KR20210103269A - Method and apparatus to minimize the data transmission/reception interruption time in the conditional handover - Google Patents

Abstract

The present invention relates to a communication technique and a system for converging a 5G communication system with IoT technology to support a higher data transmission rate after a 4G system. The invention may be applied to intelligent services (e.g., a smart home, a smart building, a smart city, a smart car or a connected car, healthcare, digital education, a retail business, a security and safety-related service, and the like) based on 5G communication technology and IoT-related technology. Disclosed are operations of a terminal and a base station for minimizing data transmission interruption time between the terminal and the base station when performing a conditional handover in a mobile communication system. A control signal processing method in a wireless communication system comprises: a step of receiving a first control signal transmitted from the base station; a step of processing the received 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 to minimize the data transmission/reception interruption time in the conditional handover

The present invention relates to an operation of a terminal and a base station for minimizing a data transmission interruption time between a terminal and a base station when a condition-based handover is performed in a mobile communication system.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or the pre-5G communication system is called a system after the 4G network (Beyond 4G Network) communication system or after the LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as 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, in the 5G communication system, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, for network improvement 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 (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Technology development is underway. In addition, in the 5G system, FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), which are advanced coding modulation (ACM) methods, and FBMC (Filter Bank Multi Carrier), which are advanced access technologies, NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network where humans create and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers, etc. with IoT technology, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) are being studied. In the IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects and creates new values in human life 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 appliance, 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, in technologies such as sensor network, machine to machine (M2M), and machine type communication (MTC), 5G communication technology is implemented by techniques such as beam forming, MIMO, and array antenna. there will be The application of cloud radio access network (cloud RAN) as the big data processing technology described above can be said to be an example of the convergence of 5G technology and IoT technology.

When a handover, which is a cell-to-cell switching procedure of a terminal, is performed in a mobile communication system, the terminal is in a data transmission/reception disconnection state for a certain period of time, which causes a time delay in data transmission/reception by the terminal. Therefore, there is a need to reduce the time delay.

An object of the present invention is to perform a condition-based handover in a mobile communication system, when the terminal performs a radio resource control (RRC) reconfiguration procedure to a selected cell, the selected cell We propose a method of effectively reducing data transmission interruption time by waiting until transmission of the first physical random access channel (PRACH) of PRACH is possible and then initiating the RRC reconfiguration procedure.

The present invention for solving the above problems is a control signal processing method in a wireless communication system, the method comprising: 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 an embodiment of the present invention, when the UE performs the RRC Reconfiguration procedure with the selected cell, the UE waits until the first PRACH transmission of the selected cell is possible and then initiates the RRC Reconfiguration procedure, thereby stopping data transmission occurring during handover. It is possible to reduce the time and effectively transmit and receive data between the terminal and the base station.

1A is a diagram showing the structure of a next-generation mobile communication system.
1B is a diagram illustrating a radio protocol structure in a mobile communication system to which the present invention is applied.
1C is a flowchart of a process of performing a first handover operation in a mobile communication system.
1D is a flowchart of a process of performing a second handover operation in a mobile communication system.
FIG. 1E is a diagram for explaining a process of performing a handover in an LTE system.
1F is a flowchart of a process of minimizing data transmission interruption time in condition-based handover.
1G is a flowchart of a terminal operation for minimizing data transmission interruption time in condition-based handover.
1H is a block diagram illustrating an internal structure of a terminal to which the present invention is applied.
1I is a block diagram showing the configuration of a base station according to the present invention.

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

For the same reason, some components are exaggerated, omitted, or schematically illustrated in the accompanying drawings. In addition, the size of each component does not fully reflect the actual size. In each figure, the same or corresponding elements are assigned the same reference numerals.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may 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, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment 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 also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may in fact be performed substantially simultaneously, or it is possible that the blocks are sometimes performed in the reverse order according to the corresponding function.

At this time, the term '~ unit' used in this embodiment means software or hardware components such as FPGA or ASIC, and '~ unit' performs certain roles. However, '-part' is not limited to software or hardware. The '~ unit' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Thus, as an example, '~' denotes components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to play one or more CPUs in a device or secure multimedia card.

