KR20240085696A - Method and apparatus for operating control plane in communication system - Google Patents

Abstract

A control plane operation technology in a communication system is disclosed. A method of operating a central unit of a first base station in a communication system, comprising: receiving a request for preparation of a dual active protocol stack (DAPS) handover from a second base station; Transmitting DAPS handover indication information to the distribution unit of the first base station; Receiving a terminal context setup response message including primary DAPS handover parameter information required for the DAPS handover; Generating information necessary for the DAPS handover; And a method of operating a central unit of a first base station can be provided, including transmitting the information necessary for the DAPS handover to the second base station.

Description

Method and apparatus for operating a control plane in a communication system {METHOD AND APPARATUS FOR OPERATING CONTROL PLANE IN COMMUNICATION SYSTEM}

The present disclosure relates to control plane operation technology in a communication system, and more specifically, to the application of dual active protocol stack (DAPS), public warning system (PWS), etc. in a functionally separated base station. It is about control plane operation technology in a communication system that enables

With the advancement of information and communication technology, various wireless communication technologies can be developed. Representative wireless communication technologies may include long term evolution (LTE), new radio (NR), and 6th generation (6G) specified in the 3rd generation partnership project (3GPP) standard. LTE may be a wireless communication technology among 4G (4th Generation) wireless communication technologies, and NR may be a wireless communication technology among 5G (5th Generation) wireless communication technologies.

In order to handle the rapid increase in wireless data after the commercialization of the 4G communication system (e.g., a communication system supporting LTE), the frequency band of the 4G communication system (e.g., a frequency band below 6 GHz) as well as the 4G communication system A 5G communication system (e.g., a communication system supporting NR) that uses a frequency band higher than the frequency band (e.g., a frequency band of 6 GHz or higher) may be considered. The 5G communication system can support enhanced Mobile BroadBand (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

Meanwhile, 3GPP can propose the concept of a functionally separated base station. Here, functional separation may be a method of physically separating and operating one base station. Accordingly, functional separation may refer to a technology that separates the protocol stack based on a certain standard from the existing method of mounting all protocol stacks on one node and operates by mounting some protocol stacks on two or more nodes. A functionally separated base station can be largely composed of a distribution unit (DU) and a central unit (CU). 3GPP can define the control plane interface between distributed units and central units as F1AP (F1 application protocol). Such a functionally separated base station may require modification to the radio bearer to apply dual active protocol stack (DAPS), public warning system (PWS), etc.

The purpose of the present disclosure to solve the above problems is to provide a communication system that allows the application of a dual active protocol stack (DAPS), a public warning system (PWS), etc. in a functionally separated base station. To provide a control plane operation method and device.

A control plane operation method in a communication system according to the first embodiment of the present disclosure to achieve the above object is a method of operating a central unit of a first base station in a communication system, and is provided by a dual active protocol (DAPS) method from a second base station. stack) Receiving a handover preparation request message requesting preparation for handover; Transmitting a terminal context setup message including DAPS handover indication information to the distribution unit of the first base station; Receiving a terminal context setup response message including primary DAPS handover parameter information required for the DAPS handover generated based on the DAPS handover indication information from the distribution unit; Generating information necessary for the DAPS handover based on the first DAPS handover parameter information; And it may include transmitting a handover preparation request response message including the information necessary for the DAPS handover to the second base station.

Here, the DAPS handover indication information may be composed of DAPS handover setting information at the DRB (data radio bearer) level.

Here, the DAPS handover configuration information at the DRB level includes each DRB ID (identifier) information of a plurality of DRBs and DAPS bearer information indicating whether or not the DAPS handover is applied to each DRB ID. This can be done with DRB information.

Here, transmitting a terminal context setup message including DAPS handover instruction information to the distribution unit of the first base station includes generating the DAPS handover instruction information including DAPS handover configuration information at the DRB level; And it may include transmitting the terminal context setup message including the DAPS handover indication information to the distribution unit through an F1 application protocol (F1AP) interface.

Here, the step of generating information necessary for the DAPS handover based on the first DAPS handover parameter information includes secondary DAPS handover parameter information required for the DAPS handover based on the first DAPS handover parameter information. generating a; And it may include generating the information necessary for the DAPS handover consisting of the first DAPS handover parameter information and the second DAPS handover parameter information.

Here, receiving a PDCP early sequence number (SN) from the second base station for early data transmission and reception; Receiving data from the second base station; And it may further include transmitting the data to the terminal based on the PDCP early SN.

Meanwhile, the control plane operation method in the communication system according to the second embodiment of the present disclosure for achieving the above object is a method of operating the central unit of the base station in the communication system, and receives a warning message from the cell broadcast center. steps; And generating system information according to the type of the warning message and transmitting a warning request message including the system information to a distribution unit of the base station, wherein the system information is divided into a plurality of system information blocks (SIBs). In this case, the plurality of SIBs can be delivered to the distribution unit using the warning request message.

Here, generating system information according to the type of the warning message and transmitting it to the distribution unit of the base station using a warning request message includes: identifying the message type of the warning message; If the message type is a CMAS warning message including CMAS (commercial mobile alert system) warning content, generating SIB 8 including the CMAS warning content; And it may include transmitting the warning request message including the SIB 8 to the distribution unit.

Here, generating system information according to the type of the warning message and transmitting it to the distribution unit of the base station using a warning request message includes: identifying the message type of the warning message; If the message type is an ETWS (earthquake and tsunami warning system) warning message that includes the main and auxiliary parts of an ETWS (earthquake and tsunami warning system) warning, generating SIB 6 including the main part and generating SIB 7 including the auxiliary part. ; And it may include transmitting the warning request message including the SIB 6 and the SIB 7 to the distribution unit.

