KR20210069735A - Session establishment method, session management function entity base station and storage medium - Google Patents

Abstract

The disclosure (disclosure) relates to LTE (Long Term Evolution) and 4G (4 ^th generation) 5G to support higher data rates than the subsequent communication system (5 ^th generation) or pre-5G communication system such. Embodiments of the present disclosure provide a method for setting up a session, the process comprising: receiving a message for creating a session management context; selecting a user plane functional entity (UPF) for redundant session processing in response to the message for creating the session management context; and setting a packet data unit (PDU) corresponding to the UPF. Session establishment methods may be further provided by the base station and related devices. The above technical solutions can realize the reliability of service transmission.

Description

Session establishment method, session management function entity base station and storage medium

The present disclosure relates to the field of communication technology, and more specifically, a session setup method, a session management functional entity, a base station, and a storage medium. will be.

4G (4 ^th generation) to meet the traffic demand in the radio data communication system increases since the commercialization trend, efforts to develop improved 5G (5 ^th generation) communication system, or pre-5G communication system have been made. For this reason, the 5G communication system or the pre-5G communication system is called a 'beyond 4G network communication system' or a 'LTE (long term evolution) system after (post LTE) system'.

In order to achieve high data rates, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands (eg, 60 gigabytes (60 GHz) bands). To mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, in the 5G communication system, beamforming, massive multi-input multi-output (massive MIMO), and all-dimensional multiple input/output (full dimensional MIMO, FD-MIMO), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network (ultra-dense network) , device to device communication (D2D), wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), and reception interference cancellation (interference cancellation) Technology development is underway.

In addition, in the 5G system, hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC), which are advanced coding modulation (ACM) methods, and filter bank multi carrier (FBMC), which are advanced access technologies, are ), non orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are being developed.

Modern mobile communication tends to provide users with multimedia services transmitted at high speed, and some multimedia services must be transmitted very stably with low delay. In order to support this function, a concept of securing reliability of service transmission by establishing two packet data unit (PDU) sessions through two user plane function entities (UPFs) has been proposed. However, a specific solution for a method of establishing two PDU sessions has not been proposed.

Therefore, there is a need for a session establishment solution to achieve high and stable service transmission.

To this end, an embodiment of the present invention proposes a session setup method, a session management functional entity (SMF), a base station, and a storage medium.

According to a first aspect of the present disclosure, there is provided a session establishment method comprising:

Receiving a message for creating a session management context (session management context);

selecting a user plane functional entity (UPF) for redundant session processing in response to the message for creating the session management context; and

and setting a packet data unit (PDU) corresponding to the UPF.

In some embodiments, in response to the message for creating a session management context, the process of selecting a UPF for duplicate session processing includes:

The process of determining whether the session for which the session management context needs to be created is a duplicate session, and whether the duplicate session is a first duplicate session or a second duplicate session based on at least one;

information related to the duplicate session included in the message for creating the session management context; and

data network name (DNN) or single network slice selection assistance information (S-NSSAI) and network configuration of the operator;

and determining the UPF for duplicate session processing according to an identity of a serving base station of a user equipment (UE) based on the determination.

In some embodiments,

Receiving a first base station identifier of the base station in which the first redundant session is established and a second base station identifier of the base station in which the second redundant session is established;

selecting a UPF for the second overlapping session according to the second base station identifier and selecting a UPF for the first overlapping session according to the first base station identifier; or

Receiving the base station identifier of the base station to which the second overlapping session is established;

The method further comprising the step of selecting a UPF for the second overlapping session according to the base station identifier.

According to a second aspect of the present disclosure, in a wireless communication system, a method for establishing a session includes: a first base station for establishing a first redundant session for redundant handling, the method comprising:

Receiving a message for establishing a second redundant session for redundant handling,

determining whether to add a second base station for processing the second redundant session in response to the message; and

If the second base station is determined to be added, the method of establishing the second overlapping session processed by the second base station.

In some embodiments,

In response to the message, determining whether to add a second base station for processing the second redundant session includes:

determining whether the base station supports dual connectivity for the second redundant session and the first redundant session; and

If the base station supports dual connectivity, determining the addition of the second base station for establishing the second redundant session processed by the second base station;

otherwise, determining not to add the second base station.

In some embodiments,

storing information necessary for establishing the second redundant session when the first base station does not support dual connectivity; and

When it is determined that the first base station is capable of supporting dual connectivity, determining the addition of the second base station by using the stored information to establish the second redundant session processed by the second base station How to include.

In some embodiments, the process of establishing the second redundant session processed by the second base station includes:

requesting the second base station for establishing the second redundant session in the second base station;

receiving an acknowledgment message for acknowledging establishment of the second redundant session from the second base station;

receiving resources for the second redundant session established by user equipment (UE); and

and transmitting the configured resources to the second base station for establishing the second redundant session with the second base station.

Alternatively, the process of establishing the second redundant session processed by the second base station includes:

requesting the second base station for establishing the second redundant session in the second base station;

receiving an acknowledgment message for acknowledging establishment of the second redundant session from the second base station;

receiving resources for the second redundant session established by user equipment (UE); and

and transmitting the configured resources to the second base station for establishing the second redundant session with the second base station.

According to a third aspect of the present disclosure, in a wireless communication system, a method for handing over to a master base station for redundant session processing includes:

A process of receiving a handover request message transmitted by a third base station, wherein the handover request message requests a first base station to handover a main control function for redundant session processing of the third base station; ,

establishing a connection to a user equipment (UE) corresponding to the duplicate session processing based on the handover request message; and

A method comprising transmitting a path switch request message to a mobility management control entity.

In some embodiments, in response to the handover request message, the method further comprising adding a fourth base station for processing a second duplicate session among duplicate sessions of the third base station.

According to a fourth aspect of the present disclosure, a session management functional entity (SMF) includes:

processing unit; and

a storage unit storing machine readable instructions which, when executed by the processing unit, configure the processing unit to perform the method according to any one of claims 1 to 3 SMF.

According to a fifth aspect of the present disclosure, the base station comprises:

processing unit; and

A storage unit storing machine readable instructions that, when executed by the processing unit, configure the processing unit to perform the method according to any one of claims 4 to 8 or 9 to 10. A base station comprising a (storage unit).

According to a sixth aspect of the present disclosure, a session management functional entity (SMF) in a wireless communication system includes:

a message receiving unit, configured to receive a message for creating a session management context;

a UPF selection unit configured to select a user plane functional entity (UPF) for redundant session processing in response to the message for creating the session management context; and

and a session setup unit configured to establish a packet data unit (PDU) session corresponding to the UPF.

According to a seventh aspect of the present disclosure, a base station in a wireless communication system includes:

a message receiving unit, configured to receive a message for establishing a second redundant session for redundant handling;

a base station addition determination unit, configured to, in response to the message, determine whether to add a second base station for processing the second overlapping session; and

and a second redundant session configuration unit, configured to establish the second redundant session to be processed by the second base station if the second base station decides to add.

According to an eighth aspect of the present disclosure, a base station in a wireless communication system includes:

a message receiving unit, configured to receive a handover request message sent by a third base station, wherein the handover request message is a main control function for duplicate session processing of the third base station ( requesting handover of the main control function) to the first base station;

a connection setup unit, configured to establish a connection to a user equipment (UE) corresponding to the duplicate session processing based on the handover request message; and

A base station comprising a message transmitting unit configured to transmit a path switch request message to a mobility management control entity.

According to a ninth aspect of the present disclosure, a computer readable storage medium, when executed by a processor, causes a processor to perform the method according to the first aspect or the method according to the second aspect ( cause) a computer readable storage medium storing executable instructions.

Embodiments of the present disclosure can guarantee reliability of service transmission by establishing two redundant PDU sessions in each of two base stations.

The above and further aspects and advantages of the present application may be more clearly and readily understood from the following description in conjunction with the accompanying drawings.
1 shows a system architecture diagram of system architecture evolution (SAE).
Figure 2 shows a system architecture diagram of the Next Generation Network (next generation network), or 5-generation network (5 ^th generation network).
3 illustrates a schematic diagram of a session establishment method according to embodiments of the present disclosure.
4 schematically illustrates a method for handing over a second PDU session to a secondary base station according to embodiments of the present disclosure.
5 schematically shows a schematic diagram of a method for handing over a PDU session of redundant session processing to another base station according to embodiments of the present disclosure.
6 schematically shows a schematic diagram of another method for handing over a PDU session of duplicate session processing to another base station according to embodiments of the present disclosure.
7 schematically shows a schematic diagram of another session establishment method according to embodiments of the present disclosure.
8 schematically shows a schematic diagram of another session establishment method according to embodiments of the present disclosure.
9 schematically illustrates a schematic diagram of a system supporting reliable session transmission according to embodiments of the present disclosure.
10 is a schematic flowchart of a session establishment method according to embodiments of the present disclosure.
11 illustrates a schematic flowchart of another session establishment method according to embodiments of the present disclosure.
12 is a schematic block diagram of a session management function entity (SMF) for session establishment according to embodiments of the present disclosure.
13 is a schematic block diagram of a base station for session establishment according to embodiments of the present disclosure.
14 is a schematic flowchart of a method for handing over a master base station for redundant session processing according to embodiments of the present disclosure;
15 is a schematic block diagram of an apparatus for handing over a master base station for redundant session processing according to embodiments of the present disclosure.
16 schematically illustrates a block diagram of a computing system that may be used to implement an SMF or a base station of the present disclosure, according to embodiments of the present disclosure.
In the accompanying drawings, identical or similar structures may be identified by identical or similar reference numerals.

본 개시는 첨부된 도면들 및 특정 실시 예들과 관련하여 아래에서 상세히 설명될 것이다. 본 개시는 아래에서 설명되는 특정 실시 예들로 제한되지 않는 것으로 이해될 수 있다. 본 명세서에 예시된 특정 실시 예들은 예시적인 것으로, 본 개시를 설명하기 위해 사용될 뿐, 본 개시를 제한하는 것으로 해석될 수 없다. 또한, 편의를 위해, 본 개시에 대한 이해의 혼동을 피하기 위하여 본 개시의 내용과 직접적으로 관련되지 않은 공지된 기술에 대한 상세한 설명은 생략된다.

