CN116762468A - Method and apparatus for supporting small data transmission in a wireless communication system - Google Patents

Abstract

The present disclosure relates to a communication method and system that converges support for fifth generation (5G) communication systems that exceed the higher data rates of fourth generation (4G) systems with internet of things (IoT) technology. The present disclosure is applicable to smart services based on 5G communication technology and IoT-related technology, such as smart homes, smart buildings, smart cities, smart cars, connected cars, healthcare, digital education, smart retail, security and security services. There is provided a method of a base station of a wireless communication system, the method comprising: receiving a Radio Resource Control (RRC) message including uplink data from a user equipment (INACTIVE) in an INACTIVE mode to a Distributed Unit (DU) of a base station; transmitting a first message from the DU to a centralized unit control plane (CU-CP) of the base station, the first message including at least one of indicator information related to transmission of uplink data and identification information of a Data Radio Bearer (DRB) corresponding to the uplink data; based on the first message, uplink data is sent to the user plane function UPF.

Description

Method and apparatus for supporting small data transmission in a wireless communication system

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for supporting small data transmission in a wireless communication system.

Background

In order to meet the increasing demand for wireless data services since the deployment of 4G communication systems, efforts have been made to develop improved 5G or quasi 5G communication systems. Therefore, a 5G or quasi 5G communication system is also referred to as a "post 4G network" or a "post LTE system". A 5G communication system is considered to be implemented in a higher frequency (millimeter wave) band, for example, a 60GHz band, in order to achieve a higher data rate. In order to reduce propagation loss of radio waves and increase transmission distance, in 5G communication systems, beamforming, massive Multiple Input Multiple Output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, massive antenna techniques are discussed. Further, in the 5G communication system, development of system network improvement based on advanced small cell, cloud Radio Access Network (RAN), ultra dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, coordinated multipoint (CoMP), reception-side interference cancellation, and the like is underway. In 5G systems, hybrid FSK and QAM modulation (FQAM) and Sliding Window Superposition Coding (SWSC) have been developed as Advanced Coding Modulation (ACM), and Filter Bank Multicarrier (FBMC), non-orthogonal multiple access (NOMA) and Sparse Code Multiple Access (SCMA) as advanced access techniques.

The internet is now evolving to the internet of things (IoT) as a human-centric connectivity network for human generation and consumption of information, wherein distributed entities (e.g., things) exchange and process information without human intervention. Internet of everything interconnect (IoE) is the internet where IoT technology and big data processing technology are combined together through a connection with a cloud server. Technical elements such as "sensing technology", "wired/wireless communication and network infrastructure", "service interface technology" and "security technology" have recently been studied for IoT implementations, sensor networks, machine-to-machine (M2M) communications, machine Type Communications (MTC), etc. Such IoT environments may provide intelligent internet technology services that create new value for human life by collecting and analyzing data generated between connected things. Through the fusion and combination between existing Information Technology (IT) and various industrial applications, IT can be applied to various fields including smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart devices and advanced medical services.

In keeping with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, techniques such as sensor networks, machine Type Communications (MTC), and machine-to-machine (M2M) communications may be implemented by beamforming, MIMO, and array antennas. Application of the cloud Radio Access Network (RAN) as the big data processing technology described above can also be regarded as an example of fusion between the 5G technology and the IOT technology.

According to recent developments in 5G communication systems, a method of transmitting and receiving relatively small data more efficiently is required. In particular, a method of minimizing unnecessary delay in small data transmission and reception between a separate base station (separate gNB) and a UE in a 5G communication system has emerged.

Disclosure of Invention

Technical problem

According to a general data transmission and reception method, in order to transmit and receive data to and from a Base Station (BS), a UE in an active mode needs to be switched to a connected mode. Therefore, even when the UE in the inactive mode transmits and receives relatively small data, the UE switches to the connected mode each time, and thus unnecessary delay may be generated due to a signaling procedure for switching between the radio access states.

Technical proposal

In accordance with an embodiment of the present disclosure to solve the above-described problems, a method of a Base Station (BS) in a wireless communication system includes: receiving, by a Distributed Unit (DU) of a BS, a Radio Resource Control (RRC) message including uplink data from a User Equipment (UE) in an inactive mode; a first message including at least one indicator information related to transmission of uplink data and identification information of a Data Radio Bearer (DRB) corresponding to the uplink data is transmitted to a DU-to-BS centralized unit control plane (CU-CP), and the uplink data is transmitted to a User Plane Function (UPF) based on the first message.

According to another embodiment of the present disclosure, in order to solve the above-described problem, a Base Station (BS) in a wireless communication system includes a transceiver, and a controller configured to control the transceiver to receive a Radio Resource Control (RRC) message including uplink data from a User Equipment (UE) in an inactive mode through a Distributed Unit (DU) of the BS, transmit a first message by the DU, the first message including at least one indicator information related to transmission of the uplink data and identification information of a Data Radio Bearer (DRB) corresponding to a centralized unit control plane (CU-CP) of the BS, and transmit the uplink data to a User Plane Function (UPF) based on the first message.

Advantageous effects of the invention

According to embodiments of the present disclosure, a UE in an inactive mode may transmit and receive relatively small data to and from an aggregated base station (aggregated gNB) or a separate base station (separate gNB) without switching to a connected mode. Thus, unnecessary delays that may be generated by the transmission or reception of small data can be resolved.

Drawings

Fig. 1 shows an example of the structure of a next-generation mobile communication system;

Fig. 2 shows a radio protocol structure of a next generation mobile communication system;

fig. 3 illustrates a transition of a radio access state in a next generation mobile communication system according to an embodiment of the present disclosure;

fig. 4 is a sequence diagram illustrating a procedure in which a UE accessing a detached base station (detached gNB) is switched to an inactive radio access state in a next generation mobile communication system according to an embodiment of the present disclosure;

fig. 5 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure and tunnel configuration of a detached base station (detached gNB) supporting the method according to the first embodiment of the present disclosure;

fig. 6 is a sequence diagram showing an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to the first embodiment of the present disclosure;

fig. 7 shows a message and an Information Element (IE) according to a first embodiment of the invention;

fig. 8 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure of a detach base station (detach gNB) supporting a method according to a second embodiment of the present disclosure;

fig. 9A is a sequence diagram showing an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to the second embodiment of the present disclosure;

Fig. 9B is a sequence diagram illustrating an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to a second embodiment of the present disclosure;

fig. 10A shows a message and Information Element (IE) according to a second embodiment of the present disclosure;

fig. 10B shows a message and Information Element (IE) according to a second embodiment of the present disclosure;

fig. 10C illustrates a message and Information Element (IE) according to a second embodiment of the present disclosure;

fig. 10D shows a message and Information Element (IE) according to a second embodiment of the present disclosure;

fig. 11 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure of a detached base station (detached gNB) supporting the method according to the third embodiment of the present disclosure;

fig. 12 is a sequence diagram illustrating an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to a third embodiment of the present disclosure;

fig. 13 illustrates a structure of a UE according to an embodiment of the present disclosure;

fig. 14 illustrates a structure of a BS according to an embodiment of the present disclosure.

Detailed Description

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

In describing embodiments of the present disclosure, descriptions related to technical contents well known in the art and not directly associated with the present disclosure will be omitted. This unnecessary description is omitted for the purpose of preventing confusion and more clear transfer of the main idea of the present disclosure.

