, delay/latency occurring during communication between user equipment and a base station can be reduced.

Furthermore, due to the development of smart devices, not only a small amount of data but also data that occurs infrequently can be efficiently sent/received.

Furthermore, signals can be transmitted/received in a system supporting a new radio access technology.

Those skilled in the art will understand that the effects that can be achieved through the present invention are not limited to the contents specifically described above, and other advantages of the present invention will be more clearly understood from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

FIG1 illustrates a random access preamble format in a conventional LTE/LTE-A system.

FIG2 illustrates a time slot structure available in the new radio access technology (NR).

FIG3 abstractly illustrates the hybrid beamforming structure in terms of a transceiver unit (TXRU) and physical antennas.

FIG4 illustrates a cell of a New Radio Access Technology (NR) system.

FIG5 illustrates transmission of a synchronization signal (SS) block and RACH resources linked to the SS block.

FIG6 illustrates the configuration/format and receiver functionality of a random access channel (RACH) preamble.

FIG7 illustrates a receive (Rx) beam formed at a gNB to receive a RACH preamble.

FIG8 shows a RACH signal and RACH resources for explaining terms used to describe the present invention.

FIG9 illustrates an example of a RACH resource set.

FIG. 10 shows boundary alignment of RACH resources according to the present invention.

FIG11 illustrates a method of configuring a mini-slot in a RACH time slot SLOT _RACH when BC is valid.

FIG12 illustrates another method of configuring mini-slots within the RACH slot SLOT _RACH when BC is valid.

FIG13 illustrates a method of configuring mini-slots within the RACH slot SLOT _RACH when beam correspondence (BC) is not valid.

FIG14 illustrates a method of configuring mini-slots using guard time.

FIG. 15 shows an example of transmitting data by performing mini-slot concatenation of the same length as a normal slot when BC is valid.

FIG. 16 is a block diagram showing elements of the transmitting device 10 and the receiving device 20 for implementing the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The detailed description given below with reference to the accompanying drawings is intended to explain exemplary embodiments of the present invention, rather than to illustrate the only embodiment that can be implemented according to the present invention. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without these specific details.

In some cases, known structures and devices are omitted or shown in block diagram form, focusing on important features of the structures and devices, so as not to obscure the concept of the present invention. The same reference numerals will be used throughout the specification to represent the same or similar parts.

The following techniques, devices, and systems can be applied to various wireless multiple access systems. Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and multi-carrier frequency division multiple access (MC-FDMA) systems. CDMA can be implemented by radio technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented by radio technologies such as Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), or Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented by radio technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) that uses E-UTRA. 3GPP LTE uses OFDMA in the DL and SC-FDMA in the UL. Advanced LTE (LTE-A) is an evolved version of 3GPP LTE. For ease of description, it is assumed that the present invention is applied to a 3GPP-based communication system, such as LTE/LTE-A, NR. However, the technical features of the present invention are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP LTE/LTE-A/NR system, aspects of the present invention that are not specific to 3GPP LTE/LTE-A/NR may be applied to other mobile communication systems.

For example, the present invention is applicable to contention-based communications such as Wi-Fi, as well as non-contention-based communications such as in 3GPP LTE/LTE-A systems, in which an eNB allocates downlink (DL)/ultra-high (UL) time/frequency resources to a UE, and the UE receives DL signals and transmits UL signals based on the eNB's resource allocation. In non-contention-based communications, an access point (AP) or a control node controlling the AP allocates resources for communication between the UE and the AP, while in contention-based communications, communication resources are occupied through contention between UEs seeking access to the AP. Contention-based communications will now be briefly described. One contention-based communications scheme is Carrier Sense Multiple Access (CSMA). CSMA refers to a probabilistic medium access control (MAC) protocol used to confirm the absence of other traffic on a shared transmission medium, such as a frequency band (also known as a shared channel), before a node or communication device transmits traffic on the same shared transmission medium. In CSMA, a transmitting device determines whether another transmission is in progress before attempting to transmit traffic to a receiving device. In other words, the transmitting device attempts to detect the presence of a carrier from another transmitting device before attempting to transmit. Once a carrier is sensed, a transmitting device waits for another transmitting device in the process to complete its transmission before executing its own transmission. Therefore, CSMA can be used as a communication scheme based on the "sense before sending" or "listen before talking" principle. Schemes for avoiding collisions between transmitting devices in contention-based communication systems using CSMA include Carrier Sense Multiple Access with Collision Detection (CSMA/CD) and/or Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). CSMA/CD is a collision detection scheme in wired local area network (LAN) environments. In CSMA/CD, a personal computer (PC) or server wishing to communicate in an Ethernet environment first confirms whether communication is occurring on the network. If another device is carrying data on the network, the PC or server waits before sending the data. In other words, when two or more users (e.g., PCs, UEs, etc.) transmit data simultaneously, collisions occur between simultaneous transmissions, and CSMA/CD is a scheme for flexibly transmitting data by monitoring for collisions. Transmitting devices using CSMA/CD adjust their data transmissions by using specific rules to monitor data transmissions performed by another device. CSMA/CA is a MAC protocol specified in the IEEE 802.11 standard. A wireless LAN (WLAN) system that complies with the IEEE 802.11 standard does not use CSMA/CD, which has been used in the IEEE 802.3 standard, but uses CA, that is, a collision avoidance scheme. A transmitting device always monitors the carrier of the network, and if the network is empty, the transmitting device waits for a determined time according to its position in the registered list, and then sends data. Various methods are used to determine the priority of the transmitting devices in the list and reconfigure the priority. In a system according to some versions of the IEEE 802.11 standard, a collision may occur, and in this case, a collision monitoring process is performed. A transmitting device using CSMA/CA uses specific rules to avoid collisions between its data transmission and the data transmission of another transmitting device.

In the embodiments of the present invention described below, the term "assume" may mean that a subject transmitting a channel transmits the channel according to a corresponding "assumption." This may also mean that, assuming that the channel has been transmitted according to the "assumption," a subject receiving the channel receives or decodes the channel in a form that conforms to the "assumption."

In the present invention, puncturing a channel on specific resources means mapping the channel's signal to specific resources during the channel's resource mapping process, but a portion of the signal mapped to the punctured resource is excluded from the transmitted channel. In other words, the specific resources punctured during the channel's resource mapping process are counted as resources used for the channel, and the signal mapped to the specific resource among the channel's signals is not actually transmitted. Assuming that the signal mapped to the specific resource is not transmitted, the receiver of the channel receives, demodulates, or decodes the channel. On the other hand, rate matching of a channel on specific resources means that the channel is never mapped to a specific resource during the channel's resource mapping process, and therefore the specific resource is not used for transmission of the channel. In other words, the specific resources for rate matching during the channel's resource mapping process are not counted as resources used for the channel. Assuming that the specific rate matching resource is not used for mapping and transmission of the channel, the receiver of the channel receives, demodulates, or decodes the channel.

In the present invention, a user equipment (UE) can be a fixed or mobile device. Examples of UEs include various devices that transmit and receive user data and/or various control information to and from a base station (BS). A UE can be referred to as a terminal equipment (TE), mobile station (MS), mobile terminal (MT), user terminal (UT), subscriber station (SS), wireless device, personal digital assistant (PDA), wireless modem, handheld device, etc. Furthermore, in the present invention, a BS generally refers to a fixed station that communicates with a UE and/or another BS and exchanges various data and control information with the UE and another BS. A BS can be referred to as an advanced base station (ABS), a Node B (NB), an evolved Node B (eNB), a base transceiver system (BTS), an access point (AP), a processing server (PS), etc. Specifically, a BS for UTRAN is referred to as a Node B, a BS for E-UTRAN is referred to as an eNB, and a BS for a new radio access technology network is referred to as a gNB. In describing the present invention, a BS will be referred to as a gNB.

In this disclosure, a node refers to a fixed point capable of transmitting and receiving radio signals through communication with a UE. Regardless of the terminology, various types of gNBs can be used as nodes. For example, a base station (BS), node B (NB), eNode B (eNB), picocell eNB (PeNB), home eNB (HeNB), gNB, relay, repeater, etc. can be a node. Furthermore, the node may not be a gNB. For example, a node may be a radio remote head (RRH) or a radio remote unit (RRU). An RRH or RRU typically has a lower power level than a gNB. Since an RRH or RRU (hereinafter referred to as RRH/RRU) is generally connected to a gNB via a dedicated line such as an optical cable, cooperative communication between the RRH/RRU and the gNB can be performed more smoothly than cooperative communication between gNBs connected via radio lines. Each node is equipped with at least one antenna. An antenna can refer to a physical antenna, an antenna port, a virtual antenna, or an antenna group. A node may also be referred to as a point.

In this disclosure, a cell refers to a defined geographical area where one or more nodes provide communication services. Therefore, in this disclosure, communicating with a specific cell may mean communicating with a gNB or node providing communication services for the specific cell. Furthermore, DL/UL signals of a specific cell refer to DL/UL signals from/to the gNB or node providing communication services for the specific cell. A cell providing UL/DL communication services to a UE is specifically referred to as a serving cell. Furthermore, the channel status/quality of a specific cell refers to the channel status/quality of a channel or communication link established between the gNB or node providing communication services for the specific cell and the UE. In a 3GPP-based communication system, a UE can measure the DL channel status received from a specific node using the cell-specific reference signal (CRS) resources and/or the channel state information reference signal (CSI-RS) resources, which are assigned to the specific node via its antenna port and transmitted on the cell-specific reference signal (CRS) resources.

Meanwhile, a 3GPP-based communication system uses a concept of a cell in order to facilitate management of radio resources and cells associated with radio resources are distinguished from cells of a geographical area.

A "cell" of a geographical area can be understood as a coverage area in which a node can provide services using a carrier, and a "cell" of radio resources is associated with a bandwidth (BW) that is a frequency range configured by the carrier. Since the DL coverage, which is the range in which a node can send a valid signal, and the UL coverage, which is the range in which a node can receive a valid signal from a UE, depend on the carrier that carries the signal, the coverage area of the node can be associated with the coverage area of the "cell" of the radio resources used by the node. Therefore, the term "cell" may sometimes be used to indicate the service coverage area of a node, at other times may indicate a radio resource, or at other times may indicate a range in which a signal using a radio resource can reach with effective strength.