Here, the warning request message may be transmitted from the central unit to the distributed unit using the F1AP interface.

Here, when the system information consists of the plurality of SIBs, the central unit may transmit the warning request message including a plurality of indicators indicating the plurality of SIBs to the distributed unit.

Here, the information element of the warning request message includes PWS system information, and the plurality of indicators may be specified as the range of the PWS system information.

Meanwhile, in the communication system according to the third embodiment of the present disclosure for achieving the above object, the control plane operating device in the communication system is a distributed unit of the first base station and includes a processor, and the processor is the first base station. The distributed unit of a first base station receives a terminal context setup message including DAPS handover indication information from the central unit of the first base station that has received a request for preparation of a dual active protocol stack (DAPS) handover from a second base station; And, based on the DAPS handover indication information, the information required for DAPS handover may be generated and transmitted to the central unit through a terminal context setup response message.

Here, the DAPS handover indication information consists of DAPS handover setting information at the DRB (data radio bearer) level, and the DAPS handover setting information at the DRB level includes each DRB ID (identifier) information of a plurality of DRBs and the It may be composed of each DRB information including DAPS bearer information indicating whether or not the DAPS handover is applied to each DRB ID.

Here, when information necessary for DAPS handover is generated based on the DAPS handover indication information and transmitted to the central unit through a terminal context setup response message, the processor is configured to allow the distribution unit of the first base station to generate the DAPS handover. Generating the information necessary for the DAPS handover according to over indication information; And may operate to cause transmission of the terminal context setup response message containing the information necessary for the DAPS handover to the central unit through the F1AP interface.

According to the present disclosure, the central unit of the target base station receives a handover preparation request message requesting preparation for a handover applying DAPS (dual active protocol stack) technology from the source base station, and then sends a handover preparation request message to the distributed unit of the target base station applying DAPS technology. You can request terminal context setup for override.

Accordingly, according to the present disclosure, the distributed unit of the target base station can provide a terminal context setup response message to the central unit of the target base station after executing setup of the terminal context required for handover using DAPS technology.

Additionally, according to the present disclosure, in a public warning system, a central unit of a base station can transmit system information related to earthquake and tsunami warnings to distributed units of the base station using a single message. Accordingly, according to the present disclosure, the distributed unit of the base station can receive system information related to earthquake and tsunami warnings through a single message from the central unit of the base station and quickly broadcast a system message containing the related information to the terminals. can do.

1 is a conceptual diagram showing a first embodiment of a communication system.
Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
Figure 3 is a flowchart showing a first embodiment of a handover method in a communication system.
Figure 4 is a flowchart showing a second embodiment of a handover method in a communication system.
Figure 5 is a flowchart showing a first embodiment of a handover method using dual active protocol stack technology in a communication system.
Figure 6 is a flowchart showing a second embodiment of a handover method using dual protocol stack technology in a communication system.
FIG. 7 is a flowchart illustrating a first embodiment of the handover preparation procedure of FIG. 6.
Figure 8 is a flowchart showing a first embodiment of a public warning method in a communication system.
Figure 9 is a flowchart showing a second embodiment of a public warning method in a communication system.

Since the present disclosure can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present disclosure.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be referred to as a second component, and similarly, the second component may be referred to as a first component without departing from the scope of the present disclosure. The term and/or includes any of a plurality of related stated items or a combination of a plurality of related stated items.

In embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Additionally, in embodiments of the present disclosure, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B.”

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The terms used in this disclosure are only used to describe specific embodiments and are not intended to limit the disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present disclosure, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted in an idealized or overly formal sense unless explicitly defined in the present disclosure. No.

Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate overall understanding in explaining the present disclosure, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

1 is a conceptual diagram showing a first embodiment of a communication system.

Referring to FIG. 1, the communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Here, the communication system may be referred to as a “communication network”. Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may use a communication protocol based on code division multiple access (CDMA), a communication protocol based on wideband CDMA (WCDMA), a communication protocol based on time division multiple access (TDMA), and a frequency division multiple access (FDMA)-based communication protocol. access)-based communication protocol, OFDM (orthogonal frequency division multiplexing)-based communication protocol, OFDMA (orthogonal frequency division multiple access)-based communication protocol, SC (single carrier)-FDMA-based communication protocol, NOMA (non-orthogonal multiple access) access)-based communication protocols, SDMA (space division multiple access)-based communication protocols, etc. Each of the plurality of communication nodes may have the following structure.

Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transmitting and receiving device 230 that is connected to a network and performs communication. Additionally, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the communication node 200 is connected by a bus 270 and can communicate with each other. However, each component included in the communication node 200 may be connected through an individual interface or individual bus centered on the processor 210, rather than the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transmission/reception device 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present disclosure are performed. Each of the memory 220 and the storage device 260 may be comprised of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be comprised of at least one of read only memory (ROM) and random access memory (RAM).

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of user equipment (UEs). ) may include (130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third UE 130-3, and the fourth UE 130-4 may belong to the coverage of the first base station 110-1. The second UE 130-2, the fourth UE 130-4, and the fifth UE 130-5 may belong to the coverage of the second base station 110-2. The fifth base station 120-2, the fourth UE 130-4, the fifth UE 130-5, and the sixth UE 130-6 may belong within the coverage of the third base station 110-3. . The first UE (130-1) may belong to the coverage of the fourth base station (120-1). The sixth UE (130-6) may belong to the coverage of the fifth base station (120-2).

