Method and apparatus for performing random access backoff in a wireless communication system

Abstract

To provide a communication method and a system that integrates a fifth generation (5G) communication system that supports higher data speeds than fourth generation (4G) systems using an IoT (internet of things) technology.SOLUTION: The present disclosure can be applied to an intelligent service based on 5G communication technology and IoT related technology. A method and an apparatus according to this disclosure start a backoff timer for random access preamble retransmissions, determine whether a criterion for selecting an uncontested random access resource during a backoff timer is satisfied, select a random access resource for transmission of the random access preamble when a backoff timer interval criterion is satisfied, and perform random access in a wireless communication system through a terminal by transmitting a random access preamble with a selected random access resource to a base station.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system. More specifically, the present disclosure relates to an apparatus, a method, and a system for performing random access backoff in a wireless communication system.

Background Art

[0002] In order to meet the increasing demand for wireless data traffic that has been on the rise since the commercialization of 4G communication systems, efforts are underway to develop improved 5G or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are also referred to as "Beyond 4G Network" communication systems or "Post LTE" communication systems. To achieve high data rates, 5G communication systems are considered to be implemented in the millimeter wave (mmWave) band (e.g., 60 GHz band). In 5G communication systems, beamforming, massive MIMO (Multiple-Input Multiple-Output), FD-MIMO (Full Dimensional MIMO), array antenna, analog beam-forming, and large scale antenna technologies are being discussed to reduce radio wave loss and increase the transmission distance. Furthermore, for network improvement of the system, in 5G communication systems, technologies such as advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, Device to Device (D2D) communication, wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and reception-end interference cancellation are under development.In the 5G system, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), as well as advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (non orthogonal multiple access), and SCMA (sparse code multiple access) are being developed.

[0003] On the other hand, the Internet is evolving from a human-centered connection network where humans generate and consume information to an IoT (Internet of Things) network that exchanges and processes information among distributed components such as things. IoE (Internet of Everything) technology, which combines big data processing technology and others through connection to cloud servers and the like, is also emerging. To implement IoT, technical elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, technologies such as sensor networks for connecting things, machine-to-machine (M2M), and MTC (Machine Type Communication) have been studied. In the IoT environment, intelligent IT (Internet Technology) services that collect and analyze data generated by connected things to create new value for human life can be provided. IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services through the integration and combination between existing IT (information technology) technologies and various industries.

[0004] In addition, there have been various attempts to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, MTC (Machine Type Communication), and Machine to Machine (M2M) are realized by 5G communication technologies through techniques such as beamforming, MIMO, and array antennas. The application of cloud radio access network (cloud RAN) as the above-mentioned big data processing technology can also be regarded as an example of the integration of 5G technology and IoT technology.

[0005] In addition, various studies have been conducted on the random access procedure for the 5G communication system.

[0006] The above information is presented only as background information to assist in the understanding of the present disclosure. No determination has been made, nor is any claim being made, as to whether any of the above matters are applicable as prior art in relation to the present disclosure.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] There are various requirements for improving the random access procedure in the 5G communication system.

MEANS FOR SOLVING THE PROBLEMS

[0008] Aspects of the present disclosure are to solve at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below. Accordingly, aspects of the present disclosure are to provide a method and apparatus for performing random access back off in a wireless communication system.

[0009] Additional aspects will be described in part in the following description, and in part will be apparent from the description or can be learned by practicing the presented embodiments.

[0010] According to an aspect of the present disclosure, a method for a terminal to perform random access is provided. The method includes starting a backoff timer for a random access procedure, determining whether criteria for selecting a contention-free random access resource during the backoff timer are satisfied, selecting a random access preamble associated with the contention-free random access resource when the criteria during the backoff timer are satisfied, and transmitting the random access preamble to a base station.

[0011] According to another aspect of the present disclosure, a terminal for performing random access is provided. The terminal includes a transceiver configured to transmit and receive signals, and a control unit configured to start a backoff timer for a random access procedure, determine whether criteria for selecting a contention-free random access resource during the backoff timer are satisfied, access a random access preamble associated with the contention-free random access resource when the criteria during the backoff timer are satisfied, and transmit the random access preamble to a base station.

[0012] According to another aspect of the present disclosure, a method for a base station to perform random access is provided. The method includes transmitting a backoff timer for a random access procedure to a terminal, and receiving a random access preamble from the terminal, wherein it is determined whether criteria for selecting a contention-free random access resource during the backoff timer are satisfied, and the random access preamble associated with the contention-free random access resource is selected when the criteria during the backoff timer are satisfied.

[0013] According to another aspect of the present disclosure, a base station for performing random access is provided. The base station includes a transceiver configured to transmit and receive signals, and a control unit configured to transmit a backoff timer for a random access procedure to a terminal and receive a random access preamble from the terminal. However, the criterion for selecting a contention-free random access resource is determined during the backoff timer, and the random access preamble associated with the contention-free random access resource is selected when the criterion during the backoff timer is satisfied.

[0014] Aspects, advantages, and salient features of the present disclosure will become apparent to those skilled in the art from the following detailed description, which discloses various embodiments of the present disclosure in connection with the accompanying drawings.

Effect of the Invention

[0015] According to various embodiments of the present disclosure, the random access procedure of the 5G communication system can be efficiently improved.

Brief Description of the Drawings

[0016]

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Modes for Carrying Out the Invention

[0017] The above-described and other aspects, features, and advantages of specific embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0018] It should be noted that throughout the drawings, the same reference numerals are used to indicate the same or similar elements, features, and structures.

[0019] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. This includes various specific details for the purpose of assistance, but these should be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications to the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Further, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

[0020] The terms and words used in the following description and claims are not limited to bibliographical meanings, but are used to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those of ordinary skill in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and is not provided to limit the present disclosure as defined by the appended claims and their equivalents.

[0021] It should be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to “a component surface” includes a reference to one or more of such surfaces.

[0022] The term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limitations, and other factors known to those of ordinary skill in the art, may occur to the extent that they do not exclude the effect the characteristic is intended to provide.

