KR20200036705A - Method to manage connectivity for low power consumption mode iot device - Google Patents

Abstract

The present disclosure relates to a communication technique for fusing a 5G communication system with an Internet of things (IoT) technology to support a higher data transmission rate than that of a 4G system, and a system thereof. The present disclosure can be applied to an intelligent service (for example, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety related services, etc.) based on a 5G communication technology and an IoT-related technology. Disclosed in the present invention is a method of providing a cellular IoT service to a terminal operating in a low power mode in a next generation mobile communication system. According to the present invention, a control signal processing method in a wireless communication system comprises the steps of: receiving a first control signal transmitted from a base station; processing the first control signal received; and transmitting a second control signal generated based on the processing to the base station.

Description

Method for managing connectivity of IoT terminals using low power mode {METHOD TO MANAGE CONNECTIVITY FOR LOW POWER CONSUMPTION MODE IOT DEVICE}

The present invention relates to a method for providing a cellular IoT service to a terminal operating in a low power mode in a next generation mobile communication system.

Efforts have been made to develop an improved 5G communication system or a pre-5G communication system to meet the increasing demand for wireless data traffic after commercialization of the 4G communication system. For this reason, the 5G communication system or the pre-5G communication system is called a 4G network (Beyond 4G Network) communication system or an LTE system (Post LTE) or later system. To achieve high data rates, 5G communication systems are being considered for implementation in the ultra-high frequency (mmWave) band (eg, 60 gigahertz (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, in 5G communication systems, beamforming, massive array multiple input / output (massive MIMO), full dimensional multiple input / output (FD-MIMO) ), Array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, in order to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network ), Device to Device communication (D2D), wireless backhaul, mobile network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation ) And other technologies are being developed. In addition, in 5G systems, advanced coding modulation (Advanced Coding Modulation (ACM)), hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access technologies, FBMC (Filter Bank Multi Carrier), and NOMA (non orthogonal multiple access), and SCMA (sparse code multiple access) are being developed.

Meanwhile, the Internet is evolving from a human-centered connection network where humans generate and consume information to IoT (Internet of Things) networks that exchange information between distributed components such as objects. Internet of Everything (IoE) technology, in which big data processing technology, etc. through connection to a cloud server, is combined with IoT technology is also emerging. In order to implement IoT, technical elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, a sensor network for connection between objects, a machine to machine (Machine to Machine) , M2M), and MTC (Machine Type Communication). In an IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects to create new values in human life may be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliance, high-tech medical service through convergence and complex between existing IT (information technology) technology and various industries. It can be applied to.

Accordingly, various attempts have been made to apply a 5G communication system to an IoT network. For example, 5G communication technology such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication) is implemented by techniques such as beamforming, MIMO, and array antenna. It is. It may be said that the application of cloud radio access network (cloud RAN) as the big data processing technology described above is an example of 5G technology and IoT technology convergence.

One object of the present invention is a method for updating a PDU session connection without a transition to an idle state (IDLE) by the base station notifying the base station when the UPF service area exists for the PDU session used by the terminal, and the base station Is to suggest.

In addition, an object of the present invention is to propose a method for delivering NAS signaling generated in the Core Network to a terminal when the terminal is using eDRX in RRC-Inactive.

The present invention for solving the above problems is a control signal processing method in a wireless communication system, comprising: receiving a first control signal transmitted from a base station; Processing the received first control signal; And transmitting a second control signal generated based on the processing to the base station.

Due to the present invention, for a terminal using a function for low power, the SMF can determine whether it is outside the service area of the UPF and always provide the optimal UPF to the terminal. Conventional terminals attempt to transmit data in a low power mode in a state far away from the UPF service area, which results in data transmission failure, but according to the present invention, data is continuously reliable while using a low power mode data transmission function of the terminal. It has the effect of being delivered.

 In addition, due to the present invention, for a terminal using a low-power function, the Core Network can transmit NAS signaling to be sent to the terminal according to the eDRX cycle, which is a low-power function of the terminal. Due to this, the Core Network has an effect of not having to perform unnecessary NAS connection recovery to secure the reachability of the terminal. That is, it is possible to reduce unnecessary terminal management processing of the core network and paging procedure for finding the terminal. This has the effect of preventing unnecessary waste of radio resources.

1 is a diagram for explaining a method of delivering a UPF service area to a base station when establishing a PDU Session.
FIG. 2 is a diagram illustrating a method of applying a UPF service area when a UE uses EDT or RAI for a PDU session in SSC mode 1.
3 is a diagram for explaining a method of applying a UPF service area when a UE uses EDT or RAI for a PDU session in SSC mode 2 or 3.
4 is a diagram for explaining a method of applying a UPF service area when a UE uses EDT or RAI based on Location Reporting.
5 is a diagram for explaining a method of sending a NAS signaling by transmitting a NAS retransmission timer to a base station.
6 is a diagram for explaining a method of processing a NAS signaling to a terminal using RRC-Inactive with eDRX as a failure.
FIG. 7 is a diagram for explaining a method of notifying the state of a terminal using RRC-Inactive with eDRX to the Core Network and considering the NAS signaling.
8 is a diagram for explaining a method of applying a UPF service area when a UE uses EDT or RAI for a PDU session according to another embodiment.
9 is a diagram showing the structure of a terminal according to an embodiment of the present invention.
10 is a diagram showing the structure of a base station according to an embodiment of the present invention.
11 is a view showing the structure of an AMF according to an embodiment of the present invention.
12 is a view showing the structure of an SMF according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with the accompanying drawings. In addition, in the description of the present invention, when it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

In describing the embodiments of the present invention in detail, 3GPP defines a 5G network standard for a wireless access network, a core network, a New RAN (NR) and a packet core (5G system, or 5G Core Network, or NG Core: Next Generation Core). Although it will be the main object, the main subject matter of the present invention can be applied to other communication systems having similar technical backgrounds with a slight modification within a range not departing greatly from the scope of the present invention, which is skilled in the technical field of the present invention. It will be possible by the judgment of those with technical knowledge.

For convenience of description below, some terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) standard may be used. However, the present invention is not limited by the terms and names, and may be applied to systems conforming to other standards.

The present invention seeks to solve the following problems.

First, in order to minimize power consumption, an CIoT terminal has been developed to reduce the number of RRC messages. Therefore, the terminal sends data including the RRC connection request message, or, in the RRC connection request message, whether it transmits only one data uplink and transitions to the idle state, or receives one downlink for one uplink and pauses (IDLE ). Alternatively, the base station can determine whether the terminal sees the traffic profile of the terminal, and whether the terminal usually sends and receives only one uplink, or receives one downlink for one uplink and transitions to an idle state.

When the base station determines that the terminal transmits uplink data and immediately transitions to the idle state, the base network may not only notify the core network that the terminal has transitioned to the connected state, but only send data and immediately transition the terminal to the idle state. The problem that may occur at this time is that the core network cannot know the current location of the terminal due to not informing the core network of the connected state of the terminal, and thus the service area of the UPF that provides the corresponding PDU session for the PDU session used by the terminal. It is not possible to determine whether the terminal is out. The UPF Service area indicates a range of regions in which the corresponding UPF can provide data transmission service, and base stations in the region can connect to the UPF, but base stations outside the region may not be able to connect to the UPF.

Or, if the base station determines that the UE sends one Uplink data and there will be no more data transmission / reception, the base network may send the data only and release the UE without notifying the Core network that the UE has transitioned to the Connected state. At this time, the base station performs the AMF and the Access Network Release procedure to inform the latest location of the terminal, and can inform that the terminal has been released. The problems caused by the operation of the base station sending the uplink data sent by the terminal to the UPF and releasing the terminal immediately are as follows. The base station cannot determine whether the current location of the terminal is outside the service area of the UPF providing the corresponding PDU session. The UPF Service area indicates a range of regions in which the corresponding UPF can provide data transmission service, and base stations in the region can connect to the UPF, but base stations outside the region may not be able to connect to the UPF. Therefore, if the location where the terminal is currently awake is outside the service area of the UPF that provides the PDU Session used by the current terminal, one Uplink data sent by the terminal may not be transmitted.

SMF performs the operation of allocating a new UPF to the terminal when the terminal leaves the service area of the UPF, or maintaining the connection to the existing UPF by adding an Intermediate UPF (I-UPF) to the connection between the existing UPF and the base station. Should be.

In order to solve this, the present invention notifies the base station when the UPF service area exists for the PDU session used by the terminal, and the base station updates the PDU session connection without transitioning the terminal to the idle state immediately based on this. Suggest how to do it.

In another method, the present invention proposes a method for the base station to determine whether the current location of the terminal belongs to the UPF Service Area of the PDU Session used by the terminal, and accordingly informs the location of the terminal to the AMF or SMF to make a new UPF We propose a method to establish a data session connection with.

 Second, the CIoT terminal can use a function called eDRX to minimize power consumption. (eDRX: extended Discontinuous Reception) The base station can manage the terminal with a power consumption similar to the idle state by transitioning the terminal to the RRC-Inactive state, where eDRX can be applied. When eDRX is applied, the terminal wakes up with a long interval to monitor the paging channel, and the network can communicate with the terminal only by signaling to the terminal according to this interval.