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes a NodeB, an evolved NodeB, a base transceiver station (BTS), Radio base station, radio transceiver, access point, access node, road side unit (RSU), digital unit (DU), cloud digital unit (CDU) , may be referred to as a radio remote head (RRH), radio unit (RU), transmission point (TP), transmission and reception point (TRP), relay node, etc. A plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) each include a terminal, an access terminal, a mobile terminal, It may be referred to as a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, etc.

A plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) Each may support cellular communication (e.g., long term evolution (LTE), advanced (LTE-A), etc. defined in the 3rd generation partnership project (3GPP) standard). Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in a different frequency band or may operate in the same frequency band. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be connected to each other through ideal backhaul or non-ideal backhaul, and ideal backhaul Alternatively, information can be exchanged with each other through non-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through ideal backhaul or non-ideal backhaul. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) transmits the signal received from the core network to the corresponding UE (130-1, 130-2, 130-3, 130). -4, 130-5, 130-6), and the signal received from the corresponding UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is sent to the core network can be transmitted to.

Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support OFDMA-based downlink transmission and SC-FDMA-based uplink ) can support transmission. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits multiple input multiple output (MIMO) (e.g., single user (SU)-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, carrier aggregation transmission, transmission in unlicensed band, device to device (D2D) ) may support communication (or ProSe (proximity services), etc. Here, each of the plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is connected to a base station Operations corresponding to (110-1, 110-2, 110-3, 120-1, 120-2), supported by base stations (110-1, 110-2, 110-3, 120-1, 120-2) The action can be performed.

Meanwhile, 3GPP can propose the concept of a functionally separated base station. Here, functional separation may be a method of physically separating and operating one base station. Accordingly, functional separation may refer to a technology that separates the protocol stack based on a certain standard from the existing method of mounting all protocol stacks on one node and operates by mounting some protocol stacks on two or more nodes. A functionally separated base station can be largely composed of a distribution unit (DU) and a central unit (CU).

Generally, the protocol stack mounted on a base station includes RF (radio frequency) function, PHY (physical) function, MAC (medium access control) function, RLC (radio link control) function, and PDCP (packet data convergence protocol) based on the 5G communication system. ) function, service data adaptation protocol (SDAP) function, radio resource control (RRC) function, NG application protocol (NGAP) function, XN application protocol (XNAP) function, X2 application protocol (X2AP) function, etc.

Here, the central unit (CU) is a logical node that can control the operations of one or more distributed units (DU) and performs the RRC function, PDCP function, SDAP function, NGAP function, XNAP function, and X2AP function. You can. A distributed unit (DU) may be a logical node that performs RF functions, PHY functions, MAC functions, and RLC functions.

Meanwhile, the central unit (CU) may include a central unit-control plane (CU-CP), which is a control plane node, and a user-plane (CU-UP), which is a user plane node. Here, CU-CP can perform control functions. CU-CP can be equipped with protocols such as RRC function, PDCP-C (control) function, NGAP function, XNAP function, and X2AP function. Additionally, CU-UP can perform the function of transmitting user data. CU-UP can be equipped with protocols such as PDCP-U function and SDAP function.

In 3GPP, the control plane interface between the distributed unit and the central unit can be defined as F1AP (F1 application protocol). Distributed units and central units can transmit and receive control messages such as RRC messages, NGAP messages, XNAP messages, and X2AP messages through the F1AP interface. Such a functionally separated base station may require modification to the radio bearer to apply dual active protocol stack (DAPS), public warning system (PWS), etc.

Figure 3 is a flowchart showing a first embodiment of a handover method in a communication system.

Referring to FIG. 3, in the handover method, the source base station can perform measurement configuration so that the terminal can perform measurements on neighboring base stations, including the target base station. Next, the terminal can measure the signal strength of surrounding base stations including the source/target base station (S300), and if the measurement result satisfies a predetermined condition, a measurement report including the measurement result to the source base station (measurement report) report) message can be transmitted (S301). At this time, the reported measurement results may include signal measurement results from surrounding base stations.

The source base station may receive a measurement report message from the terminal. Accordingly, the source base station can determine handover to the target base station based on the received measurement results. Additionally, the source base station may instruct the target base station to prepare for handover by transmitting a handover preparation request message to the target base station (S302). At this time, the source base station may include the measurement result for the target base station received from the terminal in a handover preparation request message and transmit it to the target base station.

Meanwhile, the target base station can decide whether to accept the handover of the terminal through admission control (S303), and if it is determined to accept the handover of the terminal, handover preparation approval to the source base station (handover A preparation acknowledgment message can be transmitted (S304). Accordingly, the source base station can receive a handover preparation approval message from the target base station.

Additionally, the source base station may transmit a PDCP sequence number (SN) for normal data transmission and reception at the target base station (S305). Then, the target base station can receive the PDCP SN from the source base station. Meanwhile, the source base station may transmit a handover command message to the terminal (S306). Then, the terminal can receive a handover command message from the source base station.

The terminal that receives the handover command message can immediately perform handover. Accordingly, the terminal can obtain downlink synchronization with the target base station, disconnect from the source base station, and attempt to connect to the target base station. Meanwhile, the source base station can forward data to be transmitted to the terminal to the target base station. When the access procedure for the target base station is completed, the terminal may transmit a handover complete message to the target base station (S307). The target base station that receives the handover completion message from the terminal can initiate data transmission to the terminal.

