WO2022099453A1

WO2022099453A1 - Methods, entities, and computer readable media for ulcl insertion

Info

Publication number: WO2022099453A1
Application number: PCT/CN2020/127784
Authority: WO
Inventors: Chunbo Wang; Jan Backman
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ); Chunbo Wang
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2022-05-19

Abstract

Methods, entities, and computer readable media for ULCL insertion. The method at a second control plane entity that supports selection of a first user plane entity and a ULCL function entity includes: performing a process of inserting a ULCL function entity during a connection establishment.

Description

METHODS, ENTITIES, AND COMPUTER READABLE MEDIA FOR ULCL INSERTION

TECHNICAL FIELD

The present disclosure generally relates to the technical field of communication technologies, and particularly to methods, entities, and computer readable media for Uplink Classifier (ULCL) insertion in Evolved Packet Core (EPC) .

BACKGROUND

This section is intended to provide a background to the various embodiments of the technology described in this disclosure. The description in this section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and/or claims of this disclosure and is not admitted to be prior art by the mere inclusion in this section.

3GPP Releases 15 and 16 specify ULCL for 5G core network. The ULCL function provides multiple Packet Data Unit (PDU) Session anchors (PSAs) in the data path of a PDU session. The UL traffic is classified by ULCL and forwarded to different anchor User plane Functions (UPFs) based on the traffic forwarding rules provided by the Session Management Function (SMF) . Such functions provide edge computing for the terminals, e.g. the vehicles, so as to route the traffic matching the local access through the local Data Network (DN) .

FIG. 1 (corresponding to Figure 5.6.4.2-1 of 3GPP TS23.501 v16.6.0, and 3GPP TS23.501 v16.6.0 is incorporated herein by reference in its entirety) schematically illustrates a User plane Architecture for the ULCL, in which insertion of an ULCL PSA in a data path of a PDU Session is depicted.

As shown in FIG. 1, the SMF may decide to insert a ULCL PSA in the data path of a PDU Session during or after the PDU Session Establishment, or to remove a ULCL PSA from the data path of a PDU Session (e.g., due to application service termination) . The SMF may include more than one UPF supporting the UL CL functionality in the data path of a PDU Session.

In addition, due to UE mobility, the network may need to relocate a UPF acting as ULCL and establish a new PSA for access to the local DN. The source to target ULCL and PSA UPF relocation procedure is schematically illustrated in FIG. 2 (corresponding to Figure 4.3.5.7-1 of 3GPP TS23.502 v16.6.0, and 3GPP TS23.502 v16.6.0 is incorporated herein by reference in its entirety) .

As shown in FIG. 2, the UE has an established PDU Session with a UPF including the PDU Session Anchor (Remote UPF) . The PDU Session user plane involves at least the Source (R) AN, Source Branching Point or Source UL CL, local Source UPF (PSA2) and the Remote UPF (PDU Session Anchor, PSA1) , where Source Branching Point or Source UL CL and PSA2 can be co-located.

1. At some point, the SMF decides to change the Branching Point or the ULCL due to UE mobility.

2. The SMF selects a local Target UPF (PSA3) and using N4 establishes the local Target UPF for the PDU Session. In the case of IPv6 multi-homing PDU Session, the SMF also allocates a new IPv6 prefix corresponding to PSA3, and if the PCF has subscribed to the IP allocation/release event, the SMF performs the Session Management Policy Modification procedure as defined in clause 4.16.5 of 3GPP TS23.502 v16.6.0 to provide the new allocated IPv6 prefix to the PCF.

The SMF may send an earlier notification to the Application Function (AF) after PSA3 is selected. If the runtime coordination between 5G Core (5GC) and AF is enabled based on local configuration as specified in clause 4.3.6.3 of 3GPP TS23.502 v16.6.0, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF waits for a notification response from the AF before configuring the PSA3. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure.

3. The SMF selects a UPF and using N4 establishes the Target Branching Point or Target ULCL for the PDU Session. SMF provides the necessary uplink forwarding rules towards the PSA3 and PSA1 including the Tunnel Info for each UPF. If session continuity upon ULCL relocation is used, the SMF also uses N4 to establish an N9 forwarding tunnel between the Source ULCL and Target ULCL, including the Tunnel Info for each UPF. In addition, the AN Tunnel Info to target (R) AN is provided for downlink forwarding. In the case of ULCL, the SMF provides traffic filters indicating what traffic shall be forwarded towards PSA3, PSA1 and Source ULCL, respectively. In the case of IPv6 multi-homing, the SMF also provides traffic filters for the IPv6 prefixes corresponding to PSA3 and PSA1 indicating what traffic shall be forwarded towards PSA3 and PSA1 respectively. Target Branching Point or Target ULCL provides the CN Tunnel Info for downlink traffic.

NOTE 1: If the Target Branching Point or Target ULCL and the PSA3 are co-located in a single UPF then steps 2 and 3 can be merged.

NOTE 2: When session continuity upon ULCL relocation is used, the downlink traffic at this point goes through Source ULCL, Target ULCL and Target (R) AN.

4. The SMF updates the PSA1 via N4. It provides the PDU Session CN Tunnel Info for the downlink traffic.

5. The SMF updates the PSA3. It provides the CN Tunnel Info for downlink traffic.

NOTE 3: If the Target Branching Point or the Target ULCL and the PSA3 are co-located in a single UPF then step 5 is not needed.

6. In the case of PDU session with ULCL, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure and remove the Target Branching Point or Target ULCL and PSA3.

The SMF updates (R) AN via N2 SM information over N11. It provides the new CN Tunnel Info corresponding to the Target Branching Point or the Target ULCL. If there is an existing UPF between the Target (R) AN and Target Branching Point or Target ULCL, the SMF updates the existing UPF via N4 instead of updating the (R) AN.

NOTE 4: When session continuity upon ULCL relocation is used, the uplink traffic destined to PSA2 at this point goes through Target (R) AN, Target ULCL and Source ULCL.

7. In the case of IPv6 multi-homing PDU Session, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure.

In the case of IPv6 multi-homing, the SMF notifies the UE of the availability of the new IP prefix @PSA3. This is performed using an IPv6 Router Advertisement message. Also, the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message as described in clause 5.8.2.2.2 of 3GPP TS23.501 v16.6.0.

8. In the case of IPv6 multi-homing, the SMF may re-configure the UE for the original IP prefix @PSA1, i.e. SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message as described in clause 5.8.2.2.2 of 3GPP TS23.501 v16.6.0.

9. The SMF sends a Late Notification to the AF indicating a change of DNAI as described in clause 4.3.6.3 of 3GPP TS23.502 v16.6.0. In cases where target local DN is associated with another AF instance, SMF also sends notification to target AF as described in 4.3.6.3 and cancels any future notification message to source AF as it is no longer involved.

NOTE 5: The message can include routing information to the application located in the target local DN. Alternatively the routing information to the application located in the target local DN can be determined by the AF based on the new DNAI, in which case the AF can invoke the AF triggered influence on traffic routing procedure targeting single UE as described in clause 4.3.6.4 of 3GPP TS23.502 v16.6.0, which assists the SMF in generation of the routing rule on the Target ULCL towards PSA3 (i.e. towards the application located in the target local DN) . It is up to network configuration whether the routing information to the application located in the target local DN is configured in the SMF or in the AF.

NOTE 6: When session continuity upon ULCL relocation is used the AF can also trigger mechanisms that are out of the scope of this specification (e.g. IP-level or HTTP-level redirection) by which the traffic is redirected towards the application in the target local DN. Based on this redirection the UE starts using a new destination IP address which leads the Target ULCL to force the traffic towards PSA3.

10. When session continuity upon ULCL relocation is used, detection of no active traffic over the N9 forwarding tunnel is performed during a preconfigured time interval in order to release the N9 forwarding tunnel. The detection can be done by either Source ULCL or Target ULCL, either of which notifies the SMF.

NOTE 7: It is up to network configuration whether the detection of no active traffic is performed by the Source ULCL or the Target ULCL. As an alternative to the detection of no active traffic, the AF can send an explicit notification to the SMF when traffic to/from this UE ceases to exist, leading the SMF to release the Source ULCL and the Source UPF (PSA2) .

11. The SMF releases via N4 the PSA2.

12. The SMF releases the Source Branching Point or the Source ULCL.

NOTE 8: If the Target Branching Point or Target ULCL and the PSA2 are co-located in a single UPF then steps 11 and 12 can be merged.

The 4G network will co-exist with 5G network for a long period. And the 3GPP standard has defined the interworking between 5G System (5GS) and Evolved Packet System (EPS) (See 3GPP TS23.501 v16.6.0, clause 4.3.1 for 5GS Interworking with the Evolved Packet Core (EPC) in a Non-Roaming architecture) . Some operators have been asking if it is possible for the 4G network to also provide the similar edge computing capabilities as the 5G network.

However, the above ULCL function with multiple PDU Session anchors (PSAs) is only defined for 5GC. There is no signaling procedure to support ULCL insertion, change or removal in EPC standards. In case of the handover from 5GS to EPS, the ULCL function is released and the edge session anchor is discontinued.

In EPC network, there is only a single anchor point in the data path, that is, the PGW-U. The single PGW-U anchor can’ t be changed during the lifetime of a Packet Data Network (PDN) connection (the PDN connection in the EPC (4G) corresponds to the PDU session in the 5GC) .

Therefore, it is desired to have the ULCL function in EPC.

SUMMARY

In order to solve or at least alleviate the above problems in the conventional technical solutions, the present disclosure provides following technical solutions of:

● inserting a ULCL PSA in the data path at PDN connection establishment;

● keeping the ULCL PSA during the mobility in EPS network, and triggering PDN connection reactivation (also called PDN reactivation) , which includes PDN connection release and PDN connection reestablishment, based on e.g. UE location and/or service information after mobility procedure is completed, so that the ULCL PSA is changed after the PDN reactivation; and

● keeping the ULCL PSA during the handover between 5GS and EPS, and triggering PDN/PDU reactivation based on e.g. UE location and/or service information after the handover is completed, so that the ULCL PSA is changed after PDN/PDU reactivation.

According to a first aspect of the present disclosure, a method at a first control plane entity is provided. The method includes: determining that a second control plane entity selected by the first control plane entity supports selection of a first user plane entity and a ULCL function entity; and transmitting, to the second control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.

In an exemplary embodiment, the indication includes a first address, that is to be allocated to a first user plane entity, for a ULCL function entity to transmit Downlink (DL) traffic to the first user plane entity.

In an exemplary embodiment, the method further includes: receiving, from the second control plane entity, a second address, that is allocated to a ULCL function entity and transmitted by the ULCL function entity to the second control plane entity, for a first user plane entity to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the method further includes: selecting, based on the received second address, the first user plane entity; and transmitting the second address to the first user plane entity for the first user plane entity to transmit the UL traffic to the ULCL function entity.

In an exemplary embodiment, the method further includes: transmitting the second address to a first mobility management entity.

In an exemplary embodiment, the first user plane entity and the ULCL function entity are collocated.

In an exemplary embodiment, the indication is transmitted in a Create Session Request message, and the first address is an Internal Full Qualified-Tunnel Endpoint Identifier (F-TEID) that is transmitted in an S5/S8-U SGW F-TEID Information Element (IE) in the Create Session Request message.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is received in an S5/S8-U PGW F-TEID IE in a Create Session Response message from the second control plane entity, transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message to the mobility management entity, and transmitted in a UL remote Forwarding Action Rule (FAR) in a Packet Forwarding Control Protocol (PFCP) Session Establishment Request message to the first user plane entity.

