KR20210124868A - Method and apparatus to set rlf report in the mobile communication - Google Patents

Abstract

The present invention relates to a communication technique that combines a 5^th generation (5G) or pre-5G communication system with an IoT technology to support higher data rates after a 4^th generation (4G) communication system such as long term evolution (LTE) and a system thereof. The present invention can be applied to intelligent services (eg, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety related services, etc.) based on a 5G communication technology and an IoT-related technology. According to various embodiments of the present invention, disclosed are a method for configuring wireless link failure information in a mobile communication system and a device thereof.

Description

METHOD AND APPARATUS TO SET RLF REPORT IN THE MOBILE COMMUNICATION

The present invention relates to the operation of a terminal and a base station in a mobile communication system.

Efforts are being made to develop an improved 5th generation (5G) communication system or a pre-5G communication system in order to meet the increasing demand for wireless data traffic after commercialization of the 4G (4th generation) communication system. For this reason, the 5G communication system or the pre-5G communication system is called a 4G network after (Beyond 4G Network) communication system or an LTE (Long Term Evolution) system after (Post LTE) system.

In order to achieve high data rates, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands (eg, 60 gigabytes (60 GHz) bands). In order to alleviate 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), an ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and reception interference cancellation Technology development is underway.

In addition, in the 5G system, Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), which are advanced coding modulation (Advanced Coding Modulation, ACM) methods, and Filter Bank Multi Carrier (FBMC), an advanced access technology, ), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are being developed.

The 5G system is considering support for various services compared to the existing 4G system. For example, the most representative services are enhanced mobile broadband (eMBB), ultra-reliable and low latency communication (URLLC), and massive device-to-device communication service (mMTC). machine type communication), next-generation broadcast service (eMBMS: evolved multimedia broadcast/multicast Service), and the like. In addition, the system providing the URLLC service may be referred to as a URLLC system, and the system providing the eMBB service may be referred to as an eMBB system. Also, the terms service and system may be used interchangeably.

Among them, the URLLC service is a service newly considered in the 5G system, unlike the existing 4G system, and has ultra-high reliability (eg, about 10-5 packet error rate) and low latency (eg, about 0.5 msec) requirement to be satisfied. In order to satisfy such strict requirements, the URLLC service may need to apply a shorter transmission time interval (TTI) than the eMBB service, and various operating methods are being considered using this.

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, technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication) are implemented by 5G communication technologies such as beamforming, MIMO, and array antenna. will be. The application of a cloud radio access network (cloud RAN) as the big data processing technology described above is an example of the convergence of 5G technology and IoT technology.

In the present invention, in a next-generation mobile communication system using a beam, in particular, when a terminal and a base station measure signal strength of a serving cell and neighboring cells and want to obtain location information, only in RRC connected mode (RRC_CONNECTED) and standby mode (RRC_IDLE) Rather, an object of the present invention is to provide a method for transmitting and receiving an RRC message even in an inactive radio access state (RRC_INACTIVE).

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be able

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, by newly defining the RRC_Inactive radio access state in the next-generation mobile communication system using a beam, and applying a radio link monitoring (RLM) operation and a radio link failure (RLF) operation, the terminal and the base station Signal strengths of the serving cell and neighboring cells may be measured and location information may be obtained.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present disclosure belongs from the description below. will be.

1A is a diagram illustrating a structure of a next-generation mobile communication system according to an embodiment of the present invention.
1B is a diagram for explaining a wireless access state transition in a next-generation mobile communication system according to an embodiment of the present invention.
1C is a view for explaining a technique for collecting and reporting cell measurement information according to an embodiment of the present invention.
1D is a diagram illustrating a method of collecting and reporting cell measurement information according to an embodiment of the present invention.
1E is a flowchart of an operation for collecting and reporting cell measurement information according to an embodiment of the present invention.
1F is a diagram for explaining an operation of Radio Link Monitoring (RLM) according to an embodiment of the present invention.
1G is a diagram for explaining a Radio Link Failure (RLF) operation and an RLF report according to an embodiment of the present invention.
1H is a diagram for explaining a random access (RA) report according to an embodiment of the present invention.
1I is a flowchart of a process in which RLF is generated due to handover failure according to an embodiment of the present invention.
1j is a flowchart of an operation of a terminal configuring RLF report information according to an embodiment of the present invention.
1K is a block diagram illustrating an internal structure of a terminal applied according to an embodiment of the present invention.
11 is a block diagram illustrating a configuration of a base station according to an embodiment of the present invention.
1M is a flowchart of an operation of a terminal processing RLF report information according to an embodiment of the present invention.

