WO2018199673A1 - Method for transmitting data according to edt - Google Patents

Abstract

One disclosure of the present specification provides a method for supporting early data transmission (EDT) by a base station. The method may comprise a step of receiving a first message from a mobility management entity (MME). A first NAS message may include downlink data. The method may further comprise a step of confirming that there is no additional data other than the downlink data, on the basis of reception of the first NAS message.

Description

Method of transmitting data according to EDT

The present invention relates to mobile communications.

The 3GPP, which enacts the technical specifications of the mobile communication system, has been trying to optimize and improve the performance of 3GPP technologies since late 2004 in order to respond to various forums and new technologies related to 4G mobile communication. Started research on Term Evolution / System Architecture Evolution technology.

SAE, centered on 3GPP SA WG2, is a study on network technology aimed at determining network structure and supporting mobility between heterogeneous networks in parallel with LTE work of 3GPP TSG RAN. Recent important standardization issues of 3GPP Is one of. This is a work to develop a 3GPP system into a system supporting various radio access technologies based on IP, and has been aimed at an optimized packet-based system that minimizes transmission delay with improved data transmission capability.

The Evolved Packet System (EPS) high-level reference model, defined by 3GPP SA WG2, includes non-roaming cases and roaming cases in various scenarios. Reference may be made to documents TS 23.401 and TS 23.402. The network structure diagram of FIG. 1 is a simple reconfiguration.

1 is a structural diagram of an evolved mobile communication network.

The EPC may include various components, and in FIG. 1, some of them correspond to a Serving Gateway (S-GW) 52, a PDN Packet Data Network Gateway (GW) 53, and a Mobility Management Entity (MME). 51, a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN), and an enhanced Packet Data Gateway (ePDG).

The S-GW 52 operates as a boundary point between the radio access network (RAN) and the core network, and is an element that functions to maintain a data path between the eNodeB 20 and the PDN GW 53. In addition, when a terminal (or user equipment: UE) moves over an area served by the eNodeB 20, the S-GW 52 serves as a local mobility anchor point. That is, packets may be routed through the S-GW 52 for mobility in the E-UTRAN (Universal Mobile Telecommunications System (Evolved-UMTS) Terrestrial Radio Access Network defined in 3GPP Release-8 or later). In addition, the S-GW 52 may be connected to other 3GPP networks (RANs defined before 3GPP Release-8, for example, UTRAN or GERAN (GSM (Global System for Mobile Communication) / EDGE (Enhanced Data rates for Global Evolution) Radio Access). It can also serve as an anchor point for mobility with a network).

PDN GW (or P-GW) 53 corresponds to the termination point of the data interface towards the packet data network. The PDN GW 53 may support policy enforcement features, packet filtering, charging support, and the like. In addition, mobility management between 3GPP networks and non-3GPP networks (for example, untrusted networks such as Interworking Wireless Local Area Networks (I-WLANs), code-division multiple access (CDMA) networks, or trusted networks such as WiMax) Can serve as an anchor point for.

Although the S-GW 52 and the PDN GW 53 are configured as separate gateways in the example of the network structure of FIG. 1, two gateways may be implemented according to a single gateway configuration option. have.

The MME 51 is an element that performs signaling and control functions to support access to the network connection of the UE, allocation of network resources, tracking, paging, roaming and handover, and the like. . The MME 51 controls control plane functions related to subscriber and session management. The MME 51 manages a number of eNodeBs 20 and performs signaling for the selection of a conventional gateway for handover to other 2G / 3G networks. In addition, the MME 51 performs security procedures, terminal-to-network session handling, idle terminal location management, and the like.

The SGSN handles all packet data, such as user's mobility management and authentication to other connecting 3GPP networks (e.g., GPRS networks, UTRAN / GERAN).

The ePDG acts as a secure node for untrusted non-3GPP networks (eg, I-WLAN, WiFi hotspots, etc.).

As described with reference to FIG. 1, a terminal (or UE) having IP capability is provided by an operator (ie, an operator) via various elements in the EPC, based on 3GPP access as well as non-3GPP access. Access to an IP service network (eg, IMS).

1 illustrates various reference points (eg, S1-U, S1-MME, etc.). In the 3GPP system, a conceptual link defining two functions existing in different functional entities of E-UTRAN and EPC is defined as a reference point. Table 1 below summarizes the reference points shown in FIG. 1. In addition to the examples of Table 1, there may be various reference points according to the network structure.

Reference point	Explanation
S1-MME	Reference point for control plane protocol between E-UTRAN and MME
S1-U	Reference point between E-UTRAN and SGW for inter-eNB eNB switching and per-bearer user plane tunneling during handover
S3	Reference point between MME and SGSN that provides user and bearer information exchange for mobility between 3GPP access networks in idle and / or active state. This reference point can be used in PLMN-to-PLMN-to-for example (for PLMN-to-PLMN handover))
S4	Reference point between SGW and SGSN that provides relevant control and mobility support between the GPRS core and SGW's 3GPP anchor functionality. It also provides user plane tunneling if no direct tunnel is established.
S5	Reference point providing user plane tunneling and tunnel management between the SGW and PDN GW. Used for SGW relocation because of UE mobility and when a connection to the PDN GW where the SGW is not co-located is required for the required PDN connectivity.
S11	Reference point between MME and SGW
SGi	Reference point between the PDN GW and the PDN. The PDN may be an operator external public or private PDN or, for example, an in-operator PDN for the provision of IMS services. This reference point corresponds to Gi of 3GPP access

Among the reference points shown in FIG. 1, S2a and S2b correspond to non-3GPP interfaces. S2a is a reference point that provides the user plane with associated control and mobility support between trusted non-3GPP access and PDN GW. S2b is a reference point that provides the user plane with relevant control and mobility support between the ePDG and PDN GW.

Figure 2 is an exemplary view showing the functions of the main nodes of the E-UTRAN and the general EPC in general.

As shown, the eNodeB 20 may route to a gateway, schedule and transmit paging signals, schedule and transmit broadcaster channels (BCHs), uplink and downlink while an RRC (Radio Resource Control) connection is active. Dynamic allocation of resources in the UE, configuration and provision for the measurement of the eNodeB (20), radio bearer control, radio admission control (radio admission control), and can perform functions for connection mobility control. Within the EPC, paging can occur, LTE_IDLE state management, user planes can perform encryption, EPS bearer control, NAS signaling encryption and integrity protection.

3 is an exemplary diagram illustrating a structure of a radio interface protocol in a control plane between a UE and an eNodeB, and FIG. 4 is a structure of a radio interface protocol in a user plane between a terminal and a base station. Another example is shown.

The radio interface protocol is based on the 3GPP radio access network standard. The air interface protocol consists of a physical layer (Physical layer), a data link layer (Data Link layer) and a network layer (Network layer) horizontally, vertically the user plane (User Plane) and control for data information transmission It is divided into a control plane for signal transmission.

The protocol layers are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems, and includes L1 (first layer), L2 (second layer), and L3 (third layer). ) Can be separated.

Hereinafter, each layer of the radio protocol of the control plane shown in FIG. 3 and the radio protocol in the user plane shown in FIG. 4 will be described.

The physical layer, which is the first layer, provides an information transfer service using a physical channel. The physical layer is connected to a medium access control layer on the upper side through a transport channel, and data between the medium access control layer and the physical layer is transmitted through the transport channel. In addition, data is transferred between different physical layers, that is, between physical layers of a transmitting side and a receiving side through a physical channel.

The physical channel is composed of several subframes on the time axis and several sub-carriers on the frequency axis. Here, one subframe includes a plurality of symbols and a plurality of subcarriers on the time axis. One subframe consists of a plurality of resource blocks, and one resource block consists of a plurality of symbols and a plurality of subcarriers. The transmission time interval (TTI), which is a unit time for transmitting data, is 1 ms corresponding to one subframe.

According to 3GPP LTE, the physical channels existing in the physical layer of the transmitting side and the receiving side are physical downlink shared channel (PDSCH), physical uplink shared channel (PUSCH) and physical downlink control channel (PDCCH), which are control channels, It may be divided into a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH).

The PCFICH transmitted in the first OFDM symbol of a subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. The wireless device first receives the CFI on the PCFICH and then monitors the PDCCH.

Unlike the PDCCH, the PCFICH does not use blind decoding and is transmitted on a fixed PCFICH resource of a subframe.

The PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for a UL hybrid automatic repeat request (HARQ). The ACK / NACK signal for uplink (UL) data on the PUSCH transmitted by the wireless device is transmitted on the PHICH.

The Physical Broadcast Channel (PBCH) is transmitted in the preceding four OFDM symbols of the second slot of the first subframe of the radio frame. The PBCH carries system information necessary for the wireless device to communicate with the base station, and the system information transmitted through the PBCH is called a master information block (MIB). In comparison, system information transmitted on the PDSCH indicated by the PDCCH is called a system information block (SIB).

The PDCCH includes resource allocation and transmission format of downlink-shared channel (DL-SCH), resource allocation information of uplink shared channel (UL-SCH), paging information on PCH, system information on DL-SCH, and random access transmitted on PDSCH. Resource allocation of higher layer control messages such as responses, sets of transmit power control commands for individual UEs in any UE group, activation of voice over internet protocol (VoIP), and the like. A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

Control information transmitted through the PDCCH is called downlink control information (DCI). DCI is a resource allocation of PDSCH (also called DL grant), a PUSCH resource allocation (also called UL grant), a set of transmit power control commands for individual UEs in any UE group. And / or activation of Voice over Internet Protocol (VoIP).

There are several layers in the second layer. First, the Medium Access Control (MAC) layer is responsible for mapping various logical channels to various transport channels, and also for logical channel multiplexing to map multiple logical channels to one transport channel. Play a role. The MAC layer is connected to the upper layer RLC layer by a logical channel, and the logical channel includes a control channel for transmitting information of a control plane according to the type of information to be transmitted. It is divided into a traffic channel that transmits user plane information.

The Radio Link Control (RLC) layer of the second layer adjusts the data size so that the lower layer is suitable for transmitting data to the radio section by segmenting and concatenating data received from the upper layer. It plays a role. In addition, in order to guarantee various QoS required by each radio bearer (RB), TM (Transparent mode, transparent mode), UM (Un-acknowledged mode, no response mode), and AM (Acknowledged mode, Response mode). In particular, the AM RLC performs a retransmission function through an Automatic Repeat and Request (ARQ) function for reliable data transmission.

The Packet Data Convergence Protocol (PDCP) layer of the second layer is an IP containing relatively large and unnecessary control information for efficient transmission in a low bandwidth wireless section when transmitting IP packets such as IPv4 or IPv6. Performs Header Compression, which reduces the packet header size. This transmits only the necessary information in the header portion of the data, thereby increasing the transmission efficiency of the radio section. In addition, in the LTE system, the PDCP layer also performs a security function, which is composed of encryption (Ciphering) to prevent third-party data interception and integrity protection (Integrity protection) to prevent third-party data manipulation.

The radio resource control layer (hereinafter RRC) layer located at the top of the third layer is defined only in the control plane, and the settings (setting) and reset (Re) of radio bearers (abbreviated as RBs) are performed. It is responsible for the control of logical channels, transport channels, and physical channels in connection with setup and release. In this case, RB means a service provided by the second layer for data transmission between the terminal and the E-UTRAN.

If there is an RRC connection (RRC connection) between the RRC of the terminal and the RRC layer of the radio network, the terminal is in the RRC connected state (Connected mode), otherwise it is in the RRC idle state (Idle mode).

Hereinafter, the RRC state and the RRC connection method of the UE will be described. The RRC state refers to whether or not the RRC of the UE is in a logical connection with the RRC of the E-UTRAN. If the RRC state is connected, the RRC_CONNECTED state is called, and the RRC_IDLE state is not connected. Since the UE in the RRC_CONNECTED state has an RRC connection, the E-UTRAN can grasp the existence of the UE in units of cells, and thus can effectively control the UE. On the other hand, the UE in the RRC_IDLE state cannot identify the existence of the UE by the E-UTRAN, and the core network manages the unit in a larger tracking area (TA) unit than the cell. That is, the terminal in the RRC_IDLE state is only detected whether the terminal exists in a larger area than the cell, and the terminal must transition to the RRC_CONNECTED state in order to receive a normal mobile communication service such as voice or data. Each TA is identified by a tracking area identity (TAI). The terminal may configure a TAI through a tracking area code (TAC), which is information broadcast in a cell.

When the user first turns on the power of the terminal, the terminal first searches for an appropriate cell, then establishes an RRC connection in the cell, and registers the terminal's information in the core network. Thereafter, the terminal stays in the RRC_IDLE state. The terminal staying in the RRC_IDLE state selects a cell (re) as needed and looks at system information or paging information. This is called camping on the cell. When it is necessary to establish an RRC connection, the UE staying in the RRC_IDLE state makes an RRC connection with the RRC of the E-UTRAN through an RRC connection procedure and transitions to the RRC_CONNECTED state. There are several cases in which the UE in RRC_IDLE state needs to establish an RRC connection. For example, when uplink data transmission is necessary due to a user's call attempt, or when a paging signal is received from E-UTRAN, Send a response message.

A non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

The following describes the NAS layer shown in FIG. 3 in detail.