Meanwhile, in this handover method, the entity in charge of the PDCP function of the source base station may no longer transmit downlink data after delivering the PDCP SN to the target base station. The target base station can receive a handover completion message from the terminal and transmit downlink data to the terminal accordingly. As a result, the terminal can receive data from the target base station after transmitting the handover completion message. In this way, the terminal cannot receive downlink data from the time the source base station transfers the PDCP SN to the target base station until the handover is completed.

Figure 4 is a flowchart showing a second embodiment of a handover method in a communication system.

Referring to FIG. 4, in the handover method, the source base station can perform measurement settings so that the terminal can perform measurements on neighboring base stations including the target base station. Next, the terminal can measure the signal strength of surrounding base stations, including the source/target base station, and if the measurement result satisfies a predetermined condition, it can transmit a measurement report message containing the measurement result to the source base station. . At this time, the reported measurement results may include signal measurement results from surrounding base stations.

The source base station may receive a measurement report message from the terminal. Accordingly, the source base station can determine handover to the target base station based on the received measurement results (S400). In addition, the source base station may proceed with a handover preparation procedure with the central unit of the target base station and the distributed unit of the target base station (S401). That is, the source base station may transmit a handover preparation request message to the central unit (CU) of the target base station and instruct the central unit of the target base station to prepare for handover.

At this time, the source base station may include the measurement result for the target base station received from the terminal in a handover preparation request message and transmit it to the central unit of the target base station. Then, the central unit of the target base station can request the creation of a terminal context from the distributed unit of the target base station. Accordingly, the distributed unit of the target base station can receive a terminal context creation request from the central unit of the target base station and create a terminal context accordingly. In addition, the distributed unit of the target base station may respond to the central unit of the target base station that the terminal context has been successfully created including radio resource settings to be used by the terminal.

Meanwhile, when the central unit of the target base station determines to accept the handover of the terminal through this process, it can transmit a handover preparation approval message to the source base station. Accordingly, the source base station can receive a handover preparation approval message from the central unit of the target base station.

In addition, the source base station may transmit the PDCP SN for normal data transmission and reception in the central unit (CU) of the target base station (S402). Then, the central unit of the target base station can receive the PDCP SN from the source base station. Meanwhile, the source base station may transmit a handover command message to the terminal (S403). Then, the terminal can receive a handover command message from the source base station.

The terminal that receives the handover command message can immediately perform handover. Accordingly, the terminal can obtain downlink synchronization with the target base station, disconnect from the source base station, and attempt to connect to the target base station. Meanwhile, the source base station may transmit data to be transmitted to the terminal to the central unit of the target base station. When the access procedure for the target base station is completed, the terminal may transmit a handover completion message to the central unit of the target base station (S404). The central unit of the target base station that receives the handover completion message from the terminal may initiate data transmission to the terminal.

Meanwhile, in this handover method, the entity in charge of the PDCP function of the source base station may no longer transmit downlink data after delivering the PDCP SN to the central unit of the target base station. The central unit of the target base station can receive a handover completion message from the terminal and transmit downlink data to the terminal accordingly. As a result, the terminal can receive data from the central unit of the target base station after transmitting the handover completion message. In this way, the terminal cannot receive downlink data from the time the source base station transfers the PDCP SN to the central unit of the target base station until the handover is completed.

Meanwhile, the dual active protocol stack (DAPS) technology may be a method of preventing data reception interruption time by temporarily transmitting and receiving data simultaneously between the source base station and the target base station during the handover process.

Figure 5 is a flowchart showing a first embodiment of a handover method using dual active protocol stack technology in a communication system.

Referring to FIG. 5, in the handover method, the source base station can perform measurement settings so that the terminal can perform measurements on neighboring base stations including the target base station. Next, the terminal can measure the signal strength of surrounding base stations, including the source/target base station, and if the measurement result satisfies a predetermined condition, it can transmit a measurement report message containing the measurement result to the source base station. . At this time, the reported measurement results may include signal measurement results from surrounding base stations.

The source base station may receive a measurement report message from the terminal. Accordingly, the source base station can determine handover to the target base station based on the received measurement results (S500). Then, the source base station and the target base station can proceed with a handover preparation procedure (S501). That is, the source base station can instruct the target base station to prepare for handover by transmitting a handover preparation request message to the target base station. At this time, the source base station may include the measurement result for the target base station received from the terminal in a handover preparation request message and transmit it to the target base station. Additionally, the source base station may transmit DAPS handover indication information requesting preparation for a handover using dual active protocol stack technology to the target base station by including it in a handover preparation request message. Accordingly, the target base station can receive a handover preparation request message including measurement results and DAPS handover indication information from the source base station. Here, the DAPS handover indication information may consist of DAPS handover setting information at the DRB level that indicates whether to apply DAPS technology to each DRB (data radio bearer).

Meanwhile, the target base station can decide whether to accept the request for a handover using the DAPS technology of the source base station through acceptance control, and if it is decided to accept the handover using the DAPS technology of the source base station, the target base station can determine whether to accept the handover request using the DAPS technology of the source base station. An over-ready acknowledgment message can be transmitted. Accordingly, the source base station can receive a handover preparation approval message from the target base station.

In addition, the source base station may transmit the PDCP early SN for normal early data transmission and reception at the target base station (S502). Then, the target base station can receive the PDCP early SN from the source base station. At this time, the source base station can transmit downlink data to the terminal. Additionally, the source base station can transmit downlink data to the target base station. Accordingly, the target base station can also transmit downlink data to the terminal.