At the same time, the communication standard based on 3GPP uses the concept of cells to manage radio resources. A "cell" associated with radio resources is defined by a combination of downlink resources and uplink resources, that is, a combination of DL CCs and UL CCs. A cell can be configured by downlink resources only, or by downlink resources and uplink resources. If carrier aggregation is supported, the link between the carrier frequency of the downlink resources (or DL CC) and the carrier frequency of the uplink resources (or UL CC) can be indicated by system information. For example, the combination of DL resources and UL resources can be indicated by the link of System Information Block Type 2 (SIB2). The carrier frequency means the center frequency of each cell or CC. A cell operating on the primary frequency can be referred to as a primary cell (Pcell) or PCC, and a cell operating on a secondary frequency (or SCC) can be referred to as a secondary cell (Scell) or SCC. The carrier corresponding to the Pcell on the downlink will be referred to as the downlink primary CC (DL PCC), and the carrier corresponding to the Pcell on the uplink will be referred to as the uplink primary CC (UL PCC). An Scell refers to a cell that can be configured after a radio resource control (RRC) connection is established and used to provide additional radio resources. The Scell, together with the PCell, can form a group of serving cells for a UE based on the UE's capabilities. The carrier corresponding to the Scell on the downlink will be referred to as a downlink secondary CC (DL SCC), and the carrier corresponding to the Scell on the uplink will be referred to as an uplink secondary CC (UL SCC). While the UE is in the RRC-CONNECTED state, if the UE is not configured with carrier aggregation or does not support carrier aggregation, only a single serving cell configured by the PCell exists.

3GPP-based communication standards define DL physical channels corresponding to resource elements that carry information derived from higher layers, and DL physical signals corresponding to resource elements used by the physical layer but not carrying information derived from higher layers. For example, the physical downlink shared channel (PDSCH), physical broadcast channel (PBCH), physical multicast channel (PMCH), physical control format indicator channel (PCFICH), physical downlink control channel (PDCCH), and physical hybrid ARQ indicator channel (PHICH) are defined as DL physical channels, and reference signals and synchronization signals are defined as DL physical signals. Reference signals (RS), also known as pilots, are predefined signals with special waveforms known to both the base station and the user equipment terminal. For example, cell-specific RS (CRS), UE-specific RS (UE-RS), positioning RS (PRS), and channel state information RS (CSI-RS) can be defined as DL RS. Meanwhile, the 3GPP LTE/LTE-A standards define UL physical channels corresponding to resource elements that carry information derived from higher layers, and UL physical signals corresponding to resource elements used by the physical layer but not carrying information derived from higher layers. For example, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are defined as UL physical channels, and a demodulation reference signal (DMRS) for UL control/data signals and a sounding reference signal (SRS) for UL channel measurement are defined as UL physical signals.

In the present invention, the Physical Downlink Control Channel (PDCCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH), and Physical Downlink Shared Channel (PDSCH) refer to the time-frequency resources or resource element (RE) sets that carry downlink control information (DCI), the time-frequency resources or RE sets that carry control format indicators (CFI), the time-frequency resources or RE sets that carry downlink acknowledgements (ACK)/negative ACKs (NACKs), and the time-frequency resources or RE sets that carry downlink data, respectively. Furthermore, the Physical Uplink Control Channel (PUCCH), Physical Uplink Shared Channel (PUSCH), and Physical Random Access Channel (PRACH) refer to the time-frequency resources or RE sets that carry uplink control information (UCI), the time-frequency resources or RE sets that carry uplink data, and the time-frequency resources or RE sets that carry random access signals, respectively. In this invention, specifically, time-frequency resources or REs allocated to or belonging to the PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH are referred to as PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH REs or PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resources, respectively. Therefore, in this invention, a UE's PUCCH/PUSCH/PRACH transmission is conceptually the same as UCI/uplink data/random access signal transmission on PUSCH/PUCCH/PRACH, respectively. Furthermore, a gNB's PDCCH/PCFICH/PHICH/PDSCH transmission is conceptually the same as downlink data/DCI transmission on PDCCH/PCFICH/PHICH/PDSCH, respectively.

In the following, the OFDM symbols/subcarriers/REs to which or for which CRS/DMRS/CSI-RS/SRS/UE-RS are assigned or configured will be referred to as CRS/DMRS/CSI-RS/SRS/UE-RS symbols/carriers/subcarriers/REs. For example, the OFDM symbols to which or for which Tracking RS (TRS) is assigned or configured are referred to as TRS symbols, the subcarriers to which or for which TRS is assigned or configured are referred to as TRS subcarriers, and the REs to which or for which TRS is assigned or configured are referred to as TRS REs. In addition, the subframes configured for TRS transmission are referred to as TRS subframes. In addition, the subframes in which a broadcast signal is sent are referred to as broadcast subframes or PBCH subframes, and the subframes in which a synchronization signal (e.g., PSS and/or SSS) is sent are referred to as synchronization signal subframes or PSS/SSS subframes. The OFDM symbols/subcarriers/REs to which or for which PSS/SSS is assigned or configured are referred to as PSS/SSS symbols/subcarriers/REs, respectively.

In the present invention, CRS port, UE-RS port, CSI-RS port and TRS port refer to an antenna port configured to send CRS, an antenna port configured to send UE-RS, an antenna port configured to send CSI-RS and an antenna port configured to send TRS, respectively. Antenna ports configured to send CRS can be distinguished from each other by the position of RE occupied by CRS according to the CRS port, antenna ports configured to send UE-RS can be distinguished from each other by the position of RE occupied by UE-RS according to the UE-RS port, and antenna ports configured to send CSI-RS can be distinguished from each other by the position of RE occupied by CSI-RS according to the CSI-RS port. Therefore, the term CRS/UE-RS/CSI-RS/TRS port can also be used to indicate the pattern of RE occupied by CRS/UE-RS/CSI-RS/TRS in a predetermined resource area.

For terms and technologies not described in detail in the present invention, reference may be made to the standard documents of 3GPP LTE/LTE-A, for example, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.321, and 3GPP TS 36.331, and the standard documents of 3GPP NR, for example, 3GPP TS 38.211, 3GPP TS 38.212, 3GPP 38.213, 3GPP 38.214, 3GPP 38.215, 3GPP TS 38.321, and 3GPP TS 36.331.

In LTE/LTE-A systems, when a UE powers on or wishes to access a new cell, it performs an initial cell search procedure, which involves acquiring time and frequency synchronization with the cell and detecting the cell's physical layer cell _identity , ^NcellID . To this end, the UE may receive synchronization signals from the eNB, such as the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS), to establish synchronization with the eNB and obtain information such as the cell identity (ID). After the initial cell search procedure, the UE may perform a random access procedure to access the eNB. To this end, the UE may transmit a preamble via the Physical Random Access Channel (PRACH) and receive a response message to the preamble via the PDCCH and PDSCH. After performing the above procedures, the UE may perform PDCCH/PDSCH reception and PUSCH/PUCCH transmission as normal UL/DL signaling procedures. The random access procedure is also known as the Random Access Channel (RACH) procedure. The random access procedure is used for various purposes, including initial access, adjusting UL synchronization, resource allocation, and handover.

After transmitting the RACH preamble, the UE attempts to receive a random access response (RAR) within a preset time window. Specifically, in LTE/LTE-A systems, the UE attempts to detect a PDCCH with a random access radio network temporary identifier (RA-RNTI) (hereinafter, RA-RNTI PDCCH) within the time window (e.g., masking the CRC on the PDCCH with the RA-RNTI). Upon detecting the RA-RNTI PDCCH, the UE checks whether the PDSCH corresponding to the RA-RNTI PDCCH has a RAR pointing to it. The RAR includes timing advance (TA) information indicating timing offset information for UL synchronization, UL resource allocation information (UL grant information), and a temporary UE identifier (e.g., temporary cell-RNTI (TC-RNTI)). The UE can perform UL transmission (e.g., Msg3) based on the resource allocation information and TA value in the RAR. HARQ is applied to the UL transmission corresponding to the RAR. Therefore, after transmitting Msg3, the UE can receive reception response information (e.g., PHICH) corresponding to Msg3.

FIG1 illustrates a random access preamble format in a conventional LTE/LTE-A system.

In legacy LTE/LTE-A systems, a random access preamble (RACH preamble) consists of a cyclic prefix of length T _CP and a sequence portion of length T _SEQ in the physical layer. The parameter values T _CP and T _SEQ are listed in the table below and depend on the frame structure and random access configuration. Higher layers control the preamble format. In 3GPP LTE/LTE-A systems, PRACH configuration information is signaled via the cell's system information and mobility control information. The PRACH configuration information indicates the root sequence index, the cyclic shift unit N _CS of the Zadoff-Chu sequence, the length of the root sequence, and the preamble format to be used for the RACH procedure in the cell. In 3GPP LTE/LTE-A systems, the PRACH opportunity, which is the timing at which the preamble format and RACH preamble can be transmitted, is indicated by a PRACH configuration index, which is part of the RACH configuration information (see Section 5.7 of 3GPP TS 36.211 and "PRACH-Config" of 3GPP TS 36.331). The length of the Zadoff-Chu sequence used for the RACH preamble is determined according to the preamble format (refer to Table 4).

Table 1

Preamble format 0 1 2 3 4

In LTE/LTE-A systems, the RACH preamble is sent in the UL subframe. The transmission of the random access preamble is limited to certain time and frequency resources. These resources are called PRACH resources and are enumerated in increasing order of subframe number within the radio frame and PRB number in the frequency domain, so that index 0 corresponds to the lowest numbered PRB and subframe within the radio frame. The random access resources are defined according to the PRACH configuration index (refer to the standard document 3GPP TS 36.211). The PRACH configuration index is given by a higher layer signal (sent by the eNB).

