WO2018190636A1 - Method and apparatus for providing system information - Google Patents

Abstract

Provided are a method for broadcasting system information, in a wireless communication system, by a distributed unit (DU) of a base station and an apparatus for supporting the method. The method may comprise the steps of: receiving, from a central unit (CU) of a base station, system information owned by the CU of the base station; receiving, from a terminal, a request for the system information; receiving, from the CU of the base station, a message commanding broadcasting of the system information; and broadcasting the requested system information.

Description

Method and apparatus for providing system information

The present invention relates to a wireless communication system, and more particularly, to a method for providing system information in a scenario in which a central unit and a distributed unit of a base station are divided, and an apparatus for supporting the same.

Efforts have been made to develop an improved 5th-generation (5G) communication system or a pre-5G communication system to meet the increasing demand for wireless data traffic since the commercialization of a 4th-generation (4G) communication system. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (beyond 4G network) or after a long term evolution (LTE) system (post LTE).

System information refers to essential information for communication between the terminal and the base station. In 3GPP LTE, system information is divided into MIB (Master Information Block) and SIB (System Information Block). MIB is the most essential information, and SIB is divided into SIB-x according to its importance or frequency. The MIB is transmitted through a physical broadcast channel (PBCH), which is a physical channel, and the SIB is transmitted through a PDCCH as common control information.

On the other hand, considering that the information generated in the RRC layer is transmitted to the terminal, the generated information should be transmitted to the terminal through a distributed unit (DU). Since the system information to be broadcast is also generated in the RRC layer of the central unit (CU), signaling between the CU and the DU may be required for the DU to broadcast the system information. For example, when a CU receives a system information request from a terminal through a DU, signaling between the CU and the DU may be necessary for the DU to broadcast the system information. However, in the CU-DU split scenario, there is no procedure for the DU to transmit the system information requested by the terminal to the terminal. Therefore, in the CU-DU partitioning scenario, a method for providing system information and an apparatus supporting the same need to be proposed.

According to an embodiment, a method of distributing system information by a distributed unit (DU) of a base station in a wireless communication system is provided. The method includes receiving from the CU of the base station the system information owned by the CU of the base station held by a central unit (CU) of the base station; Receiving a request for the system information from a terminal; Receiving a message from the CU of the base station, the message commanding to broadcast the system information; And broadcasting the requested system information.

In another embodiment, a distributed unit (DU) of a base station that broadcasts system information in a wireless communication system is provided. DU of the base station is a memory; Transceiver; And a processor that connects the memory and the transceiver, wherein the processor is configured to transmit the system information owned by the CU of the base station to which the transceiver is held by a central unit of the base station. To receive from the CU of the base station, and control the transceiver to receive a request for the system information from the terminal, and to receive a message from the CU of the base station that commands the transceiver to broadcast the requested system information. And control the transceiver to broadcast the requested system information.

System information can be provided efficiently.

1 shows a structure of an LTE system.

2 shows an air interface protocol of an LTE system for a control plane.

3 shows an air interface protocol of an LTE system for a user plane.

4 shows the structure of a 5G system.

5 shows an example in which a master information block (MIB), a system information block (SIB1), and other system information blocks (SIB) are transmitted.

6 shows a contention-based random access procedure.

7 shows a non-competition based random access procedure.

8 shows a procedure for the terminal to receive a new type of system information.

9 shows a scenario of separated base station deployment (Centralized Deployment).

10 illustrates a functional split between a central unit and a distributed unit in a split base station deployment scenario.

11 illustrates a procedure for providing system information according to an embodiment of the present invention.

12 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

13 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

14 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

15 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

16 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

17 is a block diagram illustrating a method in which a DU of a base station provides system information according to an embodiment of the present invention.

18 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented by wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA), which employs OFDMA in downlink and SC in uplink -FDMA is adopted. LTE-A (advanced) is the evolution of 3GPP LTE. 5G communication system is the evolution of LTE-A.

For clarity, the following description focuses on LTE-A, but the technical spirit of the present invention is not limited thereto.

1 shows a structure of an LTE system. Communication networks are widely deployed to provide various communication services such as IMS and Voice over internet protocol (VoIP) over packet data.

Referring to FIG. 1, an LTE system structure includes one or more UEs 10, an evolved-UMTS terrestrial radio access network (E-UTRAN), and an evolved packet core (EPC). The terminal 10 is a communication device moved by a user. The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device.

The E-UTRAN may include one or more evolved node-eB (eNB) 20, and a plurality of terminals may exist in one cell. The eNB 20 provides an end point of a control plane and a user plane to the terminal. The eNB 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to in other terms such as a base station (BS), a base transceiver system (BTS), an access point, and the like. . One eNB 20 may be arranged per cell. There may be one or more cells within the coverage of the eNB 20. One cell may be configured to have one of bandwidths such as 1.25, 2.5, 5, 10, and 20 MHz to provide downlink (DL) or uplink (UL) transmission service to various terminals. In this case, different cells may be configured to provide different bandwidths.

Hereinafter, DL means communication from the eNB 20 to the terminal 10, and UL means communication from the terminal 10 to the eNB 20. In the DL, the transmitter may be part of the eNB 20 and the receiver may be part of the terminal 10. In the UL, the transmitter may be part of the terminal 10 and the receiver may be part of the eNB 20.

The EPC may include a mobility management entity (MME) that serves as a control plane, and a system architecture evolution (SAE) gateway (S-GW) that serves as a user plane. The MME / S-GW 30 may be located at the end of the network and is connected to an external network. The MME has information about the access information of the terminal or the capability of the terminal, and this information may be mainly used for mobility management of the terminal. S-GW is a gateway having an E-UTRAN as an endpoint. The MME / S-GW 30 provides the terminal 10 with the endpoint of the session and the mobility management function. The EPC may further include a packet data network (PDN) -gateway (GW). PDN-GW is a gateway with PDN as an endpoint.

The MME includes non-access stratum (NAS) signaling to the eNB 20, NAS signaling security, access stratum (AS) security control, inter CN (node network) signaling for mobility between 3GPP access networks, idle mode terminal reachability ( Control and execution of paging retransmission), tracking area list management (for terminals in idle mode and active mode), P-GW and S-GW selection, MME selection for handover with MME change, 2G or 3G 3GPP access Bearer management, including roaming, authentication, and dedicated bearer settings, SGSN (serving GPRS support node) for handover to the network, public warning system (ETWS) and commercial mobile alarm system (PWS) It provides various functions such as CMAS) and message transmission support. S-GW hosts can be based on per-user packet filtering (eg, through deep packet inspection), legal blocking, terminal IP (Internet protocol) address assignment, transport level packing marking in DL, UL / DL service level charging, gating and It provides various functions of class enforcement, DL class enforcement based on APN-AMBR. For clarity, the MME / S-GW 30 is simply represented as a "gateway", which may include both MME and S-GW.

An interface for user traffic transmission or control traffic transmission may be used. The terminal 10 and the eNB 20 may be connected by the Uu interface. The eNBs 20 may be interconnected by an X2 interface. Neighboring eNBs 20 may have a mesh network structure by the X2 interface. The eNBs 20 may be connected with the EPC by the S1 interface. The eNBs 20 may be connected to the EPC by the S1-MME interface and may be connected to the S-GW by the S1-U interface. The S1 interface supports a many-to-many-relation between eNB 20 and MME / S-GW 30.

The eNB 20 may select for the gateway 30, routing to the gateway 30 during radio resource control (RRC) activation, scheduling and transmission of paging messages, scheduling channel information (BCH), and the like. Perform connection mobility control in transmission, dynamic allocation of resources from the UL and DL to the terminals 10, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC) and LTE activation can do. As mentioned above, the gateway 30 may perform paging initiation, LTE idle state management, user plane encryption, SAE bearer control, and encryption and integrity protection functions of NAS signaling in the EPC.

2 shows an air interface protocol of an LTE system for a control plane. 3 shows an air interface protocol of an LTE system for a user plane.

The layer of the air interface protocol between the UE and the E-UTRAN is based on the lower three layers of the open system interconnection (OSI) model, which is well known in communication systems, and includes L1 (first layer), L2 (second layer), and L3 (third layer). Hierarchical). The air interface protocol between the UE and the E-UTRAN may be horizontally divided into a physical layer, a data link layer, and a network layer, and vertically a protocol stack for transmitting control signals. ) Can be divided into a control plane and a user plane which is a protocol stack for transmitting data information. Layers of the radio interface protocol may exist in pairs in the UE and the E-UTRAN, which may be responsible for data transmission of the Uu interface.