[0023] It will be understood by those of ordinary skill in the art that the blocks of a flowchart (or sequence diagram) and combinations of flowchart blocks can be represented and executed by computer program instructions. Such computer program instructions can be loaded onto the processor of a general purpose computer, special purpose computer, or programmable data processing apparatus. When the loaded program instructions are executed by the processor, this generates means for performing the functions described in the flowchart. Since the computer program instructions can be stored in a computer-readable memory usable by a special purpose computer or programmable data processing apparatus, it is also possible to generate a product that performs the functions described in the flowchart. Since the computer program instructions can be loaded onto a computer or programmable data processing apparatus, when executed as a process, this can perform the operations of the functions described in the flowchart.

[0024] The blocks of a flowchart can correspond to or be a part of a module, segment, or code that contains one or more executable instruction words embodying one or more logical functions. In some cases, the functions represented by the blocks can be executed in a different order than the listed steps. For example, two blocks listed in sequence can be executed simultaneously or in reverse order.

[0025] In such an explanation, words such as "unit" and "module" can refer to software components or hardware components such as an FPGA (field-programmable gate array) or an application-specific integrated circuit (ASIC) that can perform functions or operations, for example. However, "unit" etc. is not limited to hardware or software. A unit etc. can reside in an addressable storage medium or can be configured to drive one or more processors. A unit etc. can refer to a software component, an object-oriented software component, a class component, a task component, a process, a function, an attribute, a procedure, a subroutine, a program code segment, a driver, firmware, microcode, a circuit, data, a database, a data structure, a table, an array, or a variable. The functions provided by components and units can be a combination of smaller components and units, and can be combined with other components and units to form larger components and units. Components and units can be configured to drive a device or one or more processors with a security multimedia card.

[0026] Prior to the detailed description, terms or definitions necessary to understand the present disclosure are explained. However, such terms should be interpreted in a non-limiting manner.

[0027] As used herein, a "base station (BS)" is preferably an entity that communicates with a user equipment (UE), and can be referred to as a BS, a base transceiver station (BTS), a Node B (NB), an evolved NB (eNB), an access point (AP), a 5G NB (5GNB), or a gNB.

[0028] As used herein, a "UE" is preferably an entity that communicates with a BS, and can be referred to as a UE, a device, a mobile station (MS), a mobile equipment (ME), or a terminal.

[0029] The 5G wireless communication system will be implemented not only in lower frequency bands but also in higher frequency millimeter wave (mmWave) bands, such as the 10 GHz to 100 GHz band, in order to achieve higher data transmission rates. In order to mitigate the radio wave loss of radio waves and increase the transmission distance, beamforming, massive MIMO, FD-MIMO (full dimensional MIMO), array antennas, analog beamforming, and large-scale antenna technologies are considered in the design of the 5G wireless communication system. Also, the 5G wireless communication system is expected to handle different use cases with different requirements in terms of data speed, latency, reliability, mobility, etc. However, the design of the radio interface of the 5G wireless communication system is expected to be flexible enough to serve UEs with different capabilities depending on the use case and to market segment the UE cater service to the end customers. Exemplary use cases expected to be handled by the 5G wireless communication system include eMBB (enhanced mobile broadband), m-MTC (massive machine type communication), URLL (ultra-reliable low latency communication), etc. eMBB requirements such as dozens of Gbps data speed, low latency, and high mobility handle market segments representing existing wireless broadband subscribers who need an Internet connection everywhere, all the time and on the go. m-MTC requirements such as very high connection density, sporadic data TX, very long battery life, and low mobility addresses handle market segments representing IoT / IoE that envisions the connection of billions of devices. URLL requirements such as very low latency, very high reliability, and variable mobility handle market segments representing vehicle-to-vehicle / vehicle-to-infrastructure communication, which is predicted to be one of the enablers for industrial automation applications and autonomous vehicles.

[0030] In a 5G (also referred to as NR or New Radio) wireless communication system, the RA (random access) procedure is used to achieve uplink time synchronization. The RA procedure is used during initial access, handover, radio resource control (RRC) connection reconfiguration procedure, scheduling request transmission, secondary cell group (SCG) addition / modification, and data or control information transmission in the uplink by a UE that is not synchronized in the RRC CONNECTED state.

[0031] During the RA procedure, the UE first transmits a random access preamble (also referred to as Msg1), and then waits for a RAR (random access response) or Msg2 in the RAR window corresponding to this random access preamble transmission. The gNB (i.e., the base station) transmits the RAR on the PDSCH (physical downlink shared channel) addressed with the RA-RNTI (RA-Radio network temporary identifier). The RA-RNTI identifies the time-frequency resource (also referred to as the PRACH (physical random access channel) occasion, PRACH TX occasion, or RACH (random access channel) occasion) where the random access preamble was detected by the gNB. Multiple RARs for various random access preambles detected by the gNB can be multiplexed by the gNB with the same RAR MAC (media access control) protocol data unit (PDU). The RAR of the MAC PDU corresponds to the UE's random access preamble transmission if it contains the RAP ID (random access preamble ID) of the random access preamble transmitted by the UE. If a RAR corresponding to the random access preamble transmission is not received during the RAR window and the UE has not yet transmitted the random access preamble for a configurable number of times (configured by the gNB in the RACH configuration), the UE retransmits the random access preamble.

[0032] If a RAR corresponding to a random access preamble transmission is received and the UE transmits a dedicated random access preamble, the RA procedure is considered successful. If the UE transmits a non-dedicated (i.e., contention-based) random access preamble upon successful reception of the RAR, the UE transmits Msg3 using the uplink (UL) grant received in the RAR. Msg3 includes messages such as an RRC connection request, an RRC connection reconfiguration request, an RRC handover confirmation, a scheduling request, etc. This further includes a UE identity (i.e., C-RNTI (Cell-RNTI) or S-TMSI (system architecture evolution-temporary mobile subscriber identity) or a random number). After transmitting Msg3, the UE starts a contention resolution timer. While the contention resolution timer is running, if the UE receives a PDCCH (physical downlink control channel) addressed to the C-RNTI included in Msg3, the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. While the contention resolution timer is running, if the UE receives a contention resolution MAC control element (CE) including the UE's Contention Resolution Identity (the first X bits of the CCCH (common control channel) SDU (service data unit) transmitted in MSg3), the contention resolution is considered successful, the contention resolution timer is stopped, and the RA procedure is completed. If the contention resolution timer expires and the UE has not yet transmitted a random access preamble for a configurable number of times, the UE re-transmits the random access preamble.