The sequence portion of the RACH preamble (hereinafter, the preamble sequence) uses a Zadoff-Chu sequence. Preamble sequences used for the RACH are generated from a Zadoff-Chu sequence with a zero correlation zone, generated from one or more root Zadoff-Chu sequences. The network configures the set of preamble sequences that a UE is allowed to use. In conventional LTE/LTE-A systems, 64 preamble sequences are available in each cell. The set of 64 preamble sequences in a cell is found by first including all available cyclic shifts of the root Zadoff-Chu sequence with the logical index RACH_ROOT_SEQUENCE in order of increasing cyclic shifts, where RACH_ROOT_SEQUENCE is broadcast as part of the system information (for the corresponding cell). If all 64 preamble sequences cannot be generated from a single root Zadoff-Chu sequence, additional preamble sequences are obtained from root sequences with consecutive logical indices until all 64 preamble sequences are found. The logical root sequence order is cyclic: logical indices 0 to 837 are consecutive. For preamble formats 0 to 3 and 4, the relationship between the logical root sequence index and the physical root sequence index u is given in Table 2 and Table 3 respectively.

Table 2

Table 3

The u-th root Zadoff-Chu sequence is defined as follows.

Equation 1

The length N _ZC of the Zadoff-Chu sequence is given by the following table.

Table 4

Preamble format 0～3 839 4 139

Starting from the u-th root Zadoff-Chu sequence, a random access preamble with a zero correlation zone of length _NZC -1 is defined by a cyclic shift according to xu _,v (n)= _xu ((n+ _Cv ) _modNZC ), where the cyclic shift is given by the following equation.

Equation 2

For preamble formats 0 to 3, N _CS is given in Table 5. For preamble format 4, N _CS is given in Table 6.

Table 5

Table 6

zeroCorrelationZoneConfig 0 2 1 4 2 6 3 8 4 10 5 12 6 15 7 N/A 8 N/A 9 N/A 10 N/A 11 N/A 12 N/A 13 N/A 14 N/A 15 N/A

The parameter zeroCorrelationZoneConfig is provided by higher layers. The parameter High-speed-flag provided by higher layers determines whether the unrestricted set or the restricted set should be used.

The variable _du is a cyclic shift corresponding to a Doppler shift of magnitude 1/T _SEQ and is given by the following equation.

Equation 3

p is the smallest non-negative integer satisfying (pu) mod N _ZC = 1. The parameters of the restricted set of cyclic shifts depend on _du . For N _ZC ≤ _du < N _ZC /3, the parameters are given by the following equation.

Equation 4

For N _ZC /3≤d _u <(N _ZC −N _CS )/2, the parameters are given by the following formula.

Equation 5

For all other values of _du , there are no cyclic shifts in the restricted set.

A time-continuous random access signal s(t), which is a baseband signal of RACH, is defined by the following equation.

Equation 6

Where 0 ≤ t < T _SEQ - T _CP , β _PRACH is the amplitude scaling factor to comply with the transmit power P _PRACH specified in 3GPP TS 36.213, and k ₀ = n ^RA _PRB N ^RB _sc - N ^UL _RB N ^RB _sc /2. N ^RB _sc represents the number of subcarriers that make up one resource block (RB). ^{N UL} _RB represents the number of RBs in an UL slot and depends on the UL transmission bandwidth. The position in the frequency domain is controlled by the parameter n ^RA _PRB , which is derived from Section 5.7.1 of 3GPP TS 36.211. The factor K = Δf / Δf _RA accounts for the difference in subcarrier spacing between the random access preamble and uplink data transmission. The variable Δf _RA (the subcarrier spacing of the random access preamble) and the variable (the fixed offset that determines the frequency domain position of the random access preamble within the physical resource block) are given in the following table.

Table 7

In the LTE/LTE-A system, the subcarrier spacing Δf is 15 kHz or 7.5 kHz. However, as shown in Table 7, the subcarrier spacing Δf _RA of the random access preamble is 1.25 kHz or 0.75 kHz.

As more and more communication devices require higher communication capacity, mobile broadband must be enhanced compared to traditional radio access technology (RAT). In addition, large-scale machine type communication that provides various services regardless of time and place by connecting multiple devices and objects to each other is a major issue to be considered in the next generation of communications. In addition, the design of a communication system in which services/UEs that are sensitive to reliability and delay are taken into consideration is under discussion. The introduction of the next generation RAT has been discussed by considering enhanced mobile broadband communication, massive MTC, ultra-reliable and low-latency communication (URLLC), etc. In the current 3GPP, research on the next generation mobile communication system after EPC is underway. In the present invention, for convenience, the corresponding technology is referred to as new RAT (NR) or 5G RAT.

NR communication systems are required to support much better performance than traditional fourth-generation (4G) systems in terms of data rate, capacity, latency, energy consumption, and cost. Therefore, NR systems need to make progress in bandwidth, spectrum, energy, signaling efficiency, and cost per bit.

<OFDM parameter set>

New RAT systems use an OFDM transmission scheme or a similar transmission scheme. New RAT systems may use OFDM parameters that differ from those of LTE systems. Alternatively, New RAT systems may conform to the parameter sets of legacy LTE/LTE-A systems but may have a wider system bandwidth (e.g., 100 MHz) than legacy LTE/LTE-A systems. A cell can support multiple parameter sets. This means that UEs operating with different parameter sets can coexist within a cell.

<Subframe Structure>

In the 3GPP LTE/LTE-A system, the duration of a radio frame is 10ms ( _307,200Ts ). The radio frame is divided into 10 subframes of equal size. Subframe numbers can be assigned to the 10 subframes within a radio frame respectively. Here, _Ts represents the sampling time, where _Ts = 1/(2048×15kHz). Each subframe is 1ms long and is further divided into two time slots. In a radio frame, 20 time slots are numbered sequentially from 0 to 19. The duration of each time slot is 0.5ms. The time interval for transmitting a subframe is defined as the transmission time interval (TTI). Time resources can be distinguished by radio frame number (or radio frame index), subframe number (or subframe index), time slot number (or time slot index), etc. TTI refers to the interval in which data can be scheduled. For example, in the current LTE/LTE-A system, there is a transmission opportunity for UL grant or DL grant every 1ms, and there are several transmission opportunities for UL/DL grant in a time shorter than 1ms. Therefore, the TTI in the conventional LTE/LTE-A system is 1 ms.

FIG2 shows a time slot structure available in the new radio access technology (NR).

In order to minimize data transmission delay, in 5G new RAT, a time slot structure in which a control channel and a data channel are time-division multiplexed is considered.

In Figure 2, the shaded area indicates the transmission area of the DL control channel (e.g., PDCCH) carrying DCI, and the black area indicates the transmission area of the UL control channel (e.g., PUCCH) carrying UCI. DCI is control information sent by the gNB to the UE. DCI can include information about the cell configuration that the UE should be aware of, DL-specific information such as DL scheduling, and UL-specific information such as UL grants. UCI is control information sent by the UE to the gNB. UCI can include HARQ ACK/NACK reports for DL data, CSI reports on DL channel status, and scheduling requests (SRs).

In FIG2 , the symbol region from symbol index 1 to symbol index 12 can be used to transmit a physical channel carrying downlink data (e.g., PDSCH), or can be used to transmit a physical channel carrying uplink data (e.g., PUSCH). According to the slot structure of FIG2 , DL transmission and UL transmission can be performed sequentially in one slot, and thus, DL data transmission/reception and UL ACK/NACK reception/transmission for DL data can be performed in one slot. As a result, the time spent on retransmitting data when a data transmission error occurs can be reduced, thereby minimizing the delay in the final data transmission.

In this slot structure, switching from transmit mode to receive mode and vice versa for the gNB and UE requires time gaps. To facilitate this switching process, some OFDM symbols when switching from DL to UL in the slot structure are set as guard periods (GPs).

In conventional LTE/LTE-A systems, downlink control channels are time-division multiplexed with data channels, and the PDCCH, serving as a control channel, is transmitted across the entire system band. However, in new RATs, the bandwidth of a system is expected to be approximately a minimum of 100 MHz, and it is difficult to allocate control channels across the entire band for transmission of control channels. For data transmission/reception by a UE, if the entire band is monitored to receive downlink control channels, this may result in increased battery consumption and reduced efficiency for the UE. Therefore, in the present invention, downlink control channels can be transmitted locally or distributed in a portion of the system band (i.e., the channel band).

In NR systems, the basic transmission unit is the time slot. The duration of a time slot consists of 14 symbols with a normal cyclic prefix (CP) or 12 symbols with an extended CP. In addition, the time slot can be scaled in time as a function of the subcarrier spacing used.

<Analog Beamforming>

The fifth generation (5G) mobile communication system that has been discussed recently is considering the use of an ultra-high frequency band, that is, a millimeter frequency band equal to or higher than 6 GHz, to send data to multiple users in a wide frequency band while maintaining a high transmission rate. In 3GPP, this system is used as NR, and in the present invention, this system will be referred to as an NR system. Since the millimeter frequency band uses too high a frequency band, its frequency characteristics exhibit very strong signal attenuation depending on the distance. Therefore, in order to correct the strong propagation attenuation characteristics, the NR system using a frequency band of at least 6 GHz or more uses a narrow beam transmission scheme to solve the problem of reduced coverage caused by strong propagation attenuation by sending signals in a specific direction rather than in all directions in order to focus energy. However, if only one narrow beam is used to provide signal transmission services, since the range served by one BS is narrowed, the BS provides broadband services by aggregating multiple narrow beams.

In the millimeter frequency band (i.e., millimeter wave (mmW) band), wavelengths are shortened, allowing multiple antenna elements to be installed in the same area. For example, a total of 100 antenna elements can be installed in a 5 × 5 cm panel in a two-dimensional array at intervals of 0.5λ (wavelength) in the 30 GHz band, where the wavelength is approximately 1 cm. Therefore, in mmW bands, increasing coverage or throughput by increasing beamforming (BF) gain using multiple antenna elements is considered.