The physical layer (PHY) belongs to L1. The physical layer provides an information transmission service to a higher layer through a physical channel. The physical layer is connected to a higher layer of a media access control (MAC) layer through a transport channel. Physical channels are mapped to transport channels. Data may be transmitted between the MAC layer and the physical layer through a transport channel. Data between different physical layers, that is, between the physical layer of the transmitter and the physical layer of the receiver may be transmitted using radio resources through a physical channel. The physical layer may be modulated using an orthogonal frequency division multiplexing (OFDM) scheme, and utilizes time and frequency as radio resources.

The physical layer uses several physical control channels. A physical downlink control channel (PDCCH) reports resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH to the UE. The PDCCH may carry an uplink grant to report to the UE regarding resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for the PDCCH and is transmitted every subframe. A physical hybrid ARQ indicator channel (PHICH) carries a HARQ ACK (non-acknowledgement) / NACK (non-acknowledgement) signal for UL-SCH transmission. A physical uplink control channel (PUCCH) carries UL control information such as HARQ ACK / NACK, a scheduling request, and a CQI for downlink transmission. The physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH).

The physical channel includes a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe consists of a plurality of symbols in the time domain. One subframe consists of a plurality of resource blocks (RBs). One resource block is composed of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols of the corresponding subframe for the PDCCH. For example, the first symbol of the subframe may be used for the PDCCH. The PDCCH may carry dynamically allocated resources, such as a physical resource block (PRB) and modulation and coding schemes (MCS). A transmission time interval (TTI), which is a unit time at which data is transmitted, may be equal to the length of one subframe. One subframe may have a length of 1 ms.

The transport channel is classified into a common transport channel and a dedicated transport channel depending on whether the channel is shared or not. A DL transport channel for transmitting data from a network to a UE includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, and a DL-SCH for transmitting user traffic or control signals. And the like. The DL-SCH supports dynamic link adaptation and dynamic / semi-static resource allocation by varying HARQ, modulation, coding and transmit power. In addition, the DL-SCH may enable the use of broadcast and beamforming throughout the cell. System information carries one or more system information blocks. All system information blocks can be transmitted in the same period. Traffic or control signals of a multimedia broadcast / multicast service (MBMS) are transmitted through a multicast channel (MCH).

The UL transport channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message, a UL-SCH for transmitting user traffic or a control signal, and the like. The UL-SCH can support dynamic link adaptation due to HARQ and transmit power and potential changes in modulation and coding. In addition, the UL-SCH may enable the use of beamforming. RACH is generally used for initial connection to a cell.

The MAC layer belonging to L2 provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The MAC layer provides a mapping function from a plurality of logical channels to a plurality of transport channels. The MAC layer also provides a logical channel multiplexing function by mapping from multiple logical channels to a single transport channel. The MAC sublayer provides data transfer services on logical channels.

The logical channel may be divided into a control channel for information transmission in the control plane and a traffic channel for information transmission in the user plane according to the type of information to be transmitted. That is, a set of logical channel types is defined for other data transfer services provided by the MAC layer. The logical channel is located above the transport channel and mapped to the transport channel.

The control channel is used only for conveying information in the control plane. The control channel provided by the MAC layer includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a dedicated control channel (DCCH). BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel used for transmitting paging information and paging a terminal whose cell-level location is not known to the network. CCCH is used by the terminal when there is no RRC connection with the network. MCCH is a one-to-many downlink channel used to transmit MBMS control information from the network to the terminal. DCCH is a one-to-one bidirectional channel used by the terminal for transmitting dedicated control information between the terminal and the network in an RRC connection state.

The traffic channel is used only for conveying information in the user plane. The traffic channel provided by the MAC layer includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). DTCH is used for transmission of user information of one UE in a one-to-one channel and may exist in both uplink and downlink. MTCH is a one-to-many downlink channel for transmitting traffic data from the network to the terminal.

The uplink connection between the logical channel and the transport channel includes a DCCH that can be mapped to the UL-SCH, a DTCH that can be mapped to the UL-SCH, and a CCCH that can be mapped to the UL-SCH. The downlink connection between the logical channel and the transport channel is a BCCH that can be mapped to a BCH or DL-SCH, a PCCH that can be mapped to a PCH, a DCCH that can be mapped to a DL-SCH, a DTCH that can be mapped to a DL-SCH, MCCH that can be mapped to MCH and MTCH that can be mapped to MCH.

The RLC layer belongs to L2. The function of the RLC layer includes adjusting the size of the data by segmentation / concatenation of the data received from the upper layer in the radio section such that the lower layer is suitable for transmitting data. In order to guarantee the various QoS required by the radio bearer (RB), the RLC layer is divided into three modes: transparent mode (TM), unacknowledged mode (UM) and acknowledged mode (AM). Provides three modes of operation. AM RLC provides retransmission through automatic repeat request (ARQ) for reliable data transmission. Meanwhile, the function of the RLC layer may be implemented as a functional block inside the MAC layer, in which case the RLC layer may not exist.

The packet data convergence protocol (PDCP) layer belongs to L2. The PDCP layer introduces an IP packet, such as IPv4 or IPv6, over a relatively low bandwidth air interface to provide header compression that reduces unnecessary control information so that the transmitted data is transmitted efficiently. Header compression improves transmission efficiency in the wireless section by transmitting only the information necessary for the header of the data. In addition, the PDCP layer provides security. Security functions include encryption to prevent third party inspection and integrity protection to prevent third party data manipulation.

The radio resource control (RRC) layer belongs to L3. The RRC layer at the bottom of L3 is defined only in the control plane. The RRC layer serves to control radio resources between the terminal and the network. To this end, the UE and the network exchange RRC messages through the RRC layer. The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of RBs. RB is a logical path provided by L1 and L2 for data transmission between the terminal and the network. That is, RB means a service provided by L2 for data transmission between the UE and the E-UTRAN. Setting up an RB means defining the characteristics of the radio protocol layer and channel to provide a particular service, and determining each specific parameter and method of operation. RBs may be classified into two types: signaling RBs (SRBs) and data RBs (DRBs). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

Referring to FIG. 2, the RLC and MAC layers (end at the eNB at the network side) may perform functions such as scheduling, ARQ and HARQ. The RRC layer (ended at the eNB at the network side) may perform functions such as broadcast, paging, RRC connection management, RB control, mobility function, and UE measurement report / control. The NAS control protocol (terminated at the gateway's MME at the network side) may perform functions such as SAE bearer management, authentication, LTE_IDLE mobility handling, paging initiation at LTE_IDLE, and security control for signaling between the terminal and the gateway.

Referring to FIG. 3, the RLC and MAC layer (end at the eNB at the network side) may perform the same function as the function in the control plane. The PDCP layer (terminating at the eNB at the network side) may perform user plane functions such as header compression, integrity protection and encryption.

Hereinafter, the 5G network structure will be described.

4 shows the structure of a 5G system.

In the case of an Evolved Packet Core (EPC), which is a core network structure of an existing Evolved Packet System (EPS), an entity such as a mobility management entity (MME), a serving gateway (S-GW), and a packet data network gateway (P-GW) Each function, reference point, protocol, etc. are defined.

On the other hand, in the case of a 5G core network (or NextGen core network), functions, reference points, protocols, etc. are defined for each network function (NF). That is, 5G core network does not define functions, reference points, protocols, etc. for each entity.

Referring to FIG. 4, the 5G system structure includes one or more UEs 10, a Next Generation-Radio Access Network (NG-RAN), and a Next Generation Core (NGC).

The NG-RAN may include one or more gNBs 40, and a plurality of terminals may exist in one cell. The gNB 40 provides the terminal with the control plane and the end point of the user plane. The gNB 40 generally refers to a fixed station communicating with the terminal 10 and may be referred to as other terms such as a base station (BS), a base transceiver system (BTS), an access point, and the like. . One gNB 40 may be arranged per cell. There may be one or more cells within coverage of the gNB 40.

The NGC may include an Access and Mobility Function (AMF) and a Session Management Function (SMF) that are responsible for the functions of the control plane. The AMF may be responsible for the mobility management function, and the SMF may be responsible for the session management function. The NGC may include a user plane function (UPF) that is responsible for the function of the user plane.

An interface for user traffic transmission or control traffic transmission may be used. Terminal 10 and gNB 40 may be connected by an NG3 interface. The gNBs 40 may be interconnected by Xn interface. Neighboring gNBs 40 may have a mesh network structure with an Xn interface. The gNBs 40 may be connected to the NGC by the NG interface. The gNBs 40 may be connected to the AMF by the NG-C interface and may be connected to the UPF by the NG-U interface. The NG interface supports a many-to-many-relation between gNB 40 and MME / UPF 50.