The present disclosure will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It may be understood that the present disclosure is not limited to the specific embodiments described below. The specific embodiments illustrated in this specification are illustrative and are used only to describe the present disclosure, and should not be construed as limiting the present disclosure. In addition, for convenience, detailed descriptions of well-known technologies that are not directly related to the contents of the present disclosure are omitted to avoid confusion in understanding the present disclosure.

It will be understood by those skilled in the art that the singular forms "a", "an", and "the" used herein may include the plural forms unless otherwise stated. Also, as used herein, the phrase “comprise” refers to features, integers, steps, operators, elements and/or or to the presence of components, but not to exclude the presence or addition of one or more other features, integers, steps, operations, elements and/or components. can be When an element is referred to as being “connected” or “coupled” to another element, it may be understood to be directly connected or coupled to the other element or with an intermediate element between them. have. Also, as used herein, “connected” or “coupled” may include wireless connection or wireless coupling. As used herein, the phrase “and/or” may include all one or more of the related list items or all combinations thereof.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the content of this disclosure belongs, unless otherwise defined. It can be understood by those skilled in the art. Terms such as terms defined in a general dictionary may be understood to have a meaning consistent with the meaning of the corresponding term. It is not described in an idealized or overly formal sense unless specifically defined.

1 shows a system architecture diagram of system architecture evolution (SAE). Here, the user equipment (UE) 101 may be a terminal device for receiving data. The evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network comprising a macro-base station (eNodeB/NodeB) for providing the UE with an interface for accessing the radio network. can be

A mobility management entity (MME) 103 may manage the UE's mobile context, session context, and security information. A serving gateway (SGW) 104 mainly provides a function of a user plane and may be located in the same physical entity as the MME 103 . A packet data network entity (PGW) 105 may be in charge of functions such as charging, lawful interception, and the like. It may also be located in the same physical entity as the SGW 104 . A policy and charging rules function entity (PCRF) 106 may provide quality of service (QoS) policies and charging criteria. The general packet radio service support node (SGSN) 108 may be a network node device of a universal mobile telecommunications system (UMTS) that provides routing for data transmission. The home subscriber server (HSS) 109 is a home subsystem of the UE and can protect user information including the current location of the UE, the address of the serving node, user security information, and packet data context of the UE. have.

Figure 2 shows a system architecture diagram of the Next Generation Network (next generation network), or 5-generation network (5 ^th generation network). Here, the UE 101 may be a terminal device that receives data. The next generation-radio access network (NG-RAN) 102 is a radio access network including a base station (a gNB or eNB connected to a 5G core network (5GC)), for accessing the radio network to the UE. interface can be provided. An access control and mobility management function entity (AMF) 103 may manage mobile context and security information of the UE. A user plane functional entity (UPF) 104 may mainly provide a function of a user plane. A session management function entity (SMF) 105 may be in charge of session management. Data network (DN) 106 may include, for example, operator's services, Internet access and third party services, and the like.

To support highly reliable service transmission with low latency, Rel-15 mainly considers an air interface, and the same architecture and session establishment method can be used to support various services on the network side. have.

One solution being discussed now to support high reliability service transmission with low latency is to establish a redundant user plane. That is, two PDU sessions may be established through two UPFs to ensure reliability of service transmission. However, there is no specific discussion on how to establish two PDU sessions. In particular, there is no specific discussion on a method of selecting an appropriate UPF while establishing PDU sessions, a method of supporting handover, and the like.

A solution according to the present disclosure will be described in detail below with reference to the accompanying drawings.

3 illustrates a schematic diagram of a session establishment method according to embodiments of the present disclosure. Detailed descriptions of steps not related to the present disclosure may be omitted below. The method of the present disclosure may include the following steps.

In step 301, the terminal may transmit a PDU session setup request message to the AMF. The terminal may transmit a PDU session establishment request message to the base station through the RRC message. The base station may transmit a PDU session establishment request message to the AMF through an NG access protocol (AP) message (NGAP message). Here, the base station may be the NG-RAN node 1. The PDU session establishment request message may include a redundant sequence number (RSN). RSN may indicate redundant handling. The value of RSN may indicate whether to establish a first PDU session or a second PDU session.

In step 302, the AMF may transmit a session creation management context request message to the SMF. In this embodiment, there may be three methods of selecting the UPF.

In the first method, for each of the first PDU session and the second PDU session for redundancy processing, the UPF may be selected according to the identity of the master base station. For this method, in step 302, the AMF transmits the base station identifier of the base station to which the UE is connected to the SMF or the NG-RAN node 1 receives the identifier of the master base station or the cell identifier of the master base station accessed by the UE through the AMF. can be transmitted Here, the cell may be a primary cell of the master base station accessed by the UE as described in detail below.

In a second method, in step 304, the SMF may select a UPF according to an existing mechanism. In steps 311 and 312, in the NG-RAN node 1, the identity of the base station to which each PDU session is to be established or the identifier of the cell of the base station accessed by the UE is transmitted to the SMF through the AMF PDU session It may be included in the setup approval message. The SMF may reselect UPFs for the first PDU session and the second PDU session, respectively. Here, the SMF may select the UPF for the first PDU session and the second PDU session in consideration of the identifier of the master base station and the identifier of the secondary base station. Here, the cell of the base station accessed by the UE may be the primary cell of the base station accessed by the UE, for example, the primary cell of the master base station or the primary cell of the secondary base station, and the cell of the base station accessed by the UE is below. It is not explained again if it is cited in When the identifier of the cell of the base station to which the terminal is connected is received by the SMF, the SMF may obtain the identifier of the base station according to the identifier of the cell, which is true below and will not be described again. The SMF may select a UPF close to the master base station and the secondary base station, respectively.

In the third method, the SMF may select the UPF according to the identity of the master base station in step 304 for the first PDU session and the second PDU session for redundancy processing. This is detailed in step 304 below. In steps 311 and 312, the identifier of the secondary base station to which the second PDU session is to be established may be included in the PDU session setup acknowledgment message transmitted from the NG-RAN node 1 to the SMF through the AMF. have. In addition, the SMF may select the UPF for the second PDU session again. The SMF may select the UPF for the second PDU session in consideration of the identifier of the secondary base station or the identifier of the cell of the secondary base station. When the SMF receives the identifier of the cell of the base station, the SMF may obtain the identifier of the base station according to the identifier of the cell. The SMF may select a UPF close to the secondary base station. For convenience of explanation, in the method according to the present disclosure, the first PDU session is established in the master base station and the second PDU session is established in the secondary base station to establish dual connectivity for the PDU session for duplication processing. A method is described. In actual applications, which PDU session is established in the master base station and which PDU session is established in the secondary base station may be determined by the SMF or NG-RAN. According to the method determined by the SMF, the SMF may indicate the above information to the NG-RAN through the RSN.

AMF may transmit a base station identifier (identity) of a base station to which the UE is connected or an identifier of a cell to which the UE is connected to the SMF. AMF can know the base station to which the terminal is connected by receiving the NGAP message from the base station. Here, the base station may be the NG-RAN node 1.

In step 303 , the SMF may transmit a session creation management context response message to the AMF.

In step 304, the SMF may select a UPF. The SMF may select the UPF in consideration of a base station identity or a cell identifier received from the AMF. The base station identifier received by the SMF may be an identifier of a master base station or an identifier of a secondary base station. The secondary base station may also be referred to as a second base station. When the SMF receives the identifier of the cell of the base station, the SMF may obtain the base station identifier according to the cell identifier. The SMF may know that the PDU session is used for redundancy processing based on RSN or data network name (DNN) or single network slice selection assistance information (S-NSSAI) received from the UE and network configuration. In addition, it may be known whether the PDU session is the first PDU session or the second PDU session. The SMF may select the UPF in consideration of the information that the PDU session is the first PDU session for duplication processing and the received base station identifier or cell identifier. If the SMF does not receive the RSN from the UE, the SMF may determine to establish a first PDU session or a second PDU session for duplication processing using DNN or S-NSSAI together with an operator's configuration. The SMF may select the UPF using information that the first PDU session or the second PDU session is established together with other information.

In step 305 , the SMF may transmit an N4 session setup request message or an N4 session modification request message to the selected UPF. If the request is an initial request, the SMF may initiate an N4 session establishment procedure for the selected UPF. Otherwise, the SMF may initiate the N4 session modification procedure for the selected UPF.

In step 306 , the UPF may transmit an N4 session setup response or an N4 session modification response message to the SMF.

In step 307, the SMF may transmit an N1N2 message transmission message to the AMF. The message may include a PDU session ID (PDU session ID), N2 session management information (N2 SM information), and an N1 session container (N1 session container). The message may include information on duplicate PDU session processing. The information on duplicate PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using RSN. The information on the duplicate PDU session processing may further indicate a relationship between two PDU sessions for duplicate handling. The SMF may configure the same RSN value for two PDU sessions to indicate that the two PDU sessions are related PDU sessions for duplication processing.

In step 308 , the AMF may transmit a PDU session setup request message to the NG-RAN node 1. The message may include information on duplicate PDU session handling. The information on the duplicate PDU session processing may indicate whether the PDU session is a first PDU session or a second PDU session using RSN. The information on the duplicate PDU session processing may also indicate an association relationship between two PDU sessions for duplicate handling, for example, to inform NG-RAN node 1 that two PDU sessions are used for duplicate handling. RSNs for both PDU sessions of the message may be configured with the same value to inform NG-RAN Node 1 that the two PDU sessions are related PDU sessions for duplication processing. The association between two PDU sessions for redundancy processing may be equally indicated throughout the specification, and a description thereof will be omitted.

The NG-RAN node 1 may know that the PDU session to be set according to the received PDU session setup request message is used for duplication processing (handling). The NG-RAN node 1 may also know whether the PDU session to be established is the first PDU session or the second PDU session, or the NG-RAN node 1 may know which two PDU sessions are used for duplication processing. When the PDU session to be set is used for redundancy processing and the PDU session to be set is the second PDU session, the NG-RAN node 1 may establish the second PDU session to a base station different from the first PDU session. For example, if the first PDU session is a bearer terminated by a master node (MN), the second PDU session should be configured as a bearer terminated by a secondary node (SN). As an implementation method of the present disclosure, the first PDU session may be configured as a bearer terminated by the MN, and the second PDU session may be configured as a bearer terminated by the SN. The first PDU session may be established as a bearer terminated by the SN and the second PDU session may be established as a bearer terminated by the MN. Whether a master cell group (MCG) bearer, a secondary cell group (SCG) bearer, or a split bearer is used as a basic resource is not limited herein. For two PDU sessions for redundant processing, it may be relatively easy to use the MCG bearer as the bearer terminated by the MN and the SCG bearer as the bearer terminated by the SN.

