KR20230021493A - Method and apparatus for performing conditional handover - Google Patents

Abstract

The disclosure relates to a communication technique and system which integrates a 5G communication system with IoT technology to support higher data transmission rates after the 4G system. The disclosure can be applied to intelligent services (e.g. smart home, smart building, smart city, smart or connected car, healthcare, digital education, retail, security and safety-related services, etc.) based on 5G communication technology and IoT-related technology. According to various embodiments proposed in the disclosure, in a conditional handover modification procedure, a method to prevent handover command messages including the same information from being delivered from the source base station to the terminal is provided. Accordingly, problems such as unnecessary waste of radio resources can be solved, and more efficient conditional handover can be supported. The present invention relates to a control signal processing method, comprising: a step of receiving a first control signal transmitted from a base station; a step of processing the received a first control signal; and a step of transmitting a second control signal generated based on the processing to the base station.

Description

Method and apparatus for performing conditional handover in communication system

This disclosure relates to the operation of a base station in a communication system. More specifically, the present disclosure relates to operation of a base station for conditional handover in a communication system.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system to meet the growing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or pre-5G communication system is being called a system after the 4G network (Beyond 4G Network) communication system or LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in a mmWave band (eg, a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used in 5G communication systems. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), and an ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation etc. are being developed. In addition, in the 5G system, advanced coding modulation (Advanced Coding Modulation: ACM) methods FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), advanced access technologies FBMC (Filter Bank Multi Carrier), NOMA (non orthogonal multiple access) and SCMA (sparse code multiple access) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network in which humans create and consume information to an Internet of Things (IoT) network in which information is exchanged and processed between distributed components such as things. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection with cloud servers, etc., is also emerging. In order to implement IoT, technical elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, sensor networks for connection between objects and machine to machine , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new values in human life by collecting and analyzing data generated from connected objects can be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliances, advanced medical service, etc. can be applied to

Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, technologies such as sensor network, machine to machine (M2M), and machine type communication (MTC) are implemented by techniques such as beamforming, MIMO, and array antenna, and 5G communication technologies There is. The application of the cloud radio access network (cloud RAN) as the big data processing technology described above can be said to be an example of convergence of 5G technology and IoT technology.

As various services can be provided according to the development of the mobile communication system as described above, a method for effectively providing these services is required.

On the other hand, in a next-generation mobile communication system such as a 5G communication system, conditional A conditional handover (CHO) has been proposed. Conditional handover may refer to handover performed by the terminal when one or more handover execution conditions are satisfied. Recently, the need for a solution to problems such as waste of radio resources and signaling overhead, which may occur in procedures related to conditional handover, has emerged.

In the above-described conditional handover, the terminal receiving configuration information for the conditional handover evaluates whether one or more handover execution conditions are satisfied, and if the handover execution conditions are satisfied, the handover execution conditions are satisfied. It may consist of a procedure for performing handover by synchronizing with a candidate cell (or target base station, target gNB) corresponding to .

Configuration information used in the conditional handover procedure is configuration information for conditional handover candidate cell(s), which can be changed through a conditional handover modification (CHO modification) procedure.

Meanwhile, in the conditional handover change procedure, a handover command message (eg, handover command message) included in a handover request acknowledgment message (eg, handover request acknowledge message) received by the source base station from the target base station is It is transparent to the base station. In other words, the source base station transmits the handover command message to the terminal as it is without performing a separate confirmation operation. If the configuration information for conditional handover is not changed (for example, if the target base station includes the same configuration information as the previously transmitted configuration information for conditional handover in the handover command message), the same information The containing message may be redundantly delivered from the source base station to the terminal. This may cause problems such as waste of radio resources and unnecessary increase in signaling overhead. Therefore, it is necessary to devise a method to solve the above problems in order to support more efficient conditional handover.

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

In order to solve the above problems, according to an embodiment of the present disclosure, a method for processing a control signal in a communication system is provided. The control signal processing method may include receiving a first control signal transmitted from a base station; processing the received first control signal; and transmitting a second control signal generated based on the processing to the base station.

According to various embodiments proposed in the present disclosure, a method for preventing a handover command message including identical information from being repeatedly transmitted from a source base station to a terminal in a conditional handover change procedure is provided. Accordingly, problems such as waste of unnecessary radio resources can be solved, and more efficient conditional handover can be supported.

The above and other objects, features and advantages of the present disclosure will become clearer through the following description of embodiments of the present disclosure with reference to the accompanying drawings.
1 is a diagram illustrating an example of a structure of a next-generation mobile communication system to which the present disclosure can be applied.
2 is a diagram illustrating a radio protocol structure of a next-generation mobile communication system to which the present disclosure can be applied.
FIG. 3 is a handover preparation procedure performed by a source base station and a potential target base station to support conditional handover according to an embodiment of the present disclosure and a pre-set conditional condition between the source base station and the potential target base station. A diagram illustrating a conditional handover change procedure for changing handover-related settings (eg, CHO configuration).
4 is a diagram of a terminal, a source base station, and a target according to embodiments proposed in the present disclosure in order to solve a problem caused by duplicate handover command messages including the same information being transmitted to the terminal in a conditional handover change procedure. It is a diagram showing the overall operation of the base station.
5 is a diagram illustrating an operation of a target base station according to the first embodiment of the present disclosure.
6 is a diagram illustrating an operation of a source base station according to a first embodiment of the present disclosure.
7 is a diagram illustrating a message and an information element (IE) according to the first embodiment of the present disclosure.
8 is a diagram illustrating an operation of a target base station according to a second embodiment of the present disclosure.
9 is a diagram illustrating an operation of a source base station according to a second embodiment of the present disclosure.
10 is a diagram illustrating a message and an IE according to the second embodiment of the present disclosure.
11 is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.
12 is a diagram showing the structure of a base station according to an embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