[0033] In some cases, congestion may occur on the PRACH channel. To alleviate the congestion, the gNB sends a backoff indicator in the RAR MAC PDU. After that, the UE applies backoff during the random access preamble retransmission, i.e., it retransmits the random access preamble after a period randomly selected between 0 and the backoff value or between 0 and {scaling factor}*{backoff value}. The scaling factor can be signaled by the gNB for one or more events that trigger random access (e.g., handover, beam failure recovery, etc.). If the scaling factor is not signaled, it is assumed to be 1. The backoff value is obtained by the UE from a predefined backoff table corresponding to the backoff index (BI) received in the RAR MAC PDU. According to the current backoff procedure, if the RAR corresponding to the random access preamble transmission is not received during the RAR window and the UE has not yet transmitted the random access preamble for a configurable number of times, and if the random access preamble is selected among the contention-based random access preambles during the ongoing RA procedure, the UE selects a random backoff time according to a uniform distribution between 0 and the backoff value or between 0 and {scaling factor}*{backoff value}, and delays the subsequent random access preamble transmission by the selected backoff time. Additionally, if the contention resolution timer during the RA procedure expires and the UE has not yet transmitted the random access preamble for a configurable number of times, the UE selects a random backoff time according to a uniform distribution between 0 and the backoff value or between 0 and {scaling factor}*{backoff value}, and delays the subsequent random access preamble transmission by the selected backoff time.

[0034] Figure 1 illustrates the transmission of a contention-free (or non-contention) random access preamble according to an embodiment of the present disclosure.

[0035] Referring to FIG. 1, when the contention-free random access resource is configured for the UE, the Nth random access preamble transmission during the RA procedure can be based on the contention-based random access preambles 105, 110, and 115. All subsequent (N + 1)th random access preamble transmissions can be based on the contention-free random access preamble 120 as shown in FIG. 1. The current backoff procedure 125 unduly delays the (N + 1)th random access preamble transmission when the UE receives a backoff indication from the gNB after transmitting the Nth random access preambles 105 and 110. In this case, if there is at least one suitable SSB (synchronization signal block) / CSI-RS (channel state information reference signal) that can be utilized by the contention-free random access resource, the UE selects a contention-free random access preamble.

[0036] FIG. 2 illustrates the transmission of contention-based random access preambles according to an embodiment of the present disclosure.

[0037] Referring to FIG. 2, when the contention-free random access resource 205 is configured for the UE, the Nth random access preamble transmission can be based on the contention-free random access preambles 210, 215, and 220. All subsequent (N + 1)th random access preamble transmissions can be based on the contention-based random access preamble 220 as shown in FIG. 2. Since the UE retransmits using the contention-based random access preamble, backoff must be applied before the (N + 1)th transmission. However, the backoff is not applied to the current backoff procedure 225, which can result in more collisions and thus more delays.

[0038] According to aspects of the present disclosure, an improved method of random access backoff is provided.

[0039] Example 1 FIG. 3 is a flowchart of operations for random access backoff during a random access procedure according to an embodiment of the present disclosure. Referring to FIG. 3, in one embodiment, the UE performs such an operation when a RAR corresponding to the random access preamble transmission is not received during the RAR window and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when the contention resolution timer during the RA procedure expires and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when a RAR corresponding to the random access preamble transmission is not received during the RAR window, a backoff indicator is received in the RAR, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, in a two-step RACH procedure, the UE further performs such an operation when a network response indicating successful reception of MsgA indicated or transmitted by the UE to send Msg3 is not received during the response window, a backoff indicator is received in the network response, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure.

[0040] In operation 305, the UE selects a random backoff time according to a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set with a backoff value or, if the scaling factor is set by the gNB for the ongoing random access procedure, it is set with the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received from the gNB during such a random access procedure.

[0041] In operation 310, the UE starts a backoff timer for the determined backoff time.

[0042] In operation 325, it is determined whether the criteria for selecting a contention-free random access resource during the execution of the backoff timer are met. If so, the UE stops the backoff timer in operation 335. If not, the UE checks whether the backoff timer has expired in operation 330, and if so, performs random access resource selection in operation 340 (i.e., selects a random access preamble and a RACH occasion) and transmits the random access preamble. Since the criteria for selecting a contention-free random access resource are met, the UE transmits the random access preamble without waiting for the completion of the backoff time in order to perform random access resource selection (i.e., to select a random access preamble and a RACH occasion).

[0043] If the contention-free random access resource for the ongoing RA is associated with the SSB / CSI RS, or if the RA procedure is started by a PDCCH order and the PDCCH order contains a ra-preamble index that is not 0, the UE can check the criteria for selecting a contention-free random access resource once at the time of starting the backoff, during the backoff time, or periodically whenever new measurements of the SSB / CSI RS become available.

[0044] Here, the criteria for selecting a contention-free random access resource are described in detail.

[0045] A contention-free random access resource associated with an SSB and / or CSIRS is signaled at the UE during an ongoing RA procedure (other than beam failure recovery), and when the signal quality of at least one of the associated SSB or CSI RS (i.e., reference signal received power (RSRP)) exceeds a threshold (signaled by the gNB), the criteria for selecting a contention-free random access resource are considered to be satisfied.

[0046] When such an RA procedure is initiated by a PDCCH order and the PDCCH order contains a ra-preamble index that is not 0, the criteria for selecting a contention-free random access resource are further considered to be satisfied.

[0047] When the RA procedure is initiated for beam error recovery and the beam error recovery timer is running or not set, and a contention-free random access resource associated with an SSB and / or CSIRS is signaled at the UE during the ongoing RA procedure, and the signal quality of at least one of the associated SSB or CSI RS (i.e., reference signal received power (RSRP)) exceeds a threshold (signaled by the gNB), the criteria for selecting a contention-free random access resource are further considered to be satisfied.