For the same reasons, some elements may be enlarged, omitted, or schematically shown in the drawings. Furthermore, the size of each element does not fully reflect the actual size. In the drawings, identical or corresponding elements have identical reference numerals.

The advantages and features of the present disclosure and the manner of attaining them will become apparent by reference to the embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments set forth below, but may be implemented in various forms. The following examples are provided solely for the purpose of fully disclosing the present disclosure and informing those skilled in the art the scope of the present disclosure and are limited only by the scope of the appended claims. Throughout the specification, the same or similar reference numerals denote the same or similar elements.

Here, it will be understood that each block of the flowchart, and combinations of blocks in the flowchart, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer-usable or computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-usable or computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

Furthermore, each block of the flowchart illustrations may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the block may occur out of the order. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

In the following description, for convenience, terms that identify access nodes, terms that relate to network entities, terms that relate to messages, terms that relate to interfaces between network entities, terms that relate to various identification information, etc., are exemplarily used. Accordingly, the present disclosure is not limited by the terms used below, and other terms relating to the subject matter having the equivalent technical meaning may be used.

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

That is, the following detailed description of embodiments of the present disclosure will be directed mainly to the communication standard defined by 3 GPP. However, based on the determination by those skilled in the art, the main idea of the present disclosure may also be applied to other communication systems having similar technical backgrounds through some modifications without significantly departing from the scope of the present disclosure.

Fig. 1 shows an example of a structure of a next-generation mobile communication system. That is, fig. 1 shows an example of a next-generation mobile communication system structure to which the embodiments of the present disclosure can be applied.

Referring to fig. 1, radio Access Network (RAN) nodes 1-100 and 1-200 of the structure may be mobile communication Base Stations (BSs), such as LTE evolved node BS (enodebs), or next generation node BS (NR gbbs) connected to a mobile communication Core Network (CN), such as Evolved Packet Core (EPC) or 5G core network (5 GC) 1-400. Furthermore, the RAN nodes 1-100 and 1-200 may be divided into a Centralized Unit (CU) and a Distributed Unit (DU), and the CU may be divided into a CU Control Plane (CP) and a CU User Plane (UP).

According to an embodiment, the RAN node may comprise one or more CU-CPs, one or more CU-UP and one or more DUs. Further, CU-CP, CU-UP and DU included in the RAN node may be configured together. For example, the RAN node may include a CU and a DU, where the CU-CP and CU-UP are configured together in the CU. In another example, the CU-CP and DU may be configured together in the RAN node and the CU-UP may be configured separately therein. In another example, the RAN node may be configured in the form of an aggregated base station (aggregated gNB), where CU-CP, CU-UP, and DU are configured together. The RAN node may be configured by another combination and example as described above.

According to one embodiment, the CUs and DUs may support BS functions separately. For example, a CU may support the RRC/PDCP layer, while a DU may support the RLC/MAC/PHY/RF layer. Furthermore, the CU and DU may be connected by an interface between functions within the BS, such as a W1 or F1 interface.

According to one embodiment, CUs may be divided into CU-CPs and CU-CPs. For example, a CU-CP may support an RRC/PDCU (for RRC) layer, a CU-UP may support a PDCP (for user data transfer) layer, and the CU-CP and the CU-UP may be connected through an interface between functions within the BS, such as an E1 interface.

According to one embodiment, the BS may be configured in an aggregation structure or a partition structure, and a connection between aggregation base stations (aggregation gbbs), a connection between partition base stations (partition gbbs), and a connection between aggregation base stations (aggregation gbb) and partition base stations (partition gbb) are possible. The RAN nodes may be connected via an inter-BS interface such as an X2 or Xn interface. Furthermore, the RAN node and the core network may be connected through an interface between the BS and the core network, such as an S1 or NG interface. The method proposed in the present disclosure may be applied to a case in which the UE 1-300 is connected to the RAN node in a state of maintaining an INACTIVE (rrc_inactive) radio access state and transmits small data regardless of an aggregation base station (aggregation gNB) or a separate base station (separation gNB).

Fig. 2 shows a radio protocol structure in a next generation mobile communication system. That is, fig. 2 illustrates a radio protocol structure of a next-generation mobile communication system to which the embodiments of the present disclosure can be applied.

Referring to fig. 2, radio protocols of the next generation communication system may include Service Data Adaptation Protocols (SDAPS) 2-01 and 2-45, NR PDCP 2-05 and 2-40, NR RLC 2-10 and 2-35, NR MAC 2-15 and 2-30, and NR PHY 2-20 and 2-25 in UEs and NR BSs (e.g., NR gnbs).

The primary functions of NR SDAPS 2-01 and 2-45 may include some of the following functions.

User data transfer function (transfer of user plane data)

Mapping the QoS flows and data bearers of the uplink and downlink (mapping between DL and UL QoS flows and DRBs)

Function of marking QoS flow IDs for uplink and downlink (marking QoS flow IDs in DL and UL packets)

Function of mapping the reflected QoS flow to the data bearer of the uplink SDAP PDU (mapping the reflected QoS flow to the DRB of the UL SDAP PDU)

For the SDAP layer (or SDAP layer device), the UE may receive a configuration indicating whether to use a header of the SDAP layer device or a function of the SDAP layer device for each PDCP layer device, each bearer, or a logical channel through a Radio Resource Control (RRC) message. When configuring the SDAP header, the UE may indicate updating or reconfiguration of mapping information for uplink and downlink QoS flows and data bearers by a non-access stratum (NAS) quality of service (QoS) reflection configuration 1 bit indicator (NAS reflection QoS) and an Access Stratum (AS) QoS reflection configuration 1 bit indicator (AS reflection QoS) of the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. QoS information can be used as data processing priority and scheduling information to smoothly support services.

The main functions of NR PDCP 2-05 and 2-40 can include some of the following functions.

Header compression and decompression function (header compression and decompression: ROHC only)

User data transfer function (transfer of user data)

Sequential delivery function (sequential delivery of upper layer PDUs)

Non-sequential delivery function (unordered delivery of upper layer PDUs)

Reordering function (received PDCP PDU reordering)

Duplicate detection function (duplicate detection of lower layer SDU)

Retransmission function (retransmission of PDCP SDU)

Encryption and decryption functions (encryption and decryption)

Timer-based SDU removal function (timer-based SDU discard in uplink)

In the above example, the reordering function of the NR PDCP device is a function of sequentially reordering PDCP PDUs received by a lower layer based on PDCP Sequence Numbers (SNs). The reordering function of the NR PDCP layer may include a function of sequentially transferring reordered data to a higher layer. Alternatively, the recording function of the NR PDCP may include a function of directly transmitting data regardless of a sequence. Further, the recording function of the NR PDCP may include a function of reordering sequences and recording lost PDCP PDUs, a function of transmitting a status report on the lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of the lost PDCP PDUs.

The primary functions of NR RLCs 2-10 and 2-35 may include some of the following functions.

Data transfer function (transfer of upper layer PDU)

Sequential delivery function (sequential delivery of upper layer PDUs)

Non-sequential delivery function (unordered delivery of upper layer PDUs)

ARQ function (error correction by ARQ)

Concatenation, segmentation and reassembly functions (concatenation, segmentation and reassembly of RLC SDUs)

Repartitioning function (repartitioning of RLC data PDUs)

Reordering function (reordering of RLC data PDUs)

-repetition detection function (repetition detection)

Error detection function (protocol error detection)

RLC SDU discard function (RLC SDU discard)

RLC re-establishment function (RLC re-establishment)

In the above description, the sequential delivery function (in-order delivery) of the NR RLC device may be a function of sequentially delivering RLC SDUs received from a lower layer to a higher layer. When one RLC SDU is divided into a plurality of RLC SDUs and received, the sequence delivery function (in-sequence delivery) of the NR RLC device may include a function of reassembling and then transmitting the RLC SDUs.