In describing the embodiments, descriptions of technical contents that are well known in the technical field to which the present disclosure belongs and are not directly related to the present disclosure will be omitted. This is to more clearly convey the gist of the present disclosure without obscuring it by omitting unnecessary description.

For the same reason, in the accompanying drawings, some components are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. In each figure, the same reference number is assigned to the same or corresponding component.

Advantages and features of the present disclosure, and methods of achieving them, will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms, only the present embodiments make the present disclosure complete, and those of ordinary skill in the art to which the present disclosure belongs It is provided to fully inform the person of the scope of the invention, and the present disclosure is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

At this time, it will be understood that each block of the process flow chart diagrams and combinations of the flow chart diagrams can be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates means to perform functions. These computer program instructions may also be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular way, such that the computer usable or computer readable memory The instructions stored in are also capable of producing an article of manufacture containing instruction means that perform the functions described in the flowchart block(s). The computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to generate computer or other programmable data processing equipment. Instructions for performing processing equipment may also provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is possible for the functions mentioned in the blocks to occur out of order. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in reverse order depending on their function.

A term used in the following description to identify a connection node, a term referring to network entities, a term referring to messages, a term referring to an interface between network entities, and a term referring to various types of identification information. Etc. are illustrated for convenience of description. Therefore, it is not limited to the terms used in this disclosure, and other terms that refer to objects having equivalent technical meanings may be used.

For convenience of description below, terms and names defined in the standards for 5G, NR, or LTE systems are used in the present disclosure. However, the present disclosure is not limited by these terms and names, and may be equally applied to systems conforming to other standards.

That is, in the specific description of the embodiments of the present disclosure, the communication standard established by the ^3rd generation partnership project (3GPP) will be the main target, but the main subject of the present disclosure is other communication systems having a similar technical background Even in the range that does not significantly depart from the scope of the present invention, it can be applied with slight modifications, which will be possible with the judgment of those skilled in the art of the present disclosure.

In the present disclosure, a source base station may be referred to as a source gNB, a first base station, a source cell, or a term having the same or similar meaning thereto.

Also, in the present disclosure, a target base station may be referred to as a target gNB, a second base station, a target cell, or a term having the same or similar meaning thereto. Meanwhile, in the present disclosure, a potential target base station means a target base station to which a terminal can perform handover according to conditional handover, and includes a candidate target base station, a candidate target cell, and a candidate cell. may be referred to as, or may also be referred to as a target base station, a target cell, etc., depending on the context.

In addition, in the present disclosure, a radio resource control (RRC) message may be referred to as a higher layer message, a higher level message, higher layer signaling, or a term having the same or similar meaning thereto.

1 is a diagram illustrating an example of a structure of a next-generation mobile communication system to which the present disclosure can be applied.

Referring to FIG. 1, the illustrated RAN (Radio Access Network) Nodes (1-100, 1-200) are mobile communication core networks such as EPC (Evolved Packet Core) or 5GC (5G Core Network) (1-400) It may refer to a mobile communication base station such as an LTE evolved Node B (eNodeB) or an NR next generation Node B (gNodeB) connected to a Core Network (CN). On the other hand, RAN Nodes (1-100, 1-200) can have their functions separated into CU (Centralized Unit) and DU (Distributed Unit), and CU is again CU-CP (Control Plane) and CU-UP (User Plane) ), the functions can be separated.

According to one embodiment, one RAN Node may be composed of one or more CU-CPs, one or more CU-UPs, and one or more DUs, respectively. In addition, one RAN Node may be composed of CU-CP, CU-UP and DU. For example, one RAN Node may be composed of CUs and DUs in which CU-CP and CU-UP are implemented together. Alternatively, CU-CP and DU may be implemented together in one RAN Node, and CU-UP may be configured separately. Alternatively, one RAN Node may be configured as an integrated base station in which CU-CP, CU-UP, and DU are implemented together. On the other hand, the configuration of the RAN Node as described above corresponds to only one example, and the present disclosure is not limited thereto. One RAN Node may be configured in any other combination other than the above-described examples.

According to one embodiment, CUs and DUs can support each base station function separately. For example, a CU may support a function of a radio resource control (RRC) layer or a packet data convergence protocol (PDCP) layer, and a DU may support a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical ) layer or a radio frequency (RF) layer function. In addition, the CU and DU may be connected to each other through an interface between internal functions of the base station, such as a W1 interface or an F1 interface.