As a method of forming a narrow beam in the millimeter frequency band, the main consideration is a beamforming scheme, in which the BS or UE sends the same signal through a large number of antennas using an appropriate phase difference so that the energy increases only in a specific direction. This beamforming scheme includes digital beamforming for imparting a phase difference to a digital baseband signal, analog beamforming for imparting a phase difference to a modulated analog signal using a time delay (i.e., cyclic shift), and hybrid beamforming using both digital beamforming and analog beamforming. If a transceiver unit (TXRU) is provided for each antenna unit to enable adjustment of the transmit power and phase, each frequency resource can be beamformed independently. However, installing TXRU in all approximately 100 antenna units is not feasible in terms of cost. That is, the millimeter frequency band requires the use of a large number of antennas to correct the strong propagation attenuation characteristics. Digital beamforming requires as many radio frequency (RF) components (e.g., digital-to-analog converters (DACs), mixers, power amplifiers, linear amplifiers, etc.) as the number of antennas. Therefore, if digital beamforming is desired to be implemented in the millimeter frequency band, the cost of the communication equipment increases. Therefore, when a large number of antennas are required in the millimeter frequency band, analog beamforming or hybrid beamforming is considered. In the analog beamforming method, multiple antenna elements are mapped to one TXRU, and an analog phase shifter is used to adjust the beam direction. This analog beamforming method can form only one beam direction in the entire frequency band, so frequency selective beamforming (BF) cannot be performed, which is disadvantageous. The hybrid BF method is an intermediate type between digital BF and analog BF, and uses B TXRUs, which are less than Q antenna units. In the case of hybrid BF, the number of directions in which beams can be transmitted simultaneously is limited to B or less, depending on the collection method of B TXRUs and Q antenna units.

As described above, digital BF can simultaneously transmit or receive signals in multiple directions using multiple beams by processing the digital baseband signals to be transmitted or received. However, analog BF, in which the analog signals to be transmitted or received are modulated, cannot simultaneously transmit or receive signals in multiple directions beyond the coverage area of a single beam. Typically, a base station (BS) utilizes wideband transmission or multi-antenna features to simultaneously communicate with multiple users. If a BS uses analog or hybrid BF and forms an analog beam in a single beam direction, due to the analog BF characteristics, the eNB can only communicate with users included in the same analog beam direction. Considering the limitations imposed by analog or hybrid BF, a RACH resource allocation method and a BS resource utilization method according to the present invention are proposed, which will be described later.

<Hybrid Simulation BF>

Figure 3 abstractly illustrates the TXRU and hybrid BF structure in terms of physical antennas.

When multiple antennas are used, a hybrid BF method that combines digital BF and analog BF is considered. Analog BF (or RF BF) refers to the operation of the RF unit performing precoding (or combining). In hybrid BF, each of the baseband unit and the RF unit performs precoding (or combining), so that performance similar to that of digital BF can be obtained while reducing the number of RF chains and the number of digital-to-analog (D/A) (or analog-to-digital (A/D)) converters. For convenience, the hybrid BF structure can be represented as N TXRUs and M physical antennas. The digital BF of the L data layers to be sent by the transmitter can be represented as an N×L matrix. Next, the N converted digital signals are converted into analog signals by the TXRU, and the analog BF represented as an M×N matrix is applied to the analog signal. In Figure 3, the number of digital beams is L and the number of analog beams is N. In the NR system, the BS is designed to change the analog BF in units of symbols, and considers efficient BF support for UEs located in a specific area. If N TXRUs and M RF antennas are defined as one antenna panel, the NR system even considers introducing a method for applying multiple antenna panels to which independent hybrid beamforming (BF) can be applied. In this way, when the BS uses multiple analog beams, since which analog beam is beneficial for signal reception can differ for each UE, beam sweeping operation is considered. This allows all UEs to receive signals, at least for synchronization signals, system information, and paging, by varying the multiple analog beams applied by the BS according to the symbols in a specific time slot or subframe.

Recently, the 3GPP standardization organization is considering network slicing to implement multiple logical networks within a single physical network in new RAT systems (i.e., NR systems, which are 5G wireless communication systems). The logical networks should be able to support a variety of services with varying requirements (e.g., eMBB, mMTC, URLLC, etc.). The physical layer system of the NR system is considering a method for supporting orthogonal frequency division multiplexing (OFDM) using variable parameter sets depending on the service. In other words, the NR system can support OFDM (or multiple access) using independent parameter sets in each time and frequency resource area.

Recently, with the advent of smart phone devices, data traffic has increased significantly, and NR systems need to support higher communication capacity (e.g., data throughput). One method considered for increasing communication capacity is to use multiple transmit (or receive) antennas to send data. If you want to apply digital BF to multiple antennas, each antenna requires an RF chain (e.g., a chain consisting of RF elements such as a power amplifier and a downconverter) and a D/A or A/D converter. This structure increases hardware complexity and consumes high power, which may not be practical. Therefore, when using multiple antennas, the NR system considers the above-mentioned hybrid BF method that combines digital BF and analog BF.

FIG4 illustrates a cell of a New Radio Access Technology (NR) system.

Referring to Figure 4, in the NR system, a method of forming a cell with multiple transmission and reception points (TRPs) is being discussed, which is different from the conventional LTE wireless communication system in which one base station forms one cell. If multiple TRPs form one cell, seamless communication can be provided even when the TRP providing service to the UE changes, thereby facilitating UE mobility management.

In LTE/LTE-A systems, the PSS/SSS is transmitted omnidirectionally. Consider a method in which a gNB using millimeter wave (mmWave) transmits signals such as the PSS/SSS/PBCH via a beam forwarding function (BF) while sweeping a beam direction omnidirectionally. Transmitting/receiving signals while sweeping a beam direction is referred to as beam sweeping or beam scanning. In this disclosure, "beam sweeping" refers to the behavior of a transmitter, while "beam scanning" refers to the behavior of a receiver. For example, assuming a gNB can have up to N beam directions, the gNB transmits signals such as the PSS/SSS/PBCH in each of the N beam directions. That is, the gNB transmits synchronization signals such as the PSS/SSS/PBCH in each direction while sweeping across directions the gNB can support or that the gNB wishes to support. Alternatively, if the gNB can form N beams, a beam group can be configured by grouping several beams, and the PSS/SSS/PBCH can be transmitted/received for each beam group. In this case, a beam group includes one or more beams. Signals such as PSS/SSS/PBCH transmitted in the same direction can be defined as one synchronization (SS) block, and multiple SS blocks can exist in one cell. When there are multiple SS blocks, the SS block index can be used to distinguish between the SS blocks. For example, if PSS/SSS/PBCH is transmitted in 10 beam directions in a system, the PSS/SSS/PBCH transmitted in the same direction can constitute one SS block, and it can be understood that there are 10 SS blocks in the system. In the present invention, the beam index can be interpreted as an SS block index.

FIG5 illustrates transmission of an SS block and RACH resources linked to the SS block.

To communicate with a UE, the gNB must acquire the optimal beam direction between the gNB and the UE and continuously track the optimal beam direction, as the optimal beam direction changes as the UE moves. The process of acquiring the optimal beam direction between the gNB and the UE is called the beam acquisition process, and the process of continuously tracking the optimal beam direction is called the beam tracking process. The beam acquisition process is required for 1) initial access, when the UE first attempts to access the gNB; 2) handover, when the UE switches from one gNB to another; or 3) beam recovery, when the UE and the gNB cannot maintain optimal communication or enter a communication-impossible state due to loss of the optimal beam while performing beam tracking to search for the optimal beam between the UE and the gNB (i.e., beam failure).

In the context of NR systems currently under development, a multi-stage beam acquisition process is being discussed for beam acquisition in environments using multiple beams. In this multi-stage beam acquisition process, the gNB and UE establish a connection using a wide beam during the initial access phase. After the connection is established, the gNB and UE communicate using a narrowband network with optimal quality. While this disclosure primarily discusses various beam acquisition methods for NR systems, the most actively discussed methods are as follows.

1) The gNB transmits an SS block per wide beam, allowing the UE to search for the gNB during the initial access process (i.e., perform cell search or cell acquisition) and search for the optimal wide beam to use in the first phase of beam acquisition by measuring the channel quality of each wide beam. 2) The UE performs a cell search for the SS block per beam and uses the cell detection results for each beam to perform DL beam acquisition. 3) The UE performs a RACH procedure to notify the gNB that the UE will access the gNB it has discovered. 4) The gNB connects or associates the SS block transmitted per beam with the RACH resource to be used for RACH transmission, allowing the UE to notify the gNB of the results of the RACH procedure and the results of DL beam acquisition (e.g., beam index) for the wide beam level. If the UE performs a RACH procedure using a RACH resource connected to the optimal beam direction discovered by the UE, the gNB obtains information about the DL beam suitable for the UE during the RACH preamble reception process.

<Beam Correspondence (BC)>

In a multi-beam environment, whether the UE and/or TRP can accurately determine the transmit (Tx) and/or receive (Rx) beam direction between the UE and the TRP is questionable. In a multi-beam environment, beam sweeping or signal transmission repetition for signal reception may be considered based on the Tx/Rx reciprocity capability of the TRP (e.g., eNB) or the UE. The Tx/Rx reciprocity capability is also referred to as Tx/Rx beam correspondence (BC) in the TRP and the UE. In a multi-beam environment, if the Tx/Rx reciprocity capability in the TRP or the UE is not valid, the UE may not transmit UL signals in the beam direction in which the UE has received DL signals because the optimal path for UL may be different from the optimal path for DL. If the TRP can determine the TRP Rx beam for UL reception based on the UE's DL measurements for one or more Tx beams of the TRP, and/or if the TRP can determine the TRP Tx beam for DL transmission based on the TRP's UL measurements for one or more Rx beams of the TRP, then the Tx/Rx BC in the TRP is valid. Tx/Rx BC in the UE is valid if the UE can determine the UE Rx beam for UL transmission based on the UE's DL measurements of one or more Rx beams for the UE and/or if the UE can determine the UE Tx beam for DL reception based on an indication of the TRP based on UL measurements of one or more Tx beams for the UE.

In LTE and NR systems, the following elements may be used to configure a RACH signal for initial access to a gNB (i.e., initial access to a gNB via a cell used by the gNB).

* Cyclic Prefix (CP): This element is used to prevent interference from the previous OFDM symbol and to group RACH preambles arriving at the gNB with different time delays into one time zone. That is, if the CP is configured to match the maximum cell radius, RACH preambles already transmitted by UEs in the cell using the same resources are included in the RACH reception window corresponding to the length of the RACH preamble configured by the gNB for RACH reception. The CP length is typically set to be equal to or greater than the maximum round-trip delay.

*Preamble: defines the sequence used by the gNB for detection signal transmission, and the preamble is used to carry this sequence.