In an exemplary embodiment, the first control plane entity includes a Serving Gateway Control plane (SGW-C) entity, the second control plane entity includes a combined Packet Data Network Gateway Control plane (PGW-C) and SMF entity, the first user plane entity includes a Serving Gateway User plane (SGW-U) entity, and the ULCL function entity includes a ULCL PSA entity, and the first mobility management entity includes a Mobility Management Entity (MME) .

According to a second aspect of the present disclosure, a method, at a second control plane entity that supports selection of a first user plane entity and a ULCL function entity. The method includes: performing a process of inserting a ULCL function entity during a connection establishment.

In an exemplary embodiment, said performing the process of inserting the ULCL function entity includes: determining to insert a ULCL function entity; and performing session establishment with the ULCL function entity.

In an exemplary embodiment, the ULCL function entity is determined to be inserted based on at least one of:

a location of a User Equipment (UE) , or

service information related to the ULCL function entity.

In an exemplary embodiment, the service information includes at least one of:

a Data Network Access Identifier ‘DNAI’ , or

a traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the traffic forwarding rule for the ULCL function entity includes routing contexts to local DN for edge breakout by the ULCL function entity.

In an exemplary embodiment, said performing the process of inserting the ULCL function entity further includes: receiving, from a first control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.

In an exemplary embodiment, the indication includes a first address, that is to be allocated to the first user plane entity, for the ULCL function entity to transmit Downlink (DL) traffic to the first user plane entity.

In an exemplary embodiment, said performing the session establishment with the ULCL function entity further includes: triggering session establishment to a second user plane entity; and receiving, from the second user plane entity, a third address, that is allocated to the second user plane entity.

In an exemplary embodiment, said performing the session establishment with the ULCL function entity further includes: transmitting, to the ULCL function entity, a session establishment request message; and receiving, from the ULCL function entity, a session establishment response message,

wherein the session establishment request message includes: the first address, that is received from the first control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity; the third address, that is received from the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity; and the traffic forwarding rule for the ULCL function entity; and

wherein the session establishment response message includes: a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity; and a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, said performing the session establishment with the ULCL function entity further includes: transmitting, to the second user plane entity, the received fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, said performing the session establishment with the ULCL function entity further includes: transmitting, to the first control plane entity, the received second address that is allocated to the ULCL function entity.

In an exemplary embodiment, the indication is received in a Create Session Request message, and the first address is an Internal F-TEID that is received in an S5/S8-U SGW F-TEID IE of the Create Session Request message.

In an exemplary embodiment, the transmitted session establishment request message includes a PFCP Session Establishment Request message, which includes: a UL remote FAR that is set to an N9 PSA F-TEID as the third address, a DL remote FAR that is set to the Internal F-TEID as the first address, and the traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the received session establishment response message includes a PFCP Session Establishment Response message, which includes: an S5-U ULCL F-TEID as the second address, and an N9 ULCL F-TEID as the fourth address.

In an exemplary embodiment, the fourth address is an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message.

In an exemplary embodiment, the method further includes: receiving, from another first control plane entity, as a target first control plane entity, a fifth address that is allocated to another first user plane entity, as a target first user plane entity, and transmitted by the target first user plane entity to the target first control plane entity; and transmitting the fifth address to the ULCL function entity for the ULCL function entity to establish a session with the target first user plane entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity.

In an exemplary embodiment, the fifth address is received in a case where the target first control plane entity receives the second address from a first mobility management entity, and transmits the second address to the target first user plane entity, wherein the second address was received by the first mobility management entity from the second control plane entity via the source first control plane entity.

In an exemplary embodiment, the method further includes: transmitting, to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity.

In an exemplary embodiment, the method further includes: re-performing the process of inserting a ULCL function entity for a new connection establishment to establish another ULCL function entity.

In an exemplary embodiment, the fifth address is a Target S5/S8-U SGW F-TEID that is received in a Modify Bearer Request message, and is transmitted in a DL remote FAR of a PFCP Session Modification Request message.

In an exemplary embodiment, the method further includes: transmitting, to the ULCL function entity, a session modification request message; and receiving, from the ULCL function entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the session modification request message is transmitted in a case where handover from an EPS to a 5GS is required.

In an exemplary embodiment, the method further includes: receiving, from a second mobility management entity, a seventh address that is allocated to the access node; and transmitting the received seventh address to the ULCL function entity for the ULCL function entity to transmit DL traffic to the access node.

In an exemplary embodiment, the method further includes: receiving a handover complete indication from the second mobility management entity; and triggering session modification to the ULCL function entity for the ULCL function entity to switch the DL traffic to the access node based on the received seventh address.

In an exemplary embodiment, the transmitted session modification request message includes a PFCP Session Modification Request message, and the received session modification response message includes a PFCP Session Modification Response message, which includes an N3 ULCL F-TEID as the sixth address.

In an exemplary embodiment, the seventh address is an N3 Next Generation-Radio Access Network (NG-RAN) F-TEID that is received in an Nsmf_PDU Session_Update_SM Context Request message, and is transmitted in a PFCP Session Modification Request message.

In an exemplary embodiment, the first control plane entity may include an SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include an SGW-U entity, the ULCL function entity may include a ULCL PSA entity, the first mobility management entity includes a Mobility Management Entity (MME) , the second mobility management entity includes an Access and Mobility Management Function (AMF) entity.

According to a third aspect of the present disclosure, a method at a ULCL function entity is provided. The method includes: receiving a session establishment request message from a second control plane entity that supports selection of a first user plane entity and a ULCL function entity; and transmitting, to the second control plane entity, a session establishment response message.

In an exemplary embodiment, the session establishment request message includes: a first address, that is to be allocated by a first control plane entity to the first user plane entity, and is received from the first control plane entity via the second control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity; a third address, that is allocated to the second user plane entity, and is received from the second user plane entity via the second control plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity; and a traffic forwarding rule for the ULCL function entity; and the session establishment response message includes: a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity; and a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the ULCL function entity is collocated with the first user plane entity.

In an exemplary embodiment, the received session establishment request message includes a PFCP Session Establishment Request message, which includes: a UL remote FAR IE that is set to an N9 PSA F-TEID as the third address, a DL remote FAR IE that is set to the Internal F-TEID as the first address, and the traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the transmitted session establishment response message includes a PFCP Session Establishment Response message, which includes: an S5-U ULCL F-TEID as the second address, and a N9 ULCL F-TEID as the fourth address.

In an exemplary embodiment, the method further includes: receiving, from the second control plane entity, a fifth address, that is allocated to another first user plane entity, as a target first user plane entity, for the ULCL function entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity, wherein the fifth address was received by the target first control plane entity from the target first user plane entity and transmitted to the second control plane entity.

In an exemplary embodiment, the method further includes: receiving, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity; and releasing the session between the ULCL function entity and the target first user plane entity.

In an exemplary embodiment, the fifth address is a Target S5/S8-U SGW F-TEID that is received in a DL remote FAR of a PFCP Session Modification Request message.

In an exemplary embodiment, the method further includes: receiving a session modification request message from the second control plane entity; and transmitting, to the second control plane entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the session modification request message is received in a case where handover from an EPS to a 5GS is required.

In an exemplary embodiment, the method further includes: receiving, from the second control plane entity, a seventh address, that is allocated to the access node and transmitted to the second control plane entity from a second mobility management entity, for the ULCL function entity to transmit DL traffic to the access node.

In an exemplary embodiment, the method further includes: switching the DL traffic to the access node based on the received seventh address, in a case where a handover complete indication is received by the second control plane entity from the second mobility management entity.

In an exemplary embodiment, the received session modification request message includes a PFCP Session Modification Request message, and the transmitted session modification response message includes a PFCP Session Modification Response message, which includes an N3 ULCL F-TEID as the sixth address.

In an exemplary embodiment, the seventh address is an N3 NG-RAN F-TEID that is received in a PFCP Session Modification Request message.

In an exemplary embodiment, the first control plane entity includes a SGW-C entity, the second control plane entity includes a combined PGW-C and SMF entity, the first user plane entity includes an SGW-U entity, the ULCL function entity includes a ULCL PSA entity, the second user plane entity includes a PSA entity, the first mobility management entity is an MME, and the second mobility management entity includes an AMF entity.

According to a fourth aspect of the present disclosure, a method at a first user plane entity is provided. The method includes: receiving, from a first control plane entity, a second address, that is allocated to a ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, wherein the second address was received by the first control plane entity from the ULCL function entity via a second control plane entity.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is received in a UL remote FAR in a PFCP Session Modification Request message from the first control plane entity.

In an exemplary embodiment, the first control plane entity includes a SGW-C entity, the second control plane entity includes a combined PGW-C and SMF entity, the first user plane entity includes a SGW-U entity, and the ULCL function entity includes a ULCL PSA entity.

According to a fifth aspect of the present disclosure, a method at a second user plane entity is provided. The method includes: transmitting, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity; and receiving, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the second control plane entity supports selection of a first user plane entity and a ULCL function entity.

In an exemplary embodiment, the third address is an N9 PSA F-TEID that is transmitted in a PFCP Session Establishment Response message, and the fourth address is an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.

In an exemplary embodiment, the second user plane entity includes a PSA entity, the second control plane entity includes a combined PGW-C and SMF entity, the first user plane entity includes a SGW-U entity, and the ULCL function entity includes a ULCL PSA entity.

According to a sixth aspect of the present disclosure, a method at a second control plane entity that supports selection of a first user plane entity and a ULCL function entity is provided. The method includes: triggering first session modification to a ULCL function entity; and receiving, from the ULCL function entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the method is performed in a case where handover from a 5GS to an EPS is required.

In an exemplary embodiment, the method further includes: triggering second session modification to the second user plane entity; and receiving, from the second user plane entity, a third address, that is allocated to the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity.

In an exemplary embodiment, the method further includes: transmitting the second address to a mobility management entity.

In an exemplary embodiment, the method further includes: receiving, from a first control plane entity, an eighth address that is allocated to the first user plane entity; and transmitting, to the ULCL function entity, the eighth address for the ULCL function entity to transmit DL traffic to the first user plane entity and the third address for the ULCL function entity to transmit UL traffic to the second user plane entity.

In an exemplary embodiment, the method further includes: transmitting, to the second user plane entity, the fourth address for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is received in a PFCP Session Modification Response message from the ULCL function entity, and the fourth address is a N9 ULCL F-TEID that is received in the PFCP Session Modification Response message from the ULCL function entity.

In an exemplary embodiment, the third address is an N9 PSA F-TEID that is received in a PFCP Session Modification Response message from the second user plane entity.

In an exemplary embodiment, the third address is an N9 PSA F-TEID that is transmitted in a PFCP Session Modification Request message to the ULCL function entity, and the eighth address is an S5/S8-U SGW F-TEID that is transmitted in the PFCP Session Modification Request message to the ULCL function entity.

In an exemplary embodiment, the fourth address is the N9 ULCL F-TEID that is transmitted in a PFCP Session Modification Request message to the second user plane entity.

In an exemplary embodiment, the method further includes: transmitting, to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the first user plane entity.