It can be determined that the terminal is in the RRC-Inactive state, in terms of the Core Network, the terminal is in the CM-Connected state. Therefore, if the Core Network does not know whether the terminal is applying eDRX, it can think of the terminal as being connected and send NAS signaling to the terminal immediately. However, since the terminal is in a low power state for a long interval by applying eDRX, the base station cannot directly transmit NAS signaling to the terminal.

Since the NAS message sent by the Core Network is a message sent according to the NAS procedure, there is a time waiting for a response from the terminal. That is, if the terminal does not respond, the NAS attempts to send signaling again, and if the terminal does not respond continuously, it processes an error and performs a NAS recovery procedure to recover the connection of the terminal. This causes unnecessary error procedures, complicates terminal management processing of the core network, and sometimes attempts to send paging to various regions to find the terminal, which incurs a large cost in radio resources.

To solve this, the present invention proposes a method for delivering NAS signaling generated in the Core Network to a terminal when the terminal is using eDRX in RRC-Inactive.

Description of entities appearing in the present invention according to FIG. 1 is as follows.

The UE is connected to a radio access network (RAN) to access a device performing a mobility management function of a 5G core network device. In the present invention, this will be referred to as AMF (Access and Mobility management Function). This may refer to a function or device in charge of both RAN access and mobility management of the terminal. SMF is the name of the network function that performs the session management function. The AMF is connected to the SMF, and the AMF routes Session related messages to the terminal through the Session Management Function (SMF). The SMF connects with a user plane function (UPF) to allocate a user plane resource to be provided to the terminal, and establishes a tunnel for transmitting data between the base station and the UPF.

UPF may have a fixed UPF Service area. This area refers to an area where it is not necessary to establish a connection between a base station and an existing UPF by adding a new UPF, or to allocate a new UPF, that is, to maintain an N3 connection with a base station for a PDU session provided by the UPF. . It is also known by the SMF. Therefore, when allocating the UPF, it is possible to allocate the UPF having the most suitable UPF service area for the current location of the terminal. The UPF service area may consist of a list of base station IDs, a Tracking Area list, or a Cell list.

When the location of the terminal changes, the SMF performs an operation such as inserting an Intermediate UPF (I-UPF) in the middle to maintain a connection between the corresponding UPF and the base station, or allocating a new UPF to establish a new connection with the base station. This may vary depending on the SSC mode (Service Session Continuity). SSC mode 1 is a mode in which the UPF serving as a PDU session anchor does not change. Since the UPF cannot be changed, an I-UPF can be added in the middle to maintain connection with the base station. SSC mode 2 and SSC mode 3 are modes in which the UPF serving as the PDU Session Anchor can be changed. Since the UPF serving as the PDU Session Anchor is changed, the existing PDU session is released, and a new PDU session is established with the new UPF. Through the operation, the connection between the base station and the UPF can be maintained. In SSC mode 2, the PDU session is released and a new PDU session is established. In SSC mode 3, before releasing the PDU session, a new PDU session is established first, and then the old PDU session is released.

PCF stands for Policy & Charging Function, and controls policy and charging related information for a session used by a terminal. NRF is an abbreviation of Network Repository Function, and functions to store information on NFs installed in a mobile operator network and inform information about it. The NRF can be connected to all NFs, and when each NF starts to run in the operator network, it performs registration procedures with the NRF so that the NRF knows that the NF is running in the network.

UDM is the same as HSS of 4G network, and stands for User Data Management. It stores the subscription information of the terminal or the context used by the terminal in the network. UDM, PCF, SMF, AMF, and NRF are connected through a Service Based Interface, which uses a service (or API) provided by each NF to send and receive control messages from each other. Each NF defines the service they provide, which is defined in the standard as Nudm, Npcf, Nsmf, Namf, Nnrf, etc. For example, when AMF delivers a session related message to SMF, a service (or API) called Nsmf_PDUSession_CreateSMContext can be used.

As a background technology of the present invention, a function provided for a low-power CIoT terminal in a mobile communication system is as follows.

-5GS UP Optimization: Since the IoT terminal transmits / receives a small amount of data, it switches to the Connected mode from IDLE mode every time, activates the user plane connection of the PDU session, establishes DRB, and sends the necessary signaling until it is transmitted. However, it is inefficient compared to the amount of data actually sent. If the terminal can reduce signaling to and from a base station for DRB establishment, power consumption of the terminal can be reduced, and a network load for DRB establishment can be prevented.

Therefore, the base station stores the information about the DRB and PDU session that the terminal is using in the connected mode, that is, even when the terminal maintains the IDLE mode, the base station keeps the information in the access stratum context (AS context) of the terminal, and the terminal When switching from the IDLE mode to the Connected mode, the base station may perform an operation of reviving the DRB and the PDU session connection to the terminal previously used by the terminal based on the stored AS Context. This is a simple RRC procedure to the user plane because the base station can activate the DRB and the PDU session connection used by the base station in response to the RRC Connection Resume message sent by the terminal when the terminal switches from IDLE mode to Connected mode. It has the advantage of activating all paths for data transmission. That is, signaling for communication with the base station is reduced for DRB establishment, thereby reducing power consumption of the terminal.

The base station can identify the AS context based on the Resume ID that the UE sends to the RRC Connection Resume. In addition, when the base station transitions to the RRC-IDLE, the base station informs that the RRC connection is suspended, and transmits the Resume ID that the UE should use when resuming for AS context identification. The terminal uses this Resume ID when performing Resume to establish an RRC connection in the future.

The base station notifies the AMF that the terminal is awakened after the connection of the terminal is resume, and also informs the SMF that the user plane connection of the PDU session should be activated. Upon receiving this, the SMF can activate the user plane connection between the UPF and the base station. The terminal may transmit uplink data immediately after completing the resume procedure, and the UPF may transmit downlink data to the terminal after the user plane connection is activated. Although the name 5GS UP Optimization is used in the present invention, it may be another name such as a data transmission function through user plane optimization, and encompasses a method of following the operation procedure.

-EDT (Early Data Transmission): Since the IoT terminal transmits a small amount of data, establishing a user plane connection for data transmission of a small capacity is inefficient in using radio resources, and signaling for establishing a user plane connection It is also inefficient in that this necessarily occurs. Therefore, a technique for transmitting a small amount of data transmitted by a terminal by including it in a message for establishing an RRC connection has been developed. This is called EDT.

When using the 5GS UP Optimization technology or RRC-Inactive technology, the terminal is supposed to send an RRC Resume request to transition to the RRC-Connected state. When using the EDT technology, the UE may send the RRC Resume Request message by including Uplink data. Upon receiving this, the base station directly transmits data to the N3 tunnel to the UPF for the corresponding bearer, and the UPF receives it and transmits it to the external network.

-RAI (Release Assistance Information): IoT terminals have monotonous data transmission / reception patterns. In the case of a sensor device, it mainly has a traffic pattern for sending sensor data. Therefore, if only one Uplink data can be sent and transitioned to the idle state immediately, there is no need to consume power to maintain a specific time for radio resource connection. In the case of another IoT device, when uplink data is sent and an acknowledgment (ACK) is received, it may have a pattern in which no other traffic occurs. In the case of such a terminal, uplink data can be transmitted, and when downlink data for it arrives, it can immediately transition to the idle state. Therefore, there is no need to consume power to maintain the radio resource connection for a specific time.

RAI is a proposed function to represent these traffic characteristics. RAI stands for Release Assistance Information or Release Assistance Indication, which means information that helps a base station release a terminal. If the RAI indicates that the terminal has only one characteristic of sending the uplink, the base station can immediately release the wireless connection of the terminal after transmitting the uplink data of the terminal to the UPF. If the RAI indicates that the terminal has one uplink and receives one downlink in response, the base station transmits the uplink data of the terminal, and when downlink data for the terminal arrives later, traffic transmission / reception for this terminal It can be determined that it is over and the wireless connection of the terminal can be released immediately. If the UE informs the RAI that it will transmit and receive multiple packets, the base station can maintain a predetermined time without immediately releasing the radio connection to the UE to ensure sufficient packet transmission and reception.

RAI can be used with EDT. That is, the UE sends data including the RRC Resume request message together, and may indicate that it is a traffic pattern in which only one uplink is generated through RAI. Upon receiving this, the base station transmits the data contained in the RRC Resume request of the UE to the UPF, and sends an RRC Release or RRC Suspend in response to the RRC Resume request of the UE to immediately transition the UE to the RRC-IDLE state or RRC-inactive state. I can do it.

-Traffic profile: This is a profile indicating what type of traffic pattern the terminal mainly has, and there is no difference in RAI and its configuration. Unlike the RAI directly indicated by the terminal, the Traffic Profile is a value analyzed by the mobile communication network or a value provided by the 3rd party application server connected to the IoT terminal to identify the traffic characteristics of the terminal and provide it to the mobile communication network.