In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is prepared based on a Long-Term Evolution (LTE) system, but is also applied to other mobile communication systems such as (New Radio) (NR), which is a next-generation mobile communication system. As an example, in the present invention, evolved Node B (eNodeB, eNB) in LTE is New Radio Node B (gNodeB, gNB) in NR, Mobility Management Entity (MME) in LTE is Access and Mobility Management Function in NR ( AMF).

1A is a diagram illustrating an EN-DC structure of a next-generation mobile communication system.

The EN-DC means dual connectivity between EUTRAN (LTE system) and NR (next-generation mobile communication system), and is a scenario in which one terminal is simultaneously connected to two different types of systems to receive a service.

Referring to FIG. 1A, as shown, the radio access network of the next-generation mobile communication system is composed of a next-generation base station (New Radio Node B, hereinafter gNB) 1a-10 and AMF (1a-05, New Radio Core Network). . A user terminal (New Radio User Equipment, hereinafter NR UE or terminal) 1a-15 accesses an external network through gNB 1a-10 and AMF 1a-05.

In FIG. 1A , gNBs 1a-10 correspond to an Evolved Node B (eNB) of an existing LTE system. The gNB is connected to the NR UE 1a-15 through a radio channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device for scheduling by collecting status information such as the buffer status of the UEs, the available transmission power status, and the channel status is required. 1a-10) is in charge. One gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the existing LTE, it can have more than the existing maximum bandwidth, and additionally beamforming technology can be grafted by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as a radio access technology. . In addition, an Adaptive Modulation & Coding (AMC) scheme that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The AMF 1a-05 performs functions such as mobility support, bearer setup, QoS setup, and the like. AMF is a device in charge of various control functions as well as mobility management functions for the terminal and is connected to a number of base stations. In addition, the next-generation mobile communication system can be linked with the existing LTE system, and the AMF is connected to the MME (1a-25) through a network interface. The MME may be connected to the existing base station eNB (1a-30). In the EN-DC scenario, the gNB can be controlled by being connected to the eNB.

1B is a diagram illustrating a radio protocol structure in a mobile communication system to which the present invention is applied.

The control plane radio protocol of the mobile communication system is RRC (Radio Resource Control, 1b-02, 1b-45), PDCP (Packet Data Convergence Protocol 1b-05, 1b-40), RLC (Radio Link Control 1b) in the terminal and gNB, respectively. -10, 1b-35) and MAC (Medium Access Control 1b-15, 1b-30). RRC (Radio Resource Control, 1b-02, 1b-45) is in charge of RRC connection and mobility support related settings, and PDCP (Packet Data Convergence Protocol) (1b-05, 1b-40) is for IP header compression/restore, etc. In charge of the operation, radio link control (hereinafter referred to as RLC) 1b-10, 1b-35 reconfigures a PDCP packet data unit (PDU) to an appropriate size to perform ARQ operation and the like. The MACs 1b-15 and 1b-30 are connected to several RLC layer devices configured in one terminal, and perform operations of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The physical layer (1b-20, 1b-25) channel-codes and modulates upper layer data, creates OFDM symbols and transmits them over a radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel and transmits them to higher layers do the action

1C is a flowchart of a process of performing a first handover operation in a mobile communication system.

The terminal 1c-05 receives a predetermined radio resource control (RRC) message including measurement configuration information from a source cell 1c-10 (1c-25). The terminal measures the signal quality of the source cell and neighboring cells by applying the measurement configuration information, and reports the collected cell measurement information to the source cell periodically or when a configured event occurs (1c-30) ( 1c-35). The source cell determines whether to trigger the first handover operation based on the reported cell measurement information (1c-40). For example, when event A3 (Neighbor becomes offset better than SpCell) is satisfied and cell measurement information is reported, the source cell may determine the first handover. If it is decided to trigger the first handover, the source cell requests the first handover to one target cell 1c-20 through a predetermined inter-node message. do (1c-45). Upon receiving the request, the target cell accepts the request, and transmits handover configuration information necessary for the first handover operation to the source cell (1c-50). The source cell stores the handover configuration information and additional configuration information received from the target cell in a predetermined RRC message, and transmits the RRC message to the UE (1c-55). The configuration information includes the ID of the target cell, frequency information, configuration information necessary for a random access operation to the target cell (dedicated preamble information, dedicated radio resource information, etc.), transmission power information, and a cell radio network temporary identifier used in the target cell (cell). radio network temporary identity, C-RNTI) information and the like.

