WO2021002632A1 - Method and device for controlling load of small data - Google Patents

Abstract

The present disclosure relates to a method and a device for controlling a load (overload) in a process of small data transmission of an RRC inactive terminal or an RRC idle terminal. An aspect provides a method and a device for controlling a load of small data by a terminal, the method comprising the steps of: triggering small data transmission in an RRC inactive state; transmitting Msg 3 or Msg A including small data to a base station; and receiving Msg 4 or Msg B including information for overload control from the base station.

Description

Load control method and device for small amount of data

The present disclosure relates to a method and apparatus for controlling an overload in a process of transmitting a small amount of data by an RRC INACTIVE terminal or an RRC IDLE terminal.

There are demands for large-capacity data processing, high-speed data processing, and various service demands using wireless terminals in vehicles and industrial sites. As described above, there is a need for a technology for a high-speed and large-capacity communication system capable of processing various scenarios and large-capacity data, such as video, wireless data, and machine-type communication data, beyond simple voice-oriented services. To this end, ITU-R discloses the requirements for adopting the IMT-2020 international standard, and research on next-generation wireless communication technology to meet the requirements of IMT-2020 is in progress.

In particular, 3GPP is conducting research on the LTE-Advanced Pro Rel-15/16 standard and the NR (New Radio Access Technology) standard in parallel to satisfy the IMT-2020 requirements referred to as 5G technology. It plans to receive approval as the next generation wireless communication technology.

Meanwhile, with the development of wireless communication technology, a number of application applications are installed in portable communication terminals and IoT terminals such as smart phones. Many application applications installed in smart phone terminals, MTC terminals, IoT terminals, etc. frequently transmit numerous small data packets. In these cases, the UE must transition to the RRC connected state in order to transmit a small amount of data, which causes signaling overhead as a whole. In addition, in terms of the terminal, it is inefficient because it causes power consumption due to frequent RRC state change procedures.

In particular, even when a procedure for transmitting a small amount of data is simplified, a small amount of data may be frequently transmitted according to the characteristics of an application. In this case, there may be a problem in that the base station load increases due to frequent transmission of small amounts of data. Alternatively, a processing procedure is required when the terminal transmits a small amount of data when the load on the base station is increased by another terminal.

Therefore, there is a need to control the load caused by transmission of a small amount of data.

The present disclosure is intended to propose a method and apparatus for controlling a load when a terminal transmits a small amount of data.

In one aspect, in a method for controlling a small amount of data load by a terminal, triggering a small amount of data transmission in an RRC inactive state and transmitting Msg 3 or Msg A including small amount of data to a base station, and It provides a method comprising the step of receiving from a base station Msg 4 or Msg B including information for overload control.

In another aspect, in a method for a base station to control a small amount of data load, based on the step of receiving Msg 3 or Msg A including small amount of data from a terminal in an RRC inactive state and whether small amount of data can be received Thus, it provides a method including generating information for overload control and transmitting Msg 4 or Msg B including information for overload control to a terminal.

In another aspect, the terminal controlling the small amount of data load performs a control unit that triggers small amount of data transmission in an RRC inactive state, a transmission unit that transmits Msg 3 or Msg A including small amount of data to the base station, and overload control. It provides a terminal device including a receiving unit for receiving from the base station Msg 4 or Msg B including information for.

In another aspect, the base station controlling the small amount of data load controls the overload based on the receiving unit receiving Msg 3 or Msg A including small amount of data from the terminal in the RRC inactive state and whether the small amount of data can be received. It provides a base station apparatus including a control unit for generating information for and a transmission unit for transmitting Msg 4 or Msg B including information for overload control to a terminal.

According to the present disclosure, it is possible to control a load generated by a small amount of data transmission by a terminal.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which the present embodiment can be applied.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

7 is a diagram for explaining CORESET.

8 is a diagram illustrating an example in which different subcarrier spacings are arranged at a symbol level.

9 is a diagram illustrating an example of a terminal configuration including a 5GMM (or NAS MM) entity to which the present embodiment can be applied.

10 is a diagram for explaining a 2-step random accessor procedure (2-step RACH) to which the present embodiment can be applied.

11 is a flowchart illustrating an operation of a terminal according to the present embodiment.

12 is a flowchart illustrating an operation of a base station according to the present embodiment.

13 is a diagram for describing an R/F/LCID/L MAC subheader with 8-bit L field according to an embodiment.

14 is a diagram illustrating an R/F/LCID/L MAC subheader with 16-bit L field according to an embodiment.

15 is a diagram for describing an R/LCID MAC subheader according to an embodiment.

16 is a diagram for describing an LCID value in a MAC according to an embodiment.

17 is a diagram illustrating an example MAC RAR format according to an embodiment.

18 is a diagram for describing a configuration of a terminal according to an embodiment.

19 is a diagram illustrating a configuration of a base station according to an embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When "include", "have", "consists of" and the like mentioned in the present specification are used, other parts may be added unless "only" is used. In the case of expressing the constituent elements in the singular, the case including plural may be included unless there is a specific explicit description.

In addition, in describing the constituent elements of the present disclosure, terms such as first, second, A, B, (a) and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, order, or number of the component is not limited by the term.

In the description of the positional relationship of the components, when two or more components are described as being "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected" ", but it will be understood that two or more components and other components may be further "interposed" to be "connected", "coupled" or "connected". Here, the other components may be included in one or more of two or more components "connected", "coupled" or "connected" to each other.

In the description of the temporal flow relationship related to the components, the operation method or the manufacturing method, for example, the temporal predecessor relationship such as "after", "after", "after", "before", etc. Alternatively, a case where a flow forward and backward relationship is described may also include a case that is not continuous unless "direct" or "direct" is used.

On the other hand, when a numerical value for a component or its corresponding information (e.g., level, etc.) is mentioned, the numerical value or its corresponding information is related to various factors (e.g., process factors, internal or external impacts, etc.) It can be interpreted as including an error range that may be caused by noise, etc.).

The wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The embodiments disclosed below can be applied to a wireless communication system using various wireless access technologies. For example, the present embodiments include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA). Alternatively, it may be applied to various various wireless access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented with a wireless technology such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA), and employs OFDMA in downlink and SC- in uplink. Adopt FDMA. As described above, the present embodiments may be applied to a wireless access technology currently disclosed or commercialized, and may be applied to a wireless access technology currently being developed or to be developed in the future.

Meanwhile, a terminal in the present specification is a generic concept that refers to a device including a wireless communication module that performs communication with a base station in a wireless communication system, and is used in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio). It should be interpreted as a concept that includes all of the UE (User Equipment) of, as well as the MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), and wireless device in GSM. In addition, the terminal may be a user's portable device such as a smart phone according to the usage type, and in the V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module so that machine type communication is performed.

The base station or cell of the present specification refers to the end of communication with the terminal in terms of the network, and Node-B (Node-B), eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Point (e.g., Transmit Point, Receiving Point, Transmitting Point), Relay Node ), a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell. Also, the cell may mean including a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean an activation BWP of the terminal.

In the various cells listed above, since there is a base station controlling one or more cells, the base station can be interpreted in two ways. 1) In relation to the radio area, the device itself may provide a mega cell, a macro cell, a micro cell, a pico cell, a femto cell, and a small cell, or 2) the radio area itself may be indicated. In 1), all devices that are controlled by the same entity that provide a predetermined wireless area are controlled by the same entity, or all devices that interact to form a wireless area in collaboration are instructed to the base station. A point, a transmission/reception point, a transmission point, a reception point, etc. may be an embodiment of a base station according to the configuration method of the wireless area. In 2), it is also possible to instruct the base station to the radio region itself to receive or transmit a signal from the viewpoint of the user terminal or the viewpoint of a neighboring base station.

In the present specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point, and the transmission/reception point itself. I can.

Uplink (Uplink, UL, or uplink) refers to a method of transmitting and receiving data to a base station by a UE, and downlink (Downlink, DL, or downlink) refers to a method of transmitting and receiving data to a UE by a base station. do. Downlink may refer to a communication or communication path from multiple transmission/reception points to a terminal, and uplink may refer to a communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of the multiple transmission/reception points, and the receiver may be a part of the terminal. In addition, in the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of the multiple transmission/reception points.

Uplink and downlink transmit and receive control information through a control channel such as Physical Downlink Control CHannel (PDCCH), Physical Uplink Control CHannel (PUCCH), and the like, and The same data channel is configured to transmit and receive data. Hereinafter, a situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH is expressed in the form of'transmitting and receiving PUCCH, PUSCH, PDCCH and PDSCH' do.

In order to clarify the description, hereinafter, the present technical idea is mainly described with a 3GPP LTE/LTE-A/NR (New RAT) communication system, but the present technical feature is not limited to the corresponding communication system.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from 4G communication technology and LTE-A pro, which has improved LTE-Advanced technology as a 5G communication technology to meet the requirements of ITU-R. Both LTE-A pro and NR refer to 5G communication technology. Hereinafter, 5G communication technology will be described centering on NR when a specific communication technology is not specified.

The operation scenario in NR defined various operation scenarios by adding considerations to satellites, automobiles, and new verticals from the existing 4G LTE scenario.In terms of service, eMBB (Enhanced Mobile Broadband) scenario, high terminal density, but wide It is deployed in the range and supports the mMTC (Massive Machine Communication) scenario that requires a low data rate and asynchronous connection, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and supports high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, a low latency technology, a mmWave support technology, and a forward compatible provision technology are applied. In particular, in the NR system, various technological changes are proposed in terms of flexibility to provide forward compatibility. The main technical features of the NR will be described below with reference to the drawings.

<NR system general>

1 is a diagram schematically showing a structure of an NR system to which this embodiment can be applied.

1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and NG-RAN controls user plane (SDAP/PDCP/RLC/MAC/PHY) and UE (User Equipment). It is composed of gNB and ng-eNB that provide plane (RRC) protocol termination. The gNB or gNB and ng-eNB are interconnected through an Xn interface. The gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as a terminal access and mobility control function, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6GHz (FR1, Frequency Range 1) and frequencies above 6GHz (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in the present specification should be understood in a sense encompassing gNB and ng-eNB, and may be used as a means to distinguish between gNB or ng-eNB as necessary.

<NR wave form, numer roller and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with MIMO (Multiple Input Multiple Output), and has the advantage of being able to use a low complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, and coverage are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

Specifically, the NR transmission neuron is determined based on sub-carrier spacing and CP (cyclic prefix), and the value of μ is used as an exponential value of 2 based on 15khz as shown in Table 1 below. Is changed to.

μ	Subcarrier spacing	Cyclic prefix	Supported for data	Supported for synch
0	15	Normal	Yes	Yes
One	30	Normal	Yes	Yes
2	60	Normal, Extended	Yes	No
3	120	Normal	Yes		Yes
4	240	Normal	No	Yes

As shown in Table 1 above, the NR neuron can be classified into 5 types according to the subcarrier interval. This is different from the fixed subcarrier spacing of 15khz of LTE, one of the 4G communication technologies. Specifically, subcarrier intervals used for data transmission in NR are 15, 30, 60, and 120khz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 12, and 240khz. In addition, the extended CP is applied only to the 60khz subcarrier interval. On the other hand, a frame structure in NR is defined as a frame having a length of 10 ms consisting of 10 subframes having the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame includes 5 subframes. In the case of the 15khz subcarrier interval, one subframe consists of 1 slot, and each slot consists of 14 OFDM symbols.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

Referring to FIG. 2, in the case of a normal CP, a slot is fixedly composed of 14 OFDM symbols, but the length in the time domain of the slot may vary according to the subcarrier interval. For example, in the case of a newer roller having a 15khz subcarrier interval, a slot is 1ms long and has the same length as the subframe. In contrast, in the case of a newer roller with a 30khz subcarrier spacing, a slot consists of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5ms. That is, the subframe and the frame are defined with a fixed time length, and the slot is defined by the number of symbols, and the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot, and introduces a mini-slot (or sub-slot or non-slot based schedule) in order to reduce the transmission delay of the radio section. If a wide subcarrier spacing is used, the length of one slot is shortened in inverse proportion, so that transmission delay in the radio section can be reduced. The mini-slot (or sub-slot) is for efficient support for the URLLC scenario, and scheduling is possible in units of 2, 4, or 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation as a symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of transmitting HARQ ACK/NACK directly within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which a downlink symbol and an uplink symbol are combined are supported. In addition, NR supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station may inform the UE of whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station can indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, and dynamically indicates through Downlink Control Information (DCI) or statically or through RRC. It can also be quasi-static.

<NR physical resource>

Regarding the physical resource in NR, the antenna port, resource grid, resource element, resource block, bandwidth part, etc. are considered. do.

The antenna port is defined so that a channel carrying a symbol on an antenna port can be inferred from a channel carrying another symbol on the same antenna port. When the large-scale property of a channel carrying a symbol on one antenna port can be inferred from a channel carrying a symbol on another antenna port, the two antenna ports are QC/QCL (quasi co-located or quasi co-location) relationship. Here, the wide-range characteristic includes at least one of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram illustrating a resource grid supported by a radio access technology to which the present embodiment can be applied.

Referring to FIG. 3, since the NR supports a plurality of neurons in the same carrier, a resource grid may exist according to each neuron in the resource grid. In addition, the resource grid may exist according to antenna ports, subcarrier spacing, and transmission directions.

A resource block consists of 12 subcarriers, and is defined only in the frequency domain. In addition, a resource element consists of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, the size of one resource block may vary according to the subcarrier interval. In addition, NR defines “Point A” that serves as a common reference point for the resource block grid, a common resource block, and a virtual resource block.

4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

In NR, unlike LTE where the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in the NR, as shown in FIG. 4, a bandwidth part (BWP) can be designated within the carrier bandwidth and used by the terminal. In addition, the bandwidth part is associated with one neurology and is composed of a subset of consecutive common resource blocks, and can be dynamically activated over time. The UE is configured with up to four bandwidth parts, respectively, in uplink and downlink, and data is transmitted and received using the active bandwidth part at a given time.