Traffic Profile is transmitted to the base station through the Core network, and the base station can refer to this Traffic profile and refer to the radio resource management of the terminal. For example, when the Traffic Profile indicates that the terminal sends and ends only one uplink data, the base station can release the wireless connection of the terminal immediately after the terminal sends the uplink data with reference to this. Likewise, if the Traffic Profile sends one Uplink data and one Downlink data for it, the base station refers to this, and when the terminal sends Uplink data and Downlink data arrives for this terminal, traffic transmission and reception of the terminal You can terminate the wireless connection by determining that it is over.

-RRC-inactive with eDRX: The RRC state of the terminal is inactive, but the new connection mode, which is connected to the core network connection state of the terminal, is applied under the name of RRC-inactive in 5G. Existing terminals existed only in RRC connected or RRC idle state, but since many signaling was inevitable to enter RRC connected from RRC idle, by defining RRC inactive state as a way to optimize this, the terminal has very few signaling It is a technology that can establish RRC connection to perform data communication.

The RRC inactive state terminal is regarded as connected in the core network position, and maintains both the user plane and the control plane for the terminal in the core network to be active. When data for the terminal occurs, the corresponding data is transmitted to the base station through UPF, the base station finds the terminal through RAN paging, and the terminal performs RRC resume and transitions to the RRC connected state to transmit data.

eDRX is to extend the DRX cycle used in the existing terminal and apply it to the IoT terminal. It is a technology that prevents power consumption by discontinuous data reception, and the longer the discontinuous reception interval, the less power consumption. This was a technique applied to the terminal in the IDLE state, but in the CIoT of the 5G system, a method of applying eDRX to the terminal in the RRC-Inactive state has been proposed. That is, the terminal in the RRC-Inactive state continuously monitors the reception channel, and this cycle follows the eDRX cycle.

The eDRX value is determined through negotiation between the terminal and the AMF, and the AMF can deliver this value to the base station. The base station may apply the eDRX value when the UE is in the RRC-Inactive state based on the transmitted value. During the eDRX cycle, a terminal is idle in a low power state, that is, during a sleep cycle, the terminal cannot paging the terminal because it does not listen to a reception channel.

<First embodiment-Fig. 1>

The first embodiment follows FIG. 1.

Step 1: In order to establish a PDU session, the UE constructs a PDU Session Establishment Request, which is an SM NAS message, and sends it to the AMF. The UE may include an indicator informing the NAS message to the AMF that the UE uses 5GS UP Optimization. This indicator is used by AMF to select SMF using 5GS UP Optimization. In addition, it can be used to determine whether the SMF should send the UPF Service Area to the base station for the PDU session.

Step 2: AMF selects SMF that supports 5GS UP Optimization.

Step 3: The AMF delivers the Nsmf_PDUSession_CreateSMContext request message to the selected SMF. The AMF may include an indicator indicating that this message is a request of a PDU session using 5GS UP Optimization.

Step 4: The SMF sends a Nudm_UECM_Registration message to the UDM to perform the registration procedure. Through this procedure, the SMF registers with the UDM what the DNN uses for the PDU Session ID. As a result of this, UDM can deliver subscriber information related to Session Management to SMF.

Step 5: The SMF can send a response to Step 3 to the AMF to inform the PDU Session establishment procedure is in progress. In this response message, SMF includes SM Context related information and sends it to AMF.

Step 6: The SMF performs the procedure for establishing the SM Policy Association with the PCF. Through this procedure, PCF can deliver SM-related policies to SMF.

Step 7: The SMF performs the UPF selection procedure. At this time, if the UE requests 5GS UP Optimization, the UE selects an UPF that can support it. In addition, considering the location of the terminal, it is possible to select a UPF having a suitable service area. If the UE uses 5GS UP Optimization, the SMF may decide to deliver the selected UPF Service Area to the base station as an N2 message. UPF, which can support 5GS UP Optimization, can mean UPF that maintains the Uplink Tunnel between the base station and the UPF, but can disable the Downlink Tunnel.

Step 8: The SMF performs the selected UPF and N4 session establishment procedure. SMF delivers packet detection, enhancement, forwarding rules, etc. to UPF. Tunnel information used by UPF for data transmission may be allocated by SMF or UPF. This information is exchanged between the SMF and the UPF through the N4 session establishment procedure.

Step 9: The SMF sends a Namf_Communication_N1N2messageTransfer message to the AMF to establish a tunnel between the base station and the UPF and to send a response to the PDU Session establishment request to the terminal. This message includes an N2 SM message, which is an SM message to the base station, and an N1 message, which is an SM message to the terminal. The N2 message includes PDU Session ID, QoS Profile, QoS Flow ID, UPF tunnel information for UPF and N3 Tunnel connection of the base station, and the like. The N1 message means a PDU Session Establishment Accept message, and includes QoS Rule, SSC mode, and so on.

The SMF is a PDU session in which the corresponding PDU session uses 5GS UP Optimization, and if the service area of the UPF is determined, the N2 SM message includes the UPF service area and delivers it. The UPF Service Area may consist of a list of RAN node IDs, a list of Tracking Area IDs, or a list of Cell IDs.

Step 10: The AMF delivers the ACK for Step 9 to the SMF.

Step 11: AMF delivers the N2 PDU Session Request message to the base station. This message includes the N2 SM message received from the SMF, and the N1 SM NAS message received from the SMF.

Step 12: The base station receives the message of step 11, and performs an RRC signaling procedure for establishing a data radio bearer with the terminal according to QoS information contained in the N2 SM message. In addition, the base station delivers the received NAS message to the terminal. If the base station includes UPF Service Area information in the N2 SM message, the base station stores the UPF Service Area as an Access Stratum Context of the UE. This is used to determine whether the terminal is located in the UPF Service Area or out of the outside by looking at the location of the terminal when the terminal later intends to activate the wireless connection with the RRC Resume. The operation when the terminal is out of the UPF Service Area for the PDU session currently being used follows the embodiments of FIGS. 2 and 3.

The base station stores the tunnel information on the UPF side for establishing a tunnel connection with the UPF received from the N2 SM message. Therefore, the base station knows to which UPF the tunnel address should be sent. The base station establishes a wireless connection with the information received from the SMF and allocates tunnel information on the base station side for establishing a tunnel connection with the UPF. This tunnel information indicates to which base station the UPF should send data to the tunnel address.

Step 13: The base station sends a response to step 11. This message includes an N2 SM message, which includes a PDU session ID and tunnel information on a base station side for N3 tunnel connection with UPF. In addition, information such as established QoS flow may also be included.

Step 14: Upon receiving the message of step 13, the AMF delivers the N2 SM message contained in the message of step 13 to the SMF to the SMF.

Step 15: The SMF reports the N2 SM message received in step 14 and performs UPF and N4 Session Modification procedures. At this time, the SMF transmits N3 tunnel information of the base station side received from the base station to the UPF, and also transmits a packet forwarding rule for this. Through this step, it can be seen that the UPF and the base station have established a tunnel connection for data transmission / reception.

Step 16: The SMF sends a response to Step 14 to the AMF.

<Second embodiment-Fig. 2>

Step 1: The UE performs a random access procedure to activate a radio connection with the base station or to establish a radio connection.

Step 2: The UE sends an RRC Resume request to the base station to resume the RRC Connection. At this time, the terminal can use the EDT function to send data. That is, it can be delivered by including the uplink data payload along with the RRC Resume Request message. At this time, the UE may transmit the RAI together. For example, it may indicate that RAI transmits only one Uplink.

Step 3: After receiving the RRC Resume request of the terminal, the base station may perform a procedure of obtaining the context of the terminal. If the base station has the context of the corresponding terminal, based on the information, it is possible to obtain the tunnel address of the UPF to transmit the data sent by the terminal. If the current base station does not have the context of the terminal, the base station can identify the old base station, based on the identifier of the terminal sent by the Resume Request, and perform a procedure for obtaining the context of the terminal from the old base station. have. The base station that has acquired the context of the terminal can view the address of the UPF to transmit data to be transmitted by the terminal, and transmit the data transmitted through the EDT function to the address.

Step 4: The base station can determine the current location of the terminal by viewing the Cell ID or Tracking Area ID information contained in the RRC Resume request message sent by the terminal. The base station may determine whether the current location of the terminal is outside the UPF Service Area if the context of the terminal obtained through Step 3 contains UPF Service Area information for the PDU Session used by the terminal. If the current location of the terminal does not deviate from the UPF Service Area, steps 6 to 15 are omitted, and then the connection of the terminal can be suspended according to step 16. If the current location of the terminal is outside the UPF Service Area, the base station may determine that the connection between the base station and the UPF may be changed for the PDU session of the terminal. Therefore, the base station can decide not to Suspend the connection of the terminal.

Step 5: The base station sends data to the UPF if there is data sent by the terminal through step 2.

Step 6: The base station, according to the determination result of step 4, the terminal has transmitted data using the EDT, RAI for this RRC connection represents only one uplink transmission, if the current location of the terminal is out of the UPF Service Area , RSP Resume connection of the terminal is sent according to step 6 without Suspend the RRC connection of the terminal. Therefore, the terminal completes the RRC connection establishment and maintains the connection until the base station releases. In addition, the base station stores the data received from the terminal without transmitting it to the UPF. After establishing a new UPF and User Plane tunnel through step 13, the base station transmits the stored Uplink data to the UPF.