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.

1A is a diagram illustrating a structure of a next-generation mobile communication system according to an embodiment of the present invention.

Referring to Figure 1a, the radio access network of the next-generation mobile communication system (new radio, NR) is a next-generation base station (new radio node B, hereinafter gNB) (1a-10) and AMF (1a-05, new radio core network) can be configured. A user terminal (new radio user equipment, hereinafter NR UE or terminal, terminal) 1a-15 accesses an external network through gNB 1a-10 and AMF 1a-05.

In FIG. 1A , gNBs 1a - 10 correspond to evolved node b (eNB) of the existing LTE system. The gNB (1a-10) is connected to the NR UE through a radio channel and can provide a service superior to that of the existing Node B (1a-20). 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 1a-10 typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to existing LTE, it can have more than the existing maximum bandwidth, and additional beamforming technology can be grafted using orthogonal frequency division multiplexing (OFDM) as a radio access technology. . In addition, an adaptive modulation & coding (AMC) method 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. The AMF (1a-05) is a device in charge of various control functions as well as a mobility management function 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 (1a-05) is connected to the MME (1a-25) through a network interface. The MME is connected to the existing base station eNB (1a-30). A UE supporting LTE-NR Dual Connectivity may transmit and receive data while maintaining a connection to not only the gNB 1a-20 but also the eNB 1a-30 (1a-35).

1B is a diagram for explaining a wireless access state transition in a next-generation mobile communication system according to an embodiment of the present invention.

The next-generation mobile communication system has three radio connection states (RRC states). The connected mode (RRC_CONNECTED, 1b-05) is a wireless connection state in which the terminal can transmit and receive data. The standby mode (RRC_IDLE, 1b-30) is a radio access state in which the terminal monitors whether paging is transmitted to itself. The two modes are radio access states that are also applied to the existing LTE system, and the detailed technology is the same as that of the existing LTE system. In the next-generation mobile communication system, a new inactive (RRC_INACTIVE) radio connection state 1b-15 is defined. In the radio access state, the UE context is maintained in the base station and the terminal, and RAN-based paging is supported. The characteristics of the new wireless connection state are listed below.

- Cell re-selection mobility;

- CN - NR RAN connection (both C/U-planes) has been established for UE;

- The UE AS context is stored in at least one gNB and the UE;

- Paging is initiated by NR RAN;

- RAN-based notification area is managed by NR RAN;

- NR RAN knows the RAN-based notification area which the UE belongs to;

The new INACTIVE radio access state may transition to a connected mode or a standby mode using a specific procedure. According to the resume process, the INACTIVE mode is converted to the connected mode, and the connected mode is converted to the INACTIVE mode by using the Release procedure including the suspend setting information (1b-10). The above procedure transmits and receives one or more RRC messages between the terminal and the base station, and consists of one or more steps. Also, it is possible to switch from INACTIVE mode to standby mode through the Release procedure after Resume (1b-20). Switching between connected mode and standby mode follows the existing LTE technology. That is, through an establishment or release procedure, the mode is switched (1b-25).

1C is a view for explaining a technique for collecting and reporting cell measurement information according to an embodiment of the present invention.

When constructing or optimizing a network, a mobile communication service provider usually measures the signal strength in an expected service area, and then goes through a process of arranging or re-adjusting base stations in the service area based on this. The operator loads the signal measurement equipment on the vehicle and collects the cell measurement information in the service area, which requires a lot of time and money. The process is commonly referred to as a drive test by using a vehicle (1c-30). In order to support operations such as cell reselection, handover, and serving cell addition, the terminal is equipped with a function of measuring a signal with a base station when moving between cells (1c-25). Therefore, instead of the drive test, a terminal in the service area can be used, which is called minimization of drive test (MDT). The operator can set the MDT operation to specific terminals through various components of the network, and the terminals are in the connected mode (RRC_Connected), the standby mode (RRC_Idle) or the inactive mode (RRC_Inactive). Signals from the serving cell and neighboring cells Collect and store century information. In addition, various information such as location information, time information, and signal quality information is also stored. The stored information may be reported to the network when the terminals are in the connected mode, and the information is transmitted to a specific server.

The MDT operation is largely classified into immediate MDT and logged MDT.