According to one embodiment, CU may be divided into CU-CP and CU-UP. For example, in CU-CP, functions of RRC layer or PDCP (for RRC) layer may be supported, in CU-UP, functions of PDCP (for user data transmission) layer may be supported, and CU-CP and CU -UP may be connected through an interface between internal functions of a base station such as an E1 interface.

According to an embodiment, the base stations may be implemented as an integrated structure or a separate structure, and connection between integrated structure base stations, between separate base stations, and between integrated structure base stations and separate structure base stations may be possible. RAN Nodes may be connected through an interface between base stations such as an X2 interface or an Xn interface. In addition, the RAN Node and the Core network may be connected through an interface between the base station and the Core network, such as an S1 interface or an NG interface. Meanwhile, in the embodiments proposed in the present disclosure, in a state in which the terminal 1-300 maintains an inactive (RRC_INACTIVE) wireless connection state, small data is transmitted by connecting to an integrated or separate RAN Node. It can also be applied to transmission.

2 is a diagram illustrating a radio protocol structure of a next-generation mobile communication system to which the present disclosure can be applied.

Referring to FIG. 2, the radio protocols of the next-generation mobile communication system include NR service data adaptation protocol (SDAP) (2-01, 2-45) and NR in a terminal and an NR base station (eg, NR gNB), respectively. It can be composed of PDCP (2-05, 2-40), NR RLC (2-10, 2-35), NR MAC (2-15, 2-30), and NR PHY (2-20, 2-25). there is.

The main functions of the NR SDAPs (2-01, 2-45) may include some of the following functions.

- Transfer of user plane data

- A mapping function between a QoS flow and a data bearer for uplink and downlink (mapping between a QoS flow and a DRB for both DL and UL)

- Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

- A function of mapping reflective QoS flow to data bearer for UL SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer (or SDAP layer device), the terminal transmits the header of the SDAP layer device for each PDCP layer device or for each bearer or for each logical channel in a radio resource control (RRC) message. Whether to use or whether to use the function of the SDAP layer device can be set. When the SDAP header is set, the UE sets the Non-Access Stratum (NAS) Quality of Service (QoS) reflection setting 1-bit indicator (NAS reflective QoS) of the SDAP header and the Access Stratum (AS) QoS With the reflective configuration 1-bit indicator (AS reflective QoS), the UE may be instructed to update or reset mapping information for uplink and downlink QoS flows and data bearers. The SDAP header may include QoS flow ID information indicating QoS. QoS information may be used as data processing priority and scheduling information to support smooth service.

The main functions of the NR PDCPs (2-05, 2-40) may include some of the following functions.

- Header compression and decompression (ROHC only)

- Transfer of user data

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- PDCP PDU reordering for reception

- Duplicate detection of lower layer SDUs

- Retransmission of PDCP SDUs

- Ciphering and deciphering

- Timer-based SDU discard in uplink.

In the above description, the reordering function of the NR PDCP layer (or PDCH layer device) may refer to a function of rearranging PDCP PDUs received from a lower layer in order based on a PDCP sequence number (SN). . The reordering function of the NR PDCP layer may include a function of delivering data to a higher layer in the rearranged order. Alternatively, the order rearrangement function of the NR PDCP layer may include a function of direct delivery without considering the order. In addition, the order rearrangement function of the NR PDCP layer may include a function of rearranging the order and recording lost PDCP PDUs, and may include a function of reporting the status of the lost PDCP PDUs to the transmitter side, It may include a function of requesting retransmission of the received PDCP PDUs.

The main functions of NR RLC (2-10, 2-35) may include some of the following functions.

- Transfer of upper layer PDUs

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- ARQ function (Error Correction through ARQ)

- Concatenation, segmentation and reassembly of RLC SDUs

- Re-segmentation of RLC data PDUs

- Reordering of RLC data PDUs

- Duplicate detection

- Error detection function (Protocol error detection)

- RLC SDU discard function (RLC SDU discard)

- RLC re-establishment

In the above description, the in-sequence delivery function of the NR RLC layer (or RLC layer device) may refer to a function of sequentially delivering RLC SDUs received from a lower layer to an upper layer. If one RLC SDU is originally divided into several RLC SDUs and received, the in-sequence delivery function of the NR RLC layer may include a function of reassembling and delivering them.

The in-sequence delivery function of the NR RLC layer may include a function of rearranging received RLC PDUs based on an RLC sequence number (SN) or a PDCP sequence number (SN). In addition, the sequential delivery function of the NR RLC layer may include a function of reordering and recording lost RLC PDUs. In addition, the sequential delivery function of the NR RLC layer may include a function of reporting the status of lost RLC PDUs to the transmitter, and may include a function of requesting retransmission of the lost RLC PDUs.

In-sequence delivery of the NR RLC layer may include, when there is a lost RLC SDU, a function of sequentially delivering only RLC SDUs prior to the lost RLC SDU to a higher layer.

In-sequence delivery of the NR RLC layer, if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received before the timer starts can be sequentially delivered to the upper layer. there is.

In-sequence delivery of the NR RLC layer may include a function of sequentially delivering all RLC SDUs received up to now to a higher layer if a predetermined timer expires even if there is a lost RLC SDU.