In this handover method using dual protocol stack technology, the entity in charge of the PDCP function of the source base station can continue to transmit downlink data to the terminal after delivering the PDCP early SN to the target base station. The target base station can also transmit downlink data to the terminal. Through this method, the terminal can receive data without interruption until it connects to the target base station.

Meanwhile, the source base station may transmit a handover command message to the terminal (S503). Then, the terminal can receive a handover command message from the source base station. The terminal that receives the handover command message can immediately perform handover. Accordingly, the terminal can obtain downlink synchronization with the target base station, disconnect from the source base station, and attempt to connect to the target base station. When the access procedure for the target base station is completed, the terminal may transmit a handover completion message to the target base station (S504). The target base station that receives the handover completion message from the terminal may transmit the handover success message to the source base station (S505). The source base station may transmit the PDCP SN for normal data transmission and reception at the target base station (S506). Then, the target base station can receive the PDCP SN from the source base station. At this time, the source base station can transmit downlink data to the target base station. Accordingly, the target base station can transmit downlink data to the terminal. And, the PDCP entity of the source base station can stop downlink transmission to the terminal.

Meanwhile, in the handover method where dual protocol stack technology is applied, the source base station provides DAPS handover setting information at the DRB level that informs whether or not dual protocol stack technology is applied to each DRB at the DRB level, not the terminal level, in the handover preparation procedure. can be transmitted to the target base station. The target base station that receives this can proceed with internal procedures depending on whether it accepts it or not. At this time, the target base station can configure the wireless section for the newly connected terminal depending on whether or not each DRB has a dual protocol stack configured.

Figure 6 is a flowchart showing a second embodiment of a handover method using dual protocol stack technology in a communication system.

Referring to FIG. 6, in the handover method, the source base station can perform measurement settings so that the terminal can perform measurements on neighboring base stations, including the target base station. Next, the terminal can measure the signal strength of surrounding base stations, including the source/target base station, and if the measurement result satisfies a predetermined condition, it can transmit a measurement report message containing the measurement result to the source base station. . At this time, the reported measurement results may include signal measurement results from surrounding base stations.

The source base station may receive a measurement report message from the terminal. Accordingly, the source base station can determine handover to the target base station based on the received measurement results (S600). Additionally, the source base station may proceed with a handover preparation procedure with the central unit of the target base station and the distributed unit of the target base station (S601). That is, the source base station may transmit a handover preparation request message to the central unit (CU) of the target base station and instruct the central unit of the target base station to prepare for handover.

At this time, the source base station may include the measurement result for the target base station received from the terminal in a handover preparation request message and transmit it to the central unit of the target base station. Additionally, the source base station may include DAPS handover indication information requesting the target base station to prepare for a handover using dual active protocol stack technology in a handover preparation request message and transmit it to the central unit of the target base station. Accordingly, the central unit of the target base station can receive a handover preparation request message including measurement results and DAPS handover indication information from the source base station. Here, the DAPS handover indication information may consist of DAPS handover setting information at the DRB level that indicates whether to apply DAPS technology to each DRB.

Then, the central unit of the target base station can request the creation of a terminal context from the distributed unit of the target base station. At this time, the central unit of the target base station may transmit DAPS handover indication information to the distribution unit of the target base station, informing the distribution unit of the target base station that a handover using dual active protocol stack technology will be performed.

Accordingly, the distributed unit of the target base station can receive a terminal context creation request from the central unit of the target base station and create a terminal context accordingly. Additionally, the central unit of the target base station can receive DAPS handover indication information from the distribution unit of the target base station, and can generate parameters that the distribution unit of the target base station is responsible for in handover to which DAPS technology is applied. In addition, the distributed unit of the target base station may respond to the central unit of the target base station that the terminal context has been successfully created including radio resource settings to be used by the terminal. At this time, the distributed unit of the target base station may transmit the generated parameters to the central unit of the target base station.

Then, the central unit of the target base station may receive the success of creating a terminal context including radio resource settings to be used by the terminal as a distributed unit of the target base station. At this time, the central unit of the target base station may receive parameters generated from the distributed unit of the target base station.

Meanwhile, if the central unit of the target base station decides to accept the handover of the terminal through this process, it can generate parameters that the central unit of the target base station is responsible for in the handover to which DAPS technology is applied. In addition, the central unit of the target base station may transmit a handover preparation approval message including parameters generated by the central unit of the target base station, parameters generated by the distributed unit of the target base station, and radio resource settings to be used by the terminal to the source base station. there is. Accordingly, the source base station can receive a handover preparation approval message from the central unit of the target base station. In addition, the source base station can determine the parameters generated by the central unit of the target base station, the parameters generated by the distributed unit of the target base station, and the radio resource settings to be used by the terminal from the handover preparation approval message.

And, the source base station may transmit the PDCP early SN for normal early data transmission and reception in the central unit (CU) of the target base station (S602). Then, the central unit of the target base station can receive the PDCP early SN from the source base station. At this time, the source base station can transmit downlink data to the terminal. Additionally, the source base station can transmit downlink data to the central unit of the target base station. Accordingly, the central unit of the target base station can also transmit downlink data to the terminal.

In this handover method using dual protocol stack technology, the entity in charge of the PDCP function of the source base station can continue to transmit downlink data to the terminal after delivering the PDCP early SN to the central unit of the target base station. The central unit of the target base station can also transmit downlink data to the terminal. Through this method, the terminal can receive data without interruption until it connects to the target base station.