Guard Time (GT): This element is defined so that a RACH signal arriving at the gNB with a delay from the maximum distance from the gNB within the RACH coverage area does not interfere with signals arriving after the RACH symbol duration. During this GT, the UE does not transmit a signal, so the GT is not defined as a RACH signal.

FIG6 illustrates the configuration/format of the RACH preamble and receiver functionality.

The UE transmits a RACH signal using a designated RACH resource at the gNB's system timing obtained through the SS. The gNB receives signals from multiple UEs. Typically, the gNB performs the process shown in Figure 5 for RACH reception. Since the CP used for RACH signals is set to the maximum round-trip delay or more, the gNB can configure any point between the maximum round-trip delay and the CP length as the boundary for signal reception. If the boundary is determined as the starting point for signal reception and correlation is applied to a signal of a length corresponding to the sequence length from the starting point, the gNB can obtain information regarding the presence of a RACH signal and information regarding the CP.

If the communication environment operated by the gNB (e.g., the millimeter wave band) uses multiple beams, RACH signals arrive at the eNB from multiple directions, and the gNB needs to detect RACH preambles (i.e., PRACH) while sweeping the beam direction to receive RACH signals arriving from multiple directions. As described above, when using analog BF, the gNB performs RACH reception in only one direction at a time. To this end, it is necessary to design the RACH preamble and RACH procedure so that the gNB can correctly detect the RACH preamble. Considering both cases where the gNB's BF is effective and cases where it is not, the present invention proposes RACH preambles and/or RACH procedures for high-frequency bands applicable to NR systems (particularly BF).

FIG7 illustrates a receive (Rx) beam formed at a gNB to receive a RACH preamble.

If BC is inactive, even when the gNB forms an Rx beam in the Tx beam direction of an SS block while the RACH resource is linked to the SS block, the beam direction may not match. Therefore, the RACH preamble can be configured in the format shown in Figure 7(a) so that the gNB can perform beam scanning to perform/attempt RACH preamble detection while sweeping the Rx beam in multiple directions. Conversely, if BC is active, since the RACH resource is linked to the SS block, the gNB can form an Rx beam in the direction used to transmit the SS block for one RACH resource and detect the RACH preamble only in that direction. Therefore, the RACH preamble can be configured in the format shown in Figure 7(b).

As mentioned above, considering the two purposes of the RACH procedure of UE's DL beam acquisition report and DL preferred beam report and beam scanning according to the gNB's BC, RACH signals and RACH resources should be configured.

8 shows a RACH signal and a RACH resource for explaining terms used to describe the present invention. In the present invention, the RACH signal can be configured as follows.

*RACH Resource Element: A RACH resource element is the basic unit used by a UE to transmit a RACH signal. Because different RACH resource elements can be used for RACH signal transmission by different UEs, a CP is inserted into the RACH signal within each RACH resource element. The CP already protects signals between UEs, so a GT is not required between RACH resource elements.

*RACH Resource: A RACH resource is defined as a set of concatenated RACH resource elements connected to one SS block. If RACH resources are allocated contiguously, two consecutive RACH resources can be used for signal transmission to different UEs, such as RACH resource elements. Therefore, a CP can be inserted into the RACH signal within each RACH resource. A GT is not required between RACH resources, as the CP prevents signal detection distortion caused by time delay. However, if only one RACH resource is allocated (i.e., non-contiguously), a GT can be inserted before the PUSCH/PUCCH, as the PUSCH/PUCCH can be allocated after the RACH resource.

*RACH resource set: A RACH resource set is a collection of concatenated RACH resources. If a cell has multiple SS blocks and the RACH resources connected to each of the multiple SS blocks are concatenated, the concatenated RACH resources can be defined as a RACH resource set. A GT is inserted into the last RACH resource set, which is the portion of the RACH resource set where RACH resources are included and other signals such as PUSCH/PUCCH may intersect. As described above, since a GT is a duration during which no signal is transmitted, it can be excluded from being defined as a signal. The GT is not shown in Figure 8.

*RACH preamble repetition: When configuring a RACH preamble for Rx beam scanning of the gNB, that is, when the gNB configures the RACH preamble format so that the gNB can perform Rx beam scanning, if the same signal (i.e., the same sequence) is repeated within the RACH preamble, a CP is not required between the repeated signals because the repeated signal serves as the CP. However, when the preamble is repeated within the RACH preamble using different signals, a CP is required between the preambles. A GT is not required between RACH preambles. Hereinafter, the present invention is described assuming that the same signal is repeated. For example, if the RACH preamble is configured in the form of "CP+preamble+preamble," the present invention is described assuming that the preambles within the RACH preamble are configured with the same sequence.

Figure 8 illustrates RACH resources for multiple SS blocks and the RACH preamble in each RACH resource for a gNB. The gNB attempts to receive a RACH preamble in each RACH resource of the corresponding cell in the time zone for which the RACH resources are configured. A UE transmits its RACH preamble using a RACH resource linked to a specific SS block (e.g., an SS block with better reception quality), rather than transmitting a RACH preamble in each RACH resource for all SS blocks of the cell. As described above, different RACH resource elements or different RACH resources can be used to transmit RACH preambles by different UEs.

Figure 9 illustrates RACH resource sets. Figure 9(a) illustrates the case where two RACH resource elements are configured for each RACH resource in a cell of a gNB with valid BC. Figure 9(b) illustrates the case where one RACH resource element is configured for each RACH resource in a cell of a gNB with valid BC. Referring to Figure 9(a), two RACH preambles can be transmitted in a RACH resource linked to an SS block. Referring to Figure 9(b), one RACH preamble can be transmitted in a RACH resource linked to an SS block.

A RACH resource set may be configured as shown in FIG9 to maximize the efficiency of RACH resources using the RACH signal configuration characteristics described in FIG8. As shown in FIG9, to improve the efficiency of RACH resource usage/allocation, RACH resources or RACH resource elements may be configured to be fully concatenated without allocating blank durations between RACH resources in a RACH resource set.

However, if RACH resources are configured as shown in Figure 9, the following issues may arise. 1) When BC is enabled and the gNB receives the RACH resources corresponding to SS block #N by forming a beam in the direction of SS block #N, because the Rx beam changes in the middle of the OFDM symbol (OS) defined for the data or control channel, the gNB only partially uses resources other than the frequency resources allocated as RACH resources. That is, as shown in Figure 9(a), if the gNB forms an Rx beam to receive SS block #1, OS #4 cannot be used for the data channel or control channel. 2) When BC is disabled and the gNB performs Rx beam scanning within the RACH resource element, the gNB can perform RACH preamble detection while receiving data/control signals by forming an Rx beam for the RACH resources corresponding to SS block #1 on each OS at the boundary of OS #1/OS #2/OS #3. However, when the gNB performs beam scanning on the RACH resource corresponding to SS block #2, the beam direction for receiving data/control signals and the beam direction for receiving the RACH preamble do not match in the duration corresponding to OS #4, and thus problems arise in detecting the RACH preamble.

In summary, if the gNB performs beam scanning while changing the direction of the Rx beam used for RACH signal reception, and the timing of the Rx beam change does not match the OFDM symbol boundaries defined for data or control channels, there is a problem of reduced resource utilization/allocation efficiency for data or control channels served in frequency regions outside of the frequency resources allocated as RACH resources. To address this issue, the present invention proposes a structure in which RACH resources are allocated to be aligned with OFDM symbol boundaries. This allows the gNB to perform RACH preamble detection while changing the beam direction in multi-beam scenarios, while simultaneously utilizing all radio resources other than the RACH resources used for data and control channels. When BC is in effect, two methods can be used, for example, to align RACH resources or RACH preambles transmitted via RACH resources with OFDM symbol boundaries, as shown in Figure 10.

Figure 10 illustrates RACH resource boundary alignment according to the present invention. The example shown in Figure 10 corresponds to a case where BC is valid and two RACH resource elements can be transmitted on a single RACH resource. When BC is not valid, a single RACH preamble can be configured with a single CP and multiple consecutive preambles, as shown in Figures 7(a) or 8(a). Even in this case, the present invention can be applied. It is possible to transmit only one RACH resource element on a single RACH resource, and the present invention is applicable thereto.

1) One method for aligning OFDM symbol boundaries with RACH resource boundaries (hereinafter, Method 1) determines the CP length and preamble length of the RACH preamble by considering the gNB's RACH preamble detection capability, the gNB's coverage, and the subcarrier spacing of the RACH preamble. The CP length and preamble length are then used to configure RACH resource elements, as shown in Figure 10(a). The gNB can configure RACH resources by determining the number of RACH resource elements per RACH resource, taking into account the RACH resource capacity. The gNB configures RACH resources so that the boundaries of each RACH resource to be used consecutively align with the boundaries of OFDM symbols to be used for data and control channels. In this case, a blank duration may occur between RACH resources. The blank duration can be configured as a duration during which no signal is transmitted. Alternatively, a signal can be sent as a postfix only to the last RACH resource element in the RACH resource. That is, a UE transmitting a RACH preamble using the last RACH resource element in the time domain among the RACH resource elements in the RACH resource can append the postfix signal to its RACH preamble before transmitting the RACH preamble. A UE that transmits a RACH preamble using RACH resource elements other than the last RACH resource element can transmit the RACH preamble without adding a suffix signal.