In the case of a paired spectrum, uplink and downlink bandwidth parts are independently set, and in the case of an unpaired spectrum, unnecessary frequency re-tuning between downlink and uplink operations is prevented. For this purpose, the downlink and uplink bandwidth parts are set in pairs to share a center frequency.

<NR initial connection>

In NR, the terminal accesses the base station and performs cell search and random access procedures to perform communication.

Cell search is a procedure in which a terminal synchronizes with a cell of a corresponding base station, obtains a physical layer cell ID, and obtains system information by using a synchronization signal block (SSB) transmitted by a base station.

5 is a diagram illustrating a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

Referring to FIG. 5, an SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, respectively, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in the time and frequency domain.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms time, and the UE performs detection on the assumption that SSBs are transmitted every 20 ms period based on one specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted under 3GHz, and up to 8 in a frequency band of 3 to 6GHz, and a maximum of 64 different beams in a frequency band of 6GHz or higher can be used to transmit SSBs.

Two SSBs are included in one slot, and the start symbol and the number of repetitions in the slot are determined according to the subcarrier interval as follows.

Meanwhile, the SSB is not transmitted at the center frequency of the carrier bandwidth, unlike the conventional LTE SS. That is, the SSB may be transmitted even in a place other than the center of the system band, and a plurality of SSBs may be transmitted in the frequency domain when broadband operation is supported. Accordingly, the UE monitors the SSB by using a synchronization raster, which is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are information on the center frequency of the channel for initial access, have been newly defined in NR, and the synchronization raster has a wider frequency interval than the carrier raster to support fast SSB search of the terminal. I can.

The UE can acquire the MIB through the PBCH of the SSB. The MIB (Master Information Block) includes minimum information for the terminal to receive remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, PBCH is information about the location of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (e.g., SIB1 neurology information, information related to SIB1 CORESET, search space information, PDCCH Related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neurology information is equally applied to some messages used in the random access procedure for accessing the base station after the terminal completes the cell search procedure. For example, the neurology information of SIB1 may be applied to at least one of messages 1 to 4 for a random access procedure.

The aforementioned RMSI may mean System Information Block 1 (SIB1), and SIB1 is periodically broadcast (ex, 160ms) in a cell. SIB1 includes information necessary for the UE to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the UE to receive SIB1, it is necessary to receive newer roller information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling through the PBCH. The UE checks scheduling information for SIB1 using SI-RNTI in CORESET, and acquires SIB1 on the PDSCH according to the scheduling information. SIBs other than SIB1 may be periodically transmitted or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 6, when the cell search is completed, the UE transmits a random access preamble for random access to the base station. The random access preamble is transmitted through the PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH consisting of consecutive radio resources in a specific slot that is periodically repeated. In general, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when a random access is performed for beam failure recovery (BFR), a contention-free random access procedure is performed.

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

Upon receiving a valid random access response, the terminal processes the information included in the random access response and performs scheduled transmission to the base station. For example, the UE applies TAC and stores a temporary C-RNTI. Also, by using UL Grant, data stored in the buffer of the terminal or newly generated data is transmitted to the base station. In this case, information for identifying the terminal should be included.

Finally, the terminal receives a downlink message for resolving contention.

<NR CORESET>

The downlink control channel in NR is transmitted in CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits uplink/downlink scheduling information, SFI (Slot Format Index), and TPC (Transmit Power Control) information. .

In this way, NR introduced the concept of CORESET to secure system flexibility. CORESET (Control Resource Set) means a time-frequency resource for a downlink control signal. The terminal may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. A QCL (Quasi CoLocation) assumption for each CORESET is set, and this is used to inform the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7, CORESET may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of up to 3 OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration so that additional configuration information and system information can be received from the network. After establishing the connection with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions, bands, subbands, control channels, data channels, synchronization signals, various reference signals, various signals, or various messages related to NR (New Radio) Can be interpreted as a meaning used in the past or present, or in various meanings used in the future.

New Radio (NR)

As described above, NR, which has been recently conducted in 3GPP, has been designed to satisfy various QoS requirements required for each subdivided and specified usage scenario, as well as an improved data transmission rate compared to LTE. In particular, eMBB (enhancement mobile broadband), mMTC (massive MTC), and URLLC (Ultra Reliable and Low Latency Communications) were defined as representative usage scenarios for NR. flexible) frame structure design is required. Each usage scenario has different requirements for data rates, latency, reliability, and coverage. Accordingly, as a method for efficiently satisfying the requirements for each usage scenario through the frequency band constituting an arbitrary NR system, radio resource units (eg, subcarrier spacing, subframe, TTI, etc.) based on different numerology (eg subcarrier spacing, subframe, TTI, etc.) unit) is designed to be efficiently multiplexed.

For example, discussion has been made on a method of multiplexing and supporting numerology with different subcarrier spacing values based on TDM, FDM or TDM/FDM through one or more NR component carrier(s). lost. In addition, in configuring a scheduling unit in the time domain, discussion has been made on a method of supporting more than one time unit. In this regard, in NR, a subframe is defined as a kind of time domain structure. As a reference numerology for defining the corresponding subframe duration, it was decided to define a single subframe duration consisting of 14 OFDM symbols of normal CP overhead based on 15kHz Sub-Carrier Spacing (SCS) same as LTE. Accordingly, in NR, the subframe has a time duration of 1 ms. However, unlike LTE, a subframe of NR is an absolute reference time duration, and slots and mini-slots may be defined as time units that are the basis of actual uplink/downlink data scheduling. In this case, the number of OFDM symbols constituting the slot and the y value were determined to have a value of y=14 regardless of the SCS value in the case of normal CP.

Accordingly, an arbitrary slot consists of 14 symbols. In addition, depending on the transmission direction of the corresponding slot, all symbols may be used for DL transmission, all symbols may be used for UL transmission, or DL portion + (gap) + UL portion. have.

In addition, in any numerology (or SCS), a mini-slot consisting of fewer symbols than the aforementioned slot is defined. A short time-domain scheduling interval for transmitting/receiving uplink/downlink data based on a mini-slot may be set, or a long time-domain scheduling interval for transmitting/receiving uplink/downlink data through slot aggregation. have. In particular, in the case of transmitting/receiving latency-sensitive data such as URLLC, it is difficult to satisfy the latency requirement when 1ms (14 symbols)-based slot unit scheduling defined in a numerology-based frame structure with a small SCS value such as 15 kHz is performed. I can. Accordingly, by defining a mini-slot composed of fewer OFDM symbols than a slot composed of 14 symbols, scheduling capable of satisfying the requirements of URLLC can be performed based on this.

8 is a diagram for exemplifying symbol level alignment between different SCSs in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 8, R supports the following structure on the time axis. The difference from the existing LTE is that in NR, the basic scheduling unit is changed to the aforementioned slot. Also, as shown in FIG. 9, regardless of subcarrier spacing, a slot consists of 14 OFDM symbols. On the other hand, it supports a non-slot structure (mini-slot structure) composed of 2, 4, and 7 OFDM symbols, which are smaller scheduling units. The non-slot structure can be used as a scheduling unit for URLLC service.

■ Radio frame: Fixed 10ms regardless of numerology (SCS) (Fixed 10ms regardless of numerology).

■ Subframe: Fixed 1ms as a reference for time duration in the time domain. Unlike LTE, it is not used as a scheduling unit for data and control signals.

■ Slot: Mainly for eMBB scenario. Include 14 OFDM symbols.

■ Non-slot (i.e. mini-slot): Mainly for URLLC, but not limited to URLLC only. Include 2, 4, or 7 OFDM symbols (Include 2, 4, or 7 OFDM symbols).

■ One TTI duration: A time duration for data/control channel transmission. A number of OFDM symbols per a slot/non-slot in the time main

In addition, as described above, numerology having different SCS values in one NR carrier may be multiplexed in a TDM and/or FDM scheme to support. Therefore, a method of scheduling data according to latency requirements based on the slot (or mini-slot) length defined for each numerology is also considered. For example, when the SCS is 60 kHz, the symbol length is reduced by about 1/4 compared to the SCS 15 kHz, so when one slot is configured with the same 14 OFDM symbols, the 15 kHz-based slot length becomes 1 ms. On the other hand, the slot length based on 60 kHz is reduced to about 0.25 ms.

Small data transfer

Many application programs installed in smart phone terminals, MTC terminals, IoT terminals, etc. frequently or occasionally transmit small data packets. Whenever the terminal transmits a small amount of data, when performing an RRC connection state transition, signaling overhead and power consumption are caused, which is inefficient. For example, the RRC IDLE state UE must transition to the RRC connected state through the RRC setup procedure for small data transmission. Thereafter, the terminal must activate security to transmit user data and release the RRC connection. In order to solve this problem, various techniques have been proposed for efficiently transmitting small amounts of data.

However, in the case of the proposed prior art, a small amount of data was transmitted through an RRC message. Therefore, there is a problem that the overhead for RRC message generation and transmission/reception processing still exists. In addition, in the case of a small amount of data transmission that does not include an RRC message, there is a problem that overload control for a data transmission request is impossible when the load of the base station increases.

The present disclosure, which was devised to solve this problem, proposes a method and apparatus capable of effectively transmitting and receiving a small amount of data without an RRC message to an RRC inactive terminal or an RRC idle terminal based on an NR. In addition, in transmitting a small amount of data without an RRC message, a base station provides a method and apparatus for controlling overload in response to a data transmission request from a terminal.

Hereinafter, a method of transmitting a small amount of data based on an NR radio access technology will be described. However, this is for better understanding, and the present embodiment may be applied to any radio access technology such as LTE technology or WiFi technology. In addition, embodiments described in the present disclosure include information elements and contents of operations specified in TS38.321, which is an NR MAC standard, and TS 38.331, which is an NR RRC standard. Even if the contents of the terminal operation related to the definition of the corresponding information element are not included in the present specification, the contents specified in the standard specification, which is a known technique, are included in the present embodiment to be understood.

Meanwhile, below, a small data transmission technique according to the present embodiment is described as SDT (small data transmission) as necessary. This is for convenience of description and is not limited to the corresponding name. In addition, the following description will focus on the SDT method and access control of the RRC inactive terminal, but the same or similar can be applied to the RRC idle terminal.

If the RRC inactive terminal can perform SDT without an RRC message, it is possible to reduce the overhead for processing the RRC message. However, if the RRC message is not provided, functions that could be provided through RRC procedure and signaling cannot be provided. For example, when the load of the base station is high, it becomes difficult to provide an overload control function that rejects an RRC connection request. For another example, it becomes difficult to provide an access control function that prohibits the access of the terminal when the load on the base station is high. In the prior art, in order for the NR-based RRC inactive terminal to process mobile outgoing data, it was necessary to perform an RRC connection resumption procedure. When the upper layer of the terminal requests to resume the suspended RRC connection, the RRC initiated the RRC connection resumption procedure. Through the RRC connection resumption procedure, the UE and the base station resumed RRC connection by transmitting and receiving a corresponding RRC message. In this process, when an overload occurs in the base station, the overload can be controlled by using the RRC connection rejection message for the RRC connection request message.

In order to effectively perform SDT without an RRC message, it is necessary to modify/redesign an RRC connection resumption procedure or an RRC connection establishment procedure based on RRC signaling. Alternatively, an RRC connection resumption procedure based on RRC signaling or an RRC procedure different from the RRC connection establishment procedure must be defined. This may include an interworking function between an upper layer including NAS (NAS MM, NAS SM, application) and a lower layer including RRC (RRC, SDAP, PDCP, RLC, MAC, PHY). In addition, in the SDT technology, the RRC procedure may include an interworking function to trigger/instruct SDT without an RRC message in a lower layer. Hereinafter, a small amount of data transmission and an access control method therefor will be described. In addition, as a failure processing method for small amount data transmission, an overload control method for small amount data transmission will be described. The embodiments provided below may be applied individually or by arbitrarily combining/combining each of the embodiments. If there is no separate description below, the upper layer may represent one or more of NAS MM, NAS SM, and application. In addition, the lower layer may represent one or more of RRC, SDAP, PDCP, RLC, MAC, and PHY.

First, a NAS entity structure will be described for understanding of the present disclosure.

9 is a diagram illustrating an example of a terminal configuration including a 5GMM (or NAS MM) entity to which the present embodiment can be applied.

Referring to FIG. 9, the 5GMM (or NAS MM) entity 920 here represents an entity that processes a NAS signaling message between the UE 900 or the UE 900 and the Access and Mobility Management Function (AMF) within the AMF. In addition, the 5GSM (or NAS SM) entity 910 may interact/interact with upper layers such as an application and an operating system (OS). The upper layer may request the 5GSM entity 910 to establish a PDU session indicating at least one PDU session attribute. The 5GSM entity 910 in the terminal 900 may indicate an attribute of a newly established PDU session to a higher layer. The attribute of the PDU session includes, for example, one or more of PDU session identity, SSC mode, S-NSSAI, DNN, PDU session type, access type, and PDU address.

The AS layer 930 is configured under the NAS MM 920 and may include an RRC entity, an L2 entity, and an L1 entity.

Meanwhile, the present disclosure will be described based on an operation of transmitting a small amount of data through a random access procedure. Accordingly, the present disclosure may be applied to a 2-step random access procedure as well as an existing 4-step random access procedure.

10 is a diagram for explaining a 2-step random accessor procedure (2-step RACH) to which the present embodiment can be applied.

Referring to FIG. 10, the 2-step random access procedure is for simplifying the existing 4-step random access procedure, and refers to a procedure in which the terminal and the base station each perform one step.

For example, in the first step, the terminal 1000 transmits Msg A to the base station 1010, and in the second step, the base station 1010 transmits MsgB to the terminal 1000. Msg A includes a preamble on the PRACH and uplink data on the PUSCH. MsgB contains information for RA response and contention resolution.