The gNB host may determine functions for radio resource management, IP header compression and encryption of user data stream, and routing to AMF from information provided by the terminal. Selection of an AMF at UE attachment when no routing to an AMF can be determined from the information provided by the UE, Routing of User Plane data to one or more UPFs towards UPF (s)), Scheduling and transmission of paging messages (originated from the AMF), transmission and scheduling of system broadcast information (derived from AMF or O & M) Scheduling and transmission of system broadcast information (originated from the AMF or O & M), or setting up and measuring measurement reports for scheduling and mobility (Me It can perform functions such as asurement and measurement reporting configuration for mobility and scheduling.

Access and Mobility Function (AMF) hosts can be used for NAS signaling termination, NAS signaling security, AS Security control, and inter CN node signaling for mobility between 3GPP access networks. node signaling for mobility between 3GPP access networks), IDLE mode UE reachability (including control and execution of paging retransmission), UE in ACTIVE mode and IDLE mode Tracking Area list management (for UE in idle and active mode), AMF selection for handovers with AMF change, Access Authentication, Or perform key functions such as access authorization including check of roaming rights. The.

A user plane function (UPF) host is an anchor point for Intra- / Inter-RAT mobility (when applicable), an external PDU session point for the interconnection to the data network (if applicable). (External PDU session point of interconnect to Data Network), Packet routing & forwarding, Packet inspection and User plane part of Policy rule enforcement, Traffic usage reporting ( Traffic usage reporting, Uplink classifier to support routing traffic flows to a data network, Branching point to support multi- homed PDU session, QoS handling for the user plane, e.g. packet filtering, gating, QoS handling for user plane, eg packet filtering, gating, UL / DL rate enforcement, uplink traffic verification (SDF to QoS flow mapping), transport level packet marking in downlink and uplink It can perform main functions such as packet marking in the uplink and downlink, or downlink packet buffering and downlink data notification triggering.

The Session Management Function (SMF) host is responsible for session management, UE IP address allocation and management, selection and control of UP functions, and traffic to the appropriate destinations. Configure traffic steering at UPF to route traffic to proper destination, control part of policy enforcement and QoS, or downlink data notification Can perform key functions such as

The system information will be described below.

5 shows an example in which a master information block (MIB), a system information block (SIB1), and other system information blocks (SIB) are transmitted.

The LTE cell broadcasts the basic parameters necessary for the operation of the IDLE_MODE terminal and the CONNECTED_MODE terminal into a plurality of information blocks. Examples of information blocks include MIBs, SIB1, SIB2, and other System Information Blocks (SIBn).

The MIB includes the most basic parameters necessary for the terminal to access the cell. Referring to FIG. 5, the MIB message is broadcasted through the BCH at a period of 40 ms, and the MIB transmission is repeated in all radio frames within the 40 ms period. The terminal receives the SIB message using the parameter received from the MIB.

There are several types of SIBs.

SIB1 includes information related to cell access, and in particular, includes scheduling information of other SIBs SIB2 to SIBn except SIB1. SIBs having the same transmission period among other SIs except SIB1 are included in the same system information (SI) message and transmitted. Therefore, the scheduling information includes a mapping relationship between each SIB and SI message. The SI message is transmitted in a window of the time domain (SI-window), and each SI message is associated with one SI-window. Since SI-windows of different SIs do not overlap, only one SI message is transmitted in any SI-window. Therefore, the scheduling information includes the length of the SI-window and the SI transmission period. The time / frequency at which the SI message is transmitted is determined by the dynamic scheduling of the base station. SIB1 is broadcast on a downlink common channel (DL-SCH) in eight radio frame periods (ie, 80 ms periods), and SIB1 is repeatedly retransmitted on subframe 5 of a radio frame of SFN mod 2 within an 80 ms period.

SIB2 includes information necessary for the terminal to access the cell. This includes information about uplink cell bandwidth, random access parameters, parameters related to uplink power control, and the like.

SIB3 includes cell reselection information. SIB4 includes frequency information of a serving cell and intra frequency information of a neighbor cell related to cell reselection. SIB5 includes information on another E-UTRA frequency and information on inter frequencies of neighboring cells related to cell reselection. SIB6 includes information on UTRA frequency and information on UTRA neighbor cells related to cell reselection. SIB7 includes information on GERAN frequencies related to cell reselection. SIB8 includes information about a neighbor cell.

SIB9 includes an ID of a Home eNodeB (HeNB). SIB10 to SIB12 include public warning messages, for example earthquake warnings. SIB14 is used to support enhanced access barring and controls terminals accessing a cell. SIB15 includes information required for MBMS reception of an adjacent carrier frequency. SIB16 includes GPS time and Coordinated Universal Time (UTC) related information. SIB17 includes RAN assistance information.

Not all SIBs should always exist. For example, SIB9 is not needed in the mode in which the HeNB is constructed by the operator, and SIB13 is not necessary unless the MBMS is provided in the cell.

Hereinafter, random access will be described.

Random access is used for the terminal to obtain uplink synchronization with the base station or receive uplink radio resources. After the power is turned on, the terminal acquires downlink synchronization with the initial cell and receives system information. From the system information, a set of available random access preambles and information about radio resources used for transmission of the random access preambles are obtained. The radio resource used for transmission of the random access preamble may be specified as a combination of a radio frame and / or at least one or more subframes. The terminal transmits a random access preamble randomly selected from the set of random access preambles, and the base station receiving the random access preamble sends a TA (timing alignment) value for uplink synchronization to the terminal through a random access response. As a result, the terminal acquires uplink synchronization.

That is, the base station allocates a designated random access preamble to a specific terminal, and the terminal performs non-contention random access with the corresponding random access preamble. That is, in the process of selecting a random access preamble, a contention-based random access using a randomly selected one by a terminal within a specific set and a non-competitive random access using a random access preamble allocated by a base station only to a specific terminal There can be. Non-competitive random access may be used when requested by a procedure for handover or a command of a base station.

6 shows a contention-based random access procedure.

Referring to FIG. 6, the terminal randomly selects one random access preamble from a set of random access preambles indicated by system information or a handover command. In operation S610, a radio resource capable of transmitting the random access preamble is selected to transmit the selected random access preamble. The radio resource may be a specific subframe, which may be to select a physical random access channel (PRACH).

After the random access preamble transmission, the terminal attempts to receive a random access response in the random access response receiving window indicated by the system information or the handover command, and accordingly receives a random access response (S620). The random access response is transmitted in a MAC PDU format, and the MAC PDU may be transmitted in a physical downlink shared channel (PDSCH). In addition, the physical downlink control channel (PDCCH) is also delivered in order for the terminal to properly receive the information delivered to the PDSCH. That is, the PDCCH includes information of a terminal receiving the PDSCH, frequency and time information of radio resources of the PDSCH, a transmission format of the PDSCH, and the like. Once the UE succeeds in receiving the PDCCH delivered to it, the UE properly receives the random access response transmitted to the PDSCH based on the information of the PDCCH.

The random access response may include a random access preamble identifier (ID), an UL grant (uplink radio resource), a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and a time alignment command (TAC). Since one random access response may include random access response information for one or more terminals, a random access preamble identifier may be included to indicate to which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. The TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a random access-radio network temporary identifier (RA-RNTI).

When receiving the random access response valid to the terminal, the terminal processes the information included in the random access response, and performs the scheduled transmission to the base station (S630). That is, the terminal applies the TAC and stores the temporary C-RNTI. In addition, by using the UL Grant, data or newly generated data stored in the buffer of the terminal is transmitted to the base station. In this case, information that can identify the terminal should be included. This is because, in the contention-based random access procedure, the base station cannot determine which terminals perform random access, and thus it is necessary to identify the terminal in order to resolve the collision.

There are two methods for including the information identifying the terminal. If the UE already has a valid cell identifier assigned in the cell before performing random access, the UE transmits its cell identifier through the UL Grant. On the other hand, if a valid cell identifier has not been allocated before the random access procedure, the terminal transmits its own unique identifier (eg, S-TMSI or Random ID). In general, the unique identifier is longer than the cell identifier. If the terminal transmits data through the UL Grant, it initiates a timer (contention resolution timer) for conflict resolution.

After receiving the random access response, the terminal transmits data including its identifier through the allocated UL Grant, and waits for an instruction of the base station to resolve the collision (S640). That is, it attempts to receive a PDCCH to receive a specific message. Two methods may be proposed as a method of receiving a PDCCH. As mentioned above, when its identifier transmitted through the UL Grant is a cell identifier, it may attempt to receive the PDCCH using its cell identifier. In this case, if the PDCCH is received through its cell identifier before the conflict resolution timer expires, the UE determines that the random access has been normally performed and terminates the random access. If the identifier transmitted through the UL Grant is a unique identifier, it attempts to receive the PDCCH using the temporary C-RNTI included in the random access response. In this case, if the PDCCH is received through the temporary cell identifier before the conflict resolution timer expires, the data transmitted by the PDSCH indicated by the PDCCH is checked. If the unique identifier is included in the data, the terminal may determine that the random access is normally performed and may terminate the random access.