The NR RLC layer may process RLC PDUs in the order in which they are received regardless of the order of sequence numbers (out-of sequence delivery) and deliver them to the NR PDCP layer.

When the NR RLC layer receives a segment, it may receive segments stored in a buffer or to be received later, reconstruct it into one complete RLC PDU, and deliver it to the NR PDCP layer.

The NR RLC layer may not include a concatenation function. Alternatively, the splicing function may be performed in the NR MAC layer, or the splicing function may be replaced by a multiplexing function of the NR MAC layer.

In the above description, out-of-sequence delivery of the NR RLC layer may refer to a function of immediately delivering RLC SDUs received from a lower layer to an upper layer regardless of order. Out-of-sequence delivery of the NR RLC layer may include a function of reassembling and delivering, when originally one RLC SDU is divided into several RLC SDUs and received. The out-of-sequence delivery function of the NR RLC layer may include a function of storing RLC SNs or PDCP SNs of received RLC PDUs and arranging the order to record lost RLC PDUs.

NR MACs (2-15, 2-30) may be connected to several NR RLC layers configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

- Mapping between logical channels and transport channels

- Multiplexing/demultiplexing of MAC SDUs

- Scheduling information reporting

- HARQ function (Error correction through HARQ)

- Priority handling between logical channels of one UE

- Priority handling between UEs by means of dynamic scheduling

- MBMS service identification

- Transport format selection

- Padding function (Padding)

The NR PHY layers (2-20, 2-25) channel code and modulate higher layer data, convert OFDM symbols into OFDM symbols and transmit them through a radio channel, or demodulate OFDM symbols received through a radio channel and channel decode them to a higher layer. You can perform forwarding operations.

As described above, in the next-generation mobile communication system to which the present disclosure can be applied, enhanced mobility is provided compared to conventional handover methods, such as an improvement in the success rate of handover performed as the terminal moves. To support this, we are considering a method of performing handover according to conditional handover (CHO). Conditional handover may refer to handover performed by the terminal when one or more handover execution conditions are satisfied. Hereinafter, conditional handover will be described in detail with reference to FIG. 3 .

FIG. 3 is a handover preparation procedure performed by a source base station and a potential target base station to support conditional handover according to an embodiment of the present disclosure and a pre-set conditional condition between the source base station and the potential target base station. A diagram illustrating a conditional handover change procedure for changing handover-related settings (eg, CHO configuration).

Referring to FIG. 3 , in step 3-01, the terminal 3-100 may transmit a measurement report to the source base station 3-200. Upon receiving the measurement report from the terminal 3-100, the source base station 3-200 determines the potential in step 3-10 based on the signal measurement results and determination conditions of the base stations (eg, gNBs) measured by the terminal. It may be determined to perform conditional handover (CHO) by selecting target base stations 3-300. Meanwhile, although FIG. 3 illustrates one potential target base station and a conditional handover procedure, in particular, a preparation procedure for conditional handover, the present disclosure is not limited thereto. Conditional handover according to an embodiment of the present disclosure may include determining one or more potential target base stations, performing a procedure for conditional handover with each potential target base station, and each potential target base station. The same procedure shown in FIG. 3 may be performed for the target base station. After determining to perform the conditional handover, the source base station 3-200 may transmit a handover request message (eg, a HANDOVER REQUEST message) to the potential target base station 3-300 in step 3-02. . In this case, the handover request message may include an indicator (eg, CHO initiation) indicating that the handover requested by the source base station 3-200 is a conditional handover. Meanwhile, the handover request message may include RRC Context along with protocol data unit (PDU) session resource (PDU session resource) information. RRC Context may include a handover preparation information message (eg, HandoverPreparationInformation message). The PDU session resource information and the handover preparation information message, which is RRC Context, may be information desired to be accepted and configured by the potential target base station 3-300. Upon receiving the handover request message, the potential target base station 3-300 sends a handover request confirmation message (for example, a HANDOVER REQUEST ACKNOWLEDGE message) to the source base station 3-200 in step 3-03 in response thereto. can transmit. The handover request confirmation message includes a handover command message (eg, HandoverCommand message) may be included. The potential target base station 3-300 may accept all or part of the PDU session resources received from the source base station 3-200. In addition, all of the RRC Context settings received from the source base station 3-200 may be followed, or some settings may be followed. Upon receiving the handover request confirmation message, the source base station (3-200) includes the handover command message in the handover request confirmation message in the RRC message (eg, RRC Reconfiguration message) in step 3-04, and the terminal (3-200) -100). At this time, the handover command message is transparent to the source base station 3-200. In other words, the source base station 3-200 does not check the content of the handover command message, and as described above, carries the handover command message in the RRC message and only serves to deliver it to the terminal 3-100. Upon receiving the RRC message, the terminal 3-100 may complete the preparation procedure for conditional handover by transmitting an RRC message (eg, RRC Reconfiguration Complete message) in step 3-05 in response thereto. Meanwhile, according to an embodiment, the preparation procedure for conditional handover corresponding to steps 3-01, 3-02, 3-03, 3-04, 3-05, and 3-10 of FIG. 3 is an initial conditional handover. It may be referred to as a setup procedure.