In the 2-step RACH, the PUSCH okay is defined as a time-frequency resource for payload transmission. The PUSCH okays can be configured separately from the PRACH okays. Alternatively, the relative position of the PUSCH occasion may be configured with respect to the associated PRACH occasion. For example, a time/frequency relationship between PRACH preambles and PUSCH okays in the PRACH occasion(s) may have a single standard fixed value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single standard fixed value. For another example, a time/frequency relationship between PRACH preambles in the PRACH occasion(s) and the PUSCH okay may have a single semi-statically configured value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single semi-statically configured value.

In this specification, for convenience of explanation, a method of transmitting small amount of data without an RRC connection using a 4-step RACH or a 2-step RACH and a method of controlling overload will be described. However, the main embodiments may be applied even when a small amount of data is transmitted over an RRC connection, and may be included in the scope of the present disclosure. In addition, small amount of data in the present specification refers to data transmitted from the terminal to the base station through the RACH procedure, and the term is not limited. That is, data less than a predetermined predetermined TBS may mean a small amount of data, or data transmitted from the terminal to the base station without an RRC message.

Hereinafter, the operation of the terminal and the base station according to the present disclosure will be described.

11 is a flowchart illustrating an operation of a terminal according to the present embodiment.

Referring to FIG. 11, a method of controlling a small amount of data load by a terminal may include triggering a small amount of data transmission in an RRC inactive state (S1110).

For example, a UE in an RRC inactive state or an RRC idle state may trigger a small amount of data transmission in an upper layer. For example, a UE in an RRC inactive state or an RRC idle state may trigger a small amount of data transmission in the NAS layer. In this case, the NAS layer may instruct the RRC connection resumption request to the lower layer. As another example, the MAC entity may acquire small amount of data transmission indication information through Msg 3 (Message 3) or Msg A (Message A) based on the RRC connection resumption request. That is, the UE may instruct the MAC layer to transmit a small amount of data through Msg 3 or Msg A when an RRC connection resumption request is indicated to a lower layer. To this end, the MAC layer may receive indication information indicating transmission of Msg 3 or Msg A from an upper portion of the MAC layer.

On the other hand, the small amount of data transmission indication information through Msg 3 or Msg A further includes at least one of RRC message type, RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. You may.

In addition, the method of controlling the small amount of data load by the terminal may include transmitting Msg 3 or Msg A including small amount of data to the base station (S1120).

For example, if Msg 3 or Msg A transmission is determined based on the small amount of data transmission indication information through Msg 3 or Msg A, the terminal may transmit Msg 3 or Msg A to the base station. Msg 3 or Msg A may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening in the MAC CE. For example, Msg 3 or Msg A for small data transmission may not include an RRC message.

Meanwhile, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

In addition, the method of controlling a small amount of data load by the terminal may include receiving from the base station Msg 4 or Msg B including information for overload control (S1130). After transmitting Msg 3 or Msg A, the UE receives Msg4 or MsgB including confirmation information for Msg 3 or Msg A from the base station.

For example, Msg 4 or Msg B is a transmission failure of Msg 3 or Msg A containing small data in MAC CE or MAC RAR or MAC subheader, rejection of transmission of Msg 3 or Msg A including the small amount of data, RRC It may include at least one of information indicating connection denial, fallback random access response, and waiting time information.

For example, Msg 4 or Msg B may include information indicating that a small amount of data transmitted by the terminal is rejected by the base station or that transmission has failed. Transmission failure information of Msg 3 or Msg A, transmission rejection information of Msg 3 or Msg A including the small amount of data, and RRC connection rejection information indicate that Msg 3 or Msg A transmitted by the terminal to the base station was not successfully delivered. Instruct. In addition, the waiting time information may indicate a predetermined waiting time for RRC connection or small data transmission requested by the base station to the terminal. The above-described information may be included in the MAC CE or MAC RAR or MAC subheader of Msg 4 or Msg B and received.

On the other hand, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the base station may receive Msg 4 or MsgB and instruct the RRC state of the UE to not change unnecessary. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The above-described MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and received by the UE.

When Msg 4 or Msg B is received, the UE may transfer information included in Msg 4 or Msg B to the RRC layer. The RRC layer can deliver the information to the NAS layer. For example, the terminal transmits the indication information on the above-described small data transmission failure or the RRC state of the terminal to the Non-Access Stratum (NAS) layer through the MAC entity. The NAS layer may recognize whether a small amount of data is transmitted or whether the terminal is instructed to change the state through the transmitted information.

Meanwhile, when the terminal transmits a small amount of data in Msg A through a 2-step random access procedure, the terminal receives Msg B from the base station. As described above, the information for overload control may include at least one of transmission failure of Msg 3 or Msg A, transmission rejection of Msg 3 or Msg A including a small amount of data, RRC connection rejection, and latency information. . In addition, information indicating a fallback random access response to information for overload control may be included. When the information for overload control is included in Msg B, the UE may retransmit Msg 3 including a small amount of data after receiving the corresponding Msg B. That is, the terminal receives information for overload control of the base station and transmits Msg 3 when the information for overload control indicates a fallback random access response. Through this, the terminal can transmit a small amount of data by changing the random access procedure from the 2-step random access procedure to the 4-step random access procedure.

As described above, the terminal may transmit a small amount of data through a random access procedure in the RRC inactive state or the idle state. In this case, the base station may control whether to receive Msg 3 or Msg A including a small amount of data in the random access procedure of the terminal for overload control. When the terminal receives Msg 4 or Msg B including information for overload control, it may process by suspending/cancelling small data transmission or changing a random access procedure based on the information for overload control. A detailed procedure in the case of success by transmitting a small amount of data without an RRC message will be described in detail below.

12 is a flowchart illustrating an operation of a base station according to the present embodiment.

Referring to FIG. 12, a method for the base station to control a small amount of data load may include receiving Msg 3 or Msg A including small amount of data from a terminal in an RRC inactive state (S1210).

When a small amount of data transmission is triggered by the terminal, the base station receives Msg 3 or Msg A including small amount of data. For example, Msg 3 or Msg A may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening. In addition, Msg 3 or Msg A may not include an RRC message. Here, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

The method for the base station to control the small amount of data load may include generating information for overload control based on whether the small amount of data can be received (S1220). For example, the base station may generate information for overload control based on the load information of the base station. Information for overload control may be generated for each random access message of the terminal. For example, the information for overload control is at least one of transmission failure of Msg 3 or Msg A including small amount of data, transmission rejection of Msg 3 or Msg A including small amount of data, RRC connection rejection, and latency information. It may include. That is, the information for overload control may include indication information for processing when the base station cannot receive Msg 3 or Msg A of the terminal. Alternatively, the information for overload control may include information indicating a fallback random access response.

Meanwhile, the base station may successfully receive Msg 3 or Msg A including small amount of data of the terminal. For example, the base station checks Msg 3 or Msg A received from the terminal and receives a small amount of data.

The method for the base station to control a small amount of data load may include transmitting Msg 4 or Msg B including information for overload control to the terminal (S1230).

For example, the base station may include the above-described information for overload control in the MAC CE or MAC RAR or MAC subheader of Msg 4 or Msg B and transmit the information to the terminal. For example, when the base station receives a small amount of data through Msg A and transmits information for overload control through Msg B, if the information for overload control includes information indicating a fallback random access response, Msg B After transmission, Msg 3 including a small amount of data may be further received. That is, when receiving a small amount of data through a two-step random access procedure, the base station may instruct a fallback random access response to the terminal for overload control. When the fallback random access response is instructed, the UE changes the procedure to a 4-step random access procedure and transmits a small amount of data in Msg 3 to the base station.

Meanwhile, when the base station can receive a small amount of data and receives it, Msg 4 or Msg B including the following information may be transmitted.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle. That is, the base station may instruct not to cause unnecessary RRC state change of the terminal through Msg 4 or MsgB. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The aforementioned MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and transmitted to the terminal.

The operation of the terminal and the base station described with reference to FIGS. 11 and 12 will be described in more detail below by dividing detailed embodiments. The detailed embodiments described below may be performed by the operations of the terminal and the base station described above, and may be performed as a separate operation in a specific operation step or before/after the aforementioned step.

Hereinafter, the overall operation of the terminal and the base station will be described based on individual operation embodiments. Each of the embodiments described below may be individually or all or partly combined with each other to be performed by a terminal or a base station.

In each embodiment, a method of transmitting a small amount of data without an RRC message of a terminal and an overload control operation of a base station are described.

1. How to provide MAC CE-based overload control through Msg4

For overload control based on RRC signaling, cause information in the RRC connection request message was used. For example, the terminal transmits the RRC connection request message including cause information (establishmentcause or resumecasue). Upon receiving this, the base station establishes/allows or rejects the RRC connection based on the cause information included in the terminal when overload occurs. Through this, the base station was able to prevent subsequent processing of additional signaling messages and data transmission/reception after RRC connection establishment. Since this is based on RRC signaling, if a small amount of data is to be transmitted without an RRC message, a method for effectively supporting this may be needed.

If the terminal transmits Msg 3 with a small amount of data without RRC, the base station may control overload through Msg 4. For example, it should be able to provide a function of rejecting a small amount of data transmission by a terminal due to a lack of random resources and an overload in the base station. For example, a corresponding function may be provided through MAC CE. Through this, the base station can instruct the terminal of the SDT (Small Data Transmission) failure. Hereinafter, an SDT procedure for transmitting small amount of data without RRC signaling through a 4-step RACH and an overload control method will be described.

First, a procedure for transmitting a small amount of data without an RRC message will be described.

In the case of SDT through 4-step random access in the corresponding serving cell, an available set of PRACH resources for random access preamble transmission may be indicated to the terminal through RRC signaling (SIB or dedicated RRC message). The available set of PRACH resources may be provided in association with the coverage level. Alternatively, the available set of PRACH resources may be provided in association with radio quality (eg (for SSB) rsrp threshold/measurement value/level). The base station may indicate a threshold value for selecting SDT through 4-step random access.

If the message size (uplink data for transmission + MAC header, MAC CE if necessary) is larger than the signaled TBS size, or in SDT through 4-step random access, a fallback is indicated by data transmission through a normal RRC resumption procedure. In the case where the radio quality is bad or the wireless quality is bad, SDT through 4-step random access may be canceled (cancel/abort). The terminal (the terminal's MAC) indicates this to the upper layer (RRC). Alternatively, RRC indicates this as an upper layer (NAS). The upper layer may fall back with a request to resume RRC connection for mobile originated data.

For example, when the PRACH resource linked to the SDT is not available, or when a random access preamble linked to the SDT is transmitted and the uplink grant provided in the random access response message is not for indicating the SDT, a fallback is indicated. Can be. For another example, when rsrp of the SSB is worse than a threshold signaled by the base station (eg, rsrp-ThresholdSSB), it may be indicated as a case of poor radio quality. In these cases, it may be difficult to transmit to the corresponding TBS, so it may be desirable to cancel. This makes it possible to provide a small amount of data transmission through SDT only when the radio quality or load is good.

The terminal selects a PRACH resource associated with the SDT for the terminal. The terminal transmits a random access preamble.

When a random access preamble through 4-step random access linked to the SDT is transmitted, an uplink grant may be provided in the random access response message. If the uplink grant received in the random access response is for indicating SDT and there is a MAC PDU in the Msg3 buffer, the UE transmits Msg3.

For example, if SDT is initiated through Msg3, the terminal recovers the security context from the stored terminal context. The UE recovers the PDCP state (eg PDCP sequence number) for a specific DRB for SDT (or for all SRBs or all DRBs). And the terminal resets the PDCP entity. The UE resumes a specific DRB (or all SRBs or all DRBs). A specific DRB for SDT may be indicated to the terminal through a dedicated RRC message (eg RRC release or RRC release with suspendconfig). The terminal may derive a K _UPenc key associated with a previously configured _ciphering algorithm. Alternatively, the terminal may derive a K _UPint key associated with a previously configured integrity protection algorithm.

For another example, the UE is an authentication token/message authentication code (MAC-I) used for data integrity protection on MAC CE or CCCH on Msg3 or on a DTCH multiplexed with 16 least significant bits of the calculated MAC-I. May include shortMAC-I. Alternatively, the UE may include an authentication token (MAC-I) on the MAC CE on the PUSCH included in Msg3 for integrity protection or shortMAC-I, which is 16 least significant bits of the calculated MAC-I. Alternatively, the terminal may include the establishment cause/resume cause information in the MAC CE. Alternatively, when the RRC receives a request to resume the RRC connection for mobile outgoing data from the upper layer, it transmits the terminal temporary identifier, authentication token for integrity protection, and setup cause/restart cause information to the MAC through 4-step random access. Can be instructed to perform SDT.

For another example, the terminal (the RRC of the terminal) may indicate that the RRC connection suspended in the upper layer has been resumed. Alternatively, the terminal (the RRC of the terminal) may indicate that the SDT is initiated through the RRC connection suspended in the upper layer. This may be provided as information indicating that the suspended RRC connection has been resumed and other information. Through this, the UE can transmit user data to the lower layer by distinguishing that the upper layer is in a state in which data can be transmitted according to the RRC restart request. Through this, it can be seen that even if the terminal does not transmit an RRC message to the base station by using RRC signaling, the upper layer is in a state in which data transmission is possible in the lower layer. If the MAC PDU data to be transmitted from the lower layer (MAC) is larger than the signaled TBS size, indication information for canceling the SDT may be transmitted to the upper layer (RRC). In addition, RRC can fall back to a normal RRC connection resumption procedure. Alternatively, the RRC may indicate the indication information for canceling the SDT to the upper layer, and the higher layer may fall back to the RRC connection resumption request for mobile origin data. For reference, in the prior art, only when the terminal transitions to the RRC connection state after receiving the RRC resume message from the base station, the RRC of the terminal indicated that the RRC connection suspended in the upper layer was resumed.