Meanwhile, the source base station may transmit a handover command message to the terminal (S603). Then, the terminal can receive a handover command message from the source base station. The terminal that receives the handover command message can immediately perform handover. Accordingly, the terminal can obtain downlink synchronization with the target base station, disconnect from the source base station, and attempt to connect to the target base station. Meanwhile, the source base station may transmit data to be transmitted to the terminal to the central unit of the target base station. When the access procedure for the target base station is completed, the terminal may transmit a handover completion message to the central unit of the target base station (S604).

The central unit of the target base station that receives the handover completion message from the terminal may transmit the handover success message to the source base station (S605). The source base station may transmit the PDCP SN for normal data transmission and reception in the central unit of the target base station (S606). Then, the central unit of the target base station can receive the PDCP SN from the source base station. At this time, the source base station can transmit downlink data to the central unit of the target base station. Accordingly, the central unit of the target base station can transmit downlink data to the terminal. And, the PDCP entity of the source base station can stop downlink transmission to the terminal.

FIG. 7 is a flowchart illustrating a first embodiment of the handover preparation procedure of FIG. 6.

Referring to FIG. 7, in the handover preparation procedure, the source base station may transmit a handover preparation request message to the central unit (CU) of the target base station to instruct the central unit of the target base station to prepare for handover (S700).

At this time, the source base station may include the measurement result for the target base station received from the terminal in a handover preparation request message and transmit it to the central unit of the target base station. Additionally, the source base station may include DAPS handover indication information requesting the target base station to prepare for a handover using dual active protocol stack technology in a handover preparation request message and transmit it to the central unit of the target base station.

Accordingly, the central unit of the target base station can receive a handover preparation request message including measurement results and DAPS handover indication information from the source base station. Here, the DAPS handover indication information may consist of DAPS handover setting information at the DRB level that indicates whether to apply DAPS technology to each DRB.

Then, the central unit of the target base station can allocate DRBs according to the handover preparation request message received from the source base station. And, the central unit of the target base station may transmit a terminal context setup request message containing information about the allocated DRBs to the distribution unit of the target base station through the F1AP interface (S701). At this time, the central unit of the target base station may transmit a terminal context setup request message including DAPS handover indication information consisting of DAPS handover setting information at the DRB level to the distributed unit of the target base station.

Here, referring to Table 1, the DAPS handover setting information at the DRB level includes each DRB ID (identifier) information element (IE) of a plurality of DRBs and whether or not DAPS handover is applied to each DRB ID. It may be composed of each DRB information including the DAPS bearer information element that is notified. Here, the DAPS bearer information element can be optionally included when handover using DAPS technology is performed by setting presence to option (i.e., O).

Accordingly, the distributed unit of the target base station may receive a terminal context setup request message including DRB information from the central unit of the target base station. The distribution unit of the target base station can create a terminal context according to the received DRB information and allocate radio resources to service the corresponding terminal. At this time, the distribution unit of the target base station can generate parameters necessary to perform handover using DAPS technology. In addition, the distribution unit of the target base station sends a terminal context setup response message to the central unit of the target base station indicating the success of terminal context creation, including the radio resource settings allocated for use by the terminal and the parameters necessary to perform handover using DAPS technology. It can be transmitted (S702). Then, the central unit of the target base station successfully creates a terminal context including the radio resource settings allocated for use by the terminal from the distributed unit of the target base station and the parameters necessary to perform handover using DAPS technology. A terminal context setup response message notifying may be received. Accordingly, the central unit of the target base station can generate additional parameters necessary to perform handover using DAPS technology.

Meanwhile, if the central unit of the target base station determines to accept the handover of the terminal through this process, it may transmit a handover preparation approval message to the source base station (S703). Accordingly, the source base station can receive a handover preparation approval message from the central unit of the target base station. Here, the handover preparation approval message includes radio resource configuration information to be used by the terminal, information on parameters necessary to perform a handover using DAPS technology generated by the distributed unit of the target base station, and DAPS generated by the central unit of the target base station. It may include information on parameters necessary to perform handover using technology. Table 2 below shows the parameters required to perform handover. Referring to Table 2, the parameters required for a general handover may be different from those required for a handover using DAPS technology. Additionally, referring to Table 2, the parameters generated by the central unit of the target base station may be different from the parameters generated by the distributed unit of the target base station. In particular, the central unit and distributed unit of the target base station may recognize parameters that are necessary for general handover but not necessary for DAPS handover, and may not generate the corresponding parameters when generating parameters required for handover.

Meanwhile, public warning systems (PWS) can be used to provide timely and accurate alerts, warnings and information regarding disasters and other emergencies. These PWS systems may include commercial mobile alert systems (CMAS) and earthquake and tsunami warning systems (ETWS). ETWS can notify the terminal that an earthquake or tsunami disaster is imminent, or rescue information (for example, notification of the location of an evacuation site) after an earthquake or tsunami disaster. CMAS can provide public safety warning services (eg, forest fires, terrorist attacks, etc.) to users of the terminal.

Figure 8 is a flowchart showing a first embodiment of a public warning method in a communication system.

Referring to FIG. 8, in the public warning method, a cell broadcast entity (CBE) may transmit emergency information including a warning message and warning area information to a cell broadcast center (CBC). Here, the warning message may include a multimedia object related to the location, text message, warning parameters, or additional information about the warning (photo, audio, video). At this time, the warning parameter may be a parameter indicating severity or urgency. Types of these warning messages may be ETWS messages or CMAS messages.