Here, the NG-RAN node 1 may directly establish a second PDU session to the secondary base station (eg, NG-RAN node 2) or first establish a second PDU session to the NG-RAN node 1, after which the UE Only after being fully configured and a response to the core network is made, an SN addition procedure for handing over the second PDU session to the secondary base station may be performed. For the latter method in which the second PDU session is first established in NG-RAN Node 1, it may not be necessary to perform steps 309a, 309b and 310b.

In step 309a, if the NG-RAN node 1 determines to establish a second PDU session in the NG-RAN node 2, the NG-RAN node 1 sends an SN addition request message to the NG-RAN node 2 can be transmitted. The message may include information on duplicate PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using RSN. The information on the duplicate PDU session handling may indicate a relationship between two PDU sessions for duplicate handling, for example, two PDU sessions used for duplicate handling may be notified to the NG-RAN node 2. The NG-RAN node 2 may store information on redundant PDU session processing, and the NG-RAN node 2 may establish a PDU session with the bearer terminated by the SN. The NG-RAN node 2 may not hand over the bearer to the bearer terminated by the MN.

In step 309b, the NG-RAN node 2 may transmit an SN addition request acknowledgment message to the NG-RAN node 1 . The NG-RAN node 2 may allocate downlink tunnel information for an NG interface for a PDU session to be established as a bearer terminated by the SN. The tunnel information may include a tunnel end number and a transport layer address.

For example, if NG-RAN node 1 cannot configure dual connectivity (DC) for the UE, according to the UE's measurement report, NG-RAN node 1 does not allocate resources to the second PDU session. It may not be, and in step 311, the PDU session in the NG-RAN node 1 may be included in the list of PDU sessions in which resource setup has failed. For example, failure reasons, such as not being able to establish the second PDU session or DC configuration not supported, may be included in PDU session resource setup failure transfer information. In the case of the second PDU session in which the establishment fails, the SMF may not trigger the second PDU session establishment procedure for the NG-RAN. As will be described in detail in step 311, the NG-RAN node 1 may configure a second PDU session in the NG-RAN node 1 as described.

In step 310 , the NG-RAN node 1 may transmit an RRC connection reconfiguration message to the terminal. NG-RAN node 1 may transmit a received NAS message (NAS message) to the UE. The UE may transmit an RRC connection reconfiguration completion message to the NG-RAN node 1. Through this step, the resource for the PDU session to be established may be configured.

In step 310b, the NG-RAN node 1 may transmit an SN reconfiguration completion message to the NG-RAN node 2.

Here, there may be no absolute order of steps 310b and 311 .

In step 311, the NG-RAN node 1 may transmit a PDU session setup acknowledgment message to the AMF.

Corresponding to the second method of selecting the UPF, in the NG-RAN node 1, the base station identifier of the base station to which the PDU session is to be established or the identifier of the cell of the base station accessed by the UE is transmitted PDU session resource setup response (PDU session) resource setup response transfer). For example, when the first PDU session is established in the NG-RAN node 1, the identifier of the NG-RAN node 1 or the identifier of the cell of the NG-RAN node accessed by the UE is to be included in the response information of the first PDU session. can When the second PDU session is established in the NG-RAN node 2, the identifier information of the NG-RAN node 2 or the identifier information of the cell of the NG-RAN node 2 accessed by the UE may be included in the response information of the second PDU session. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

Corresponding to the third method of selecting the UPF, when the second PDU session is established in the secondary base station for establishing the second PDU session for redundant PDU processing, the message includes the identity of the secondary base station or the secondary base station Identification of the cell of may include. In this embodiment, the message may include the identifier of the NG-RAN node 2 accessed by the UE or the identifier of the cell of the NG-RAN node 2 accessed by the UE. The message may include information on a downlink tunnel allocated by the NG-RAN for the PDU session to be established.

If the second PDU session is not established in the secondary base station, there may be two processing methods in the present disclosure.

In the first method, the NG-RAN may not allocate resources including radio resources and network resources to the second PDU session, and the second PDU session may not be established. In the NG-RAN node 1, the second PDU session may be included in a list of PDU sessions in which resource setup has failed in a PDU session setup response message. The PDU session list in which resource establishment has failed may include identities of PDU sessions and reasons for failure (eg, dual connection establishment failure or DC configuration not supported). The SMF may determine whether to maintain the first PDU session in the redundant PDU session or release the first PDU session in the redundant PDU session according to a local policy.

In the second method, the NG-RAN node 1 may establish a second PDU session in the NG-RAN node 1. That is, two PDU sessions for duplication processing may not be configured with dual connectivity. In the NG-RAN node 1, the second PDU session may be included in a PDU session resource setup list of a PDU session setup response message, where the PDU session resource setup response includes identifiers of PDU sessions. may include The PDU session resource establishment response may further include information that two PDU sessions are not configured with dual connectivity, information that two PDU sessions have failed dual connectivity configuration, or information that a second PDU session is not established in the secondary base station. In the NG-RAN node 1, the PDU session resource setup resource may include a base station identifier of a base station configured with a second PDU session or an identifier of a primary cell of the base station. SMF is the base station identifier (identity) of the base station in which the second PDU session is configured, or the identifier of the primary cell of the secondary base station in which the second PDU session is not established, or in the dual connectivity mode, two duplicate PDU sessions are not configured. It can be notified implicitly through the identifier of the head cell. The SMF is two PDUs for overlapping processing according to the identifier of the received base station, which is the identifier of the primary cell of the base station in which the second PDU session is configured or received, and the identifier of the primary cell of the master base station or the identifier of the master base station. It can be seen that the sessions were not successfully configured with the DC. When it implicitly informs the SMF that two PDU sessions are not successfully configured with dual connectivity, the NG-RAN node 1 is the base station identifier of the base station in which the first PDU session is configured or the primary cell of the corresponding base station. An identifier (eg, an identifier of NG-RAN Node 1) may be transmitted to the SMF. Accordingly, the SMF is based on the base station identifier of the base station in which the first PDU session is configured or the identifier of the primary cell of the corresponding base station, and the base station identifier of the base station in which the second PDU session is configured or the base station identifier of the primary cell of the corresponding base station. It can be seen that the two PDU sessions for duplication processing were not successfully configured with dual connectivity. The NG-RAN node 1 may transmit the base station identifier of the base station configured with the first PDU session or the identifier of the primary cell of the base station to the SMF in the process of establishing the first PDU session or in the current step. The SMF may determine whether to maintain the second PDU session or release the second PDU session according to the local policy. In this case, if the NG-RAN node 1 does not receive the message to release the second PDU session, when the NG-RAN node 1 can hand over the second PDU session to the secondary base station, NG -RAN node 1 establishes the second PDU session in the secondary base station and configures the second PDU session as a bearer terminated by the SN. A secondary node (SN) addition process can be performed. have. The NG-RAN node 1 may inform the SMF that the second PDU session has been successfully configured or that dual connectivity has been successfully configured in the secondary base station, and the NG-RAN node 1 is the identifier of the secondary base station or the secondary base station accessed by the UE. The identifier of the cell may be further informed to the SMF. The SMF may determine whether to reselect the UPF for the second PDU session by using the identifier of the base station or the identifier of the cell of the secondary base station. The identifier of the cell of the secondary base station may be the cell identifier of the primary cell of the secondary base station selected for the UE.

In step 312, the AMF may transmit an update session management context request message to the SMF. The AMF may transmit the identifier of the master base station and/or secondary base station received from NG-RAN node 1 or the identifier of the cell of the master base station accessed by the UE and/or the identifier of the cell of the secondary base station accessed by the UE to the SMF. have. The AMF may transmit the session management information received from the NG-RAN to the SMF.

Corresponding to the second method of selecting the UPF, when the SMF receives the identifier of the base station or the identifier of the cell of the base station accessed by the UE, the SMF generates the UPFs for the first PDU session and/or the second PDU session. can be re-selected. The SMF may select the UPF for the first PDU session and the second PDU session in consideration of the identifier of the master base station and the identifier of the secondary base station, respectively. The SMF may select a UPF close to the master base station and the secondary base station, respectively. The identifier of the base station may be used as an input for UPF reselection. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

Corresponding to the third method of selecting the UPF, when the SMF receives the identifier of the secondary base station to which the UE is connected or the identifier of the cell of the secondary base station, the SMF may reselect the UPF for the second PDU session. The identifier of the secondary base station may be used as an input for UPF reselection. The SMF may select the UPF providing the second PDU session in consideration of the identifier of the secondary base station. The SMF may select a UPF close to the secondary base station. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The message may include information of a tunnel allocated by the NG-RAN for the PDU session to be established.

In step 313 , the SMF may transmit an N4 session modification request message to the UPF. When the UPF is reselected, the SMF may transmit an N4 session modification request message to the reselected UPF. The SMF may transmit information of a downlink tunnel allocated by the NG-RAN to the UPF for data transmission through an NG interface. In the case of a PDU session that the NG-RAN has not established, the SMF may request the UPF to delete the corresponding downlink user plane tunnel information, and the UPF may delete the corresponding PDU session or mark the corresponding PDU session as inactive.

In step 314 , the UPF may transmit an N4 session modification response message to the SMF.

In step 315, the SMF may transmit an update session management context acknowledgment message to the AMF.

So far, a method for supporting reliable session transmission and a method for establishing a first session according to the present invention have been described. In this way, two redundant PDU sessions may be established at two base stations to ensure reliability of transmission, and UPFs close to two base stations may be selected respectively to reduce transmission delay.

4 is a schematic diagram of a method for handing over a second PDU session to a secondary base station (eg, NG-RAN node 2 in FIG. 3 ) according to an embodiment of the present disclosure; show Corresponding to the establishment of the second PDU session in the redundancy processing, the method may first establish, by the master base station, the second PDU session in the master base station (eg, NG-RAN node 1 in FIG. 3 ). And only after the UE is fully configured and the response to the core network is made, the method is an SN addition procedure for handing over the second PDU session to the secondary base station (eg, NG-RAN node 2 in Figure 3). can be done The method may include the following steps in which detailed descriptions of steps not related to the present disclosure are omitted.