Evolved Session Management (ESM) belonging to the NAS layer performs functions such as Default Bearer management and Dedicated Bearer management, and is responsible for controlling the terminal to use the PS service from the network. The default bearer resource is characterized in that it is allocated from the network when it is connected to the network when it first accesses a specific Packet Data Network (PDN). At this time, the network allocates an IP address usable by the terminal so that the terminal can use the data service, and also allocates QoS of the default bearer. LTE supports two types of bearer having a guaranteed bit rate (GBR) QoS characteristic that guarantees a specific bandwidth for data transmission and reception, and a non-GBR bearer having a best effort QoS characteristic without guaranteeing bandwidth. In case of Default bearer, Non-GBR bearer is assigned. In the case of a dedicated bearer, a bearer having a QoS characteristic of GBR or non-GBR may be allocated.

The bearer allocated to the terminal in the network is called an evolved packet service (EPS) bearer, and when the EPS bearer is allocated, the network allocates one ID. This is called EPS Bearer ID. One EPS bearer has QoS characteristics of a maximum bit rate (MBR), a guaranteed bit rate (GBR), or an aggregated maximum bit rate (AMBR).

Meanwhile, in FIG. 3, an RRC layer, an RLC layer, a MAC layer, and a PHY layer located under the NAS layer are collectively referred to as an access stratum (AS).

5a is a flowchart illustrating a random access procedure in 3GPP LTE.

The random access procedure is used for the UE 10 to obtain UL synchronization with the base station, that is, the eNodeB 20 or to be allocated UL radio resources.

The UE 10 receives a root index and a physical random access channel (PRACH) configuration index (configuration index) from the eNodeB 20. Each cell has 64 candidate random access preambles defined by a Zadoff-Chu (ZC) sequence, and the root index is a logical index for the UE to generate 64 candidate random access preambles.

Transmission of the random access preamble is limited to a specific time and frequency resource for each cell. The PRACH configuration index indicates a specific subframe and a preamble format capable of transmitting the random access preamble.

UE 10 transmits a randomly selected random access preamble to eNodeB 20. The UE 10 selects one of the 64 candidate random access preambles. Then, the corresponding subframe is selected by the PRACH configuration index. UE 10 transmits the selected random access preamble in the selected subframe.

Upon receiving the random access preamble, the eNodeB 20 sends a random access response (RAR) to the UE 10. The random access response is detected in two steps. First, the UE 10 detects a PDCCH masked with a random access-RNTI (RA-RNTI). The UE 10 receives a random access response in a medium access control (MAC) protocol data unit (PDU) on the PDSCH indicated by the detected PDCCH.

5b illustrates a connection process in a radio resource control (RRC) layer.

As shown in FIG. 5B, an RRC state is shown depending on whether RRC is connected. The RRC state refers to whether or not an entity of the RRC layer of the UE 10 is in a logical connection with an entity of the RRC layer of the eNodeB 20. If the RRC state is connected, the RRC state is connected. A state that is not connected is called an RRC idle state.

Since the UE 10 in the connected state has an RRC connection, the E-UTRAN may determine the existence of the corresponding UE in units of cells, and thus may effectively control the UE 10. On the other hand, the UE 10 in the idle state cannot be understood by the eNodeB 20, and is managed by a core network in units of a tracking area, which is a larger area than a cell. The tracking area is a collection unit of cells. That is, the idle state UE (10) is identified only in the presence of a large area unit, in order to receive the normal mobile communication services such as voice or data, the terminal must transition to the connected state (connected state).

When the user first powers up the UE 10, the UE 10 first searches for a suitable cell and then remains in an idle state in that cell. When the UE 10 staying in the idle state needs to establish an RRC connection, the UE 10 establishes an RRC connection with the RRC layer of the eNodeB 20 through an RRC connection procedure and performs an RRC connection state ( connected state).

There are several cases in which the UE in the idle state needs to establish an RRC connection. For example, a user's call attempt or an uplink data transmission is necessary, or a paging message is received from EUTRAN. In this case, the response message may be transmitted.

In order to establish an RRC connection with the eNodeB 20, the UE 10 in an idle state must proceed with an RRC connection procedure as described above. The RRC connection process is largely a process in which the UE 10 sends an RRC connection request message to the eNodeB 20, and the eNodeB 20 transmits an RRC connection setup message to the UE 10. And a process in which the UE 10 transmits an RRC connection setup complete message to the eNodeB 20. This process will be described in more detail with reference to FIG. 5B.

1) When the UE 10 in idle state attempts to establish an RRC connection due to a call attempt, a data transmission attempt, or a response to the paging of the eNodeB 20, the UE 10 first performs an RRC connection. A RRC connection request message is transmitted to the eNodeB 20.

2) When the RRC connection request message is received from the UE 10, the eNB 20 accepts the RRC connection request of the UE 10 when the radio resources are sufficient, and establishes an RRC connection, which is a response message (RRC connection). setup) message is transmitted to the UE 10.

3) When the UE 10 receives the RRC connection setup message, the UE 10 transmits an RRC connection setup complete message to the eNodeB 20. When the UE 10 successfully transmits an RRC connection establishment message, the UE 10 establishes an RRC connection with the eNodeB 20 and transitions to the RRC connected mode.

On the other hand, recently, research on communication that occurs between devices or between devices and servers without human interaction, that is, without human intervention, that is, MTC (Machine Type Communication) has been actively researched.

MTC communication is also called Internet of Things (IoT) communication because there is no human intervention. It is called CIoT to perform IoT communication on a cellular basis, not on a wireless LAN such as Wi-Fi. Unlike wireless LAN, CIoT supports not only IP-based communication but also IP-based communication.

Meanwhile, in order to support CIoT service, 3GPP has improved a physical layer, that is, a Radio Access Technology (RAT). The improved RAT is called Narrowband-IoT (NB-IoT).

As such, it is expected that CIoT devices using NB-IoT generally transmit and receive a small amount of data. However, in order for a CIoT device to transmit and receive data, a large number of signals must be exchanged with the base station in advance. In order to transmit and receive such a small amount of data, transmitting and receiving a large number of control signals in advance may be inefficient.

In order to solve this problem, there are attempts to optimize using a control plane (CP) in an evolved packet service (EPo) for CIoT and an attempt to optimize using a user plane (UP).

On the other hand, there has recently been a discussion to be able to transfer data more quickly. This is called early data transmission (EDT).

However, there was a technically impossible problem in applying EPS optimization and EDT together.

Therefore, one disclosure of the present specification is intended to propose a solution that can solve the above problems.

In order to achieve the above object, one disclosure of the present specification provides a method for a base station to support Early Data Transmission (EDT). The method may include receiving a first message from a mobility management entity (MME). The first NAS message may include downlink data. The method may further include determining that there is no additional data other than the downlink data based on the reception of the first NAS message.

The method may further include the base station transmitting an initial UE (Initial User equipment) message to the MME. The initial UE message may include data of the UE according to the EDT.

The first NAS message may include a downlink non-access-stratum transport message.

The method may further include the base station transmitting a UE context resume request message to the MME.

In order to achieve the above object, one disclosure of the present specification provides a method for transmitting uplink (UL) data according to Early Data Transmission (EDT) by a wireless device including a Radio Resource Control (RRC) layer and an upper layer. . The method includes obtaining a release assistance indication (RAI) from the upper layer; Determining whether EDT is applicable based on the RAI; If it is determined that the EDT is applicable, the method may include transmitting an RRC request message including the UL data.

In the acquiring step, an RRC establishment cause and a call type may be further obtained.

The RRC request message including the UL data may be transmitted through the third message of the random access procedure.

The RRC request message may include one or more of an EPS bearer ID and an LC (Logical Channel) ID.

The RAI may indicate that subsequent UL data is not expected or only one DL (Downlink) data for the UL data may be expected.

The RRC request message may be an RRC connection resumption request message.

When the UL data is transmitted through a control plane (CP), an RRC connection resumption procedure may not be performed.

When the UL data is transmitted through a control plane (CP), the RRC request message may be a different message from the RRC connection resume request message.

In order to achieve the above object, one disclosure of the present specification provides a method for transmitting uplink (UL) data according to Early Data Transmission (EDT) by a wireless device including a Radio Resource Control (RRC) layer. The method includes transmitting a third message of a random access procedure to a base station; And receiving a fourth message of a random access procedure from the base station. The third message may include an RRC connection resume request message for performing an RRC connection resume procedure in an RRC suspend state. The RRC connection resume request message may include the UL data according to the EDT.

The fourth message may include DL (Downlink) data.

The fourth message may include one or more of an RRC connection resume message, an RRC connection setup message, and an RRC connection rejection message.

In order to achieve the above object, one disclosure of the present specification provides a wireless device for transmitting uplink (UL) data according to Early Data Transmission (EDT). The wireless device includes a transceiver; And a processor that controls the transceiver and includes a radio resource control (RRC) layer and an upper layer. When the RRC layer of the processor obtains Release Assistance Indication (RAI) from the upper layer, the RRC layer may determine whether EDT is applicable based on the RAI. If it is determined that the EDT is applicable, the RRC layer of the processor may transmit an RRC request message including the UL data.

According to the disclosure of the present specification, the above-described problems of the prior art are solved. Specifically, according to the disclosure of the present specification, the CIoT device can perform EDT (Early Data Transmission), thereby enabling power saving.

1 is a structural diagram of an evolved mobile communication network.

Figure 2 is an exemplary view showing the architecture of a general E-UTRAN and a general EPC.

3 is an exemplary diagram illustrating a structure of a radio interface protocol in a control plane between a UE and an eNodeB.

4 is another exemplary diagram illustrating a structure of a radio interface protocol in a user plane between a terminal and a base station.

5a is a flowchart illustrating a random access procedure in 3GPP LTE.

5b illustrates a connection process in a radio resource control (RRC) layer.

6 shows an example of machine type communication (MTC) communication.

7 shows a series of procedures that a CIoT device performs for data communication.

8 is a signal flow diagram illustrating a suspension procedure initiated by a base station.

9 is a signal flow diagram illustrating a connection resumption procedure initiated by a CIoT device.

10A and 10B illustrate a procedure of transmitting data by a CIoT device according to control plane (CP) CIoT EPS optimization.

11 illustrates a procedure of transmitting data by a CIoT device according to user plane (UP) CIoT EPS optimization.

12A and 12B are exemplary views illustrating transmission and reception of a context resume request message between the base station and the MME illustrated in FIG. 11.

13 is an exemplary flow diagram illustrating a procedure for transmitting data early according to an EDT.

14A and 14B are exemplary flowcharts illustrating a procedure of transmitting data according to an EDT.

15 shows an example of EDT application for UP CIoT optimization.

16 is a block diagram illustrating a configuration of a CIoT device 100 and a network device according to an embodiment of the present invention.

Although the present invention is described based on the Universal Mobile Telecommunication System (UMTS) and the Evolved Packet Core (EPC), the present invention is not limited to such a communication system, but also to all communication systems and methods to which the technical spirit of the present invention can be applied. Can be applied.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. In addition, the technical terms used in the present specification should be interpreted as meanings generally understood by those skilled in the art unless they are specifically defined in this specification, and are overly inclusive. It should not be interpreted in the sense of or in the sense of being excessively reduced. In addition, when the technical terms used herein are incorrect technical terms that do not accurately represent the spirit of the present invention, it should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In the present application, the term “consisting of” or “having” should not be construed as necessarily including all of the various components, or various steps described in the specification, and some of the components or some steps may not be included. It should be construed that it may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be connected or connected to another component, it may be directly connected to or connected to the other component, but other components may be present in between. On the other hand, when a component is mentioned as being directly connected or directly connected to another component, it should be understood that no other component exists in the middle.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and should not be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

In the accompanying drawings, although a user equipment (UE) is illustrated as an example, the illustrated UE may be referred to in terms of terminal, mobile equipment (ME), and the like. In addition, the UE may be a portable device such as a laptop, a mobile phone, a PDA, a smart phone, a multimedia device, or a non-portable device such as a PC or a vehicle-mounted device.

Definition of Terms

Before describing with reference to the drawings, in order to help the understanding of the present invention, terms used herein will be briefly defined.

UMTS: Abbreviation for Universal Mobile Telecommunication System, which means the third generation mobile communication network.

UE / MS: means User Equipment / Mobile Station, terminal equipment.

EPS: stands for Evolved Packet System and means a core network supporting a Long Term Evolution (LTE) network. UMTS evolved network

PDN (Public Data Network): Independent network where the server providing the service is located

PDN connection: Connection from the terminal to the PDN, that is, association (connection) between the terminal represented by the IP address and the PDN represented by the APN.

PDN-GW (Packet Data Network Gateway): Network node of EPS network that performs UE IP address allocation, Packet screening & filtering, Charging data collection

Serving GW (Serving Gateway): Network node of EPS network that performs mobility anchor, packet routing, idle mode packet buffering, Triggering MME to page UE function

PCRF (Policy and Charging Rule Function): Node of EPS network that performs policy decision to apply differentiated QoS and charging policy dynamically by service flow

APN (Access Point Name): The name of the access point managed by the network, which is provided to the UE. That is, a string that refers to or distinguishes a PDN. In order to connect to the requested service or network (PDN), the P-GW passes through the P-GW. The name (string) predefined within the network to find this P-GW (example) internet.mnc012.mcc345.gprs

Tunnel Endpoint Identifier (TEID): End point ID of a tunnel established between nodes in a network, and is set for each section in bearer units of each UE.

NodeB: A base station of a UMTS network, which is installed outdoors, and a cell coverage scale corresponds to a macro cell.

eNodeB: A base station of an evolved packet system (EPS), which is installed outdoors, and a cell coverage size corresponds to a macro cell.

(e) NodeB: A term referring to NodeB and eNodeB.