When the terminal (RRC of the terminal) indicates that the suspended RRC connection has been resumed to the upper layer, the DRB is resumed, Msg3 is transmitted, and the response is received for Msg3 transmission (eg, if HARQ is configured for user data transmission, HARQ ACK is received. , PDCCH reception and Msg4 reception).

The terminal (the RRC of the terminal) may indicate to the upper layer that data has been transmitted through the SDT. Through this, the terminal can distinguish that a small amount of data transmission has been completed in the upper layer, so that the user data can be processed later.

Through this operation, the UE can transmit including user data (small data) on Msg 3 without RRC signaling. User data (small data) transmission on Msg 3 without RRC signaling and a successful response thereto will be separately described later.

Hereinafter, an embodiment in which information for overload control is transmitted from the base station to the terminal will be described.

o MAC CE definition on Msg 4 including indication information for overload control (information for overload control)

When the base station receives Msg 3, the base station may attempt to control overload by rejecting the SDT request for any reason such as overload. As an example, the base station may attempt to indicate to the terminal a failure in SDT transmission. As another example, the base station may wish to limit/prohibit additional SDT transmission. As another example, the base station may wish to limit/prohibit SDT retransmission. As another example, the base station may wish to limit/prohibit any RRC connection resumption/RRC connection setup to the corresponding terminal.

For example, the base station may attempt to perform an overload control operation for at least one of the following reasons.

-Overload on the interface between the base station and the core network control plane entity (e.g. AMF)

-Overload on the interface between the base station and the core network user plane entity (e.g. UPF)

-When sending a request message to the anchor base station to retrieve UE context request, overload on the interface between the corresponding base stations or overload of the corresponding serving cell

When performing an overload control operation, the base station transmits at least one of SDT transmission failure, SDT transmission rejection, SDT additional transmission limitation, SDT retransmission limitation, RRC connection rejection, arbitrary RRC connection limitation, and waiting time for backoff processing. Instructed by This information can be provided through the MAC CE.

Meanwhile, the MAC CE may include information for instructing the terminal to maintain the RRC inactive state and/or information for instructing the terminal to transition to the RRC idle state. The information for instructing the UE to maintain the RRC inactive state and the information for instructing the UE to transition to the RRC idle state may be indicated by different bits, respectively, or two values may be divided and indicated by one bit. Alternatively, the indication information may include information for contention resolution. Even if the base station indicates rejection/failure/restriction of the SDT transmission request through Msg4, if there is contention, the terminal may have to resolve it, and thus contention resolution information may be included together.

In addition, if the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it may be multiplexed to the aforementioned MAC CE and transmitted to the terminal.

Meanwhile, the above-described MAC CE may have an LCID that is distinct from the MAC CE for indicating response/confirmation/completion of SDT transmission. Alternatively, information indicating rejection/failure/restriction on the SDT transmission request through Msg4 may be provided through one MAC CE having a specific LCID. For example, SDT transmission failure, SDT transmission rejection, SDT additional transmission limit, SDT retransmission limit information, information to limit transmission of a general RRC connection request, wait time (eg wait time), the terminal is in the RRC inactive state. One or more of information for instructing to maintain and information for contact resolution may be provided through one MAC CE/SDU/subPDU/PDU (or included in one MAC CE). This can reduce the number of MAC subheader bits.

The waiting time information is a value received by the UE through MAC CE/SDU/subPDU/PDU, and may be used to operate a timer for limiting SDT or a timer for limiting RRC connection setup/resume in the UE. For example, the waiting time information is composed of 4 bits and may represent 1 to 16 seconds. Alternatively, the waiting time information may indicate a value used for user data transmission backoff that is distinguished from a value used for RACH backoff (e.g. a backoff indicator used to set PREAMBLE_BACKOFF). To this end, the MAC may transmit information received through Msg 4 or Msg B to the RRC. For example, the terminal (MAC of the terminal) that has received the waiting time information transmits it to the RRC. The RRC can be started by setting the T302 timer to the waiting time value indicated by the waiting time information. The terminal (the RRC of the terminal) may inform the upper layer (e.g. NAS) that access baring is applied to all access categories except for the access categories “0” (MT paging) and “2” (Emergency).

o Method for transmitting indication information for overload control to Msg4 by dividing it into CCCH

When performing a small amount of data transmission without RRC signaling, one or more control information (or all control information) included in Msg 4 may be classified and transmitted through a CCCH. For example, information for overload control (ex, information indicating rejection/failure/restriction of SDT transmission request) through Msg 4 may be divided into CCCH and transmitted. CCCH is a logical channel for transmitting control information between the UE and the network, and is used when the UE does not have an RRC connection with the network (Common Control Channel (CCCH): channel for transmitting control information between UEs and network.This channel is used for UEs having no RRC connection with the network.). If a small amount of data is transmitted without RRC signaling through Msg 3, the associated control parameter to indicate the rejection/failure/restriction of the SDT transmission request in response to this is assumed to be a control channel used without RRC connection, and all transmitted on the CCCH. Can be.

Although the RRC message itself is not configured as a MAC SDU, information included as an information element in a conventional RRC message or a parameter controlled/used in the RRC may be configured as one fixed-length MAC SDU. Through this, it is possible to reduce the overhead for configuring the RRC format/header.

13 is a diagram for describing an R/F/LCID/L MAC subheader with 8-bit L field according to an embodiment. 14 is a diagram illustrating an R/F/LCID/L MAC subheader with 16-bit L field according to an embodiment.

13 and 14, a MAC SDU including a DL CCCH in the related art had to use a MAC subheader of 2 octets or more. However, if the above-described RRC format/header configuration method is used, the MAC subheader can be reduced.

15 is a diagram for describing an R/LCID MAC subheader according to an embodiment.

Referring to FIG. 15, a 1-octet MAC subheader format may be used according to the above-described RRC format/header configuration method. In this case, compared to FIG. 13 or 14, bits of 1 octet or more may be reduced. As an LCID for the corresponding MAC SDU/subPDU/PDU, a value of 0 for distinguishing the conventional DL CCCH may be used.

Meanwhile, in order to distinguish the newly defined MAC SDU from the conventional CCCH type, the LCID value for the corresponding MAC SDU may have a value different from the conventional 0 value.

16 is a diagram for describing an LCID value in a MAC according to an embodiment.

Referring to FIG. 16, a DL LCID value allocated in the current NR MAC standard is shown. Therefore, one of the 33-46 LCID values currently reserved as a spare state can be used.

o A method of including one or more information of information for Msg 4 control in a subheader

When SDT is transmitted through Msg 3, information for overload control in response to this may be included in the MAC subheader and transmitted to the terminal. As described above, the information for overload control includes SDT transmission failure, SDT transmission rejection, SDT additional transmission limitation, SDT retransmission limitation information, general RRC connection request transmission limitation information, waiting time (eg wait time). ), information for instructing the terminal to maintain the RRC inactive state and information for contact resolution (or terminal identifier or terminal temporary identifier). The MAC subheader including information for overload control can use an existing MAC subheader to designate and use an arbitrary field value on the MAC subheader. Alternatively, the MAC subheader including information for overload control may use a new MAC subheader format that is distinct from conventional NR MAC subheaders. Through this, the number of bits included in the MAC SDU can be reduced. In addition, the corresponding terminal/base station can distinguish and process the corresponding MAC SDU.

In the following, a case of a 2-step random access procedure will be described.

2. Method of providing MAC CE-based overload control through Msg B

The 2-step RACH procedure is a technique proposed for the purpose of reducing the delay of the 4-step RACH procedure, but no specific detailed procedure is currently provided. For convenience of explanation, for the 2-step RACH procedure, the message transmitted from the terminal to the base station in the first step is denoted as Msg A, and the message transmitted from the base station to the terminal in the second step is denoted by Msg B. Msg A includes a preamble on the PRACH and uplink data on the PUSCH. Msg B contains information for contention resolution. Msg B may additionally include information for a random access response (RA response).

In the 2-step RACH, the PUSCH okay is defined as a time-frequency resource for payload transmission. The PUSCH okays can be configured separately from the PRACH okays. Alternatively, the relative position of the PUSCH occasion may be configured with respect to the associated PRACH occasion. For example, a time/frequency relationship between PRACH preambles and PUSCH okays in the PRACH occasion(s) may have a single standard fixed value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single standard fixed value. For another example, a time/frequency relationship between PRACH preambles in the PRACH occasion(s) and the PUSCH okay may have a single semi-statically configured value. For another example, the time/frequency relationship between each PRACH preamble in the PRACH occasion(s) for the PUSCH okay may have a single semi-statically configured value.

In the case of SDT through 2-step random access in the corresponding serving cell, an available set of PRACH resources for random access preamble transmission may be indicated to the terminal through RRC signaling (SIB or dedicated RRC message). The available set of PRACH resources may be provided in association with the coverage level. Alternatively, the available set of PRACH resources may be provided in association with radio quality (eg (for SSB) rsrp threshold/measurement value/level). The base station may indicate a threshold value for selecting SDT through 2-step random access. The information element for the 2-step RACH procedure may be indicated with a different value distinguished from the information element for the 4-step RACH procedure.

If the message size (uplink data for transmission + MAC header, MAC CE if necessary) is larger than the signaled TBS size, or fall back from SDT through 2-step random access to SDT through 4-step random access or 2-step SDT may be canceled (cancel/abort) when a fallback is indicated by data transmission through a normal RRC resumption procedure in SDT through random access or when radio quality is poor.

The terminal (the terminal's MAC) indicates this to the upper layer (RRC). For example, if a fallback is instructed from SDT through 2-step random access to SDT through 4-step random access or from SDT through 2-step random access to data transmission through a normal RRC resumption procedure, the SDT is linked. This refers to a case where the 2-step random access PRACH resource is not available. Or, if a fallback is instructed from SDT through 2-step random access to SDT through 4-step random access or from SDT through 2-step random access to data transmission through a normal RRC resumption procedure, 2-step random linked to SDT This means a case where the access preamble is transmitted and the uplink grant provided in the 2-step random access response message is not for indicating SDT through 2-step random access. For example, the base station may indicate SDT through 4-step random access through a fallback random access response, or may indicate data transmission through a normal RRC resumption procedure.

The case of poor radio quality may indicate a case in which the rsrp of the SSB is worse than the threshold signaled by the base station (eg, MsgA-rsrp-ThresholdSSB through 2-step random access).

In the above-described cases, it may be difficult to transmit to the corresponding TBS, so it may be desirable to cancel. This makes it possible to provide a small amount of data transmission through SDT only when wireless quality or load is good.

The terminal selects a PRACH resource associated with the SDT for the terminal. The UE transmits a random access preamble and MsgA including user data.

For example, if SDT is initiated through MsgA, the terminal recovers the security context from the stored terminal context. The UE recovers the PDCP state (eg PDCP sequence number) for a specific DRB for SDT (or for all SRBs or all DRBs). And the terminal resets the PDCP entity. The UE resumes a specific DRB (or all SRBs or all DRBs). A specific DRB for SDT may be indicated to the terminal through a dedicated RRC message (eg RRC release or RRC release with suspendconfig). The terminal may derive a K _UPenc key associated with a previously configured _ciphering algorithm. Alternatively, the terminal may derive a K _UPint key associated with the previously configured integrity protection algorithm.

For another example, the UE may include an authentication token (MAC-I) or shortMAC-I, which is 16 least significant bits of the calculated MAC-I, in the CCCH on the PUSCH included in Msg A for integrity protection. Alternatively, the UE may include an authentication token (MAC-I) on the multiplexed DTCH with the CCCH on the PUSCH included in the MsgA for integrity protection, or shortMAC-I, which is 16 least significant bits of the calculated MAC-I. The above information may be provided through a separate MAC CE. Alternatively, it may be included and provided in the MAC CE described below.

Meanwhile, the terminal (the RRC of the terminal) may indicate that the RRC connection suspended in the upper layer has been resumed. Alternatively, the terminal (the RRC of the terminal) may indicate that the SDT is initiated through the RRC connection suspended in the upper layer. This may be provided as information indicating that the suspended RRC connection is resumed and other information. Through this, the upper layer of the terminal can transmit the user data to the lower layer by distinguishing that data can be transmitted according to the RRC resume request. In addition, even if the terminal does not transmit an RRC message to the base station through RRC signaling, the upper layer may be able to know that data transmission is possible in the lower layer.

The terminal (the RRC of the terminal) may indicate to the upper layer that data has been transmitted through the SDT. Through this, the terminal can distinguish that a small amount of data transmission has been completed in the upper layer, so that the user data can be processed later.

The UE may transmit including user data on Msg A without RRC signaling. User data transmission on Msg A without RRC signaling and a successful response thereto will be separately described later.

o Method of defining MAC CE/MAC RAR on MsgB including indication information for overload control

When the base station receives Msg A, the base station may attempt to control overload by rejecting the SDT request for any reason such as overload. As an example, the base station may attempt to indicate to the terminal a failure in SDT transmission. As another example, the base station may wish to limit/prohibit additional SDT transmission. As another example, the base station may wish to limit/prohibit SDT retransmission. As another example, the base station may wish to limit/prohibit any RRC connection resumption/RRC connection setup to the corresponding terminal.

For example, the base station may attempt to perform an overload control operation for at least one of the following reasons.

-Overload on the interface between the base station and the core network control plane entity (e.g. AMF)

-Overload on the interface between the base station and the core network user plane entity (e.g. UPF)

-When sending a request message to the anchor base station to retrieve UE context request, overload on the interface between the corresponding base stations or overload of the corresponding serving cell

When performing an overload control operation, the base station transmits at least one of SDT transmission failure, SDT transmission rejection, SDT additional transmission limitation, SDT retransmission limitation, RRC connection rejection, arbitrary RRC connection limitation, and waiting time for backoff processing. Instructed by Information for overload control may be provided through MAC CE or RAR MAC PDU on MsgB, which is a response message to Msg A.