7 shows a non-competition based random access procedure.

Unlike contention-based random access, contention-free random access may be terminated by the terminal receiving a random access response.

Non-competition based random access may be initiated by request, such as handover and / or command of a base station. However, in the above two cases, contention based random access may also be performed.

The terminal is assigned a designated random access preamble with no possibility of collision from the base station. The allocation of the random access preamble may be performed through the handover command and the PDCCH command (S710).

After receiving the random access preamble designated for the UE, the UE transmits the corresponding random access preamble to the base station (S720).

When the base station receives the random access preamble, the base station transmits a random access response to the terminal in response (S730). The procedure related to the random access response may refer to S620 of FIG. 6 described above.

On the other hand, the number of system information blocks continues to increase. Since the use of radio resources is required for broadcasting the system information blocks, as the number of system information blocks increases, the amount of radio resources required for broadcasting the system information blocks also increases. To solve this problem, a new type of system information has been proposed.

8 shows a procedure for the terminal to receive a new type of system information.

Referring to FIG. 8, the new type of system information may be divided into minimum system information and other system information. The minimum system information may be broadcast periodically. The minimum system information may include basic information necessary for initial access to the cell and information for obtaining other system information that is provisioned or periodically broadcast on an on-demand basis. The minimum system information may include at least one of a SFN, a list of PLMNs, a cell ID, a cell camping parameter, and a RACH parameter. If the network allows an on-demand mechanism, the parameters needed to request other system information may be included in the minimum system information. The other system information may mean all system information that is not broadcast in the minimum system information.

Hereinafter, the RRC_INACTIVE state of the terminal will be described.

In the NR standardization discussion, the RRC_INACTIVE state is newly introduced in addition to the existing RRC_CONNETED state and RRC_IDLE state. The RRC_INACTIVE state is a state introduced to efficiently manage a specific terminal (eg, mMTC terminal). The terminal in the RRC_INACTIVE state performs a radio control procedure similar to the terminal in the RRC_IDLE state to reduce power consumption. However, the terminal in the RRC_INACTIVE state maintains the connection state between the terminal and the network similarly to the RRC_CONNECTED state in order to minimize the control procedure required when transitioning to the RRC_CONNECTED state. In the RRC_INACTIVE state, the radio connection resources are released, but the wired connection can be maintained. For example, in the RRC_INACTIVE state, radio access resources may be released, but the NG interface between gNB and NGC or the S1 interface between eNB and EPC may be maintained. In the RRC_INACTIVE state, the core network recognizes that the terminal is normally connected to the base station. On the other hand, the base station may not perform connection management for the terminal in the RRC_INACTIVE state.

In case of a UE in a lightly connected mode, in order to hide state transition and mobility from the core network, the MME may maintain the S1 connection of the activated UE. In other words, in case of the UE in the RRC_INACTIVE state, in order to hide state transition and mobility from the Next Generation Core (NGC), the AMF may maintain the NG connection of the activated UE. In the present specification, the RRC_INACTIVE state may be used in a concept similar to a lightly connected mode, a lightly connected mode, or a semi-connected mode.

Hereinafter, a 5G RAN deployment scenario will be described.

5G RAN is a non-centralized deployment scenario and co-sited deployment according to the type of base station functions deployed in a central unit and a distributed unit, and coexistence with 4G base stations. It may be divided into a Deployment with E-UTRA scenario and a Centralized Deployment scenario. In this specification, 5G RAN, gNB, Next Generation NodeB, New RAN, and NR BS (New Radio Base Station) may mean a base station newly defined for 5G.

9 shows a scenario of separated base station deployment (Centralized Deployment).

Referring to FIG. 9, the gNB may be divided into a central unit and a distribution unit. That is, gNB may be separated and operated hierarchically. The central unit may perform the function of the upper layers of the base station, and the distributed unit may perform the function of the lower layers of the base station.

10 illustrates a functional split between a central unit and a distributed unit in a split base station deployment scenario.

Referring to FIG. 10, for option 1, the RRC layer is in the central unit and the PDCP layer, RLC layer, MAC layer, physical layer and RF are in the distributed unit. For option 2, the RRC layer and PDCP layer are in the central unit and the RLC layer, MAC layer, physical layer and RF are in the distributed unit. For option 3, the RRC layer, PDCP layer and RLC upper layer are in the central unit and the RLC lower layer, MAC layer, physical layer and RF are in the distributed unit. For option 4, the RRC layer, PDCP layer and RLC layer are in the central unit and the MAC layer, physical layer and RF are in the distributed unit. For option 5, the RRC layer, PDCP layer, RLC layer and MAC upper layer are in the central unit and the MAC lower layer, physical layer and RF are in the distributed unit. For option 6, the RRC layer, PDCP layer, RLC layer and MAC layer are in the central unit and the physical layer and RF are in the distributed unit. For option 7, the RRC layer, PDCP layer, RLC layer, MAC layer and upper physical layer are in the central unit, and the lower physical layer and RF are in the distributed unit. For option 8, the RRC layer, PDCP layer, RLC layer, MAC layer and physical layer are in the central unit and the RF is in the distributed unit.

Hereinafter, in the present specification, the central unit may be referred to as a CU, and the distribution unit may be referred to as a DU. The CU may be a logical node hosting a radio resource control (RRC), a service data adaptation protocol (SDAP) and a packet data convergence protocol (PDCP) layer of the gNB, and the DU may be a radio link control (RLC) of the gNB. It may be a logical node that hosts a media access control (MAC) and a physical (PHY) layer. Alternatively, the CU may be a logical node hosting the RRC and PDCP layers of en-gNB.

On the other hand, considering that the information generated in the RRC layer is transmitted to the terminal, the generated information should be transmitted to the terminal through the DU. Since system information to be broadcast is also generated at the RRC layer of the CU, signaling between the CU and the DU may be required for the DU to broadcast the system information. For example, when a CU receives a system information request from a terminal through a DU, signaling between the CU and the DU may be necessary for the DU to broadcast the system information. However, in the CU-DU split scenario, there is no procedure for the DU to transmit the system information requested by the terminal to the terminal. Hereinafter, a method for providing system information and a device supporting the same in a CU-DU partitioning scenario will be described according to an embodiment of the present invention.

11 illustrates a procedure for providing system information according to an embodiment of the present invention.

Referring to FIG. 11, in step S1110, the DU of the base station may receive system information from the CU of the base station. The system information may be received via the F1 interface. The F1 interface may mean an interface between a CU and a DU. The system information may be system information owned by the CU of the base station. The DU of the base station may receive from the CU all other system information except for SIB1 among the system information held by the CU. System information held by the CU may be included in the RRC container. The system information held by the CU of the base station may be transmitted from the CU of the base station to the DU of the base station in the F1 setup procedure. The system information may be included in an F1 setup response message.

Additionally, the DU of the base station may receive information related to the system information from the CU of the base station. The information related to the system information includes a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, and broadcast activation. ), DU ID, cell ID, or beam ID.

For example, the F1 setup response message may be defined as shown in Table 1.

IE / Group Name Presence Range Semantics description Criticality Assigned Criticality Message Type M YES reject Transaction ID M YES reject Cells to be Activated List 0 .. 1 > Cells to be Activated List Item 1 .. < maxCellingNBDU> List of cells to be activated YES reject >> NCGI M - - >> gNB-CU System Information M RRC container with system information owned by gNB-CU - - >> PCI O Physical Cell ID - -

Referring to Table 1, the F1 setup response message transmitted from the CU to the DU may include gNB-CU System Information. The gNB-CU System Information may be an RRC container including system information held by a CU. For example, the gNB-CU System Information may include all other system information except SIB1 among the system information held by the CU.

In operation S1120, the DU of the base station may receive a request for system information from the terminal. The terminal may be in an RRC_INACTIVE state. The terminal may be in an RRC_IDLE state. The system information request by the terminal may be included in message 3 in a random access procedure. When a request for system information is transmitted through message 3, the DU of the base station may not interpret the message 3 because there is no RRC layer. Therefore, the DU of the base station needs to send message 3 to the base station CU. The system information may be on-demand system information or other system information.

In step S1130, the DU of the base station may transmit a request for system information received from the terminal to the CU. A message including a container to piggyback the request for system information may be transmitted from the DU to the CU. The request for the system information may be included in an initial UL RRC message transfer message. The initial UL RRC message delivery message may be transmitted by the DU to deliver an initial layer 3 message to the CU on the F1 interface.

For example, the initial UL RRC message transfer message may be defined as shown in Table 2.