In an exemplary embodiment, the mobility management entity includes an AMF entity, the first control plane entity includes a SGW-C entity, the second control plane entity includes a combined PGW-C and SMF entity, the first user plane entity includes a SGW-U entity, the ULCL function entity includes a ULCL PSA entity, and the second user plane entity includes a PSA entity.

In an exemplary embodiment, the method further includes: performing the process of inserting a ULCL function entity according to the second aspect of the present disclosure.

According to a seventh aspect of the present disclosure, a method at a ULCL function entity is provided. The method includes: receiving, from a second control plane entity, a trigger of first session modification for the ULCL function entity; and transmitting, to the second control plane entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the method further includes: receiving a third address and an eighth address from the second control plane entity, wherein the third address is allocated to the second user plane entity, and forwarded from the second user plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the second user plane entity, and the eighth address is allocated to the first user plane entity, and forwarded from the first control plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the first user plane entity.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is transmitted in a PFCP Session Modification Response message to the second control plane entity, and the fourth address is an N9 ULCL F-TEID that is transmitted in the PFCP Session Modification Response message to the second control plane entity.

In an exemplary embodiment, the third address is an N9 PSA F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity, and the eighth address is an S5/S8-U SGW F-TEID that is received in the PFCP Session Modification Request message from the second control plane entity.

In an exemplary embodiment, the method further includes: receiving, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the first user plane entity; and releasing the session between the ULCL function entity and the first user plane entity.

In an exemplary embodiment, the first control plane entity may include a SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include a SGW-U entity, the ULCL function entity may include a ULCL PSA entity, and the second user plane entity may include a PSA entity.

According to an eighth aspect of the present disclosure, a method at a second user plane entity is provided. The method includes: transmitting, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity; and receiving, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity and forwarded from the ULCL function entity by the second control plane entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the third address is an N9 PSA F-TEID that is transmitted in a PFCP Session Modification Response message, and the fourth address is an N9 ULCL F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity.

In an exemplary embodiment, the second user plane entity includes a PSA entity, the second control plane entity includes a combined PGW-C and SMF entity, and the ULCL function entity includes a ULCL PSA entity.

According to a ninth aspect of the present disclosure, a first control plane entity is provided. The first control plane entity includes: at least one processor, and at least one memory, storing instructions which, when executed on the at least one processor, cause the first control plane entity to perform any of the methods according to the first aspect of the present disclosure.

According to a tenth aspect of the present disclosure, a second control plane entity that supports selection of a first user plane entity and a ULCL function entity is provided. The second control plane entity includes: at least one processor, and at least one memory, storing instructions which, when executed on the at least one processor, cause the second control plane entity to perform any of the methods according to the second and sixth aspects of the present disclosure.

According to an eleventh aspect of the present disclosure, a ULCL function entity is provided. The ULCL function entity includes: at least one processor, and at least one memory, storing instructions which, when executed on the at least one processor, cause the ULCL function entity to perform any of the methods according to the third and seventh aspects of the present disclosure.

According to a twelfth aspect of the present disclosure, a first user plane entity is provided. The first user plane entity includes: at least one processor, and at least one memory, storing instructions which, when executed on the at least one processor, cause the first user plane entity to perform any of the methods according to the fourth aspect of the present disclosure.

According to a thirteenth aspect of the present disclosure, a second user plane entity is provided. The second user plane entity includes: at least one processor, and at least one memory, storing instructions which, when executed on the at least one processor, cause the second user plane entity to perform any of the methods according to the fifth and eighth aspects of the present disclosure.

According to a fourteenth aspect of the present disclosure, a computer readable storage medium is provided. The computer readable storage medium has computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of the first to eighth aspects of the present disclosure.

The technical solutions of the present disclosure may achieve at least benefits of:

● Introducing ULCL function in the EPC network to provide edge breakout capability for specific traffic flows of a PDN connection in EPC network, which strengthens the EPC network with the similar 5GC edge computing capability; and

● providing solutions to change ULCL function by triggering PDN reactivation according to at least the UE location and the service information after the completion of the UE mobility procedure or the handover between 5GS and EPS.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and characteristics of the present disclosure will be more apparent, according to descriptions of preferred embodiments in connection with the drawings, in which:

FIG. 1 schematically illustrates a user plane architecture for ULCL function;

FIG. 2 schematically shows exemplary simultaneous change of Branching Point or ULCL and additional PSAfor a PDU Session in 5GS;

FIG. 3 schematically shows an exemplary network architecture for over which the present disclosure can be implemented;

FIG. 4 schematically shows a method for ULCL insertion at a first control plane entity according to a first exemplary embodiment of the present disclosure;

FIG. 5 schematically shows a method for ULCL insertion at a second control plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 6 schematically shows a method for ULCL insertion at a ULCL function entity according to the first exemplary embodiment of the present disclosure;

FIG. 7 schematically shows a method for ULCL insertion at a first user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 8 schematically shows a method for ULCL insertion at a second user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 9 schematically shows an exemplary signaling sequence diagram of ULCL insertion at initial PDN connection establishment procedure, in which the methods at various entities according to the first exemplary embodiment of the present disclosure are applied;

FIG. 10 schematically shows exemplary user plane traffic routing for collocated SGW-U and ULCL PSA1 according to the first exemplary embodiment of the present disclosure;

FIG. 11A schematically shows an exemplary signaling sequence diagram of ULCL changing after SGW relocation Type 1, in which methods at various entities according to the first exemplary embodiment of the present disclosure are applied;

FIG. 11B schematically shows an exemplary signaling sequence diagram of a ULCL changing after SGW relocation Type 2, in which the methods at various entities according to the first exemplary embodiment of the present disclosure are applied;

FIG. 12 schematically shows an exemplary traffic flow between Target SGW-U and ULCL PSA1 before PDN reactivation according to the first exemplary embodiment of the present disclosure;

FIG. 13 schematically shows an exemplary signaling sequence diagram of ULCL keeping in a scenario of Handover (HO) from EPS to 5GS and ULCL changing after the HO from EPS to 5GS, in which the methods at various entities according to the first exemplary embodiment of the present disclosure are applied;

FIG. 14 schematically shows a method for ULCL keeping at a second control plane entity according to a second exemplary embodiment of the present disclosure;

FIG. 15 schematically shows a method for ULCL keeping at a ULCL function entity according to the second exemplary embodiment of the present disclosure;

FIG. 16 schematically shows a method for ULCL keeping at a second user plane entity according to the second exemplary embodiment of the present disclosure;

FIG. 17 schematically shows an exemplary signaling sequence diagram of ULCL keeping in a scenario of HO from 5GS to EPS and ULCL changing after the HO from 5GS to EPS, in which the methods at various entities according to the second exemplary embodiment of the present disclosure are applied;

FIG. 18 schematically shows an exemplary traffic flow between SGW-U and ULCL PSA1 after handover from 5GS to EPS before PDN reactivation according to the second exemplary embodiment of the present disclosure;

FIG. 19 schematically shows an exemplary structural block diagram of a first control plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 20 schematically shows another exemplary structural block diagram of a first control plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 21 schematically shows an exemplary structural block diagram of a second control plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 22 schematically shows another exemplary structural block diagram of a second control plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 23 schematically shows an exemplary structural block diagram of a ULCL function entity according to the first exemplary embodiment of the present disclosure;

FIG. 24 schematically shows another exemplary structural block diagram of a ULCL function entity according to the first exemplary embodiment of the present disclosure;

FIG. 25 schematically shows an exemplary structural block diagram of a first user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 26 schematically shows another exemplary structural block diagram of a first user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 27 schematically shows an exemplary structural block diagram of a second user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 28 schematically shows another exemplary structural block diagram of a second user plane entity according to the first exemplary embodiment of the present disclosure;

FIG. 29 schematically shows an exemplary structural block diagram of a second control plane entity according to the second exemplary embodiment of the present disclosure;

FIG. 30 schematically shows another exemplary structural block diagram of a second control plane entity according to the second exemplary embodiment of the present disclosure;

FIG. 31 schematically shows an exemplary structural block diagram of a ULCL function entity according to the second exemplary embodiment of the present disclosure;

FIG. 32 schematically shows another exemplary structural block diagram of a ULCL function entity according to the second exemplary embodiment of the present disclosure;

FIG. 33 schematically shows an exemplary structural block diagram of a second user plane entity according to the second exemplary embodiment of the present disclosure; and

FIG. 34 schematically shows another exemplary structural block diagram of a second user plane entity according to the second exemplary embodiment of the present disclosure.

It should be noted that throughout the drawings, same or similar reference numbers are used for indicating same or similar elements; various parts in the drawings are not drawn to scale, but only for an illustrative purpose, and thus should not be understood as any limitations and constraints on the scope of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, the principle and spirit of the present disclosure will be described with reference to illustrative embodiments. Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

Those skilled in the art will appreciate that the term “exemplary” is used herein to mean “illustrative, ” or “serving as an example, ” and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms “first” and “second, ” and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term “step, ” as used herein, is meant to be synonymous with “operation” or “action. ” Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.

References in the specification to “one embodiment, ” “an embodiment, ” “an example embodiment, ” etc. indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be liming of exemplary embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed terms.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term “network” refers to a network following any suitable (wireless or wired) communication standards. For example, the wireless communication standards may comprise new radio (NR) , long term evolution (LTE) , LTE-Advanced, wideband code division multiple access (WCDMA) , high-speed packet access (HSPA) , Code Division Multiple Access (CDMA) , Time Division Multiple Address (TDMA) , Frequency Division Multiple Access (FDMA) , Orthogonal Frequency-Division Multiple Access (OFDMA) , Single carrier frequency division multiple access (SC-FDMA) and other wireless networks. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , etc. UTRA includes WCDMA and other variants of CDMA. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, Ad-hoc network, wireless sensor network, etc. In the following description, the terms “network” and “system” can be used interchangeably.

Furthermore, the communications between two devices in the network may be performed according to any suitable communication protocols, including, but not limited to, the wireless communication protocols as defined by a standard organization such as 3GPP or the wired communication protocols. For example, the wireless communication protocols may comprise the first generation (1G) , 2G, 3G, 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future.

The term “entity” or “network entity” used herein refers to a network device or network node or network function in a communication network, and may also refer to a virtualized entity that may be implemented on cloud. For example, in a wireless communication network such as a 3GPP-type cellular network, a core network device may offer numerous servicesto customers who are interconnected by an access network device. Each access network device is connectable to the core network device over a wired or wireless connection.

The term “CN entity” refers to any suitable function which can be implemented in a network entity (physical or virtual) of a communication network. For example, a network entity can be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g. on a cloud infrastructure. For example, the 5G Core Network system (5GC) may comprise a plurality of functions such as AMF, SMF, UDM (Unified Data Management) , PCF (Policy Control Function) , UPF (User plane Function) , NRF (Network Repository Function) , etc. For example, the 4G Core Network system (such as EPC) may include MME, HSS (home subscriber server) , P-GW, BM-SC, etc. In other embodiments, the CN entity may comprise different types of functions for example depending on the specific network.

FIG. 3 schematically shows an exemplary network architecture over which the present disclosure can be implemented, in which the SGW-U and the ULCL function entity (e.g., ULCL PSA1) are logically separate user plane entities but are collocated physically, and are controlled by the SGW-C and the combined PGW-C+SMF respectively via separate PFCP sessions.