Immediate MDT is characterized by reporting the collected information directly to the network. Since it needs to be reported immediately, only the connected mode terminal can perform this. In general, the RRM measurement process for supporting operations such as handover and serving cell addition is recycled, and location information and time information are additionally reported.

Logged MDT stores the collected information without directly reporting it to the network, and after the terminal switches to the connected mode, it is characterized in that it reports the stored information. Usually, a terminal in standby mode that cannot directly report to the network performs this. The terminal in the inactive mode introduced in the next-generation mobile communication system performs Logged MDT. When a specific terminal is in a connected mode, the network provides configuration information for performing a Logged MDT operation to the terminal, and after the terminal switches to a standby mode or an inactive mode, the configured information is collected and stored.

The following [Table 1] describes the RRC state according to the MDT operation.

MDT action RRC state Immediate MDT RRC_Connected Logged MDT RRC_Idle, RRC_Inactive

1D is a diagram illustrating a method of collecting and reporting cell measurement information according to an embodiment of the present invention.

The terminal 1d-05 switches from the standby mode or the inactive mode 1d-10 to the connected mode 1d-15. In the connected mode (1d-15), through an immediate MDT operation, MDT data is collected and reported to the base station. The terminal switched to the connected mode is provided with Logged MDT configuration information performed in the standby mode or the inactive mode from the base station (1d-20). The configuration information receives a predetermined RRC message and is transmitted to the terminal, and the terminal, which receives the message, starts a first timer (1d-55). The terminal performs the Logged MDT operation in the standby mode or inactive mode period until the first timer expires. The value of the first timer is included in the Logged MDT configuration information. When the terminal switches to the standby mode or the inactive mode, it performs Logged MDT according to the received configuration information (1d-25). The terminal stores predetermined information collected at each set period and logging interval (1d-35) (1d-30, 1d-45). In addition, if valid location information 1d-40 has been collected, the information should also be stored. The validity of the location information is determined to be valid when a predetermined time (1d-50) has elapsed after the information is collected. The predetermined time is shorter than or equal to the logged interval. Even before the first timer expires, the terminal temporarily suspends the logged MDT operation being performed when switching to the connected mode (1d-60). However, the first timer does not stop even in the connected mode section, but continues to be driven (1d-55). That is, the first timer is continuously driven regardless of the change in the RRC state. However, when the terminal memory for storing MDT data is insufficient, when it cannot be stored anymore, or when the Logged MDT setting information is released, the first timer is stopped. The case in which the Logged MDT configuration information is released is when other Logged MDT configuration information is provided from a serving RAT or another RAT, or when the terminal is detached or power is cut off. During the connection establishment process (RRC connection establishment) or the connection restart process (RRC connection resume), the terminal uses the RRC Setup Complete message or the RRC Resume Complete message to determine that it has the collection information (MDT data) it stores. report to (1d-65).

The connection establishment process is a process in which the terminal switches from the standby mode to the connected mode. As follows, it is usually composed of a process of three steps, and three types of RRC messages are used.

- Step 1: The terminal transmits an RRC Setup Request message to the base station

- Step 2: The base station transmits the RRC Setup message to the terminal

- Step 3: The terminal transmits the RRC Setup Complete message to the base station

The connection restart process is a process in which the terminal switches from an inactive mode to a connected mode. As follows, it is usually composed of a process of three steps, and three types of RRC messages are used.

- Step 1: The terminal transmits an RRC Resume Request message to the base station

- Step 2: The base station transmits an RRC Resume message to the terminal

- Step 3: The UE transmits the RRC Resume Complete message to the base station

The information indicating that the terminal has the collection information is reported to the target base station during the RRC connection reestablishment and handover processes in addition to the connection establishment process or the connection restart process. If the Logged MDT is set, but there is no collected and stored information yet, the report is omitted. The base station receiving the report may request a report of the MDT data stored by the terminal when necessary. The unreported MDT data must be continuously stored by the terminal for a predetermined time. If the terminal is switched back to the standby mode or the inactive mode, and the first timer has not yet expired, the Logged MDT operation is restarted again (1d-70). If the first timer expires, the Logged MDT operation is stopped (1d-75). The terminal, which has stopped the operation, drives a second timer (1d-80), and maintains the stored MDT data until the timer expires. After the timer expires, whether to delete the MDT data being stored is determined by the terminal implementation. The value of the second timer is included in the Logged MDT configuration information, or a predefined value is not set. When the terminal switches to the connected mode again, it reports to the base station that it has the collection information (MDT data) it stores (1d-85). This time, the base station uses a predetermined RRC message to request a report of the MDT data stored by the terminal (1d-90). Accordingly, the terminal receives the MDT data being stored in a predetermined RRC message, and reports the message to the base station (1d-95).