IE / Group Name Presence Range Semantics description Criticality Assigned Criticality Message Type M YES ignore gNB-DU UE F1AP ID M YES reject NCGI M NG-RAN Cell Global Identifier (NCGI) YES reject C-RNTI C-RNTI allocated at the gNB-DU YES reject RRC-Container M YES reject DU to CU RRC Container O CellGroupConfig IE. Required at least to carry SRB1 configuration YES reject

In step S1140, the DU of the base station may receive a message from the CU instructing to broadcast the requested system information. The message may be an SI broadcast request message. The message may be a system information delivery command message. The message may include information indicating the requested system information. For example, the message may include an identifier, index or number for the requested system information. For example, the message may include Other SI type. Accordingly, the DU may know that system information corresponding to the other system information type should be broadcast. In addition, the message may include timing information for broadcasting. The timing information for the broadcast may be a time interval for broadcast of other system information.

For example, the SI broadcast request message or the system information delivery command message may be defined as shown in Table 3.

IE / Group Name Presence Range IE  type and reference Semantics description Criticality Assigned Criticality Message Type M YES reject NCGI M NR cell identifier - SI type list One > SI type item IEs One ..  <maxnoofSITypes> >> Other SI Type M ENUMERATED Other SI Type YES reject >> Broadcast Time Interval M INTEGER Time interval for broadcasting of other si FFS FFS

Referring to Table 3, the CU of the base station may transmit a message including the other system information type to the DU, and the DU may broadcast system information corresponding to the other system information type. In addition, the CU of the base station may transmit a message including the broadcast time interval to the DU, and the DU may broadcast system information corresponding to the other system information type based on the broadcast time interval.

In operation S1150, based on the received message, the DU of the base station may provide the requested system information to the terminal. The system information may be provided to the terminal through broadcast signaling or dedicated signaling.

According to an embodiment of the present invention, the CU may provide the DU with information necessary for broadcasting system information and system information and system information held by the CU. The DU receiving the request for system information from the terminal may transmit the request to the CU, and may receive information indicating the system information that needs to be broadcasted or transmitted from the CU. As the CU provides information related to the SIB to the DU in advance, signaling between the CU and the DU due to the system information request of the UE may be reduced. In addition, as the CU instructs the DU only of the type of system information to be broadcast, signaling between the CU and the DU due to the system information request of the UE may be reduced.

12 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

According to an embodiment of the present invention, the CU may provide an indication for the requested SIB to the DU. Alternatively, the CU may provide the DU with information related to the requested SIB. For example, when the DU receives a system information request from the UE through message 3 in a random access procedure, an indication of the requested SIB or information related to the requested SIB may be provided to the DU from the CU.

According to an embodiment of the present invention, during the F1 setup procedure, the CU may provide the DU with information related to some or all of the SIBs supported by the CU. For example, the CU may provide the DU with information related to all of the system information owned by the CU. For example, the CU may provide the DU with all other system information except SIB1 among system information owned by the CU.

According to an embodiment of the present invention, if the CU determines to update the information related to the SIB, the CU may transmit information related to the updated SIB to the DU. In addition, if there is no request for on-demand system information for the requested SIB, the DU may release information related to the requested SIB.

Referring to FIG. 12, in step S1201, when the F1 interface is set up, the CU may transmit a message to the DU including information related to all the SIBs provided by the CU. Alternatively, the CU may transmit a message to the DU including information related to some SIBs provided by the CU. For example, the information related to the partial SIB may be minimum system information or system information about the SIB frequently requested by the terminal. The information related to the some SIB may be transmitted to efficiently manage the resources of the DU for storing the information related to the SIB. The message may be an F1 Setup Response message or an F1 Setup Request message. For example, the CU may send a message to the DU including information related to the SIBx.

Information related to the SIB included in the message may be provided for each SIB. The information related to the SIB includes a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, and broadcast activation. It may include at least one of DU ID, cell ID or beam ID.

The information related to the SIB may include system information and information necessary for broadcasting the system information in the DU. The container may be used to transmit system information from the CU to the DU including one or more parameters to be broadcast. The timing information for the broadcast may be information or time for assisting scheduling for broadcasting system information in the DU. For example, the timing information for broadcasting may include at least one of a length of a window in which system information is broadcast, a number of times in which system information is broadcast, or a position in the window when system information is broadcast. For each parameter in the SIB, there may be timing information for broadcasting for each parameter, which may have different values. The logical channel related information may include logical channel information for indicating a logical channel for transmitting system information. For example, the logical channel information may be a logical channel ID. The broadcast activation may indicate whether the provided system information is broadcast. The broadcast activation may be set when system information is always broadcasted or frequently requested by the terminal. When the DU controls, manages or covers one or more cells, the F1 setup response message or F1 setup request message may include a cell ID for each cell. If the DU controls, manages or covers one or more beams, the F1 setup response message or F1 setup request message may include a beam ID for each beam.

In step S1202, after the F1 setup procedure is completed, the DU may broadcast system information related to the SIB on which the broadcast is activated.

In step S1203, the terminal may transmit a system information request to the DU to request on-demand system information. The system information request may be included in message 3 in a random access procedure. The terminal may be in an RRC_IDLE state. The terminal may be in an RRC_INACTIVE state. In the present specification, the on-demand system information may be system information provided through broadcast signaling or dedicated signaling at the request of the terminal.

In step S1204, upon receiving the system information request from the terminal, the DU may transmit the system information request to the CU. A message including a container for piggybacking the system information request may be transmitted from the DU to the CU. The message may be an initial UE message or a new message.

Upon receiving the message from the DU, the CU may identify the requested on-demand system information based on the received system information request. And, depending on whether the CU provided the DU with information related to all the SIBs supported by the CU in step S1201, two possible options may exist.

(1) Option A

If the CU has provided the DU with information related to all the SIBs held by the CU, in step S1205, the CU may transmit the information about the requested SIB to the DU. The information on the requested SIB may indicate the requested SIB. The information on the requested SIB may be an identifier, an index, or a number for the SIB identified based on the system information request. For example, the CU may send the SIB type to the DU. Through this, the CU may instruct the DU to broadcast the requested SIB, and the DU may broadcast system information related to the indicated SIB.

Additionally, in step S1205, the CU may send a message to the DU including a container to piggyback the response to the system information request. The message may be a downlink RRC transport message or a new message.

(2) Option B

If the CU provided the DU with some SIB-related information, and / or if the CU received a system information request for requesting an SIB that the CU did not provide to the DU, in step S1205a, the CU avoids responding to the system information request. The backing may send a message containing the container to the DU. The message may be a downlink RRC transport message or a new message.

In operation S1205b, the CU may transmit a message for providing information related to the requested SIB to the DU. For example, the CU may send a message to the DU including information related to SIBy. The message may be a system information broadcast request message or a new message. Information related to the SIB included in the message may be provided for each SIB. The information related to the SIB includes a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, and broadcast activation. It may include at least one of DU ID, cell ID or beam ID. Upon receiving the message from the CU, the DU may store information related to the requested SIB.

In step S1205c, the DU may transmit a system information broadcast response message or a new message to the CU. For the requested SIB, the response message may include at least one of an SIB ID, a DU ID, a cell ID, or a beam ID corresponding to the ID included in the message received in step S1205b. For SIB, if the ID included in the request message is not included in the response message, the CU indicates that the entity (eg, DU, cell and / or beam) indicated by the CU cannot broadcast the corresponding system information. It can be recognized.

In step S1206, when receiving a message from the CU, the DU may send a message 4 to the terminal.

In step S1207, the DU may broadcast system information related to the requested SIB. System information related to the requested SIB may be broadcast after transmission of message 4. For the SIB, if the DU stores a cell ID or a beam ID, the DU may broadcast system information related to the SIB in the beam or cell indicated by the ID.

In step S1208, if the CU determines to update the information related to the SIB, the CU may send a system information broadcast request message (SI Broadcast Request message) or a new message to the DU. The system information broadcast request message or the new message may include information related to the SIB for each SIB. For example, the CU may send a message to the DU including information related to the updated SIBz. For example, the CU may send a message to the DU containing information related to the SIBz to be updated. The information related to the SIB may include a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, or broadcast activation. It may include at least one of. The broadcast activation may indicate that system information related to SIBz is not broadcast.

In step S1209, upon receiving the message from the CU, the DU may replace the previously provided information associated with the SIB with the received one. The DU may transmit a system information broadcast response message (SI Broadcast Response message) including a SIB ID related to the updated SIB or a new message to the CU.

In step S1210, for a requested SIB, if there is no request for on-demand system information for a specific time, the DU can efficiently manage the resource of the DU for storing information related to the requested SIB. It may be determined whether to release the information related to the.