MME, which stands for Mobility Management Entity, serves to control each entity in EPS to provide session and mobility for the UE.

Session: A session is a channel for data transmission. The unit may be a PDN, a bearer, or an IP flow unit. The difference in each unit can be divided into the entire target network unit (APN or PDN unit), the QoS classification unit (Bearer unit), and destination IP address unit as defined in 3GPP.

PDN connection (connection): A connection from the terminal to the PDN, that is, the association (connection) between the terminal represented by the IP address and the PDN represented by the APN. This means an inter-entity connection (terminal-PDN GW) in the core network so that a session can be established.

UE Context: Context information of UE used to manage UE in the network, ie Context Information composed of UE id, mobility (current location, etc.), session attributes (QoS, priority, etc.)

OMA DM (Open Mobile Alliance Device Management) is a protocol designed to manage mobile devices such as mobile phones, PDAs, portable computers, etc., and includes device configuration, firmware upgrade, and error report. Perform a function

OAM (Operation Administration and Maintenance): OAM is a group of network management functions that provides network fault indication, performance information, and data and diagnostic functions.

NAS Configuration MO (Management Object): A MO (Management Object) used to set (set) parameters related to NAS functions to the UE.

NAS (Non-Access-Stratum): Upper stratum of the control plane (control plane) between the UE and the MME. Supports mobility management, session management, and IP address management between UE and network

MM (Mobility Management) operation / procedure: An operation or procedure for mobility control / management / control of a UE. The MM operation / procedure may be interpreted as including one or more of the MM operation / procedure in the CS network, the GMM operation / procedure in the GPRS network, and the EMM operation / procedure in the EPS network. The UE and the network nodes (MME, SGSN, MSC) send and receive MM messages to perform MM operation / procedure.

SM (Session Management) operation / procedure: An operation or procedure for controlling / managing / processing / handling a user plane and / or bearer context / PDP context of a UE. SM operation / procedure may be interpreted as including one or more of SM operation / procedure in GPRS network and ESM operation / procedure in EPS network. The UE and the network nodes (MME, SGSN) exchange SM messages to perform SM operations / procedures.

PLMN: Abbreviation for Public Land Mobile Network, which means the network identification number of the operator. In the roaming situation of the UE, PLMN is divided into Home PLMN (HPLMN) and Visited PLMN (VPLMN).

CIoT: Abbreviation for Cellular Internet of Things, which means performing based on IoT communication.

Narrowband-IoT: For CIoT, means RAT (Radio Access Technology) improved in 3GPP. That is, it means a network operated with a bandwidth of up to 180 kHz (corresponding to one PRB).

Control plane CIoT EPS optimization: signaling optimization on the control plane to enable efficient transmission of user data (IP-based or non-IP-based or SMS-based user data)

User plane CIoT EPS optimization: Signaling optimization on the user plane to enable efficient transmission of user data (IP based or non-IP based or SMS based user data)

UEs that support CIoT EPS optimization: UEs that support control plane CIoT EPS optimization or user plane CIOT EPS optimization and one or more other CIoT EPS optimizations

NB-S1 mode: refers to a mode that operates with improved radio access technology (RAT) for narrowband (NB) IoT.

WB-S1 mode: This refers to a mode that operates with general RAT, not RAT improved for NB IoT.

Hereinafter, the disclosure of the present specification will be described with reference to the drawings.

<MTC (Machine Type Communication) Communication>

Machine type communication (MTC) refers to communication between a machine, which excludes a person, and a device used here is called an MTC device. The service provided through the MTC device is different from the communication service in which a person intervenes and may be applied to various categories of services.

6 shows an example of machine type communication (MTC) communication.

Machine Type Communication (MTC) is an exchange of information through the base station 200 between MTC devices 100 without human interaction or information through a base station between the MTC device 100 and the MTC server 700. Say exchange.

The MTC server 700 is an entity that communicates with the MTC device 100. The MTC server 700 executes an MTC application and provides an MTC specific service to the MTC device.

The MTC device 100 is a wireless device that provides MTC communication and may be fixed or mobile.

<Power Saving Mode (PSM)>

On the other hand, due to the characteristics of the MTC device, instead of receiving the mobile terminating data (Mobile terminating data) infrequently, the mobile originating data (mobile originating data) can be transmitted periodically. Considering these characteristics, in order to maximize energy efficiency, the MTC device may operate in a power saving mode (hereinafter, referred to as 'PSM').

When entering the PSM state, the MTC device deactivates an Access Stratum (AS), so the PSM is similar to a power off state. However, in the PSM state, the MTC device may exist as registered in the network, and thus, the MTC device does not need to reattach to the network and does not need to re-establish a PDN connection. As such, the PSM state and the power-off state are differentiated.

Once the MTC device enters the PSM state, a mobile originated event such as periodic TAU / RAU or uplink data generation or detachment causes the MTC device to initiate some procedure in the network. Until you do that, you stay in the PSM state.

Even if the MTC device is in the PSM state, it may leave the PSM at any time when a mobile originating service is required. That is, even in the PSM state, the MTC device may activate the access layer (AS) at any time for the mobile originated service and resume operation of the idle mode.

On the other hand, when the mobile reachable timer expires and the active time of the MTC device expires, the MME may know that the MTC device has entered the PSM state, and therefore paging is impossible.

On the other hand, once the MTC device enters the PSM state, the mobile terminating service cannot be immediately received. In other words, when the MTC device enters the PSM state, a signal after a periodic tracking area update (TAU) or routing area update (RAU) procedure is received for a mobile terminating service. It may respond only during an active time period after a mobile originated event such as a transmission or data transmission.

Therefore, the PSM is only suitable for MTC devices that require infrequent outgoing and mobile terminating services and only for MTC devices that can tolerate a certain latency in communication.

On the other hand, the MTC device must request an active time long enough to enable the reception of potential mobile terminated services or data such as SMS.

If the MTC device wishes to use the PSM, the MTC device must request the value of the active time during every attach and TAU / RAU procedure. If the network supports PSM and the MTC device accepts to use the PSM, it assigns a value of an active time to the MTC device. The network may determine an activation time value to be allocated to the MTC device in consideration of the activation time value requested by the MTC device and the MME / SGSN configuration. If the value of the activation time allocated by the network is not satisfactory, the MTC device may request the value of its desired activation time only during the next TAU / RAU procedure period.

In addition, PTC-applicable MTC devices request periodic TAU / RAU timer values suitable for latency / responsiveness for mobile terminated services to the network during attach and TAU / RAU procedures. Done. If the network assigns a periodic TAU / RAU timer value to the MTC device but the MTC device is not satisfied, the MTC device only wants its own periodic TAU / RAU during the next TAU / RAU procedure. You can request a timer value.

<Cellular Internet of Things Communication>

MTC communication is also called Internet of Things (IoT) communication because there is no human intervention. It is called CIoT to perform IoT communication on a cellular basis, not on a wireless LAN such as Wi-Fi. Unlike wireless LAN, CIoT supports not only IP-based communication but also IP-based communication.

Meanwhile, in order to support CIoT service, 3GPP has improved a physical layer, that is, a Radio Access Technology (RAT). The improved RAT is called Narrowband-IoT (NB-IoT).

The improved RAT for the NB-IoT uses a physical layer optimized for very low power consumption (eg, carrier bandwidth is 180 kHz, subcarrier spacing is 3.75 kHz or 15 kHz).

<Optimization for data transmission and reception of CIoT devices>

Since the CIoT device transmits and receives a small amount of data, as described above, the CIoT device can operate in a network operated with an improved RAT for NB-IoT, that is, a bandwidth of up to 180 kHz (corresponding to one PRB). .

However, even if the CIoT device transmits and receives a small amount of data, the CIoT device has to send and receive a lot of signaling with the network in advance. This will be described with reference to FIG. 7.

7 shows a series of procedures that a CIoT device performs for data communication.

Hereinafter, a description will be given in order with reference to FIG. 7.

1 to 5) First, the CIoT device 100 performs a random access procedure for data communication. That is, the CIoT device 100 transmits a first message MSG1, for example, a random access preamble, to the base station 200. The CIoT device 100 receives a second message MSG2, for example, a random access response message, from the base station 200. Then, the CIoT device 100 transmits a third message (MSG3), for example, a scheduled message, to the base station 200. The scheduled message may include an RRC Connection Request message. Thereafter, the CIoT device 100 receives a fourth message MSG4, for example, an RRC connection setup message from the base station 200. Then, the CIoT device 100 transmits a fifth message MSG5, for example, an RRC connection complete message, to the base station 200. The RRC connection complete message may include a NAS service request message.

6-7) Then, the base station 200 transmits an S1-AP-based Initial UE message to the MME 510. The initial UE message may include the NAS service request message. The MME 510 transmits an S1-AP based initial context setup request message to the base station.

8 to 9), the base station 200 transmits an RRC security mode command (SMC) to the CIoT device and receives an RRC security mode command response.

10 to 11), the base station 200 transmits an RRC connection reconfiguration message to the CIoT device 100, and the CIoT device 100 sends an RRC connection reconfiguration complete message. Transmit to base station.

12-14) The base station 200 transmits an S1-AP based initial context setup complete message to the MME 510. Then, the MME 510 transmits a bearer modification request message to the S-GW 520 and receives a bearer modification response message from the S-GW 520.

15) As a ratio, the CIoT device 100 may perform data communication.

16-19) On the other hand, when data communication is completed and RRC connection is not needed, the base station 200 transmits an S1-AP based UE context release request message to the MME 510. Then, the MME 510 transmits a Release Access Bearer message to the S-GW 520. Then, the S-GW 510 transmits a Release Access Bearer Response message to the MME 510. The MME 510 transmits a S1-AP based UE context release command message to the base station.

20) The base station 200 transmits an RRC Connection Release message to the UE, and transmits an RRC Connection Release Complete message to the MME 510.

As described above, even if the CIoT device 100 transmits and receives a small amount of data, since the CIoT device 100 needs to exchange a large number of signals with the base station 200, there is an inefficient problem.

In particular, the CIoT device is expected to be located at a fairly high density within the coverage of the base station, in which case a significant number of signals can overload the network.

Therefore, to solve this problem, there are attempts to optimize using a control plane in an evolved packet service (EPS) for CIoT and an attempt to optimize using a user plane. Each will be described as follows.

1. Suspend and Resume Procedure for EPS Optimization

1-1. Suspend procedure

This procedure is used by the network to suspend connections if the UE and the network support User Plane CI Optimization EPS Optimization.

8 is a signal flow diagram illustrating a suspension procedure initiated by a base station.

1) The base station transmits an S1 UE Context Suspend Request message to the MME to initiate a connection suspension procedure. Specifically, the base station suspends the RRC connection of the CIoT device and instructs the MME to enter the ECM-IDLE. Data related to the S1-AP association, UE context and bearer context needed to resume the connection is maintained at the base station, CIoT device and MME.

The base station may include information on the recommended cell and the base station for paging in the S1 UE Context Suspend Request message. If available, the MME should store the information when used when paging a CIoT device.

The base station includes information on enhanced (ie, extended) coverage if possible in the S1 UE Context Suspend Request message.

2) The MME sends a Release Bearer Request message to the Serving GW requesting the release of all S1-U bearers for the CIoT device.

3) The S-GW releases all base station related information (address and downlink TEID) for the CIoT device and responds to the MME with a Release Bearer Access Response message. When the downlink packet for the CIoT device arrives, the S-GW begins to buffer the received downlink packet for the CIoT device and starts the network trigger service request procedure.

The S-GW informs the MME of the release of the S1-U bearer via a Release Access Bearer Response message.

4) The MME sends a S1-AP: UE Context Suspend Response message to the base station to successfully terminate the connection suspend procedure initiated by the base station. See TS 36.413 [36].

5) The base station transmits an RRC connection suspend message to suspend the RRC connection to the CIoT device.

When the AS layer of the CIoT device receives the RRC connection suspend message, it transmits an indication indicating that the RRC connection is suspended to the NAS layer.

Upon receiving the indication, the NAS layer of the CIoT device enters an EMM idle state. The NAS layer considers that the NAS signaling connection has been released. However, the NAS layer does not consider that even the safe exchange of NAS messages has ended.

1-2. Resumption Procedure

This procedure is used for resuming ECM connections by CIoT devices when the CIoT device and the network support user plane CIoT EPS optimization and the CIoT device has stored the information needed to perform the connection resumption procedure. Specifically, it is as follows.

While in the EMM idle state based on the pause indication, when the procedure of using the NAS message is initiated, the NAS layer of the CIoT device requests the AS layer to resume the RRC connection. To this end, the NAS layer delivers an RRC establishment cause and a call type to the AS layer. At this time, the NAS message has not yet been delivered to the AS layer.

Upon receiving an indication from the AS layer indicating that an RRC connection has been resumed, the NAS layer enters an EMM connected state. If the NAS message that is not delivered to the AS layer and is waiting is a service request message, a Control Plane Service Request (CPSR) message, or an Extended Service Request message, the NAS The message is not delivered. If the NAS message is another message, the NAS layer encrypts the message. And after the NAS layer enters the EMM connected state, it sends the message as a ratio.

9 is a signal flow diagram illustrating a connection resumption procedure initiated by a CIoT device.

1) The CIoT device initiates a random access procedure for the base station

2) The CIoT device triggers an RRC connection resumption procedure that includes information needed by the base station to access the AS context stored for the CIoT device. E-UTRAN performs security checks. EPS bearer state synchronization is performed between the CIoT device and the network. That is, when the radio bearer is not configured for the basic EPS bearer, the CIoT device does not set the radio bearer and internally removes the EPS bearer other than the control plane CIoT EPS bearer.