1E is a flowchart of an operation for collecting and reporting cell measurement information according to an embodiment of the present invention.

The terminal 1e-05 establishes a connection with the base station 1e-10 (1e-15). The terminal provides terminal capability information to the base station (1e-20), and may indicate whether it supports the MDT operation and whether it can measure what frequency. The base station receives the configuration information necessary for performing the Logged MDT operation in a predetermined RRC message and transmits it to the terminal (1e-25). For example, the setting information includes at least one of the following information.

- About Trace Reference

- About Trace Recording Session Reference

- Trace collection entity (TCE) ID information: The base station transmits the MDT data information reported from the terminal to the data server designated by the TCE ID.

- Absolute time information (absolute time): Absolute time in the current cell providing Logged MDT configuration information

- Area Configuration: Through the Logged MDT operation, it is indicated in units of cells as area information that can collect and store measurement information. It may also include RAT information for which measurement information should be collected. The list included in the RAT information is a black list or a white list. If it is a black list, cell measurement information is collected for RATs not included in the list. If it is a white list, cell measurement information is not collected for RATs not included in the list.

- Logging Duration: As the value of the first timer, when the timer is running, a Logged MDT operation is performed in a standby mode or an inactive mode.

- Logging Interval: It is the interval for saving the collected information.

- plmn-IdentityList (i.e. MDT PLMN list): PLMN list information, and stores PLMN information capable of not only performing the Logged MDT operation, but also reporting whether to store MDT data and report MDT data.

- An indicator indicating whether to perform Logged MDT operation in standby mode, inactive mode, or both. The indicator may indicate the RRC state for performing the Logged MDT operation, or without the indicator, it may be defined to always perform the Logged MDT operation in the standby mode and the inactive mode. The UE performs the Logged MDT operation only in the RRC state indicated by the indicator.

- An indicator indicating whether to collect and store beam level measurement information. A beam antenna may be applied in a next-generation mobile communication system. Without the indicator, it may be defined that beam level measurement information is always collected and stored for a frequency at which a beam-based operation is performed.

- Information on the maximum number of beams to be collected or stored, and information about the minimum signal strength of a beam to be stored. The terminal omits the storage of information on a beam weaker than the minimum signal strength. If all the beams are weaker than the set minimum signal value, the terminal may store one beam information having the strongest signal strength among them, or may include an indicator that all beams are weaker than the set minimum signal value.

- An indicator indicating whether the MDT retrieval action can be triggered in the two-step restart process (RRC resume).

Upon receiving the Logged MDT configuration information, the terminal drives a first timer (1e-30). The value of the first timer is set equal to the value of the Logging Duration. The base station uses the RRC Release message to switch the terminal to the standby mode or the inactive mode (1e-35). Depending on which RRC state is switched to, the RRC Release message contains configuration information for operation in the RRC state. If the first timer is running, the terminal performs Logged MDT in standby mode or inactive mode (1e-40). Signal strength of the serving cell and neighboring cells is measured, and location information is obtained. When the beam level measurement is set, a signal strength value for a beam greater than the set minimum value is collected and stored in the serving cell and the adjacent cell. The maximum number of beams that can be stored is set or predefined. The signal strength means RSRP or RSRQ or SINR. The collected information is stored at each Logged Interval period. Each log information stored for each period includes an indicator indicating whether the stored information is collected in the standby mode or in the inactive mode. Alternatively, the indicator may be included in every first log in which the mode is switched. This can minimize signaling overhead due to the indicator. When the first timer expires (1e-45), the Logged MDT operation is stopped (1e-50).

If the terminal is in standby mode or inactive mode by the RRC Release message, receives RAN or CN paging from the base station, or MO data transmission is activated, the terminal moves from standby mode or inactive mode to connected mode Initializes the establishment process or resume process for conversion.

The establishment process or the resume process is

- Step 1: The UE transmits an RRC Setup Request message or RRC Resume Request message to the base station (1e-55)

- Step 2: BS transmits RRC Setup message or RRC Resume message to UE (1e-60)

- Step 3: UE transmits RRC Setup Complete message or RRC Resume Complete message to the base station (1e-65)

can be composed of The terminal accommodates an indicator indicating whether there is MDT data stored therein in the RRC Setup Complete or RRC Resume Complete message. Upon receiving the RRC Setup Complete message, the base station requests a report of the MDT data by using a predetermined RRC message (1e-70). Upon receiving the request, the UE reports the MDT data using a predetermined RRC message (1e-75).