[0048] When the backoff timer expires, the UE performs random access resource selection (i.e., selects a random access preamble and a RACH occasion) and transmits a random access preamble.

[0049] Example 1-1 Random access response reception procedure

[0050] A random access preamble is transmitted, and regardless of the possibility of a measurement gap occurring, the MAC entity must do the following: 1> When a contention-free random access preamble for a beam failure recovery request is transmitted by the MAC entity: 2> Starting from the end of the random access preamble transmission as specified in TS38.213 [6], at the first PDCCH occasion, start the ra-ResponseWindow configured in BeamFailureRecoveryConfig; 2> Monitor the PDCCH of the SpCell for responses to beam failure recovery requests identified by the C-RNTI while the ra-ResponseWindow is in progress.

[0051] 1> Otherwise: 2> Starting from the end of the random access preamble transmission as specified in TS38.213 [6], at the first PDCCH occasion, start the ra-ResponseWindow configured in RACH-ConfigCommon; 2> Monitor the PDCCH of the SpCell for random access responses identified by the RA-RNTI while the ra-ResponseWindow is in progress.

[0052] 1> When a notification of PDCCH transmission reception is received from the lower layer; and 1> When the PDCCH transmission is addressed to the C-RNTI; and 1> When a contention-free random access preamble for a beam failure recovery request is transmitted by the MAC entity: 2> Consider that the random access procedure has been successfully completed.

[0053] 1> Otherwise, if a downlink assignment is received on the PDCCH for the RA-RNTI and the received TB is successfully decoded: 2> If the random access response contains a MAC subPDU with a backoff indicator: 3> Set PREAMBLE_BACKOFF to the value of the BI field of the MAC subPDU using Table 7.2-1 in TS 38.321.

[0054] 2> Otherwise: 3> Set PREAMBLE_BACKOFF to 0 ms. 2> If the random access response contains a MAC subPDU with a random access preamble identifier corresponding to the PREAMBLE_INDEX on which the random access response was transmitted (see subclause 5.1.3): 3> Consider such random access response reception as successful.

[0055] 2> If the random access response reception is considered successful: 3> If the random access response contains a MAC subPDU having only RAPID: 4> Consider such random access procedure as successfully completed; 4> Indicate an acknowledgement to the upper layer for the SI request.

[0056] 3> Otherwise: 4> Apply the following operations to the serving cell on which the random access preamble was transmitted; 5> Process the received timing advance command (see subclause 5.2 in TS 38.321); 5> Indicate preambleReceivedTargetPower and the amount of power ramping applied to the most recent random access preamble transmission to the lower layer (i.e., (PREAMBLE_POWER_RAMPING_COUNTER - 1) X powerRampingStep); 5> If the serving cell for the random access procedure is an SRS - dedicated SCell: 6> Ignore the received UL grant.

[0057] 5>Otherwise: 6>Process the received UL grant value and indicate it to the lower layer.

[0058] 4>If the random access preamble is not selected by the MAC entity among the contention-based random access preambles: 5>Consider that the random access procedure has been successfully completed.

[0059] 4>Otherwise: 5>Set the TEMPORARY_C-RNTI with the value received in the random access response; 5>If this is the first random access response successfully received within such a random access procedure: 6>If transmission is not performed on the CCCH logical channel: 7>Indicate to the multiplexing and assembly entity to include the C-RNTI MAC CE in subsequent uplink transmissions.

[0060] 6>Obtain the MAC PDU to be transmitted from the multiplexing and assembly entity and store it in the Msg3 buffer.

[0061] 1>If a random access response containing a random access preamble identifier that matches the transmitted PREAMBLE_INDEX and whose ra-ResponseWindow configured in RACH-ConfigCommon has expired is not received; or: 1>If the ra-ResponseWindow configured in BeamFailureRecoveryConfig has expired and a PDCCH addressed with the C-RNTI is not received: 2>Consider that the random access response reception is not successful; 2>Increase the PREAMBLE_TRANSMISSION_COUNTER by 1; 2>When PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1: 3>When the random access preamble is transmitted on the SpCell: 4>The random access problem is indicated to the upper layer; 4>When the random access procedure is triggered for an SI request: 5>The random access procedure is considered not to be successfully completed.

[0062] 3>Otherwise, when the random access preamble is transmitted on the SCell: 4>The random access procedure is considered not to be successfully completed.

[0063] 2>When the random access procedure is not completed: 3>The random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF; 3>The backoff timer is started.

[0064] 3>When the criterion (defined in subclause 5.1.2 of TS38.321) for selecting a contention-free random access resource is satisfied while the backoff timer is running (i.e., during the backoff time): 4>The backoff timer is stopped; 4>The random access resource selection procedure is performed (see subclause 5.1.2 of TS38.321).

[0065] 3>When the backoff timer expires (i.e., after the backoff time), the random access resource selection procedure is performed (see subclause 5.1.2 of TS38.321).

[0066] Contention resolution procedure Contention resolution is based on the C-RNTI on the PDCCH of the SpCell or the UE contention resolution identity on the DL-SCH.

[0067] When Msg3 is transmitted, the MAC entity shall: 1> Start the ra-ContentionResolutionTimer and further start the ra-ContentionResolutionTimer for each HARQ retransmission; 1> Monitor the PDCCH while the ra-ContentionResolutionTimer is running regardless of the possibility of a measurement gap; 1> When a reception notification of a PDCCH transmission is received from the lower layer: 2> If a C-RNTI MAC CE is included in Msg3: 3> If the random access procedure is initiated by the MAC sublayer itself or the RRC sublayer, the PDCCH transmission is addressed to the C-RNTI, and includes a UL grant for a new transmission; or 3> If the random access procedure is initiated by a PDCCH order and the PDCCH transmission is addressed to the C-RNTI; or 3> If the random access procedure is initiated for beam failure recovery (as specified in subclause 5.17 of TS 38.321) and the PDCCH transmission is addressed to the C-RNTI: 4> Consider such contention resolution as successful; 4> Stop the ra-ContentionResolutionTimer; 4> Discard the TEMPORARY_C-RNTI; 4> Consider such a random access procedure as having been successfully completed.