The cell broadcast center can use the warning area information to identify which access mobility function (AMF) entities need to be contacted and determine what information to place in the warning area information element. The cell broadcast center may transmit a write-replace alert request signal containing an alert message and alert area information to the AMF entity. Accordingly, the AMF entity can receive a write replacement warning request signal including a warning message and warning area information from the cell broadcast center. The AMF entity may transmit a write replacement warning request signal including a warning message and warning area information to the base station (S800). The base station may receive a write-replace warning request signal from the AMF entity including a warning message and warning area information.

The base station can broadcast a warning message by using warning area information to determine the cell(s) in which the warning message will be broadcast. At this time, the base station can identify the type of warning message and, if the identified type of warning message is an ETWS message, transmit the main part of the ETWS warning information to the terminal through system information block type SIB 6 (system information block type 6), and SIB The auxiliary part of the ETWS alert information can be transmitted to the terminal through 7 (system information block type 7) (S801). Additionally, if the type of warning message identified is a CMAS message, the base station can transmit CMAS warning information to the terminal through SIB 8 (system information block type 8) (S802). Accordingly, the terminal can receive a warning message broadcast from the base station and display the received warning message to the user. Meanwhile, the base station may transmit a write replacement warning response message to the AMF entity (S803). The AMF entity may receive a write replacement warning response message from the base station.

Figure 9 is a flowchart showing a second embodiment of a public warning method in a communication system.

Referring to FIG. 9, in the public warning method, a cell broadcast entity (CBE) may transmit information including a warning message and warning area information to a cell broadcast center (CBC). Here, the warning message may include a multimedia object related to the location, text message, warning parameters, or additional information about the warning (photo, audio, video). At this time, the warning parameter may be a parameter indicating severity or urgency. These warning messages may include ETWS warning information or CMAS warning information. Here, the ETWS warning information may include a main part (for example, an earthquake warning message, etc.) and an auxiliary part (for example, earthquake epicenter information, etc.).

The cell broadcast center can use the alert area information to identify which AMF entities need to be contacted and determine what information to place in the alert area information element. The cell broadcast center may transmit a write replacement warning request signal including a warning message and warning area information to the central unit of the base station through the AMF entity (S900). The central unit of the base station may receive a write replacement warning request message including a warning message and warning area information through the AMF entity in the cell broadcast center. The central unit of the base station may use the warning area information to determine the cell(s) in which the warning message will be broadcast and transmit the warning request message to the distributed unit of the base station responsible for the corresponding cell. At this time, when the distribution unit of the base station determines the contents of the warning message and includes ETWS warning information, it includes the main part of the ETWS warning information in the write replacement warning request message through the system information block type SIB 6 and transmits it to the distribution unit of the base station. It can be transmitted, and the auxiliary part of the ETWS warning information can be included in the write replacement warning request message through SIB 7 and transmitted to the distribution unit of the base station (S901). In addition, the central unit of the base station can identify the contents of the warning message and, if it includes CMAS warning information, include SIB 8 in the write replacement warning request message and transmit it to the distributed unit of the base station (S902). The distributed unit of the base station may generate and broadcast a system information message including warning information received from the central unit of the base station (S903). Accordingly, the terminal can receive a system information message broadcast from the distribution unit of the base station, and display warning content in the received system information message to the user.

Meanwhile, the distributed unit of the base station may inform the central unit of the base station whether to broadcast the system information message by transmitting a write replacement warning response message (S904). Then, the central unit of the base station may receive a write replacement warning response message from the distributed units of the base station. Next, the central unit of the base station may inform the AMF entity whether to broadcast the system information message by transmitting a write replacement warning response message (S905). Then, the central unit of the base station may receive a write replacement warning response message from the distributed units of the base station.

In this way, in the case of an ETWS alarm, the system information blocks required may be of two types: SIB 6 and SIB 7. However, the write instead warning request message defined in the current F1AP standard may be defined to include only one SIB. Accordingly, when the central unit of the base station transmits a single ETWS message containing both SIB 6 and SIB 7 to the distributed unit of the base station, inefficiency may occur in that the write replacement warning request message is used and transmitted twice. The present disclosure may present a method in which one write replacement warning request message can set a plurality of different SIBs. Table 3 shows the information elements of the write replacement warning request message. Referring to Table 3, the information elements of the write replacement warning request message include message type, transaction identifier, PWS system information, repetition period, and number of broadcast requests ( It may include number of broadcasts requested, etc. Here, the repetition period may indicate the repetition period (in seconds) of the message to be broadcast, and the number of broadcast requests may indicate the number of times the message will be broadcast. As can be seen, the SIB information included in the write replacement warning request message may be defined as PWS system information.

Table 4 may indicate improved PWS system information among the information elements included in the write replacement warning request message. As can be seen in Table 4, the improved PWS system information may be mandatory in presence (i.e., mandatory, M) and may have multiple indicators in range (e.g., 1. <maxSIBNum>). Here, the plurality indicator may indicate that it contains a plurality of SIBs. In this way, if the write replacement warning request message includes multiple indicators, the distribution unit that received it can detect multiple SIBs and obtain necessary information.

The operation of the method according to the embodiment of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. Computer-readable recording media include all types of recording devices that store information that can be read by a computer system. Additionally, computer-readable recording media can be distributed across networked computer systems so that computer-readable programs or codes can be stored and executed in a distributed manner.