Meanwhile, the MAC CE (or RAR MAC PDU) may include information for instructing the UE to maintain the RRC inactive state and/or information for instructing the UE to transition to the RRC idle state. The information for instructing the UE to maintain the RRC inactive state and the information for instructing the UE to transition to the RRC idle state may be indicated by different bits, respectively, or two values may be divided and indicated by one bit. Alternatively, the indication information may include information for contention resolution. Even when the base station indicates rejection/failure/restriction of the SDT transmission request through Msg B, if there is contention, the terminal may have to resolve the contention resolution information may be included together.

In addition, if the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it may be multiplexed to the aforementioned MAC CE (or RAR MAC PDU) and transmitted to the terminal.

Meanwhile, the above-described MAC CE (or RAR MAC PDU) may have an LCID that is distinguished from the MAC CE (or RAR MAC PDU) for indicating response/confirmation/completion of SDT transmission. Alternatively, information indicating the rejection/failure/restriction of the SDT transmission request through Msg B may be provided through one MAC CE (or RAR MAC PDU) having a specific LCID. For example, SDT transmission failure, SDT transmission rejection, SDT additional transmission limit, SDT retransmission limit information, information to limit transmission of a general RRC connection request, wait time (eg wait time), the terminal is in the RRC inactive state. One or more of information for instructing to maintain and information for contact resolution will be provided through one MAC CE/SDU/RAR subPDU/RAR PDU (included in one MAC CE/SDU/subPDU/PDU). I can. This can reduce the number of MAC subheader bits.

The waiting time information is a value received by the UE through the MAC CE/SDU/RAR subPDU/RAR PDU, and may be used to operate a timer for limiting SDT or a timer for limiting RRC connection setup/resume. For example, the waiting time information is composed of 4 bits and may represent 1 to 16 seconds. Alternatively, the waiting time information may indicate a value used for user data transmission backoff that is distinguished from a value used for RACH backoff (e.g. a backoff indicator used to set PREAMBLE_BACKOFF). To this end, the MAC may transmit information received through Msg B to the RRC. For example, the terminal (MAC of the terminal) that has received the waiting time information transmits it to the RRC. The RRC can be started by setting the T302 timer to the waiting time value indicated by the waiting time information. The terminal (the RRC of the terminal) may inform the upper layer (e.g. NAS) that access baring is applied to all access categories except for the access categories “0” (MT paging) and “2” (Emergency).

Alternatively, the waiting time information may be information distinguished from the backoff indicator provided through the RAR MAC PDU. In addition, the latency information may be included in a MAC subheader that is distinguished from a MAC subheader including only a backoff indicator in the RAR MAC PDU.

o Method for transmitting indication information for overload control to Msg B by dividing it with CCCH

Information indicating the rejection/failure/restriction of the SDT transmission request through Msg B may be divided into CCCH and transmitted. Alternatively, when performing small data transmission without RRC signaling, the base station may divide one or more control information (or all control information) included in Msg B into CCCH and transmit it. If a small amount of data is transmitted through the 2-step RACH without RRC signaling, the RRC control parameter associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without RRC connection.

Msg B does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in the RRC as one fixed-length MAC SDU. Alternatively, Msg B does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled by RRC as one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header.

As described above, the MAC subheader format of 1 octet as shown in FIG. 15 can be used compared to the conventional MAC SDU including the DL CCCH, which had to use 2 or more octets as shown in FIGS. 13 and 14. Thus, it is possible to reduce bits of 1 octet or more. In addition, the LCID for MAC SDU/RAR subPDU/RAR PDU can be used by designating a value for distinguishing a conventional DL CCCH. As another example, the LCID for the corresponding MAC SDU/RAR subPDU/RAR PDU may be assigned a new value that is distinguished from a value of 0, which is a conventional DL CCCH value. One of the 33-46 LCID values currently reserved as spare status can be used.

o A method of including one or more information of information for MsgB control in a subheader

When SDT is transmitted through Msg 3, information for overload control in response to this may be included in the MAC subheader and transmitted to the terminal. As described above, the information for overload control includes SDT transmission failure, SDT transmission rejection, SDT additional transmission limitation, SDT retransmission limitation information, general RRC connection request transmission limitation information, waiting time (eg wait time). ), information for instructing the terminal to maintain the RRC inactive state, information for instructing fallback, and information for contact resolution (or terminal identifier or terminal temporary identifier). The MAC subheader including information for overload control can use an existing MAC subheader to designate and use an arbitrary field value on the MAC subheader. Alternatively, the MAC subheader including information for overload control may use a new MAC subheader format different from conventional NR MAC subheaders or may be partially modified. Through this, the number of bits included in the MAC SDU can be reduced. In addition, the corresponding terminal/base station can distinguish and process the corresponding MAC SDU.

For example, the corresponding MAC subheader may be configured in a format different from the MAC subheader for the MAC subPDU that may be included in the conventional RAR MAC PDU specified in 3GPP TS 38.321. For reference, a conventional RAR MAC PDU may be configured with one or more MAC subPDUs and selectively padding, and each MAC subPDU is a MAC subheader with only a backoff indicator (a MAC subheader with Backoff Indicator only), a random access preamble ID. It may be composed of one of a MAC subheader (a MAC subheader with RAPID only) and a MAC subheader (a MAC subheader with RAPID and MAC RAR) having a random access preamble ID and MAC RAR.

o When a small amount of data is transmitted through Msg A and a 4-step fallback is instructed, how to attempt to transmit a small amount of data through Msg 3

17 is a diagram illustrating an example MAC RAR format according to an embodiment.

Referring to FIG. 17, the UE may transmit small amount of data without RRC signaling through Msg A. In this case, the terminal may receive a response to Msg A from the base station as shown in FIG. 17. In this case, the terminal may perform the SDT operation through Msg 3 described above. For example, although the base station has successfully decoded the random access preamble, decoding for the PUSCH may fail. In this case, the base station may determine that retrying the 2-step RACH is inefficient because it re-transmits the random access preamble. In this case, it is preferable that the UE performs only transmission/retransmission for the PUSCH without transmitting the random access preamble. This is equivalent to allowing the base station to successfully receive the random access preamble through Msg1 in the 4-step RACH operation and transmit Msg2 to the terminal to transmit Msg3. Therefore, hereinafter, this is indicated as indicating to fall back from the 2-step RACH to the 4-step RACH.

For example, the base station may transmit an Msg2 RAR to indicate fallback from the 2-step RACH to the 4-step RACH. The RAR format can be transmitted using the same conventional Msg2 MAC RAR format. As another example, if it is desired to instruct SDT transmission through Msg 3, the base station may additionally include information for indicating this to the terminal in the Msg2 RAR. When the terminal performing SDT through Msg A receives the Msg B fallback RAR that is the same as the Msg2 MAC RAR format or that includes the Msg2 MAC RAR format, the terminal may perform the SDT operation through Msg 3. Alternatively, when the terminal performing SDT through Msg A receives the MsgB fallback RAR that is the same as the Msg2 MAC RAR format or includes the Msg2 MAC RAR format, the terminal may fall back to a 4-step random access procedure. Upon fallback, the terminal may transmit Msg 3. The base station receiving Msg 3 may transmit Msg4. For example, the terminal may transmit an RRC connection setup/resume request message to Msg 3. The base station may transmit an RRC connection setup/resume message to Msg 4. When the RRC inactive UE receives the RRC connection resume message, the UE resumes SRB2 and all DRBs. The terminal enters the RRC connected state. The terminal can transmit the corresponding small amount of data in the RRC connected state. That is, the terminal can perform a normal RRC connection state operation.

As another example, when the base station instructs a fallback to the terminal through the MsgB fallback RAR that is the same as the Msg2 MAC RAR format or includes the Msg2 MAC RAR format, the base station further includes indication information on whether to transmit the SDT through Msg 3 and transmits I can. Through this, the UE can distinguish whether a small amount of data is transmitted through Msg 3 or transitioned to an RRC connected state and transmitted through a normal RRC connected state operation according to the situation of the base station as described above. As an example, information indicating SDT transmission through Msg 3 or transition to an RRC connection state may be included in the aforementioned fallback RAR or fallback RAR MAC subheader. As another example, information indicating SDT transmission through Msg 3 or transition to the RRC connection state and indicating SDT transmission may be indicated using one of the E field or the T1 field of the fallback RAR MAC subheader. As another example, information indicating SDT transmission through Msg 3 or transitioning to an RRC connection state and indicating SDT transmission may be indicated through a MAC CE/MAC subheader/MAC subPDU multiplexed to the fallback RAR and transmitted. As another example, information indicating SDT transmission by transitioning to SDT transmission or RRC connection state through Msg 3 may be configured as a MAC subheader in which MAC subPDU is only a MAC subheader.

3. Terminal operation that processes information for overload control received without RRC signaling (e.g. timer operation on MAC entity, etc.)

The above-described waiting time information is a value that the UE receives from the base station through MAC CE (or MAC SDU/subPDU/PDU/subheader) without RRC signaling. The waiting time information may be used to operate a timer for limiting SDT in the terminal. For example, the waiting time information may be used for SDT additional transmission limitation, SDT retransmission limitation, SDT backoff processing, general RRC connection (setup/resume) request transmission limitation, and the like. For convenience of explanation, an embodiment for limiting SDT will be described below, but a limitation on a general RRC connection procedure may be similarly applied, and this may also be included in the scope of the present disclosure.

Upon receiving the MAC CE (or MAC SDU/subPDU/PDU/subheader) or MAC CE (or MAC SDU/subPDU/PDU/subheader) including the above-described waiting time information, the terminal is set to the received waiting time value. Start the associated timer.

o An embodiment of the case that the corresponding timer operates in the MAC entity

The timer associated with the above-described waiting time information may be executed in the MAC. When the timer is operated, the terminal (MAC entity or RRC) cannot initiate/start/resume/restart SDT. Alternatively, when the timer is operated, the terminal (MAC entity) may prohibit transmission including a small amount of data (or small amount of data without RRC) through Msg 3/Msg A. When the timer starts, the terminal (MAC entity) may indicate that access control/baring has been applied to the upper layer (RRC). When the RRC is instructed by the MAC entity that barring is applied, the RRC may prevent/prohibit starting the SDT procedure. Alternatively, when the RRC is indicated by the MAC entity that barring is applied, the RRC may prevent/prohibit starting the RRC procedure for MO data transmission. Alternatively, when the RRC is indicated by the MAC entity that barring has been applied, the RRC may prevent/prohibit starting any or specific RRC signaling procedure. The RRC may indicate to an upper layer (e.g. NAS) that the aforementioned barring or prohibition operation has been initiated.

Meanwhile, the terminal may generate additional data (e.g. MO data) in the above-described standby/prohibition/backoff state. In this case, the UE may initiate an RRC setup procedure or an RRC resumption procedure for transitioning an RRC connection state other than the SDT. Through this, the RRC idle state terminal may transition to the RRC connected state. And, in the case of the RRC inactive state terminal, it may also transition to the RRC connected state.

When the above-described timer expires (or stops), the terminal (MAC entity) may indicate access control/barring alleviation to the upper layer (RRC). When the RRC is instructed by the MAC entity that the baring is alleviated, the RRC may start/restart/restart the SDT procedure. Alternatively, when the RRC is instructed by the MAC entity that barring is alleviated, the RRC may start/restart/restart the RRC procedure for MO data transmission. Alternatively, when the RRC is indicated by the MAC entity that barring is alleviated, the RRC may start/restart/restart any or specific RRC signaling procedure. In addition, the timer may be stopped/released when the cell reselection procedure or the RRC setup request message is transmitted or the RRC connection procedure is initiated.

o Example when the timer is operated in RRC

The above-described timer may be executed in RRC. When the timer is operated, the terminal (RRC) cannot start/start/resume/restart the SDT. Alternatively, when the timer is operated, the terminal (MAC entity) may prohibit transmission including a small amount of data (or small amount of data without RRC) through Msg 3/Msg A. When the MAC entity of the terminal receives the latency information through the MAC CE (or MAC SDU/subPDU/PDU), it may indicate/transmit it to the RRC. When the timer starts, the terminal RRC may indicate that the access control/baring has been applied to the higher layer NAS. When the NAS is instructed by the RRC that barring has been applied, the NAS may control the service request procedure (or SDT) to not start. When the timer expires (or stops), the terminal (RRC) may indicate access control/barring alleviation to the higher layer (NAS). When the NAS is instructed by the RRC that barring has been relaxed, the NAS may initiate a service request (or SDT) procedure. Alternatively, the terminal (RRC) in which the timer operates may prevent/prohibit starting the RRC procedure for MO data transmission. Alternatively, while the timer is running, the UE (RRC) may prevent/prohibit starting any or specific RRC signaling procedure. In addition, the timer may be stopped/released when the cell reselection procedure or the RRC setup request message is transmitted or the RRC connection procedure is initiated.

In addition, the overload control operation may be performed in various ways.

For example, in general, the overload control is to prevent additional processing that may occur in the base station when the load on the base station is high. However, if data is to be transmitted through one transmission, such as a small amount of data transmission, subsequent data transmission may not be necessary. Accordingly, it is also possible for the base station to transmit data without having to instruct the terminal to reject it and to limit access after receiving a small amount of data.

Or, in general, the overload control is to prevent additional processing that may occur in the base station when the load on the base station is high. However, if data is to be transmitted through one transmission, such as a small amount of data transmission, subsequent data transmission may not be necessary. Accordingly, even when the base station instructs the terminal to reject/fail/restrict the SDT transmission request while receiving the small amount of data, the base station may transmit the received small amount of data to the destination through the core network. To this end, even when the terminal is instructed to reject/fail/restrict the SDT transmission request, the base station can perform a procedure for transmitting a small amount of data through the core network.