3) The base station notifies the MME that the RRC connection of the CIoT device has been resumed through the S1-AP UE context resumption request message including the cause of the RRC resumption. If the base station cannot accept all suspended bearers, the base station should include information about this fact in the rejected EPS bearer list. The MME goes into the ECM-CONNECTED state. The MME confirms that the UE has returned to the base station associated with the MME storing data related to the S1-AP association, the UE context and the bearer context.

If a default bearer is not accepted by the base station, all bearers associated with that bearer are treated as non-accepting bearers. The MME releases the non-acceptable and unconfigured bearers by triggering a bearer release procedure.

4) The MME responds to resumption of connection via an S1-AP UE context resume response message.

5) If the list of E-RABs cannot be resumed, the base station resets the radio bearer.

6) UL (uplink) data transmitted by the CIoT device can now be forwarded to the S-GW by the base station. The base station transmits UL data to the S-GW address and TEID stored during the connection suspension procedure. The S-GW transmits UL data to the PDN GW.

7) The MME sends a Modify Bearer Request message. The Modify Bearer Request message may include information on an address, S1 TEID, (DL), downlink packet delay notification request, RAT type, etc., to the base station for the EPS bearer.

8) S-GW sends Modify Bearer Response message. The message includes the address of the S-GW, TEID.

2. Control Plane (CP) CIoT EPS Optimization

This is a method for transmitting data in a packet data unit (PDU) of the NAS layer. That is, when the CIoT device and the MME use the control plane CIoT EPS optimization, the CIoT device and the MME may transmit data to the NAS PDU including the EPS bearer ID of the associated PDN connection. Control plane (SRB +) for sending NAS messages such as attach and tracking area update (TAU) in the NAS layer without using user plane setup (DRB + S1-U path) required for existing data transfer Data is transmitted through S1-AP). To this end, the S11-U path is newly defined between the MME and the S-GW. Data may be transmitted through the newly defined S11-U path. At this time, the security of the data is used in the NAS layer security instead of the security of the AS layer. As such, since security of the AS layer is unnecessary, a security mode command (SMC) procedure or the like may be omitted. In addition, the required RRC signaling is reduced even when switching the RRC connected mode.

This will be described with reference to the drawings.

10A and 10B illustrate a procedure of transmitting data by a CIoT device according to control plane (CP) CIoT EPS optimization.

As can be seen with reference to FIGS. 10A and 10B, the CIoT device 100 may include data in a NAS service request message included in a fifth message MSG5 of the random access procedure, for example, an RRC connection complete message, and transmit the data. have.

That is, in comparison with FIG. 7 and FIG. 10A, in FIG. 7, the CIoT device 100 may transmit data in the fifteenth process. However, in FIG. 10A, the CIoT device 100 may transmit data in the fifth process. It can be efficiently transmitted.

3. User Plan (UP) CIoT EPS Optimization

If there is no data transmission and reception, instead of releasing (deleting) the UE context (that is, the ID (or UE ID), AS security information, etc. of the CIoT device) stored in the CIoT device and the base station, the context is maintained. In addition, when there is no data transmission and reception, the CIoT device performs an RRC suspend procedure instead of performing an S1 release procedure. Therefore, when the CIoT device requests the RRC connection again, it can quickly switch from the RRC idle mode to the RRC connected mode. That is, instead of performing a service request procedure for setting up a user plane, an RRC connection resume procedure is performed. Therefore, the number of RRC signals to be transmitted and received in order for the CIoT device to switch from the RRC idle mode (EMM-IDLE) to the RRC connected mode (EMM-CONNECTED) is significantly reduced.

11 illustrates a procedure of transmitting data by a CIoT device according to user plane (UP) CIoT EPS optimization.

0) First, if there is no data transmission and reception, instead of canceling (deleting) the UE context stored in the CIoT device 100 and the base station 200, the context is maintained, and the RRC connection is suspended instead of performing the S1 release procedure. ) Procedures were performed. As such, the NAS layer enters the ECM idle state.

1 to 3), if data communication is needed again, the NAS layer of the CIoT device 100 triggers a service request procedure, a TAU procedure, or an attach procedure. The NAS layer generates a NAS message and waits.

4) The NAS layer delivers the RRC establishment cause and call type to the AS layer. At this time, the NAS message is not delivered.

5a-5d) The AS layer of the CIoT device 100 transmits a first message (ie, MSG1) (eg, a random access preamble) of a random access procedure to the base station 200. The CIoT device 100 receives a second message (ie, MSG2) (eg, a random access response) of a random access procedure from the base station 200. Then, the AS layer of the CIoT device 100 includes the RRC connection resumption request message in the third message (ie, MSG3) (eg, scheduled message) of the random access procedure and transmits the message. In this case, a resume ID is included in the RRC connection resume request message. The base station 200 transmits a fourth message (ie, MSG4) (eg, RRC connection resumption completion message) of a random access procedure to the CIoT device 100. At this time, the RRC connection resume complete message includes a resume ID and a bearer descriptor.

6-7) The base station 200 transmits an S1-AP based UE context resumption request message to the MME 510. The MME sends a context resume response message to the base station.

8-9) On the other hand, the AS layer of the CIoT device 100 transmits an indication indicating the success of resumption to the NAS layer. The NAS layer enters an EMM connected mode.

10) The NAS layer forwards the waiting NAS message to the AS layer.

11) Then, the AS layer of the CIoT device 100 transmits a fifth message (ie, MSG5) (eg, RRC connection resumption completion message) of a random access procedure to the base station 200. The resume complete message may include the NAS message.

In comparison with FIG. 7 and FIG. 11, in FIG. 7, the CIoT device 100 may transmit data in a fifteenth process. However, in FIG. 11, the CIoT device 100 may transmit data in an eleventh process. It can be improved efficiently.

12A and 12B are exemplary views illustrating transmission and reception of a context resume request message between the base station and the MME illustrated in FIG. 11.

As shown in FIGS. 12A and 12B, the base station sends a UE context resume request message to request resume. At this time, when the MME accepts the resumption, as shown in FIG. 12A, the UE context resume response message is transmitted. However, when the MME refuses to resume, as shown in FIG. 12B, a UE context resume failure message is sent.

If the MME transmits a context resume failure message, the base station performs an RRC release procedure.

Specifically, when the MME cannot resume one E-RAB, by sending a context resume failure message to the base station, the CIoT device related logic S1 connection is released. When the base station receives the failure message, it releases the RRC connection and releases all related signaling and user data transmission resources.

4.early data transmission (EDT)

 On the other hand, there has recently been a discussion to be able to transfer data more quickly. This is called EDT. In the EDT, DL data is transmitted between MSG1 and MSG5 of the random access procedure, that is, DL data through MSG2 or MSG4 for DL data and UL data through MSG3 for UL data.

According to such an EDT, the CIoT device can quickly perform early transmission. Once the early transmission is complete, the CIoT device can save power by disconnecting the RRC early.

13 is an exemplary flow diagram illustrating a procedure for transmitting data early according to an EDT.

1) The upper layer of the CIoT device 100 triggers the connected mode.

2a-2b) The CIoT device 100 transmits MSG1 (ie, random access preamble) of a random access procedure. The MSG1 may indicate for early data transmission. The base station 200 transmits the MSG2 (ie, random access response message) of the random access procedure.

3a) The CIoT device 100 resumes DRB and SRB when transmitting the UP data in the stored CIoT configuration. The AS layer (ie, RRC layer) of the CIoT device 100 enters an RRC connected mode.

3b) The AS layer (ie, RRC layer) of the CIoT device 100 transmits MSG3 of a random access procedure. The MSG3 includes an RRC message. In the case of CP EDT, the RRC message may include a NAS message including a NAS PDU, and in the case of an UP EDT, the MSG3 may include UP data.

4a-4c) When CP EDT is used, the base station 200 may include a NAS PDU in an S1-AP based Initial UE message and transmit the same.

If 4d-4e) or UP EDT is used, the base station may transmit UL data after transmitting the S1-AP based UE context resumption request message.

4f) On the other hand, if there is DL data to be delivered to the CIoT device 100 and CP EDT is used, the MME 510 may deliver a DL NAS Transport message including a NAS PDU to the base station 200. .

4g) or DL data to be delivered to the CIoT device 100, and when UP EDT is used, DL data may be delivered to the base station 200 through the S1-U interface.

4h), the base station 200 and the MME 510 may transmit and receive an S1-AP based UE context release message.

5) When CP EDT is used, the base station 200 may deliver a NAS PDU including DL data to the CIoT device 100. Alternatively, when the UP EDT is used, the base station 200 may transmit DL data to the CIoT device 100.

<Problems to be solved through the disclosure of the present specification>

The EDT as described above has the following problems.

1. The first problem

First, there is a problem in which data is transmitted through a CP path or an UP path. Specifically, it is as follows.

In general, a CIoT device using CIoT EPS optimization includes an indication indicating whether CP CIoT EPS optimization or UP CIoT EPS optimization is included in MSG5 of the random access procedure.

The NAS layer of the CIoT device informs the AS layer of the requested CIoT EPS optimization. That is, in NB (narrowband) communication, when the NAS layer of the CIoT device requests an RRC connection to the AS layer and requests the use of an EMM registered state without a PDN connection, or requests the use of UP CIoT EPS optimization. The CIoT device delivers an indication of the requested CIoT EPS optimization to the AS layer. If the CIoT device requests the use of S1-U data delivery without using the UP CIoT optimization, the CIoT device sends an indication for the UP CIoT EPS optimization to the AS layer. On the other hand, in WB (WideBand) communication, the NAS layer of the CIoT device requests an RRC connection to the AS layer, requesting the use of an EMM registered state without a PDN connection, or using CP CIoT EPS optimization or UP CIoT EPS optimization. When requesting the use, the CIoT device delivers an indication of the requested CIoT EPS optimization to the AS layer.

Then, the AS layer generates an RRC connection setup complete message and sends the RRC connection resumption complete message to MSG5. In this case, when CIoT EPS optimization is supported, the AS layer includes an attachWithoutPDN-connectivity indication in the message. In addition, the AS layer includes an up-CIoT-EPS-Optimization indication or a cp-CIoT-EPS-Optimization indication in the message according to the request of the NAS layer.

However, in case of early transmission according to the EDT, UL data is included in the MSG3 and transmitted. When the CIoT device receives the MSG4, the UL data is not transmitted and the RRC connection is released.

That is, when early transmission is performed according to the EDT, since the RRC connection resumption completion message including the up-CIoT-EPS-Optimization indication or the cp-CIoT-EPS-Optimization indication is not transmitted, the base station updates the UL data. You do not know whether to send on the path or on the CP path.

A simple solution for solving this problem may be that only one of the CP EDT and the UP EDT is supported in the EDT.

On the other hand, when the transition from the suspend state to the resume state, conventionally all bearers of the UP has been activated again. However, in the pause state, there is a problem that there is no procedure for resuming only CP.

2. Second problem

In the case of performing the UP EDT according to the conventional or UP EDT scheme described in FIG. 9, when the CIoT device transmits UL data through the MSG3, there is no problem in the CIoT device confirming whether the UL data transmission is successful. . Specifically, with reference to the pause and resume procedure as follows.

If the CIoT device in the EMM idle state according to the suspend indication transmits with UL data via MSG3 (ie, including the RRC connection resume request message), the base station determines whether to accept the resume. If the base station accepts the resumption, the base station transmits the MSG4 (including the RRC connection resume message) to the CIoT device, and then transmits a UE context resume request message to the MME. The CIoT device receiving the MSG4 internally performs the release. The CIoT device then transitions to the EMM idle state. In this case, the CIoT device may switch to the eDRX or PSM mode to save power.

On the other hand, if the MME receives the UE context resume request message, but can not resume any one of the E-RAB, by sending a UE context resume failure message to the base station, the logical S1-connection associated with the CIoT device is released. . Upon receiving the UE context resume failure message, the base station releases the RRC connection and releases all associated signaling. The base station also releases resources for user data transfer.

This causes the following problems.

If the UL data intended to be transmitted by the CIoT device is transmitted through the CP path, the resume procedure may be unnecessary because the UP bearer does not need to be restarted. Therefore, the MME sends a UE context resume failure message to the base station, and the base station performs an RRC connection release procedure according to the failure message. However, upon receiving the MSG4, the CIoT device performs the RRC connection release as described above, and then switches to the EMM-IDLE mode and further to eDRX or PSM. For this reason, the base station cannot perform the RRC disconnection. However, the problem here is that the CIoT device switches to the EMM idle state and not to the eDRX or PSM state without knowing whether the UL data transmission is successful or failed. If the CIoT device can receive the RRC connection release request message from the base station, it is possible to infer whether the UL data is successful through the message, but the CIoT device determines that the success of the UL data has not been received. Can not.

3. Third problem

According to the conventional operation, in order to use the PSM, the CIoT device needs to request the MME to accept the use of the PSM through the TAU procedure. However, when the CIoT device supports the EDT, the UL data is transmitted through the MSG3 of the random access procedure, and the RRC connection is released before the TAU request message is transmitted. In this case, the CIoT device cannot use the PSM, and thus the power saving effect cannot be obtained. In this case, even if there is a gain due to the EDT, the disadvantage that occurs when the PSM cannot be used may be greater.