Step 7: The base station informs the AMF and SMF of the location of the terminal, and sends an NGAP message to the AMF to inform that the connection of the terminal is activated. This message is a message indicating that the connection of the terminal has been resumed, and for convenience, the name will be described as a connection resume request. Alternatively, it may mean an initial UE message, or a message used to activate a user plane by notifying AMF and SMF after the connection status of the terminal is changed to RRC-Connected. This message may include the current location of the terminal, an ID that identifies the terminal, or a cause of the terminal RRC connection. In addition, the message may include an ID for a PDU session outside the UPF Service Area according to the determination according to step 4 of the base station. This is to allow the AMF to route the location of the terminal to the SMF managing the PDU session. The AMF can perform step 8 with the SMF corresponding to the PDU session ID.

Step 8: The AMF may send the message of Step 8 to the SMF managing the corresponding PDU Session if the message received from Step 7 includes the PDU Session ID. If there is no PDU Session ID in the message received from step 7, the AMF can view the terminal context and send the message of step 8 to all SMFs managing the PDU session for all PDU sessions the terminal has. The message of step 8 may include PDU Session ID (s), UE location information, and the like.

Step 9: The SMF receiving the message of step 8 can view the current location of the terminal and compare it with the service area of the UPF managing the corresponding PDU Session. If the UE is out of the UPF service area, the SMF can perform a procedure for changing the UPF. This operation is different according to the SSC mode for the PDU session of the terminal. FIG. 2 deals with the case of SSC mode 1, and FIG. 3 deals with the case of SSC mode 2 and SSC mode 3. In SSC mode 1, since the UPF serving as the PDU Session Anchor (PSA) is not changed, the SMF can decide to insert the I-UPF that can maintain the connection between the PSA and the base station while leaving the PSA intact. When selecting the I-UPF, the SMF selects the I-UPF having the most suitable UPF Service Area based on the location of the current terminal.

Step 10: The SMF sends an N4 session establishment request to the selected I-UPF to establish a connection between the I-UPF and the PSA UPF. SMF provides the tunnel address of the PSA UPF and also the tunnel address of the base station. Upon receiving this, the UPF can establish a tunnel with the base station and a tunnel with the PSA UPF for the corresponding PDU Session. In response to the N4 session establishment request, the I-UPF includes its own tunnel information to the base station and its tunnel information to the PSA UPF.

Step 11: SMF performs an N4 Session Modification procedure on the PSA UPF to establish a tunnel connection between the I-UPF and the PSA UPF. Through this procedure, SMF delivers the tunnel information of I-UPF and the forwarding rule to the PSA UPF. Now the PSA UPF can pass the data it receives to the I-UPF.

Step 12: The SMF sends a response to Step 8. At this time, the SMF includes an N2 SM message, and this message includes information for establishing a data transmission tunnel connection between the I-UPF and the base station. That is, it contains the tunnel information of the I-UPF that the base station must use to send data. Also, the N2 SM message may include service area information of the newly allocated I-UPF. The UPF Service Area may consist of a list of RAN node IDs, a list of Tracking Area IDs, or a list of Cell IDs.

Step 13: The AMF delivers the N2 message received in step 12 to the base station. At this time, the response message of step 7 is used. Upon receiving this, the base station establishes a tunnel connection with the I-UPF. At this time, if there is no QoS-related information change, the base station does not need to reconfigure the radio resource connection. If the base station includes UPF Service Area information in the N2 SM message, the base station stores the UPF Service Area as an Access Stratum Context of the UE. This is used to determine whether the terminal is located in the UPF Service Area or out of the outside by looking at the location of the terminal when the terminal later intends to activate the wireless connection with the RRC Resume.

Step 14: If the N2 message received in the Connection Resume response of Step 13 does not have an N1 NAS message for the terminal, the base station may determine that the RRC connection of the terminal can be suspended. This determination is based on the RAI information of the terminal. For example, when the RAI is informed that the UE sends only one uplink, it can be determined that no further data transmission is necessary because the uplink data of the terminal is transmitted through step 5. Therefore, it can be determined that the terminal's RRC connection is released or suspended. As another example, when RAI informs the UE that it sends one uplink and receives one downlink, and if the base station sends uplink data of the terminal and then sends downlink data to the terminal, it determines that all traffic of the terminal has been transmitted and received. You can decide to disconnect or Suspend the RRC. Or, if the terminal did not send the RAI in step 2, the base station sees the Traffic Profile in the context of the terminal, and the terminal usually sends and receives only one uplink, or receives one downlink for one uplink and enters the idle state (IDLE) You can judge whether it is transitioning. Accordingly, it is possible to see how the actual traffic of the terminal has been transmitted and received, and it can be determined that the terminal's RRC connection is released or suspended.

Step 15: According to the determination of step 14, the base station may perform a connection suspension procedure of the terminal. During this procedure, the base station can perform the Access Network Release procedure with AMF. This is to inform the Core Network that the terminal has entered an idle state.

Step 16: The base station suspends the RRC connection of the terminal. Step 16 may be performed before step 15.

If there is a NAS message for the terminal in step 14, the base station does not Suspend the RRC connection of the terminal, delivers the NAS message to the terminal and proceeds with the operation accordingly.

In step 2, if the terminal does not use the EDT function, the terminal may include the RAI in the RRC Resume request message. That is, it can indicate whether an RRC connection is necessary for one Uplink transmission. In this case, the data transmission of the terminal is performed after the base station performs step 6. In addition, if the current location of the terminal does not deviate from the UPF Service Area according to step 4, the base station may skip steps 7 to 15 and perform step 16 to immediately stop the terminal. If it is determined in step 4 that the current location of the terminal is outside the UPF Service Area, the base station performs step 7.

<The third embodiment-Figure 3>

Step 1: The UE performs a random access procedure to activate a radio connection with the base station or to establish a radio connection.

Step 2: The UE sends an RRC Resume request to the base station to resume the RRC Connection. At this time, the terminal can use the EDT function to send data. That is, it can be delivered by including the uplink data payload along with the RRC Resume Request message. At this time, the UE may transmit the RAI together. For example, it may indicate that the RAI transmits only one Uplink.

Step 3: After receiving the RRC Resume request of the terminal, the base station may perform a procedure of obtaining the context of the terminal. If the base station has the context of the corresponding terminal, based on the information, it is possible to obtain the tunnel address of the UPF to transmit the data sent by the terminal. If the current base station does not have the context of the terminal, the base station can identify the old base station based on the identifier of the terminal sent by the Resume Request, and perform a procedure for obtaining the context of the terminal from the old base station. . The base station that has acquired the context of the terminal can view the address of the UPF to transmit data to be transmitted by the terminal, and transmit the data transmitted through the EDT function to the address.

Step 4: The base station can determine the current location of the terminal by viewing the Cell ID or Tracking Area ID information contained in the RRC Resume request message sent by the terminal. The base station may determine whether the current location of the terminal is outside the UPF Service Area if the context of the terminal obtained through Step 3 contains UPF Service Area information for the PDU Session used by the terminal. If the current location of the terminal does not deviate from the UPF Service Area, steps 6 to 15 are omitted, and then the connection of the terminal can be suspended according to step 16. If the current location of the terminal is outside the UPF Service Area, the base station may determine that the connection between the base station and the UPF may be changed for the PDU session of the terminal. Therefore, the base station can decide not to Suspend the connection of the terminal.

Step 5: The base station sends data to the UPF if there is data sent by the terminal through step 2.

Step 6: The base station, according to the determination result of step 4, the terminal has transmitted data using the EDT, RAI for this RRC connection represents only one uplink transmission, if the current location of the terminal is out of the UPF Service Area , RSP Resume connection of the terminal is sent according to step 6 without Suspend the RRC connection of the terminal. Therefore, the terminal completes the RRC connection establishment and maintains the connection until the base station releases. The base station does not transmit the Uplink data sent by the damnal to the UPF because the current location of the terminal is outside the UPF Server Area. The base station may transmit the uplink data sent by the terminal according to the user plane tunnel information with the UPF set after step 13.

Step 7: The base station informs the AMF and SMF of the location of the terminal, and sends an NGAP message to the AMF to inform that the connection of the terminal is activated. This message is a message informing that the connection of the terminal has been resumed, and for convenience, the name will be called Connection Resume Request. Alternatively, it may mean an initial UE message or a message for notifying AMF or SMF of the transition to the RRC-Connected state of the terminal. This message may include the current location of the terminal, an ID that identifies the terminal, or a cause of the terminal RRC connection. In addition, the message may include an ID for a PDU session outside the UPF Service Area according to the determination according to step 4 of the base station. This is to allow the AMF to route the location of the terminal to the SMF managing the PDU session. The AMF can perform step 8 with the SMF corresponding to the PDU session ID.

Step 8: The AMF may send the message of Step 8 to the SMF managing the PDU Session if the message received from Step 7 contains the PDU Session ID. If there is no PDU Session ID in the message received from step 7, the AMF can view the terminal context and send the message of step 8 to all SMFs managing the PDU session for all PDU sessions the terminal has. The message of step 8 may include PDU Session ID (s), UE location information, and the like.