4. User data transmission on Msg 3/Msg A without RRC signaling and a successful response procedure

Hereinafter, a small amount of data transmission on Msg 3/Msg A without RRC signaling and a successful response procedure will be described. That is, the following describes a specific procedure in terms of transmitting a small amount of data by the terminal.

As a method for a terminal to process SDT, there may be a method of transparently processing SDT in the NAS and a method of separately processing SDT in the NAS. That is, some transmission operations may vary depending on whether the NAS performs an operation to distinguish SDTs. Hereinafter, a method of transparently processing SDT in the NAS and a method of processing separately and separately will be briefly described, and an embodiment of the overall terminal operation may be applied in the same manner.

First, the procedure/condition for triggering the SDT procedure in the upper layer will be described.

As an example, SDT may be triggered when an upper layer requests resumption of an RRC connection for mobile originated data. For example, the NAS (or 5GMM) of the terminal may be notified that an uplink user data packet is to be transmitted for a PDU session having a suspended user plane resource.

As another example, SDT may be triggered when an upper layer requests resumption of an RRC connection for mobile outgoing signaling or SMS. For example, the NAS of the terminal may want to perform mobile outgoing signaling. That is, the 5GMM of the terminal may receive a request to transmit a UL NAS TRANSPORT message for PDU session establishment/modification/reconfiguration, etc. from an upper layer. For another example, the NAS (or 5GMM) of the terminal may receive a request to send a mobile outgoing SMS over NAS from an upper layer. 5GMM initiates a NAS transport procedure to transmit SMS through UL NAS TRANSPORT message.

When the terminal (the terminal's NAS) detects one of the above events, the terminal (the terminal's NAS) must map the type of request to one or more access identifiers and one access category. In addition, the NAS indicates the access identifier and the access category as a lower layer (for example, AS (RRC)). The lower layer of the terminal performs an access baring check on the triggered request based on the determined access identifier and access category.

First, a case of transparently processing SDT in NAS will be described.

When the upper layer requests the resumption of the RRC connection, the RRC of the terminal checks the condition for SDT and may initiate the SDT when fulfilling this. This condition may be limited to the case where one or more of the following is satisfied.

-Receive information indicating SDT support/allowance in the cell through system information

-Receive parameters for SDT through system information or RRC-only message (e.g. RRC release)

-When the size of the resulting user data (e.g. MAC PDU) including the total uplink data is calculated/expected to be less than or equal to the signaled transport block size (TBS)/payload threshold size

-Does not receive SDT fallback indication information (e.g. fallback indication to the general RRC resume procedure) from the lower layer

-Receive OS Id + OS App Id of application information that triggered the access attempt from the upper layer

Next, an operation of distinguishing and processing SDTs in the NAS will be described.

In order for the upper layer to request the SDT separately, the upper layer may initiate the SDT if the condition for the SDT is checked and fulfilled. Related condition/instruction information may be transmitted to an upper layer through a lower layer (RRC). The indication information transmitted from the lower layer to the upper layer may include one or more of the following information.

-Information indicating SDT support/allowance in the cell received through system information

-Parameter for SDT received through system information or RRC-only message (e.g. RRC release)

-SDT fallback indication information received from a lower layer (e.g. a fallback instruction with a general RRC resumption procedure or an upper layer instructs a fallback with a request to resume an RRC connection for mobile originated data)

The upper layer may initiate SDT when the size of the resulting user data (e.g. MAC PDU) including the total uplink data is calculated/expected to be less than or equal to the signaled transport block size (TBS) size.

Meanwhile, the information indicating SDT support/allowance in the cell through system information includes information indicating SDT support/allowance through a 2-step random access procedure and information instructing SDT support/allowance through a 4-step random access procedure. Each can be indicated separately. The terminal may perform SDT by selecting one of SDT through a 2-step random access procedure and SDT through a 4-step random access procedure.

Here, the SDT parameter may include at least one of preamble information, security information, and TBS/payload threshold information. TBS is the TBS size for the PUSCH of MsgA for transmission without an RRC message or the total TBS size of MsgA or the TBS size for the user data included in the PUSCH of MsgA or the TBS size for the PUSCH of Msg3 or the total TBS size of Msg3 or Msg3 TBS size for user data included in may be indicated.

If the upper layer provides an access category and an access identifier when requesting to resume the RRC connection, the terminal (RRC) performs the aforementioned unified access control procedure. If the access attempt is barred, the terminal (the RRC of the terminal) informs the upper layer that the access attempt for the access category has been barred. The terminal (the RRC of the terminal) ends the SDT procedure. If the access attempt is allowed, the terminal (the terminal's RRC) informs the upper layer that the access attempt for the access category is allowed.

The terminal (the RRC of the terminal) indicates the SDT to the lower layer. For example, for SDT without RRC signaling, the terminal (the terminal's RRC) instructs the parameters to be transmitted to the base station through the SDT through the MAC (e.g. terminal temporary identifier, authentication token for integrity protection, reopening cause). In addition, the information indicated by MAD to distinguish and process the signaling includes at least one of RRC message type and RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. can do. The RRC transaction identifier is for identifying the corresponding RRC signaling transaction, and all uplink RRC messages requesting a direct DL response message include the RRC transaction identifier. Thereafter, when the MAC of the UE receives a response from the base station and delivers it to the RRC, the RRC message type, RRC transaction identifier, information for instructing the UE to maintain the RRC inactive state, or state transition to RRC idle At least one piece of information for indicating

SDT can be provided through a random access procedure. It may be provided through a 4-step RACH or a 2-step RACH. When provided through a two-step RACH, information indicating whether to support/provide a two-step RACH may be broadcast through a corresponding cell.

Next, user data transmission on Msg 3 without RRC signaling and a successful response indication method will be described.

When Msg3 is transmitted, the MAC entity of the UE performs contention resolution based on the C-RNTI on the PDCCH or the UE contention resolution identity on the DL-SCH. For this, the base station needs to transmit the UE contention resolution identity to the terminal. In addition, the base station may indicate confirmation/completion of SDT transmission. For example, when the base station wants to forward a NAS message including a small amount of data through the NGAP initial UE message procedure on the interface between the base station and the core network control plane entity (eg AMF), the base station confirms/completion of SDT transmission to the terminal. I can instruct. Alternatively, when the base station wants to forward a small amount of data through an interface between the base station and the core network user plane entity (e.g. UPF), the base station may instruct the terminal to confirm/complete SDT transmission. Or, when the base station sends a request message to the anchor base station to extract the terminal context and transmits a small amount of data through the core network entity, it instructs the terminal to confirm/complete SDT transmission. I can. Alternatively, the base station may indicate confirmation/completion of SDT transmission when receiving a response from a core network entity in response to a small amount of data transmission or when receiving downlink data from a core network entity. The base station may wish to indicate confirmation/completion in response to success of SDT transmission.

The indication information may include information for instructing the UE to maintain the RRC inactive state. If the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it can transmit it to the terminal. When the confirmation message for Msg3 is referred to as Msg4, Msg4 transmitted from the base station to the terminal is information for contention resolution, information for indicating confirmation/completion of successful transmission of SDT, and instructing the terminal to maintain the RRC inactive state. It may include at least one of information for, information for instructing to transition the terminal to the RRC idle state, and downlink data to be transmitted to the terminal. Information for instructing the UE to maintain the RRC inactive state and information for instructing the UE to transition to the RRC idle state may be indicated by different bits, respectively, or may be indicated by dividing two values by one bit.

For example, in order to transmit a small amount of data without RRC signaling, one or more of the above-described control information (or all control information) included in Msg4 may be divided into CCCH and transmitted. If a small amount of data is transmitted without RRC signaling, the RRC control parameters associated therewith may be considered to be all transmitted on the CCCH, assuming that the control channel is used without RRC connection. Msg 4 does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in RRC as one fixed-length MAC SDU. Through this, it is possible to reduce the overhead for configuring the RRC format/header.

For another example, one or more of the above-described control information (or all control information) included in Msg4 for transmission of small amount of data without RRC signaling may be divided into CCCH and transmitted. If a small amount of data is transmitted without RRC signaling, the RRC control parameters associated therewith may be considered to be all transmitted on the CCCH, assuming that the control channel is used without RRC connection. Msg 4 does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in RRC as one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. The corresponding MAC CE can be distinguished from the conventional DL CCCH type, and the LCID for the corresponding MAC SDU can have a value different from the LCID 0 value. One of the 33-46 LCID values currently reserved as spare status can be used.

For another example, for small data transmission without RRC signaling, if Msg4 includes small data, small data included in Msg4 may be included in a NAS container and separated by CCCH and transmitted. Alternatively, the small amount of data included in Msg4 may be included as an RRC information element and may be divided into CCCH and transmitted. If a small amount of data is transmitted without RRC signaling, user data that needs to be processed on the RRC associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without an RRC connection. Msg 4 does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in RRC as one fixed-length MAC SDU or MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a value different from LCID 0. One of the 33-46 LCID values currently reserved as spare status can be used.

As another example, one or more of the above-described one or more control information (or all control information) included in Msg4 and small amount data included in Msg4 (if Msg4 includes small amount data) for small data transmission without RRC signaling Information may be transmitted by being divided into DCCH. DCCH represents a point-to-point control channel used to transmit dedicated control information between one UE and a network (Dedicated Control Channel (DCCH): 　a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network.Used by UEs having an RRC connection).

When transmitting a small amount of data without RRC signaling through Msg3, if the RRC inactive terminal can restore the stored terminal context and resume SRB or DRB, the above information included in Msg4 is assumed to be a control channel used without RRC connection. It may be considered to be transmitted on the DCCH. Msg 4 does not configure the RRC message itself as a MAC SDU, but the information included as an information element in the conventional RRC message or the parameters controlled/used in the RRC or user data processed in the RRC are converted to one fixed-length MAC SDU or MAC CE. It can be composed and included. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used.

For another example, one or more of the aforementioned one or more control information (or all control information) included in Msg4 for transmission of small amount of data without RRC signaling and (if Msg4 includes small amount of data) one or more of the small amount of data included in Msg4 Information may be transmitted by being divided into DTCH. DTCH represents a point-to-point traffic channel used to transmit only user plane information between one terminal and a network (Dedicated Traffic Channel (DTCH): point-to-point channel, dedicated to one UE, for the transfer of user information. .A DTCH can exist in both uplink and downlink.).

When transmitting a small amount of data without RRC signaling, if the RRC inactive terminal recovers the stored terminal context, SRB or DRB can be resumed.If Msg4 contains small amount of data, the small amount of data included in Msg4 is transferred to the user plane traffic channel. Can be considered. In addition, for Msg B transmission without RRC connection, the aforementioned one or more control information (or all control information) is also multiplexed to the DTCH and transmitted, thereby further reducing overhead.

Information included as an information element in a conventional RRC message or parameters or user data controlled/used in the RRC may be configured and included in one fixed length MAC SDU or MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used. Alternatively, the LCID may use one of the logical channel identifiers 1 to 32 for user data. You can write the LCID for the DRB.

For another example, one or more of the aforementioned one or more control information (or all control information) included in Msg4 for transmission of small amount of data without RRC signaling and (if Msg4 includes small amount of data) one or more of the small amount of data included in Msg4 The information may be divided into MAC SDUs for MAC signaling and transmitted. For example, a new MAC CE may be defined to include the above-described information. If there are information elements to be classified and transmitted for user identification, content resolution, security processing, user data encryption, integrity protection, etc., they may be grouped and provided through the classified MAC CE.

When transmitting a small amount of data without RRC signaling, if the RRC inactive terminal can recover the stored terminal context and resume SRB or DRB, information included as an information element in the above-described conventional RRC message included in Msg4 or controlled by RRC / The used parameter or user data may be composed of one or more fixed-length MAC SDUs and/or one or more fixed-length MAC CEs. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used. Alternatively, the LCID of the MAC CE including user data among the corresponding MAC CEs may use one of the logical channel identifiers 1 to 32 for user data. You can write the LCID for the DRB.

As another example, Msg4 may be composed of a CCCH and a DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in Msg4 may be provided through the MAC SDU transmitted on the CCCH for signaling without RRC. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

For another example, Msg4 may consist of a MAC CE and a DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in Msg 4 may be provided through MAC CE for RRC-free signaling. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

For another example, Msg4 may include user data on the DTCH. The corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. Alternatively, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DCCH. Alternatively, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DTCH. For example, information for instructing the UE to maintain the RRC inactive state may be included with a fixed length field at a specific location. For another example, the corresponding MAC SDU may be provided through MAC CE. Through this, it is possible to indicate information or user data for instructing the UE to maintain the RRC inactive state without RRC signaling.

For another example, Msg4 may include information for indicating response/confirmation/completion of the successful transmission of the SDT. Information for indicating response/confirmation/completion of SDT transmission may be provided through MAC SDU/subPDU/PDU through MAC CE. Through this, information for indicating response/confirmation/completion of the successful transmission of SDT can be indicated without RRC signaling. Information for indicating the response/confirmation/completion of the SDT's successful transmission may be provided as one explicitly identified information element (field). Or, if the information for indicating the response/confirmation/completion of the SDT's successful transmission implicitly includes one information element (field) of the above-described control information, it is referred to as a response/confirmation/completion of the SDT's successful transmission. They may be instructed to recognize them separately.

For another example, Msg4 may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the CCCH. For another example, Msg4 may be transmitted without an RRC message. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. For another example, Msg4 may include user data on a DTCH multiplexed with MAC CE. For another example, the MAC SDU for the CCCH may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the MAC SDU for the CCCH may be virtually configured. Through this, user data can be transmitted without an RRC message.

For another example, control information included in Msg4 may be provided through one MAC CE. For example, information for contention resolution, information for indicating response/confirmation/completion of successful transmission of SDT, and information for instructing the terminal to maintain the RRC inactive state may be provided through one MAC CE. This can reduce the number of bits compared to including each MAC subheader.