The sequence delivery function (in-sequence delivery) of the NR RLC device may include a function of reordering received RLC PDUs based on RLC Sequence Numbers (SNs) or PDCP Sequence Numbers (SNs). Further, the sequence delivery function of the NR RLC device may include a function of recording a sequence and recording missing RLC PDUs. Further, the sequence delivery function of the NR RLC device may include a function of transmitting a status report on a missing RLC PDU to the transmitting side and a function of requesting retransmission of the missing RLC PDU.

The sequence delivery function (in-sequence delivery) of the NR RLC device may include the following functions if there is a missing RLC SDU: only RLC SDUs preceding the missing RLC SDU are sequentially delivered to higher layers.

The sequence transfer function (in-sequence transfer) of the NR RLC device may include such functions as: if the predetermined timer expires, all RLC SDUs received before the timer starts are sequentially delivered to higher layers even if there are missing RLC SDUs.

The sequential delivery function (in-order delivery) of the NR RLC device may include a function of sequentially delivering all RLC SDUs received up to now to a higher layer if a predetermined timer expires even if there is a missing RLC SDU.

The NR RLC device can sequentially process RLC PDUs in the order of reception without considering sequence numbers (out-of-sequence delivery), and deliver the RLC PDUs to the NR PDCP device.

Upon receiving segments, the NR RLC device may receive segments stored in a buffer or segments to be received in the future, reconfigure the segments to one complete RLC PDU, and then transmit the RLC PDU to the NR PDCP device.

The NR RLC layer may not include a concatenation function. Alternatively, the NR MAC layer may perform a concatenation function, or the concatenation function may be replaced with a multiplexing function of the NR MAC layer.

In the above description, the non-sequential delivery function (out-of-sequence delivery) of the NR RLC device may be a function of directly delivering RLC SDUs received from a lower layer to a higher layer regardless of the sequence. When one RLC SDU is divided into a plurality of RLC SDUs and received, the non-sequential delivery function (out-of-order delivery) of the NR RLC device may include a function of reassembling and then transmitting the RLC SDUs. The non-sequential delivery function (out-of-order delivery) of the NR RLC device may include a function of storing RLC SNs or PDCP SNs of the received RLC PDUs, ordering them, and recording lost RLC PDUs.

NR MACs 2-15 and 2-30 may be connected to a plurality of NR RLC layer devices configured in one UE, and main functions of the NR MACs may include some of the following functions.

Mapping function (mapping between logical channels and transport channels)

Multiplexing and demultiplexing functions (multiplexing/demultiplexing of MAC SDUs)

-scheduling information reporting function (scheduling information reporting)

HARQ function (error correction by HARQ)

Logical channel priority control function (priority handling between logical channels of UE)

UE priority control function (priority handling between UEs by dynamic scheduling)

MBMS service identity function (MBMS service identity)

Transport format selection function (transport format selection)

Filling function (filling)

The NR PHY layers 2-20 and 2-25 perform operations of channel coding and modulating higher layer data to generate OFDM symbols and transmit the OFDM symbols through a radio channel or demodulate and channel-decode OFDM symbols received through a radio channel and transmit the demodulated and channel-decoded OFDM symbols to a higher layer.

Fig. 3 illustrates a transition of a radio access state in a next generation mobile communication system according to an embodiment of the present disclosure.

The next generation mobile communication system has three radio access states (radio resource control (RRC) states). The connection mode (rrc_connected) 3-05 may be a radio access state in which the UE can transmit and receive data. The IDLE mode (rrc_idle) 3-30 may be a radio access state in which the UE monitors whether a page is sent to the UE itself. The connection mode 3-05 and the idle mode are wireless access states applied to a conventional LTE system, and the specific technology is the same as that of the conventional LTE system. New INACTIVE (rrc_inactive) radio access states 3-15 are assumed in the next generation mobile communication system. In the present disclosure, the rrc_inactive radio access states 3-15 newly defined in the next generation mobile communication system may correspond to an INACTIVE radio access state, an INACTIVE mode, a deactivated mode, and the like.

In rrc_inactive radio access states 3-15, UE context is maintained in NR gNB and UE and RAN-based paging may be supported. The characteristics of the rrc_inactive radio access state are listed below.

-cell reselection mobility;

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

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

-initiating paging by NR RAN;

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

-the NR RAN is aware of the RAN-based notification area to which the UE belongs;

according to one embodiment, the inactive radio access state may be transitioned to either the connected mode 3-05 or the idle mode 3-30 by a specific procedure. The inactive mode 3-15 may be switched to the connected mode 3-05 according to a restoration procedure, and the connected mode 3-05 may be switched to the inactive mode 3-15 by a release procedure including suspension configuration information. During procedures 3-10, one or more RRC messages may be sent and received between the UE and the NR gNB, and procedures 3-10 may include one or more steps. After resuming in operation 3-20, the inactive mode 3-15 may be switched to the idle mode 3-30 by a release procedure.

The handover between the connection mode 3-05 and the idle mode 3-30 may be performed according to conventional LTE technology. That is, the switching between the connection mode 3-05 and the idle mode 3-30 may be performed through the setup or release procedure.

In order to transmit and receive normal data, the UE in the inactive radio access state should switch to the connected mode 3-05 via the procedure 3-10. The method proposed in the present disclosure may be applied to a case where a UE transmits Small Data (SD) while maintaining an inactive state (not switching to a connected mode). For example, the small data may be a transmitted message having a relatively small size or data having a small size, such as the heart rate of a user of the wearable communication device. Or, for example, small data may be defined as data having a size that can be included in one Transport Block (TB). In the present disclosure, for convenience of description, a method of transmitting and receiving small data is described, but the scope of the present disclosure is not limited by the general meaning of the term. For example, in a state in which the UE remains in an inactive state without switching to a connected mode, according to the method described below, the embodiments presented in the present disclosure may be applied to data having a size that can be transmitted and received.

Fig. 4 is a sequence diagram illustrating a procedure in which a UE accessing a detached base station (detached gNB) is switched to an inactive radio access state in a next generation mobile communication system according to an embodiment of the present disclosure.

When the CU-CP 4-100 of the detached base station (detached gNB) determines to switch the specific UE4-400 accessing the corresponding RAN to the inactive state in operation 4-01, a suspension indication may be inserted into a bearer context modification request (BEARER CONTEXT MODIFICATION REQUEST) message and transmitted to the CU-UP 4-200 in operation 4-02. In operation 4-03, the CP-UP 4-200 may transmit a bearer context modification response in response thereto (BEARER CONTEXT MODIFICATION RESPONSE). At this time, the corresponding UE bearer context (UE BEARER CONTEXT) may be maintained between CU-CP 4-100 and CU-UP 4-200 without being removed. In operation 4-04, the CU-CP 4-100 may transmit a UE context release order (UE CONTEXT RELEASE COMMAND) message to the DU4-300 of the RAN to remove the UE context of the corresponding UE. In operation 4-05, the DU4-300 receiving the message may transmit an RRCRelease message to the UE4-400 to allow the UE4-400 to switch to the inactive mode, and may also transmit a UE context release complete (UE CONTEXT RELEASE COMPLETE) message to the CU-CP 4-100 to inform removal of the UE context in operation 4-06.