In step 401, a master node (MN) may transmit an SN addition request message to a secondary node (SN). The message may include information on redundant PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using a redundant sequence number (RSN). The information on the duplicate PDU session handling may indicate a relationship between two PDU sessions for duplicate handling, for example, it may inform the SN of two PDU sessions used for duplicate handling. The SN may store information on duplicate PDU session processing, and the SN may set the PDU session as a bearer terminated by the SN. The SN may not hand over the bearer to the bearer terminated by the MN.

In step 402, the SN may transmit an SN addition request acknowledgment message to the MN. The SN may allocate downlink tunnel information for the NG interface for a PDU session to be established as a bearer terminated by the SN. Tunnel information may be composed of a tunnel end number and a transport layer address.

For example, if the SN cannot accept the requested configuration, the SN is an SN addition request rejection message to the MN due to a limitation of radio resources or a SN addition preparation failure (failure). message) can be sent. There may be two processing methods in the present disclosure.

In the first method, the MN may maintain a second PDU session to be configured in the MN. The MN may send a message to the AMF, where the message may include an identifier of the PDU session and information that dual connectivity is not configured. The message may be an existing PDU session resource modification request message, a PDU session resource notification message, or a newly defined message. The AMF may transmit to the SMF the identifier of the PDU session and information indicating that the dual connection configuration failed. The MN may transmit the base station identifier of the base station configured with the second PDU session or the identifier of the primary cell of the base station to the SMF. The SMF may be implicitly notified through the base station identifier of the base station in which the second PDU session is configured or the primary cell identifier of the base station in which the second PDU session is not configured in the secondary base station or two overlapping PDUs. The SMF is two PDUs for overlapping processing according to the identifier of the received base station, which is the identifier of the primary cell of the base station in which the second PDU session is configured or received, and the identifier of the primary cell of the master base station or the identifier of the master base station. It can be seen that the sessions were not successfully configured with the DC. When the two PDU sessions are not successfully configured with dual connectivity implicitly (implicitly) informing the SMF that the MN is also the base station identifier of the base station in which the first PDU session is configured or the identifier of the primary cell of the corresponding base station (eg : MN identifier) can be transmitted to the SMF. Accordingly, the SMF is based on the base station identifier of the base station in which the first PDU session is configured or the identifier of the primary cell of the corresponding base station, and the base station identifier of the base station in which the second PDU session is configured or the base station identifier of the primary cell of the corresponding base station. It can be seen that the two PDU sessions for duplication processing were not successfully configured with dual connectivity. In the process or this step of establishing the first PDU session, the MN may transmit the base station identifier of the base station configured with the first PDU session or the identifier of the primary cell of the base station to the SMF. The SMF may determine whether to maintain the second PDU session or release the second PDU session according to the local policy. In this case, if the MN does not receive the message to release the second PDU session, when the MN can hand over the second PDU session to the secondary base station, the MN performs the SN addition procedure to 2 PDU sessions can be established. The secondary base station may configure the second PDU session as a bearer *?* terminated by the SN. The MN may inform the SMF through the AMF that the second PDU session has been successfully configured or that the dual connection has been successfully configured in the secondary base station. The MN may further inform the identifier of the secondary base station or the identifier of the secondary base station accessed by the UE through the AMF. In addition, the SMF may determine whether to reselect the UPF for the second PDU session using the identifier of the secondary base station or the identifier of the cell of the secondary base station. The identifier of the cell of the secondary base station may be the cell identifier of the primary cell of the secondary base station selected for the UE.

In the second method, the MN may release the second PDU session. The MN may transmit a PDU session resource notification message to the AMF. The PDU session resource release information of the PDU session resource notification message may include an identifier of a PDU session and a reason for failing to establish a dual connection. The AMF may transmit PDU session information to the SMF. The SMF may determine whether to maintain the first PDU session in duplicate PDU sessions or release the first PDU session in duplicate PDU sessions according to a local policy. When the MN receives the SN addition request rejection message transmitted by the SN, it may not be necessary to perform the subsequent steps 403 to 412 .

In step 403, the MN may transmit an RRC connection reconfiguration message (RRC connection reconfiguration me) to the terminal.

In step 404, the UE may transmit an RRC connection reconfiguration complete message to the MN.

A resource for establishing a PDU session may be established through steps 403 and 404 .

In step 405 , the MN may transmit an SN reconfiguration completion message to the SN.

Here, there is no absolute order for step 405 and steps 407, 408 and 409.

In step 406, the MN RLC (radio link control) acknowledgment mode (acknowledgment mode, AM) is terminated (terminated) by a SN (secondary node) for a bearer (bearer) SN (sequence number) status transmission message (SN state transition message) may be transmitted to the SN.

In step 407, for the bearer terminated by the SN using the RLC AM, the MN may start a data forwarding procedure according to the bearer characteristics of the corresponding QoS flow.

In step 408, for the bearer terminated by the SN, the MN may transmit a PDU session modification indication message to the AMF.

The message may include the identifier of the secondary base station or the identifier of the cell of the secondary base station accessed by the UE. The identifier of the secondary base station or the identifier of the cell of the secondary base station accessed by the UE may be included in PDU session modification indication transfer information. The message may include information on a downlink tunnel allocated by the SN for the PDU session to be established.

In step 409, the AMF may transmit an update session management context request message to the SMF. The AMF may transmit the identifier of the secondary base station or the cell identifier of the secondary base station accessed by the UE received from the MN to the SMF.

When the SMF receives the identifier of the secondary base station or the identifier of the cell of the secondary base station accessed by the UE, the SMF may reselect the UPF for the second PDU session. The identifier of the secondary base station may be used as an input for UPF reselection. The SMF may select the UPF providing the secondary PDU session in consideration of the identifier of the secondary base station. The SMF may select a UPF close to the secondary base station. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The message may include information on a tunnel allocated by the MN for the PDU session to be established.

In step 410 , the SMF may transmit an N4 session modification request message to the UPF. When the UPF is reselected, the SMF may transmit an N4 session modification request message to the reselected UPF. The SMF may transmit information of a downlink tunnel for an NG interface allocated by the MN to the UPF for data transmission. The UPF may transmit an N4 session modification response message to the SMF.

In step 411, the SMF may transmit an update session management context acknowledgment message to the AMF.

In step 412, the SMF may transmit a PDU session modification acknowledgment message to the MN.

So far, a method for the master base station according to the present disclosure to hand over the second PDU session to the secondary base station has been described. Using this method, two overlapping PDU sessions can be established with two base stations to ensure transmission reliability, and transmission delay can be reduced by selecting UPFs close to the two base stations, respectively.

5 schematically shows a schematic diagram of a method for handing over a PDU session of redundant session processing to another base station according to embodiments of the present disclosure. Detailed descriptions of steps irrelevant to the present disclosure are omitted herein. The method may include the following steps.

In step 501 , a source MN may transmit a handover request message to a target MN. In the source MN, the UE XnAP identity of the source SN, the identifier of the SN, and the context of the UE in the source SN may be included in the handover request message. The handover request message may be composed of an MCG configuration and an SCG configuration. The handover request message may include information on redundant PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using a redundant sequence number (RSN). The information on the duplicate PDU session handling may further indicate a relationship between two PDU sessions for duplicate handling. For example, two PDU sessions used for overlap handling may be notified to the target MN. The target MN may store information on duplicate PDU session processing. The target MN may establish two PDU sessions for duplication processing: a bearer *?* terminated by the MN and a bearer *?* terminated by an SN. For example, the MN may establish a first PDU session as a bearer terminated by the MN, and the MN may establish a second PDU session as a bearer terminated by the SN.

The target MN may decide whether to reserve the source SN or select a new target SN.

In step 502 , the target MN may transmit an SN addition request message to the SN. Depending on the target MN's decision on whether to reserve the source SN or select a new target SN, the SN may be the source SN or the target SN. The message may include information on redundant PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using a redundant sequence number (RSN). The information on the duplicate PDU session handling may indicate a relationship between two PDU sessions for duplicate handling, for example, it may inform the SN of two PDU sessions used for duplicate handling. The SN may store information on duplicate PDU session processing, and the SN may set the PDU session as a bearer terminated by the SN. The SN may not hand over the bearer to the bearer terminated by the MN.

In step 503, the SN may transmit an SN addition request acknowledgment message to the target MN.

In step 504, the target MN may transmit a handover request acknowledgment message to the source MN.

In step 505a, the source MN may transmit an SN release request message to the source SN. When the source SN receives the information indicating the UE's context reservation, the source SN may reserve the UE's context.

In step 505b, the source SN may transmit an SN release request acknowledgment message to the source MN.

In step 506 , the source MN may transmit an RRC connection reconfiguration message to the UE.

In step 507 the UE may be synchronized to the target MN.

In step 508, the UE may transmit an RRC connection reconfiguration completion message to the target MN.

If the bearer using the SCG radio resource is established in step 509, the UE may be synchronized to the SN, and if the MN selects a new SN, the SN may become the target SN.

After the RRC connection reconfiguration is successful in step 510 , the target MN may transmit an SN reconfiguration completion message to the SN.

In step 511, in the case of a bearer using a radio link control acknowledgment mode (RLC AM) mode, the source MN may transmit an SN state transition message to the target MN.

In step 512 , the source MN may forward the data to the target MN. When the SN is reserved, data forwarding may not be required for the SCG bearer and the SCG split bearer.

In step 513, the target MN may transmit a path switch request message to the AMF.

In the target MN, the base station identifier of the base station to which the PDU is to be configured or the identifier of the cell of the base station to which the UE is accessed may be included in path switch request transfer. When the first PDU session is established in the target MN, the identifier of the target MN or the identifier of the cell of the target MN accessed by the UE may be included in the path switch request transmission information of the first PDU session, and the second PDU session is the target When configured in the SN or source SN, the identifier of the target SN or the identifier of the source SN or the identifier of the cell of the target SN accessed by the UE or the identifier of the cell of the source SN accessed by the UE is the path switch request of the second PDU session It may be included in the transmission information.

For establishment of the second PDU session for redundant PDU processing, when the second PDU session is to be established in the secondary base station, the message may include the identifier of the secondary base station or the identifier of the cell of the secondary base station. That is, in this embodiment, the identifier of the target SN or the identifier of the source SN or the cell identifier of the cell of the target SN accessed by the UE or the cell identifier of the cell of the source SN accessed by the UE may be included in the message. The message may include information of a downlink tunnel allocated by the MN for the PDU session to be established.