As another example, Msg4 may include user data on the DTCH. The corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DCCH. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the DTCH. For example, information for instructing the UE to maintain the RRC inactive state may be included with a fixed length field at a specific location.

As another example, the corresponding MAC SDU may be provided through MAC CE. For another example, Msg4 may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. Through this, it is possible to instruct the UE to maintain the RRC inactive state without RRC signaling. For another example, Msg4 may include information for instructing the UE to maintain the RRC inactive state on the CCCH. For another example, Msg4 may be transmitted without an RRC message. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. For another example, Msg4 may include an RRC message on a CCCH and user data on a multiplexed DTCH. For another example, Msg4 may include user data on a DTCH multiplexed with MAC CE. In this case, the MAC SDU for the CCCH may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Alternatively, the MAC SDU for the CCCH may include terminal temporary identifier information in fixed bits. Through this, user data can be transmitted without an RRC message. For another example, the MAC CE may include terminal temporary identifier information.

As another example, in transmitting the SDT through Msg 3, in response to this, SDT transmission failure, SDT transmission rejection, SDT additional transmission restriction, information for indicating SDT retransmission restriction, general RRC connection for restricting transmission One or more of information, such as wait time, information for instructing the terminal to maintain the RRC inactive state, and information for contact resolution (or terminal identifier or terminal temporary identifier) may be included in the MAC subheader. have. The corresponding MAC subheader can be used by designating an arbitrary field value on the corresponding MAC subheader by utilizing the existing MAC subheader. Alternatively, a new MAC subheader format different from conventional NR MAC subheaders may be defined and used for the corresponding MAC subheader. Through this, the number of bits included in the MAC SDU can be reduced. In addition, the corresponding terminal/base station can distinguish and process the corresponding MAC SDU.

For another example, upon receiving Msg4, the UE may indicate that the RRC connection has been suspended to a higher layer. For example, the MAC entity may indicate information for instructing the UE to maintain the RRC inactive state to the RRC, and the RRC may indicate that the RRC connection is suspended to an upper layer (e.g. NAS). Accordingly, the upper layer can distinguish that it is in the RRC inactive state, and can perform the operation in the RRC inactive state. For another example, upon receiving Msg4, the UE may indicate to the upper layer that the SDT is completed.

The following describes the case of a two-step ramdon access procedure.

Next, user data transmission on Msg A without RRC signaling and a successful response indication method will be described.

For example, Msg A may include user data on the DTCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, Msg A may include user data on the CCCH. The corresponding MAC PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. The corresponding MAC PDU may include a terminal temporary identifier in a part of the data field. For another example, Msg A may be addressed (or masked with C-RNTI) through C-RNTI if the UE has a valid C-RNTI. For another example, Msg A may be addressed (or masked with a terminal temporary identifier) through the terminal temporary identifier. For another example, Msg A may include C-RNTI MAC CE on the CCCH. For another example, Msg A may include a MAC CE including a terminal temporary identifier on the CCCH.

For another example, Msg A may include user data on the CTCH. If user data is to be transmitted without an RRC message in the absence of an RRC connection, it is necessary to define a new type of logical channel for this. For example, a new type of logical channel for this can be defined as a CTCH (Common Traffic Channel) channel. The CTCH has a lower priority than the CCCH and a logical channel priority (LCP) procedure can be performed. Alternatively, a logical channel prioritization procedure may be performed for the CTCH with a lower priority than the MAC CE for C-RNTI. Alternatively, a logical channel prioritization procedure may be performed for the CTCH with the same or higher priority as the MAC CE for the C-RNTI.

For another example, MsgA may include an RRC request message in which user data is concatenated on the CCCH. In this case, user data may be included in the RRC message through the NAS information element (e.g. dedicatedInfoNAS). Alternatively, MsgA may include user data on a multiplexed DTCH with an RRC message on the CCCH. Alternatively, MsgA may include user data on a multiplexed DTCH with an RRC message on the CCCH. Alternatively, MsgA may include user data on the multiplexed DTCH with the MAC CE on the CCCH. For another example, the MAC CE on the CCCH included in Msg A consists of a fixed bit and may include terminal temporary identifier information. The CCCH SDU may consist of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Through this, user data can be transmitted without an RRC message. In this case, it is possible to perform LCP similar to the CTCH described above. In this case, it is possible to perform LCP similar to the CTCH described above. Alternatively, the CCCH SDU may include at least one of terminal temporary identifier information, authentication token (MAC-I), and shortMAC-I in a fixed bit.

When MsgA is transmitted, the MAC entity of the UE may perform contention resolution based on the UE contention resolution identity on the C-RNTI on the PDCCH or on the DL-SCH. The base station may want to instruct the terminal to maintain the RRC inactive state. For example, when the base station wants to forward a NAS message including a small amount of data through the NGAP initial UE message procedure on the interface between the base station and the core network control plane entity (eg AMF), the base station confirms/completion of SDT transmission to the terminal. I can instruct. Alternatively, when the base station wants to forward a small amount of data through an interface between the base station and the core network user plane entity (e.g. UPF), the base station may instruct the terminal to confirm/complete SDT transmission. Or, when the base station sends a request message to the anchor base station to extract the terminal context and transmits a small amount of data through the core network entity, it instructs the terminal to confirm/complete SDT transmission. I can. Alternatively, the base station may instruct the terminal to confirm/complete SDT transmission when receiving a response from a core network entity or downlink data from a core network entity in response to a small amount of data transmission. The base station may indicate confirmation/completion in response to success of SDT transmission. The indication information may include information for instructing the UE to maintain the RRC inactive state.

The base station may instruct the terminal to maintain the RRC inactive state. If the base station has downlink data to be transmitted for the corresponding terminal (if received from the core network), it can be transmitted to the terminal. When the response message to Msg A is Msg B, the MsgB transmitted by the base station to the terminal is information for indicating confirmation/completion of the successful transmission of SDT, information for instructing the terminal to maintain the RRC inactive state, and the terminal It may include at least one of downlink data to be transmitted for and information for instructing the terminal to transition to the RRC idle state. Information for instructing the UE to maintain the RRC inactive state and information for instructing the UE to transition to the RRC idle state may be indicated by different bits, respectively, or may be indicated by dividing two values with one bit.

For example, in order to transmit a small amount of data without RRC signaling, one or more of the above-described control information (or all control information) included in the MsgB may be divided into CCCH and transmitted. If a small amount of data is transmitted through the 2-step RACH without RRC signaling, the RRC control parameter associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without RRC connection. Msg B does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled/used in the RRC as one fixed-length MAC SDU. Through this, it is possible to reduce the overhead for configuring the RRC format/header.

For another example, one or more of the above-described control information (or all control information) included in the MsgB for small data transmission without RRC signaling may be divided into CCCH and transmitted. If a small amount of data is transmitted through the 2-step RACH without RRC signaling, the RRC control parameter associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without RRC connection. Msg B does not configure the RRC message itself as a MAC SDU, but may include information included as an information element in a conventional RRC message or a parameter controlled by RRC as one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. The corresponding MAC CE can be distinguished from the conventional DL CCCH type, and the LCID for the corresponding MAC SDU can have a value different from the LCID 0 value. One of the 33-46 LCID values currently reserved as spare status can be used.

For another example, for small data transmission without RRC signaling, if MsgB includes small data, small data included in MsgB may be included in a NAS container and separated by CCCH and transmitted. Alternatively, the small amount of data included in the MsgB may be included as an RRC information element, divided into CCCH, and transmitted. If a small amount of data is transmitted without RRC signaling through the 2-step RACH, user data that needs to be processed on the RRC associated thereto may be considered to be transmitted on the CCCH assuming that the control channel is used without RRC connection. Msg B does not configure the RRC message itself as a MAC SDU, but the information included as an information element in the conventional RRC message or the parameter controlled by the RRC or user data processed by the RRC is one fixed-length MAC SDU or one fixed-length MAC. It can be composed of CE and included. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a value different from LCID 0. One of the 33-46 LCID values currently reserved as spare status can be used.

For another example, one or more of the above-described control information (or all control information) included in the MsgB for small data transmission without RRC signaling, and the small amount of data included in the MsgB (if MsgB includes small data) It may be divided into DCCH and transmitted.

When transmitting a small amount of data without RRC signaling through a 2-step RACH, if the RRC inactive terminal can resume SRB or DRB by recovering the stored terminal context, the above-described information included in the MsgB is the control channel used without RRC connection. It can be considered to be transmitted on the DCCH assuming. Msg B does not configure the RRC message itself as a MAC SDU, but the information included as an information element in the conventional RRC message, parameters controlled/used in the RRC, or user data processed in the RRC, is one fixed-length MAC SDU or one fixed. It can be included by configuring the length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used.

For another example, one or more of the above-described control information (or all control information) included in the MsgB for small data transmission without RRC signaling, and the small amount of data included in the MsgB (if MsgB includes small data) It can be divided into DTCH and transmitted.

When transmitting a small amount of data without RRC signaling through a two-step RACH, if the RRC inactive terminal can restore the stored terminal context and resume SRB or DRB (if MsgB includes small amount of data), the small amount included in the MSgB Data can be considered as a user plane traffic channel. In addition, the base station may further reduce overhead by multiplexing and transmitting the above-described one or more control information (or all control information) in the DTCH for MsgB transmission without an RRC connection.

The base station may include information included as an information element in a conventional RRC message or a parameter or user data controlled/used in the RRC by configuring user data as one fixed-length MAC SDU or one fixed-length MAC CE. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used. Alternatively, the LCID may use one of the logical channel identifiers 1 to 32 for user data. You can write the LCID for the DRB.

For another example, one or more of the above-described control information (or all control information) included in the MsgB for small data transmission without RRC signaling, and the small amount of data included in the MsgB (if MsgB includes small data) It may be divided into MAC SDUs for MAC signaling and transmitted. For example, this information may be included in the new MAC CE and transmitted. If there are information elements to be classified and transmitted for user identification, contention resolution, security processing, user data encryption, integrity protection, etc., the base station may group them and provide them through the classified MAC CE. When transmitting a small amount of data without RRC signaling through the 2-step RACH, if the RRC inactive terminal can resume SRB or DRB by recovering the stored terminal context, it is included as an information element in the aforementioned conventional RRC message included in MsgB. Information or parameters controlled/used in RRC or user data may be configured and included in one or more fixed-length MAC SDUs and/or one or more fixed-length MAC CEs. Through this, it is possible to reduce the overhead for configuring the RRC format/header. In addition, overhead for subheader addition may be reduced compared to dividing each information into MAC SDUs. The LCID for the corresponding MAC SDU or MAC CE can have a specific value. For example, one of the 33-46 LCID values currently reserved as spare can be used. Alternatively, the LCID of the MAC CE including user data among the corresponding MAC CEs may use one of the logical channel identifiers 1 to 32 for user data. You can write the LCID for the DRB.

For another example, the MsgB may consist of a CCCH and a DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in the MsgB may be provided through a MAC SDU transmitted on the CCCH for signaling without RRC. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

For another example, the MsgB may consist of a MAC CE and a DTCH multiplexed thereto. One or more of the above-described control information (or all control information) included in the MsgB may be provided through the MAC CE for signaling without RRC. A small amount of data may be transmitted through the DTCH multiplexed thereto. Accordingly, a small amount of data may be provided through a MAC SDU having a separate subheader to distinguish it.

For another example, MsgB may include user data on the DTCH. The corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DCCH. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DTCH. For example, information for instructing the UE to maintain the RRC inactive state may be included with a fixed length field at a specific location. For another example, the corresponding MAC SDU may be provided through MAC CE. Through this, information for instructing the UE to maintain the RRC inactive state without RRC signaling can be indicated.

For another example, MsgB may include information for indicating response/confirmation/completion of the successful transmission of the SDT. The corresponding MAC SDU/subPDU/PDU may be provided through MAC CE. Through this, information for indicating response/confirmation/completion of the successful transmission of SDT can be indicated without RRC signaling. Information for indicating the response/confirmation/completion of the SDT's successful transmission may be provided as one explicitly identified information element (field). Or, if the information for indicating the response/confirmation/completion of the SDT's successful transmission implicitly includes one of the above-described control information, it is classified into response/confirmation/completion of the SDT's successful transmission. You may be instructed to be aware of it.

For another example, the MsgB may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the CCCH. For another example, MsgB may be transmitted without an RRC message. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include user data on the DTCH multiplexed with the MAC CE. For another example, the MAC SDU for the CCCH may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the MAC SDU for the CCCH may be virtually configured. Through this, the base station can transmit user data without an RRC message. For another example, control information included in MsgB may be provided through one MAC CE. For example, information for contention resolution, information for indicating response/confirmation/completion of successful transmission of SDT, and information for instructing the terminal to maintain the RRC inactive state may be provided through one MAC CE. This can reduce the number of bits compared to including each MAC subheader.

For another example, MsgB may include user data on the DTCH. The corresponding MAC SDU/subPDU/PDU may include a logical channel identifier of the corresponding user data in the MAC header/subheader. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DCCH. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the DTCH. For example, information for instructing the UE to maintain the RRC inactive state may be included with a fixed length field at a specific location.

For another example, the corresponding MAC SDU may be provided through MAC CE. For another example, the MsgB may provide information for instructing the UE to maintain the RRC inactive state through the MAC CE. Through this, the base station may indicate information for instructing the terminal to maintain the RRC inactive state without RRC signaling. For another example, the MsgB may include information for instructing the UE to maintain the RRC inactive state on the CCCH. For another example, MsgB may be transmitted without an RRC message. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include the RRC message on the CCCH and user data on the multiplexed DTCH. For another example, the MsgB may include user data on the DTCH multiplexed with the MAC CE. In this case, the MAC SDU for the CCCH may be composed of 0 bits (or a fixed bit or a zero length octet string). Alternatively, the CCCH SDU may be configured virtually. Alternatively, the MAC SDU for the CCCH may include terminal temporary identifier information in fixed bits. Through this, the base station can transmit user data without an RRC message. For another example, the MAC CE may include terminal temporary identifier information.