Disclosure of the Invention

Hereinafter, it is assumed that the CIoT device can support the EDT. Hereinafter, it is assumed that when the CIoT device transmits UL data, when the CIoT device is in the EMM idle state according to the pause indication and in the RRC idle state according to the pause indication, the resume procedure is performed.

I. First Initiation: Preliminary Preparation for EDT

The CIoT device and the network node perform an operation of checking each other's capability information for the EDT according to one of the following options.

Option A) When checking only capability information for EDT

In order to perform the EDT, the CIoT device should inform the network node of the capability information of its EDT. To this end, the CIoT device may transmit after setting the EDT support bit to “EDT supported” in the capability information field in the attach request message for performing the attach procedure or the TAU request message for performing the TAU procedure. If the network node (eg, MME) receiving the attach request message or the TAU request message also supports the EDT, the EDT supported " is set in the EPS network feature support field in the attach accept message or the TAU accept message. , May be transmitted to the CIoT device.

Option B) Identify EDT capable bearers with capability information for EDT support

Unlike option A, in addition to capability information for EDT support, an operation of checking bearer information supporting EDT may be performed.

B-1) When checking bearer information supporting EDT together with attach procedure or TAU procedure

The CIoT device transmits to the network node an attach request message or a TAU request message including bearer information supporting the EDT in addition to the capability information for the EDT support.

The network node (eg, MME) confirms the attach request message or the TAU request message. In this case, when the network node also supports the EDT, an attach accept message or a TAU accept message including bearer information to be used for the EDT among the bearers supporting the EDT is transmitted.

On the other hand, even if the CIoT device does not include bearer information in the message, the network node (eg, MME) checks the bearer context of the current CIoT device, and provides information on the bearer supporting the EDT according to the confirmation. It may be included in the attach accept message or the TAU accept message and transmitted to the CIoT device.

B-1) In case of separately checking bearer information supporting EDT

Capability information verification for EDT support may be performed according to option A. Confirmation of the bearer supporting the EDT may be performed as follows.

When the CIoT device performs an ESM procedure (eg, PDN connection request procedure, bearer resource allocation request procedure, bearer resource modification procedure), information about a bearer supporting EDT is included in a protocol configuration option (PCO) or an extended PCO. Transmit to a network node (eg, P-GW).

When the network node (eg, P-GW) supports the EDT for the bearer, an indication indicating that the EDT is supported is included in the PCO or the Extended PCO and transmitted to the CIoT device. Through this process (ESM procedure), MME can also check bearer information supporting EDT.

The "EDT supported" may be expressed by subdividing the CP EDT and the UP EDT. In other words, when CP EDT is supported, it may be expressed as "CP EDT supported" and when "UP EDT is supported".

II. Second Initiation: UL Data Transmission

The second disclosure relates to a solution for solving the aforementioned first problem.

When the CIoT device transmits MSG3 (ie, RRC connection resumption request message) including UL data, whether the data should be transmitted on the CP path (that is, CP data (or data transmitted by CP EDT)) or CP Information on whether the EDT scheme is used) or whether to transmit on the UP path (that is, whether the UP data scheme or the UP EDT scheme is used) may be transmitted. Specifically, the operation of the CIoT device is as follows.

1) When the application layer of the CIoT device delivers data to be transmitted to a lower layer (for example, NAS layer or AS layer), whether the data to be transmitted is CP data (or data transmitted by CP EDT) or UP data (or UP). It also sends an indication indicating whether the data is transmitted by the EDT.

1-A) The following is included in the indication or delivered separately to a lower layer (eg, NAS layer or AS layer).

Information about whether the data is a small amount of data, and / or

(Following) information (or Release Assistance Indication (RAI)) on whether UL data transmission or DL data reception is not expected, and / or

Information about whether to perform EDT.

1-B) The CIoT device may consider the following cases according to the triggering path internally.

The application layer of the CIoT device sends the information to the AS layer via the NAS layer. In this case, the NAS layer may transmit the EPS bearer ID information to transmit the information to the AS layer. The point in time when the NAS layer delivers the information or EPS bearer ID information to the AS layer becomes a time point for transmitting the RRC establishment cause and the call type when the resumption procedure is triggered. Specifically, it is as follows.

If the suspend indication triggers a procedure to use the initial NAS message while in the EMM idle state, the CIoT device requests the lower layer to resume the RRC connection. At this time, the NAS layer delivers an indication for the EDT to the AS layer. In addition, the NAS layer delivers information on the EPS bearer ID to which data is transmitted, the RRC establishment cause, and the call type to the AS layer.

The AS layer of the CIoT device includes the data in the MSG3 (including the RRC connection resumption request message) of the random access procedure and transmits the data to the base station. The base station may accept or reject the resume request or indicate a fallback. If resume is refused or a fallback is instructed, an attempt is made to retransmit data through the conventional operation of the AS layer of the CIoT device.

When the data to be transmitted according to the EDT is CP data (or data transmitted by the CP EDT), the generated NAS message may be a control plane service request (CPSR) message. If resumption is refused or a fallback is instructed, retransmission is made through the data contained in the CPSR.

On the other hand, the information may be directly transmitted to the AS layer without passing through the NAS layer. That is, the application layer of the CIoT device may directly transfer the information to the AS layer. When the EPS bearer ID is not received from the upper layer, the AS layer may know the EPS bearer ID to which data is transmitted.

2) Upon receiving the UL data to be transmitted, the indication, and the information, the AS layer of the CIoT device determines that early transmission is necessary, and performs the following operation together with the resumption procedure.

2-A) The AS layer starts a random access procedure. Specifically, the AS layer of the CIoT device transmits MSG1, and upon successful reception of MSG2, transmits MSG3 (ie, including RRC connection resumption request message) including UL data to the base station.

2-B) At this time, the UL data is cryptographically secured and guaranteed by the AS security context (eg, authentication token, short MAC-I) stored in the AS layer of the CIoT device.

2-C) The MSG3 of the random access procedure contains the following indication.

An indication indicating whether CP data (or data transmitted by CP EDT) or UP data (or data transmitted by UP EDT), and / or

It includes EPS bearer ID or LC (Logical Channel) ID. In case of CP data (or data transmitted by CP EDT), the corresponding information may not be included.

3) When the base station receives the MSG3 including the UL data, it is checked whether the corresponding UL data is CP data (or data transmitted by the CP EDT) or UP data (or data transmitted by the UP EDT). The EPS bearer ID or LC ID may be used to determine whether CP data (or data transmitted by CP EDT) or UP data (or data transmitted by UP EDT). The base station transmits an S1-AP message to the MME as described below. The base station may determine whether to resume the corresponding EPS bearer by checking the received EPS bearer ID or LC ID. In this case, even if another EPS bearer is resumed, if the corresponding EPS bearer cannot be resumed, the base station transmits an RRC connection resume refusal message for notifying the CIoT device of the resumption refusal. The rejection message may include cause information indicating a reason for the rejection. In case of CP data (or data transmitted by CP EDT), it may not be necessary to perform resumption. In this case, the base station may immediately transmit CP data (or data transmitted by CP EDT) to the MME without performing resumption. In case of resuming the CP data (or data transmitted by the CP EDT), the UE context resumption request message may be transmitted to the MME.

3-A) If the data transmitted via MSG3 is UP data (or data transmitted by UP EDT), the resume procedure is performed. In other words, the base station sends a UE context resume request message to the MME. When the MME receives the UE context resume request message, the CIoT device resumes the EPS bearer desired to transmit, and then transmits a UE context resume response message to the base station. Meanwhile, even when the EPS bearer which the CIoT device wants to transmit is not resumed and another EPS bearer is resumed, the MME may transmit a UE context resume response message to the base station. However, in this case, since the EPS bearer for transmitting the UL data received from the CIoT device by the base station is not resumed, resuming another EPS bearer may be unnecessary. Therefore, it may be efficient to resume only the necessary EPS bearers.

Meanwhile, the following optimization operation may be performed during the resume procedure.

When the optimization is applied, the base station transmits the EPS bearer ID received from the CIoT device in the UE context resumption request message in step 2). When the base station receives the LC ID from the CIoT device, it can find the EPS bearer ID mapped to the LC ID, and then include the found EPS bearer ID in the message.

If the optimization is not applied, the base station may generally generate and transmit a UE context resume request message.

3-B) If the data transmitted by the CIoT device through the MSG3 is CP data (or data transmitted by the CP EDT), the base station extracts the RRC connection resume request message in the MSG3, and in the RRC connection resume request message. Extract the included UL data. The base station includes the extracted UL data in an S1-AP message and transmits it to the MME. The S1-AP message may be a reuse or modification of a general UE context resume request message or an Initial UE message, or a newly defined message. The S1-AP message may include a separate indication indicating that CP data (or data transmitted by CP EDT) is included. The specific operation is as follows.

In case of Initial UE message,

An Information Element (IE) may be added as a container for CP data (or data transmitted by CP EDT) in the Initial UE message to include CP data (or data transmitted by CP EDT). CP data (or data transmitted by CP EDT) may be included in the IE, or the CP data (or data transmitted by CP EDT) may be included in an existing NAS-PDU IE.

Only when the CP data (or data transmitted by the CP EDT) is included in the existing NAS-PDU IE, an indication indicating that the CP data (or data transmitted by the CP EDT) may be included.

-UE context resume request message

E-RAB Failed To Resume List is not included. As a container for CP data (or data transmitted by CP EDT) to contain CP data (or data transmitted by CP EDT), a new IE may be added in the message. CP data (or data transmitted by CP EDT) may be included in the newly added IE.

New S1-AP message

At least the message type, ID of S1-AP, may be included in the message.

The message includes CP data (or data transmitted by CP EDT). The message may include an indication that separate CP data (or data transmitted by CP EDT) is included.

4) When the MME receives the S1-AP message, it operates as described below.

4-A) For UP data (or data transmitted by UP EDT),

4-A-i) If the optimization of the process 3-A) is applied, the MME receiving this can resume only the E-RAB bearer corresponding to the received EPS bearer ID.

If the resumption of the E-RAB bearer succeeds, the UE context resume response message is transmitted to the base station.

The base station which receives this transmits corresponding UP data (or data transmitted by the UP EDT) through the resumed S1-U bearer without performing DRB setup with the CIoT device. After transmitting the UP data (or the data transmitted by the UP EDT), the base station may inform the CIoT device whether the UP data (or the data transmitted by the UP EDT) is successful. The RRC message indicating whether the transmission is successful may be a general RRC message (eg, an RRC disconnection message) or a new RRC message. The RRC message includes cause information indicating whether the UL data transmission has failed successfully.

 If the resumption of the E-RAB bearer fails, the UE context resume failure message is transmitted to the base station. The message includes cause information indicating whether or not the data transmission was successful. The cause information may indicate a specific reason for the failure. For example, the cause information may indicate that the requested EPS bearer ID cannot be resumed.

Upon receiving this, the base station may inform the CIoT device of the corresponding cause information while transmitting an RRC connection release message or an RRC resumption rejection message.

The CIoT device receiving this recognizes that data transmission has failed. The reason for the failure may be specifically recognized according to the cause information.

4-A-ii) If the optimization is not applied, the MME generates and transmits a UE context resume response message or a UE context resume failure message as conventionally.

4-B) In case of CP data (or data transmitted by CP EDT), the MME receiving the S1-AP message transmitted by the base station in step 4) has successfully resumed at the base station (eg, successfully resumed test). Recognizes that the data has been passed), checks the CP data (or data transmitted by the CP EDT) included in the corresponding S1-AP message and determines whether to transmit the corresponding CP data (or data transmitted by the CP EDT).

4-B-i) If the MME does not transmit CP data (or data transmitted by CP EDT) (rejects transmission), informs the CIoT device of the rejection and the reason for the rejection. To this end, the MME transmits an S1-AP message to the base station. The S1-AP message may be a reuse or modification of a general S1-AP message (eg, a Downlink NAS Transport message or a UE context resumption failure message) or a newly defined message.

When reusing or modifying a general S1-AP message, the S1-AP message used in the process 3-B) determines which S1-AP message to use. For example, when an Initial UE message is used in step 3-B), when a Downlink NAS Transport message or a UE context resume request message is used, a UE context resume failure message is used. The message may include cause information indicating the reason for the rejection.

At this time, if DL data to be transmitted to the CIoT device is waiting for the MME, it is transmitted together with the base station. The DL data may be included in the S1-AP message and transmitted.

4-B-ii) When the MME wants to transmit CP data (or data transmitted by CP EDT), it checks the EPS bearer ID to be transmitted and sends the CP data (or data transmitted by CP EDT) through an interface. Check if it should be sent. Specifically, the MME may check the PDN connection with the SCEF or P-GW based on the EPS bearer ID included in the message.

When the MME determines to transmit CP data (or data transmitted by the CP EDT) or when the transmission is successful, an S1-AP message may be transmitted to the base station or an S1 release procedure may be informed. The S1-AP message may be a reuse or modification of a general S1-AP message (eg, Downlink NAS Transport message or UE context resume failure message), or may be a newly defined message.

When reusing or modifying a conventional S1-AP message, it is determined which S1-AP message to use according to the S1-AP message used in step 3-B). For example, if an Initial UE message, Downlink NAS Transport message, or UE context resume request message is used in step 3-B), the UE context resume failure message is used. The message may include an indication indicating that transmission of CP data (or data transmitted by CP EDT) is successful.

4-C) Both UP data (or data transmitted by the UP EDT) and CP data (or data transmitted by the CP EDT) are transmitted together with the base station when DL data to be transmitted to the CIoT device is waiting in the MME.