The message may include the identifier of the secondary base station accessed by the UE or the cell identifier of the cell of the secondary base station. The path switch request transmission information may include an identifier of a secondary base station or a cell identifier of a cell of a secondary base station accessed by the UE. The message may include information of a downlink tunnel allocated by the SN for the PDU session to be established.

If two PDU sessions for duplication processing are not configured in dual connectivity in the target base station, the target base station may inform the SMF of this information. The target base station may notify the SMF in an explicit manner including, for example, an information element that the DC was not successfully configured in a path switch request message. The target base station may also inform the SMF in an implicit way. That is, the target base station may inform the SMF of the base station identifier of the base station in which each PDU session is established or the identifier of the primary cell of the base station. The SMF may know whether the DC has been successfully configured according to the information, and may determine whether to maintain the second PDU session or release the second PDU session according to the local policy.

In step 514, the AMF may transmit an update session management context request message to the SMF. The AMF may transmit the identifier of the base station or the cell identifier received from the target MN to the SMF. For each PDU session, when the SMF receives the identifier or cell identifier of the base station to which the PDU session is to be established, the SMF may select the UPF for the PDU session using the received identifier of the base station. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

When the SMF receives the identifier of the secondary base station or the cell identifier of the cell of the secondary base station accessed by the UE, the SMF may reselect the UPF for the second PDU session. The identifier of the secondary base station may be used as an input for UPF reselection. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The message may include information on a tunnel allocated by the target MN for the PDU session to be established.

In step 515, the SMF may transmit an N4 session modification request message to the UPF. When the UPF is reselected, the SMF may transmit an N4 session modification request message to the reselected UPF. The SMF may transmit information of a downlink tunnel allocated by the NG-RAN to the UPF for data transmission through an NG interface.

Upon receiving the N4 session modification request message, the UPF may transmit an N4 session modification response message to the SMF.

In step 516, the SMF may transmit an update session management context acknowledgment message to the AMF.

In step 517, the UPF may transmit data to the target MN. The UPF may transmit downlink data to the target MN according to the received downlink tunnel information allocated by the target MN. In the case of a bearer terminated by the MN, the corresponding UPF (eg, UPF1) may transmit downlink data to the target MN. In the case of a bearer terminated by an SN, the corresponding UPF (eg, UPF2) may transmit downlink data to the source SN or the target SN (according to whether the SN is changed).

In step 518, the SMF may transmit a path switch request acknowledgment message to the target MN.

In step 519, the target MN may transmit a UE context release message to the source MN.

In step 520 , the source MN may transmit a UE context release message to the source SN.

So far, a method for supporting reliable session transmission and a first handover method according to the present invention have been described. Using this method, transmission reliability can be secured by establishing two redundant PDU sessions in two base stations after handover, and UPFs close to the two base stations can be selected, respectively, in order to reduce transmission delay.

6 schematically shows a schematic diagram of another method for handing over a PDU session of duplicate session processing to another base station according to an embodiment of the present disclosure. Detailed descriptions of steps irrelevant to the present disclosure are omitted herein. As shown in FIG. 6 , the method may include the following steps.

In step 601, the source MN may transmit a handover request message to the target base station. Here, the target base station may be a gNB or an LTE base station gn-eNB connected to the 5G core network. In the source MN, the UE XnAP identity of the source SN, the identifier of the SN, and the context of the UE in the source SN may be included in the handover request message. The handover request message may be composed of an MCG configuration and an SCG configuration. The handover request message may include information on redundant PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using a redundant sequence number (RSN). The information on the duplicate PDU session handling may further indicate a relationship between two PDU sessions for duplicate handling. For example, two PDU sessions used for overlap handling may be notified to the target MN. The target MN may store information on duplicate PDU session processing.

For example, when the target base station cannot configure dual connectivity (DC), such as when there is no available secondary base station cell according to the UE's measurement report, there may be two processing methods performed by the target base station.

In the first method, the target base station does not need to allocate resources including radio resources and network resources to the second PDU session, and the second PDU session may not be established. The target base station may configure only resources for the first PDU session.

In the second method, the target base station may configure both the first PDU session and the second PDU session in the target base station. That is, two PDU sessions for duplication processing may not be configured with dual connectivity.

In step 602, the target base station may transmit a handover request acknowledgment message to the source MN. Corresponding to the first processing method in the target base station of step 601, the second PDU session in the target base station may be included in the list of PDU sessions for which resources are not identified. The message may include reasons for failure (eg, the reason that the second PDU session cannot be established or DC configuration is not supported). Corresponding to the second processing method in the target base station of step 601, the first PDU session and the second PDU session in the target base station may be included in the PDU session list for which resources are identified.

In step 603a, the source MN may transmit an SN release request message to the source SN.

In step 603b, the source SN may transmit an SN release request acknowledgment message to the source MN.

In step 604 , the source MN may send an RRC connection reconfiguration message to the UE.

In step 605, the terminal may be synchronized with the target base station.

In step 606, the terminal may transmit an RRC connection reconfiguration complete message to the target base station.

In step 607, the source SN may send an SN status transfer message to the source MN for the bearer terminated by the SCG using the RLC AM mode.

In step 607b, the source MN may transmit the SN status transmission message to the target base station.

In step 608 the source SN may pass the data to the source MN. The source MN may forward the data to the target base station.

In step 609, the target base station may transmit a path switch request message to the AMF.

In the target base station, the base station identifier of the base station to which the PDU is to be established or the cell identifier of the cell of the base station accessed by the UE may be included in the path switch request transmission. For example, when the first PDU session is established in the target base station, the identifier of the target base station or the cell identifier of the cell of the target base station to which the UE is accessed may be included in the path switch request transmission information of the first PDU session.

Corresponding to the first processing method in the target base station of step 601, in the target base station, the second PDU session that has not been established by the secondary base station may be included in the list of PDU sessions in which resource setup has failed. The list of PDU sessions in which resource establishment has failed may be composed of identities of PDU sessions and reasons for failure (eg, the reason that the second PDU session cannot be established or DC configuration is not supported). The SMF may determine whether to maintain the first PDU session in the redundant PDU session or release the first PDU session in the redundant PDU session according to the local policy.

Corresponding to the second processing method in the target base station in step 601, the second PDU session in the target base station may be included in the resource information list for the PDU session to be handed over in a path switch request message. . The resource information for the PDU sessions to be handed over may include identifiers of the PDU sessions. The resource information for the PDU sessions to be handed over includes information that the two PDU sessions are not configured with dual connectivity, information that the two PDU sessions have failed to configure with dual connectivity, or information that the second PDU session is not established in the secondary base station. may include The target base station may transmit the base station identifier of the base station in which the second PDU session is configured or the identifier of the primary cell of the base station to the SMF. The SMF may be implicitly notified through the base station identifier of the base station in which the second PDU session is configured or the primary cell identifier of the base station in which the second PDU session is not configured in the secondary base station or two overlapping PDUs. The SMF is two PDUs for overlapping processing according to the identifier of the received base station, which is the identifier of the primary cell of the base station in which the second PDU session is configured or received, and the identifier of the primary cell of the master base station or the identifier of the master base station. It can be seen that the sessions were not successfully configured with the DC. When the SMF is implicitly informed that the two PDU sessions were not successfully configured with dual connectivity, the target base station also determines the base station identifier of the base station with which the first PDU session is configured or the identifier of the primary cell of the corresponding base station ( Example: identifier of the target base station) may be transmitted to the SMF. Accordingly, the SMF is based on the base station identifier of the base station in which the first PDU session is configured or the identifier of the primary cell of the corresponding base station, and the base station identifier of the base station in which the second PDU session is configured or the base station identifier of the primary cell of the corresponding base station. It can be seen that the two PDU sessions for duplication processing were not successfully configured with dual connectivity. The SMF may determine whether to maintain the second PDU session or release the second PDU session according to the local policy. In this method, if the target base station does not receive the message to release the second PDU session, when the target base station can hand over the second PDU session to the secondary base station, the target base station performs an SN addition procedure to establish a second PDU session. The secondary base station may configure the second PDU session as a bearer terminated by the SN. The target base station may notify the SMF through the AMF that the second PDU session has been successfully configured or dual connectivity has been successfully configured in the secondary base station. The target base station may further inform the identifier of the secondary base station or the identifier of the secondary base station accessed by the UE through the AMF. In addition, the SMF may determine whether to reselect the UPF for the second PDU session using the identifier of the secondary base station or the identifier of the cell of the secondary base station. The identifier of the cell of the secondary base station may be the cell identifier of the primary cell of the secondary base station selected for the UE. In fact, the target base station to which the session has been successfully handed over is the base station serving the terminal, and for convenience of description of the method, the name of the target base station is used as it is.

In step 610, the AMF may transmit an update session management context request message to the SMF. The AMF may transmit the identifier of the base station or the cell identifier received from the target MN to the SMF. For each PDU session, when the SMF receives the identifier or cell identifier of the base station to which the PDU session is to be established, the SMF may select the UPF for the PDU session using the received identifier of the base station. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The message may include information on a tunnel allocated by a target base station to which a PDU session is to be established. If the establishment of the second PDU session fails, the SMF may not trigger the second PDU session establishment procedure in the target base station.

In step 611 , the SMF may transmit an N4 session modification request message to the UPF. The SMF may transmit the N4 session modification request message to the UPF (eg, UPF1) for the first PDU session and to the UPF (eg, UPF2) for the second PDU session for redundancy processing, respectively. When the UPF is reselected for a specific PDU session, the SMF may transmit an N4 session modification request message to the reselected UPF. The SMF may transmit the downlink tunnel information for the NG interface allocated by the target base station to the corresponding UPF for data transmission. In the case of a PDU session that the target base station has not established, the SMF may request the UPF to delete the corresponding downlink user plane tunnel information, and the UPF may delete the corresponding PDU session or mark the corresponding PDU session as inactive.

Upon receiving the N4 session modification request message, the UPF may transmit an N4 session modification response message to the SMF.

In step 612, the SMF may transmit an update session management context acknowledgment message to the AMF.

In step 613, the UPF may transmit data to the target base station. The UPF may transmit downlink data to the target base station according to the received downlink tunnel information allocated by the target base station.

In step 614, the SMF may transmit a path switch request acknowledgment message to the target base station.

In step 615, the target base station may transmit a UE context release message to the source MN.

In step 616 , the source MN may send a UE context release message to the source SN.