Upon receiving the handover configuration information, the terminal immediately performs a random access process to the target cell and starts the T304 timer (1c-60). The terminal transmits the provided preamble (1c-65). If a dedicated preamble is not provided, one of the preambles used in the contention basis is transmitted. Upon receiving the preamble, the target cell transmits a random access response message (RAR) to the UE (1c-70). The terminal transmits message3 (msg3) to the target cell using uplink resource (UL grant) information contained in the RAR (1c-75). The msg3 accommodates an RRC connection reconfiguration complete (RRCConnectionReconfigurationComplete) message in the case of an LTE system and an RRCReconfigurationComplete message in the case of an NR system. When the random access process is successfully completed, it is considered that the first handover has been successfully completed, and the running T304 timer is stopped. If the first handover is not successfully completed until the T304 timer expires, it is regarded as a handover failure.

1D is a flowchart of a process of performing a second handover operation in a mobile communication system.

The terminal 1d-05 reports its capability information to the source cell 1d-10 (1d-25). The capability information includes whether the terminal supports the second handover. The UE receives a predetermined RRC message including measurement configuration information from the source cell (1d-30). The terminal measures the signal quality of the source cell and neighboring cells by applying the measurement configuration information, and reports the collected cell measurement information to the source cell periodically or when a configured event occurs (1d-35) ( 1d-40). The source cell determines whether to trigger a second handover operation based on the reported cell measurement information (1d-45). In order to configure the second handover, the terminal must be able to support the second handover. If it is determined to trigger the second handover, the source cell requests the second handover to one or more target cells 1d-20 through a predetermined inter-node message (1d-50). The target cells that have received the request accept it, and transmit handover configuration information necessary for the second handover operation to the source cell (1d-55). Target cells that have not accepted the request are excluded from the second handover. The source cell stores the handover configuration information and additional configuration information received from the target cells in a predetermined RRC message, and transmits the RRC message to the UE (1d-60). The configuration information includes ID of target cells, frequency information, configuration information necessary for random access operation to target cells (dedicated preamble information for each target cell, dedicated radio resource information, etc.), transmission power information, and C used in each target cell. -RNTI information, conditions for triggering a random access operation to each target cell, etc. are included. Each of the conditions may be different for each target cell, and a plurality of conditions may be set for one target cell.

Upon receiving the handover configuration information, the terminal evaluates whether the provided condition(s) is satisfied (1d-65). If a condition related to a specific target cell is satisfied, a random access process is performed to the target cell and a T304 timer is driven (1d-70). For example, Event A3 (Neighbor becomes offset better than SpCell) is set as the above condition, and if it is satisfied, the UE transmits the provided preamble to the associated target cell (1d-75). If the dedicated preamble is not provided, one of the preambles used in the contention base is transmitted. Upon receiving the preamble, the target cell transmits a random access response message (RAR) to the UE (1d-80). The UE transmits msg3 to the target cell by using the UL grant information contained in the RAR (1d-85). The msg3 contains an RRCConnectionReconfigurationComplete message in the case of an LTE system and an RRCReconfigurationComplete message in the case of an NR system. When the random access process is successfully completed, it is considered that the second handover has been successfully completed, and the running T304 timer is stopped. If the second handover is not successfully completed until the T304 timer expires, it is regarded as a handover failure.

When the handover is successfully completed, the terminal deletes the handover configuration information. When the source cell receives the handover success report from the target cell, it deletes the context information of the terminal. The success or failure can also be determined by the UE context release message, which is an inter-node message transmitted to the target cell to the source cell. In addition, the source cell instructs other candidate target cells included in the handover configuration information to delete the handover configuration information (or UE context information) (or notifies that it is no longer valid). The candidate target cells may delete the handover configuration information by themselves when a predetermined time elapses after receiving the handover request without an instruction from the source cell.

FIG. 1E is a diagram for explaining a process of performing a handover in an LTE system.