The UE may transition to the inactive mode through this procedure. The detach base station (detach gNB) may remove the UE context of the corresponding UE that exists between the DU and CU and identify that the corresponding UE transitions to the inactive mode while maintaining the bearer context of the corresponding UE that exists between CU-UP and CU-CP. The methods presented in this disclosure are applicable to UEs transitioning to inactive mode through procedures and RANs.

< first embodiment >

Fig. 5 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure and tunnel configuration of a detached base station (detached gNB) supporting the method according to the first embodiment of the present disclosure.

In operation 5-100, the ue 5-01 may simultaneously transmit an RRC message (e.g., rrcresmerequest message) and uplink data (UL data) to the gNB-DU5-02 in order to transmit small data to the user plane in the inactive mode. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling. In operation 5-200, the gNB-DU5-02 may transmit the RRCResumeRequest in the received message to the gNB-CU-CP 5-03, and in operation 5-300, transmit UL data to the gNB-CU-UP 5-04 to allow transmission of the UL data to a User Plane Function (UPF) 5-05. As shown in fig. 4, the UE context between the gNB-DU5-02 and the gNB-CUs 5-03 and 5-04 may have been removed when the particular UE 5-01 is in the inactive mode. In this case, in operation 5-200, the tunnel 5-10 through which the gNB-DU5-02 transmits data to the gNB-CU-UP 5-04 may not exist, and thus, in operation 5-300, the gNB-DU5-02 cannot simultaneously transmit the RRCResumeRequest message to the gNB-CU-CP 5-04, but transmit UL data to the gNB-CU-UP 5-04.

According to a first embodiment of the present disclosure, the gNB-DU5-02 may first transmit an rrcreseumerequest message to the gNB-CU-CP while storing (or saving) UL data in a buffer, informing of the arrival of small data from the corresponding UE, and establishing a tunnel 5-10 and a user context for data transmission between the gNB-CU-UP 5-04 and the gNB-DU 5-02. After the tunnel configuration is completed, the gNB-DU5-02 may send the stored UL data to the gNB-CUUP 5-04, and may transmit the UL data to the UPF5-05. If there is downlink data to be transmitted to the UE 5-01, the gNB-CU-UP 5-04 may transmit DL data to the gNB-DU5-02 through the generated tunnel in operation 5-400.

Fig. 6 is a sequence diagram illustrating an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to the first embodiment of the present invention.

The UE 6-100 may simultaneously transmit an RRC message (e.g., rrcreseumerequest message) and UL data to the gNB-DU6-200 in order to transmit small data in a state where the inactive mode is maintained in operation 6-01. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling.

In operation 6-02, the gNB-DU6-200 may insert the RRCResumeRequest message received from the UE 6-100 into a message (e.g., an INITIAL UL RRC messaging (INITIAL UL RRC MESSAGE TRANSFER) message) to be transmitted to the gNB-CU 6-300 and 400, and transmit the RRCResumeRequest message to the gNB-CU-CP 6-300. At this time, the initial UL RRC message transmission message may include at least one of an indicator indicating that the current operation is for Small Data Transmission (SDT) (e.g., SDT session) and an ID of a Data Radio Bearer (DRB) used by the UE to transmit UL data. Meanwhile, the gNB-DU6-200 may not directly transmit the UL data received with the RRCResumeRequest, but may store it in a buffer.

After receiving the initial UL RRC message transmission message, the gNB-CU-CP 6-300 may send a message (e.g., a UE context setup request (UE CONTEXT SETUP REQUEST) message) to the gNB-DU6-200 to generate a tunnel for UL data transmission in operation 6-03. Therefore, processing of UL data transmitted by the UE can be prepared. When the DRB ID of the SDT is obtained through the received INITIAL UL RRC message transmission (INITIAL UL MESSAGE TRANSFER), the gNB-CU-CP 6-300 may configure only the corresponding DRB, and when the DRB ID is not obtained, all the DRBs may be configured. For this, the DRB configuration information may be transmitted while inserting the DRB configuration information into a UE context setup request (UE CONTEXT SETUP REQUEST) message. The DRB configuration information may include an endpoint address (uplink endpoint) of a tunnel through which uplink data may be received by the gNB-CU-UP 6-400. Accordingly, the gNB-DU6-200 receiving the message can transmit the UL data through the generated tunnel. UL data sent from the gNB-DU6-200 may be communicated to the UPF 6-500 via the gNB-CU 6-400.

gNB-DU6-200 may transmit the UL data stored by gNB-DU6-200 through the tunnel acquired by operation 6-03 in operation 6-05.

Further, in operation 6-04, in response to the UE context setup request message, the gNB-DU6-200 may transmit a response message (e.g., a UE context setup response message) to the gNB-CU-CP6-300. The corresponding UE context setup response message may include an endpoint address (downlink endpoint) of a tunnel through which the gNB-DU6-200 may receive DL data. Thus, the gNB-CU-CP6-300 receiving the UE context setup response message may identify the endpoint address.

That is, according to embodiments of the present disclosure, an uplink endpoint for UL data transmission may be transmitted to the gNB-DU6-200 through a request message, and a downlink endpoint may be transmitted to the gNB-CU-CP6-300 through a response message.

The gNB-CU-CP6-300 may send a message (e.g., a bearer context modification request message) for informing the gNB-CU-UP 6-400 of tunnel information for transmitting the DL data obtained through operation 6-04 in operation 6-06. The message may include downlink endpoint information.

In operation 6-07, in response to the bearer context modification request message, the gNB-CU-UP 6-400 may send a response message (e.g., a bearer context modification response message) to the gNB-CU-CP6-300.

In operations 6-03 to 6-06, uplink and downlink tunnels may be generated between the gNB-DU6-200 and the gNB-CU6-400, and all the UL data and the DL data may be transmitted through the corresponding tunnels. As described above, in operation 6-03, UL data may be transmitted after the gNB-DU6-200 receives the UE context setup request and acquires (identifies) the UL endpoint address, and DL data may be transmitted after the gNB-CU6-400 acquires (identifies) the DL endpoint address from the gNB-CU6-300 through the bearer context modification request message.

After receiving the UL data from the gNB-CU-UP 6-400, the UPF 6-500 may transmit DL data to the gNB-CU-UP 6-400 when there is a DL data header of the UE 6-100 that has transmitted the corresponding data in operation 6-08. Alternatively, after receiving the UL data from the gNB-CU-UP 6-400, the UPF 6-500 may transmit the DL data to the gNB-CU-UP 6-400 after a predetermined time when there is a DL data header of the UE 6-100 that has transmitted the corresponding data. This is because DL data can be transmitted to the gNB-DU6-200 only when the gNB-CU-UP 6-400 obtains the DL endpoint address. How long after the UPF 6-500 receives the UL data to transmit the DL data may be determined using a timer, which may follow an implementation method. If there is no DL data to be transmitted to the UE 6-100, operation 6-08 may be omitted.

According to an embodiment, when there is no DL data header or no additional DL data for the UE 6-100 after operation 6-08, the gNB-CU-CP 6-300 may send a message (e.g., a UE context release command message) to the gNB-DU6-200 to remove the UE context in operation 6-09.