So far, a method for supporting reliable session transmission and a second handover method according to the present invention have been described. Using this method, if the target base station cannot configure DC during handover, resources are not allocated to the second PDU session, and thus resource waste and failure in redundant user plane configuration can be prevented.

7 schematically shows a schematic diagram of another session establishment method according to embodiments of the present disclosure. In the method of FIG. 3, the NG-RAN receives the information that the second PDU session will be established from the core network, but the NG-RAN cannot configure DC for the UE, or the redundant user plane during the handover corresponding to FIG. 6 When the target base station receives the information that this is established, but the target base station cannot establish DC for the UE, the base station or the target base station may store information that the second PDU session establishment is necessary, and the base station configures DC for the UE If possible, the base station may establish a second PDU session in the secondary base station. Detailed descriptions of steps irrelevant to the present disclosure are omitted herein. 7 , the method may include the following steps.

In step 701 , the MN may transmit an SN addition request message to the SN. The message may include information on duplicate PDU session handling. The information on the redundant PDU session handling may indicate whether the PDU session is a first PDU session or a second PDU session using RSN. The information on the duplicate PDU session handling may indicate an association relationship between two PDU sessions for duplicate handling, for example, may inform the SN of two PDU sessions used for duplicate handling. The SN stores information on duplicate PDU session processing, and the SN may establish a PDU session with the bearer terminated by the SN. The SN may not hand over the bearer to the bearer terminated by the MN.

In step 702, the SN may transmit an SN addition request acknowledgment message to the MN.

In step 703, the MN may transmit an RRC connection reconfiguration message to the terminal.

If the bearer using the SCG radio resource is established in step 704, the terminal may be synchronized to the SN.

In step 705, the UE may transmit an RRC connection reconfiguration complete message to the MN.

After the RRC connection reconfiguration is successful in step 706 , the MN may transmit an SN reconfiguration complete message to the SN.

In step 707, the MN may transmit a PDU session setup completion indication message to the AMF. In the MN, the PDU session identity of the second PDU session and information on the downlink tunnel allocated by the SN may be included in the PDU session establishment completion indication message. In the MN, the base station identifier of the base station to which the PDU is to be configured or the cell identifier of the cell to which the UE is connected may be included in the PDU session establishment completion indication message. For example, when the second PDU session is to be established in the SN, the identifier of the SN assigned to the UE in the SN or the cell identifier of the primary cell may be included in the PDU session establishment completion indication message corresponding to the second PDU session. .

In step 708 , the AMF may transmit an update session management context request message to the SMF. The AMF may transmit the identifier of the base station or the cell identifier received from the MN to the SMF. The AMF may transmit the received session management information to the SMF. For each PDU session, when the SMF receives the identifier or cell identifier of the base station to which the PDU session is to be established, the SMF may select the UPF for the PDU session using the received identifier of the base station. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

When the SMF receives the identifier of the secondary base station or the identifier of the primary cell of the secondary base station, the SMF may select or reselect the UPF for the second PDU session. The ID of the secondary base station may be used as an input for UPF selection or reselection. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The message may include information of the tunnel allocated by the MN for the PDU session to be established.

In step 709, the SMF may transmit an N4 session modification request message to the UPF. The SMF may transmit an N4 session modification request message to the UPF for the second PDU session for duplication processing. When the UPF is reselected for a specific PDU session, the SMF may transmit an N4 session modification request message to the reselected UPF. The SMF may transmit information of a downlink tunnel for an NG interface allocated by the MN to the corresponding UPF for data transmission.

Upon receiving the N4 session modification request message, the UPF may transmit an N4 session modification response message to the SMF.

In step 710, the SMF may transmit an update session management context acknowledgment message to the AMF.

In step 711, the UPF may transmit downlink data to the NG-RAN. The UPF may transmit downlink data to the NG-RAN according to the received information of the downlink tunnel allocated by the NG-RAN. In the case of the bearer terminated by the SN, the corresponding UPF may transmit downlink data to the SN.

In step 712, the SMF may transmit a PDU session completion indication acknowledgment message to the target MN.

So far, a method for supporting reliable session transmission and a method for establishing a second PDU session according to the present invention have been described. In this way, when the MN cannot configure a duplicate PDU session in a specific secondary base station during initial PDU session establishment or handover, the MN may store information of the second PDU session. When the DC becomes available, the MN configures the DC and informs the information (via AMF) that the second PDU session will be established to the SMF, and also the identifier of the secondary base station or the cell identifier of the primary cell of the secondary base station to the SMF. The SMF may select the UPF for the second PDU session in consideration of the identifier of the secondary base station or the identity of the primary cell of the secondary base station to ensure transmission reliability and reduce transmission delay.

8 schematically shows a schematic diagram of another session establishment method according to an embodiment of the present disclosure. Detailed descriptions of steps irrelevant to the present disclosure are omitted herein. As shown in FIG. 8 , the method may include the following steps.

In step 801, the terminal may transmit a PDU session establishment request message to the AMF. The terminal may transmit a PDU session establishment request message to the base station through the RRC message. The RRC message may include information indicating that a duplicate PDU session will be established or information indicating that a second PDU session will be established.

The base station connected by the UE (eg, NG-RAN Node 1) knows that the second PDU session will be established, but the base station cannot configure DC for the UE, for example according to the UE's measurement report to discover. In this case, the base station can set the information that the DC cannot be used for the NGAP message for transmitting the non-access stratum message, the PDU session setup request message, or the current second PDU session. It can be transmitted to the AMF including the information that it is not there.

For example, if the base station can configure DC for the UE according to the UE's measurement report, the identifier of the secondary base station or the cell identifier in which the PDU session can be established in the base station Non-access layer message PDU session establishment request message The NGAP message for transmission may include information on the secondary base station. The AMF may transmit an identifier of a possible secondary base station or an identifier of a cell of the secondary base station to the SMF in step 802 . The SMF may select the UPF for the secondary PDU session service in consideration of the identifier of the secondary base station. or the cell identifier of the secondary base station. For example, in step 804 , the UPF may be selected in consideration of the identifier of the secondary base station that may be configured for the UE. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier.

The base station may transmit a PDU session establishment request message to the AMF through an NGAP message.

The PDU session establishment request message may include a redundant sequence number (RSN). RSN may indicate redundant processing. The value of RSN may indicate whether to establish a first PDU session or a second PDU session.

In step 802 , the AMF may transmit a session creation management context request message to the SMF. When the AMF receives information indicating that the DC is unavailable from the NG-RAN or receives information indicating that the current second PDU session cannot be established, the AMF transmits information indicating that the DC cannot be used or establishes a second PDU session. Information indicating that it cannot be used may be transmitted to the SMF. The SMF may store information of the second PDU session to be set.

In step 803, the SMF may transmit a session creation management context response message to the AMF.

In the method according to the present disclosure, the SMF may trigger steps 804 to 813 . As another method of the present disclosure, steps 804 to 813 may not be triggered.

In step 804, the SMF may select a UPF. The SMF may select the UPF in consideration of a base station identity or a cell identifier received from the AMF. The base station identifier received by the SMF may be an identifier of a master base station or an identifier of a secondary base station. The secondary base station may also be referred to as a second base station. When the SMF receives the identifier of the cell of the base station, the SMF may obtain the base station identifier according to the cell identifier. The SMF may know that the PDU session is used for redundancy processing based on RSN or data network name (DNN) or single network slice selection assistance information (S-NSSAI) received from the UE and network configuration. In addition, it may be known whether the PDU session is the first PDU session or the second PDU session. The SMF may select the UPF in consideration of the information that the PDU session is the first PDU session for duplication processing and the received base station identifier or cell identifier. The SMF may select the UPF using information that the first PDU session or the second PDU session is established together with other information.

In step 805 , the SMF may transmit an N4 session setup request message or an N4 session modification request message to the selected UPF. If the request is an initial request, the SMF may initiate an N4 session establishment procedure for the selected UPF. Otherwise, the SMF may initiate the N4 session modification procedure for the selected UPF.

In step 806 , the UPF may transmit an N4 session setup response or an N4 session modification response message to the SMF.

In step 807, the SMF may transmit an N1N2 message transmission message to the AMF. The message may include a PDU session ID (PDU session ID), N2 session management information (N2 SM information), and an N1 session container (N1 session container).

In step 808, the AMF may transmit a PDU session setup request message to the NG-RAN node 1. The message may include information on duplicate PDU session handling. The information on the duplicate PDU session processing may indicate whether the PDU session is a first PDU session or a second PDU session using RSN. The information on the duplicate PDU session processing may also indicate an association relationship between two PDU sessions for duplicate handling, for example, to inform NG-RAN node 1 that two PDU sessions are used for duplicate handling.

The NG-RAN node 1 may know that the PDU session to be set according to the received PDU session setup request message is used for duplication processing (handling). The NG-RAN node 1 may also know whether the PDU session to be established is the first PDU session or the second PDU session, or the NG-RAN node 1 may know which two PDU sessions are used for duplication processing. When the PDU session to be set is used for redundancy processing and the PDU session to be set is the second PDU session, the NG-RAN node 1 may establish the second PDU session to a base station different from the first PDU session. However, when the NR-RAN node 1 cannot configure a DC for the UE, the NG-RAN node 1 may store information of the second PDU session to be established.

For example, if the NG-RAN Node 1 cannot configure dual connectivity (DC) for the UE, there are two processing methods performed in the NG-RAN Node 1 according to the UE's measurement report, details are in the steps (311), which will not be described again hereinafter.

In step 809, the NG-RAN node 1 may transmit a PDU session setup acknowledgment message to the AMF.

In step 810, the AMF may transmit an update session management context request message to the SMF.

In step 811, the SMF may transmit an N4 session modification request message to the UPF. In the case of a PDU session that the NG-RAN has not established, the SMF may request the UPF to delete the corresponding downlink user plane tunnel information, and the UPF may delete the corresponding PDU session or mark the corresponding PDU session as inactive.

In step 812 , the UPF may transmit an N4 session modification response message to the SMF.

In step 813, the SMF may transmit an update session management context acknowledgment message to the AMF.

The NG-RAN node 1 monitors information on whether DC is available, and when the DC becomes available, the NG-RAN configures the DC and may perform the process described in FIG. 7 .