The terminal 1e-02 in the connected mode reports the cell measurement information (Measurement Report) to the current source cell (or serving cell, serving cell, 1e-01) when periodic or a specific event is satisfied (1e-04) . The source cell determines whether or not to handover the terminal to a neighboring cell based on the measurement information. Handover is a technology for changing a primary cell (PCell) that provides a service to a terminal in a connected mode state to one of the adjacent cells. The source cell requests a handover to a new cell that will provide a service to the UE, that is, a target cell 1e-03 (1e-05). If the target cell accepts this, it transmits a HO command message to the current source cell (1e-06). The HO command is transmitted from the source cell to the terminal using an RRC Connection Reconfiguration message (1e-07). At the same time, data transmission/reception with the source cell is stopped. The terminal attempts random access to the target cell indicated by the source cell. The random access is for notifying the target cell that the terminal is moving through handover and at the same time synchronizing uplink. For the random access, the terminal transmits a preamble ID provided from the source cell or a preamble corresponding to a randomly selected preamble ID to the target cell (1e-08). After the preamble transmission, after a specific number of subframes have elapsed, the terminal monitors whether a random access response message (RAR) is transmitted from the target cell. The monitoring time period is referred to as a random access response window (RAR window). During the specified time, if a RAR is received (1e-09). The terminal responds to the target cell with an RRC Connection Reconfiguration Complete message (1e-10). Accordingly, the terminal attempts to receive data from the RAR window start time for the target cell, and after receiving the RAR, starts transmitting to the target cell while transmitting an RRC Connection Reconfiguration Complete message.

Looking at the existing handover process, a specific terminal cannot transmit or receive its own data from the time it receives the HO command from the existing source cell to the time at which it transmits the RRC Connection Reconfiguration Complete message in which the handover is completed. This data transmission/reception disconnected state causes a predetermined time delay in data transmission/reception by the terminal, which is called an interruption time. In order to reduce the interruption time, an improvement plan for maintaining data transmission/reception with the source cell is introduced until the time when the first preamble is transmitted to the target cell, not the time when the HO command is received. This is called MBB (Make Before Break) technology. This was developed considering a terminal with a single RX/TX chain.

1F is a flowchart of a process of minimizing data transmission interruption time in condition-based handover.

The terminal 1f-05 reports its capability information to the source cell 1f-10 (1f-25). The capability information includes whether the terminal supports the second handover and whether the method for reducing the interruption time proposed in the present invention is supported. The UE receives a predetermined RRC message including measurement configuration information from the source cell (1f-30). The terminal measures the signal quality of the source cell and neighboring cells by applying the measurement configuration information, and reports the collected cell measurement information to the source cell periodically or when a configured event occurs (1f-35) ( 1f-40). The source cell determines whether to trigger a second handover operation based on the reported cell measurement information (1f-45). In order to configure the second handover, the terminal must be able to support the second handover. If it is determined to trigger the second handover, the source cell requests the second handover to one or more target cells 1f-20 through a predetermined inter-node message (1f-50). The target cells that have received the request accept it, and transmit handover configuration information necessary for the second handover operation to the source cell (1f-55). Target cells that have not accepted the request are excluded from the second handover. The source cell stores the handover configuration information and additional configuration information received from the target cells in a predetermined RRC message, and transmits the RRC message to the UE (1f-60). The configuration information includes ID of target cells, frequency information, configuration information necessary for random access operation to target cells (dedicated preamble information for each target cell, dedicated radio resource information, etc.), transmission power information, and C used in each target cell. -RNTI information, conditions for triggering a random access operation to each target cell, etc. are included. Each of the conditions may be different for each target cell, and a plurality of conditions may be set for one target cell.

Upon receiving the handover configuration information, the terminal evaluates whether the provided condition(s) is satisfied, and searches for one or more target cells that satisfy the condition (1f-65). If there is one target cell that satisfies the above condition, the cell is selected. Otherwise, if there are two or more target cells that satisfy the above condition, one target cell is selected according to a predetermined rule. (1f-70). That is, a candidate cell is set with an RRCReconfiguration message, and cells satisfying the execution condition become candidate target cells, and the terminal selects one of them and is selected. The handover procedure is initiated based on the conditions set in RRCReconfiguration for the cell. In particular, when determining a selected cell from a plurality of candidate target cells, in order to reduce the interruption time, a first physical random access channel (PRACH) transmission is the first to arrive. You can select the target cell as the selected cell.

When performing the RRCReconfiguration procedure with the selected cell, the UE waits until the first PRACH transmission of the selected cell is possible before starting the RRCReconfiguration procedure. In the conventional MBB, some operations of RRCReconfiguration are performed first, and the rest (after MAC reset) is performed immediately before the first PRACH transmission. In the present invention, the entire RRCReconfiguration is performed immediately before the first PRACH transmission.