[0068] 2> Otherwise, if a CCCH SDU is included in Msg3 and the PDCCH transmission is addressed to the TEMPORARY_C-RNTI: 3> If the MAC PDU is successfully decoded: 4> Stop the ra-ContentionResolutionTimer; 4>When the MAC PDU contains a UE contention resolution identity MAC CE; and 4>When the UE contention resolution identity of the MAC CE matches the CCCH SDU transmitted in Msg3: 5>Consider such contention resolution as successful and complete the disassembly and demultiplexing of the MAC PDU; 5>If such a random access procedure was initiated for an SI request: 6>Indicate to the upper layer the reception of a confirmation response for the SI request.

[0069] 5>Otherwise: 6>Set the C-RNTI to the value of TEMPORARY_C-RNTI; 5>Abandon TEMPORARY_C-RNTI; 5>Consider such a random access procedure as successfully completed.

[0070] 4>Otherwise 5>Abandon TEMPORARY_C-RNTI; 5>Consider such contention resolution as not successful and discard the successfully decoded MAC PDU.

[0071] 1>If the ra-ContentionResolutionTimer expires: 2>Abandon TEMPORARY_C-RNTI; 2>Consider the contention resolution as not successful.

[0072] 1>If it is considered that the contention resolution cannot succeed: 2>Flush the HARQ buffer used for transmitting the MAC PDU in the Msg3 buffer.

[0073] 2>Increase the PREAMBLE_TRANSMISSION_COUNTER by 1; 2>When PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1: 3>Indicate the random access problem to the upper layer; 3>If such a random access procedure is triggered for an SI request: 4>Consider that the random access procedure is not successfully completed.

[0074] 2>If the random access procedure is not completed: 3>Select a random backoff time according to a uniform distribution between 0 and PREAMBLE_BACKOFF; 3>Start the backoff timer.

[0075] 3>If a contention-free random access resource is explicitly provided by the RRC and the criteria for selecting a contention-free random access resource during the execution of the backoff timer (i.e., during the backoff time) (defined in subclause 5.1.2 of TS38.321) are met: 4>Stop the backoff timer; 4>Perform a random access resource selection procedure (see subclause 5.1.2 of TS38.321).

[0076] 3>When the backoff timer expires (i.e., after the backoff time), perform a random access resource selection procedure (see subclause 5.1.2 of TS 38.321).

[0077] Example 2 Figure 4 is another flowchart of operations for random access backoff during a random access procedure according to an embodiment of the present disclosure. Referring to FIG. 4, the UE does not receive an RAR corresponding to the random access preamble transmission during the RAR window, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when the contention resolution timer during the RA procedure expires and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, the UE further does not receive an RAR corresponding to the random access preamble transmission during the RAR window, receives a backoff indicator in the RAR, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, in the two-step RACH procedure, the UE further does not receive a network response indicating the successful reception of MsgA indicated or sent by the UE to send Msg3 during the response window, receives a backoff indicator in the network response, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure.

[0078] Such an RA procedure is started by the PDCCH order in operation 405, and if the PDCCH order includes a ra-preambleIndex that is not 000000, the operation proceeds to operation 410. Otherwise, the operation proceeds to operation 415.

[0079] In operation 415, a random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set with a backoff value or, if the scaling factor is set by the gNB during the ongoing random access procedure, is set with the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received in the RAR MAC PDU.

[0080] In operation 420, a backoff timer is started for the determined backoff time.

[0081] In operation 435, when the criteria for selecting a contention - free random access resource during the execution of the backoff timer are met, the backoff timer is stopped in operation 445.

[0082] Here, the criteria for selecting a contention - free random access resource are described in detail.

[0083] A contention - free random access resource associated with an SSB and / or CSI RS is signaled at the UE during an ongoing RA procedure (other than beam failure recovery), and when the signal quality (i.e., RSRP) of at least one of the associated SSB or CSI RS exceeds a threshold (signaled by the gNB), the criteria for selecting a contention - free random access resource are considered to be met.

[0084] If the RA procedure is started for beam error recovery and the beam error recovery timer is either running or not set, and a contention - free random access resource associated with an SSB and / or CSI RS is signaled at the UE during the ongoing RA procedure, and the signal quality (i.e., reference signal received power (RSRP)) of at least one of the associated SSB or CSI RS exceeds a threshold (signaled by the gNB), the criteria for selecting a contention - free random access resource are further considered to be met.

[0085] In operation 450, random access resource selection (i.e., selecting a random access preamble and a RACH occasion) is performed, and a random access preamble is transmitted.

[0086] In operation 440, when the backoff timer expires, the UE performs random access resource selection (i.e., selects a random access preamble and a RACH occasion) and transmits a random access preamble.

[0087] Example 3 FIG. 5 is another flowchart of operations for random access backoff during a random access procedure according to an embodiment of the present disclosure.

[0088] Referring to FIG. 5, the UE does not receive an RAR corresponding to the random access preamble transmission during the RAR window, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when the contention resolution timer during the RA procedure expires and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, the UE further does not receive an RAR corresponding to the random access preamble transmission during the RAR window, receives a backoff indicator in the RAR, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure. In one embodiment, in the two-step RACH procedure, the UE further does not receive a network response indicating the successful reception of MsgA indicated or transmitted by the UE to send Msg3 during the response window, receives a backoff indicator in the network response, and the UE performs such an operation when it has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure.

[0089] During such an operation 505 in the RA procedure, if the gNB sets contention-free random access resources for all SSBs and / or CSI RSs, the operation proceeds to operation 510. Otherwise, the operation proceeds to operation 515.

[0090] In operation 515, a random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set with a backoff value or, if the scaling factor is set by the gNB during the ongoing random access procedure, is set with the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received in the RAR MAC PDU.

[0091] In operation 520, a backoff timer is started for the determined backoff time.