2) Another method (hereinafter, Method 2) among the methods for aligning OFDM symbol boundaries and RACH resource boundaries configures the CP length and preamble length to align the RACH resource boundary with the OFDM symbol boundary, as shown in Figure 10(b). However, since the number of RACH resource elements in each RACH resource can vary, changing the length of the RACH preamble to match the OFDM symbol boundary poses a risk of changing the characteristics of the preamble sequence in the RACH preamble. Specifically, depending on the preamble format shown in Table 4, the length of the Zadoff-Chu (ZC) sequence used to generate the preamble is determined to be 839 or 139. Changing the preamble length to align the RACH preamble length with the OFDM symbol boundary poses a risk of changing the characteristics of the ZC sequence as the preamble sequence. Therefore, if the RACH preamble format is determined and the RACH resource elements for each RACH resource are determined, the RACH preamble length can be fixed, but the CP length can become larger than the length determined when configuring the RACH preamble format, so that the RACH resource is aligned with the OFDM symbol boundary. Specifically, this method aligns RACH resource boundaries (i.e., boundaries of RACH preambles transmitted/received via RACH resources) with boundaries of OFDM symbols used to transmit data/control channels (i.e., normal OFDM symbols) by fixing the length of each preamble in the RACH preamble and increasing the CP length to match the OFDM symbol boundary to maintain the characteristics of the preamble sequence. In this case, the CP length of only some RACH resource elements can be configured to increase (i.e., the CP length of only some RACH preambles can be configured to increase), or the CP length of all RACH resource elements can be configured to increase appropriately (i.e., the CP length of each RACH preamble can be configured to increase appropriately). For example, if the gNB configures RACH resources in the time domain configured by OFDM symbols, the gNB configures a preamble format that specifies a CP length and a sequence portion length, such that the sequence portion length is a positive integer multiple of the preamble length obtained from a specific length (e.g., the length of the RACH ZC sequence) based on the number of preambles to be included in the corresponding RACH preamble, and the CP length is equal to the value obtained by subtracting the preamble portion length from the total length of a normal OFDM symbol. If the OFDM symbols are all the same length, the RACH preamble format according to the present invention is defined such that the sum of positive integer multiples of a preamble length (e.g., the preamble length obtained from the preamble length of the ZC sequence) and the CP length is a multiple of the OFDM symbol length. When a UE detects an SS block of a cell and generates a RACH preamble to be transmitted on a RACH resource connected to the SS block, the UE generates the RACH preamble by generating each preamble to be included in the RACH preamble using a sequence of a specific length (e.g., a ZC sequence) according to the preamble format configured by the gNB and adding a CP to the leading portion of the preamble or a repetition of the preamble.

Methods 1 and 2 can also be applied similarly even when the gNB performs Rx beam scanning due to inactive BC. When BC is active for Methods 1 and 2, it is likely that the RACH preamble will be configured in a format that includes one preamble. Furthermore, Methods 1 and 2 described with reference to FIG10 can also be applied similarly when the gNB wishes to perform Rx beam scanning due to inactive BC, except when there is a high probability that the RACH preamble will be configured to include preamble repetitions when BC is inactive. For example, when the gNB wishes to perform Rx beam scanning due to inactive BC, the gNB configures and signals a preamble format that includes preamble repetitions (e.g., see FIG7(a) or FIG8(a)). Here, the RACH resource can be configured in the manner of Method 1 so that the RACH preamble is monitored by considering the duration from the end of one RACH resource to the portion immediately before the start of the next RACH resource as the blanking duration or suffix duration. Alternatively, RACH resources can be configured in the form of Method 2 to monitor the RACH preamble in each RACH resource configured by the gNB under the assumption that the RACH preamble boundary is equal to the OFDM symbol boundary.

The RACH resource allocation method proposed in this invention is used to efficiently use frequency resources other than those occupied by RACH resources as data resources or control channel resources in one or more time slots used for RACH resources. Therefore, to effectively use data/control channel resources taking into account RACH resources, the gNB needs to schedule data or control channels using information about which element is used for beamforming for the time slot to which the RACH resources are allocated. When the gNB performs scheduling based on this information and transmits data or control channels, the UE can receive information about which OFDM symbol element is used. To this end, two methods can be considered to enable the gNB to schedule data or control channels in the time zone to which the RACH resources are allocated.

*Mini slot allocation

When scheduling a channel in a time region to which a RACH resource is allocated, since the scheduled channel should be included in one beam region, the time length of the resource to which the channel is allocated should be shorter than the time length of the RACH resource and multiple time slots of short length may be included for one RACH resource.

If the gNB operates by configuring a beam direction for each RACH resource, and the time units in which the gNB allocates resources to the UE do not match in the time zones to which RACH resources are allocated and in the time zones to which RACH resources are not allocated, the gNB should define a time slot for scheduling in the time zone occupied by the RACH resources and notify the UE of information related to this time slot. Hereinafter, the time slot used for scheduling in the time zone occupied by the RACH resources will be referred to as a mini-slot. In this structure, there are several considerations for transmitting data or control channels using mini-slots. For example, the following considerations are given.

1) A case where a mini-slot is defined for the timeslot to which the RACH resource is allocated:

FIG11 illustrates a method of configuring a mini-slot in a RACH time slot SLOT _RACH when BC is valid.

The UE knows all information about the RACH resources used by the gNB through system information. Therefore, the smallest set of OFDM symbols that includes the entire RACH resource allocated for each SS block can be defined as a mini-slot. When the gNB performs scheduling at the time the RACH resources are allocated, the UE interprets the mini-slot as the length of the TTI and transmits data or control channels within the TTI. If multiple mini-slots are included in a normal timeslot, the UE needs to determine which mini-slot it will use to transmit the data/control channel. Methods for the UE to determine the mini-slot to use for transmitting data/control channels can broadly include the following two schemes.

A. If the gNB schedules the transmission of UL data/control channels, the gNB can specify to the UE via DCI which mini-slot within the timeslot the UE should use for transmission.

B. The UE continuously performs beam tracking in a multi-beam scenario. If the UE previously received information from the gNB regarding the SS block to which the serving beam from which the UE is currently receiving service is connected, the UE interprets the same time zone as the time zone to which the RACH resources connected to the SS block associated with the serving beam are allocated as the time zone in which the UE should perform transmission. If the RACH resources connected to the SS block associated with the UE's serving beam are not present in the time slot scheduled for the UE, the UE may determine that beam mismatch has occurred.

2) A case where multiple mini-slots are defined in a time slot to which RACH resources are allocated:

FIG12 illustrates another method of configuring mini-slots in the RACH time slot SLOT _RACH when BC is valid.

When multiple mini-slots are defined in a timeslot to which RACH resources are allocated, this is essentially similar to the case where multiple mini-slots are defined in a timeslot to which RACH resources are allocated, except that multiple mini-slots exist in one timeslot to which RACH resources are allocated. The same operations as the method presented in Figure 11 are performed. However, as shown in Figure 12, the minimum OFDM symbol set comprising the entire RACH resource is divided into several subsets, and each subset is defined as a mini-slot. In this case, the gNB should first inform the UE how the minimum OFDM symbol set comprising the RACH resource should be divided to use mini-slots. For example, the gNB can indicate to the UE how the minimum OFDM symbol comprising the RACH resource should be divided in the form of a bitmap. Alternatively, when the minimum OFDM symbol comprising the RACH resource can be divided into multiple equal subsets, the gNB can inform the UE of the number of allocated mini-slots. Furthermore, the gNB should indicate to the scheduled UE which mini-slot of the multiple mini-slots the UE should use to transmit data/control channels. The gNB can directly indicate the mini-slots over which data/control channels should be transmitted via DCI. Alternatively, when scheduling a UE in the time zone to which RACH resources are allocated, the gNB can notify the UE in advance (e.g., during connection establishment) of the mini-slots to be used. Alternatively, the mini-slots to be used can be determined by a predetermined rule using information shared between the UE and gNB (such as the UE ID).

3) Case where BC is not valid during preamble repetition and thus beam scanning is performed:

FIG13 illustrates a method of configuring a mini-slot within a RACH time slot SLOT _RACH when BC is not valid.

When beam scanning is inactive, as described above, the gNB performs beam sweeping while sweeping the receiver's beam direction in the slot to which a RACH resource is allocated. Therefore, this scenario can operate similarly to a scenario in which beam scanning is active and multiple mini-slots exist in the slot to which the RACH resource is allocated. To this end, similar to the method described in Figure 12 , the gNB transmits to the UE information regarding how beam sweeping is performed for the minimum OFDM symbol set comprising the RACH resource, as well as information regarding which SS block each beam is connected to. This information can be used to determine which mini-slot can be scheduled for the UE. In this case, similar to the method described in Figure 12 , the UE can receive information regarding which mini-slot among the multiple mini-slots that can be scheduled for the UE is scheduled to transmit data/control channels via DCI. Alternatively, this information can be pre-scheduled via RRC signals, or defined by predefined rules using information shared between the gNB and the UE.

4) Permission-free scheduling:

>A. When the time resource of the data/control channel to be sent by the UE on the unlicensed resources overlaps with the RACH resources, the data/control channel may be sent in the mini-slot defined in the time region of the RACH resources. However, when unlicensed scheduling is used and the signal format of the data/control channel to be sent by the UE through unlicensed scheduling (i.e., through the unlicensed resources) is a normal slot or a slot that is shorter than a normal slot but longer than a mini-slot defined in the RACH resource region, and when the length of the mini-slot is too short, so that the transmission code rate of the data/control channel through the mini-slot is too high relative to the specified code rate, the UE may i) discard the transmission, ii) change the transport block size, or iii) use multiple mini-slots to send the data/control channel when multiple mini-slots are available. On the other hand, when the transmission code rate of the data/control channel is still lower than the specified code rate even if the data/control channel is sent with the length of the mini-slot, the UE may also send the data/control channel with the specified transport block size.

>B. When unlicensed scheduling is used and the signal format of the data/control channel to be transmitted by the UE via unlicensed scheduling (i.e., via unlicensed resources) is shorter than a mini-slot, the data/control channel may be transmitted normally in the mini-slot position determined in the above scheme. That is, if the data/control channel transmitted via unlicensed scheduling requires resources shorter than a mini-slot in the time domain, the UE transmits the data/control channel via a mini-slot corresponding to the same gNB Rx beam as the data/control channel, within a mini-slot configured to match the length of the RACH resource (i.e., RACH preamble). In this case, the transport block size may be increased according to a predetermined rule in proportion to the mini-slot length compared to the pre-configured signal format. For example, if the signal format for transmitting the data/control channel via unlicensed scheduling is defined as using two OFDM symbols and the mini-slot length in the RACH slot corresponds to three OFDM symbols, the transport block size capable of carrying the unlicensed scheduled data/control channel may be increased by 1.5 times.

5) Allocate mini-slots to guard time or blank duration:

FIG14 illustrates a method of configuring mini-slots using guard time.