1F is a diagram for explaining a radio link monitoring (RLM) operation according to an embodiment of the present invention.

The UE physical layer measures the downlink signal quality from the CRS of the serving cell (1f-05). It is determined whether the signal quality is lower than a specific threshold Qout (1f-10). The threshold is a signal quality value corresponding to a specific BLER measured in the PDCCH. If the signal quality is lower than a specific threshold Qout, the physical layer transmits an 'out-of-sync' indicator to a higher layer. In LTE technology, this operation is called RLM. If the indicator is delivered to the upper layer more than a certain number of times, the upper layer drives a specific timer, and when the timer expires, declares an RLF (1f-15).

1G is a diagram for explaining a radio link failure (RLF) operation according to an embodiment of the present invention.

As previously explained, RLFs can be declared according to the results from the RLM. The UE physical layer determines whether the downlink signal quality is lower than a specific threshold Qout from the CRS of the serving cell every specific period, Qout evaluation period. If the signal quality is lower than a specific threshold Qout, the physical layer transmits an 'out-of-sync' indicator to a higher layer. After the minimum indicator is delivered to the upper layer (1g-05), when a specific number of times N310 is delivered to the upper layer, a specific timer T310 is driven (1g-10). The physical layer also determines whether the downlink signal quality is higher than a specific threshold Qin from the CRS of the serving cell. If the signal quality is higher than a specific threshold Qin, the physical layer transmits an 'in-sync' indicator to a higher layer. When the indicator is transmitted to the upper layer a specific number of times, the running T310 timer is stopped. If the T310 timer is not stopped and expires, the upper layer declares an RLF (1g-15). After the RLF declaration, the terminal drives another timer T311. The terminal searches for a new suitable cell, and if it does not find it until the T311 expires, it switches to a standby mode (1g-25). If a new suitable cell is found before the timer expires, the T301 timer is driven and a re-establishment process is performed with the cell (1g-20). If the re-establishment is not successfully completed before the T301 timer expires, the terminal switches to the standby mode (1g-30). If the re-establishment is successful, the terminal continues the connected mode in the cell. The RLF may be declared by the RLM operation, and may be declared according to another condition. Even when random access fails, RLF may be declared (1g-35). In addition, even if the maximum number of retransmissions is reached in the RLC layer, even if the packet is not successfully delivered, RLF is declared (1g-40).

The following [Table 2] is a description of the T301 and T311 operations.

Timer Start Stop At expiry T301 Upon transmission of RRCReestabilshmentRequest Upon reception of RRCReestablishment or RRCSetup message as well as when the selected cell becomes unsuitable Go to RRC_IDLE T311 Upon initiating the RRC connection re-establishment procedure Upon selection of a suitable NR cell or a cell using another RAT. Enter RRC_IDLE

Another case in which RLF is declared is when handover fails. When the terminal receives the RRCConnectionReconfiguration message including the handover configuration information and the mobilityControlInfo IE (1g-45), the terminal drives the T304 timer. The timer value of T304 is provided in the mobilityControlInfo. If the random access with the target cell is not successfully completed before the timer expires, it is regarded as a handover failure and RLF is declared (1g-50).

Predetermined information collected when RLF occurs in the UE is useful for optimizing the cell area. Accordingly, such information is stored by the terminal when RLF occurs, and then reported to the base station when the terminal is successfully switched to the connected mode. The report is called an RLF report, and the predetermined information reported at this time is as follows. At this time, information related to the random access process is also stored.

- plmn-IdentityList

- measResultLastServCell

- measResultNeighCells

- locationInfo

- failedPCellId

- previousPCellId

- timeConnFailure

- C-RNTI used in the source PCell

- connectionFailureType

- absoluteFrequencyPointA: absolute frequency position of the reference resource block (Common RB 0)

- locationAndBandwidth: Frequency domain location and bandwidth of the bandwidth part associated to the random-access resources used by the UE

- subcarrierSpacing: Subcarrier spacing used in the BWP associated to the random-access resources used by the UE

- msg1-FrequencyStart: Offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0 of the UL BWP

- msg1-SubcarrierSpacing: Subcarrier spacing of PRACH resources

- msg1-FDM: The number of PRACH transmission occasions FDMed in one time instance

- raPurpose: the RA scenario for which the RA report entry is triggered

- perRAInfoList: detailed information about each of the random access attempts in the chronological order of the random access attempts, for example, the SSB index related to preamble transmission, the number of preamble transmissions per SSB, whether contention occurs, etc.