[0092] During the ongoing random access procedure proceeding to operation 525, a contention-free random access resource is signaled by the gNB, and in operation 535, when the criteria for selecting a contention-free random access resource while the backoff timer is running are met, the backoff timer is stopped in operation 545.

[0093] If the contention-free random access resource is not set by the gNB, the UE selects a random access resource when the backoff timer expires in operation 530 and transmits a random access preamble to the base station (gNB).

[0094] Here, the criteria for selecting a contention-free random access resource are described in detail.

[0095] A contention-free random access resource associated with the SSB and / or CSI RS is signaled at the UE during the ongoing RA procedure (other than beam failure recovery), and when the signal quality (i.e., RSRP) of at least one of the associated SSB or CSI RS exceeds a threshold (signaled by the gNB), the criteria for selecting a contention-free random access resource are considered to be met.

[0096] Such an RA procedure is started by a PDCCH order. When the PDCCH order includes a ra - preamble index other than 0, the criterion for selecting a contention - free random access resource is considered to be further satisfied.

[0097] If the RA procedure is started for beam error recovery, the beam error recovery timer is running or not set, and a contention - free random access resource associated with an SSB and / or CSI RS is signaled to the UE during an ongoing RA procedure, and the signal quality of at least one of the associated SSB or CSI RS (i.e., reference signal received power (RSRP)) exceeds a threshold (signaled by the gNB), the criterion for selecting a contention - free random access resource is considered to be further satisfied.

[0098] In operation 550, random access resource selection (i.e., selecting a random access preamble and a RACH occasion) is performed, and the random access preamble is transmitted.

[0099] In operation 540, when the back - off timer expires, the UE performs random access resource selection (i.e., selects a random access preamble and a RACH occasion) and transmits the random access preamble.

[0100] Example 4 Figure 6 is another flowchart of operations for random access back - off during a random access procedure according to an embodiment of the present disclosure.

[0101] Referring to FIG. 6, if the UE does not receive a RAR corresponding to the random access preamble transmission during the RAR window, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure, such an operation is performed. In one embodiment, in the two-step RACH procedure, if the UE does not receive a network response indicating the successful reception of MsgA shown or sent by the UE to further send Msg3 during the response window, and a backoff indicator is received in the network response, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for the configurable number of times during the RA procedure, such an operation is performed.

[0102] In such an operation 605 during the RA procedure, if the contention-free random access resource is explicitly signaled by an RRC or PDCCH order, the operation proceeds to operation 610. Otherwise, the operation proceeds to operation 615.

[0103] In operation 615, a random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set by a backoff value or, if a scaling factor is set by the gNB during the ongoing random access procedure, is set by the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received in the RAR MAC PDU.

[0104] In operation 620, the subsequent random access preamble transmission is delayed by the backoff time.

[0105] In operation 625, a random access resource selection (i.e., selection of a random access preamble and a RACH occasion) is performed, and the random access preamble is transmitted.

[0106] Example 5 Figure 7 is another flowchart of operations for random access backoff during a random access procedure according to an embodiment of the present disclosure. Referring to Figure 7, the UE performs such an operation when a RAR corresponding to the random access preamble transmission is not received during the RAR window and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, in a two-step RACH procedure, the UE further performs such an operation when a network response indicating successful reception of MsgA shown or transmitted by the UE for transmitting Msg3 is not received during the response window, a backoff indicator is received in the network response, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure.

[0107] In operation 705 during the most recent preamble transmission, if a random access preamble among the contention-based random access preambles is not selected, the operation proceeds to operation 710. Otherwise, if a random access preamble among the contention-based random access preambles is selected during the most recent preamble transmission, the operation proceeds to operation 715.

[0108] In operation 715, a random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set by a backoff value or, when a scaling factor is set by the gNB during the ongoing random access procedure, is set by the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received in the RAR MAC PDU.

[0109] In operation 720, the subsequent random access preamble transmission is delayed by the backoff time.

[0110] In operation 725, random access resource selection (i.e., selection of a random access preamble and a RACH occasion) is performed and the random access preamble is transmitted.

[0111] Example 6 FIG. 8 is another flowchart of operations for random access backoff during a random access procedure according to an embodiment of the present disclosure. Referring to FIG. 8, the UE performs such an operation when a RAR corresponding to the random access preamble transmission is not received during the RAR window and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when the contention resolution timer during the RA procedure expires and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, the UE further performs such an operation when a RAR corresponding to the random access preamble transmission is not received during the RAR window, a backoff indicator is received in the RAR, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure. In one embodiment, in a two-step RACH procedure, the UE further performs such an operation when a network response indicating successful reception of MsgA indicated or transmitted by the UE for transmitting Msg3 is not received during the response window, a backoff indicator is received in the network response, and the UE has not yet transmitted the random access preamble (preambleTransMax set by the gNB via RRC signaling) for a configurable number of times during the RA procedure.

[0112] During operation 805 in such an RA procedure, when a contention-free random access resource is configured (i.e., explicitly signaled by an RRC or PDCCH order) and the criteria for selecting the contention-free random access resource are met, the operation proceeds to operation 815. Otherwise, the operation proceeds to operation 810.

[0113] In operation 810, the random backoff time is selected by a uniform distribution between 0 and PREAMBLE_BACKOFF. PREAMBLE_BACKOFF is set by a backoff value or, if a scaling factor is set by the gNB during the ongoing random access procedure, is set by the scaling factor * backoff value. The backoff value is obtained by the UE from a backoff table corresponding to the backoff index received in the RAR MAC PDU.

[0114] In operation 825, the subsequent random access preamble transmission is delayed by the backoff time.

[0115] In operation 820, random access resource selection (i.e., selection of the random access preamble and the RACH occasion) is performed and the random access preamble is transmitted.

[0116] Example 7 Hereinafter, an example of the implementation of SI window determination for SI message reception will be described. FIG. 9 shows a system information window according to an embodiment of the present disclosure. FIG. 10 shows another system information window according to an embodiment of the present disclosure. Figures 9 and 10 are exemplary diagrams of SI windows for default association. The default association (i.e., the PDCCH monitoring occasion for OSI is set the same as for RMSI (remaining system information)) is used when the osi-SearchSpace is not signaled by the gNB. The number of slots in a radio frame is assumed to be, for example, 0.