The gNB can freely configure an Rx beam for a portion of the duration configured as the guard time, or it can freely configure an Rx beam for the blank duration in the remaining slot after configuring RACH resources in a slot, even if the blank duration is not used for guard time. Therefore, the gNB can notify the UE of information about mini-slots that can be used independently of the beam used for RACH resource reception, as well as information related to RACH resources, and the UE can expect that dynamic scheduling will be performed for mini-slots configured during the guard time. The position of the allocated mini-slot can be determined using the aforementioned method (e.g., a method indicating the length and position of the mini-slot configured in the RACH slot and the beam direction).

6) Allocation of short PUCCH resources:

In a TDD system, the control channel can be sent during part of the duration of a time slot by configuring the control channel with a short length. In the NR system, a scheme is being discussed to send the DL control channel at the front of a time slot and the UL control channel at the last part of a time slot. In particular, the UL control channel sent in this way is called a short PUCCHH. Since the short PUCCH is configured to be sent on the last one or two symbols, the short PUCCH can be sent in the above-mentioned mini-slot. However, as mentioned earlier, since the beam direction may change within a time slot, the short PUCCH cannot always be located in the last part of the time slot. Therefore, when a short PUCCH is scheduled in a slot region to which RACH resources are allocated, the UE transmits the short PUCCH in a mini-slot where there is a beam in the same direction as the beam from which the UE receives services (i.e., the gNB Rx beam, or the UE Tx beam corresponding to the gNB Rx beam) or a beam for which the gNB has previously formed a link for the short PUCCH (i.e., the gNB Rx beam, or the UE Tx beam corresponding to the gNB Rx beam). In this case, the PUCCH may be transmitted at the last symbol position in the mini-slot, at a symbol position designated by the gNB through signaling, or at a symbol position determined by a rule. However, if there is no beam in the same direction as the beam from which the UE receives services or a beam for which the gNB has previously formed a link for the short PUCCH, the UE may discard the transmission of the short PUCCH.

*Micro-slot cascade

When forming an Rx beam for a RACH resource set, if the Rx beam directions of the respective RACH resources are not significantly different, data or control channels can be transmitted using long slots to perform transmission over the entire duration of the RACH resource set. This is called mini-slot concatenation, in which the mini-slots described above are concatenated.

Figure 15 shows an example of data transmission when BC is active by concatenating mini-slots of the same length as a normal slot. Specifically, Figure 15 illustrates the transmission of concatenated mini-slots and the insertion of reference signals during the RACH resource duration when BC is active. For example, a data packet can be transmitted in a long slot obtained by concatenating mini-slots, resulting in a long slot having the same length as a normal slot. In this case, a data packet is transmitted separately in a mini-slot within the long slot.

Therefore, when using concatenated mini-slots for data transmission, since the gNB uses information about the SS block transmission direction to form the Rx beam for each RACH resource, the UE desires to transmit signals in a direction that allows for optimal reception of each SS block. Therefore, the gNB notifies the UE of information related to Rx beamforming (e.g., information associated with the SS block) for each OFDM symbol (when BC is inactive) or for each RACH resource (when BC is active) in the RACH resource time zone. In this case, smooth reception of the data channel may not be achieved because the gNB's Rx beam changes during signal transmission while the UE transmits signals using concatenated mini-slots and transmits reference signals in the format defined for normal slots. Therefore, to account for changes in the gNB's Rx beam direction, it is necessary to insert reference signals into cells where the gNB's Rx beam direction changes. To this end, it is desirable to define a reference signal structure for concatenated mini-slots allocated within a RACH resource duration. UEs to which data or control channels in a concatenated mini-slot format are allocated within a RACH resource duration should transmit reference signals in the concatenated mini-slot format.

During PUSCH or PUCCH transmission, if there is no stable gNB Rx beam for the UE Tx beam direction for PUSCH or PUCCH, or if multiple beams have similar quality, PUSCH or long PUCCH can be transmitted using concatenated mini-slots to leverage beam diversity for stable reception. In this case, the gNB can efficiently use the allocated RACH time resources by transmitting PUSCH or PUCCH in the RACH resource region.

In addition, the gNB performs beam tracking on the Tx beam or Rx beam so that the beam with the best quality is maintained as the serving beam, thereby stably maintaining service in a multi-beam environment. Therefore, the gNB can change the characteristics of the Rx beam during the time slot to which RACH resources are allocated, and measure the quality of the gNB Rx beam or UE Tx beam and perform beam tracking by causing the UE to perform repeated transmissions of the PUSCH, long PUCCH, or short PUCCH in each RACH resource region, or to transmit RS defined for beam tracking over multiple mini-slots. In other words, to efficiently use resources for beam tracking, the gNB can cause the UE to transmit a physical channel suitable for the characteristics of the time zone to which RACH resources are allocated, and the gNB can use the physical channel as a resource for beam tracking. In other words, to efficiently use resources for beam tracking, the gNB can indicate to the UE that the UE should transmit a physical channel using a UE Tx beam suitable for each mini-slot configured in the time zone to which RACH resources are allocated, and the gNB can use the physical channel in each mini-slot for beam tracking. To enable the UE to efficiently transmit a signal for beam tracking, the gNB notifies the UE of information regarding changes in beam direction as described above. The UE then inserts a reference signal into each Rx beam of the gNB based on this information and predefined rules, and transmits the reference signal. The gNB can use the reference signal as a signal for channel estimation during the Rx beam duration or as a signal for signal quality measurement for beam tracking.

When transmitting the PUSCH or long PUCCH received by the gNB using beam diversity, the antenna gain can have different characteristics because the gNB attempts to receive the signal in each Rx beam duration. Therefore, the UE can configure the PUSCH/PUCCH transmit power differently for each Rx beam direction (e.g., each RACH resource region). To this end, the gNB can notify the UE that the reference channel/signal information and power control parameters used for path loss calculation for open-loop power control should be configured separately for each RACH resource region. The UE uses this information to configure and transmit different transmit powers in the RACH resource time region.

In contrast, during signal transmission for beam tracking (or beam management) in multiple RACH resource regions, the transmission power of each RACH resource region should be kept the same so that the gNB can measure the quality of the signal received by the gNB. In this case, only one reference channel/signal is required to control the power. If the gNB notifies the UE of the reference channel/signal information or the information is predefined by a rule, the UE can use the reference channel/signal to determine the transmission power and transmit the PUSCH/PUCCH by applying the transmission power equally to all regions.

The gNB can inform the UE whether the UL data or control channel transmitted in the RACH resource transmission time zone (i.e., the time zone to which the RACH resources are configured in the corresponding cell) is used for beam diversity or beam tracking for each UL channel, and enable the UE to perform power control operations according to the above usage.

FIG. 16 is a block diagram illustrating elements of the transmitting device 10 and the receiving device 20 for implementing the present invention.

The transmitting device 10 and the receiving device 20 respectively include: radio frequency (RF) units 13 and 23, which are capable of sending and receiving radio signals carrying information, data, signals and/or messages; memories 12 and 22, which are used to store information related to communication in a wireless communication system; and processors 11 and 21, which are operatively connected to elements such as the RF units 13 and 23 and the memories 12 and 22 to control the elements and are configured to control the memories 12 and 22 and/or the RF units 13 and 23 so that the corresponding devices can perform at least one of the above-mentioned embodiments of the present invention.

The memories 12 and 22 may store programs for processing and controlling the processors 11 and 21 and may temporarily store input/output information. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally control the overall operation of the various modules in the transmitting device and the receiving device. In particular, the processors 11 and 21 can perform various control functions to implement the present invention. The processors 11 and 21 can be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The processors 11 and 21 can be implemented by hardware, firmware, software, or a combination thereof. In a hardware configuration, the processors 11 and 21 may include an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), or a field programmable gate array (FPGA). At the same time, if firmware or software is used to implement the present invention, the firmware or software can be configured to include modules, processes, functions, etc. that perform the functions or operations of the present invention. The firmware or software configured to perform the present invention can be included in the processors 11 and 21, or stored in the memories 12 and 22 to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 10 performs predetermined coding and modulation on the signals and/or data scheduled by the processor 11 or a scheduler connected to the processor 11 to be transmitted externally, and then transmits the coded and modulated data to the RF unit 13. For example, the processor 11 converts the data stream to be transmitted into K layers through demultiplexing, channel coding, scrambling, and modulation. The coded data stream is also called a codeword and is equivalent to a transport block as a data block provided by the MAC layer. One transport block (TB) is encoded into one codeword, and each codeword is transmitted to the receiving device in the form of one or more layers. For upconversion, the RF unit 13 may include an oscillator. The RF unit 13 may include N _t (where N _t is a positive integer) transmit antennas.

The signal processing process of receiving device 20 is the inverse of the signal processing process of transmitting device 10. Under the control of processor 21, RF unit 23 of receiving device 20 receives the radio signal transmitted by transmitting device 10. RF unit 23 may include N _r (where N _r is a positive integer) receive antennas and down-convert each signal received by the receive antennas to a baseband signal. For down-conversion, RF unit 23 may include an oscillator. Processor 21 decodes and demodulates the radio signal received by the receive antennas and recovers the data intended to be transmitted by transmitting device 10.

RF units 13 and 23 include one or more antennas. According to one embodiment of the present invention, under the control of processors 11 and 21, the antennas perform the function of transmitting signals processed by RF units 13 and 23 to the outside or receiving radio signals from the outside to transmit radio signals to RF units 13 and 23. Antennas may also be referred to as antenna ports. Each antenna may correspond to a physical antenna or may be configured by a combination of more than one physical antenna element. The signal transmitted from each antenna cannot be further decomposed by receiving device 20. The RS transmitted by the corresponding antenna defines the antenna from the perspective of receiving device 20 and enables receiving device 20 to derive a channel estimate for the antenna, regardless of whether the channel represents a single radio channel from one physical antenna or a composite channel from multiple physical antenna elements including the antenna. In other words, the antenna is defined so that the channel carrying the symbol of the antenna can be derived from the channel carrying the symbol of another antenna. RF units that support MIMO functionality for transmitting and receiving data using multiple antennas can be connected to two or more antennas.

In the present invention, the RF units 13 and 23 may support Rx BF and Tx BF. For example, in the present invention, the RF units 13 and 23 may be configured to perform the functions shown in FIG.