The terminal continues data transmission/reception with a source PCell (Primary Cell) and a source SCell (Secondary Cell) until the time when the first PRACH transmission of the selected cell becomes possible. When the first PRACH transmission becomes possible, the UE deactivates the source SCells and then releases them. And configure the SCells of the RRCReconfiguration message of the selected Cell, and set the initial state to either active or deactivated.

For the above operation, the terminal should apply the default BCCH configuration to candidate cells satisfying a predetermined condition and obtain MIB in advance. A predetermined condition is that the UE needs to know the SFN of the candidate cell in order to determine the PRACH occasion/timing among candidate cells that are likely to become the candidate target cell, but the UE may not know the SFN of the candidate cell. At this time, since it is not necessary to know the SFN, a candidate cell indicated or recognized that the SFN of the source cell and the target cell is the same, or a candidate cell whose PRACH periodicity is within a predetermined value (eg, 10 ms) does not need to know the SFN. is excluded from the cell that needs to acquire . In another embodiment, the information (indicator or list of cells) on the cell(s) that do not need to acquire the SFN is explicitly informed to the terminal using a ReconfigurationWithSync field or an RRCReconfiguraiton message including the field. . Alternatively, the SFN information of the candidate target cells may be explicitly informed to the UE using the ReconfigurationWithSync field or an RRCReconfiguraiton message including the field. In this case, the SFN information may be expressed as absolute time information or offset information with the SFN timing of the source cell.

On the other hand, the UE may have previously acquired whether the SFN timing of the source cell matches the SFN timing of the adjacent cells within a predetermined error or difference through predetermined system information or a dedicated RRC process. For example, the deriveSSB-IndexFromCell field provided through SIB2 and SIB4 broadcast by the base station may be used to determine whether the SFN of a source cell matches the SFN of cells of a serving frequency or an adjacent frequency. Through this information, the terminal can determine whether to receive the MIB from the candidate target cell.

The terminal transmits the provided preamble to the selected cell (1f-75). If the dedicated preamble is not provided, one of the preambles used in the contention base is transmitted. Upon receiving the preamble, the target cell transmits a random access response message (RAR) to the UE (1f-80). The UE transmits msg3 to the target cell using the UL grant information contained in the RAR (1f-85). The msg3 contains an RRCConnectionReconfigurationComplete message in the case of an LTE system and an RRCReconfigurationComplete message in the case of an NR system. When the random access process is successfully completed, it is considered that the second handover has been successfully completed, and the running T304 timer is stopped. If the second handover is not successfully completed until the T304 timer expires, it is regarded as a handover failure.

When the handover is successfully completed, the terminal deletes the handover configuration information. When the source cell receives the handover success report from the target cell, it deletes the context information of the terminal. The success or failure can also be determined by the UE context release message, which is an inter-node message transmitted to the target cell to the source cell. In addition, the source cell instructs other candidate target cells included in the handover configuration information to delete the handover configuration information (or UE context information) (or notifies that it is no longer valid). The candidate target cells may delete the handover configuration information by themselves when a predetermined time elapses after receiving the handover request without an instruction from the source cell.

1G is a flowchart of a terminal operation for minimizing data transmission interruption time in condition-based handover.

In step 1g-05, the terminal reports the cell measurement result to the base station according to the configuration from the base station.

In step 1g-10, the terminal receives an RRCReconfiguration message containing the ReconfigurationWithSync field from the base station. The field is used to indicate to the terminal to perform the first handover or the second handover.

In step 1g-15, the terminal determines whether the ReconfigurationWithSync includes first handover-related configuration information or second handover-related configuration information.

In step 1g-20, if the field includes the first handover-related configuration information, the terminal considers the PCI of the frequency indicated in ReconfigurationWithSync as the target cell.

In step 1g-25, the terminal stops data transmission and reception with the source PCell and deactivates the source SCells.

In step 1g-30, upon receiving the ReconfigurationWithSync field, the terminal starts T304 and resets the MAC.

In step 1g-35, the terminal determines the PRACH occasion through the PRACH config information of ServingCellConfigCommon stored in the ReconfigurationWithSync field.

In step 1g-40, the UE transmits a preamble to the first PRACH occasion among the PRACH occasions.