[0117] Referring to Figure 9, Figure 9 is an example of Pattern 1 where the set of PDCCH monitoring occasions for RMSI starts from system frame number (SFN) 0 and is positioned every 20 ms. In this case, the network will set the si-WindowLength (i.e., the same as N) of 20 slots. During the SI window, the UE monitors only the slots / symbols corresponding to the PDCCH monitoring occasions for the SI message.

[0118] Referring to Figure 10, Figure 10 is an example of Pattern 2 / 3 where the set of PDCCH monitoring occasions for RMSI is positioned for each synchronization signal (SS) burst set period. The SS burst set period can start from SFN0 or start with an offset from SFN0. In this example, the SS burst set period is 20 ms and the offset is 1 radio frame. In this case, the network will set the si-WindowLength of 20 slots and an offset identical to one radio frame. During the SI window, the UE monitors only the slots / symbols corresponding to the PDCCH monitoring occasions for the SI message.

[0119] For the default association: * "Pattern 1" refers to a multiplexing pattern in which the SS / PBCH block and the RMSI control resource set (CORESET) are generated from different time instances, and the initial active DL BandWidth Part (BWP) including the SS / PBCH block TX BandWidth (BW) and the RMSI CORESET overlaps; * "Pattern 2" refers to a multiplexing pattern in which the SS / PBCH block and the RMSI CORESET are generated at different time instances, and the initial active DL BWP including the SS / PBCH block TX BW and the RMSI CORESET does not overlap; * "Pattern 3" refers to a multiplexing pattern in which the SS / PBCH block and the RMSI CORESET are generated at the same time instance, and the initial active DL BWP including the SS / PBCH block TX BW and the RMSI CORESET does not overlap.

[0120] The pattern used for default association is set using the parameter PDCCHConfigSIB1 signaled in the MIB.

[0121] FIG. 11 shows another system information window according to an embodiment of the present disclosure. Referring to FIG. 11, FIG. 11 is an exemplary diagram of an SI window for non-default association. In this example, the osi-SearchSpace settings are as follows. Periodicity: 5 slots; Offset: 0; duration: 2 slots; monitoringSymbolsWithinSlot: 00100000100000; and CORESET-time-duration: 4 OFDM symbols. The number of slots in the radio frame is assumed to be, for example, 0. The number of SSBs is 12. In this case, the network will set the si-WindowLength of 15 slots so that there is a PDCCH monitoring occasion for each SSB.

[0122] The UE receives SystemInformationBlockType1 from the gNB. SystemInformationBlockType1 includes scheduleInfoList, si-WindowLength, Offset, and si-Periodicity. si-Periodicity is signaled independently for each SI message in the scheduleInfoList. All such parameters are applicable to all DL BWPs where the UE receives SI messages (for the cell). The UE procedure for determining the start of the SI window for the associated SI message is as follows:

[0123] - Determine a number n corresponding to the order of the entry in the list of SI messages set by the scheduleInfoList of SystemInformationBlockType1 for the associated SI message; - Determine an integer value x = Offset + (n - 1)*w, where w is the si-WindowLength of a slot. In one embodiment, the offset is not set and the UE determines the integer value x = (n - 1)*w, where w is the si-WindowLength; - The SI window starts at slot #a in a radio frame where SFN mod T = FLOOR(x / number of slots in a radio frame), where a = x mod (number of slots in a radio frame), and T is the si-Periodicity of the associated SI message. The number of slots in a radio frame varies depending on the SCS for the OSI. The SCS for the OSI is the SCS of the DL BWP where the UE receives SI messages. The mapping between slots in a radio frame and various SCSs is predefined; - During the SI window, the UE monitors only the slots / symbols corresponding to the PDCCH monitoring occasions for SI messages. The PDCCH monitoring occasions for SI messages are determined by the settings indicated by osi-SearchSpace if osi-SearchSpace is not 0, and otherwise are determined by default association (i.e., the PDCCH monitoring occasion for paging is the same as that for RMSI). osi-SearchSpace is the search space id of the search space setting that the UE must use for SI message reception.

[0124] FIG. 12 is a block diagram of a terminal according to an embodiment of the present disclosure. Referring to FIG. 12, the terminal includes a transceiver 1210, a control unit 1220, and a memory 123. The transceiver 1210, the control unit 1220, and the memory 1230 are configured to perform the operations of the UE as shown in the drawings, for example, FIGS. 1 to 11, or as described above. Although the transceiver 1210, the control unit 1220, and the memory 1230 are shown as separate entities, they can be implemented as a single entity such as a single chip. The transceiver 1210, the control unit 1220, and the memory 1230 can be electrically connected or coupled to each other.

[0125] The transceiver 1210 can transmit signals to other network entities, such as a base station, and then receive signals from it.

[0126] The control unit 1220 can control the UE to perform functions according to one or more of the above-described embodiments. The control unit 1220 can refer to a circuit, an ASIC (application-specific integrated circuit), or at least one processor, but these embodiments are not limited herein.

[0127] In one embodiment, the operation of the terminal can be implemented using a memory 1230 that stores corresponding program code. Specifically, a memory 1230 for storing program code for implementing desired operations can be installed in the terminal. To perform the desired operations, the control unit 1220 can interpret and execute the program code stored in the memory 1230 by using a processor or a central processing unit (CPU).

[0128] FIG. 13 is a block diagram of a BS according to an embodiment of the present disclosure. Referring to FIG. 13, the base station includes a transceiver 1310, a control unit 1320, and a memory 1330. The transceiver 1310, the control unit 1320, and the memory 1330 are configured to perform the operations of the network (e.g., gNB) shown in the drawings, for example, FIGS. 1 to 11, or described above if not shown. The transceiver 1310, the control unit 1320, and the memory 1330 are shown as separate entities, but can be implemented as a single entity such as a single chip. The transceiver 1310, the control unit 1320, and the memory 1330 can be electrically connected or coupled to each other.