4-Ci) In this case, the DL data is of a size that the base station can transmit in a general RRC message (e.g., MSG4 (i.e., RRC connection setup message, RRC connection rejection message, RRC connection resume message or RRC connection release message). Data (i.e., data of a size that can be transmitted to the EDT) The MME or S-GW recognizes the allowed size information of the data and transmits it only to the base station if the DL data is the allowed size. The operation may be performed only when there is no further buffered DL data other than the DL data for the CIoT device, specifically, the MME has DL data to be transmitted to the CIoT device and the DL data. In addition, when there is no longer buffered DL data, it may be notified to the base station. When transmitting a Downlink NAS Transport message including U (including the DL data), an indication indicating that there is no additional data to be transmitted may be included in the Downlink NAS Transport message and transmitted. Ensure that there is no additional data other than the NAS PDU (the DL data) The information about the allowed size of the data may be preset or signaling (e.g., from the base station to the MME and / or from the base station to the S-GW and / or Or MME or S-GW signaling through MME).

If the DL data is CP data (or data transmitted by the CP EDT), the MME determines whether the EDT is applied to the DL data. When EDT is applied to DL data, the MME includes CP data (or data transmitted by CP EDT) in a NAS message (e.g., CPSR message) to deliver to lower layer (i.e., S1-AP layer), and It sends the 'EDT' indication to the lower layer to indicate that it is an EDT. Upon receiving this, the lower layer transmits the NAS message including the CP data (or data transmitted by the CP EDT) and the EDT indication to the base station in an S1-AP message (eg, a downlink NAS transport message).

If the DL data is UP data (or data transmitted by the UP EDT), the S-GW determines whether to apply the EDT to the DL data. The MME may inform the S-GW when performing process 4) that the EDT application is activated for a specific bearer. Alternatively, the S-GW may know in advance through the first initiation whether EDT application for a specific bearer is activated. According to the above condition, when EDT is applied to DL data, the S-GW transmits UP data (or data transmitted by the UP EDT) to the base station. If the optimization of process 3-A) is applied, 'EDT' indication is sent to MME indicating EDT. Receiving the indication, the MME delivers an 'EDT' indication indicating the EDT to the lower layer (that is, the S1-AP layer). Upon receiving this, the lower layer transmits the EDT indication to the base station by including an S1-AP message (eg, a UE Context Release command message).

4-C-ii) If the DL data is CP data (or data transmitted by CP EDT), the S1-AP message including the DL data includes an indication indicating that the data is for EDT.

4-C-iii) If the corresponding DL data is UP data (or data transmitted by UP EDT), and the optimization of step 3-A) is applied, the following operation is performed.

If there is a resumed / established bearer for transmitting the DL data (eg, data of the same bearer as the bearer of UL data transmitted in step 4), it is transmitted to the base station.

If there is no resume / established bearer for transmitting the DL data (e.g., in step 4), the resume procedure does not operate when the UL data or signaling transmission is not the same bearer data as the bearer of the UL data transmitted. Or unsuccessful), an additional S1-U bearer and DRB should be established for transmitting the DL data.

In this case, as in the prior art, the S-GW transmits a downlink data notification (DDN) message to the MME.

The MME receiving the DDN transmits an E-RAB setup request message including the bearer information to establish the bearer. The E-RAB setup request message includes an E-RAB ID and related information (eg, E-RAB level QoS parameters) of a bearer to transmit the DL data. The MME receives and confirms the E-RAB setup response message that the E-RAB setup for the bearer was successfully performed and sends a DDN response message to the S-GW.

Upon receiving the DDN response message, the S-GW transmits the DL data to a base station.

4-C-iv) If pending (buffered) DL data cannot be sent to the EDT,

In case of downlink CP data (or data transmitted by CP EDT), a procedure for transmitting CP data (or data transmitted by CP EDT) is performed.

In the case of downlink UP data (or data transmitted by UP EDT) transmission, the MME performs a conventional operation for establishing an S1-U connection and a DRB as in the conventional operation. For example, if there is no UE context in the base station, an initial context setup procedure is performed. Or if the base station has a UE context, but the bearer is not activated, the E-RAB setup procedure is performed.

5) When the base station receives the S1-AP message of process 4), it operates as described below. At this time, when the DL data is waiting (buffering), the base station transmits the DL data to the CIoT device.

5-A) For UP data (or data transmitted by UP EDT),

If the optimization of 5-A-i) process 3-A) is applied,

In step 4), if the MME succeeds in resuming the corresponding E-RAB bearer, and the MME transmits a UE context resume response message to the base station, the base station receiving the same transmits the data through the resumed S1-U bearer. .

If the MME fails to resume the E-RAB bearer in step 4), and if the UE context resumption failure message is transmitted to the base station, the message includes cause information indicating whether the data transmission was successful. The cause information may indicate a specific reason for the failure. For example, the cause information may indicate that the requested EPS bearer ID cannot be resumed.

5-A-ii) Without applying the optimization of process 3-A)

If the MME succeeds in the process 4), when the MME transmits the UE context resume response message to the base station, the base station checks whether the EPS bearer for transmitting the UL data received in the process 3) is resumed. When the EPS bearer is resumed, the base station transmits the data through the resumed S1-U bearer.

When the MME fails to resume in step 4) and transmits a UE context resume failure message to the base station,

5-B) For CP data (or data transmitted by CP EDT), receive the S1-AP message described in step 4), and the base station recognizes the success or failure of the UL data transmission. When the CIoT device recognizes a transmission failure from the base station through the RRC message, the CIoT device may attempt to retransmit through the RRC connection that is not released. In detail, when the RRC connection is not released, the CIoT device may retransmit the MSG5 (that is, the RRC Connection setup complete message) or another RRC message.

5-C) The following applies to both UP data (or data transmitted by UP EDT) and CP data (or data transmitted by CP EDT). In the case of UP data (or data transmitted by UP EDT), the following applies regardless of applying optimization.

When the base station receives the S1-AP message including the DL data described in step 4) and recognizes that there is no additional data to be transmitted, the base station includes the corresponding DL data in the MSG4 and attempts transmission to the CIoT device. If the DL data is CP data, it is included in the RRC message of the MSG4. If the DL data is UP data, the DL data may be transmitted in a separate DTCH from the RRC message of the MSG4. The base station checks whether the DL data can be included in the MSG4, and if the DL data has a size that can be transmitted to the MSG4, the base station transmits the DL data including the DL data. When the base station transmits an MSG4 that does not include the DL data according to the conventional operation (ie, after transmitting the RRC connection setup message) when the DL data is a size that cannot be included in the MSG4 or fails to transmit to the MSG4, the RRC connection is performed. After switching to the connected state, the DL data transmission is attempted or included in the DL data S1-AP message to the MME, and an indication indicating DL transmission failure is transmitted to the MME. . The base station transmits an RRC message to the CIoT device. The RRC message may be an RRC connection release message or another RRC message. The RRC message includes cause information indicating the success or failure of the transmission. The cause information may indicate a specific reason in case of failure. For example, the cause information may indicate failure of resuming the corresponding EPS bearer.

In case of transmitting the DL data, the DL data may be transmitted by being included in an existing RRC message (eg, an MSG4 (ie, an RRC connection setup message, an RRC connection rejection message, an RRC connection resume message, or an RRC connection release message)). Or, the RRC message other than the RRC connection release message may be used as the message for transmitting the DL data, when the base station wants to transmit the RRC connection release message, the DL data is successfully transmitted to the AS layer of the CIoT device. The RRC disconnection message can then be sent to the CIoT device.

At the time when the base station transmits the RRC message to the CIoT device, when the CIoT device is in the RRC idle state (ie, the base station does not transmit the MSG4), an RRC message other than the RRC disconnection message may be transmitted. . The RRC message may be an RRC connection setup message or an RRC connection rejection message.

6) The CIoT device recognizes the success or failure of the UL data transmission. The CIoT device may specifically recognize the reason according to the cause information. In case of failure, retransmission can be attempted. In case of failure, the CIoT device may determine whether to retransmit according to the cause information. If UL data fails and a retransmission can be attempted, the NAS layer or the RRC layer of the CIoT device may perform retransmission in the EMM connected state or the RRC connected state without switching to the EMM idle state or the RRC idle state.

In the foregoing, the EDT indication may be represented by cause information.

In addition, in the above, even in case of CP data (or data transmitted by CP EDT), the CIoT device assumes transmission in the EMM idle state according to the pause indication. However, when transmitting CP data (or data transmitted by the CP EDT) according to the EDT, it may not be necessary to perform a resume procedure. This is because there is no need to establish a UL bearer when the UL data is CP data (or data transmitted by the CP EDT). Thus, when the CIoT device is in the EMM idle state according to the suspend indication, when the CP data (or data transmitted by the CP EDT) is transmitted in accordance with the EDT, the NAS layer of the CIoT device may enter the EMM idle state. Thereafter, CP data (or data transmitted by CP EDT) may be transmitted. In this case, when CP data (or data transmitted by the CP EDT) is transmitted according to the EDT, the resumption procedure may not be performed during the process 3). Meanwhile, while resuming the context of the CIoT device, the base station may receive an RRC message (eg, an RRC connection request message or a new RRC message) for transmitting CP data (or data transmitted by the CP EDT) from the CIoT device. have. Thereafter, the base station can clear the context of the CIoT device that is being resumed. The base station extracts CP data (or data transmitted by CP EDT) included in the NAS message in the RRC message in the RRC idle state or the EMM-idle state. The base station encapsulates the extracted CP data (or data transmitted by CP EDT) in a UL NAS transport message and then transmits the encapsulated CP data to an MME.

CP data (or data transmitted by CP EDT) described above in step 4) may be applied regardless of whether UP optimization is used. In other words, the above description may also apply to a case in which the CIoT device transmits CP data (or data transmitted by CP EDT) in the uplink in the EMM idle state.

As described above, the CIoT device in the EMM idle state according to the pause indication is applied by the EDT only when the initial NAS message is not transmitted to the network node (that is, the MME). Data). In other words, EDT should not be performed when the initial NAS message should be delivered to the network node.

In the following i), ii) and iii), upon successful resumption procedure, the initial NAS message is not sent to the network node.

The CIoT device switches to EMM connected mode when receiving an indication from the lower layer that the RRC connection has been resumed when in the EMM idle state according to the pause indication. The NAS message is as follows.

i) service request message

ii) the CPSR message, the CIoT device does not include the ESM container, NAS message container, or EPS bearer context status IE.

iii) the extended service request message and the service type IE indicates "packet services via S1", and the CIoT device does not include EPS bearer context state IE,

The message is not sent. Otherwise, the CIoT device encrypts the message and transmits the initial NAS message when it switches to the EMM connected mode.

If the NAS message is discarded and not sent to the network node, the value of the uplink NAS COUNT corresponding to the message may be reused for the uplink NAS message to be transmitted next.

In the resumption procedure of the above process 3-A), all bearers in the bearer context of the CIoT device are conventionally resumed. However, in case of EDT, transmission using only a specific bearer is typical. Therefore, it is suggested to resume only a specific bearer. On the other hand, it has been described that the CIoT device includes the ESP bearer ID in the MSG3, so that the bearer ID is delivered to the MME. The bearer ID to be resumed may be included. For example, if a bearer for an EDT is already promised / configured between a CIoT device and a network node, the base station can transmit the bearer for inclusion in an S1-AP message even if the EPS bearer ID is not received from the CIoT device. have

III. Third Initiation: Determination of Success for UL Data Transmission

In order to solve the second problem, the third disclosure proposes a method of allowing a CIoT device to know whether a UL data transmission is successful. Option 1) described later relates to a method of additionally using a timer in the resume procedure, and option 2) relates to a method of improving the resume procedure.

Option 1) How to use timer

The AS layer of the CIoT device transmits MSG3 (ie, RRC connection resumption request message) to the base station. If the base station accepts the resumption, the MSG4 (ie, RRC connection resumption message) is transmitted to the AS layer of the CIoT device. In this case, the message may include an in-activity timer. The AS layer of the CIoT device receiving the MSG4 starts a timer Txx. At this time, when the in-activity timer is included in the MSG4, the timer Txx is set by the in-activity timer. If there is no in-activity timer in MSG4, the CIoT device sets the timer Txx according to the set value. While the timer Txx is running, when receiving signaling (eg, an RRC connection release message) or data from a base station, the CIoT device stops the timer Txx. When the timer Txx expires, the CIoT device releases the RRC connection internally and transitions to the EMM idle state. In this case, CIoT devices that were using eDRX continue to use eDRX.

Option 2) Modify the conventional resume procedure. This will be described with reference to the drawings.

14A and 14B are exemplary flowcharts illustrating a procedure of transmitting data according to an EDT.

In the following description, only contents that are different from the general resumption procedure will be described.

As described in the first disclosure, the UP data is applied by applying the EDT only when the CIoT device is in the EMM idle state according to the suspend indication and when the initial NAS message is not sent to the network node (ie, MME). (Or data transmitted by the UP EDT) may be transmitted. In other words, EDT should not be performed when an initial NAS message has to be delivered to a network node. If the CIoT device is in the EMM idle state according to the suspend indication, and if the CP data (or data transmitted by the CP EDT) is transmitted by applying the EDT, the NAS layer of the CIoT device may enter the EMM idle state. Thereafter, CP data (or data transmitted by CP EDT) is transmitted. That is, the contents described below in the third disclosure assume a situation in which the CIoT device transmits UP data (or data transmitted by the UP EDT) when the CIoT device is in the EMM idle state according to the pause indication.