A system supporting reliable session transmission according to the present disclosure is shown in FIG. 9 . A redundant user plane is established for the UE, two UPFs are connected to two different centralized unit-user plane entities (CU-UPs) of the same base station. Two CU-UPs are each connected Data of two PDU sessions may be transmitted to the UE through each DU. Instead of transmitting data of two overlapping PDU sessions to the terminal through two base stations compared to the prior art, data of two overlapping PDU sessions may be transmitted to the terminal through two CU-UPs and two DUs of the same base station.

10 is a schematic flowchart of a session establishment method according to an embodiment of the present disclosure. As shown in FIG. 10 , the method may include the following steps.

In step S1010, a message for creating a session management context may be received.

In some examples, the message may be a session creation management context request message received from AMF, but the technical solution according to an embodiment of the present invention is not limited to a specific message/specific name of a message.

In step S1020, in response to the message for creating a session management context, a UPF for duplicate session processing may be selected.

In step S1030, a PDU (Packet Data Unit) session corresponding to the UPF may be established.

In some embodiments, selecting a UPF for duplicate session handling in response to a message to create a session management context may include:

The session management context may determine whether the session for which the session management context should be created is a duplicate session and determine whether the duplicate session is a first duplicate session or a second duplicate session based on at least one of the following.

Information related to a duplicate session included in a message for creating a session management context (eg, a PDU session establishment request message); and

data network name (DNN) or single network slice selection support information (S-NSSAI) and operator's network configuration;

selecting, based on the determination, a UPF for duplicate session processing according to an identifier of a serving base station of a user equipment (UE).

For example, in the case of the first overlapping session and the second overlapping session, the UPF may be selected according to the identifier of the master base station (eg, the serving base station of the UE). Of course, other implementations are possible, and the embodiment of the present invention is not limited thereto.

For example, the selection of UPF may be implemented at other times. In some embodiments, after the UPF is selected for the first redundant session and the second redundant session, the reselection may also be performed later at an appropriate time. Based on this, the method may further comprise:

The first base station identifier of the base station with which the first overlapping session is to be established or the cell identifier of the cell of the first base station accessed by the UE and the second base station identity of the base station with the second overlapping session are established or accessed by the UE. It is the cell identifier of the cell of the second base station, and the UPF for the first overlapping session may be selected according to the first base station identifier, and the UPF for the second overlapping session may be selected according to the following. When the SMF receives the cell identifier of the base station, the SMF may obtain the base station identifier according to the cell identifier. Alternatively, the method may further comprise:

Receiving a base station identifier of a base station to which a second overlapping session is to be established, and selecting a UPF for the second overlapping session according to the base station identifier or cell identifier. Here, it is possible to select a UPF closest to the base station to which the session is to be established according to the selection criterion. The UPF may be selected according to other distance-related conditions or a combination of distance-related conditions and other selection criteria.

11 illustrates a schematic flowchart of another session establishment method according to an embodiment of the present disclosure. This method may be performed at a first base station (eg, a master base station/serving base station of the UE) that establishes a first redundancy session for redundancy processing. 11 , the method may include the following steps.

In step S1110, a message for establishing a second redundant session for duplication processing may be received.

The message may be a PDU session establishment request message received from the AMF, but the technical solution according to an embodiment of the present invention is not limited to a specific message/specific name of a message.

In step S1120, in response to the message, it may be determined whether to add a second base station for processing the second redundant session.

In step S1130 , the second overlapping session may be configured to be processed by the second base station when it is determined to add the second base station.

In some embodiments, in response to the message, determining whether to add a second base station to handle the second redundant session may include:

determining whether the first base station supports dual connectivity for the first redundant session and the second redundant session; and

if the first base station supports dual connectivity, determining to add a second base station to configure a second redundant session to be processed by the second base station; Otherwise, it may decide not to add the second base station.

The first base station may store information necessary to establish a second redundant session when the first base station does not support dual connectivity. If it is determined that the first base station can support dual connectivity, it may decide to add the second base station using the stored information to configure the second redundant session to be handled by the second base station.

In the above embodiment, configuring the second redundant session to be processed by the second base station may include:

requesting the second base station to establish a second redundant session with the second base station;

receiving, from a second base station, an acknowledgment message for accepting establishment of a second redundant session;

receiving a resource configured by the user equipment for a second redundant session; and

transmitting, at the second base station, a resource configured to establish a second redundant session to the second base station.

Alternatively, configuring the second redundant session to be processed by the second base station may include:

establishing a second redundant session with the first base station;

requesting the second base station to establish a second redundant session with the second base station;

receiving, from a second base station, an acknowledgment message for accepting establishment of a second redundant session;

receiving a resource configured by the user equipment for a second redundant session; and

Handing over the second redundant session to the second base station using the configured resources.

12 is a schematic block diagram of an SMF for session establishment according to an embodiment of the present disclosure. 12 , the SMF may include a message receiving unit 1210 , a UPF selection unit 1220 , and a session setup unit 1230 . . The message receiving unit 1210 may be configured to receive a message for creating a session management context. The UPF selection unit 1220 may be configured to select a UPF for duplicate session handling in response to the message for creating a session management context. The session establishment unit 1230 may be configured to establish a packet data unit (PDU) session corresponding to the UPF.

In some examples, the received message may be a session creation management context request message received from AMF, but the technical solution according to an embodiment of the present invention is not limited to a specific message/specific name of a message.

In some examples, UPF selection unit 1220 may be configured as follows:

It may be determined whether the session for which the session management context is to be created is a duplicate session, and whether the duplicate session is a first duplicate session or a second duplicate session based on at least one of the following.

information related to duplicate sessions included in a message for creating a session management context (eg, a PDU session establishment request message); and

data network name (DNN) or single network slice selection assistance information (S-NSSAI) and operator's network configuration; and

Based on the determination, the UPF for duplicate session processing may be selected according to the identifier of the serving base station of the user equipment (UE) or the cell identifier of the cell of the base station accessed by the UE.

For example, for the first redundant session and the second redundant session, the UPF may be selected according to the identifier of the master base station (eg, the serving base station of the UE). Of course, other implementations are possible, and the embodiment of the present invention is not limited thereto.

For example, the selection of UPF may be implemented at different times. In some embodiments, after the UPF is selected for the first redundant session and the second redundant session, the reselection may also be performed later at an appropriate time. Based on this, the UPF selection unit 1220 may be further configured to: select the first base station identifier of the base station with which the first redundant session is to be established or the cell identifier of the cell of the first base station accessed by the UE. may be configured to receive. and select the UPF for the first overlapping session according to the second base station identifier of the base station with which the second overlapping session is to be established or the cell identifier of the cell of the second base station accessed by the UE, the first base station. In addition, the UPF for the second overlapping session may be selected according to the second base station identifier. When the SMF receives the cell identification information of the base station, the SMF may obtain the base station identification information according to the cell identification information. Alternatively, the UPF selection unit 1220 may further configure the following: receive a base station identifier of a base station with which the second redundant session is to be established, and select the UPF for the second redundant session according to the base station identifier or the cell base station. You can choose. Here, it is possible to select a UPF closest to the base station to which the session is to be established according to the selection criterion. When the SMF receives the cell identification information of the base station, the SMF may obtain the base station identification information according to the cell identification information. The UPF may be selected according to other distance-related conditions or a combination of distance-related conditions and other selection criteria.

13 is a schematic block diagram of a base station for session establishment according to an embodiment of the present disclosure. As shown in FIG. 13 , the base station includes a message receiving unit 1310 , a base station addition determination unit 1320 and a second redundant session configuration unit. 1330 may be included. The message receiving unit 1310 may be configured to receive a message for establishing a second duplicate session for duplicate processing. The base station addition determining unit 1320 may be configured to determine whether to add the second base station to handle the second redundant session in response to the message. The second redundant session configuration unit 1330 may be configured to configure a second redundant session to be processed by the second base station when it is determined to add the second base station.

The message may be a PDU session establishment request message received from the AMF, but the technical solution according to an embodiment of the present invention is not limited to a specific message/specific name of a message.

In some embodiments, the base station addition determining unit 1320 may be configured as follows:

determine whether the first base station supports dual connectivity for the first redundant session and the second redundant session; and

if the first base station supports dual connectivity, decide to add a second base station to configure a second redundant session to be processed by the second base station; Otherwise, it may be decided not to add the second base station.

The first base station may store information necessary to establish a second redundant session when the first base station does not support dual connectivity. If it is determined that the first base station can support dual connectivity, it may decide to add the second base station using the stored information to configure the second redundant session to be handled by the second base station.

In the above embodiments, the second redundant session configuration unit 1330 may be configured as follows:

request the second base station to establish a second redundant session with the second base station;

receiving an acknowledgment message from the second base station accepting establishment of a second redundant session;

receive a resource configured by the user equipment for the second redundant session; and

The configured resource may be transmitted to the second base station to establish a second redundant session in the second base station.

Alternatively, the second redundant session configuration unit 1330 may be configured as follows.

establishing a second redundant session with the first base station;

requesting the second base station to establish a second redundant session with the second base station;

receive from the second base station an acknowledgment message accepting establishment of a second redundant session;

receive a resource configured by the user equipment for the second redundant session; and

The second redundant session may be handed over to the second base station using the configured resource.

In the above embodiment, the first base station may operate as a master base station for redundant session processing. In some embodiments, the main control function may be handed over from another base station (eg, a third base station below) acting as a master base station for some other overlapping session processing. 14 is a schematic flowchart of a method for handing over a master base station for redundant session processing according to an embodiment of the present disclosure. 14 , the method may include the following steps.

In step S1410, a handover request message transmitted by the third base station may be received, and the handover request message may request the third base station to hand over a main control function for redundant session processing to the first base station.

In step S1420, a connection to the UE corresponding to the duplicate session processing may be established based on the handover request message.

In step S1430, a path switch request message may be transmitted to a mobility management control entity.

In some embodiments, the method may further include, in response to the handover request message, adding a fourth base station for handling the second redundant session in the redundant session of the third base station.

In some embodiments, the first base station may also hand over the main control function for redundant session processing to another base station. In this case, the first base station may transmit a handover request message to another base station and release the resource after receiving a confirmation message from the other base station.

15 is a schematic block diagram of an apparatus for handing over a master base station for redundant session processing according to an embodiment of the present disclosure. The apparatus may be the first base station described above. 15 , the device may include a message receiving unit 1510 , a connection setup unit 1520 and a message transmitting unit 1530 . . The message receiving unit 1510 is configured to receive a handover request message sent by the third base station, wherein the handover request message is configured to hand over a main control function for redundant session processing of the third base station to the first base station. you can request The connection establishment unit 1520 may be configured to establish a connection to a user equipment (UE) corresponding to the duplicate session processing based on the handover request message. The message sending unit 1530 may be configured to send a route switch request message to the mobility management control entity.