Step 9: The SMF receiving the message of step 8 can view the current location of the terminal and compare it with the service area of the UPF managing the corresponding PDU Session. If the UE is out of the UPF service area, the SMF can perform a procedure for changing the UPF. This operation is different according to the SSC mode for the PDU session of the terminal. This embodiment deals with the case of SSC mode 2 and SSC mode 3. In SSC mode 2 or 3, since the UPF serving as the PDU Session Anchor (PSA) is changed, the SMF must perform the operation according to the SSC mode.

Step 10: The SMF determines the SSC mode of the corresponding PDU Session. In the case of SSC mode 2, the SMF must trigger the terminal to release the existing PDU Session and establish a new PDU Session. In case of SSC mode 3, SMF triggers a terminal to establish a new PDU Session and release the existing PDU session connection. Depending on whether SSC mode 2 or SSC mode 3, the N1 or N2 message included in step 11 may be different.

Step 11: The SMF constructs an N1 message for operation according to the SSC mode and delivers it to the AMF as a response message for step 8. At this time, the SMF configures the PDU Session Release message with the N1 SM message for the PDU Session in SSC mode 2. This message may include an identifier that PDU Session Re-establishment is required, so that the UE can perform the PDU Session establishment procedure. SMF configures PDU Session Modification message with N1 SM message for PDU Session in SSC mode 3. This message may contain an identifier that the re-establishment of the PDU Session is necessary because the existing PDU Session needs to be relocated to a different UPF. In addition, information about the 'lifetime of an existing PDU Session' may be included in how long the existing PDU Session should be maintained before release. The SMF may include information for activating the user plane tunnel between the UPF and the base station in the N2 SM message. For example, it may include tunnel information (eg, IP address or GTP tunnel address) with UPF that can transmit data.

Step 12: The AMF forwards the message received in step 11 to the base station in response to step 7.

Step 13: The base station confirms that there is an N1 SM message sent to the terminal in the message received from step 12, and transmits the N1 SM message to the terminal through RRC signaling. Upon receiving the N1 SM message of step 13, the terminal releases the corresponding PDU Session when it receives the PDU Session Release message. In addition, the PDU Session can be re-established by viewing the identifier included in the message. When the UE receives the PDU Session Modification message in step 13 as an N1 SM message, it can be determined that the PDU session establishment request should be sent by viewing the identifier included in the corresponding message. In addition, it is possible to determine when to disconnect the existing PDU Session based on the information included in the message.

If the base station receives the N2 SM message from the SMF, it can transmit the uplink data sent by the terminal through the EDT according to the tunnel information with the UPF included in the N2 SM message.

Step 14: The terminal performs a PDU Session establishment procedure according to the N1 SM message received in Step 13.

Step 15: In the case of SSC mode 3, the UE performs a PDU Session release procedure for the corresponding PDU Session before or after the “lifetime of the existing PDU Session” that is guided by the N1 SM message from the SMF passes or after the time expires.

Step 16: The base station may Suspend the RRC connection according to the Inactivity of the terminal.

<Fourth embodiment-Fig. 4>

Step 1: During the PDU Session establishment procedure, the SMF may decide to set the UE Location Reporting Event, which is an event for locating the UE, to determine whether the UE is out of the service area of the UPF. SMF can set UPF Service Area as Area of Interest. The Area of Interest can be expressed as a RAN node ID list, a Tracking Area ID list, or a Cell ID list. SMF can apply this event subscription to PDU Session using 5GS UP Optimization. That is, a location reporting event for a UPF service area can be subscribed to a terminal using 5GS UP Optimization.

Step 2: The SMF may send a Namf_EventExposure_Subscribe message to the AMF to subscribe to the location reporting event of the terminal. In this message, the SMF includes the UE ID and the Area of Interest configured in step 1.

Step 3: AMF transmits the Location Reporting Control message to the base station serving the UE according to the Event subscription received from the SMF. This message contains information about the SMF subscribed Area of Interset. In addition, an identifier (Request Reference ID) for identifying the corresponding Location Reporting Control is included. At this time, if the terminal is using 5GS UP Optimization, and the terminal is in the IDLE state, it can deliver the Location Reporting Control message to the base station that last served the terminal.

Upon receiving this, the base station stores the Location Event received from the Location Reporting Control in the context of the terminal managed by the base station. That is, the Area of Interest included in the Location Reprorting Control message is stored, and when the location of the terminal is known, it can be continuously determined whether or not it is within the Area of Interest. If the serving base station of the terminal is changed, the previous base station sends the context of the terminal to the new base station, and since the location information is included in the terminal context, the new base station continues to the location of the terminal as location reporting You can judge whether you are within or out of the established Area of Interest.

If there is no packet transmission of the terminal, time may pass without any action.

Step 4: The UE performs a random access procedure to activate a radio connection with the base station or to establish a radio connection.

Step 5: The UE sends an RRC Resume request to the base station to resume the RRC Connection. At this time, the terminal can use the EDT function to send data. That is, it can be delivered by including the uplink data payload along with the RRC Resume Request message. At this time, the UE may transmit the RAI together. For example, it may indicate that the RAI transmits only one Uplink.

Step 6: After receiving the RRC Resume request of the terminal, the base station may perform a procedure of obtaining the context of the terminal. If the base station has the context of the corresponding terminal, based on the information, it is possible to obtain the tunnel address of the UPF to transmit the data sent by the terminal. If the current base station does not have the context of the terminal, the base station can identify the old base station based on the identifier of the terminal sent by the Resume Request, and perform a procedure for obtaining the context of the terminal from the old base station. . The base station that has acquired the context of the terminal can view the address of the UPF to transmit data to be transmitted by the terminal, and transmit the data transmitted through the EDT function to the address. In addition, the base station checks the Location Reporting Control information set in the context of the terminal.

Step 7: The base station can determine the current location of the terminal by viewing the Cell ID or Tracking Area ID information contained in the RRC Resume request message sent by the terminal. The base station may determine whether the current location of the terminal is within or outside the Area of Interset according to the Location Reporting Control information, if the Context of the terminal obtained through step 6 contains location reporting control information for the terminal. If the current location of the terminal does not deviate from the Area of Interest, the base station does not send Location Reporting to the AMF. If the current location of the terminal is outside the Area of Interest according to Location Reporting Control, the base station determines to inform the AMF of the location of the terminal. Alternatively, the base station determines whether the current location of the terminal is outside the Area Of Interest after determining whether the Context of the terminal contains Location Reporting Control information for the terminal, and this information includes the Area Of Interest. You can decide not to send data to the UPF. This is because it can be expected that a user plane tunnel connection with a new UPF will occur as the terminal leaves the area of interest.

Step 8: The base station transmits data using the EDT in step 5, and if the terminal indicates that only one RAI included in the message of step 5 will occur in the uplink transmission, it determines that the traffic transmission of the terminal is over and Suspends the RRC connection of the terminal. You can. Alternatively, the base station sends data using the EDT in step 5, and when it checks the traffic profile in the context of the terminal managed by the base station, if it determines that the terminal has only one pattern of uplink transmission, the traffic transmission of the terminal is over. By determining, it is possible to Suspend the RRC connection of the terminal.

As another example, the base station sends data using the EDT in step 5, and if the terminal indicates that the RAI included in the message in step 5 will generate only one uplink transmission and one downlink for it, and one uplink transmission for the corresponding terminal. If and one downlink transmission has already occurred, it can be determined that the traffic transmission of the corresponding terminal is over, and thus the RRC connection of the terminal can be suspended. Or, if the base station sends data using the EDT in step 5, and when the traffic profile in the context of the terminal managed by the base station is checked, if the terminal has confirmed that it has a pattern that generates only one uplink transmission and one downlink for it, In addition, if one uplink transmission and one downlink transmission have already occurred for the corresponding terminal, it is determined that the traffic transmission of the terminal has been completed, and thus the RRC connection of the terminal can be suspended.

If the base station determines that the terminal is out of the Area of Interest according to the Location Report Control information, it can expect that a change or release procedure for the PDU Session of the corresponding terminal will occur. Therefore, without transmitting the traffic of the terminal, without performing the RRC connection Suspend procedure according to step 8, the terminal can be waited for a certain time. To this end, the base station can maintain the connection of the terminal by sending an RRC Resume response to the terminal. As another method, the UE may wait for a while without sending a response to the RRC Resume request. After performing the step 9, the base station may operate the timer according to step 10 to wait until the session-related message for the terminal arrives from the core network.

Step 9: The base station determines that the current location of the terminal is out of the Area of Interest according to the Location Reporting Control according to Step 7 to send a Location Report message to inform the AMF of the location of the terminal. This message may include the Request Reference ID and the current location of the terminal, or an identifier indicating whether the terminal exists in the Area of Interest.

Step 10: The base station may not change or release the RRC connection of the terminal as described in step 8 in anticipation that a change or release procedure for the PDU Session of the terminal will occur. That is, the terminal can be idle in a connected state for a certain time. To this end, the base station can maintain the connection of the terminal by sending an RRC Resume response to the terminal. As another method, it is possible to wait a certain time without sending a response to the RRC Resume request of the terminal according to step 5. In order to wait until a session-related message for a terminal arrives from the core network within a certain time, the base station may start a timer according to step 10. This timer means the time that the base station waits before Suspend the RRC Connection of the terminal. This timer value follows the internal setting.