Meanwhile, after initial configuration for supporting conditional handover is completed, the source base station 3-200 may change (or amend) conditional handover-related settings previously set by the potential target base station 3-300. there is. In step 3-20, the source base station 3-200 may determine to change conditional handover-related settings. In step 3-06, the source base station 3-200 may transmit a handover request message (eg, a HANDOVER REQUEST message) to the target base station 3-300 that has completed the existing conditional handover setup. At this time, in the handover request message (eg, HANDOVER REQUEST message) transmitted to the target base station (3-300) in step 3-06, an indicator indicating that the message intends to change the existing conditional handover setting (eg, For example, a CHO Replace indicator) may be included. In addition, the handover request message may include changed conditional handover settings, that is, PDU session resources and RRC Context. Upon receiving a handover request message (eg, HANDOVER REQUEST message) including an indicator indicating that the existing conditional handover setting is to be changed, the potential target base station 3-300 receives the message as conditional handover setting It can be recognized that it was sent to change. In response to this, the target base station 3-300 may transmit a handover request confirmation message (eg, a HANDOVER REQUEST ACKNOWLEDGE message) to the source base station 3-200 in step 3-07. At this time, the handover request confirmation message transmitted in step 3-07 may include a PDU session resource newly accepted and configured by the potential target base station 3-300 and a handover command. In step 3-08, the source base station 3-200 that has received the handover request confirmation message receives an RRC message including the handover command received in step 3-07, similarly to the initial setting for conditional handover ( For example, an RRC Reconfiguration message) may be transmitted to the terminal 3-100. Upon receiving the RRC message, the UE 3-100 can recognize the changed conditional handover configuration. Thereafter, in step 3-09, the terminal 3-100 transmits an RRC message (eg, an RRC Reconfiguration Complete message) to the source base station 3-200 in response thereto, thereby changing the conditional handover configuration. process can be completed.

As described above, the potential target base station 3-300 accepts all settings based on handover preparation information (eg, HandoverPreparationInformation), which is an RRC Context transmitted by the source base station 3-200. You can decide whether to accept some settings. This may also be performed in the same way in a procedure for changing conditional handover settings. For example, as the source base station 3-200 determines to change the preset conditional handover settings in step 3-20, the corresponding message in the handover request message indicates that the conditional handover settings are to be changed. Even if RRC Context is transmitted to the potential target eNB 3-300 together with an indicator (eg, CHO Replace indicator), the potential target eNB 3-300 determines not to change the existing conditional handover configuration in consideration of various circumstances. may be That is, there may be cases in which the handover command message transmitted in step 3-03 and the handover command message transmitted in step 3-07 include the same information. Meanwhile, as described above, the source base station 3-200 does not check the content of the handover command message and transmits it to the terminal 3-100 as it is. Therefore, in this case, the handover command message delivered to the terminal 3-100 through the RRC message (eg, RRC Reconfiguration message), that is, the configuration of the potential target base station 3-300 is also the same, which is the same information. This means that is transmitted to the terminal 3-100 in duplicate, which may cause unnecessary waste in terms of radio resources and processing power of the terminal. Therefore, the present disclosure proposes a method capable of solving problems such as waste of radio resources, processing power of a terminal, and increased overhead in a network due to unnecessary signal transmission and reception, which may occur in a conditional handover change procedure. Hereinafter, it will be described in detail with reference to FIG. 4 .

4 is a diagram of a terminal, a source base station, and a target according to embodiments proposed in the present disclosure to solve problems caused by duplicate handover command messages including the same information being transmitted to the terminal in a conditional handover change procedure. It is a diagram showing the overall operation of the base station.

Referring to FIG. 4 , a preparation procedure 100 for conditional handover is the same as that described in FIG. 3 , and thus a description thereof will be omitted. After the initial configuration for conditional handover, the source base station 4-200 may decide to change the preset conditional handover configuration. In this case, the first embodiment including steps 4-20 to 4-21 ( 200) or operations of the source base station and the target base station according to the second embodiment 300 including steps 4-30 to 4-31 may be performed. Hereinafter, each embodiment will be described in detail with reference to FIGS. 5 to 12 .

5 is a diagram illustrating an operation of a target base station according to the first embodiment of the present disclosure.