Additionally, computer-readable recording media may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Program instructions may include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc.

Although some aspects of the disclosure have been described in the context of an apparatus, it may also refer to a corresponding method description, where a block or device corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method may also be represented by corresponding blocks or items or features of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as a microprocessor, programmable computer, or electronic circuit, for example. In some embodiments, at least one or more of the most important method steps may be performed by such an apparatus.

In embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to perform some or all of the functionality of the methods described herein. In embodiments, a field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

Although the present disclosure has been described above with reference to preferred embodiments, those skilled in the art may modify and change the present disclosure in various ways without departing from the spirit and scope of the present disclosure as set forth in the claims below. You will understand that it is possible.

Claims (15)

A method of operating a central unit of a first base station in a communication system, comprising:
Receiving a handover preparation request message requesting preparation for a dual active protocol stack (DAPS) handover from a second base station;
Transmitting a terminal context setup message including DAPS handover indication information to the distribution unit of the first base station;
Receiving a terminal context setup response message including primary DAPS handover parameter information required for the DAPS handover generated based on the DAPS handover indication information from the distribution unit;
Generating information necessary for the DAPS handover based on the first DAPS handover parameter information; and
A method of operating a central unit of a first base station, comprising transmitting a handover preparation request response message containing the information necessary for the DAPS handover to the second base station. In claim 1,
The DAPS handover indication information is composed of DAPS handover setting information at the DRB (data radio bearer) level. A method of operating a central unit of a first base station. In claim 2,
The DAPS handover configuration information at the DRB level includes each DRB ID (identifier) information of a plurality of DRBs and each DRB information including DAPS bearer information indicating whether or not to apply the DAPS handover to each DRB ID. A method of operating a central unit of a first base station, consisting of: In claim 1,
The step of transmitting a terminal context setup message including DAPS handover indication information to the distribution unit of the first base station,
Generating the DAPS handover indication information including DAPS handover configuration information at the DRB level; and
A method of operating a central unit of a first base station, comprising transmitting the terminal context setup message including the DAPS handover indication information to the distribution unit through an F1 application protocol (F1AP) interface. In claim 1,
The step of generating information necessary for the DAPS handover based on the first DAPS handover parameter information,
Generating secondary DAPS handover parameter information required for the DAPS handover based on the primary DAPS handover parameter information; and
A method of operating a central unit of a first base station, comprising generating the information necessary for the DAPS handover consisting of the first DAPS handover parameter information and the second DAPS handover parameter information. In claim 1,
Receiving a PDCP early sequence number (SN) from the second base station for early data transmission and reception;
Receiving data from the second base station; and
A method of operating a central unit of a first base station, further comprising transmitting the data to a terminal based on the PDCP early SN. A method of operation of a central unit of a base station in a communication system, comprising:
Receiving an alert message from a cell broadcast center; and
Generating system information according to the type of the warning message and transmitting a warning request message including the system information to a distribution unit of the base station,
When the system information consists of a plurality of SIBs (system information blocks), the operating method of the central unit of the base station transmits the plurality of SIBs to the distributed unit using the warning request message. In claim 7,
The step of generating system information according to the type of the warning message and transmitting it to the distribution unit of the base station using a warning request message,
Determining the message type of the warning message;
If the message type is a CMAS warning message including CMAS (commercial mobile alert system) warning content, generating SIB 8 including the CMAS warning content; and
A method of operating a central unit of a base station, comprising transmitting the warning request message including the SIB 8 to the distributed unit. In claim 7,
The step of generating system information according to the type of the warning message and transmitting it to the distribution unit of the base station using a warning request message,
Determining the message type of the warning message;
If the message type is an ETWS (earthquake and tsunami warning system) warning message that includes the main and auxiliary parts of an ETWS (earthquake and tsunami warning system) warning, generating SIB 6 including the main part and generating SIB 7 including the auxiliary part. ; and
A method of operating a central unit of a base station, comprising transmitting the warning request message including the SIB 6 and the SIB 7 to the distributed unit. In claim 7,
The warning request message is transmitted from the central unit to the distributed unit using an F1AP interface. In claim 7,
When the system information consists of the plurality of SIBs, the central unit transmits the warning request message including a plurality of indicators indicating the plurality of SIBs to the distribution unit. In claim 11,
The information element of the warning request message includes PWS system information, and the plurality of indicators is specified as a range of the PWS system information. As a distributed unit of the first base station,
Includes a processor,
The processor is the distributed unit of the first base station,
Receive a terminal context setup message including DAPS handover indication information from a central unit of the first base station that has received a request for preparation of a dual active protocol stack (DAPS) handover from a second base station; and
A distribution unit of a first base station, operative to generate information necessary for DAPS handover based on the DAPS handover indication information and transmit it to the central unit through a terminal context setup response message. In claim 13,
The DAPS handover indication information consists of DAPS handover setting information at the DRB (data radio bearer) level,
The DAPS handover configuration information at the DRB level includes each DRB ID (identifier) information of a plurality of DRBs and each DRB information including DAPS bearer information indicating whether or not to apply the DAPS handover to each DRB ID. Consisting of a distributed unit of the first base station. In claim 13,
When information required for DAPS handover is generated based on the DAPS handover indication information and transmitted to the central unit through a terminal context setup response message, the processor is configured to:
Generating the information necessary for the DAPS handover according to the DAPS handover indication information; and
The distributed unit of the first base station operative to cause transmission of the terminal context setup response message containing the information necessary for the DAPS handover to the central unit via a F1AP interface.

Images