Here, “combined PGW-C+SMF” refers to a control plane entity having functions of both PGW-C and SMF. The combined PGW-C+SMF as proposed in the present disclosure can support selection of the collocated user plane, i.e., the collocated SGW-U and the ULCL function entity, based on system configuration.

The collocation of the SGW-U and the ULCL function entity as proposed in the present disclosure may enable to reduce one hop (from RAN to DN) in the user plane, which may reduce the user plane latency, and save user plane resource.

In the example of FIG. 3, the combined PGW-C+SMF establishes the UPF PSA0 and the inserts ULCL PSA1 at the PDN connection establishment. The SGW-C selects and controls the SGW-U which is collocated with the ULCL PSA1.

The basic ideas of the present disclosure mainly consist in:

-inserting a ULCL function entity (e.g., ULCL PSA1 as shown in FIG. 3) , i.e., establishing ULCL function, that is collocated with the SGW-U during PDN connection establishment according to e.g., UE location and/or service information related to the ULCL function entity (locally configured or received from the PCF) , thus two PSA (e.g., ULCL PSA1 and UPF PSA0 as shown in FIG. 3) being established in the data path after a successful PDN connection establishment, wherein the ULCL PSA1 is used for edge breakout;

- keeping the ULCL function entity in the data path at UE mobility, such as SGW relocation Type 1 (corresponding to FIG. 11A) , or SGW relocation Type 2 (corresponding to FIG. 11B) , HO from EPS to 5GS (corresponding to FIG. 13) , HO from 5GS to EPS (corresponding to FIG. 17) , etc.; and

- triggering PDN reactivation, including PDN connection release and PDN connection reestablishment, based on e.g. UE location and/or service information after the mobility procedure is completed.

Hereinafter, a method 400 for ULCL insertion that is performed at a first control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 4. It should be understood that the first control plane entity may be any node that can be configured to perform the method 400 as described below, including a virtualized entity that may be implemented on cloud..

As shown in FIG. 4, in step S401, the first control plane entity may determine that a second control plane entity selected by the first control plane entity can support selection of a first user plane entity and a ULCL function entity that are collocated (e.g., based on system configuration) .

Then in step S403, the first control plane entity may transmit an indication to the selected second control plane entity, indicating to the second control plane entity that collocated user plane (i.e., a first user plane entity and a ULCL function entity that are collocated) shall be selected.

In an exemplary embodiment, the indication may include a first address, e.g., a reserved Internal F-TEID, which may take an unused IP address, such as 0.0.0.0. On the other hand, the first address may be allocated to a first user plane entity for its collocated ULCL function entity to transmit DL traffic to the first user plane entity.

In an exemplary embodiment, the indication may be transmitted in a Create Session Request message to the second user plane entity, and the first address may be an Internal F-TEID that is transmitted in an S5/S8-U SGW F-TEID IE in the Create Session Request message.

After step S403, the first control plane entity may receive, from the second control plane entity, a second address, that is allocated to a ULCL function entity and transmitted by the ULCL function entity to the second control plane entity, for a first user plane entity to transmit UL traffic to the ULCL function entity.

When determining a collocated first user plane entity to be selected based on the received second address, the first control plane entity may select the first user plane entity collocated with the ULCL function entity, based on the received second address. Then, the first control plane entity may transmit the second address to the first user plane entity for the first user plane entity to transmit the UL traffic to the ULCL function entity.

In an exemplary embodiment, the second address may be an S5-U ULCL F-TEID that is received in an S5/S8-U PGW F-TEID IE in a Create Session Response message from the second control plane entity, and may be transmitted in a UL remote FAR in a PFCP Session Establishment Request message to the first user plane entity.

The first control plane entity may also transmit the second address to a first mobility management entity.

In an exemplary embodiment, the second address may be an S5-U ULCL F-TEID that is transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message to the first mobility management entity.

In an exemplary embodiment, the first control plane entity may include an SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include an SGW-U entity, and the ULCL function entity may include a ULCL PSA entity.

Hereinafter, a method 500 for ULCL insertion that is performed at a second control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 5. It should be understood that the second control plane entity may be any node that can be configured to perform the method 500 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 500 at the second control plane entity at least partly corresponds to the method 400 at the first control plane entity. Thus, some description of the method 500 may refer to that of method 400 as previously described, and thus will be omitted here for simplicity.

As shown in FIG. 5, in step S501, the second control plane entity that supports selection of a first user plane entity and a ULCL function entity may perform a process of inserting a ULCL function entity during a connection establishment.

In step S501, the second control plane entity may receive an indication from the first control plane entity, indicating, to the second control plane entity, of selecting a first user plane entity and a ULCL function entity that are collocated.

As previously the indication includes a first address, that is to be allocated to the first user plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity.

In an exemplary embodiment, the indication may be received in a Create Session Request message from the first user plane entity, and the first address may be an Internal F-TEID that is transmitted in an S5/S8-U SGW F-TEID IE in the Create Session Request message.

In the method 500, the second control plane entity may also trigger session establishment to a second user plane entity; and receive, from the second user plane entity, a third address, that is allocated to the second user plane entity.

In step S501, the second control plane entity may determine to insert a ULCL function entity, and perform session establishment with the ULCL function entity.

In an exemplary embodiment, the ULCL function entity may be determined to be inserted based on at least one of: UE location, or service information related to the ULCL function entity.

In an exemplary embodiment, the service information may include at least one of: a DNAI, or a traffic forwarding rule for the ULCL function entity. The service information may be configured locally in the second control plane entity, or based on Policy and Charging Control (PCC) rules received from the PCF. The concept of the service information may refer to 3GPP TS 29.512 V17.0.0, and 3GPP TS 29.512 V17.0.0 is incorporated herein by reference in its entirety.

The traffic forwarding rule for the ULCL function entity may include routing contexts, e.g., N6 interface information, to local DN (also called Edge DN) for edge breakout by the ULCL function entity. The routing contexts may be used by the ULCL function entity to forward the UL traffic to the Edge DN via the N6 interface, as shown in FIG. 10.

In the step of performing the session establishment with the ULCL function entity, the second control plane entity may transmit a session establishment request message to the ULCL function entity; and receive a session establishment response message from the ULCL function entity.

The session establishment request message may include:

the first address, that is received from the first control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity,

the third address, that is received from the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity, and

the traffic forwarding rule for the ULCL function entity.

The session establishment response message may include:

a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, and

a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the transmitted session establishment request message may include a PFCP Session Establishment Request message, which may include: a UL FAR that is set to a N9 PSA F-TEID as the third address, a DL remote FAR that is set to the Internal F-TEID as the first address, and the traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the received session establishment response message may include a PFCP Session Establishment Response message, which may include: an S5-U ULCL F-TEID as the second address, and an N9 ULCL F-TEID as the fourth address.

In the step of performing the session establishment with the ULCL function entity, the second control plane entity may transmit, to the second user plane entity, the received fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the fourth address may be an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.

In the step of performing the session establishment with the ULCL function entity, the second control plane entity may transmit, to the first control plane entity, the received second address that is allocated to the ULCL function entity.

In an exemplary embodiment, the second address may be an S5-U ULCL F-TEID that is transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message.

As such, the ULCL insertion performed at the second control plane entity during the initial PDN connection establishment is completed. Thus, in the UL direction, the first user plane entity may transmit the UL traffic to the ULCL function entity via the S5-U interface between the ULCL function entity and the first user plane entity based on the second address (S5-U ULCL F-TEID) ; and the ULCL function entity may divert the UL traffic in two ways based on the traffic forwarding rules for the ULCL function entity. In particular, the UL traffic in one way (for edge computing) may be forwarded by the ULCL function entity to the Edge DN via the N6 interface between the ULCL function entity and the Edge DN; and the UL traffic in another way may be forwarded by the ULCL function entity to the second user plane entity based on the received third address (e.g., N9 PSA F-TEID) via the N9 interface between the ULCL function entity and the second user plane entity and in turn forwarded by the second user plane entity to the central DN via the N6 interface between the second user plane entity and the central DN. Accordingly, in the DL direction, the DL traffic for edge computing from the Edge DN may enter the second user plane entity via the N6 interface and may be forwarded to the ULCL function entity via the N9 interface based on the fourth address (N9 ULCL F-TEID) , and the ULCL function entity may transmit the DL traffic to the first user plane entity via the S5-U interface based on the received first address (e.g., Internal F-TEID) .

According to the technical solution of the present disclosure, the second control plane entity places the second address (e.g., S5-U ULCL F-TEID) , that is allocated to the ULCL function entity, in an existing IE (e.g., S5/S8-U PGW F-TEID IE) of the Create Session Response message, and transmits the Create Session Response message to the first control plane entity. Thus, only the second control plane entity knows that the S5/S8-U PGW F-TEID IE is filled with a new value (second address) . Other entities, such as the first control plane entity (e.g., the SGW-C) , and the first mobility management entity (e.g., the MME) , receiving the Create Session Response message would take the IE of the Create Session Response message as a normal one for their normal subsequent operations. That is, those other entities do not know that the S5/S8-U PGW F-TEID IE is filled with a new value (second address) .

When the first control plane entity (e.g., the SGW-C) detects that a collocated SGW-U is to be selected based on the second address contained in the existing S5/S8-U PGW F-TEID it receives, the first control plane entity (e.g., the SGW-C) may select the first user plane entity (e.g., the SGW-U) collocated with the ULCL function entity, and transmit a PFCP Session Establishment Request message to the first user plane entity (e.g., the SGW-U) with the UL remote FAR set to the second address (e.g., S5-U ULCL F-TEID) it receives.

During the PDN connection establishment, only the second control plane entity knows that it is interacting with the ULCL function entity. The ULCL function entity is transparent to the first user plane entity (e.g., the SGW-U) and the first control plane entity (e.g., the SGW-C) . The first user plane entity (e.g., the SGW-U) and the first control plane entity (e.g., the SGW-C) regard the ULCL function entity as a second user plane entity (e.g., a PGW-U) .

In addition, as the legacy behavior, the first mobility management entity (e.g., the MME) stores the received S5/S8-U PGW F-TEID which will be used in the later SGW relocation scenarios, and will be described later.

The ULCL function entity is also transparent to the first mobility management entity (e.g., the MME) . That is, the first mobility management entity regards the ULCL function entity as a legacy PGW-U.

In an exemplary implementation, after the ULCL function entity is inserted during the PDN connection establishment, and the SGW relocation occurs due to UE mobility, the method 500 may further include the following steps.

The second control plane entity may receive a fifth address from another first control plane entity, which is used as a target first control plane entity, wherein the fifth address is allocated to another first user plane entity, which is used as a target first user plane entity.

Here, the fifth address may be transmitted by the target first user plane entity to the target first control plane entity, and forwarded by the target first control plane entity to the second control plane entity.

Then, the second control plane entity may transmit the received fifth address to the ULCL function entity for the ULCL function entity to establish a session with the target first user plane entity to switch the DL traffic to the target first user plane entity from the first user plane entity, which is used as a source first user plane entity.

In an exemplary embodiment, the fifth address may be a Target S5/S8-U SGW F-TEID that is received in a Modify Bearer Request message, and may be transmitted in a DL remote FAR of a PFCP Session Modification Request message.

The fifth address may be received in a case where the target first control plane entity receives the second address from a first mobility management entity, and transmits the second address to the target first user plane entity, wherein the second address was received by the first mobility management entity from the second control plane entity via the source first control plane entity.