In step S1211, when determining release for the information related to the requested SIB, the DU sends a System Release Information (SI Release Indication) message or a new message to indicate that the DU no longer has information related to the SIB. Can transmit to the CU. The message may include an identifier, index, or number for the released SIB. For example, the message may include the type of SIB released. After transmitting the message, the DU may release information related to the indicated SIB.

According to an embodiment of the present invention, the CU may provide the DU with information necessary for broadcasting system information and system information. The information may basically be provided when supporting broadcasting of system information. Alternatively, the information may be provided at the request of the terminal. In addition, as the CU provides information related to the SIB to the DU in advance, signaling between the CU and the DU due to the on-demand system information request of the UE may be reduced. Furthermore, resources of the DU for storing information related to the requested SIB can be efficiently managed.

13 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

According to an embodiment of the present invention, using the F1 setup procedure, the CU may provide the DU with information related to some or all of the SIB provided by the CU. Additionally, if the CU receives a request from the DU for system information related to the SIB corresponding to the on-demand system information by the terminal, or if the CU decides to update the information related to the SIB, the CU is requested or updated. Information related to the SIB may be transmitted to the DU. Further, if there is no request for on-demand system information for the requested SIB, the DU may release information related to the requested SIB.

Referring to FIG. 13, in step S1301, when the F1 interface is set up, the CU may transmit a message to the DU including information related to all SIBs provided by the CU. Alternatively, the CU may transmit a message to the DU including information related to some SIBs provided by the CU. For example, the information related to the partial SIB may be minimum system information or system information about the SIB frequently requested by the terminal. The information related to the some SIB may be transmitted to efficiently manage the resources of the DU for storing the information related to the SIB. The message may be an F1 Setup Response message or an F1 Setup Request message. For example, the CU may send a message to the DU including information related to the SIBx.

Information related to the SIB included in the message may be provided for each SIB. The information related to the SIB includes a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, and broadcast activation. It may include at least one of DU ID, cell ID or beam ID.

The information related to the SIB may include system information and information necessary for broadcasting the system information in the DU. The container may be used to transmit system information from the CU to the DU including one or more parameters to be broadcast. The timing information for the broadcast may be information or time for assisting scheduling for broadcasting system information in the DU. For example, the timing information for broadcasting may include at least one of a length of a window in which system information is broadcast, a number of times in which system information is broadcast, or a position in the window when system information is broadcast. For each parameter in the SIB, there may be timing information for broadcasting for each parameter, which may have different values. The logical channel related information may include logical channel information for indicating a logical channel for transmitting system information. For example, the logical channel information may be a logical channel ID. The broadcast activation may indicate whether the provided system information is broadcast. The broadcast activation may be set when system information is always broadcasted or frequently requested by the terminal. When the DU controls, manages or covers one or more cells, the F1 setup response message or F1 setup request message may include a cell ID for each cell. If the DU controls, manages or covers one or more beams, the F1 setup response message or F1 setup request message may include a beam ID for each beam.

In step S1302, after the F1 setup procedure is completed, the DU may broadcast system information related to the SIB on which the broadcast is activated.

In operation S1303, the terminal may transmit a system information request to the DU to request on-demand system information. The system information request may be included in message 1 in a random access procedure. In order to request system information, the preamble transmitted by the terminal may be mapped to all SIBs. Alternatively, the preamble transmitted by the terminal may be mapped to one or more SIBs. This mapping may be broadcast by the DU or may be preset between the DU and the terminal. In addition, the UE may transmit a plurality of preambles in which each preamble is mapped to the SIB to the DU. The terminal may be in an RRC_IDLE state. The terminal may be in an RRC_INACTIVE state.

In step S1304, upon receiving the message from the terminal, the DU may identify whether the received on-demand system information can broadcast system information related to the SIB requested. If the DU can broadcast system information related to the SIB requested by the received on-demand system information, the DU may omit signaling with the CU. For example, where possible, steps S1305a, S1305b, and S1305c may be omitted. If the DU cannot broadcast system information related to the SIB requested by the received on-demand system information, the DU may perform signaling with the CU.

In step S1305a, the DU may send a message to the CU including information about the requested SIB. The information on the requested SIB may indicate the requested SIB. The information on the requested SIB may be an identifier, an index, or a number for the SIB identified based on the system information request. The message may be an on-demand system information indication message or a new message.

In step S1305b, upon receiving the message from the DU, the CU may identify the requested on-demand system information. In addition, the CU may transmit a message for providing information related to the requested SIB to the DU. For example, the CU may send a message to the DU including information related to SIBy. The message may be a system information broadcast request message or a new message. Information related to the SIB included in the message may be provided for each SIB. The information related to the SIB includes a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, and broadcast activation. It may include at least one of DU ID, cell ID or beam ID. Upon receiving the message from the CU, the DU may store information related to the requested SIB.

In step S1305c, the DU may transmit a system information broadcast response message or a new message to the CU. For the requested SIB, the response message may include at least one of an SIB ID, a DU ID, a cell ID, or a beam ID corresponding to the ID included in the message received in step S1305b. For SIB, if the ID included in the request message is not included in the response message, the CU indicates that the entity (eg, DU, cell and / or beam) indicated by the CU cannot broadcast the corresponding system information. It can be recognized.

In step S1306, the DU may send a message 2 to the terminal.

In step S1307, after transmitting message 2, the DU may broadcast system information related to the requested SIB. For the SIB, if the DU stores a cell ID or a beam ID, the DU may broadcast system information related to the SIB in the beam or cell indicated by the ID.

In step S1308, if the CU determines to update the information associated with the SIB, the CU may send a system information broadcast request message (SI Broadcast Request message) or a new message to the DU. The system information broadcast request message or the new message may include information related to the SIB for each SIB. For example, the CU may send a message to the DU including information related to the updated SIBz. For example, the CU may send a message to the DU containing information related to the SIBz to be updated. The information related to the SIB may include a SIB ID, a container including system information, timing information for broadcasting, logical channel related information, or broadcast activation. It may include at least one of. The broadcast activation may indicate that system information related to SIBz is not broadcast.

In step S1309, upon receiving the message from the CU, the DU may replace the previously provided information associated with the SIB with the received one. The DU may transmit a system information broadcast response message (SI Broadcast Response message) including a SIB ID related to the updated SIB or a new message to the CU.

In step S1310, for a requested SIB, if there is no request for on-demand system information for a specific time, the DU can efficiently manage the resource of the DU for storing information related to the requested SIB. It may be determined whether to release the information related to the.

In step S1311, when determining release for the information related to the requested SIB, the DU sends a System Release Information (SI Release Indication) message or a new message to indicate that the DU no longer has information related to the SIB. Can transmit to the CU. The message may include an identifier, index, or number for the released SIB. For example, the message may include the type of SIB released. After transmitting the message, the DU may release information related to the indicated SIB.

According to an embodiment of the present invention, the CU may provide the DU with information necessary for broadcasting system information and system information. The information may basically be provided when supporting broadcasting of system information. Alternatively, the information may be provided at the request of the terminal. In addition, as the CU provides information related to the SIB to the DU in advance, signaling between the CU and the DU due to the on-demand system information request of the UE may be reduced. Furthermore, resources of the DU for storing information related to the requested SIB can be efficiently managed.

14 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

According to an embodiment of the present invention, if the CU receives a request for grouped system information broadcast of the terminal through the DU, or if the CU determines to broadcast one or more grouped system information, the CU May transmit one or more grouped system information (eg, MIB, SIB1 and SIB2 in LTE) to the DU using a message for each grouped system information.

In step S1401, the terminal may transmit a system information request to the DU to request on-demand system information. The system information request may be included in message 1 in a random access procedure. In order to request system information, the preamble transmitted by the terminal may be mapped to all system information groups. Alternatively, the preamble transmitted by the terminal may be mapped to one or more system information groups. This mapping may be broadcast by the DU or may be preset between the DU and the terminal. In addition, the UE may transmit a plurality of preambles in which each preamble is mapped to a system information group, to the DU. The terminal may be in an RRC_IDLE state. The terminal may be in an RRC_INACTIVE state.

In operation S1402, upon receiving a message from the terminal, the DU may transmit a message including the requested system information group to the CU based on message 1 received from the terminal. The message may be an On-demand SI Indication message or a new message.

In step S1403, the CU receives an on-demand system information indication message or a new message including the system information group x, or if the CU decides to broadcast the system information group x, the CU requests to broadcast the system information group x. The message may be sent to the DU. The message may be a SIx Broadcast Request message or a new message. The x may mean a group x. For example, if system information group 2 and system information group 3 are to be broadcast, the CU may use the SI2 broadcast request message and the SI3 broadcast request message, respectively. The SIx broadcast request message or new message may include a system information group x, timing information for broadcasting, logical channel related information, DU ID, cell ID, and beam. It may include at least one of ID or on-demand SI related information.