In operation 6-10, the gNB-DU6-200 receiving the UE context release command message may send an RRC message (e.g., RRCRelease message) included in the message to the UE 6-100. At this time, the gNB-DU6-200 may also transmit the DL data received in operation 6-08 to the UE 6-100 together with the RRCRelease message. For example, DL data may be transmitted upon inserting an RRCRelease message, or may be transmitted through separate signaling.

In operation 6-11, the gNB-DU6-200 may send a message (e.g., a UE context release complete message) informing the gNB-CU-CP 6-300 of the removal of the UE context, and the gNB-CU-CP 6-300 may identify the removal of the UE context based on the message.

Fig. 7 shows a message and an Information Element (IE) according to a first embodiment of the present disclosure.

The message (e.g., initial UL RRC message transfer message) 7-100 that transmits the RRC message received by the gNB-DU from the UE to the gNB-CU-CP may include at least one of information or IE (e.g., SDT session) 7-110 indicating the RRC message SDT transmitted by the UE and information or IE (e.g., SDT session). The DRB ID 7-120 of the SDT indicates the DRB ID that transmits UL data. According to an embodiment, when an SDT session in an initial UL RRC message transmission received by the gNB-CU-CP is configured to be true, the message may be identified as an RRC message for the SDT and a UE context associated with the DRB corresponding to the DRB ID of the SDT may be established. Meanwhile, all the information must be included in one message, but only some of the information may be included, and other information may be further included. The corresponding pieces of information may be sent by separate messages.

< second embodiment >

Fig. 8 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure of a detach base station (detach gNB) supporting the method according to the second embodiment of the present disclosure.

In operation 8-100, the ue 8-01 may send an RRC message (e.g., rrcresmerequest message) and UL data to the gNB-DU8-02 simultaneously in order to send small data to the user plane in the inactive mode. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling. In operation 8-200, the gNB-DU8-02 may transmit all received messages (RRCResumeRequest+UL data) to the gNB-CU-CP 8-03, and in operation 8-300, the gNB-CU-CP 8-03 may transmit UL data to the gNB-CU-UP 8-04 and eventually send it to the UPF 8-05. Even when there is downlink data (DL data) to be transmitted to the UE 8-01, the gNB-CU-UP 8-04 may transmit DL data to the gNB-CU-CP 8-03 so as to be transmitted to the gNB-DU8-02 in operation 8-400. Thus, in the method shown in fig. 8, unlike the method shown in fig. 5, a configuration of a separate tunnel for transmitting UL data or DL data between the gNB-CU-UP 8-04 and the gNB-DU8-02 may not be required.

Fig. 9A and 9B are sequence diagrams illustrating operations between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to the second embodiment of the present disclosure.

The UE 9-100 may simultaneously transmit an RRC message (e.g., rrcreseumerequest message) and UL data to the gNB-DU9-200 in order to transmit small data in a state where the inactive mode is maintained in operation 9-01. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling.

In operation 9-02, the gNB-DU9-200 may insert the RRCResumeRequest message into an RRC container within a message (e.g., an initial UL RRC message transfer message) conveying the RRC message received from the UE 9-100 to the gNB-CU9-300, and insert UL data into the UL SD container to send it to the gNB-CU9-300. At this time, the initial UL RRC message transmission message may include at least one of an indicator indicating that the current operation is for Small Data Transmission (SDT) (e.g., SDT session) and an ID of a Data Radio Bearer (DRB) used by the UE to transmit UL data.

After receiving the initial UL RRC message transmission message, the gNB-CU-CP 9-300 may send UL data in the UL SD container within the corresponding message to the gNB-CU-UP 9-400 for transmission to the UPF. Thus, two methods are presented in the second embodiment of the present disclosure.

Method 1-1

First, the gNB-CU-CP 9-300 may newly define a message for transmitting UL data to the gNB-CU-UP 9-400. In this disclosure, the newly defined message is referred to as, for example, a UL small data transfer (UL SMALL DATA TRANSFER) message.

In operation 9-03a, the gNB-CU-UP 9-300 may insert the UL data received in operation 9-02 into a UL SD container within the UL small data transfer message and transmit it to the gNB-CU-UP 9-400. According to one embodiment, the DRB ID received in operation 9-02 may also be inserted into the UL small data transfer message at this time and then transmitted. This is because the gNB-CU-UP 9-400 should be aware of the PDCP through which data is processed. The gNB-CU-UP 9-400 can acquire DRB information for transmitting UL data to process the data through PDCP matched with the corresponding DRB and transmit the data to the UPF 9-500.

Methods 1-2

Second, information or Information Elements (IEs) for transmitting UL data included in existing messages (e.g., bearer context modification request messages) transmitted from the gNB-CU-CP 9-300 to the gNB-CU-UP 9-400 may be newly defined. In this disclosure, the newly defined IE is referred to as, for example, a UL SD container IE.

In operation 9-03b, the gNB-CU-CP 9-300 may insert the UL data received in operation 9-02 into the UL SD container in the bearer context modification request message and send it to the gNB-CU-UP 9-400. According to one embodiment, as described in method 1-1, since the gNB-CU-UP 9-400 should be aware of the PDCP through which data is processed, the DRB ID should also be inserted into the bearer context modification request message.

In operation 9-04, the gNB-CU-UP 9-400 may send the received UL data to the UPF 9-500.

After receiving the UL data from the gNB-CU-UP 9-400, the UPF 9-500 may transmit DL data to the gNB-CU-UP 9-400 when there is data to be transmitted to the corresponding UE 9-100 in operation 9-05. If there is no DL data to be transmitted to the UE 9-100, the operations described below may be omitted.

When the DL data is received, the gNB-CU-UP 9-400 may transmit the DL data to the gNB-CU-CP 9-300, so as to allow the gNB-CU-CP 9-300 to transmit the DL data to the gNB-DU 9-200. Thus, two methods are presented in the second embodiment of the present disclosure.

Method 2-1

First, the gNB-CU-UP 9-400 may newly define a message for transmitting DL data to the gNB-CU-CP 9-300. In this disclosure, the newly defined message is referred to as, for example, a small data transfer notification (SMALL DATA TRANSMISSION NOTIFY) message.

When there is DL data received from the UPF 9-500 in operation 9-05, the gNB-CU-UP 9-400 may insert the DL data into a DL SD container within the small data transmission notification message and transmit it to the gNB-CU-CP 9-300 in operation 9-06 a. According to one embodiment, a DRB ID may also be inserted and transmitted to allow the gNB-DU 9-200 receiving the DL data to determine the RLC matching the DL data. Meanwhile, no DL data is to be transmitted to the UE 9-100, and a corresponding message may not be transmitted. A timer may be used to determine the point in time at which the corresponding message is sent, which may follow the implementation method.

Method 2-2

Second, information or an IE of transmission DL data included in an existing message (e.g., a bearer context modification response message) transmitted from the gNB-CU-UP 9-400 to the gNB-CU-CP 9-300 may be newly defined. In this disclosure, the newly defined IE is referred to as, for example, a DL SD container.

When there is DL data received from the UPF 9-500 in operation 9-05, the gNB-CU-UP 9-400 may insert the DL data into a DL SD container within the bearer context modification response message and send it to the gNB-CU-CP 9-300 in operation 9-06 b. According to one embodiment, as described in method 2-1), a DRB ID may also be inserted into the bearer context modification response message and sent to allow the gNB-DU9-200 receiving DL data to determine the RLC matching the DL data. A timer may be used to determine the point in time at which the corresponding message is sent, which may follow the implementation method. Meanwhile, unlike the method 2-1), even when there is no DL data, a response message may be transmitted as a response to the bearer context modification request message.