Since the second address (e.g., S5-U ULCL F-TEID) of the ULCL function entity is received by the target first user plane entity, and the fifth address (e.g., Target S5/S8-U SGW F-TEID) of the target first user plane entity is received by the ULCL function entity, the ULCL function entity may transmit the DL traffic to the target first user plane entity based on the received fifth address (e.g., Target S5/S8-U SGW F-TEID) , and the target first user plane entity may transmit the UL traffic to the ULCL function entity based on the received second address (e.g., S5-U ULCL F-TEID) .

Thus, the traffic may be routed between the UE and the original edge Data Network (DN) via the target first user plane entity and the ULCL function entity after the SGW relocation, until PDN reactivation is triggered.

When the second control plane entity determines to trigger the PDN reactivation (including PDN connection release and PDN connection reestablishment) based on at least one of the UE location and the service information, the second control plane entity may transmit, to the ULCL function entity, an indication of releasing the session between the ULCL function entity and the target first user plane entity.

The second control plane entity may then perform step S501 as previously described during PDN reactivation to perform the PDN connection reestablishment to insert another ULCL function entity, in particular, to insert another ULCL function entity collocated with another first user plane entity, e.g., in order to obtain better user experience. It should be understood that the first user plane entity that is collocated with the newly inserted ULCL function entity may be the former target first user plane entity, or may be some other suitable first user plane entity, which depends on at least one of the UE location and the service information.

In another exemplary implementation, after the ULCL function entity is inserted during the PDN connection establishment involved in the PDN reactivation, and in a case where HO from EPS to 5GS is required due to UE mobility, the method 500 may further include the following steps.

The second control plane entity may transmit, to the ULCL function entity, a session modification request message; and receive, from the ULCL function entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for the access node to transmit UL traffic to the ULCL function entity.

The second control plane entity may receive, from a second mobility management entity, a seventh address that is allocated to the access node; and transmit the received seventh address to the ULCL function entity for the ULCL function entity to transmit DL traffic to the access node.

In an exemplary embodiment, the transmitted session modification request message may include a PFCP Session Modification Request message, and the received session modification response message may include a PFCP Session Modification Response message, which may include an N3 ULCL F-TEID as the sixth address.

In an exemplary embodiment, the seventh address may be an N3 NG-RAN F-TEID that is received in an Nsmf_PDU Session_Update_SM Context Request message, and is transmitted in a PFCP Session Modification Request message.

After the second control plane entity receives an HO complete indication from the second mobility management entity, the second control plane entity may trigger session modification to the ULCL function entity for the ULCL function entity to switch the DL traffic to the access node based on the received seventh address.

The second control plane entity may then change the ULCL function entity either by the PDU session reactivation (referring to Clause 4.3.5.1 of 3GPP TS 23.502 v16.6.0, which is thus incorporated herein by reference in its entirety) or ULCL change (referring to Clause 4.3.5.7 of 3GPP TS 23.502 v16.6.0 which is thus incorporated herein by reference in its entirety) in 5GC, e.g., in order to obtain better user experience.

In an exemplary embodiment, the first control plane entity may include an SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include an SGW-U entity, the ULCL function entity may include a ULCL PSA entity, the second user plane entity may include a PSA entity, the first mobility management entity is an MME, and the second mobility management entity may include an AMF entity.

Hereinafter, a method 600 for ULCL insertion that is performed at a ULCL function entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 6. It should be understood that the ULCL function entity may be any node that can be configured to perform the method 600 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 600 at the ULCL function entity at least partly corresponds to the method 500 at the second control plane entity. Thus, some description of the method 600 may refer to that of method 500 as previously described, and thus will be omitted here for simplicity.

As previously described, the second control plane entity may determine to insert a ULCL function entity based on at least one of: UE location, or service information related to the ULCL function entity. The service information may include at least one of: a DNAI, or a traffic forwarding rule for the ULCL function entity.

Thus, in step S601, the ULCL function entity may receive a session establishment request message from the second control plane entity that supports selection of a first user plane entity and a ULCL function entity that are collocated.

Then in step S603, the ULCL function entity may transmit, to the second control plane entity, a session establishment response message.

The session establishment request message may include:

a first address, that is to be allocated by a first control plane entity to the first user plane entity, and is received from the first control plane entity via the second control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity;

a third address, that is allocated to the second user plane entity, and is received from the second user plane entity via the second control plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity; and

the traffic forwarding rule for the ULCL function entity.

As previously described, the traffic forwarding rule for the ULCL function entity may include routing contexts to local DN for edge breakout by the ULCL function entity. The routing contexts may be used by the ULCL function entity to forward the UL traffic to the Edge DN via the N6 interface, as shown in FIG. 10.

The session establishment response message may include:

a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity; and

Here, the ULCL function entity is collocated with the first user plane entity.

In an exemplary embodiment, the received session establishment request message may include a PFCP Session Establishment Request message, which may include: a UL remote FAR IE that is set to an N9 PSA F-TEID as the third address, a DL remote FAR IE that is set to the Internal F-TEID as the first address, and the traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the transmitted session establishment response message may include a PFCP Session Establishment Response message, which may include: an S5-U ULCL F-TEID as the second address, and a N9 ULCL F-TEID as the fourth address.

As such, the ULCL insertion performed at the ULCL function entity during the initial PDN connection establishment is completed. Thus, the ULCL function entity may transmit the DL traffic to the first user plane entity based on the received first address (e.g., Internal F-TEID) , and transmit the UL traffic to the second user plane entity based on the received third address (e.g., N9 PSA F-TEID) . Accordingly, the second user plane entity may transmit the UL traffic to the ULCL function entity based on the received fourth address (N9 ULCL F-TEID) that is transmitted by the ULCL function entity and forwarded by the second control plane entity. The second address (S5-U ULCL F-TEID) forwarded by the second control plane entity from the ULCL function entity will be further forwarded by the first control user plane entity to the mobility management entity for the access node to transmit the UL traffic to the ULCL function entity.

In an exemplary implementation, after the ULCL function entity is inserted during the PDN connection establishment, and the SGW relocation occurs due to UE mobility, the method 600 may further include the following steps.

The ULCL function entity may receive, from the second control plane entity, a fifth address, that is allocated to another first user plane entity, which is used as a target first user plane entity, for the ULCL function entity to switch the DL traffic to the target first user plane entity from the first user plane entity which is used as a source first user plane entity, wherein the fifth address was received by the target first control plane entity from the target first user plane entity and transmitted to the second control plane entity.

In an exemplary embodiment, the fifth address may be a Target S5/S8-U SGW F-TEID that is received in a DL remote FAR of a PFCP Session Modification Request message.

When the second control plane entity determines to trigger the PDN reactivation (including PDN connection release and PDN connection reestablishment) based on at least one of the UE location and the service information, the ULCL function entity may receive, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity; and then release the session between the ULCL function entity and the target first user plane entity.

As previously described, the second control plane entity may then perform step S501 as previously described during PDN reactivation to perform the PDN connection reestablishment to insert another ULCL function entity, in particular, to insert another ULCL function entity collocated with another first user plane entity, e.g., in order to obtain better user experience. Accordingly, the newly inserted ULCL function entity may perform the method 600 as previously described.

In another exemplary implementation, after the ULCL function entity is inserted during the PDN connection establishment, and in a case where HO from EPS to 5GS is required due to UE mobility, the method 600 may further include the following steps.

The ULCL function entity may receive a session modification request message from the second control plane entity; and transmit, to the second control plane entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the received session modification request message may include a PFCP Session Modification Request message, and the transmitted session modification response message may include a PFCP Session Modification Response message, which may include an N3 ULCL F-TEID as the sixth address.

The ULCL function entity may receive, from the second control plane entity, a seventh address, that is allocated to the access node and transmitted to the second control plane entity from a second mobility management entity, for the ULCL function entity to transmit DL traffic to the access node.

In a case where an HO complete indication is received by the second control plane entity from the second mobility management entity, the ULCL function entity may switch the DL traffic to the access node based on the received seventh address.

In an exemplary embodiment, the seventh address may be an N3 NG-RAN F-TEID that is received in a PFCP Session Modification Request message.

As previously described, the second control plane entity may then change the ULCL function entity either by the PDU session reactivation (referring to Clause 4.3.5.1 of 3GPP TS 23.502 v16.6.0, which is thus incorporated herein by reference in its entirety) or ULCL change (referring to Clause 4.3.5.7 of 3GPP TS 23.502 v16.6.0 which is thus incorporated herein by reference in its entirety) in 5GC, e.g., in order to obtain better user experience.

In an exemplary embodiment, the first control plane entity may include a SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include an SGW-U entity, the ULCL function entity may include a ULCL PSA entity, the second user plane entity may include a PSA entity, the first mobility management entity is an MME, and the second mobility management entity may include an AMF entity.

Hereinafter, a method 700 for ULCL insertion that is performed at a first user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 7. It should be understood that the first user plane entity may be any node that can be configured to perform the method 700 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 700 at the first user plane entity at least partly corresponds to the method 400 at the first control plane entity. Thus, some description of the method 700 may refer to that of method 400 as previously described, and thus will be omitted here for simplicity.

As shown in FIG. 7, in step S701, the first user plane entity may receive, from a first control plane entity, a second address, that is allocated to a ULCL function entity that is collocated with the first user plane entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, wherein the second address was received by the first control plane entity from the ULCL function entity via the second control plane entity.

In an exemplary embodiment, the second address may be an S5-U ULCL F-TEID that is received in a UL remote FAR in a PFCP Session Modification Request message from the first control plane entity.

As such, the first user plane entity may transmit the UL traffic to the ULCL function entity. On the other hand, the ULCL function entity may transmit DL traffic to the first user plane entity based on the first address it receives, as previously described.

The above process may be performed during the PDN connection establishment.

In an exemplary implementation, after the ULCL function entity is inserted during the PDN connection establishment, and the SGW relocation occurs due to UE mobility, the method 700 may further include the following steps.

The first user plane entity, which is used as a target first user plane entity in this exemplary implementation, may receive a second address from the first control plane entity, which is used as a target first control plane entity in this exemplary implementation.

The second address was allocated to the ULCL function entity, for the target first user plane entity to transmit UL traffic to the ULCL function entity. As previously described, the second address was received by the first control plane entity from the ULCL function entity via the second control plane entity.

In an exemplary embodiment, the second address may be an S5-U ULCL F-TEID that is received in a UL remote FAR in a PFCP Session Establishment Request message from the first control plane entity.

Then, the target first user plane entity may transmit a fifth address, that is allocated to the tar target first user plane entity, to the target first control plane entity, which is to be used for the ULCL function entity to transmit DL traffic to the target first user plane entity.

In an exemplary embodiment, the fifth address may be transmitted by the target first user plane entity to the target first control plane entity, and forwarded by the target first control plane entity to the ULCL function entity via the second control plane entity.

The ULCL function entity may then switch, based on the received fifth address, the DL traffic to the target first user plane entity from the first user plane entity

In an exemplary embodiment, the fifth address may be a Target S5/S8-U SGW F-TEID that is transmitted in a PFCP Session Establishment Response message to the target first control plane entity.

As previously described, the second control plane entity may then perform step S501 as previously described during PDN reactivation to perform the PDN connection reestablishment to insert another ULCL function entity, in particular, to insert another ULCL function entity collocated with another first user plane entity, e.g., in order to obtain better user experience. Accordingly, the first user plane entity that is collocated with the newly inserted ULCL function entity may perform the method 700 as previously described.