In the first embodiment, a new indicator may be added to a handover request message (eg, a HANDOVER REQUEST message). The source base station 4-200 includes a conditional handover related indicator (eg, the above-described CHO Replace indicator) and an indicator allowing omission of RRC context (eg, Permission to omit RRC Context indicator) in the handover request message. Can be transmitted to the target base station (4-300) including. In step 5-100, the potential target base station 4-300 sends a handover request message including an indicator (eg, CHO Replace indicator) indicating that the handover request message intends to change the conditional handover configuration. can receive In step 5-200, the target base station 4-300 does not include the RRC Context in the handover request confirmation message and may check whether it can be transmitted to the source base station 4-200. That is, the target base station 4-300 sends an RRC message to the handover request confirmation message based on whether an indicator allowing omission of the RRC context (eg, Permission to omit RRC Context) is included in the handover request message. It can be checked whether it can be transmitted to the source base station 4-200 without including the Context. If the corresponding indicator (eg, Permission to omit RRC Contxt) is not included in the handover request message, in step 5-500, the target base station 4-300 sends a handover command message to the handover request confirmation message. can be transmitted, including In contrast, if the corresponding indicator (eg, Permission to omit RRC Contxt) is included in the handover request message, in step 5-300, the potential target base station 4-300 is the previous (eg, recent) It may be checked whether the handover command message (eg, old HandoverCommand) transmitted to the source base station is the same as the currently newly generated handover command message (eg, New HandoverCommand). When the handover command message previously transmitted to the source base station (eg, old HandoverCommand) and the currently newly generated handover command message (eg, New HandoverCommand) are the same, in step 5-400, the target base station (4) -300) may transmit a handover request confirmation message that does not include the currently generated handover command message to the source base station 4-200. On the other hand, if the handover command message previously transmitted to the source base station (eg, old HandoverCommand) is different from the currently newly generated handover command message (eg, New HandoverCommand), in step 5-500, the target The base station 4-300 may transmit a handover request confirmation message including a newly generated handover command message (eg, New HandoverCommand) to the source base station 4-200.

That is, the potential target base station 4-300, which has received permission from the source base station 4-200 to send a handover request confirmation message that does not include an RRC Context, performs a newly created handover based on the current conditional handover configuration. When the information included in the command message is the same as the information included in the handover command message previously (or recently) transmitted to the source base station 4-200, the target base station 4-300 currently performs a newly generated handover. The handover request confirmation message may be configured by excluding (or omitting) the command message. The source base station 4-100 receiving the handover request confirmation message without such a handover command message sends the terminal 4-100 a handover command message or an RRC message including information in the handover command message (e.g. For example, the step of transmitting the RRC Reconfiguration message (step 4-40 of FIG. 4) can be omitted, and accordingly, in response to the RRC message received by the terminal, the RRC message (eg, For example, the step of transmitting the RRC Reconfiguration Complete message (steps 4-41 of FIG. 4) may also be omitted.

Meanwhile, steps 5-100 to 5-500 of FIG. 5 may be performed simultaneously or some may be omitted.

6 is a diagram illustrating an operation of a source base station according to a first embodiment of the present disclosure.

Referring to FIG. 6, in step 6-100, when the source base station 4-200 determines to change the conditional handover configuration, the handover including the conditional handover-related indicator (eg, the CHO Replace indicator described above). An over request message may be transmitted to the target base station 4-300. At this time, the handover request message may include an indicator allowing omission of the RRC context (eg, Permission to omit RRC Context). In step 6-200, the source base station 4-200 may receive a handover request confirmation message from the target base station 4-300. Meanwhile, when the handover request message transmitted to the target base station 4-300 in step 6-100 includes an indicator allowing omission of the RRC context, the source base station 4-200 receives the handover request message in step 6-200. The handover request confirmation message may or may not include a handover command message. If the handover request confirmation message includes the handover command message, in step 6-300, the source base station 4-200 sends an RRC message (eg, RRC Reconfiguration message) including the handover command message. It can be transmitted to the terminal 4-100. In response to this, in step 6-400, the source base station 4-200 may receive an RRC message (eg, an RRC Reconfiguration complete message) from the terminal 4-100. Alternatively, if the handover request confirmation message does not include the handover command message, the source base station 4-200 may omit operations of steps 6-300 to 6-400.

7 is a diagram illustrating a message and an information element (IE) according to the first embodiment of the present disclosure.

As described above, according to the first embodiment of the present disclosure, as a new IE in the handover request message 7-100 transmitted from the source base station to the potential target base station, an indicator allowing omission of the RRC context (eg, , Permission to omit RRC Context) (7-10) can be defined. As described above with reference to FIGS. 4 to 6, the potential target base station receiving the handover request message including the corresponding IE under specific conditions (e.g., the handover command message previously transmitted to the source base station and the currently newly generated handover The handover request confirmation message 7-200 may be configured by including or excluding the handover command message depending on whether the command message is the same or different, and transmit the handover request confirmation message 7-200 to the target base station. To this end, according to an embodiment of the present disclosure, a Target NG-RAN node To Source NG-RAN node Transparent Container (7-20) that contains the handover command message in the handover request confirmation message (7-200) The presence of can be set as optional.

On the other hand, in the above-described first embodiment, the handover command message transmits the handover request message based on whether an indicator allowing omission of the RRC context (eg, Permission to omit RRC Context) is included in the handover request message. Although it has been described that whether or not to be included in a message and transmitted is determined, the present disclosure is not limited thereto. For example, an indicator related to whether omission of the RRC context is allowed may be included in the handover request message, and whether the indicator indicates that omission of the RRC context is allowed (eg, indicates a first value or a TRUE value), or The above-described procedure may be performed depending on whether omission of the RRC context is not permitted (eg, indicating a second value or a FALSE value).

8 is a diagram illustrating an operation of a target base station according to a second embodiment of the present disclosure.