When the terminal switches to the connected mode through the RRC establishment or RRC resume process, it reports to the base station that the RLF report is being stored using a predetermined RRC message such as an RRCSetupComplete or RRCResumeComplete message (1g-55). The base station instructs the terminal to report the RLF report by using the UEInformationRequest message (1g-60). The terminal reports the UEInformationResponse message that receives the RLF report to the base station (1g-65).

1H is a diagram for explaining a random access (RA) report according to an embodiment of the present invention.

The terminal stores information related to the random access in a terminal internal variable VarRA-Report for a successfully completed random access (1h-05). This is called one RA report. The information is as follows.

- CellId: CGI of the cell in which the associated random access procedure was performed

- absoluteFrequencyPointA: absolute frequency position of the reference resource block (Common RB 0)

- locationAndBandwidth: Frequency domain location and bandwidth of the bandwidth part associated to the random-access resources used by the UE

- subcarrierSpacing: Subcarrier spacing used in the BWP associated to the random-access resources used by the UE

- msg1-FrequencyStart: Offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0 of the UL BWP

- msg1-SubcarrierSpacing: Subcarrier spacing of PRACH resources

- msg1-FDM: The number of PRACH transmission occasions FDMed in one time instance

- raPurpose: the RA scenario for which the RA report entry is triggered

- perRAInfoList: detailed information about each of the random access attempts in the chronological order of the random access attempts

In addition, when storing the information, the terminal stores the EPLMN list if there is stored EPLMN information, otherwise, the selected PLMN information is stored together.

If another random access process succeeds after storing the RA information, information related to the random access is stored (1h-10). At this time, if the RPLMN is included in the stored PLMN information, it is updated and stored with the currently stored EPLMN information. If the RPLMN is not included in the stored PLMN information, all information stored in the VarRA-Report is deleted.

The terminal can store up to 8 RA reports. Eight RA reports are already stored. When a new random access process is successfully completed, the first stored RA report is deleted and information related to the random access process is stored (1h-15).

After the terminal is switched to the connected mode, the base station may request the stored RA report information using a predetermined RRC message (1h-20). At this time, if the terminal stores the RA report and the RPLMN is included in the stored PLMN information, the terminal reports the stored RA report to the base station using a predetermined RRC message (1h-25). All of the reported RA report information is deleted from the VarRA-Report.

1I is a flowchart of a process in which RLF is generated due to handover failure according to an embodiment of the present invention.

The terminal 1i-05 receives a predetermined RRC message including measurement configuration information from the source cell 1i-10 (1i-25). The terminal measures the signal quality of the serving 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 (1i-30) ( 1i-35). The source cell determines whether to trigger a handover operation based on the reported cell measurement information (1i-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 handover. If it is decided to trigger the handover, the source cell requests the handover to one target cell 1i-20 through a predetermined inter-node message (1i-45). Upon receiving the request, the target cell accepts the request, and transmits handover configuration information necessary for the handover operation to the source cell (1i-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 (Ii-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, C-RNTI information used in the target cell, etc. do.

Upon receiving the handover configuration information, the terminal immediately performs a random access process to the target cell and drives a T304 timer (1i-60). The terminal transmits the received preamble (1i-65). 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 (RAR) message to the UE. The UE transmits msg3 to the target cell using the UL grant information contained in the RAR. 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 handover has been successfully completed, and the running T304 timer is stopped. If the handover is not successfully completed until the T304 timer expires, it is regarded as a handover failure and RLF is declared (1i-70).

The terminal stores valid information for the RLF report according to the expiration of T304 (1i-75). Stores information related to random access that the terminal most recently attempted through uplink of the target cell. More specifically, the frequency information of the reference resource block related to the RA resource in the target cell uplink, absoluteFrequencyPointA is stored, and locationAndBandwidth related to the RA resouce in the most recent active uplink BWP of the target cell and Stores subcarrierSpacing, and stores msg1-FrequencyStart, msg1-SubcarrierSpacing, and msg1-FDM in the most recent active uplink BWP of the target cell. In addition, ssbRLMConfigBitmap and csi-rsRLMConfigBitmap related to the most recent active BWP of the source cell are stored.