In an exemplary embodiment, the first control plane entity may include a SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include a SGW-U entity, and the ULCL function entity may include a ULCL PSA entity.

Hereinafter, a method 800 for ULCL insertion that is performed at a second user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 8. It should be understood that the second user plane entity may be any node that can be configured to perform the method 800 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 800 at the second user plane entity at least partly corresponds to the method 500 at the second control plane entity. Thus, some description of the method 800 may refer to that of method 500 as previously described, and thus will be omitted here for simplicity.

As shown in FIG. 8, in step S801, the second user plane entity may transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity.

Then in step S803, the second user plane entity may receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

The second control plane entity may support selection of a first user plane entity and a ULCL function entity that are collocated.

The above process may be performed during the PDN connection establishment.

In an exemplary embodiment, the third address may be an N9 PSA F-TEID that is transmitted in a PFCP Session Establishment Response message, and the fourth address may be an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.

In an exemplary embodiment, the second user plane entity may include a PSA entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include a SGW-U entity, and the ULCL function entity may include a ULCL PSA entity.

It should be understood that the description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all. Any appropriate order for performing these operations/steps falls within the scope of the present disclosure.

Hereinafter, an exemplary signaling sequence diagram of ULCL insertion at initial PDN connection establishment procedure will be described with reference to FIG. 9, in which the methods 400～800 at various entities according to the first exemplary embodiment of the present disclosure are applied.

In the exemplary signaling sequence diagram of FIG. 9, an MME is shown as an example of the first mobility management entity, an SGW-C is shown as an example of the first control plane entity, a combined PGW-C and SMF is shown as an example of the second control plane entity and may be represented as (combined) PGW-C+SMF, an SGW-U is shown an example of the first user plane entity, a ULCL PSA1 is shown as an example of the ULCL function entity, a UPF (PSA0) is shown as an example of the second user plane entity. As previously described, the SGW-U and the ULCL PSA1 are collocated, which may be represented as (collocated) ULCL PSA1+SGW-U.

It should be noted that the description below mainly focuses on signaling related to the methods 400～800, and some other signaling is not described in detail to avoid obscuring the principle of the present disclosure. In FIG. 9, modification on the signaling related to the methods 400～800 is shown in Bold Italics, in which e.g., Signaling S9_3, S9_5～S9_10 and S9_12 are involved.

In S9_3, when detecting that the selected PGW-C+SMF can support the collocated user plane selection (based on system configuration) , the SGW-C skips SGW-U selection and sends a Create Session Request to the combined PGW-C+SMF, with its S5/S8-U SGW F-TEID set to a reserved Internal F-TEID which is used to indicate to the PGW-C+SMF that the collocated user plane shall be selected.

Note (S9 3) :

The reserved Internal F-TEID may take an unused IP address, such as 0.0.0.0, as an indication for the collocated user plane selection. The Internal F-TEID may also be used by the SGW-U to receive DL traffic from the collocated user plane entity, see Note (S9_5) as well.

In S9_4, the combined PGW-C+SMF triggers PFCP session establishment towards the UPF (PSA0) to establish the PSA0 for the UE. The UPF (PSA0) returns its allocated N9 F-TEID towards the combined PGW-C+SMF.

In S9_5, the combined PGW-C+SMF determines to insert a ULCL (PSA1) function, preferably based on at least one of the UE location and the service information. The service information (such as DNAI, traffic forwarding rules) may be configured locally in the combined PGW-C+SMF or based on the PCC rules received from PCF, which may refer to step 5 in Figure 4.3.6.4-1 of 3GPP TS 23.502 v16.6.0, and 3GPP TS 23.502 v16.6.0 is incorporated herein by reference in its entirety.

The combined PGW-C+SMF triggers the establishment of ULCL PSA1 and sends a PFCP Session Establishment Request message with the UL remote FAR, the DL remote FAR, and the ULCL traffic forwarding rules (also called ULCL rules) , such as traffic filters, routing contexts to local DN (i.e., Edge DN) for edge breakout, e.g., N6 interface information. The routing contexts may be used by the ULCL PSA1 to forward the UL traffic to the Edge DN via the N6 interface, as shown in FIG. 10.

Note (S9 5) :

The DL remote FAR (set to the Internal F-TEID, see the above Note (S9_3) indicates to the ULCL PSA1 to send the DL traffic to the internal tunnel end point of the collocated SGW-U. The UL remote FAR (set to the PSA0 N9 F-TEID) is used by the ULCL PSA1 to send the UL traffic to the UPF (PSA0) .

In S9_6, the ULCL PSA1 sends towards the PGW-C+SMF its allocated S5-U ULCL F-TEID and N9 F-TEID in a PFCP Session Establishment Response message.

Note (S9 6) :

The S5-U ULCL F-TEID is used by the SGW-U to send UL traffic to the ULCL PSA1, and the N9 ULCL F-TEID will be used by the UPF (PSA0) to send DL traffic to the ULCL PSA1.

In S9_7～S9_8, the combined PGW-C+SMF sends a PFCP Session Modification Request message towards the UPF (PSA0) with the DL remote FAR updated to the N9 ULCL F-TEID.

In S9_9, the combined PGW-C+SMF sends towards the SGW-C a Create Session Response message with the S5/S8-U PGW F-TEID IE which contains the value of the S5-U ULCL F-TEID.

In S9_10, when detecting a collocated SGW-U to be selected based on the IP address contained in S5/S8-U PGW F-TEID (received in step In S9_9, containing the value of the S5-U ULCL F-TEID) , the SGW-C may select the SGW-U collocated with the ULCL PSA1 and send a PFCP Session Establishment Request to the SGW-U with the UL remote FAR set to the S5-U ULCL F-TEID.

Note (S9 10) :

The ULCL logic is transparent to the SGW-C and SGW-U. The SGW-C and SGW-U regards the ULCL PSA1 as a PGW-U.

In S9_11, the SGW-U returns its allocated S1-U SGW F-TEID in a PFCP Session Establishment Response towards the SGW-C.

In S9_12, the SGW-C sends a Create Session Response message to the MME with the S5/S8-U PGW F-TEID (containing the value of the S5-U ULCL F-TEID) and the S1-U SGW F-TEID.

Note (S9 12) :

As the legacy behavior, the MME stores the received S5/S8-U PGW F-TEID (containing the value of the S5-U ULCL F-TEID) which will be used in the later SGW relocation scenarios (refer to FIG. 11A and FIG. 11B) .

The ULCL logic is transparent to the MME, i.e., the MME regards the ULCL PSA1 as the legacy PGW-U.

In S9_13～S9_16, the MME continues PDN connection establishment as normal, which may refer to step 6～14 in Figure 5.10.2-1 of 3GPP TS 23.401 v16.8.0 for details. 3GPP TS 23.401 v16.8.0 is thus incorporated herein by reference in its entirety.

As such, the PDN connection establishment procedure is completed.

Note:

As shown in FIG. 10, the collocated SGW-U and ULCL PSA1 are inserted in the data path of the PDN connection after the successful PDN connection establishment. In the UL direction, the ULCL function diverts the traffic in two ways based on the ULCL traffic forwarding rules. The traffic in one way is forwarded to the Central DN via the UPF PSA0, and the traffic in another way for edge computing is forwarded to the Edge DN via the N6 interface. In the DL direction, the traffic for edge computing from the Edge DN enters the ULCL PSA1 via the N6 interface and is forwarded to SGW-U via the S5-U interface, and the traffic from the Central DN is routed via the UPF PSA0 and forwarded to the ULCL PSA1 via the N9 interface, and then is further forwarded to the SGW-U via the S5-U interface. There is no change for the S1-U tunnel between the eNB and the SGW-U.

After the PDN connection establishment procedure is completed in which the ULCL function entity (e.g., ULCL PSA1) is inserted to be collocated with the first user plane entity (e.g., SGW-U) based on e.g., UE location and/or service information (locally configured or received from the PCF) , such scenarios as SGW relocation (e.g., Type 1 and Type 2, which are respectively shown in FIGS. 11A and 11B) , HO from EPS to 5GS (shown in FIG. 13) may occur due to UE mobility.

Hereinafter, exemplary signaling sequence diagrams of ULCL changing after SGW relocation Type 1 and Type 2 will be described respectively with reference to FIGS. 11A and 11B, in which the methods 400～800 at various entities according to the first exemplary embodiment of the present disclosure are applied.

In the exemplary signaling sequence diagrams of FIG. 11A and 11B, an MME is shown as an example of the first mobility management entity, a Target SGW-C is shown as an example of the target first control plane entity, a Source SGW-C is shown as an example of the source first control plane entity, a combined PGW-C and SMF is shown as an example of the second control plane entity and may be represented as (combined) PGW-C+SMF, a Target SGW-U is shown an example of the target first user plane entity, a Source SGW-U is shown an example of the source first user plane entity, a ULCL PSA1 is shown as an example of the ULCL function entity, a UPF (PSA0) is shown as an example of the second user plane entity. As previously described, the source SGW-U and the ULCL PSA1 are collocated, which may be represented as (collocated) ULCL PSA1+Source SGW-U.

The exemplary signaling sequence diagram of FIG. 11A is applied to the SGW relocation Type 1 scenario, details of which follows the procedure as per Clause 5.5.1.1.3 of 3GPP TS 23.401 v16.8.0, which is thus incorporated herein by reference in its entirety.

It should be noted that the description below mainly focuses on signaling related to the methods 400～800, and some other signaling is not described in detail to avoid obscuring the principle of the present disclosure. In FIG. 11A, modification on the signaling related to the methods 400～800 is shown in Bold Italics, in which e.g., Signaling S11A_1, S11A_2, S11A_5, S11A_6, S11A_18, and PDN connection reestablishment related signaling (referring to S9_3, S9_5～S9_10 and S9_12 in FIG. 9) .

In S11A_1, the MME sends a Create Session Request message (with the S5/S8-U PGW F-TEID set to S5/S8-U ULCL F-TEID, referring to S9_12 of FIG. 9) to the Target SGW-C.

Note (S11A 1) :

The MME receives and stores the S5/S8-U PGW F-TEID at ULCL insertion in S9_12 of FIG. 9 as described above.

In S11A_2, the Target SGW-C sends a PFCP Session Establishment Request to the Target SGW-U, and sets the UL remote FAR to the S5/S8-U PGW F-TEID (set to S5/S8-U ULCL F-TEID) received from the MME.

Note (S11A 2) :

The S5/S8-U PGW F-TEID takes the value of the S5/S8-U ULCL F-TEID (referring to S9_4 of FIG. 9 as described above) . After S11A_2, the target SGW-U can send UL traffic to the ULCL PSA1 using the UL remote FAR (i.e., S5/S8-U ULCL F-TEID) .

In S11A_3, the Target SGW-U returns its allocated Target S1-U SGW F-TEID and Target S5/S8-U SGW F-TEID to the Target SGW-C.

In S11A_4, the Target SGW-C sends a Modify Bearer Request (MBReq) message with the Target S5/S8-U SGW F-TEID to the combined PGW-C+SMF.

In S11A_5～S11A_6, the combined PGW-C+SMF updates the DL remote FAR of the ULCL PSA1 with the Target S5/S8-U SGW F-TEID. Then, the ULCL PSA1 can send DL traffic to the Target SGW-U using the DL remote FAR (i.e., Target S5/S8-U SGW F-TEID) .