In the second embodiment, a new indicator may be added to the handover request confirmation message. Referring to FIG. 8 , in step 8-100, the target base station 4-300 may receive a handover request message including a conditional handover-related indicator (eg, the aforementioned CHO Replace indicator). In step 6-200, the potential target base station 4-300 transmits a handover command message (eg, old HandoverCommand) previously (or recently) transmitted to the source base station and a newly generated handover command message (eg, For example, it is possible to check whether New HandoverCommand) is the same. For example, the target base station 4-300 determines whether information included in a handover command message previously (or recently) transmitted to the source base station is the same as information included in a newly generated handover command message. You can check. If the case is the same, in step 8-300, the target base station 4-300 includes an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator) in the handover request confirmation message, and returns to the source base station (4-300). 200) can be transmitted. Alternatively, if different, in step 8-400, the target base station 4-300 does not include an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator) in the handover request confirmation message, and performs handover A request confirmation message may be transmitted to the source base station 4-200. Meanwhile, according to the second embodiment of the present disclosure, when the information included in the handover command message previously (or recently) transmitted to the source base station and the information included in the currently newly generated handover command message are the same or different In this case, the handover command message generated based on the current configuration may be included in the handover request confirmation message and transmitted to the source base station 4-200.

Upon receiving the handover request confirmation message including an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator), the source base station 4-200 sends a handover command message to the terminal 4-100 or handover The step of transmitting the RRC message (eg, RRC Reconfiguration message) including the information in the command message (steps 4-40 of FIG. 4) may be omitted, and accordingly, the source base station responds to the RRC message received by the terminal. The step of transmitting the RRC message (eg, RRC Reconfiguration Complete message) to (4-200) (step 4-41 of FIG. 4) may also be omitted.

9 is a diagram illustrating an operation of a source base station according to a second embodiment of the present disclosure.

Referring to FIG. 9, in step 9-100, when the source base station 4-200 determines to change the conditional handover configuration, the handset including the conditional handover-related indicator (eg, the CHO Replace indicator described above). An over request message may be transmitted to the target base station 4-300. In step 9-200, the source base station 4-200 may receive a handover request confirmation message from the target base station 4-300. If the handover request confirmation message received in step 9-200 does not include an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator), the source base station (4-200) in step 9-300 may transmit an RRC message (eg, RRC Reconfiguration message) including the handover command message received through the handover request confirmation message to the terminal 4-100. In response to this, in step 9-400, the source base station 4-200 may receive an RRC message (eg, an RRC Reconfiguration complete message) from the terminal 4-100. Alternatively, if the handover request confirmation message received in step 9-200 includes an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator), the source base station 4-200 Operations of steps 9 through 400 may be omitted.

10 is a diagram illustrating a message and an IE according to the second embodiment of the present disclosure.

As described above, according to the second embodiment 2 of the present disclosure, as a new IE in the handover request confirmation message 10-100 transmitted from the potential target base station to the source base station, an indicator instructing to ignore the RRC context (eg For example, Ignore RRC Context indicator) (10-10) can be defined. As described above with reference to FIGS. 4, 8, and 9, the potential target base station is determined under a specific condition (eg, when the handover command message previously transmitted to the source base station is the same as or different from the currently newly generated handover command message). ), the source that received the handover command message by including or not including an indicator (eg, Ignore RRC Context indicator) 10-10 instructing to ignore the RRC context in the handover request confirmation message The base station may or may not transmit this to the terminal. For example, when the source base station receives a handover request confirmation message including an indicator (eg, Ignore RRC Context) 10-10 indicating to ignore the RRC context from the target base station, the source base station performs handover The handover command message in the request confirmation message or the information included in the handover command message may not be transmitted to the terminal. Alternatively, when the source base station receives a handover request confirmation message from the target base station that does not include an indicator (eg, Ignore RRC Context) 10-10 indicating to ignore the RRC context, the source base station requests handover A handover command message in the confirmation message or information included in the handover command message may be transmitted to the terminal.

Meanwhile, in the above-described second embodiment, depending on whether the information included in the handover command message previously (or recently) transmitted to the source base station and the information included in the newly generated handover command message are the same or different, Although the handover request confirmation message has been described as including or not including an indicator instructing to ignore the RRC context (eg, Ignore RRC Context indicator), the present disclosure is not limited thereto. For example, an indicator on whether or not to ignore the RRC context is included in the handover request confirmation message, and information included in the handover command message previously (or recently) transmitted to the source base station and the currently newly generated handover command Depending on whether the information included in the message is the same or different, the indicator may indicate to ignore the RRC context (eg, a third value or a TRUE value) or may indicate not to ignore the RRC context (eg, a third value or a TRUE value) For example, indicating a fourth value or a FALSE value), the above-described procedure may be performed accordingly.

According to the above-described embodiments, a method for preventing handover command messages including identical information from being repeatedly transmitted from a source base station to a terminal in a conditional handover change procedure is provided. Accordingly, problems such as waste of unnecessary radio resources can be solved, and more efficient conditional handover can be supported.

11 is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 11 , a terminal may include a transceiver 11-10, a controller 11-20, and a memory 11-30. In the present disclosure, the controller may be defined as a circuit or an application-specific integrated circuit or at least one processor.

The transmitting/receiving unit 11-10 may transmit/receive signals with other network entities. For example, the transceiver 11-10 may receive a signal including an RRC message (eg, RRC Reconfiguration message) from the base station, and transmit an RRC message (eg, RRC Reconfiguration Complete message) to the base station. signals can be transmitted.