The gNB-CU-CP 9-300 receiving the small data transmission notification message or the bearer context modification response message in operation 9-06a or 9-06b may insert the RRCRelease message into an RRC container within the message (e.g., DL RRC messaging message) for transmitting the RRC message to be transmitted to the UE 9-100 to the gNB-DU9-200 and transmitting the message to the gNB-DU9-200 in operation 9-07. At this time, when DL data is received in operation 9-06a or 9-06b, the gNB-CU-CP 9-300 may insert the corresponding data into a DL SD container within the DL RRC messaging message and also insert a DRB ID corresponding to the DL data and transmit the message to the gNB-DU9-200.

In operation 9-08, the gNB-DU 9-200 receiving the DL RRC message transfer message may send an RRCRelease message to the UE 9-100 within the DL RRC message transfer. When DL data is received, an RRCRelease message may be transmitted to the UE together with the DL data in operation 9-07. At this time, DL data may be transmitted through DRBs corresponding to the DRB IDs received together. For example, DL data may be inserted into the RRCRelease message and transmitted, or may be transmitted through separate signaling.

Fig. 10A to 10D illustrate messages and Information Elements (IEs) according to a second embodiment of the present disclosure.

The message (e.g., initial UL RRC message transmission) 10-100 conveying the RRC message received by the gNB-DU from the UE may include at least one of information or IEs (e.g., SDT sessions) 10-110 indicating that the RRC message sent by the UE is for Small Data Transfer (SDT). The DRB ID 10-120 of the SDT indicates the DRB ID to transmit UL data. In addition, UL data may also be included in the message 10-100 through UL SD container 10-130IE and sent to the gNB-CU-CP.

In order to transmit UL data received from the gNB-DU to the gNB-CU-UP, a newly defined message (e.g., UL small data transmission message) 10-200 may be transmitted to the gNB-CU-UP according to the above-described method 1-1. Alternatively, according to the above method 1-2, the newly defined information or IE may be added to an existing message (e.g., bearer context modification request message) 10-400 transmitted from the gNB-CU-CP to the gNB-CU-UP for transmitting the UL data.

According to method 1-1), the UL small data transfer message 10-200 transmitted to the gNB-CU-UP by the gNB-CU-CP may include at least one of a message type 10-210, a gNB-CU-CP E1AP ID 10-220, and a gNB-CU-UP E1AP ID 10-230 of the UE transmitting UL data. The same DRB ID information (e.g., DRB ID of SDT) 10-240 and UL SD container 10-250IE as at least one of DRB ID information (e.g., DRB ID of SDT) 10-240 and UL SD container 10-250IE received from the gNB-DU may also be included.

Alternatively, according to method 1-2), the bearer context modification request message 10-400 sent by the gNB-CU-CP to the gNB-CU-UP may further include at least one of DRB ID information (e.g., DRB ID of SDT) 10-410 and UL SD container 10-420IE, which are identical to those received from the gNB-DU.

After transmitting UL data to the UPF (or after receiving DL data (if DL data exists) from the UPF), the gNB-CU-UP may transmit a newly defined message (e.g., a small data transmission notification message according to method 2-1) 10-300 to notify the gNB-CU-CP of the transmission or reception. Alternatively, according to the above method 2-2, the newly defined information or IE may be added to an existing message, for example, a bearer context modification request message 10-500 sent from the gNB-CU-UP to the gNB-CU-CP, and sent to transmit the DL data.

According to method 2-1, the small data transmission notification message 10-300 sent by the gNB-CU-UP to the gNB-CU-CP may include at least one of a message type 10-310 of the UE, gNB-CU-CP E1AP ID 10-320, and gNB-CU-UP E1AP ID 10-330 to receive the DL data, and may further include at least one of a DL SD container 10-350 containing the DL data received from the UPF and information indicating the DRB ID (e.g., DRB ID of SDT) 10-340.

Alternatively, according to method 2-2, the bearer context modification response message 10-500 sent by the gNB-CU-UP to the gNB-CU-UP may further include at least one of the DL SD container 10-520 including DL data and information indicating a DRB ID (e.g., a DRB ID of the SDT) 10-510.

When there is DL data to be transmitted to the UE, the DL RRC message transmission message 10-600 may further include at least one of a DRB ID of the SDT 10-610 and a DL SD container 10-620IE to transmit DL data to the gNB-DU through the gNB-CU-CP.

< third embodiment >

Fig. 11 illustrates a method of transmitting Small Data (SD) transmitted by an inactive mode UE to a user plane, and a structure of a detach base station (detach gNB) supporting the method according to the third embodiment of the present disclosure. This method may be applied when the UPF has DL data to send to the UE.

In operation 11-100, the ue 11-01 may simultaneously transmit an RRC message (e.g., rrcresmerequest message) and UL data to the gNB-DU11-02 in order to transmit small data to the user plane in the inactive mode. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling. In the case of UL data, as described in the second embodiment, in operation 11-200, the gNB-DU11-02 may transmit all received messages (rrcrumerequest+ul data) to the gNB-CU-CP 11-03, and in operation 11-300, the gNB-CU-CP 11-03 may transmit UL data to the gNB-CU-UP 11-04 and finally to the UPF 11-05. As described in the first embodiment, when there is downlink data (DL data) to be transmitted to the UE 11-01, a tunnel and a user context for DL data transmission may be established between the gNB-CU-UP 11-04 and the gNB-DU. Through configuration of the tunnel, the gNB-CU-UP 11-04 may transmit the DL data to the gNB-DU11-02 and transmit it to the UE 11-01 in operation 11-400.

Fig. 12 is a sequence diagram showing an operation between a UE and a detached base station (detached gNB) or inside the detached base station (detached gNB) according to the third embodiment of the present disclosure.

The UE 12-100 may simultaneously transmit an RRC message (e.g., rrcreseumerequest message) and UL data to the gNB-DU 12-200 in order to transmit small data in a state where the inactive mode is maintained in operation 12-01. For example, UL data may be transmitted when UL data is inserted into the RRCResumeRequest message, or UL data may be transmitted through separate signaling.

In operation 12-02, the gNB-DU 12-200 may insert the RRCResumeRequest message into an RRC container within a message (e.g., an initial UL RRC message transfer message) used to transfer RRC messages received from the UE 12-100 to the gNB-CU 12-300 and 12-400, and insert UL data into an UL SD container to send it to the gNB-CU-CP 12-300. At this time, the initial UL RRC message transfer message may include at least one of an indicator indicating that the current operation is for Small Data Transmission (SDT) (e.g., SDT session) and an ID of a Data Radio Bearer (DRB) used by the UE to transmit UL data.

After receiving the initial UL RRC message transmission message, the gNB-CU-CP 12-300 may send UL data in the UL SD container within the corresponding message to the gNB-CU-UP 12-400 for transmission to the UPF. Thus, similar to method 1-1 of the second embodiment, a message (e.g., a UL small data transfer message) in which the gNB-CU-CP 12-300 transfers UL data to the gNB-CU-UP 12-400 may be newly defined. Alternatively, similar to method 1-2, information or Information Elements (IEs) for transmitting UL data included in existing messages (e.g., bearer context modification request messages) transmitted from gNB-CU-CP 12-300 to gNB-CU-UP 12-400 may be newly defined.