If the NAS message or the N2 SM message for the terminal has not arrived until the timer expires, the base station Suspends the RRC connection of the terminal according to step 13.

If the N2 SM message has not arrived until the timer expires, the base station may decide to transmit the data received through the EDT from the terminal to the UPF in step 5. This is because it is possible to determine that the UPF serving the PDU Session of the terminal has not changed if the N2 SM message is not transmitted from the SMF after notifying that the terminal is out of the Area Of Interest. Therefore, the base station can transmit data received through step 5 from the terminal through the tunnel with the existing UPF.

Step 11: The base station receiving the Location Report from the base station according to step 9 notifies the SMF that subscribed to the event to the event notification. The notification may include the location information of the terminal, the ID of the terminal, the identifier of the event subscribed to by the SMF, or the presence of the terminal in the Area of Interest.

Step 12: The SMF, which knows the location of the terminal according to the notification of the location reporting event, may determine whether it is necessary to relocate the UPF or insert the I-UPF for the PDU session of the terminal. The SMF determines what operation to perform by looking at the SSC mode of the PDU Session of the corresponding terminal.

Step 14: When the PDU Session of the terminal is SSC mode 1, the SMF performs a procedure for inserting an I-UPF.

Step 15: When the PDU Session of the terminal is SSC mode 2, the SMF releases the PDU Session with the existing UPF (UPF1) and triggers a procedure for establishing a PDU Session with the new UPF (UPF2). If the RRC connection of the terminal is in the Suspend state, the AMF or the base station can paging the terminal to send a NAS message to the terminal.

Step 16: When the PDU Session of the terminal is SSC mode 3, the SMF triggers a procedure for establishing a PDU Session with a new UPF (UPF2) and a procedure for releasing a PDU Session with an existing UPF (UPF1). If the RRC connection of the terminal is in the Suspend state, the AMF or the base station can paging the terminal to send a NAS message to the terminal.

<Fifth embodiment-Fig. 5>

Step 1: The UE negotiates through the AMF and Registration procedure to use the eDRX function for low power. The terminal sends the eDRX cycle that it wants to use by including it in the registration request message. The AMF receives this and transmits the eDRX cycle available to the terminal to the terminal based on the communication pattern or expected behavior of the terminal in the Registration Accept message. In this process, the AMF can inform the base station of the eDRX cycle value used by the UE. This can be used to apply eDRX in the RRC-Inactive state of the terminal in the base station.

In addition, the AMF can transmit the NAS retransmission timer or SMS retransmission timer value for the corresponding terminal to the base station while informing the eDRX cycle value of the terminal. This means the time that the AMF waits for a response to NAS signaling sent to the corresponding terminal. After this time, the AMF determines that NAS signaling to the terminal has failed, and may attempt to recover the NAS connection. Upon receiving this value, the base station may perform the operation of step 5 when NAS signaling for the terminal arrives from the AMF. As another example, when the eMFX cycle value is greater than the NAS retransmission timer (or SMS retransmission timer) set by the AMF when the UE eDRX Cycle value is notified to the base station, the eDRX value notifying the base station of the NAS retransmission timer (or SMS retransmission timer) value. The base station may determine that the received value is eDRX clcye for the terminal and apply it. If the AMF informs the base station of the NAS retransmission timer value and the SMS retransmission timer value in step 1, steps 3 and 4 may be omitted.

Step 2: The base station can apply the RRC-Inactive to the terminal. That is, in order to reduce the power consumption of the idle state of the terminal, the terminal is transitioned to the RRC-Inactive state, and eDRX can be applied to the terminal. The base station may apply eDRX to the corresponding terminal based on the eDRX cycle value allowed for the terminal received from the AMF in step 1. Now, since the terminal is eDRX applied in the RRC-Inactive state, the terminal is in the CM-Connected state (the connection state between the terminal and the core network is Connected), but the terminal is not able to receive signaling at any time, and according to the eDRX cycle It is a state that can receive signaling.

Step 3: NAS signaling to be sent from the AMF to the terminal may occur. Since this is the NAS signaling sent to the terminal, we will call it Mobile Terminated, MT signaling for convenience. NAS signaling may be generated from SMF and transmitted to AMF. Or it may be NAS Signaling generated from AMF. When NAS signaling is generated from the SMF and transmitted to the AMF, the SMF may transmit the Retransmission timer value for the corresponding NAS procedure to the AMF. This may mean that the NAS connection must be restored by processing an error if there is no terminal response until the corresponding time passes. When NAS signaling is generated in the AMF, the AMF may set a Retransmission timer value for the corresponding NAS procedure. This may mean that if there is no terminal response until the corresponding time has passed, the NAS connection recovery procedure of the terminal must be performed by processing an error.

Step 4: The AMF may transmit the received N1 NAS message and the set Retransmission timer according to step 3 to the base station in the N2 message.

Step 5: The base station may determine the following conditions based on the received N1 NAS message and the Retransmission Timer. The NAS retransmission timer may be a value received in step 1.

First, it can be determined whether the eDRX sleep cycle of the terminal is greater than the received timer value. Alternatively, it may be determined whether the remaining time until the next paging occasion of the terminal is greater than the received timer value. Alternatively, the base station may determine whether the corresponding MT signaling can be buffered until the timer expires. The base station may determine the next operation according to step 6 by combining one or more of the above determination conditions.

Step 6: The following operation is performed according to the determination result according to step 5. If the eDRX sleep cycle of the terminal is smaller than the received timer value, the base station may transmit MT signaling to the terminal at the time the terminal wakes up according to the eDRX cycle. Alternatively, if the remaining time until the next paging occasion of the terminal is smaller than the received timer value, the base station may deliver MT signaling to the terminal at the time the terminal wakes up according to the eDRX cycle. In this case, the base station transmits MT signaling to the terminal according to step 7.

If the eDRX sleep cycle of the terminal is greater than the received timer value, the base station may determine that the retransmission timer has already expired if the terminal delivers MT signaling to the terminal at the time of waking according to the eDRX cycle. Therefore, the base station does not perform step 7 and informs the AMF that the NAS message has not been transmitted according to step 8, and notifies the reason that it is due to eDRX.

As another example, if the time remaining until the next paging occasion of the terminal is greater than the received timer value, the base station cannot transmit MT signaling to the terminal at the time the terminal wakes up according to the eDRX cycle, and after that, the retransmission timer has already expired. Can be judged. Therefore, the base station does not perform step 7 and informs the AMF that the NAS message has not been transmitted according to step 8, and notifies the reason that it is due to eDRX. Alternatively, if the base station determines that MT signaling cannot be buffered until the received timer expires due to network congestion, it notifies the AMF that the NAS message has not been transmitted according to step 8 without performing step 7, and the reason This is due to eDRX.

Step 7: According to the determination according to step 6, the base station performs RAN paging when the terminal wakes up according to the eDRX cycle, and can deliver NAS signaling to the terminal.

Step 8: According to the determination according to step 6, the base station informs the AMF that it has not delivered MT signaling to the terminal, and notifies the reason that it is due to eDRX. Upon receiving this, the AMF may send MT signaling again in an N2 message according to the eDRX cycle of the terminal, and the base station repeats the operation of step 5.

As another method, the AMF may perform terminal paging after receiving the message of step 8. This paging message may be performed according to the eDRX cycle, and accordingly, the terminal may receive and respond to MT signaling.

<Sixth embodiment-Fig. 6>

Step 1: The UE negotiates through the AMF and Registration procedure to use the eDRX function for low power. The terminal sends the eDRX cycle that it wants to use by including it in the registration request message. The AMF receives this and transmits the eDRX cycle available to the terminal to the terminal based on the communication pattern or expected behavior of the terminal in the Registration Accept message. In this process, the AMF can inform the base station of the eDRX cycle value used by the UE. This can be used to apply eDRX in the RRC-Inactive state of the terminal in the base station.

Step 2: The base station can apply the RRC-Inactive to the terminal. That is, in order to reduce the power consumption of the idle state of the terminal, the terminal is transitioned to the RRC-Inactive state, and eDRX can be applied to the terminal. The base station may apply eDRX to the corresponding terminal based on the eDRX cycle value allowed for the terminal received from the AMF in step 1. Now, since the terminal is eDRX applied in the RRC-Inactive state, the terminal is in the CM-Connected state (the connection state between the terminal and the core network is Connected), but the terminal is not able to receive signaling at any time, and according to the eDRX cycle It is a state that can receive signaling.

Step 3: NAS signaling to be sent from the AMF to the terminal may occur. Since this is the NAS signaling sent to the terminal, we will call it Mobile Terminated, MT signaling for convenience. NAS signaling may be generated from SMF and transmitted to AMF. Or it may be NAS Signaling generated from AMF.

Step 4: The AMF includes the N1 NAS message generated according to step 3 in the N2 message and delivers it to the base station.