In an embodiment of the present invention, a UE functions as a transmitting device 10 in the UL and as a receiving device 20 in the DL. In an embodiment of the present invention, a gNB functions as a receiving device 20 in the UL and as a transmitting device 10 in the DL. Hereinafter, the processor, RF unit, and memory included in the UE will be referred to as the UE processor, UE RF unit, and UE memory, respectively, and the processor, RF unit, and memory included in the gNB will be referred to as the gNB processor, gNB RF unit, and gNB memory, respectively.

The gNB processor of the present invention may configure a RACH preamble for a cell according to method 1 or method 2 of the present invention based on its RACH preamble detection capability, cell coverage, and the subcarrier spacing of the RACH preamble. For example, the processor may configure the RACH preamble according to method 2 of the present invention so that the boundaries of the RACH resources occupied by the RACH preamble are aligned with the boundaries of OFDM symbols in the time domain. The gNB processor may control the gNB RF unit to transmit information regarding the configuration of the RACH preamble for the cell (e.g., preamble format, root sequence index, sequence length, and/or cyclic shift unit (N _ZC )). For example, the gNB processor may control the gNB RF unit to transmit RACH preamble configuration information and control the gNB RF unit to detect the RACH preamble on each RACH resource based on the RACH preamble configuration information. If any UE transmits a RACH preamble on a RACH resource, the gNB processor may detect the RACH preamble on the RACH resource. Conversely, if a RACH resource not used for transmitting a RACH preamble exists among the RACH resources configured by the gNB processor, the gNB processor may not detect a RACH preamble on the RACH resource. The gNB processor may perform RACH preamble reception/detection assuming that a RACH preamble in the RACH resource has been transmitted according to the RACH preamble configuration information. For example, the gNB processor may be configured to perform RACH preamble reception/detection assuming that the length N _RA of the RACH preamble transmitted to the cell to which the RACH preamble configuration is applied is equal to the total length of the OFDM network used for receiving the RACH preamble, and that the RACH preamble includes a sequence portion having a length of N _SEQ and a CP having a length of N _CP,RA . Here, the sequence portion includes n preambles (where n is a positive integer), each preamble having a length of N _u , N _SEQ = N _u * n, and N _CP,RA + N _SEQ = N _RA . Under the assumption that the RACH preamble spans the OFDM symbol from the beginning to the end in the time domain, the gNB processor may control the gNB RF unit to attempt to perform reception/detection of the RACH preamble.

The UE processor of the present invention can be configured to generate a RACH preamble according to the RACH preamble configuration of the cell when sending a RACH preamble on the cell, and control the UE RF unit to send the RACH preamble on the RACH resource. For example, the UE processor can control the UE RF unit to receive RACH preamble configuration information (e.g., preamble format, root sequence index, sequence length and/or cyclic shift unit (N _ZC )). If it is necessary to perform a RACH process, the UE processor can control the UE RF unit to generate a RACH preamble according to the RACH preamble configuration information, and send the RACH preamble on a RACH resource associated with a (specific or selected according to a specific standard) SS block. For example, the UE processor can generate the RACH preamble so that the length N _RA of the RACH preamble sent in the cell to which the RACH preamble configuration is applied is equal to the total length of the OFDM symbol used to receive the RACH preamble. The UE processor may generate a RACH preamble such that the RACH preamble includes a sequence portion having a length of N _SEQ =N _u *n and a CP. The sequence portion includes n preambles (where n is a positive integer), each preamble having a length of N _u , and a CP having a length of N _CP,RA , satisfying N _CP,RA + N _SEQ = N _RA . The UE processor may generate the RACH preamble such that it spans an OFDM symbol from the beginning to the end of the OFDM symbol in the time domain. The UE processor may control the UE RF unit to transmit the RACH preamble by spanning the OFDM symbol from the beginning to the end of the OFDM symbol in the time domain.

The gNB processor of the present invention can configure mini-slots according to any of the mini-slot allocation methods (and mini-slot concatenation methods) of the present invention. The gNB processor can control the gNB RF unit to transmit information regarding mini-slot configuration. The gNB processor can be configured to schedule a PUCCH or PUSCH for any mini-slot. The gNB processor can control the gNB RF unit to transmit scheduling information regarding mini-slots according to the mini-slot allocation method of the present invention. The UE processor of the present invention can control the UE RF unit to receive configuration information regarding mini-slots. The UE processor can control the UE RF unit to receive scheduling information regarding mini-slots configured according to the configuration information. The UE processor can control the UE RF unit to transmit a PUSCH or PUCCH in the mini-slot based on the scheduling information.

The gNB processor or UE processor of the present invention can be configured to apply the present invention to a cell operating in a high frequency band of 6 GHz or higher using analog or hybrid BF.

As described above, a detailed description of the preferred embodiments of the present invention has been given to enable those skilled in the art to implement and practice the present invention. Although the present invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various modifications and changes can be made in the present invention without departing from the spirit or scope of the present invention described in the appended claims. Therefore, the present invention should not be limited to the specific embodiments described herein, but should be given the widest scope consistent with the principles and novel features disclosed herein.

Industrial Applicability

The embodiments of the present invention are applicable to a BS, a UE or other devices in a wireless communication system.

Claims (16)

1. A method for a user equipment to transmit a random access channel (RACH) preamble in a wireless communication system, the method comprising: Generate the RACH leader; and The RACH preamble is sent using the RACH resource. In the time domain, the RACH preamble is configured as a cyclic prefix (CP) portion and a sequence portion following the CP portion. The RACH resource consists of multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain. The sequence portion includes n preambles, each preamble having a length N _{_u} , and the length N _{_SEQ} of the sequence portion is N _{_u} * n, where n is a positive integer. Wherein, the length of the CP portion, N _{_CP, RA,} is greater than the length of the CP portion of the OFDM symbol, so as to satisfy N _{_CP, RA} + N _{_SEQ} = N _{_RA}. Wherein, N _RA is the length of the RACH preamble, which is equal to the total length of the plurality of OFDM symbols in the time domain, and The start and end of the RACH preamble are aligned with the start and end of the plurality of OFDM symbols in the time domain. 2. The method according to claim 1, Where _Nu is a fixed value. 3. The method according to claim 1, further comprising: Receive information about the random access preamble format. The RACH preamble is generated according to the random access preamble format. 4. The method according to claim 1, The wireless communication system is one that is applicable to each OFDM symbol through the receiving beamforming of the base station. 5. A method for a base station to receive a random access channel (RACH) preamble in a wireless communication system, the method comprising: Send RACH preamble configuration information; and In response to the RACH preamble configuration information, the RACH preamble is received using RACH resources. In the time domain, the RACH preamble is configured as a cyclic prefix (CP) portion and a sequence portion following the CP portion. The RACH resource consists of multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain. The sequence portion includes n preambles, each preamble having a length N _{_u} , and the length N _{_SEQ} of the sequence portion is N _{_u} * n, where n is a positive integer. Wherein, the length of the CP portion, N _{_CP, RA,} is greater than the length of the CP portion of the OFDM symbol, so as to satisfy N _{_CP, RA} + N _{_SEQ} = N _{_RA}. Wherein, N _RA is the length of the RACH preamble, which is equal to the total length of the plurality of OFDM symbols in the time domain, and The start and end of the RACH preamble are aligned with the start and end of the plurality of OFDM symbols in the time domain. 6. The method according to claim 5, Where _Nu is a fixed value. 7. The method according to claim 5, The RACH preamble configuration information includes the random access preamble format, and Specifically, the RACH preamble is received according to the random access preamble format. 8. The method according to claim 5, The wireless communication system is a system for which the receiving beamforming of the base station is applicable per OFDM symbol. 9. A user equipment for transmitting a random access channel (RACH) preamble in a wireless communication system, the user equipment comprising: transceiver, and At least one processor, said at least one processor being coupled to the transceiver, Wherein, the at least one processor is configured to: Generate the RACH leader; and The RACH preamble is sent using the RACH resource. In the time domain, the RACH preamble is configured as a cyclic prefix (CP) portion and a sequence portion following the CP portion. The RACH resource consists of multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain. The sequence portion includes n preambles, each preamble having a length N _{_u} , and the length N _{_SEQ} of the sequence portion is N _{_u} * n, where n is a positive integer. Wherein, the length of the CP portion, N _{_CP, RA,} is greater than the length of the CP portion of the OFDM symbol, so as to satisfy N _{_CP, RA} + N _{_SEQ} = N _{_RA}. Wherein, N _RA is the length of the RACH preamble, which is equal to the total length of the plurality of OFDM symbols in the time domain, and The start and end of the RACH preamble are aligned with the start and end of the plurality of OFDM symbols in the time domain. 10. The user equipment according to claim 9, Where _Nu is a fixed value. 11. The user equipment according to claim 9, Wherein, the at least one processor is further configured to: Receive information about the random access preamble format, and The RACH preamble is generated according to the random access preamble format. 12. The user equipment according to claim 9, The wireless communication system is one that is applicable to each OFDM symbol through the receiving beamforming of the base station. 13. A base station for receiving a random access channel (RACH) preamble in a wireless communication system, the base station comprising: transceiver, and At least one processor, said at least one processor being coupled to the transceiver, Wherein, the at least one processor is configured to: Send RACH preamble configuration information; and In response to the RACH preamble configuration information, the RACH preamble is received using RACH resources. In the time domain, the RACH preamble is configured as a cyclic prefix (CP) portion and a sequence portion following the CP portion. The RACH resource consists of multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain. The sequence portion includes n preambles, each preamble having a length N _{_u} , and the length N _{_SEQ} of the sequence portion is N _{_u} * n, where n is a positive integer. Wherein, the length of the CP portion, N _{_CP, RA,} is greater than the length of the CP portion of the OFDM symbol, so as to satisfy N _{_CP, RA} + N _{_SEQ} = N _{_RA}. Wherein, N _RA is the length of the RACH preamble, which is equal to the total length of the plurality of OFDM symbols in the time domain, and The start and end of the RACH preamble are aligned with the start and end of the plurality of OFDM symbols in the time domain. 14. The base station according to claim 13, Where _Nu is a fixed value. 15. The base station according to claim 13, The RACH preamble configuration information includes the random access preamble format, and The at least one processor is further configured to receive the RACH preamble according to the random access preamble format. 16. The base station according to claim 13, The wireless communication system is one in which receiving beamforming is applicable per OFDM symbol.