In S11A_7, the combined PGW-C+SMF replies a Modify Bearer Response (MBResp) message to the Target SGW-C.

In S11A_8～S11A_11, the SGW relocation continues as the existing EPC procedure. At S11A_11, after the SGW relocation is completed, the edge application traffic is routed between UE and the original edge DN via the Target SGW-U and the ULCL PSA1 as shown in FIG. 12, until PDN reactivation is triggered.

In S11A_12～S11A_19, the combined PGW-C+SMF determines to trigger PDN reactivation (including PDN connection release and PDN connection reestablishment) based on e.g., UE location and/or service information. For example, if there is edge application server deployed in the current location of the UE, the PGW-C+SMF may trigger the PDN reactivation either immediately or after a delay timer expiry.

In particular, in S11A_12, the combined PGW-C+SMF sends a Delete Bearer Request message to the Target SGW-C to request PDN reactivation.

In S11A_13, the Target SGW-C sends a Delete Bearer Request message to the MME.

In S11A_14, the MME triggers a PDN reactivation towards the UE.

In S11A_15, the MME sends a Delete Bearer Response message to the Target SGW-C.

In S11A_16, the Target SGW-C triggers PFCP session deletion towards the Target SGW-U.

In S11A_17, the Target SGW-C sends a Delete Bearer Response message to the combined PGW-C+SMF.

In S11A_18, the combined PGW-C+SMF triggers PFCP session deletion towards the ULCL PSA1 by sending, to the ULCL PSA1, an indication of releasing the session between the ULCL PSA1 and the Target SGW-U, and the ULCL PSA1 releases the session accordingly.

In S11A_19, the combined PGW-C+SMF also triggers PFCP session deletion towards the UPF (PSA0) .

Thus, the PDN connection resource in both the control plane and the user plane is released.

Then, a new collocated SGW-U and ULCL may be established in the target site according to the signaling flows in FIG. 9 as previously described to perform the PDN connection reestablishment.

Note:

After the PDN reactivation, the UE will automatically do a new Domain Name System (DNS) query and connect to the new edge application server located in the edge DN close to the target site. That is, a better user experience than that via the original ULCL PSA1 may be obtained. It may be understood that the SGW-U of the new collocated SGW-U and ULCL may be the former Target SGW-U or some other suitable SGW-U. The setup of Target SGW-U and ULCL PSA1 shown in FIG. 12 is released and replaced with the collocated SGW-U and ULCL PSA1 shown in FIG. 10.

The exemplary signaling sequence diagram of FIG. 11B is applied to the SGW relocation Type 2 scenario, details of which follows the procedure as per Clause 5.5.1.2.2 of 3GPP TS 23.401 v16.8.0 (which is thus incorporated herein by reference in its entirety) and the similar logic as the SGW relocation Type 1 scenario as previously described with reference to FIG. 11A.

It should be noted that the description below mainly focuses on signaling related to the methods 400～800, and some other signaling is not described in detail to avoid obscuring the principle of the present disclosure. In FIG. 11B, modification on the signaling related to the methods 400～800 is shown in Bold Italics, in which e.g., Signaling S11B_1, S11 B_2, S11 B_9, S11B_10, signaling related to deleting the session between ULCL PSA1 and Target SGW-U (referring to S11A_18 in FIG. 11A) , and PDN connection reestablishment related signaling (referring to S9_3, S9_5～S9_10 and S9_12 in FIG. 9) .

S11B_1～S11B_3 are identical with those of S11A_1～S11A_3, description of which is thus omitted herein for simplicity.

In S11B_4, the Target SGW-C sends a Create Session Response message (with the S1-U SGW F-TEID for the Target SGW-U) to the MME as the existing EPC standard.

In S11B_5, an HO procedure on RAN side is performed as per Clause 5.5.1.2.2 of 3GPP TS 23.401 v16.8.0.

In S11B_6, the MME sends a Modify Bearer Request message to the Target SGW-C with the S1-U eNB F-TEID.

Note (S11B 6) :

The S1-U eNB F-TEID is only available after S11B_5 for SGW relocation Type 2 (referring to Clause 5.5.1.2.2 of 3GPP TS 23.401 v16.8.0) . That is the difference from SGW relocation Type 1.

In S11B_7, the Target SGW-C triggers PFCP modification with the S1-U eNB F-TEID towards the Target SGW-U, then the Target SGW-U switches the DL traffic towards the eNB on the target side.

In S11B_8～S11B_11, the same procedure as S11A_4～ S11A_7 related to SGW relocation Type 1 is performed for the ULCL PSA1 to switch the DL traffic to the Target SGW-U.

In S11B_12, the Target SGW-C replies a Modify Bearer Response to the MME as the existing EPC standard.

In S11B_13～S11B_15, the same procedure as S11A_9～ S11A_11 related to SGW relocation Type 1 is performed to delete the resource on the source SGW-C and SGW-U.

In S11B_16, the PDN reactivation is triggered after the SGW relocation is completed as per S11A_12～ S11A_19 described previously with reference to FIG. 11A, description of which is thus omitted herein for simplicity.

Although only the above UE mobility scenarios (SGW relocation Type 1 and Type 2) with ULCL in EPC are described in detail in the present disclosure, it may be understood that other UE mobility scenarios with ULCL in EPC follow the same principle as those described with reference to FIG. 11A and 11B. That is, the mobility is executed as the legacy EPC procedure (i.e., the ULCL PSA1 is treated as the PGW-U by MME and SGW-C) . The ULCL PSA is kept during the mobility procedure. The PDN reactivation may be triggered by the combined PGW-C+SMF after the mobility procedure is completed.

The reactivation may not be triggered for each mobility procedure as long as the latency is acceptable between the target site and the ULCL PSA1. The original ULCL PSA is removed together with the PDN connection release (triggered due to PDN reactivation) , then during the PDN connection re-establishment, a new ULCL PSA can be inserted in the target site as described previously with reference to FIG. 9.

Hereinafter, exemplary signaling sequence diagram of ULCL changing after HO from EPS to 5GS will be described with reference to FIG. 13, in which the methods 400～800 at various entities according to the first exemplary embodiment of the present disclosure are applied.

In the exemplary signaling sequence diagram of FIG. 13, an MME is shown as an example of the first mobility management entity, an AMF is shown as an example of the second mobility management entity, an SGW-C is shown as an example of the first control plane entity, a combined PGW-C and SMF is shown as an example of the second control plane entity and may be represented as (combined) PGW-C+SMF, an SGW-U is shown an example of the first user plane entity, a ULCL PSA1 is shown as an example of the ULCL function entity, a UPF (PSA0) is shown as an example of the second user plane entity. As previously described, the SGW-U and the ULCL PSA1 are collocated, which may be represented as (collocated) ULCL PSA1+SGW-U.

It should be noted that the description below mainly focuses on signaling related to the methods 400～800, and some other signaling is not described in detail to avoid obscuring the principle of the present disclosure. In FIG. 13, modification on the signaling related to the methods 400～800 is shown in Bold Italics, in which e.g., Signaling S13_4, S13_5, S13_10, S13_17, S13_23, and PDN connection reestablishment related signaling (referring to S9_3, S9_5～S9_10 and S9_12 in FIG. 9) are involved.

The exemplary signaling sequence diagram of FIG. 13 is applied to the HO from EPS to 5GS scenario, details of which follows the procedure as per Clause 4.11.1.2.2 of 3GPP TS23.502 v16.6.0 (which is thus incorporated herein by reference in its entirety) and the following deviation:

In S13_4～S13_5, in order to keep the ULCL PSA1 after HO to 5GS, the combined PGW-C+SMF triggers a PFCP Session Modification Request message to the ULCL PSA1. And the ULCL PSA1 returns the allocated N3 tunnel information (e.g., N3 ULCL F-TEID) in the PDCP Session Modification Response message to the combined PGW-C+SMF.

In S13_10, the combined PGW-C+SMF receives the NG-RAN N3 Tunnel information (e.g., N3 NG-RAN F-TEID) from the AMF, then triggers PFCP session modification to update the ULCL PSA1 with the NG-RAN N3 tunnel information (e.g., N3 NG-RAN F-TEID) .

In S13_17, when the combined PGW-C+SMF receives the HO Complete Indication from the AMF, the combined PGW-C+SMF triggers PFCP session modification to the ULCL PSA1 which switches the DL traffic to the NG-RAN.

In S13_22, the resource cleanup in EPC is performed after the completion of the HO from EPS to 5GS.

In S13_23, based on the UE location and/or the service information, the combined PGW-C+SMF determines to change the UPF anchor either by the PDU session reactivation (referring to Clause 4.3.5.1 of 3GPP TS 23.502 v16.6.0, which is thus incorporated herein by reference in its entirety) or ULCL change (referring to Clause 4.3.5.7 of 3GPP TS 23.502 v16.6.0 which is thus incorporated herein by reference in its entirety) in 5GC.

In the current standard (3GPP TS 23.502 v16.6.0) , the ULCL function is released at the HO from 5GS to EPS, and the edge service through the ULCL is discontinued immediately. In a second embodiment of the present disclosure, it is proposed that the ULCL function may be kept in the data path at the HO from 5GS to EPS, so that the edge service through the ULCL can be continued until PDN reactivation is triggered.

Hereinafter, a method 1400 for ULCL keeping that is performed at a second control plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 14. It should be understood that the second control plane entity may be any node that can be configured to perform the method 1400 as described below, including a virtualized entity that may be implemented on cloud..

The method 1400 may be performed in a case where handover from a 5GS to an EPS is required.

As shown in FIG. 14, in order to keep the ULCL function entity after HO from 5GS to EPS, the second control plane entity that supports selection of a first user plane entity and a ULCL function entity may trigger first session modification to a ULCL function entity in step S1401, so as to establish a user plane tunnel for each EPS bearer.

Thus in step S1403, the second control plane entity may receive, from the ULCL function entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address may be used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address may be used for the second user plane entity to transmit DL traffic to the ULCL function entity.

The second address may be an S5-U ULCL F-TEID that is transmitted in a PFCP Session Modification Response message from the ULCL function entity, and the fourth address may be a N9 ULCL F-TEID that is transmitted in the PFCP Session Modification Response message from the ULCL function entity.

In the method 1400, the second control plane entity may also trigger second session modification to a second user plane entity.

Then, the second control plane entity may receive, from the second user plane entity, a third address, that is allocated to the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity.

The third address may be an N9 PSA F-TEID that is received in a PFCP Session Modification Response message from the second user plane entity.

In the method 1400, the second control plane entity may transmit the received second address to a mobility management entity.

The second control plane entity may receive, from the first control plane entity, an eighth address that is allocated to the first user plane entity.

The eighth address may be an S5/S8-U SGW F-TEID that is transmitted in a PFCP Session Modification Request message to the ULCL function entity.

Then, the second control plane entity may transmit, to the ULCL function entity, the received eighth address for the ULCL function entity to transmit DL traffic to the first user plane entity and the received third address for the ULCL function entity to transmit UL traffic to the second user plane entity.

The third address may be an N9 PSA F-TEID that is transmitted in a PFCP Session Modification Request message to the ULCL function entity, and the eighth address is an S5/S8-U SGW F-TEID that is transmitted in the PFCP Session Modification Request message to the ULCL function entity.