Step 5: The base station may receive the message of Step 4, and if the terminal is applying eDRX in the RRC-Inactive state, it may determine that MT signaling cannot be directly sent to the terminal. Accordingly, the base station may decide to send a message to the AMF indicating that MT signaling has not been sent. Alternatively, if the base station is not far from the time at which the UE wakes up in the next Paging Occasion of the UE, i.e., the eDRX sleep cycle, from the time the eNB receives the message of Step 4, for example, within a few seconds, MT signaling received from Step 4 After buffering, RAN paging is performed according to the eDRX cycle, and the terminal resumes the connection and sends it.

Step 6: In step 5, if the base station decides to send a message that the MT signaling has not been sent to the AMF, it sends a Non NAS delivery message to the AMF. At this time, it may include a cause of being applied to eDRX in RRC-Inactive state.

Step 7: The AMF receiving step 6 performs CN paging, which is performed according to the eDRX cycle of the UE. When AMF performs CN paging, since the UE is applying eDRX in the RRC-Inactive state, paging can be performed according to the eDRX cycle of the UE.

Step 8: The UE resumes the RRC connection according to Step 7, and accordingly, the AMF transmits the MT signaling generated in Step 3 to the UE to perform the NAS procedure.

<Seventh embodiment-Fig. 7>

Step 1: The UE negotiates through the AMF and Registration procedure to use the eDRX function for low power. The terminal sends the eDRX cycle that it wants to use by including it in the registration request message. The AMF receives this and transmits the eDRX cycle available to the terminal to the terminal based on the communication pattern or expected behavior of the terminal in the Registration Accept message. In this process, the AMF can inform the base station of the eDRX cycle value used by the UE. This can be used to apply eDRX in the RRC-Inactive state of the terminal in the base station. The AMF may send a UE State Transition Notification Request message to the base station, so that when the base station sends the terminal in the RRC-Inactive state, eDRX is applied, the terminal may be notified of the state of the terminal and whether eDRX is applied.

Step 2: The base station can apply the RRC-Inactive to the terminal. That is, in order to reduce the power consumption of the idle state of the terminal, the terminal is transitioned to the RRC-Inactive state, and eDRX can be applied to the terminal. The base station may apply eDRX to the corresponding terminal based on the eDRX cycle value allowed for the terminal received from the AMF in step 1. Now, since the terminal is eDRX applied in the RRC-Inactive state, the terminal is in the CM-Connected state (the connection state between the terminal and the core network is Connected), but the terminal is not able to receive signaling at any time, and according to the eDRX cycle It is a state that can receive signaling.

Step 3: Upon determining that the terminal has applied eDRX in the RRC-Inactive state, the base station may inform the AMF of the current state of the terminal. The base station can inform this through the N2 Notification procedure. The base station may inform that the state of the terminal is RRC-inactive, and eDRX is applied to the terminal. Upon receiving this, the AMF knows that the eDRX has been applied in the RRC-Inactive state, and can determine that the eDRX cycle must be sent in order to send MT signaling to the terminal.

Step 4: NAS signaling to be sent from the AMF to the terminal may occur. Since this is the NAS signaling sent to the terminal, we will call it Mobile Terminated, MT signaling for convenience. NAS signaling may be generated from SMF and transmitted to AMF. Or it may be NAS Signaling generated from AMF.

Step 5: Since the AMF knows that the terminal is applying eDRX in the RRC-Inactive state through step 3, the N1 NAS message generated according to step 4 is included in the N2 message according to the eDRX cycle of the terminal and transmitted to the base station. The AMF may transmit the message of step 5 a little earlier than the time the terminal wakes up to listen to paging, which takes into account the delay required to paging the terminal.

Step 6: The base station that has received step 5 may determine that the paging occasion of the terminal returns within a short time from the time when step 5 is received. Therefore, the MT signaling is buffered until the paging occasion of the terminal, and the terminal is paging according to the paging occasion of the terminal. The UE resumes the RRC connection in response to paging, and the base station can deliver the buffered MT signaling to the UE.

Step 7: The AMF can perform the following operations without performing step 5. Since the AMF knows that the terminal is applying eDRX in the RRC-Inactive state through step 3, it can perform an operation of paging the terminal according to step 7 for the N1 NAS message generated according to step 4. The paging of the AMF terminal may be referred to as CN (Core Network) paging. When AMF performs CN paging, since the UE is applying eDRX in the RRC-Inactive state, paging can be performed according to the eDRX cycle of the UE. Therefore, the UE applying eDRX in the RRC-Inactive state can see the CN paging arriving in accordance with the eDRX cycle, and inform the RMF connection that it has been awakened to the Resume, AMF. As a result of this operation, the AMF may transmit the MT signaling generated in step 4 to the terminal.

<Eighth embodiment-Fig. 8>

Step 1: The UE performs a random access procedure to activate a radio connection with the base station or to establish a radio connection. This procedure may refer to a procedure in which the terminal resolves contention for access and is allocated resources for sending uplink signaling.

Step 2: The UE sends an RRC Resume request to the base station to resume the RRC Connection. At this time, the terminal can use the EDT function to send data. That is, it can be delivered by including the uplink data payload along with the RRC Resume Request message. At this time, the UE may transmit the RAI together. For example, it may indicate that RAI transmits only one Uplink.

Step 3: After receiving the RRC Resume request of the terminal, the base station may perform a procedure of obtaining the context of the terminal. If the base station has the context of the corresponding terminal, based on the information, it is possible to obtain the tunnel address of the UPF to transmit the data sent by the terminal. If the current base station does not have the context of the terminal, the base station can identify the old base station, based on the identifier of the terminal sent by the Resume Request, and perform a procedure for obtaining the context of the terminal from the old base station. have. The base station that has acquired the context of the terminal can view the address of the UPF to transmit data to be transmitted by the terminal, and transmit the data transmitted through the EDT function to the address.

Step 4: The base station can determine the current location of the terminal by viewing the Cell ID or Tracking Area ID information contained in the RRC Resume request message sent by the terminal. Through the step 3, the base station may determine that the connection between the current base station and the UPF may be changed when the context of the terminal is obtained from another base station (ie, the old base station). In other words, since the base station serving the terminal has been changed, data may not be transmitted through the UPF tunnel information of the UPF included in the context of the terminal. This is because the service area of the UPF is fixed, and a situation in which the base station outside the specific area and the UPF cannot be connected through a tunnel may occur. Since the base station does not know the UPF Service Area, it is not possible to know whether the UE has moved out of the UPF Service Area or not due to the mobile station moving from the old base station to itself. Therefore, the base station decides not to send the uplink data sent by the terminal to the UPF tunnel of the UPF included in the context of the terminal, resumes the connection of the terminal, informs the AMF or SMF of the current location of the terminal, and the user between the base station and the UPF. After the Plane tunnel information is newly established, an operation of transmitting the Uplink data transmitted by the UE to the UPF may be performed. If the base station is the same as the base station to which the terminal has previously accessed, that is, if the old base station and the current base station are the same base station, the base station can determine that the corresponding UPF and User Plane tunnels are valid at the current location of the terminal, and accordingly step 5 Through it, the uplink data sent by the terminal can be transmitted to the UPlink tunnel of the UPF included in the context of the terminal.

Step 6: The base station, according to the determination result of step 4, the terminal transmits data using the EDT, RAI for this RRC connection indicates only one uplink transmission, and if the data sent by the terminal is transmitted to the UPF, Suspend the RRC connection.

The base station sends a response to the RRC Resume connection of the terminal according to step 6 without Suspend the RRC connection of the terminal if the terminal did not transmit the data sent through the EDT to the UPF according to the determination result of step 4. Therefore, the terminal completes the RRC connection establishment and maintains the connection until the base station releases. In addition, the base station stores the data received from the terminal without transmitting it to the UPF. After activating the UPF and User Plane tunnels through step 13, the base station can transmit the stored Uplink data to the UPF.

Step 7: The base station informs the AMF and SMF of the location of the terminal, and sends an NGAP message to the AMF to inform that the connection of the terminal is activated. This message is a message indicating that the connection of the terminal has been resumed, and for convenience, the name will be described as a connection resume request. Alternatively, it may mean an initial UE message, or a message used to activate a user plane by notifying AMF and SMF after the connection status of the terminal is changed to RRC-Connected. This message may include the current location of the terminal, an ID that identifies the terminal, or a cause of the terminal RRC connection. In addition, the message may include an ID for a PDU session through which the terminal intends to transmit data. This is to allow the AMF to route the location of the terminal to the SMF managing the PDU session. The AMF can perform step 8 with the SMF corresponding to the PDU session ID.

Step 8: The AMF may send the message of Step 8 to the SMF managing the corresponding PDU Session if the message received from Step 7 includes the PDU Session ID. If there is no PDU Session ID in the message received from step 7, the AMF can view the terminal context and send the message of step 8 to all SMFs managing the PDU session for all PDU sessions the terminal has. The message of step 8 may include PDU Session ID (s), UE location information, and the like.