1) The AS layer of the CIoT device receives an indication from a higher layer. For details, the contents of Processes 1 and 2 of the first disclosure shall apply mutatis mutandis. When the AS layer of the CIoT device receives the indication, the AS layer performs a resume procedure.

In this case, the NAS layer may operate in one of two ways.

1-i) The NAS layer of the CIoT device does not buffer (or pending) the initial NAS message, but instead passes it directly to the AS layer. In this case, an RRC establishment cause, an indication that the call type and the EDT are possible may be delivered together. That is, it transmits to the AS layer of the CIoT device (that is, the RRC layer of the CIoT device). The AS layer of the CIoT device (that is, the RRC layer of the CIoT device) transmits radio resources for the EDT to the MSG3 by transmitting the size of the UL data to be transmitted through the MSG3 (ie, data volume information) or the EDT indication in the MSG1. Request allocation. When the AS layer of the CIoT device (that is, the RRC layer of the CIoT device) receives the MSG2, the scheduling information for the UL data transmission according to the EDT may be confirmed through the MSG2. That is, it may be checked whether radio resources for UL data transmission according to the EDT have been allocated. When the scheduling of UL data transmission according to the EDT is confirmed through the MSG2, UL data (initial NAS message including UL data in case of CP data (or data transmitted by CP EDT)) is included in the MSG3 and transmitted. However, if it is confirmed that scheduling information for UL transmission according to the EDT is not included in the MSG2, the AS layer of the CIoT device (that is, the RRC layer of the CIoT device) may perform a general resumption procedure. That is, the AS layer performs a general resume procedure by sending a resume request message to the base station.

1-ii) The NAS layer of the CIoT device buffers (or pending) the initial NAS message, an initial NAS containing the cause of the RRC establishment, an indication that the call type and EDT are possible, and the UL data that is buffered (or pending). The size information (ie, data volume information) of the message is transmitted to the AS layer (ie, RRC layer of the CIoT device) of the CIoT device, and the following procedure is performed. The AS layer of the CIoT device (that is, the RRC layer of the CIoT device) transmits radio resources for the MSG3 according to the EDT by transmitting the size of UL data (ie, data volume information) or EDT indication to the MSG1 to the MSG3. Request allocation. The AS layer (ie, RRC layer) of the CIoT device may receive MSG2 and check scheduling information for UL data transmission according to the EDT through the MSG2. That is, whether radio resources for UL data transmission according to the EDT are allocated. You can check whether or not. When the scheduling information for UL data transmission according to the EDT is confirmed through the MSG2, the AS layer of the CIoT device transmits an indication that the EDT is possible or resumed successfully to a higher layer (ie, a NAS layer). The upper layer (ie, NAS layer) that receives this performs a conventional operation when it receives an indication that resumption is successful. Thereafter, the AS layer of the CIoT device transmits UL data (initial NAS message including UL data in case of CP data (or data transmitted by CP EDT)) in MSG3. However, when the UL data transmission according to the EDT is not included in the MSG2, the AS layer (ie, the RRC layer) of the CIoT device may perform a general resumption procedure. That is, the AS layer performs a general resume procedure by sending a resume request message to the base station.

2) The AS layer of the CIoT device transmits MSG1 to the base station, and the base station transmits MSG2 to the AS layer of the CIoT device.

3) When the AS layer of the CIoT device receives the MSG2, the AS layer of the CIoT device transmits the MSG3 (eg, RRC connection resumption request message) to the base station and waits for a response from the base station.

4) When the base station receives the MSG3 (ie, RRC connection resume request message) from the AS layer of the CIoT device, the MME does not send the MSG4 (RRC connection resume message or RRC connection setup message or RRC connection rejection message) to the CIoT device, Send an S1-AP message. In this case, the details of the first disclosure will apply mutatis mutandis to the type of S1-AP message, the included information (IE), and a related procedure.

In this case, when the CIoT device transmits UP data (or data transmitted by the UP EDT), the S1-AP message transmitted by the base station to the MME may include a UE context resumption request message.

However, when the CIoT device transmits CP data (or data transmitted by the CP EDT), the S1-AP message transmitted by the base station to the MME may be a message as described in the first disclosure.

5) Upon receipt of this, the MME decides to transmit and / or resume the data. In accordance with the determination, the MME sends an S1-AP to a base station. In this case, the details of the first disclosure will apply mutatis mutandis to the type of S1-AP message, the included information (IE), and a related procedure.

When the CIoT device transmits UP data (or data transmitted by the UP EDT), the S1-AP message transmitted by the MME to the base station may be a UE context resume response or a UE context resume failure message. For details on which of the two messages is transmitted, the contents described in the first disclosure shall apply mutatis mutandis.

Meanwhile, when the CIoT device transmits CP data (or data transmitted by the CP EDT), the S1-AP message transmitted by the MME to the base station may be a message as described in the first disclosure.

6) The base station receiving this may transmit an RRC message to the CIoT device. In this case, details of the type of the RRC message, the included information (IE), and the related procedure shall apply mutatis mutandis to the contents of the first disclosure.

7) The CIoT device can recognize the success or failure of the UL data transmission transmitted from the received RRC message.

7-A) UL Data Transmission Successful

The AS layer of the CIoT device sends the indication 'UL data transmission succeeded' to the NAS layer. In detail, the AS layer transmits a result of resume (success, failure, fallback) and an indication of whether to suspend the NAS layer. When the AS layer of the CIoT device receives an RRC connection state, the AS layer of the CIoT device may switch to the RRC idle state after receiving the RRC connection release message. If the RRC connection release message is not received, the AS layer internally releases the RRC connection to switch to the RRC idle state. If it was originally RRC idle, it stays there. In the case of the conventional eDRX, the state transitions to the eDRX state. When the NAS layer of the CIoT device recognizes that the 'UL data transmission is successful', it discards (or pending) the NAS message and transitions to the EMM idle state. When the pause indication is received, the EMM enters an idle state according to the indication.

7-B) If the CIoT device determines that the UL data transmission has failed, it may attempt to retransmit. The AS layer of the CIoT device transmits an indication of the transmission failure to the NAS layer of the CIoT device. When the NAS layer of the CIoT device receives this, it operates as follows. In case of CP data (or data transmitted by CP EDT), retransmission is attempted through MSG5, and in case of UP data (or data transmitted by UP EDT), DRB (Data Radio Bearer) is established according to the service request procedure. Try to resend afterwards.

For reference, the transmission timing of MSG4 was not described in the first disclosure. The first disclosure may be applied in conjunction with the conventional resume procedure or may be applied with the second disclosure.

IV. Fourth Initiation: Method for Using PSM

The fourth disclosure proposes a method for using eDRX or PSM to solve the third problem.

Hereinafter, a method for using a PSM will be described, but the following description can be applied to a method for using an eDRX.

According to a general operation, when outgoing (MO) data is generated in a CIoT device in PSM mode, a TAU request message should be transmitted first. In this case, when the TAU request message is transmitted, the two technologies have difficulty coexisting because there is no meaning of performing the EDT operation.

CIoT devices that perform EDT in PSM mode should continue to use the PSM without performing the TAU procedure.

PSM-related operating parameters are reused as they are recently used.

When the CIoT device enters PSM mode again,

It may be a point in time after the CIoT device described in the first initiation and the second initiation receives the RRC message (MSG4) from the base station after transmitting the UL data to the MSG3.

Or, it is the time when the timer expires in option 1) of the second start. The network node (eg, MME) may also recognize when the CIoT device re-enters the PSM by the operation.

Since the RRC message transmission of the base station is triggered by the MME, the MME can recognize it. If the timer expires, the base station can notify the MME.

-Otherwise

a) When the CIoT device using the PSM transmits the MSG3, the CIoT device transmits an indication requesting to continue using the PSM. b) The base station receiving this is transmitted to the MME including the S1-AP message. c) when the MME receives the S1-AP message from the base station, and if the CIoT device continues to use the PSM, the MME includes an indication to continue using the PSM in the response message S1-AP, and the base station transmits the indication. The application with the RRC message to the CIoT device. If the MME refuses to continue using the PSM, the indication is sent to the CIoT device.

Without steps a and b above, the MME can start the procedure. In this case, the MME recognizes that the CIoT device was in use of the PSM mode, and if the CIoT device recognizes that the PSM mode is being used, it performs the above operation.

All of the above-described processes may not be implemented, and may be implemented by only some processes.

The foregoing may also be applied to 5G systems. The following shows a relationship in which the technical term used in the conventional EPC (LTE) is mapped with the technical term used in the 5G system. The foregoing may be applied to 5G systems according to the mapping shown in the table below. In 5G, the MME-EMM is mapped to AMF, the MME-ESM is SMF, the interface between MME-EMM and MME-AMF is N11, and the interface between MME-EMM and base station is mapped to N2.

EMM Connection Mode (RRC Connection Mode)	CM connection mode (RRC connection mode / RRC active mode
eNodeB (eNB)	gNB
MME	AMF (or SMF)
MME-EMM (Layer)	AMF (Layer)
MME-ESM (layered), S-GW control plane function, P-GW control plane function	SMF (Layer)
User Plane Function of S-GW User Plane Function of P-GW	UPF (Layer)
S1-AP (Interface / Message)	N2 (interface / message)
NAS (Signaling Connection / Interface)	N1 (connection / interface)

V. Fifth Initiation The fifth initiation proposes a scheme for resuming only bearers corresponding to UP data (or data transmitted by the UP EDT) among the contents of the second initiation. That is, in general, the base station resumes all bearers, but the fifth disclosure proposes to only resume bearers corresponding to the specific UP data (or data transmitted by the UP EDT) included in MSG3.

In existing UP EPS CIoT optimization, the network attempts to resume all bearers of the UE. When the base station receives the RRC connection resume request message, the base station transmits an S1-AP based UE context resume request message including a list of all bearers successfully resumed. Upon receiving the S1-AP based UE context resumption request message, the MME resumes all bearers in the message and transmits a Modify Bearer Request message. The S-GW resumes all bearers contained in the Modify Bearer Request message. Then, an S1-U bearer is established corresponding to the bearer successfully resumed.

15 shows an example of EDT application for UP CIoT optimization.

Referring to FIG. 15, when the base station receives an RRC connection resumption request message including the UP EDT data, the base station may find an ID of a bearer corresponding to the UP EDT data.

Therefore, the base station does not have to send a request message to the MME for resuming other bearers other than the bearer associated with the UP EDT data.

That is, the UE context resumption request message transmitted by the base station in step 4 of FIG. 15 is used not only to inform the MME that the CIoT device has resumed the RRC connection, but also informs the MME of the UE context, UE-related logical S1 connection, and associated bearer. Can be used to request to resume the context.

That is, when the base station does not accept all suspended E-RAB, the base station may include the 'E-RAB Failed to Resume' list in the UE context resumption request message. The 'E-RAB Failed to Resume' list may include information on the E-RAB that does not need to be resumed.

On the other hand, when the base station requests to resume the bearer other than the bearer corresponding to the received UP EDT data, unnecessary S1-U bearers may be established that will not be used.

Assuming that an ID of a bearer corresponding to UP EDT data transmitted through MSG3 is 1, it will be described below.

Option 1: If the base station requests resumption of all bearers as before,

The base station sends an S1-AP based UE context resume request message including a list of all bearers. If the MME fails to resume a bearer with a bearer ID of 1 but succeeds in resuming another bearer, the MME transmits information on the resumed bearer to the base station through an S1-AP based UE context response message and modifies the bearer. Send the request message. Then, since the BS fails to resume the bearer having a bearer ID of 1, the BS transmits an RRC connection rejection message to the CIoT device and transmits an S1 UE context release request message to the MME. The MME performs an S1 release procedure.

Option 2: If the base station corresponds to UP EDT data transmitted over MSG3 and requests to resume the bearer whose bearer ID is 1, the base station selects the bearer's ID = 1 in the bearer list in the S1-AP context resume request message. Include and send. If the MME fails to resume the bearer with the ID = 1 of the bearer, the MME sends a S1-AP based UE context resume failure message to the base station. Then, the base station transmits an RRC connection rejection message to the CIoT device.

As described above, compared to option 2, option 1 requires additional signaling.

Therefore, when the base station receives the MSG3 including the UP EDT data, it is effective that the base station only requests the MME to resume the bearer corresponding to the UP EDT data.

On the other hand, when the CIoT device is in the paused state, when the CIoT device transmits the outgoing (MO) CP EDT data through the MSG3, the CIoT device may not perform the resume procedure.

Detailed procedure of the CIoT device to implement this is as follows.

Assumptions) Condition for NAS layer of CIoT device in EMM idle state to perform EDT according to pause indication

Case 1) The following NAS message is triggered, or

Upon successful resumption, a message that the NAS layer does not forward to the lower layer (which is not actually sent) may be an initial NAS message as described above.

Case 2) When a NAS message transmitting CP data (or data transmitted by CP EDT) is triggered, the control plane service request (CPRS) message, the ESM message container in the CPRS message may include an ESM data transmission message. have.

High level concept of what is suggested:

Common: Determining whether CIDT can perform EDT

The CIoT device determines that EDT can be performed when the following conditions are satisfied.

The maximum grant size for the EDT provided in the SIB is greater than the EDT data and / or

If the condition is satisfied, the EDT request is made through the MSG1 of the random access procedure, and upon receiving the MSG2 (that is, the random access response), it is determined whether the EDT can be performed. In detail, when sufficient grant (ie, resource allocation) is obtained through MSG2 to transmit EDT data through MSG3, it may be determined that EDT data transmission is possible.