[0129] The transceiver 1310 can transmit signals to other network entities, for example, terminals, and then receive signals from them.

[0130] The control unit 1320 can control the base station to perform functions according to one of the above-described embodiments. The control unit 1320 can refer to a circuit, an ASIC, or at least one processor, but these embodiments are not limited herein.

[0131] In one embodiment, the operation of the base station can be implemented using a memory 1330 that stores corresponding program code. Specifically, the base station can be equipped with a memory 1330 for storing program code that implements the desired operation. To perform the desired operation, the control unit 1320 can interpret and execute the program code stored in the memory 1330 by using a processor or CPU.

[0132] Although the present disclosure has been illustrated and described with reference to these various embodiments, those of ordinary skill in the art will understand that various changes in form and detail can be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

[0133] As described above, the embodiments disclosed in the specification and drawings are used only to present specific examples for easily explaining and assisting in understanding the content of the present disclosure, and are not intended to limit the scope of the present disclosure. Therefore, the scope of the present disclosure should be analyzed to include all changes or modifications derived based on the technical concept of the present disclosure in addition to the embodiments disclosed in this specification.

Explanation of Reference Numerals

[0134] 1210 Transceiver 1220 Control Unit 1230 Memory 1310 Transceiver 1320 Control Unit 1330 Memory

Claims

1. A method performed by a terminal of a wireless communication system, comprising: receiving, from a base station, a message including information for obtaining at least one system information (SI) message; determining a start point of an SI window for receiving the SI message based on the information and the number of slots of a radio frame; monitoring the SI message at the start point of the SI window; wherein the number of slots of the radio frame is determined based on a subcarrier spacing (SCS) setting.

2. The method according to claim 1, wherein the start point of the SI window is determined based on the length of the SI window, the period of the SI message, an n value corresponding to the order of items in a list of SI messages set by the information included in the message, and the number of slots of the radio frame.

3. The step of determining the start point of the SI window comprises: determining an n value corresponding to the order of items in a list of SI messages set by the information included in the message; determining an integer value x where x = (n - 1) * w, where w is the length of the SI window; determining the start point of the SI window to be slot a where a = x mod N in a radio frame where SFN mod T = FLOOR(x / N), where T is the SI period of the SI message, N is the number of slots of the radio frame, and SFN is the system frame number of the radio frame.

4. The method according to claim 1, wherein the message includes SI B1 (system information block 1).

5. A method performed by a base station of a wireless communication system, comprising: transmitting, to a terminal, a message including information for obtaining at least one system information (SI) message; Determining a start point of an SI window for receiving an SI message based on the information and the number of slots of a radio frame; Transmitting the SI message to the terminal based on the start point of the SI window, including; The number of slots of the radio frame is determined based on a subcarrier spacing (SCS) setting, characterized by a method.

6. The start point of the SI window is determined based on the length of the SI window, the period of the SI message, an n value corresponding to the order of items in a list of SI messages set by the information included in the message, and the number of slots of the radio frame. The method according to claim 5, characterized in that.

7. The step of determining the start point of the SI window is Determining an n value corresponding to the order of items in a list of SI messages set by the information included in the message; Determining an integer value x where x = (n - 1) * w, where w is the length of the SI window, the step of determining the integer value x; Determining the start point of the SI window in a radio frame where SFN mod T = FLOOR(x / N) and in slot a where a = x mod N, where T is the SI period of the SI message, N is the number of slots of the radio frame, and SFN is the system frame number of the radio frame. The method according to claim 5, characterized in that.

8. The message includes SIB1 (system information block 1). The method according to claim 5, characterized in that.

9. A terminal of a wireless communication system, including; A transceiver; Receiving, via the transceiver, from a base station, a message including information for obtaining at least one system information (SI) message, determining a start point of an SI window for receiving an SI message based on the information and the number of slots of a radio frame, and monitoring the SI message via the transceiver at the start point of the SI window. A control unit. The number of the slots of the wireless frame is determined based on a subcarrier spacing (SCS) setting, wherein the terminal is characterized thereby.

10. The start point of the SI window is determined based on the length of the SI window, the period of the SI message, an n value corresponding to the item order in the list of SI messages set according to the information included in the message, and the number of the slots of the wireless frame, wherein the terminal according to claim 9 is characterized thereby.

11. The control unit determines an n value corresponding to the item order in the list of SI messages set according to the information included in the message, determines an integer value x where x = (n - 1) * w, where w is the length of the SI window, and determines the start point of the SI window at a slot a where a = x mod N in a wireless frame where SFN mod T = FLOOR(x / N), where T is the SI period of the SI message, N is the number of the slots of the wireless frame, and SFN is the system frame number of the wireless frame, wherein the terminal according to claim 9 is characterized thereby.

12. The message includes an SIB1 (system information block 1), wherein the terminal according to claim 9 is characterized thereby.

13. A base station of a wireless communication system, comprising: a transceiver; and a control unit configured to transmit, via the transceiver, a message including information for obtaining at least one system information (SI) message to a terminal, determine a start point of an SI window for receiving the SI message based on the information and the number of slots of a wireless frame, and transmit the SI message to the terminal via the transceiver based on the start point of the SI window, wherein the number of the slots of the wireless frame is determined based on a subcarrier spacing (SCS) setting, wherein the base station is characterized thereby.

14. The starting point of the SI window is determined based on the length of the SI window, the period of the SI message, an n value corresponding to the item order in the list of SI messages set according to the information included in the message, and the number of slots in the radio frame. The base station according to claim 13, characterized in that.

15. The control unit determines an n value corresponding to the item order in the list of SI messages set according to the information included in the message, determines an integer value x where x = (n - 1) * w, where w is the length of the SI window, and determines the starting point of the SI window in a radio frame where SFN mod T = FLOOR(x / N) and in slot a where a = x mod N, where T is the SI period of the SI message, N is the number of slots in the radio frame, and SFN is the system frame number of the radio frame. The base station according to claim 13, characterized in that.

16. The message includes SIB1 (system information block 1). The base station according to claim 13, characterized in that.

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