The ssbRLMConfigBitmap and csi-rsRLMConfigBitmap are SSB or CSI-RS related configuration information for performing a radio link monitoring (RLM) operation.

If RLF occurs due to radio link failure rather than the handover failure (T304 expiry), valid information is stored for the RLF report. Stores information related to random access that the terminal most recently attempted through uplink of the source cell. More specifically, it stores frequency information, absoluteFrequencyPointA, of a reference resource block related to RA resource in the source cell uplink, and locationAndBandwidth related to RA resouce in the most recent active uplink BWP of the source cell and Stores subcarrierSpacing, and stores msg1-FrequencyStart, msg1-SubcarrierSpacing, and msg1-FDM in the most recent active uplink BWP of the source cell. In addition, ssbRLMConfigBitmap and csi-rsRLMConfigBitmap related to the most recent active BWP of the source cell are stored.

1j is a flowchart of an operation of a terminal configuring RLF report information according to an embodiment of the present invention.

In step 1j-05, the terminal is in an RRC connection state with the base station.

In step 1j-10, the UE triggers random access for the purpose of handover or synchronization with a serving cell.

In step 1j-15, the terminal does not successfully complete the triggered random access process.

In step 1j-20, the terminal generates RLF for a predetermined cause.

In step 1j-25, the UE determines whether the cause of the generated RLF is T304 expiration (handover failure) or radio link failure.

In step 1j-30, if the RLF occurs due to expiration of T304, the terminal stores frequency information, absoluteFrequencyPointA, of the reference resource block related to the RA resource in the target cell uplink, and the most recent active uplink BWP of the target cell with locationAndBandwidth related to RA resouce in Stores subcarrierSpacing, and stores msg1-FrequencyStart, msg1-SubcarrierSpacing, and msg1-FDM in the most recent active uplink BWP of the target cell. In addition, ssbRLMConfigBitmap and csi-rsRLMConfigBitmap related to the most recent active BWP of the source cell are stored.

In step 1j-35, if RLF occurs due to radio link failure, the UE stores frequency information, absoluteFrequencyPointA, of a reference resource block related to RA resource in the source cell uplink, and the most recent active uplink of the source cell. LocationAndBandwidth and related RA resouce in BWP Stores subcarrierSpacing, and stores msg1-FrequencyStart, msg1-SubcarrierSpacing, and msg1-FDM in the most recent active uplink BWP of the source cell. In addition, ssbRLMConfigBitmap and csi-rsRLMConfigBitmap related to the most recent active BWP of the source cell are stored.

In step 1j-40, the terminal searches for one suitable cell capable of receiving a normal service.

In step 1j-45, the UE performs an RRC (re)establishment operation to make an RRC connection to the cell.

In step 1j-50, the UE transmits an RRCSetupComplete or RRCReestablishmentComplete message including an rlf-InfoAvailable indicator indicating that the RLF report is stored to the cell.

In step 1j-55, the UE receives a UEInformationRequest message including an indicator for requesting a report of the RLF report.

In step 1j-60, the terminal reports a UEInformationResponse message including the stored RLF report to the cell. The terminal deletes the successfully reported RLF report.

1K is a block diagram illustrating an internal structure of a terminal applied according to an embodiment of the present invention.

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

The RF processing unit 1k-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 processor 1k-10 up-converts the baseband signal provided from the baseband processor 1k-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 1k-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 1k-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1k-10 may perform beamforming. For the beamforming, the RF processing unit 1k-10 may adjust the phase and magnitude of each of 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 1k-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 1k-20 generates complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 1k-20 restores a received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 1k-10. For example, in the case of orthogonal frequency division multiplexing (OFDM), when transmitting data, the baseband processing unit 1k-20 encodes and modulates a transmitted 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, when receiving data, the baseband processing unit 1k-20 divides the baseband signal provided from the RF processing unit 1k-10 into OFDM symbol units, and performs a fast Fourier transform (FFT) operation on the subcarriers. After reconstructing the mapped signals, the received bit stream is reconstructed through demodulation and decoding.

The baseband processing unit 1k-20 and the RF processing unit 1k-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1k-20 and the RF processing unit 1k-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 1k-20 and the RF processing unit 1k-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 1k-20 and the RF processing unit 1k-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 1k-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 1k-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 1k-30 provides stored data according to the request of the control unit 1k-40.