Case 1) Regardless of whether EDT can be performed or not in the above-described assumption, the conventional resume procedure can be performed. That is, the CIoT device may transmit MSG3 (ie, RRC connection resumption request message) and receive MSG4 as conventionally.

Case 2) In the above-described assumption, if it is determined that the EDT can be performed, the CP EDT data transmission procedure may be performed without performing the resume procedure. However, if it is determined that the EDT cannot be performed, the CIoT device may perform a conventional resume procedure. That is, the CIoT device may transmit MSG3 (ie, RRC connection resumption request message) and receive MSG4 as conventionally.

By conventional operation, CP data (or data transmitted by CP EDT) can be transmitted over MSG5 (ie, RRC connection setup complete message).

As in the conventional resumption procedure, when the NAS layer buffers (or pending) the initial NAS message and requests resumption from the AS layer (i.e., the RRC layer), and in hypothesis 2, the NAS layer buffers (or The data volume information in the pending NAS message must be provided to the AS layer (ie, RRC layer). The data volume information is used as information for determining whether to perform EDT.

Modification of Case 2) In the above-described assumption, the resume procedure may not be performed regardless of whether EDT can be performed. In this case, the operation in the conventional UP EPS CIoT optimization should also be improved. That is, when the CIoT device is imagined to be EMM idle according to the pause indication, when the transmission of a Control Plane Service Request (CPSR) message including CP data (or data transmitted by CP EDT) is triggered (or CP data). The resume procedure may not be performed even when a CPSR message including (or data transmitted by the CP EDT) is transmitted through MSG5). The way to implement this is as follows. When the NAS layer of the CIoT device is in the EMM idle state according to the suspend indication, when the transmission of the CPSR message including the CP data (or data transmitted by the CP EDT) is triggered, after switching to the EMM idle state A CPSR message including corresponding CP data (or data transmitted by CP EDT) is transmitted.

In the case of the above modifications, the solving procedure (UP EPS CIoT optimization) should be improved.

V-1. Implementation options

On the other hand, implementation options for implementing the proposal will be described below.

The NAS layer of the CIoT device may finally determine whether to resume.

V-1-1. Option 1

V-1-1-A. Option 1-A

The NAS layer of the CIoT device may operate according to the information on whether the AS layer of the CIoT device may perform EDT. Specifically, it is as follows.

Process 1: The following conventional operation is performed on the NAS layer of the CIoT device.

When the procedure of using the Initial NAS message is triggered in the EMM idle state according to the pause indication, the NAS layer of the CIoT device requests the AS layer to resume the RRC connection. In the request for the AS layer, the NAS layer may provide an RRC establishment cause and call type to the AS layer. For EDT, Release Indication Release Assistance Indication (RAI) and / or EDT indication is provided to the AS layer (ie, RRC layer) along with the RRC establishment cause and call type.

Step 2: The AS layer of the CIoT device may determine whether to perform EDT. See the high level concept above.

Step 2-1: When it is determined that EDT can be performed, the AS layer transmits an indication that EDT can be performed to the NAS layer of the CIoT device, and proceeds to step 3-1 below.

Step 2-2: If it is determined that the EDT cannot be performed, the resume procedure is conventionally performed.

Course 3: For Course 2-1,

Case A) If a message that the NAS layer of the CIoT device is buffering (or pending) contains a NAS message containing CP data (or data transmitted by CP EDT) (i.e. an ESM data transport mesh in the ESM message container). CPSR message), and together with the NAS message, further transmits the following information to the AS layer of the CIoT device and switches to the EMM-IDLE. And proceed to step 4. The NAS layer delivers an indication to the AS layer indicating that the NAS message is a NAS message for transmitting CP data (or data transmitted by CP EDT). The indication may be CP EDT or CP data (or data transmitted by CP EDT) transmission. The NAS layer may send an indication to the AS layer not to perform a resume or to switch to an idle state.

Case B) If a message that the NAS layer of the CIoT device is buffering (or pending) contains a NAS message containing CP data (or data transmitted by the CP EDT) (i.e. an ESM data transport mesh in the ESM message container). CPSR message), an acknowledgment (ACK) / response indication is transmitted to the AS layer of the CIoT device.

Case 4: In case A) of process 3, the AS layer of the CIoT device sends the MSG3 of the random access procedure and resumes the procedure to send a NAS message that transmits CP data (or data transmitted by the CP EDT). Do not perform. However, in case B) of process 3, the AS layer of the CIoT device performs the resume procedure.

V-1-1-B. Option 1-B

The NAS layer of the CIoT device may inform the AS layer only when transmission of a NAS message including CP data (or data transmitted by the CP EDT) is triggered. The AS layer of the CIoT device may additionally distinguish from the NAS layer of the CIoT device according to the EDT availability information.

Process 1: The following conventional operation is performed on the NAS layer of the CIoT device.

When the procedure of using the Initial NAS message is triggered in the EMM idle state according to the pause indication, the NAS layer of the CIoT device requests the AS layer to resume the RRC connection. In the request for the AS layer, the NAS layer may provide an RRC establishment cause and call type to the AS layer. In the case of EDT, Release Assistance Indication (RAI) and / or EDT indication is provided to the AS layer (ie, RRC layer) together with the RRC establishment cause and call type.

If the message being buffered (or pending) by the NAS layer of the CIoT device is a NAS message containing CP data (or data sent by CP EDT) (ie, a CPSR message containing an ESM data transport mesh in the ESM message container). If, the NAS layer delivers an indication to the AS layer indicating that the NAS message is a NAS message for transmitting CP data (or data transmitted by CP EDT). The indication may be CP EDT or CP data (or data transmitted by CP EDT) transmission.

Step 2: The AS layer of the CIoT device may determine whether to perform EDT. See the high level concept above.

Step 2-1: When it is determined that EDT can be performed, the AS layer transmits an indication that EDT can be performed to the NAS layer of the CIoT device, and proceeds to step 3-1 below.

Step 2-2: If it is determined that the EDT cannot be performed, the resume procedure is conventionally performed.

Step 3: For Step 2-1, the CIoT device NAS layer sends the following information to the AS layer of the CIoT device along with a NAS message containing the CP data (or data transmitted by the CP EDT) that is buffering (or pending): Send additionally and switch to EMM-IDLE. The NAS layer may transmit an indication not to perform resumption or an indication to switch to an idle state to the AS layer.

Step 4: The AS layer of the CIoT device transmits the MSG3 of the random access procedure and does not perform the resume procedure to transmit a NAS message that transmits CP data (or data transmitted by the CP EDT).

V-1-1-C. Option 1-C

The NAS layer of the CIoT device does not request for resumption, and after receiving EDT success from the AS layer of the CIoT device, it is possible to determine whether to request a resumption according to the type of the NAS message being buffered (or pending). Specifically, it is as follows.

Step 1: The NAS layer of the CIoT device does not perform an operation for requesting resumption in the following conventional operation.

When a procedure of using an Initial NAS message is triggered in the EMM idle state according to the pause indication, the NAS layer of the CIoT device may provide an RRC establishment cause and call type to the AS layer.

In case of EDT, in case of EDT, Release Assistance Indication (RAI) and / or EDT indication is provided to the AS layer (ie, RRC layer) together with the RRC establishment cause and call type.

Step 2: The AS layer of the CIoT device may determine whether to perform EDT. See the high level concept above.

Step 2-1: If it is determined that EDT can be performed, the AS layer transmits an indication that EDT can be performed to the NAS layer of the CIoT device.

Step 2-2: If it is determined that the EDT cannot be performed, an indication that the EDT cannot be performed is transmitted to the NAS layer of the CIoT device.

Course 3:

For process 2-1,

Case A) The NAS layer of the CIoT device switches to EMM-IDLE if the NAS message buffering is a NAS message transmitting CP data (or data transmitted by CP EDT), and converts the NAS message to CIoT. Send to the AS layer of the device.

Case B) If the NAS message of the CIoT device is not a NAS message transmitting CP data (or data transmitted by CP EDT), the NAS layer of the CIoT device sends a request to resume the RRC connection of the CIoT device. Send to AS layer.

For process 2-2,

Case C) The NAS layer of the CIoT device sends a request to the AS layer of the CIoT device to resume the RRC connection.

Course 4:

In case A) of process 3, the AS layer of the CIoT device does not send an MSG3 (for CP EDT) and perform a resume procedure to transmit a NAS message that transmits CP data (or data transmitted by CP EDT). Do not.

In case B) and case C) of process 3, the AS layer of the CIoT device performs the resume procedure.

V-1-2. Option 2

The AS layer of the CIoT device performs the final decision on whether to resume.

Process 1. Unlike the conventional operation in the EMM idle state according to the pause indication in the NAS layer of the CIoT device, the initial NAS message does not buffer the initial NAS message as if it has been in the EMM idle state. Can be delivered directly to the AS layer of the CIoT device along with the RRC establishment cause and call type. The NAS layer transmits a request for resuming the RRC connection to the AS layer of the CIoT device.

In case of EDT, the NAS layer provides RAI and / or EDT indication to the AS layer (ie, RRC layer) together with the RRC establishment cause and the call type.

In addition, the NAS layer informs the AS layer of the CIoT device whether the NAS message is a NAS message (ie, a CPSR message) that transmits CP data (or data transmitted by CP EDT).

In the case of a NAS message transmitting CP data (or data transmitted by CP EDT), the indication may be CP EDT or CP data (or data transmitted by CP EDT) transmission.

Step 2: The AS layer of the CIoT device may determine whether to perform EDT. See the high level concept above.

Step 2-1: If it is determined that EDT can be performed,

If the NAS message received in case A) process 1) is a NAS message containing CP data (or data transmitted by CP EDT),

The AS layer of the CIoT device transmits MSG3 (for CP EDT) of a random access procedure to transmit a NAS message including CP data (or data transmitted by CP EDT). At this time, the AS layer does not perform the resumption procedure and informs the NAS layer of the CIoT device. The NAS layer of the CIoT device then transitions to the EMM idle state.

Case B) If the NAS message received in step 1) is not a NAS message transmitting CP data (or data transmitted by CP EDT), the AS layer of the CIoT device performs the resumption procedure.

Step 2-2: If it is determined that the EDT cannot be performed, the resume procedure is conventionally performed.

Comparing between options: For option 1-B, perform different actions only when a NAS message occurs that transmits CP data (or data transmitted by the CP EDT), thus giving a different NAS message than other options. It can be implemented without further improvement in the case in which it occurs.

The foregoing proposals can be used in combination with each other.

The contents described so far can be implemented in hardware. This will be described with reference to the drawings.

16 is a block diagram illustrating a configuration of a CIoT device 100 and a network device according to an embodiment of the present invention.

As illustrated in FIG. 16, the CIoT device 100 includes a processor 101, a memory 102, and a transceiver 103. The network device may be a base station 200 or an MME / SGSN 510. The network device 200 or 510 includes a processor 201 or 511, a memory 202 or 512, and a transceiver 203 or 513.

The memories 102, 202 or 512 store the method described above.

The processors 101, 201, or 511 control the memories 102, 202, or 512 and the transceivers 103, 203, or 513, respectively. Specifically, the processors 101, 201, or 511 execute the methods stored in the memories 102, 202, or 512, respectively. The processors 101, 201, or 511 transmit the aforementioned signals through the transceivers 103, 203, or 513.

In the above description of the preferred embodiments of the present invention by way of example, the scope of the present invention is not limited only to these specific embodiments, the present invention is in various forms within the scope of the spirit and claims of the present invention Can be modified, changed, or improved.

Claims (12)

1. As a base station to support Early Data Transmission (EDT),

   Receiving a first message from a mobility management entity (MME),

   The first NAS message includes downlink data; And

   Based on receiving the first NAS message, confirming that there is no additional data other than the downlink data.
2. The method of claim 1,

   The base station transmitting an initial UE (Initial User Equipment) message to the MME,

   The initial UE message comprising data of a UE according to an EDT.
3. 2. The method of claim 1, wherein the first NAS message comprises a Downlink Non-Access-Stratum Transport message.
4. The method of claim 1,

   And sending, by the base station, a UE context resumption request message to the MME.
5. A wireless device including an RRC (Radio Resource Control) layer and a higher layer transmits UL (Uplink) data according to Early Data Transmission (EDT).

   Obtaining Release Assistance Indication (RAI) from the higher layer;

   Determining whether EDT is applicable based on the RAI;

   And if it is determined that the EDT is applicable, transmitting an RRC request message including the UL data.
6. The method of claim 5, wherein in the acquiring step

   The cause of the RRC establishment and the call type (call type) is characterized in that further obtained.
7. 6. The method of claim 5, wherein the RRC request message including the UL data is transmitted through a third message of a random access procedure.
8. 6. The method of claim 5, wherein the RRC request message includes one or more of an EPS bearer ID and a Logical Channel (LC) ID.
9. The method of claim 5, wherein the RAI indicates that subsequent UL data is not expected or that only one DL (Downlink) data for the UL data is expected.
10. 6. The method of claim 5, wherein the RRC request message includes an RRC connection resumption request message.
11. The method of claim 5, wherein the RRC connection resumption procedure is not performed when the UL data is transmitted through a control plane (CP).
12. 12. The method of claim 11, wherein when the UL data is transmitted through a control plane (CP), the RRC request message is a different message from the RRC connection resume request message.

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