The control unit 11-20 may control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the control unit 11-20 may control signal flow between blocks to perform an operation according to the above-described flowchart. Specifically, the control unit 11-20 sets a value for conditional handover based on the received RRC message (eg, RRC Reconfiguration message) according to an embodiment of the present disclosure. You can control what it does.

The memory 11-30 may store at least one of information transmitted and received through the transceiver 11-10 and information generated through the control unit 11-20. For example, the memory 11-30 may store setting values of potential target cells for handover.

12 is a diagram showing the structure of a base station according to an embodiment of the present disclosure.

The base station shown in FIG. 12 may correspond to a source base station or a target base station according to an embodiment of the present disclosure.

Referring to FIG. 12, a base station may include a wireless transceiver 12-10, a base station/core network transceiver 12-20, a control unit 12-30, and a memory 12-40. In the present disclosure, the controller may be defined as a circuit or an application-specific integrated circuit or at least one processor.

The base station shown in FIG. 12 may be a RAN node including both gNB-CU and gNB-DU. The RAN node is an LTE eNB (evolved Node B, eNodeB) or NR gNB (next generation Node B, gNodeB) connected to a mobile communication core network (Core Network, CN) such as EPC (Evolved Packet Core) or 5GC (5G Core Network). ), etc., may mean a mobile communication base station. Meanwhile, the RAN node may be divided into a Centralized Unit (CU) and a Distributed Unit (DU), and the CU may again have functions separated into a CU-CP (Control Plane) and a CU-UP (User Plane).

According to one embodiment, one RAN Node may be composed of one or more CU-CPs, one or more CU-UPs, and one or more DUs, respectively. In addition, one RAN Node may be composed of CU-CP, CU-UP and DU. For example, one RAN Node may be composed of CUs and DUs in which CU-CP and CU-UP are implemented together. Alternatively, CU-CP and DU may be implemented together in one RAN Node, and CU-UP may be configured separately. Alternatively, one RAN Node may be configured as an integrated base station in which CU-CP, CU-UP, and DU are implemented together. On the other hand, the configuration of the RAN Node as described above corresponds to only one example, and the present disclosure is not limited thereto. One RAN Node may be configured in any other combination other than the above examples.

According to one embodiment, CUs and DUs can support each base station function separately. For example, a CU may support functions of an RRC layer or a PDCP layer, and a DU may support functions of an RLC layer, a MAC layer, a PHY layer, or an RF layer. In addition, the CU and DU may be connected to each other through an interface between internal functions of the base station, such as a W1 interface or an F1 interface.

According to one embodiment, CU may be divided into CU-CP and CU-UP. For example, in CU-CP, functions of RRC layer or PDCP (for RRC) layer may be supported, in CU-UP, functions of PDCP (for user data transmission) layer may be supported, and CU-CP and CU -UP may be connected through an interface between internal functions of a base station such as an E1 interface.

According to an embodiment, the base stations may be implemented as an integrated structure or a separate structure, and connection between integrated structure base stations, between separate base stations, and between integrated structure base stations and separate structure base stations may be possible. RAN Nodes may be connected through an interface between base stations such as an X2 interface or an Xn interface. In addition, the RAN Node and the Core network may be connected through an interface between the base station and the Core network, such as an S1 interface or an NG interface.

The wireless transceiver 12-10 may transmit and receive signals with other network entities. For example, the wireless transceiver 12-10 may transmit/receive a signal from a terminal or transmit a signal including a message such as an RRC message (eg, an RRC Reconfiguration message) for controlling an operation of the terminal.

The other base station/core network transmission/reception units 12-20 may transmit/receive signals with other network entities. For example, uplink data or downlink data exchanged with a user plane function (UPF) may be transmitted and received.

The control unit 12-30 may control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the control unit 12-30 may control signal flow between blocks to perform an operation according to the flowchart described above.

The memory 12-40 stores at least one of information transmitted and received through the wireless transceiver 12-10 and the other base station/core network transceiver 12-20 and information generated through the control unit 12-30. can For example, the memory 12-40 may store information included in a recently transmitted handover command message.

In the specific embodiments of the present disclosure described above, constituent elements included in the present disclosure are expressed in singular or plural numbers according to the specific embodiments presented. However, the singular or plural expressions are selected appropriately for the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components, and even components expressed in plural are composed of the singular number or singular. Even the expressed components may be composed of a plurality.

On the other hand, the embodiments disclosed in the present specification and drawings are only presented as specific examples to easily explain the technical content of the present disclosure and help understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other modified examples based on the technical idea of the present disclosure can be implemented. In addition, each embodiment can be operated in combination with each other as needed. For example, parts of one embodiment and another embodiment of the present disclosure may be combined with each other. In addition, the embodiments may be implemented in other systems, for example, LTE systems, 5G or NR systems, and other modifications based on the technical idea of the above-described embodiments.

Claims (1)

A control signal processing method in a wireless communication system,
Receiving a first control signal transmitted from a base station;
processing the received first control signal; and
and transmitting a second control signal generated based on the processing to the base station.

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