In operation 12-03, the gNB-CU-CP 12-300 may insert the UL data received in operation 12-02 into a UL SD container within a UL small data transfer message or bearer context modification request message and send it to the gNB-CU-UP 12-400. According to one embodiment, the DRB ID received in operation 12-02 may also be inserted into the message and transmitted at this time. This is because the gNB-CU-UP 12-400 should be aware of the PDCP through which data is processed. The gNB-CU-UP 12-400 can acquire DRB information for transmitting UL data to process the data through PDCP matched with the corresponding DRB and transmit the data to the UPF 12-500.

In operation 12-04, the gNB-CU-UP 12-400 may send the received UL data to the UPF 12-500.

In operation 12-05, after receiving the initial UL RRC message transmission message, the gNB-CU-UP 12-300 may transmit a UE context setup request message to the gNB-DU 12-200.

Further, in operation 12-06, in response to the UE context setup request message, the gNB-DU 12-200 may transmit a response message (e.g., a UE context setup response message) to the gNB-CU-CP 12-300. The corresponding UE context setup response message may include an endpoint address (downlink endpoint) of the tunnel for receiving DL data by the gNB-DU 12-200. Thus, the gNB-CU-CP 12-300 receiving the UE context setup response message may identify the endpoint address.

The gNB-CU-CP 12-300 may send a message (e.g., a bearer context modification request message) for informing the gNB-CU-UP 12-400 of tunnel information for transmitting the DL data obtained through operation 12-04 in operation 12-007. The message may include downlink endpoint information.

In operation 12-08, in response to the bearer context modification request message, the gNB-CU-UP 12-400 may send a response message (e.g., a bearer context modification response message) to the gNB-CU-CP 12-300.

In operations 12-05 to 12-08, a downlink tunnel may be generated between the gNB-DU12-200 and the gNB-CU12-400, and the DL data may be transmitted through the corresponding tunnel. As described above, UL data may be transmitted to gNB-CU-UP through gNB-CP-CP 12-300 and ultimately to UPF

12-500 and may transmit DL data after the DL endpoint address is obtained (identified) from the gNB-CU-CP 12-300 by the gNB-CU-UP 12-400 by the bearer context modification request message.

After receiving the UL data from the gNB-CU-UP 12-400, the UPF 12-500 may transmit DL data to the gNB-CU-UP 12-400 when there is a DL data header of the UE 12-100 that has transmitted the corresponding data in operation 12-09. Alternatively, after receiving the UL data from the gNB-CU-UP 12-400, the UPF 12-500 may send the DL data to the gNB-CU-UP 12-400 after a predetermined time when there is a DL data header of the UE 12-100 that has sent the corresponding data. This is because DL data can be transmitted to the gNB-DU12-200 only when the gNB-CU-UP 12-400 obtains the DL endpoint address. How long after the UPF 12-500 receives the UL data to transmit the DL data may be determined using a timer, which may follow an implementation method.

According to an embodiment, when there is no additional DL data after operation 12-09, the gNB-CU-CP 12-300 may send a message (e.g., a UE context release command message) to the gNB-DU12-200 in operation 12-10 to remove the UE context.

In operation 12-11, the gNB-DU12-200 receiving the UE context release command message may send an RRC message (e.g., an RRCRelease message) included in the message to the UE 12-100. At this time, the gNB-DU12-200 may also transmit the DL data received in operation 12-08 to the UE 12-100 along with the RRCRelease message. For example, DL data may be inserted into the RRCRelease message and transmitted, or may be transmitted through separate signaling.

The gNB-DU12-200 may transmit a message (e.g., a UE context release complete message) informing the gNB-CU-CP 12-300 of the removal of the UE context in operation 12-12, and the gNB-CU-CP 12-300 may identify the removal of the UE context based on the message.

Fig. 13 illustrates a structure of a UE according to an embodiment of the present disclosure.

Referring to fig. 13, the ue may include a wireless transceiver 13-10, a controller 13-20, and a storage unit 13-30. In this disclosure, a controller may be defined as a circuit, an application specific integrated circuit, or at least one processor.

The radio transceiver 13-10 may send and receive signals to and from another network entity. The radio transceiver 13-10 may receive, for example, a signal from the BS and transmit a signal including an RRC resume request message or small UL data (SDT UL data) to the BS.

According to embodiments presented in the present disclosure, the controllers 13-20 may control the overall operation of the UE. For example, the controllers 13-20 may control the signal flow between the various blocks to perform operations according to the flowcharts described above. Specifically, according to embodiments of the present disclosure, the controllers 13-20 may control operations set forth in the present disclosure, such as sending an RRC resume request message to the gNB-DU, and determining the radio access state based on the received RRC release message.

The storage unit 13-30 may store at least one piece of information transmitted and received through the transceiver 13-10 and information generated through the controller 13-20. For example, the storage units 13 to 30 may store the radio access state information and DL data.

Fig. 14 illustrates a structure of a BS according to an embodiment of the present disclosure.

Referring to fig. 14, a BS may include a radio transceiver 14-10, another BS/core network transceiver 14-20, a controller 14-30, and a storage unit 14-40. In this disclosure, a controller may be defined as a circuit, an application specific integrated circuit, or at least one processor.

The BS shown in fig. 14 may be a RAN node that includes both the gNB-CU and the gNB-DU. The RAN node may be a mobile communication BS such as an LTE evolved node B (eNodeB) or a next generation node B (NRgNB or gndeb) connected to a mobile communication Core Network (CN) such as an Evolved Packet Core (EPC) or a 5G core network (5 GC). Further, the RAN node may be divided into a Centralized Unit (CU) and a Distributed Unit (DU), and the CU may be divided into a CU Control Plane (CP) and a CU User Plane (UP).

According to an embodiment, the RAN node may comprise one or more CU-CPs, one or more CU-UP and one or more DUs. Further, CU-CP, CU-UP and DU included in the RAN node may be configured together. For example, the RAN node may include a CU and a DU, where the CU-CP and CU-UP are configured together in the CU. In another example, the CU-CP and DU may be configured together in the RAN node and the CU-UP may be configured separately therein. In another example, the RAN node may be configured in the form of an aggregated base station (aggregated gNB), where CU-CP, CU-UP, and DU are configured together. The RAN node may be configured by another combination and example as described above.

According to one embodiment, the CUs and DUs may support BS functions separately. For example, a CU may support the RRC/PDCP layer, while a DU may support the RLC/MAC/PHY/RF layer. Furthermore, the CU and DU may be connected by an interface between functions within the BS, such as a W1 or F1 interface.

According to one embodiment, CUs may be divided into CU-CP and CU-UP. For example, a CU-CP may support an RRC/PDCP (for RRC) layer, a CU-UP may support a PDCP (for user data transfer) layer, and the CU-CP and the CU-UP may interface between functions within the BS, such as an E1 interface.

According to one embodiment, BSs may be configured in an aggregated structure or a split structure, and connections between aggregated base stations (aggregated GNBS), split base stations (split GNBS), and between aggregated base stations (aggregated gNB) and split base stations (split gNB) are possible. The RAN nodes may be connected via an inter-BS interface such as an X2 or Xn interface. Furthermore, the RAN node and the core network may be connected through an interface between the BS and the core network, such as an S1 or NG interface.