For another example, in transmitting SDT through Msg A, in response to this, SDT transmission failure, SDT transmission rejection, SDT additional transmission limitation, information for indicating SDT retransmission limitation, information for limiting transmission of a general RRC connection, At least one of information for a waiting time, information for instructing the UE to maintain the RRC inactive state, and information for contact resolution (or a terminal identifier or a terminal temporary identifier) may be included in the MAC subheader. The corresponding MAC subheader can use the existing MAC subheader by designating the corresponding MAC subheader as an arbitrary field value. Alternatively, the corresponding MAC subheader may define and use a new MAC subheader format that is differentiated from conventional NR MAC subheaders. Through this, the number of bits included in the MAC SDU can be reduced. In addition, the corresponding terminal/base station can distinguish and process the corresponding MAC SDU.

For another example, upon receiving the MsgB, the UE may indicate that the RRC connection has been suspended to a higher layer. For example, the MAC entity may indicate information for instructing the UE to maintain the RRC inactive state to the RRC, and the RRC may indicate that the RRC connection is suspended to an upper layer (e.g. NAS). Accordingly, the upper layer can distinguish that it is in the RRC inactive state, and can perform the operation in the RRC inactive state. For another example, upon receiving the MsgB, the terminal may indicate to the upper layer that the SDT is completed.

For convenience of explanation, the above-described embodiments of the present disclosure have described a method of transmitting a small amount of data in a MAC PDU without an RRC, but transmitting small amount of data in an arbitrary Layer2 PDU is included in the scope of the present disclosure. do. For example, it may be included in the RLC PDU and PDCP PDU, and in this case, the MAC CE may be replaced by the RLC control PDU and PDCP control PDU.

As described above, the present disclosure provides the effect that the base station can efficiently control overload when transmitting a small amount of data without an RRC connection. Hereinafter, configurations of a terminal and a base station in which the above-described embodiment according to the present disclosure can be performed will be described with reference to the drawings.

18 is a diagram for describing a configuration of a terminal according to an embodiment.

Referring to FIG. 18, a terminal 1800 for controlling a small amount of data load uses a control unit 1810 for triggering a small amount of data transmission in an RRC inactive state and Msg 3 or Msg A including small amount of data as a base station. It includes a transmitting unit 1820 for transmitting and a receiving unit 1830 for receiving Msg 4 or Msg B including information for overload control from the base station.

For example, the terminal 1800 in the RRC inactive state or the RRC idle state may trigger a small amount of data transmission in an upper layer. For example, the terminal 1800 in the RRC inactive state or the RRC idle state may trigger a small amount of data transmission in the NAS layer. In this case, the NAS layer may instruct the RRC connection resumption request to the lower layer. As another example, the MAC entity may acquire small amount of data transmission indication information through Msg 3 (Message 3) or Msg A (Message A) based on the RRC connection resumption request. That is, the controller 1810 may instruct the MAC layer to transmit a small amount of data through Msg3 or MsgA when an RRC connection resumption request is indicated to a lower layer from the NAS layer. To this end, the MAC layer may receive indication information indicating Msg3 or MsgA transmission from a higher MAC layer.

On the other hand, the small amount of data transmission indication information through Msg3 or MsgA may further include at least one of RRC message type, RRC transaction identifier, terminal temporary identifier, authentication token for integrity protection, and reopening cause information. have.

In addition, when Msg3 or MsgA transmission is determined based on the small amount of data transmission instruction information through Msg3 or MsgA, the transmitter 1820 may transmit Msg3 or MsgA to the base station. Msg 3 or Msg A may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a cause of reopening in the MAC CE. For example, Msg 3 or Msg A for small data transmission may not include an RRC message.

Meanwhile, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

On the other hand, Msg 4 or Msg B fails to transmit Msg 3 or Msg A containing a small amount of data in the MAC CE or MAC RAR or MAC subheader, rejects transmission of Msg 3 or Msg A including the small amount of data, rejects RRC connection , It may include at least one of information indicating a fallback random access response and waiting time information.

For example, Msg 4 or Msg B may include information indicating that a small amount of data transmitted by the terminal is rejected by the base station or that transmission has failed. Transmission failure information of Msg 3 or Msg A, transmission rejection information of Msg 3 or Msg A including the small amount of data, and RRC connection rejection information indicate that Msg 3 or Msg A transmitted by the terminal to the base station was not successfully delivered. Instruct. In addition, the waiting time information may indicate a predetermined waiting time for RRC connection or small data transmission requested by the base station to the terminal. The above-described information may be included in the MAC CE or MAC RAR or MAC subheader of Msg 4 or Msg B and received.

On the other hand, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle. That is, the base station may receive Msg 4 or MsgB and instruct the RRC state of the UE to not change unnecessary. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The above-described MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and received by the UE.

When Msg 4 or Msg B is received, the controller 1810 may transmit information included in Msg 4 or Msg B to the RRC layer. The RRC layer can deliver the information to the NAS layer. For example, the controller 1810 transmits the indication information on the above-described small data transmission failure or the RRC state of the terminal to the Non-Access Stratum (NAS) layer through the MAC entity. The NAS layer may recognize whether a small amount of data is transmitted or whether the terminal is instructed to change the state through the transmitted information.

On the other hand, when the transmission unit 1820 includes a small amount of data in Msg A and transmits it through a two-step random access procedure, the reception unit 1830 receives Msg B from the base station. As described above, the information for overload control may include at least one of transmission failure of Msg 3 or Msg A, transmission rejection of Msg 3 or Msg A including a small amount of data, RRC connection rejection, and latency information. . In addition, information indicating a fallback random access response to information for overload control may be included. When the information for overload control is included in Msg B, the transmitter 1830 may retransmit Msg 3 including a small amount of data after receiving the corresponding Msg B. That is, the terminal 1800 receives information for overload control of the base station, and transmits Msg 3 when the information for overload control indicates a fallback random access response. Through this, the terminal 1800 may transmit a small amount of data by changing the random access procedure from the 2-step random access procedure to the 4-step random access procedure.

In addition to this, the controller 1810 controls the overall operation of the terminal 1800 according to the procedure for transmitting a small amount of data and overload control required to perform the above-described embodiments.

The transmitting unit 1820 and the receiving unit 1830 are used to transmit and receive signals, messages, and data necessary for carrying out the above-described embodiments with the base station.

19 is a diagram illustrating a configuration of a base station according to an embodiment.

Referring to FIG. 19, a base station 1900 for controlling a small amount of data load receives a receiving unit 1930 for receiving Msg 3 or Msg A including a small amount of data from a terminal in an RRC inactive state and a small amount of data. It may include a control unit 1910 that generates information for overload control based on availability and a transmitter 1920 that transmits Msg 4 or Msg B including information for overload control to the terminal.

When a small amount of data transmission is triggered by the terminal, the receiving unit 1930 receives Msg 3 or Msg A including small amount of data. For example, Msg 3 or Msg A may include at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening. In addition, Msg 3 or Msg A may not include an RRC message. Here, the terminal temporary identifier may be composed of bits of a specific part of I-RNTI (Inactive-Radio Network Temporary Identity) or I-RNTI. For example, the specific part of the I-RNTI may mean only the bits of the part for identifying the UE context in the corresponding base station except for the base station part in the I-RNTI. Alternatively, the specific part of the I-RNTI may mean a bit of a part that is set in advance to identify the terminal or the terminal context between the terminal and the base station. Accordingly, the bits of the specific part of the I-RNTI may be determined as a few high or low bits of the I-RNTI.

For example, the controller 1910 may generate information for overload control based on load information of the base station. Information for overload control may be generated for each random access message of the terminal. For example, the information for overload control is at least one of transmission failure of Msg 3 or Msg A including small amount of data, transmission rejection of Msg 3 or Msg A including small amount of data, RRC connection rejection, and latency information. It may include. That is, the information for overload control may include indication information for processing when the base station 1900 cannot receive Msg 3 or Msg A of the terminal. Alternatively, the information for overload control may include information indicating a fallback random access response.

Meanwhile, the receiving unit 1930 may successfully receive Msg 3 or Msg A including small amount of data of the terminal. For example, the receiving unit 1930 checks Msg 3 or Msg A received from the terminal and receives a small amount of data.

The transmitter 1920 may include the above-described information for overload control in the MAC CE or MAC RAR or MAC subheader of Msg 4 or Msg B and transmit the information to the terminal. For example, when a small amount of data is received through Msg A and information for overload control is transmitted through Msg B, if the information for overload control includes information indicating a fallback random access response, the receiving unit 1930 May further receive Msg 3 including a small amount of data after Msg B transmission. That is, when receiving a small amount of data through a 2-step random access procedure, the control unit 1910 may instruct a fallback random access response to the terminal for overload control. When the fallback random access response is instructed, the UE changes the procedure to a 4-step random access procedure and transmits a small amount of data in Msg 3 to the base station.

Meanwhile, when the base station is capable of receiving a small amount of data and receives it, the transmitter 1920 may transmit Msg 4 or Msg B including the following information.

For example, Msg 4 or Msg B may include information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle. That is, the transmission unit 1920 may instruct not to cause unnecessary RRC state change of the terminal through Msg 4 or MsgB. For example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC idle may be included in the MAC CE. As another example, information for indicating maintenance of the RRC inactive state of the terminal or information for indicating a state transition to RRC idle may be included in the MAC RAR. As another example, information for indicating maintenance of the RRC inactive state of the UE or information for indicating a state transition to RRC Idle may be included in the MAC subheader. The aforementioned MAC CE or MAC RAR or MAC subheader may be included in Msg 4 or MsgB and transmitted to the terminal.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP and 3GPP2 wireless access systems. That is, steps, configurations, and parts not described in order to clearly reveal the present technical idea among the embodiments may be supported by the aforementioned standard documents. In addition, all terms disclosed in the present specification can be described by the standard documents disclosed above.

The above-described embodiments can be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to the embodiments includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), and FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller, or a microprocessor.

In the case of implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor through various known means.

In addition, terms such as "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. It may mean a combination of, software, or running software. For example, the above-described components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and/or a computer. For example, an application running on a controller or processor and a controller or processor can both be components. One or more components may reside within a process and/or thread of execution, and the components may be located on a single device (eg, a system, a computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and those of ordinary skill in the technical field to which the present disclosure pertains will be able to make various modifications and variations without departing from the essential characteristics of the technical idea. In addition, the present embodiments are not intended to limit the technical idea of the present disclosure, but to explain the technical idea, and thus the scope of the technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present disclosure.

Claims (15)

1. In the method for the terminal to control a small amount of data load,

   Triggering a small amount of data transmission in an RRC inactive state;

   Transmitting Msg 3 or Msg A including the small amount of data to a base station; And

   Receiving from the base station Msg 4 or Msg B including information for overload control.
2. The method of claim 1,

   The Msg 3 or Msg A,

   A method including at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening in the MAC CE.
3. The method of claim 1,

   The Msg 4 or Msg B,

   At least one of transmission failure of Msg 3 or Msg A including the small amount of data in MAC CE or MAC RAR or MAC subheader, transmission rejection of Msg 3 or Msg A including the small amount of data, RRC connection rejection and latency information How to include the information.
4. The method of claim 1,

   When the small amount of data is transmitted to the base station through Msg A and Msg B is received from the base station,

   If the information for overload control of Msg B includes information indicating a fallback random access response,

   After receiving the Msg B, the method of further transmitting Msg 3 including the small amount of data.
5. The method of claim 1,

   Information contained in the Msg 4 or Msg B,

   Method characterized in that delivered to the RRC layer.
6. In a method for a base station to control a small amount of data load,

   Receiving Msg 3 or Msg A including a small amount of data from a terminal in an RRC inactive state;

   Generating information for overload control based on whether the small amount of data can be received; And

   A method comprising the step of transmitting Msg 4 or Msg B including information for the overload control to the terminal.
7. The method of claim 6,

   The Msg 3 or Msg A,

   A method including at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening in the MAC CE.
8. The method of claim 6,

   Information for the overload control,

   A method comprising at least one of transmission failure of Msg 3 or Msg A including the small amount of data, transmission rejection of Msg 3 or Msg A including the small amount of data, RRC connection rejection, and waiting time information.
9. The method of claim 8,

   Information for the overload control,

   The method included in the MAC CE or MAC RAR or MAC subheader of Msg 4 or Msg B.
10. The method of claim 6,

    When the small amount of data is received through the Msg A and the information for the overload control is transmitted through the Msg B,

    If the information for the overload control includes information indicating a fallback random access response,

    A method of further receiving Msg 3 including the small amount of data after the Msg B transmission.
11. In a terminal controlling a small amount of data load,

    A control unit for triggering a small amount of data transmission in an RRC inactive state;

    A transmitter for transmitting Msg 3 or Msg A including the small amount of data to a base station; And

    Terminal comprising a receiving unit for receiving from the base station Msg 4 or Msg B including information for overload control.
12. The method of claim 11,

    The Msg 3 or Msg A,

    A terminal including at least one of a terminal temporary identifier, an authentication token for integrity protection, and a reason for reopening in the MAC CE.
13. The method of claim 11,

    The Msg 4 or Msg B,

    At least one of transmission failure of Msg 3 or Msg A including the small amount of data in MAC CE or MAC RAR or MAC subheader, transmission rejection of Msg 3 or Msg A including the small amount of data, RRC connection rejection and latency information Terminal containing information of.
14. The method of claim 11,

    When the small amount of data is transmitted to the base station through Msg A and Msg B is received from the base station,

    If the information for overload control of Msg B includes information indicating a fallback random access response,

    After receiving the Msg B, the transmission unit further transmits Msg 3 including the small amount of data.
15. The method of claim 11,

    The control unit,

    A terminal, characterized in that the information included in Msg 4 or Msg B is transmitted to the RRC layer.

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