The controller 1k-40 controls overall operations of the terminal. For example, the control unit 1k-40 transmits and receives signals through the baseband processing unit 1k-20 and the RF processing unit 1k-10. In addition, the control unit 1k-40 writes and reads data in the storage unit 1k-40. To this end, the control unit 1k-40 may include at least one processor. For example, the controller 1k-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.

11 is a block diagram showing the configuration of a base station according to an embodiment of the present invention.

As shown in the figure, the base station includes an RF processing unit 11-10, a baseband processing unit 11-20, a backhaul communication unit 11-30, a storage unit 11-40, and a control unit 11-50. is comprised of

The RF processing unit 11-10 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 processor 11-10 up-converts the baseband signal provided from the baseband processor 11-20 into an RF band signal, transmits it through an antenna, and receives the RF band signal through the antenna. downconverted to a baseband signal. For example, the RF processing unit 11-10 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 11-10 may include a plurality of RF chains. Furthermore, the RF processing unit 11-10 may perform beamforming. For the beamforming, the RF processing unit 11-10 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 11-20 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 11-20 generates complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 11-20 restores a received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 11-10. For example, in the OFDM scheme, when transmitting data, the baseband processing unit 11-20 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. In addition, upon data reception, the baseband processing unit 11-20 divides the baseband signal provided from the RF processing unit 11-10 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 11-20 and the RF processing unit 11-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 11-20 and the RF processing unit 11-10 may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

The backhaul communication unit 11-30 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 11-30 converts a bit string transmitted from the 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 string. convert to

The storage unit 11-40 stores data such as a basic program, an application program, and setting information for the operation of the base station. In particular, the storage unit 11-40 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 11-40 may store information serving as a criterion for determining whether to provide or stop multiple connections to the terminal. In addition, the storage unit 11-40 provides the stored data according to the request of the control unit 11-50.

The controller 11-50 controls overall operations of the base station. For example, the control unit 11-50 transmits and receives signals through the baseband processing unit 11-20 and the RF processing unit 11-10 or through the backhaul communication unit 11-30. In addition, the control unit 11-50 writes and reads data in the storage unit 11-40. To this end, the controller 11-50 may include at least one processor.

1M is a flowchart of an operation of a terminal processing RLF report information according to an embodiment of the present invention.

In step 1m-05, the UE declares RLF according to one of the causes described in FIG. 1G.

In step 1m-10, the terminal sets the valid information described in FIG. 1g at the time when the RLF is declared, and stores it.

In step 1m-15, the terminal determines whether access stratum (AS) security is activated.

In step 1m-20, if AS security is not activated, the terminal deletes the stored RLF report. This is to prevent storage of predetermined information in a state in which AS security is not activated, thereby maintaining complementarity.

In step 1m-15, the terminal determines whether a master cell group (MCG) failure recovery operation is triggered by the RLF. If the MCG failure recovery operation is triggered by the RLF, the terminal deletes the stored RLF report in step 1m-20. The MCG failure recovery operation means that a UE configured with dual connectivity (DC) reports the MCG failure through a secondary cell group (SCG) rather than immediately performing a re-establishment operation or switching to a standby mode even when RLF occurs in the MCG. , is a technology that continues to connect the network. If the MCG failure recovery operation is triggered, since the UE can immediately report the problem through the SCG, there is no need to store and report a separate RLF report.

In step 1m-25, if the MCG failure recovery operation is not triggered by the RLF, the terminal maintains the stored RLF report. The terminal attempts reconnection to a suitable cell or switches to a standby mode through a re-establishment operation. If it is switched to the standby mode, a connection may be attempted by performing a setup operation to a predetermined cell.

In step 1m-30, the terminal is connected to one cell.

In step 1m-35, the UE checks the PLMN supported by the cell, and if it is a connectable valid cell, an RRCSetupComplete or RRCReestablishmentComplete message including an availability indicator indicating that the RLF report is stored is transmitted to the cell.

In step 1m-40, the UE receives a UEInformationRequest message including an indicator requesting to report the RLF report from the cell.

In step 1m-45, the UE reports the UEInformationResponse message in which the RLF report is received to the cell.

In another embodiment, the UE first determines whether AS security is activated or whether the MCG failure recovery operation is triggered by the RLF, and if AS security is not activated, or the MCG failure recovery operation is performed according to the RLF If triggered, the operation of constructing and storing the RLF report is not performed.

Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.

Claims (1)

A control signal processing method in a wireless communication system, comprising:
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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