The radio transceiver 14-10 may transmit signals to and receive signals from another network entity. The radio transceiver 14-10 may transmit and receive signals to and from the UE or transmit signals including messages (e.g., RRC releases) that control the operation of the UE.

The other BS/core network transceiver 14-20 may transmit signals to and receive signals from another network entity. For example, SDT UL/DL data exchanged with UPF may be transmitted and received.

According to the embodiments presented in the present disclosure, the controllers 14-30 may control the overall operation of the BS. For example, the controllers 14-30 may control the signal flow between the various blocks to perform operations according to the flowcharts described above.

The storage unit 14-40 may store at least one piece of information transmitted and received through the radio transceiver 14-10 and the other BS/core network transceiver 14-20 and information generated through the controller 14-30. For example, the storage units 14-40 may store the UL data header of the UPF.

In the above detailed embodiments of the present disclosure, elements included in the present disclosure are expressed in singular or plural according to the presented detailed embodiments. However, for convenience of description, the singular or plural forms are appropriately selected as presented, and the present disclosure is not limited by the elements expressed in the singular or plural. Thus, an element expressed in a plurality of numbers can also include a single element, or an element expressed in the singular can also include a plurality of elements.

The embodiments of the present disclosure described and illustrated in the specification and drawings are merely specific examples, which have been presented to easily explain the technical content of the present disclosure and to aid understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, those skilled in the art will understand that other modifications based on the technical ideas of the present disclosure may be implemented. Further, the respective embodiments described above may be used in combination as needed. For example, a portion of an embodiment of the present disclosure may be combined with a portion of another embodiment of the present disclosure. Further, other modifications based on the technical ideas of the above-described embodiments may also be implemented in other systems such as LTE, 5G, or NR systems.

Claims (15)

1. A method of a base station, BS, in a wireless communication system, the method comprising:

receiving, by a distributed unit DU of a base station BS, a radio resource control RRC message including uplink data from a user equipment UE in an inactive mode;

transmitting, by the DU to a centralized unit control plane, CU-CP, of the BS, a first message including at least one indicator information related to transmission of the uplink data and identification information of a data radio bearer, DRB, corresponding to the uplink data; and

and sending the uplink data to a user plane function UPF based on the first message.

2. The method of claim 1, wherein transmitting the uplink data to the UPF comprises:

transmitting, by the CU-CP, a second message to the DU based on the first message, the second message including address information related to uplink transmission of a centralized unit user plane, CU-UP, of the BS;

transmitting, by the DU, the uplink data to the CU-UP based on address information related to uplink transmission of the CU-UP; and

the uplink data is sent by the CU-UP to the UPF.

3. The method of claim 2, further comprising:

transmitting, by the DU to the CU-CP in response to the second message, a third message including address information related to downlink transmission of the DU;

transmitting, by the CU-CP to the CU-UP, a fourth message including address information related to downlink transmission of the DU based on the third message;

receiving, by the CU-CP, downlink data of the UE from the UPF;

transmitting, by the CU-UP, the downlink data to the DU based on address information related to downlink transmission of the DU; and

and transmitting an RRC message including the downlink data to the UE by the DU.

4. The method of claim 1, wherein the first message further comprises the uplink data, and

wherein transmitting the uplink data to the UPF comprises:

transmitting, by the CU-CP, a fifth message to the CU-UP, the fifth message including the uplink data and identification information of the DRB; and

and transmitting the uplink data to the UPF by the CU-UP based on the fifth message.

5. The method of claim 4, further comprising:

Receiving, by the CU-UP, downlink data of the UE from the UPF;

transmitting, by the CU-UP to the CU-CP, a sixth message including the downlink data and identification information of the DRB;

transmitting, by the CU-CP, a seventh message to the DU based on the sixth message, the seventh message including the downlink data and identification information of the DRB; and

and transmitting an RRC message including the downlink data to the UE by the DU based on the identification information of the DRB.

6. The method of claim 4, further comprising:

transmitting, by the DU to the CU-CP, an eighth message including address information related to downlink transmission of the DU;

transmitting, by the CU-CP to the CU-UP, a ninth message including address information related to downlink transmission of the DU based on the eighth message;

receiving, by the CU-UP, downlink data of the UE from the UPF;

transmitting, by the CU-UP, downlink data to the DU based on address information related to downlink transmission of the DU; and

and transmitting an RRC message including the downlink data to the UE by the DU.

7. The method of claim 1, wherein the uplink data has a size allowed to be included in one transport block TB.

8. A base station, BS, in a wireless communication system, the BS comprising:

a transceiver; and

a controller configured to control the transceiver to:

receiving, by a distributed unit DU of the BS, a radio resource control RRC message including uplink data from a user equipment UE in an inactive mode;

transmitting, by the DU to a centralized unit control plane, CU-CP, of the BS, a first message including at least one indicator information related to transmission of the uplink data and identification information of a data radio bearer, DRB, corresponding to the uplink data; and

and sending the uplink data to a user plane function UPF based on the first message.

9. The BS of claim 8, wherein the controller is configured to control the transceiver to:

transmitting, by the CU-CP, a second message to the DU based on the first message, the second message including address information related to uplink transmission of a centralized unit user plane, CU-UP, of the BS;

Transmitting, by the DU, the uplink data to the CU-UP based on address information related to uplink transmission of the CU-UP; and

the uplink data is sent by the CU-UP to the UPF.

10. The BS of claim 9, wherein the controller is configured to control the transceiver to:

transmitting, by the DU to the CU-CP in response to the second message, a third message including address information related to downlink transmission of the DU;

transmitting, by the CU-CP to the CU-UP, a fourth message including address information related to downlink transmission of the DU based on the third message;

receiving, by the CU-UP, downlink data of the UE from the UPF;

transmitting, by the CU-UP, the downlink data to the DU based on address information related to downlink transmission of the DU; and

and transmitting an RRC message including the downlink data to the UE by the DU.

11. The BS of claim 8, wherein the first message further comprises the uplink data, and

wherein the controller is configured to control the transceiver to:

Transmitting, by the CU-CP to the CU-UP, a fifth message based on the first message, the fifth message including the uplink data and identification information of the DRB; and

and transmitting the uplink data to the UPF by the CU-UP based on the fifth message.

12. The BS of claim 11, wherein the controller is configured to transceiver to:

receiving, by the CU-UP, downlink data of the UE from the UPF;

transmitting, by the CU-UP to the CU-CP, a sixth message including the downlink data and identification information of the DRB;

transmitting, by the CU-CP, a seventh message to the DU based on the sixth message, the seventh message including the downlink data and identification information of the DRB; and

and transmitting an RRC message including the downlink data to the UE by the DU based on the identification information of the DRB.

13. The BS of claim 11, wherein the controller is configured to control the transceiver to:

transmitting, by the DU to the CU-CP, an eighth message including address information related to downlink transmission of the DU; and

And transmitting, by the CU-CP to the CU-UP, a ninth message including address information related to downlink transmission of the DU based on the eighth message.

14. The BS of claim 13, wherein the controller is configured to control the transceiver to:

receiving, by the CU-UP, downlink data of the UE from the UPF;

transmitting, by the CU-UP, the downlink data to the DU based on address information related to downlink transmission of the DU; and

and transmitting an RRC message including the downlink data to the UE by the DU.

15. The BS of claim 8, wherein the uplink data has a size allowed to be contained in one transport block TB.