If the UE successfully transmits the RRCReconfigurationComplete message to the target cell through random access in step 1g-45, it is considered that the handover procedure has been successfully completed.

In step 1g-50, if the field includes the second handover-related configuration information, the terminal checks whether the condition of the associated MeasId is satisfied through measurement of candidate cells. At this time, unlike the case of the first handover, even if the ReconfigurationWithSync field is received, T304 is not started, and MAC reset is not performed.

In step 1g-55, the terminal considers candidate cells satisfying the condition as candidate target cells.

In step 1g-60, the UE acquires the MIB after applying the default BCCH configuration to candidate cells that satisfy a predetermined condition. A cell belonging to a predetermined condition may mean a cell that the UE does not yet know of PRACH timing information from among cells with a high possibility of becoming a candidate target cell (eg, TimeToTrigger is initiated).

In step 1g-65, when at least one candidate target cell is generated, the terminal performs a selected cell determination procedure. For example, the following procedure may be performed.

- If there is only one candidate target cell, candidate target cell = selected cell

- If there are more than one candidate target cell, candidate target cell satisfying a predetermined condition = selected cell

- Among the candidate target cells, the candidate target cell in which the first PRACH occasion occurs first = selected cell

In step 1g-70, the terminal determines the PRACH occasion that arrives first in the selected cell.

In step 1g-75, the terminal continues data transmission/reception with the source PCell and source SCells until a predetermined time point, and then performs the operation of step 1g-80 when the predetermined time point arrives. The predetermined time point may be a time point at which the first PRACH occasion of the selected cell occurs.

In step 1g-80, the UE transmits a preamble on the PRACH occasion. At this time, the terminal performs the following operations.

- Consider selected cell as target PCell

- deactivate source SCells

- T304 start

- MAC reset

- Preamble transmission on the first PRACH occasion

- Set target SCell according to SCellToAddMod signaled with selected cell

If the UE successfully transmits the RRCReconfigurationComplete message to the target cell through random access in step 1g-85, it is considered that the handover procedure has been successfully completed.

The UE determines whether it is a first handover or a second handover according to the type of configuration information included in the RRCReconfiguration message.

- When the RRCReconfiguration message includes CellGroupConfig for MCG and ReconfigWithSync is included in the CellGroupConfig, a message indicating the first handover

- When the RRCReconfiguration message includes several RRCReconfiguration messages in the form of a container, and each RRCReconfiguration message includes ReconfigWithSync for a candidate cell, a message indicating a second handover

The second handover is a handover method in which one or several candidate cells are determined as a candidate target cell, and one of several candidate target cells is determined as a selected cell to perform handover. At this time, the candidate target cell is determined from the candidate cell based on MeasId, the selected cell is determined from the candidate target cell, and when the selected cell determines when to transmit the preamble, it is based on the RACH-ConfigCommon included in the RRCReconfiguration container for the cell. to decide

1h shows the structure of the terminal.

Referring to the drawings, the terminal includes a radio frequency (RF) processing unit 1h-10, a baseband processing unit 1h-20, a storage unit 1h-30, and a control unit 1h-40. .

The RF processing unit 1h-10 performs a function for transmitting and receiving a signal through a wireless channel, such as band conversion and amplification of the signal. That is, the RF processing unit 1h-10 up-converts the baseband signal provided from the baseband processing unit 1h-20 into an RF band signal, transmits it through an antenna, and receives an RF band signal received through the antenna. down-converts to a baseband signal. For example, the RF processing unit 1h-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. can In the figure, only one antenna is shown, but the terminal may include a plurality of antennas. Also, the RF processing unit 1h-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1h-10 may perform beamforming. For the beamforming, the RF processing unit 1h-10 may adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit may perform MIMO, and may receive multiple layers when performing MIMO operation.

The baseband processing unit 1h-20 performs a function of converting between a baseband signal and a bit stream according to a physical layer standard of the system. For example, when transmitting data, the baseband processing unit 1h-20 generates complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 1h-20 restores the received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 1h-10. For example, when transmitting data according to an orthogonal frequency division multiplexing (OFDM) scheme, the baseband processing unit 1h-20 encodes and modulates a transmission bit stream to generate complex symbols, and convert the complex symbols to subcarriers. After mapping to , OFDM symbols are constructed through inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. In addition, upon data reception, the baseband processing unit 1h-20 divides the baseband signal provided from the RF processing unit 1h-10 into OFDM symbol units, and sends them to subcarriers through a fast Fourier transform (FFT) operation. After reconstructing the mapped signals, the received bit stream is reconstructed through demodulation and decoding.