Step 9: The SMF receiving the message of step 8 can view the current location of the terminal and compare it with the service area of the UPF managing the corresponding PDU Session. If the UE is out of the UPF service area, the SMF can perform a procedure for changing the UPF. This operation is different according to the SSC mode for the PDU session of the terminal. In SSC mode 1, since the UPF serving as the PDU Session Anchor (PSA) is not changed, the SMF can decide to insert the I-UPF that can maintain the connection between the PSA and the base station while leaving the PSA intact. When selecting the I-UPF, the SMF selects the I-UPF having the most suitable UPF Service Area based on the location of the current terminal. In SSC mode 2, the current connection is disconnected and a new UPF and PDU Session is established. The SMF can perform the operation for this with the terminal and the base station. In SSC mode 3, the current connection is maintained for a certain period of time, but a new UPF and PDU Session can be established, and the user plane connection within a specific time can be changed with the newly established PDU Session. Even in SSC mode 2 or SSC mode 3, the user plane connection can be maintained by inserting an I-UPF.

Step 10: The SMF sends an N4 session establishment request to the selected I-UPF to establish a connection between the I-UPF and the PSA UPF. SMF provides the tunnel address of the PSA UPF and also the tunnel address of the base station. Upon receiving this, the UPF can establish a tunnel with the base station and a tunnel with the PSA UPF for the corresponding PDU Session. In response to the N4 session establishment request, the I-UPF includes its own tunnel information to the base station and its tunnel information to the PSA UPF.

Step 11: SMF performs an N4 Session Modification procedure on the PSA UPF to establish a tunnel connection between the I-UPF and the PSA UPF. Through this procedure, SMF delivers the tunnel information of I-UPF and the forwarding rule to the PSA UPF. Now the PSA UPF can pass the data it receives to the I-UPF.

Step 12: The SMF sends a response to Step 8. At this time, the SMF includes an N2 SM message, and this message includes information for establishing a data transmission tunnel connection between the I-UPF and the base station. That is, it contains the tunnel information of the I-UPF that the base station must use to send data. Also, the N2 SM message may include service area information of the newly allocated I-UPF. The UPF Service Area may consist of a list of RAN node IDs, a list of Tracking Area IDs, or a list of Cell IDs.

Step 13: The AMF delivers the N2 SM message received in step 12 to the base station. At this time, the response message of step 7 is used. Upon receiving this, the base station establishes a tunnel connection with the I-UPF. At this time, if there is no QoS-related information change, the base station does not need to reconfigure the radio resource connection. The base station that activated the connection with the UPF through the N2 SM message, if there is Uplink data of the terminal not sent in step 4, may transmit the corresponding uplink data to the UPF through step 14.

Step 15: If the N2 message received in the Connection Resume response of Step 13 has no N1 NAS message for the terminal, the base station may determine that the RRC connection of the terminal can be suspended. This determination is based on the RAI information of the terminal. For example, when the RAI informs that the UE sends only one Uplink, it can be determined that no further data transmission is necessary because the Uplink data of the UE is transmitted through Step 5 or Step 14. Therefore, it can be determined that the terminal's RRC connection is released or suspended. As another example, when RAI informs the UE that it sends one uplink and receives one downlink, and if the base station sends uplink data of the terminal and then sends downlink data to the terminal, it determines that all traffic of the terminal has been transmitted and received. You can decide to disconnect or Suspend the RRC. Or, if the terminal did not send the RAI in step 2, the base station sees the Traffic Profile in the context of the terminal, and the terminal usually sends and receives only one uplink, or receives one downlink for one uplink and enters the idle state (IDLE) You can judge whether it is transitioning. Accordingly, it is possible to see how the actual traffic of the terminal has been transmitted and received, and it can be determined that the terminal's RRC connection is released or suspended. Based on this determination, the base station can perform the Access Network Release procedure with the terminal and the AMF. This is to inform the Core Network that the terminal has entered an idle state.

9 is a diagram showing the structure of a terminal according to an embodiment of the present invention.

Referring to FIG. 9, the terminal may include a transceiver 910, a control unit 920, and a storage unit 930. In the present invention, the control unit may be defined as a circuit or application-specific integrated circuit or at least one processor.

The transceiver 910 may transmit and receive signals with other network entities. The transmitting and receiving unit 910 according to an embodiment of the present invention, the transmitting and receiving unit 910, for example, may transmit a message for resume the RRC connection to the base station, or may transmit a registration request message to the AMF.

The control unit 920 may control the overall operation of the terminal according to the embodiment proposed in the present invention. For example, the control unit 920 may control the signal flow between blocks to perform an operation according to the flowchart described above. For example, the controller 920 may control the transceiver 910 to transmit data using the EDT function, according to an embodiment of the present invention. In addition, the controller 920 may control the transceiver 910 to perform an AMF and a registration procedure to use the eDRX function according to an embodiment of the present invention.

The storage unit 930 may store at least one of information transmitted and received through the transceiver 910 and information generated through the controller 920. For example, the storage unit 930 may store RAI to be included in the RRC resume request message, information about the eDRX cycle to be included in the registration request message, and the like.

10 is a diagram showing the structure of a base station according to an embodiment of the present invention.

Referring to FIG. 10, the base station may include a transceiver 1010, a control unit 1020, and a storage unit 1030. In the present invention, the control unit may be defined as a circuit or application-specific integrated circuit or at least one processor.

The transceiver 1010 may transmit and receive signals with other network entities. The transmitting and receiving unit 1010 according to an embodiment of the present invention, the transmitting and receiving unit 1010, for example, receives a message for resume the RRC connection from the terminal, and can transmit information about the location of the terminal to AMF and SMF . In addition, the transmission / reception unit 1010 according to an embodiment of the present invention may transmit NAS signaling transmitted between the AMF and the terminal to each of the terminal and the AMF.

The controller 1020 may control the overall operation of the base station according to the embodiment proposed in the present invention. For example, the controller 1020 may control signal flow between blocks to perform an operation according to the flowchart described above. Specifically, the controller 1020 checks the location of the terminal based on a message for resuming the RRC connection received from the terminal according to an embodiment of the present invention, and transmits / receives the information to the AMF and SMF. 1010) can be controlled. In addition, the control unit 1020 according to an embodiment of the present invention may control the transmitting and receiving unit 1010 so that signaling for transitioning the terminal to the RRC inactive state is transmitted.

The storage unit 1030 may store at least one of information transmitted and received through the transceiver 1010 and information generated through the controller 1020. For example, the storage unit 1030 may store a terminal context according to an embodiment of the present invention.

11 is a view showing the structure of an AMF according to an embodiment of the present invention.

Referring to FIG. 11, the AMF may include a transmitting / receiving unit 1110, a control unit 1120, and a storage unit 1130. In the present invention, the control unit may be defined as a circuit or application-specific integrated circuit or at least one processor.

The transceiver 1110 may transmit and receive signals with other network entities. The transmitter / receiver 1110 may receive information on the location of the terminal from the base station, for example, and may transmit a session-related message to the SMF.

The controller 1120 may control the overall operation of the AMF according to the embodiment proposed in the present invention. For example, the controller 1120 may control signal flow between blocks to perform an operation according to the flowchart described above. Specifically, the control unit 1120 may control the transceiver 1110 to notify the SMF of the received terminal location-related information according to an embodiment of the present invention, determine the eDRX value for the terminal and transmit it to the base station The transmitter / receiver 1110 may be controlled to do so.

The storage unit 1130 stores data such as information transmitted and received through the transceiver 1110 and information generated through the controller 1120, and data such as a basic program for operating the AMF, application programs, and configuration information. The stored data may be provided at the request of the controller 1120.

12 is a view showing the structure of an SMF according to an embodiment of the present invention.

Referring to FIG. 12, the SMF may include a transceiver 1210, a controller 1220, and a storage 1230. In the present invention, the control unit may be defined as a circuit or application-specific integrated circuit or at least one processor.

The transceiver 1210 can transmit and receive signals with other network entities. The transmitter / receiver 1210 may receive information on the location of the terminal according to an embodiment of the present invention, for example, from a base station, and may receive session related information from the AMF.

The controller 1220 may control the overall operation of the terminal according to the embodiment proposed in the present invention. For example, the controller 1220 may control the signal flow between blocks to perform an operation according to the flowchart described above. Specifically, according to an embodiment of the present invention, the controller 1220 may control operations such as a comparison of a current location of a terminal and a service area of a UPF managing a corresponding PDU session and a procedure for changing a UPF.

The storage unit 1230 stores data such as information transmitted and received through the transmission / reception unit 1210, information generated through the control unit 1220, basic programs for operating the SMF, application programs, setting information, and the like. The stored data may be provided at the request of the controller 1220.

On the other hand, the embodiments of the present invention disclosed in this specification and the drawings are merely to provide a specific example to easily explain the technical contents of the present invention and to understand the present invention, and are not intended to limit the scope of the present invention. That is, it is obvious to those having ordinary knowledge in the technical field to which the present invention pertains that other modified examples based on the technical idea of the present invention can be implemented. In addition, each of the above embodiments can be operated in combination with each other as necessary. For example, some of the methods proposed in the present invention may be combined with each other to operate a base station and a terminal. In addition, although the above embodiments have been presented based on the LTE / LTE-A system, other systems based on the technical idea of the above embodiment may be implemented in other systems such as 5G and NR systems.

Claims (1)

In the control signal processing method in a wireless communication system,
Receiving a first control signal transmitted from a base station;
Processing the received first control signal; And
And transmitting a second control signal generated based on the processing to the base station.

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