In some embodiments, the apparatus further adds a base station addition unit 1540, configured to add a fourth base station for handling the second redundant session in the redundant session of the third base station in response to the handover request message may include

In some embodiments, the first base station may also hand over the main control function for redundant session processing to another base station. In this case, the first base station may transmit a handover request message to another base station and release the resource after receiving a confirmation message from the other base station.

16 schematically illustrates a block diagram of a computing system that may be used to implement the SMF 1200 of the present disclosure or the base station 1300 of the present disclosure according to an embodiment of the present disclosure.

As shown in FIG. 16 , the computing system 1600 includes a processor 1610 , a computer readable storage medium 1620 , an output interface 1630 , and an input interface ( input interface) 1640 . The computing system 1600 may perform the methods described above with reference to FIGS. 10 , 11 , or 14 .

Specifically, the processor 1610 may include, for example, a general purpose microprocessor, an instruction set processor and/or an associated chipset and/or a dedicated microprocessor (eg, an application specific integrated circuit (ASIC)). . The processor 1610 may further include onboard memory for caching purposes. The processor 1610 may be a single processing unit or a plurality of processing units for performing different operations of the method flow described with reference to FIGS. 10 , 11 , or 14 .

Computer-readable storage medium 1620 can be, for example, any medium that can contain, store, communicate, propagate, or transmit instructions. For example, a readable storage medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, apparatus, or propagation medium. Specific examples of readable storage media include magnetic storage devices such as hard disk drives (HDDs for short); optical storage devices such as compact disc read-only memory (CD-ROM for short); memory such as random access memory (RAM for short) or flash memory; and/or a wired/wireless communication link.

The computer-readable storage medium 1620 may include code/records that, when executed by the processor 1610 , cause the processor 1610 to perform the method flows described above with reference to, for example, FIGS. 10 , 11 or 14 and variations thereof. may include a computer program 1621, which may include computer-executable instructions.

Computer program 1621 may be configured to have computer program code including, for example, computer program modules. For example, in an exemplary embodiment, the code of the computer program 1621 may include one or more program modules including, for example, a module 1621A, a module 1621B, ... The number of modules is not fixed, and appropriate program modules or combinations of program modules may be used by those skilled in the art according to actual conditions. This combination of program modules, when executed by the processor 1610 , causes the processor 1610 to perform the method flow described above with reference to, for example, FIGS. 1 to 3 and variations thereof.

According to embodiments of the present disclosure, the processor 1610 may use the output interface 1630 and the input interface 1640 to perform the method flow and any modifications described above with reference to FIGS. 10 , 11 , or 14 .

So far, a method for supporting reliable session transmission, a session establishment method, and a handover method according to the present invention have been described. Using this method, two overlapping PDU sessions can be established for each of the two base stations in order to secure service transmission reliability and reduce transmission delay using the UPF selection method according to the present invention. At the same time, a handover method capable of ensuring low delay and high reliability of service transmission after the handover is completed is provided.

Those skilled in the art will understand that the above-described method is merely exemplary. The method according to the present disclosure is not limited to the steps and sequences described above. The above-described base station and user equipment may include more modules, for example, may further include modules available in the base station or the UE, which may or may be developed in the future. The various identities described above are merely exemplary and not restrictive, and the present disclosure is not limited to specific example names of identifiers. Many variations and modifications may be made by those skilled in the art in light of the teachings of the described embodiments.

Those skilled in the art may understand that embodiments of the present application include apparatuses related to performing one or more operations described in the present application. Such devices may include devices specifically designed and manufactured for the necessary purposes or known in general purpose computers. Such devices have stored therein a computer program that is selectively activated or reconfigured. Such a computer program may be stored in a device (eg, computer) readable medium or any tangible medium suitable for storing electronic instructions, and includes, but is not limited to, any type of disk (including floppy). can be connected to each. disk, hard disk, optical disk, compact disk read-only memory (CD-ROM) and magneto-optical disk), read only memory (ROM), random access memory (RAM), erasable programmable read-only memory (EPROM), electrical Erasable programmable read-only memory (EEPROM), flash memory, magnetic card or light card. That is, readable media can include any medium used by an apparatus (eg, a computer) to store or transmit information in a readable form.

It can be understood by those skilled in the art that each block in the structural diagram and/or block diagram and/or flowchart and combinations thereof may be implemented by computer program instructions. Those skilled in the art will understand that these computer program instructions may be implemented by a processor of a general purpose computer, a specialized computer, or other programmable data processing method. The structural diagrams and/or block diagrams and/or flow diagrams disclosed herein may be executed by a processor of a computer or other programmable data processing method.

It will be understood by those skilled in the art that the steps, measurements, and solutions in the various acts, methods, and flows discussed in this disclosure may be substituted, modified, combined, or deleted. In addition, other steps, measurements, and solutions in the various acts, methods, and flows discussed in this disclosure may be substituted, modified, rearranged, disassembled, combined, or deleted. In addition, the steps, actions and solutions in the various acts, methods, and flows in the related art and discussed herein may be substituted, modified, rearranged, disassembled, combined, or deleted.

The above description is only some embodiments of the present disclosure, and those skilled in the art may also make several improvements and modifications without departing from the principles of the present application. Such improvements and modifications are deemed to fall within the protection scope of the disclosure.

Claims (15)

A method for setting up a session in a wireless communication system, comprising:
Receiving a message for creating a session management context (session management context);
selecting a user plane functional entity (UPF) for redundant session processing in response to the message for creating the session management context; and
and setting a packet data unit (PDU) corresponding to the UPF.
The method according to claim 1,
In response to the message for creating the session management context, the process of selecting a UPF for duplicate session processing includes:
The process of determining, based on at least one, whether the session for which the session management context needs to be created is a duplicate session, and whether the duplicate session is a first duplicate session or a second duplicate session;
information related to the duplicate session included in the message for creating the session management context; and
data network name (DNN) or single network slice selection assistance information (S-NSSAI) and network configuration of the operator;
and determining the UPF for duplicate session processing according to an identity of a serving base station of a user equipment (UE) based on the determination.
3. The method according to claim 2,
Receiving a first base station identifier of the base station in which the first redundant session is established and a second base station identifier of the base station in which the second redundant session is established;
selecting a UPF for the second overlapping session according to the second base station identifier and selecting a UPF for the first overlapping session according to the first base station identifier; or
Receiving the base station identifier of the base station to which the second overlapping session is established;
The method further comprising the step of selecting a UPF for the second overlapping session according to the base station identifier.
In a wireless communication system, a method for establishing a session comprises:
A first base station for establishing a first redundant session for redundant handling, the method comprising:
Receiving a message for establishing a second redundant session for redundant handling,
determining whether to add a second base station for processing the second redundant session in response to the message; and
If the second base station is determined to be added, the method of establishing the second overlapping session processed by the second base station.
5. The method according to claim 4,
In response to the message, determining whether to add a second base station for processing the second redundant session includes:
determining whether the base station supports dual connectivity for the second redundant session and the first redundant session; and
If the base station supports dual connectivity, determining the addition of the second base station for establishing the second redundant session processed by the second base station;
otherwise, determining not to add the second base station.
6. The method of claim 5,
storing information necessary for establishing the second redundant session when the first base station does not support dual connectivity; and
When it is determined that the first base station is capable of supporting dual connectivity, determining the addition of the second base station by using the stored information to establish the second redundant session processed by the second base station How to include.
7. The method according to claim 4 to 6,
The process of establishing the second redundant session processed by the second base station includes:
requesting the second base station for establishing the second redundant session in the second base station;
receiving an acknowledgment message for acknowledging establishment of the second redundant session from the second base station;
receiving resources for the second redundant session established by user equipment (UE); and
and transmitting the configured resources to the second base station for establishing the second redundant session with the second base station.
The method according to any one of claims 4 to 6, wherein the step of establishing the second redundant session processed by the second base station comprises:
establishing the second redundant session with the first base station;
requesting the second base station to establish the second redundant session to the second base station;
receiving an acknowledgment message for acknowledging establishment of the second redundant session from the second base station;
receiving resources for the second redundant session established by user equipment (UE); and
and handing over the second redundant session to the second base station using the configured resources.
In a wireless communication system, a method for handing over to a master base station for redundant session processing includes:
A process of receiving a handover request message transmitted by a third base station, wherein the handover request message requests a first base station to handover a main control function for redundant session processing of the third base station; ,
establishing a connection to a user equipment (UE) corresponding to the duplicate session processing based on the handover request message; and
A method comprising transmitting a path switch request message to a mobility management control entity.
10. The method of claim 9,
In response to the handover request message, the method further comprising the step of adding a fourth base station for processing a second duplicate session among the duplicate sessions of the third base station.
A session management functional entity (SMF) is:
processing unit; and
a storage unit storing machine readable instructions which, when executed by the processing unit, configure the processing unit to perform the method according to any one of claims 1 to 3 SMF.
The base station is:
processing unit; and
A storage unit storing machine readable instructions that, when executed by the processing unit, configure the processing unit to perform the method according to any one of claims 4 to 8 or 9 to 10. A base station comprising a (storage unit).
A session management functional entity (SMF) in a wireless communication system is:
a message receiving unit, configured to receive a message for creating a session management context;
a UPF selection unit configured to select a user plane functional entity (UPF) for redundant session processing in response to the message for creating the session management context; and
and a session setup unit configured to establish a packet data unit (PDU) session corresponding to the UPF.
In a wireless communication system, a base station:
a message receiving unit, configured to receive a message for establishing a second redundant session for redundant handling;
a base station addition determination unit, configured to, in response to the message, determine whether to add a second base station for processing the second overlapping session; and
and a second redundant session configuration unit, configured to establish the second redundant session to be processed by the second base station if the second base station decides to add.
In a wireless communication system, a base station:
a message receiving unit, configured to receive a handover request message sent by a third base station, wherein the handover request message is a main control function for duplicate session processing of the third base station ( requesting handover of the main control function) to the first base station;
a connection setup unit, configured to establish a connection to a user equipment (UE) corresponding to the duplicate session processing based on the handover request message; and
A base station comprising a message transmitting unit configured to transmit a path switch request message to a mobility management control entity.

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