The baseband processing unit 1h-20 and the RF processing unit 1h-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1h-20 and the RF processing unit 1h-10 may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit 1h-20 and the RF processing unit 1h-10 may include a plurality of communication modules to support a plurality of different radio access technologies. In addition, at least one of the baseband processing unit 1h-20 and the RF processing unit 1h-10 may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (eg, IEEE 802.11), a cellular network (eg, LTE), and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.NRHz, NRhz) band and a millimeter wave (eg, 60GHz) band.

The storage unit 1h-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit 1h-30 may store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit 1h-30 provides stored data according to the request of the control unit 1h-40.

The controller 1h-40 controls overall operations of the terminal. For example, the control unit 1h-40 transmits and receives signals through the baseband processing unit 1h-20 and the RF processing unit 1h-10. In addition, the control unit 1h-40 writes and reads data in the storage unit 1h-40. To this end, the controller 1h-40 may include at least one processor. For example, the controller 1h-40 may include a communication processor (CP) that controls for communication and an application processor (AP) that controls an upper layer such as an application program. The control unit 1-40 may include the multi-connection processing unit 1h-42.

1I shows a block configuration of a main base station in a wireless communication system according to an embodiment of the present invention.

As shown in the figure, the base station includes an RF processing unit 1i-10, a baseband processing unit 1i-20, a backhaul communication unit 1i-30, a storage unit 1i-40, and a control unit 1i-50. is comprised of

The RF processing unit 1i-10 performs a function for transmitting and receiving a signal through a wireless channel, such as band conversion and amplification of the signal. That is, the RF processing unit 1i-10 up-converts the baseband signal provided from the baseband processing unit 1i-20 into an RF band signal, transmits it through an antenna, and receives an RF band signal received through the antenna. is downconverted to a baseband signal. For example, the RF processing unit 1i-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. Although only one antenna is shown in the drawing, the first access node may include a plurality of antennas. Also, the RF processing unit 1i-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1i-10 may perform beamforming. For the beamforming, the RF processing unit 1i-10 may adjust the phase and magnitude of each of signals transmitted and received through a plurality of antennas or antenna elements. The RF processing unit may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1i-20 performs a function of converting a baseband signal and a bit stream according to the physical layer standard of the first radio access technology. For example, when transmitting data, the baseband processing unit 1i-20 generates complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 1i-20 restores the received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 1i-10. For example, in the OFDM scheme, when transmitting data, the baseband processing unit 1i-20 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then IFFT OFDM symbols are constructed through operation and CP insertion. Also, upon data reception, the baseband processing unit 1i-20 divides the baseband signal provided from the RF processing unit 1i-10 into OFDM symbol units, and restores signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 1i-20 and the RF processing unit 1i-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1i-20 and the RF processing unit 1i-10 may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

The backhaul communication unit 1i-30 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 1i-30 converts a bit string transmitted from the main base station to another node, for example, an auxiliary base station, a core network, etc. into a physical signal, and converts the physical signal received from the other node into a bit convert to heat

The storage unit 1i-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 1i-40 may store information on a bearer allocated to an accessed terminal, a measurement result reported from the accessed terminal, and the like. In addition, the storage unit 1i-40 may store information serving as a criterion for determining whether to provide or stop multiple connections to the terminal. In addition, the storage unit 1i-40 provides the stored data according to the request of the control unit 1i-50.

The controller 1i-50 controls overall operations of the main station. For example, the control unit 1i-50 transmits and receives signals through the baseband processing unit 1i-20 and the RF processing unit 1i-10 or through the backhaul communication unit 1i-30. In addition, the control unit 1i-50 writes and reads data in the storage unit 1i-40. To this end, the control unit 1i-50 may include at least one processor. The control unit 1i-50 may include the multi-connection processing unit 1i-52.

Embodiments of the present invention disclosed in the present specification and drawings are merely provided for specific examples in order to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (1)

A control signal processing method in a wireless communication system, comprising:
Receiving a first control signal transmitted from the 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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