The SIx broadcast request message or the new message may include information necessary for broadcasting the system information group x in the system information group x and the DU. The system information group x may include one or more parameters to be broadcast. The timing information for the broadcast may be information or time for assisting scheduling for broadcasting the system information group x in the DU. For each parameter in the system information group x, there may be timing information for broadcasting for each parameter, which may have different values. The logical channel related information may include logical channel information for indicating a logical channel for transmitting the system information group x. For example, the logical channel information may be a logical channel ID. When the DU controls, manages or covers one or more cells, the SIx broadcast request message or new message may include a cell ID for each cell. When the DU controls, manages, or covers one or more beams, the SIx broadcast request message or new message may include a beam ID for each beam. The on-demand system information related information may include at least one of a length of a window in which system information is broadcast, a number of times in which system information is broadcast, or a position in the window when system information is broadcast.

In step S1404, upon receiving the request message from the CU, the DU may transmit a SIx Broadcast Response message or a new message to the CU. The response message may include at least one of a DU ID, a cell ID, or a beam ID corresponding to the ID included in the request message in step S1403. If the ID included in the request message is not included in the response message, the CU can recognize that the entity (eg, DU, cell and / or beam) indicated by the CU cannot broadcast system information group x. have.

In operation S1405, upon receiving the request message from the CU, the DU may store information included in the request message. And, based on the stored information, the DU may broadcast the system information group x. If the SIx broadcast request message or the new message includes the cell ID or the beam ID, the DU may broadcast the system information group x in the beam or cell indicated by the ID. If the SIx broadcast request message or the new message includes the on-demand system information related information, the DU may have all the information included in the on-demand system information related information or the request message during the time of broadcasting the system information. Thereafter, the DU may remove or discard the on-demand system information related information or all the information.

In step S1406, the DU may broadcast the system information group x included in the request message from the CU.

According to an embodiment of the present invention, a CU may manage system information to be broadcast to a terminal within coverage of the CU. Alternatively, the CU may provide system information according to a request of the terminal.

15 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

According to an embodiment of the present invention, if the CU receives a request for grouped system information broadcast of the terminal through the DU, or if the CU determines to broadcast one or more grouped system information, the CU May send one or more grouped system information (eg, MIB, SIB1 and SIB2 in LTE) to the DU using one message including all grouped system information.

In step S1501, the terminal may transmit a system information request to the DU to request on-demand system information. The system information request may be included in message 1 in a random access procedure. In order to request system information, the preamble transmitted by the terminal may be mapped to all system information groups. Alternatively, the preamble transmitted by the terminal may be mapped to one or more system information groups. This mapping may be broadcast by the DU or may be preset between the DU and the terminal. In addition, the UE may transmit a plurality of preambles in which each preamble is mapped to a system information group, to the DU. The terminal may be in an RRC_IDLE state. The terminal may be in an RRC_INACTIVE state.

In operation S1502, upon receiving a message from the terminal, the DU may transmit a message including the requested system information group to the CU based on message 1 received from the terminal. The message may be an On-demand SI Indication message or a new message.

In step S1503, if the CU receives an on-demand system information indication message or new message including the system information group, or if the CU decides to broadcast one or more system information groups, the CU broadcasts one or more system information groups. A request message can be sent to the DU. The message may be an SI broadcast request message or a new message. The message may include information for each system information group.

For example, the message may include information about the first system information group and information about the second system information group. The information on the first system information group includes system information group 1, timing information for broadcasting, logical channel related information, DU ID, cell ID, beam It may include at least one of ID or on-demand SI related information. The information on the second system information group includes system information group 2, timing information for broadcasting, logical channel related information, DU ID, cell ID, It may include at least one of beam ID or on-demand SI related information.

The information on each system information group may include information necessary for broadcasting the system information group in the system information group and the DU. The system information group may include one or more parameters to be broadcast. The timing information for the broadcast may be information or time for assisting scheduling for broadcasting a system information group in the DU. For each parameter in the system information group, there may be timing information for broadcasting for each parameter, which may have different values. The logical channel related information may include logical channel information for indicating a logical channel for transmitting a system information group. For example, the logical channel information may be a logical channel ID. When the DU controls, manages or covers one or more cells, the SI broadcast request message or new message may include a cell ID for each cell. If the DU controls, manages or covers one or more beams, the SI broadcast request message or new message may include a beam ID for each beam. The on-demand system information related information may include at least one of a length of a window in which system information is broadcast, a number of times in which system information is broadcast, or a position in the window when system information is broadcast.

In step S1504, upon receiving the request message from the CU, the DU may transmit an SI broadcast response message or a new message to the CU. For each system information group, the response message may include at least one of a DU ID, a cell ID, or a beam ID corresponding to the ID included in the request message in step S1503. For example, for the first system information group, if the ID included in the request message is not included in the response message, the CU is determined by an entity (eg, DU, cell and / or beam) indicated by the CU. 1 It may be recognized that the system information group cannot be broadcast.

In operation S1505, upon receiving the request message from the CU, the DU may store information included in the first system information group and / or the second system information group. In addition, based on the stored information, the DU may broadcast the system information group 1 and / or the system information group 2. For example, for the first system information group, if the SI broadcast request message or the new message includes the cell ID or the beam ID, the DU may broadcast the system information group 1 in the beam or cell indicated by the ID. For example, if the SI broadcast request message or the new message includes on-demand system information related information for the first system information group, the DU may, during the time of broadcasting the system information for the first system information group, the first system. It may have all the information included in the request message for the information group or information related to the on-demand system information. Thereafter, the DU may remove or discard all information about the first system information group or information related to the on-demand system information.

In step S1506, the DU may broadcast the system information group 1 and / or the system information group 2 included in the information on the first system information group and / or the second system information group, respectively.

According to an embodiment of the present invention, a CU may manage system information to be broadcast to a terminal within coverage of the CU. Alternatively, the CU may provide system information to the DU according to the request of the terminal. Furthermore, because a plurality of system information can be provided to the DU at one time in one procedure, signaling between the CU and the DU can be reduced.

16 illustrates a procedure for providing on-demand system information according to an embodiment of the present invention.

According to an embodiment of the present invention, using the F1 setup procedure, the CU may provide the DU with grouped system information to be broadcasted provided by the CU. For example, the grouped system information may be MIB, SIB1 or SIB2 in LTE. Additionally, if the CU receives a request from the DU for grouped system information corresponding to on-demand system information by the terminal, or if the CU decides to update the grouped system information, the CU is requested or updated. Grouped system information may be transmitted to the DU.

Referring to FIG. 16, in step S1601, when the F1 interface is set up, the CU may transmit a message to the DU including all system information groups provided by the CU. Or, the CU may send a message to the DU including a group of system information provided by the CU. For example, the some system information group may be a minimum system information group or a system information group frequently requested by the terminal. The some system information group may be transmitted to efficiently manage resources of the DU for storing information related to the system information group. The message may be an F1 Setup Response message or an F1 Setup Request message. For example, the CU may send a message to the DU including information related to system information group x.

Information related to the system information group included in the message may be provided for each system information group. The information related to the system information group includes at least one of a system information group, timing information for broadcasting, logical channel related information, DU ID, cell ID, and beam ID. It may include any one.

The information related to the system information group may include information necessary for broadcasting the system information group in the system information group and the DU. The system information group may include one or more parameters to be broadcast. The timing information for the broadcast may be information or time for assisting scheduling for broadcasting a system information group in the DU. For example, the timing information for broadcasting may include at least one of a length of a window in which system information is broadcast, a number of times in which system information is broadcast, or a position in the window when system information is broadcast. For each parameter in the system information group, there may be timing information for broadcasting for each parameter, which may have different values. The logical channel related information may include logical channel information for indicating a logical channel for transmitting a system information group. For example, the logical channel information may be a logical channel ID. When the DU controls, manages or covers one or more cells, the F1 setup response message or F1 setup request message may include a cell ID for each cell. If the DU controls, manages or covers one or more beams, the F1 setup response message or F1 setup request message may include a beam ID for each beam.

After the F1 setup procedure is completed, the DU may broadcast system information based on the information received from the CU.

In operation S1602, the terminal may transmit a system information request to the DU to request on-demand system information. The system information request may be included in message 1 or message 3 in a random access procedure. In order to request system information, the preamble transmitted by the terminal may be mapped to all system information groups. Alternatively, the preamble transmitted by the terminal may be mapped to one or more system information groups. This mapping may be broadcast by the DU or may be preset between the DU and the terminal. In addition, the UE may transmit a plurality of preambles in which each preamble is mapped to a system information group, to the DU. The terminal may be in an RRC_IDLE state. The terminal may be in an RRC_INACTIVE state.

In operation S1603, upon receiving a message from the terminal, the DU may identify whether the received on-demand system information may be broadcast. If the DU is able to broadcast the received on-demand system information, the DU may broadcast system information corresponding to the requested on-demand system information.

In step S1604, if the DU has a part of the system information group provided by the CU, and the DU cannot broadcast the system information corresponding to the on-demand system information received from the terminal, the DU is in the message 1 or message 3 The message including the system information group requested by the UE may be transmitted to the CU. The message may be a system information on-demand indication message or a new message. The requested system information group may be related to the on-demand system information.

In step S1605, if the CU receives a system information on-demand indication message or a new message, or if the CU decides to update the system information group, the CU may send a message to the DU requesting or providing the updated system information group. have. For example, the CU may send a message to the DU that includes information related to the requested or updated system information group y. The message may be a system information broadcast request message or a new message. Information related to the system information group included in the message may be provided for each system information group. The information related to the system information group includes at least one of a system information group, timing information for broadcasting, logical channel related information, DU ID, cell ID, and beam ID. It may include any one.

In step S1606, when receiving a message from the CU, the DU may transmit a system information broadcast response message (SI Broadcast Response message) or a new message to the CU. For the requested or updated system information group y, the response message may include at least one of a DU ID, a cell ID, or a beam ID corresponding to the ID included in the message received in step S1605. For the system information group y, if the ID included in the request message is not included in the response message, the CU broadcasts the system information group y to an entity (eg, DU, cell and / or beam) indicated by the CU. You can see that you can't.

In step S1607, upon receiving a message from the CU, the DU may store information included in the system information group y. Alternatively, the DU may replace the previous information with information included in the system information group y. The DU may broadcast a system information group based on the stored or replaced information. For the system information group y, if a SI Broadcast Request message or a new message includes the cell ID or beam ID, the DU may broadcast the system information group y in the beam or cell indicated by the ID. have.

In step S1608, with respect to the system information group, if there is no request for on-demand system information for a specific time, the DU efficiently manages resources of the DU for storing information related to the system information group. All information related to can be released.

According to an embodiment of the present invention, the CU may provide the DU with system information to be broadcasted to a terminal within the coverage of the CU. Alternatively, the CU may provide system information to the DU according to the request of the terminal. Furthermore, as the CU provides information related to the system information group to the DU in advance, signaling between the CU and the DU due to the on-demand system information request of the terminal may be reduced.

17 is a block diagram illustrating a method in which a DU of a base station provides system information according to an embodiment of the present invention.

Referring to FIG. 17, in step S1710, the DU of the base station may receive the system information owned by the CU of the base station, which is held by the central unit (CU) of the base station, from the CU of the base station. have. The system information held by the CU of the base station may be included in a container and transmitted from the CU of the base station to the DU of the base station. The system information held by the CU of the base station may be transmitted from the CU of the base station to the DU of the base station in the F1 setup procedure. The system information received from the CU of the base station may be all system information except for SIB1 among the system information held by the CU of the base station.

The CU may be a logical node hosting a radio resource control (RRC), a service data adaptation protocol (SDAP), and a packet data convergence protocol (PDCP) layer of the base station, and the DU may be an RLC (RLC) of the base station. It may be a logical node hosting a radio link control (MAC), a media access control (MAC), and a physical (PHY) layer.

The system information may be on-demand system information broadcast by a request of the terminal. The system information may be other system information.

In step S1720, the DU of the base station may receive a request for the system information from the terminal. The request for the system information may be transmitted from the terminal to the DU of the base station in a random access procedure. The request for system information may be included in message 3.

The system information received from the CU of the base station may include the requested system information.

In addition, if the system information received from the CU of the base station does not include the requested system information, the DU of the base station may additionally receive the requested system information from the CU of the base station.

In addition, the DU of the base station may transmit a request for the system information to the CU of the base station. The request for the system information may be included in a container and transmitted from the DU of the base station to the CU of the base station.

In operation S1730, the DU of the base station may receive a message for commanding to broadcast the system information from the CU of the base station. The message instructing to broadcast the requested system information may include the type of the requested system information. The message instructing to broadcast the requested system information may include time information for broadcasting the requested system information. The time information may be a broadcast time interval.

In step S1740, the DU of the base station may broadcast the requested system information. Alternatively, the DU of the base station may transmit the requested system information to the terminal through dedicated signaling.

18 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The terminal 1800 includes a processor 1801, a memory 1802, and a transceiver 1803. The memory 1802 is connected to the processor 1801 and stores various information for driving the processor 1801. The transceiver 1803 is connected to the processor 1801 to transmit and / or receive a radio signal. The processor 1801 implements the proposed functions, processes, and / or methods. In the above-described embodiment, the operation of the terminal may be implemented by the processor 1801.

The DU 1810 of the base station includes a processor 1811, a memory 1812, and a transceiver 1813. The memory 1812 is connected to the processor 1811 and stores various information for driving the processor 1811. The transceiver 1813 is coupled to the processor 1811 to transmit and / or receive wireless signals. Processor 1811 implements the proposed functions, processes, and / or methods. In the above-described embodiment, the operation of the DU of the base station may be implemented by the processor 1811.

The CU 1820 of the base station includes a processor 1821, a memory 1822, and a transceiver 1823. The memory 1822 is connected to the processor 1821 and stores various information for driving the processor 1821. The transceiver 1823 is coupled to the processor 1821 to transmit and / or receive signals. Processor 1821 implements the proposed functions, processes, and / or methods. In the above-described embodiment, the operation of the CU of the base station may be implemented by the processor 1821.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The transceiver may include baseband circuitry for processing wireless signals. When the embodiment is implemented in software, the above technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

Based on the examples described above, various techniques in accordance with the present disclosure have been described with reference to the drawings and reference numerals. For convenience of description, each technique described a number of steps or blocks in a specific order, but the specific order of these steps or blocks does not limit the invention described in the claims, and each step or block may be implemented in a different order, or In other words, it is possible to be performed simultaneously with other steps or blocks. In addition, it will be apparent to those skilled in the art that the steps or blocks have not been described in detail, and that at least one other step may be added or deleted without departing from the scope of the invention.

The above-described embodiments include various examples. Those skilled in the art will appreciate that not all possible combinations of examples of the inventions can be described, and that various combinations can be derived from the description herein. Therefore, the protection scope of the invention should be judged by combining various examples described in the detailed description within the scope of the claims described below.

Claims (15)

In a method of broadcasting a system information (distributed unit) of a base station (DU) in a wireless communication system, Receiving from the CU of the base station the system information owned by the CU of the base station held by the central unit (CU) of the base station; Receiving a request for the system information from a terminal; Receiving a message from the CU of the base station, the message commanding to broadcast the system information; And Broadcasting the requested system information. The method of claim 1, The system information held by the CU of the base station is included in the container (container) is transmitted from the CU of the base station to the DU of the base station. The method of claim 1, The system information held by the CU of the base station is transmitted from the CU of the base station to the DU of the base station in the F1 setup procedure. The method of claim 1, The system information received from the CU of the base station includes the requested system information. The method of claim 1, If the system information received from the CU of the base station does not include the requested system information, receiving the requested system information from the CU of the base station. The method of claim 1, The system information received from the CU of the base station is all system information except for SIB1 of the system information held by the CU of the base station. The method of claim 1, And the message instructing to broadcast the requested system information includes the type of the requested system information. The method of claim 1, The request for the system information is transmitted from the terminal to the DU of the base station in a random access procedure. The method of claim 8, The request for system information is included in message 3. The method of claim 1, And wherein the message instructing to broadcast the requested system information includes time information for the broadcast of the requested system information. The method of claim 1, Transmitting the request for system information to a CU of the base station. The method of claim 11, The request for system information is included in a container and transmitted from the DU of the base station to the CU of the base station. The method of claim 1, The CU is a logical node hosting a radio resource control (RRC), a service data adaptation protocol (SDAP), and a packet data convergence protocol (PDCP) layer of the base station, and the DU is a radio link of the base station. and a logical node hosting a control, media access control (MAC), and physical (PHY) layer. The method of claim 1, The system information is on-demand system information (other system information) or other system information (on-demand system information) that is broadcast at the request of the terminal. In a distributed unit (DU) of a base station broadcasting system information in a wireless communication system, Memory; Transceiver; And a processor connecting the memory and the transceiver, wherein the processor Control the transceiver to receive from the CU of the base station the system information owned by the CU of the base station held by the central unit (CU) of the base station, Control the transceiver to receive a request for the system information from a terminal, Control the transceiver to receive a message from the CU of the base station commanding to broadcast the requested system information, and And the transceiver controls the transceiver to broadcast the requested system information.

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