The second control plane entity may transmit, to the second user plane entity, the received fourth address for the second user plane entity to transmit DL traffic to the ULCL function entity.

The fourth address may be the N9 ULCL F-TEID that is transmitted in a PFCP Session Modification Request message to the second user plane entity.

Similarly, when the second control plane entity determines to trigger the PDN reactivation (including PDN connection release and PDN connection reestablishment) based on at least one of UE location and service information, the second control plane entity may transmit, to the ULCL function entity, an indication of releasing the session between the ULCL function entity and the first user plane entity.

The second control plane entity may then perform step S501 as previously described during PDN reactivation to perform the PDN connection reestablishment to insert another ULCL function entity, in particular, to insert another ULCL function entity collocated with another first user plane entity, e.g., in order to obtain better user experience.

In an exemplary embodiment, the mobility management entity may include an AMF entity, the first control plane entity may include a SGW-C entity, the second control plane entity may include a combined PGW-C and SMF entity, the first user plane entity may include a SGW-U entity, the ULCL function entity may include a ULCL PSA entity, and the second user plane entity may include a PSA entity.

Hereinafter, a method 1500 for ULCL keeping that is performed at a ULCL function entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 15. It should be understood that the ULCL function entity may be any node that can be configured to perform the method 1500 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 1500 at the ULCL function entity at least partly corresponds to the method 1400 at the second control plane entity. Thus, some description of the method 1500 may refer to that of method 1400 as previously described, and thus will be omitted here for simplicity.

The method 1500 may be performed in a case where handover from a 5GS to an EPS is required.

As shown in FIG. 15, in step S1501, the ULCL function entity may receive, from a second control plane entity, a trigger of first session modification for the ULCL function entity.

Then in step S1503, the ULCL function entity may transmit, to the second control plane entity, a second address and a fourth address allocated to the ULCL function entity.

The second address may be used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address may be used for the second user plane entity to transmit DL traffic to the ULCL function entity.

The second address may be an S5-U ULCL F-TEID that is transmitted in a PFCP Session Modification Response message to the second control plane entity, and the fourth address may be an N9 ULCL F-TEID that is transmitted in the PFCP Session Modification Response message to the second control plane entity.

The ULCL function entity may receive a third address and an eighth address from the second control plane entity.

The third address may be allocated to the second user plane entity, and forwarded from the second user plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the second user plane entity.

The eighth address may be allocated to the first user plane entity, and forwarded from the first control plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the first user plane entity.

The third address may be an N9 PSA F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity, and the eighth address may be an S5/S8-U SGW F-TEID that is received in the PFCP Session Modification Request message from the second control plane entity.

Similarly, when the second control plane entity determines to trigger the PDN reactivation (including PDN connection release and PDN connection reestablishment) based on at least one of UE location and service information, the ULCL function entity may receive, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity; and then release the session between the ULCL function entity and the target first user plane entity.

Hereinafter, a method 1600 for ULCL keeping that is performed at a second user plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 16. It should be understood that the second user plane entity may be any node that can be configured to perform the method 1600 as described below, including a virtualized entity that may be implemented on cloud.

It should be understood that the method 1600 at the second user plane entity at least partly corresponds to the method 1400 at the second control plane entity. Thus, some description of the method 1600 may refer to that of method 1400 as previously described, and thus will be omitted here for simplicity.

The method 1600 may be performed in a case where handover from a 5GS to an EPS is required.

As shown in FIG. 16, in step S1601, the second user plane entity may transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity.

Then in step S1603, the second user plane entity may receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity and forwarded from the ULCL function entity by the second control plane entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

The third address may be an N9 PSA F-TEID that is transmitted in a PFCP Session Modification Response message to the second control plane entity.

The fourth address may be an N9 ULCL F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity.

Hereinafter, exemplary signaling sequence diagram of ULCL changing after HO from 5GS to EPS will be described with reference to FIG. 17, in which the methods 400～800 at various entities according to the first exemplary embodiment of the present disclosure are applied.

In the exemplary signaling sequence diagram of FIG. 17, an AMF is shown as an example of the mobility management entity, an SGW-C is shown as an example of the first control plane entity, a combined PGW-C and SMF is shown as an example of the second control plane entity and may be represented as (combined) PGW-C+SMF, an SGW-U is shown an example of the first user plane entity, a ULCL PSA1 is shown as an example of the ULCL function entity, a UPF (PSA0) is shown as an example of the second user plane entity. It should be understood that in 5GS, the ULCL PSA1 is not required to be collocated with the SGW-U. After the HO from 5GS to EPS is completed, the SGW-U and the ULCL PSA1 are collocated during the PDN connection reestablishment.

It should be noted that the description below mainly focuses on signaling related to the methods 400～800, and some other signaling is not described in detail to avoid obscuring the principle of the present disclosure. In FIG. 17, modification on the signaling related to the methods 1400～1600 is shown in Bold Italics, in which e.g., Signaling S17_3, S17_4, S17_20, S17_21, and PDN connection reestablishment related signaling (referring to S9_3, S9_5～S9_10 and S9_12 in FIG. 9) are involved.

The exemplary signaling sequence diagram of FIG. 17 is applied to the HO from 5GS to EPS scenario, details of which follows the procedure as per Clause 4.11.1.2.1 of 3GPP TS23.502 v16.6.0 (which is thus incorporated herein by reference in its entirety) and the following deviation:

In S17_3, in order to keep the ULCL PSA1 after the HO to EPS, the combined PGW-C+SMF triggers PFCP session modification to the ULCL PSA1 to establish the user plane tunnel for each EPS bearer. The ULCL PSA1 need establish both S5-U and N9 tunnels for each EPS bearer. The S5-U tunnel is used to receive the UL traffic from the SGW-U, and the N9 tunnel is used to receive the DL traffic from the UPF (PSA0) . The ULCL PSA1 returns the established user plane tunnel (both S5-U and N9) information (e.g., S5-U ULCL F-TEID and N9 ULCL F-TEID) to the combined PGW-C+SMF.

Note (S17 3) :

In the current 3GPP standard as per Clause 4.11.1.2.1 of 3GPP TS 23.502 v16.6.0 (which is thus incorporated herein by reference in its entirety) , the combined PGW-C+SMF only sends PFCP session modification to UPF (PSA0) to establish the user plane tunnel for each EPS bearer.

In S17_4, the combined PGW-C+SMF triggers PFCP session modification to the UPF (PSA0) to establish the N9 user plane tunnel for each EPS bearer. The UPF (PSA0) returns the established N9 tunnel information (e.g., N9 PSA0 F-TEID) to the combined PGW-C+SMF.

In S17_5, the combined PGW-C+SMF returns to the AMF with the EPS bearer contexts (e.g., S5-U ULCL F-TEID) corresponding to the S5-U tunnel (s) established by the ULCL PSA1.

Note (S17 5) :

In the current standard as per Clause 4.11.1.2.1 of 3GPP TS23.502 v16.6.0, the combined PGW-C+SMF returns to the AMF with the EPS bearer contexts corresponding to the user plane tunnel (s) established by UPF (PSA0) .

In S17_6～S17_19, the same procedure is performed as steps 3～14a in Figure 4.11.1.2.1-1 of 3GPP TS23.502 v16.6.0 (which is thus incorporated herein by reference in its entirety) .

In S17_20, the combined SMF+PGW sends PFCP session modification to the ULCL PSA1 with the S5/S8-U SGW F-TEID and the N9 PSA0 F-TEID (corresponding to the tunnel established by the UPF (PSA0) at S17_4) , the ULCL PSA1 switches the DL traffic to the SGW-U, and switches the UL traffic to the UPF PSA0.

In S17_21, the combined SMF+PGW sends PFCP session modification to the UPF (PSA0) with the N9 ULCL F-TEID (corresponding to the tunnel established by ULCL PSA1 at S17_3) and the UPF (PSA0) switches the DL traffic to the ULCL PSA1.

In S17_22～S17_23, the same procedure is performed as steps 16～17 in Figure 4.11.1.2.1-1 of 3GPP TS23.502 v16.6.0 (which is thus incorporated herein by reference in its entirety) .

In S17_24, the combined PGW-C+SMF determines to trigger PDN connection reactivation (including PDN connection release and PDN connection reestablishment) based on the UE location and/or the service information as per S11A_12～ S11A_19 as previously described with reference to FIG. 11A, description of which is thus omitted herein for simplicity.

An exemplary traffic flow between SGW-U and ULCL PSA1 after the HO from 5GS to EPS before PDN reactivation according to the second exemplary embodiment of the present disclosure is shown in FIG. 18.

Hereinafter, a structure of a first control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 19. FIG. 19 schematically shows a block diagram of the first control plane entity 1900 according to the first exemplary embodiment of the present disclosure. The first control plane entity 1900 in FIG. 19 may perform the method 400 as described previously with reference to FIG. 4. Accordingly, some detailed description on the first control plane entity 2000 may refer to the corresponding description of the method 400 in FIG. 4 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 19, the first control plane entity 1900 may include a determination unit 1901 and a transmitting unit 1903.

The determination unit 1901 may determine that a second control plane entity selected by the first control plane entity supports selection of a first user plane entity and a ULCL function entity.

The transmitting unit 1903 may transmit, to the second control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.

In an exemplary embodiment, the indication may include a first address, that is to be allocated to a first user plane entity, for a ULCL function entity to transmit DL traffic to the first user plane entity.

In an exemplary embodiment, the first control plane entity 1900 may further include a receiving unit (not shown) , which may be configured to receive, from the second control plane entity, a second address, that is allocated to a ULCL function entity and transmitted by the ULCL function entity to the second control plane entity, for a first user plane entity to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the first control plane entity 1900 may further include a selection unit (not shown) , which may be configured to select, based on the received second address, the first user plane entity; and transmitting the second address to the first user plane entity for the first user plane entity to transmit the UL traffic to the ULCL function entity.

In an exemplary embodiment, the transmitting unit 1903 may further be configured to transmit the second address to a first mobility management entity.

In an exemplary embodiment, the indication is transmitted in a Create Session Request message, and the first address is an Internal F-TEID that is transmitted in an S5/S8-U SGW F-TEID IE in the Create Session Request message.

In an exemplary embodiment, the second address is an S5-U ULCL F-TEID that is received in an S5/S8-U PGW F-TEID IE in a Create Session Response message from the second control plane entity, transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message to the mobility management entity, and transmitted in a UL remote FAR in a PFCP Session Establishment Request message to the first user plane entity.

Hereinafter, a structure of a first control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 20. FIG. 20 schematically shows a block diagram of the first control plane entity 2000 according to the first exemplary embodiment of the present disclosure. The first control plane entity 2000 in FIG. 20 may perform the method 400 as described previously with reference to FIG. 4. Accordingly, some detailed description on the first control plane entity 2000 may refer to the corresponding description of the method 400 in FIG. 4 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 20, the first control plane entity 2000 includes at least one processor 2001 and at least one memory 2003. The at least one processor 2001 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 2003 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 2003 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 2003 stores instructions executable by the at least one processor 2001. The instructions, when loaded from the at least one memory 2003 and executed on the at least one processor 2001, may cause the first control plane entity 2000 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 4 with reference to the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a second control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 21. FIG. 21 schematically shows a block diagram of the second control plane entity 2100 according to the first exemplary embodiment of the present disclosure. The second control plane entity 2100 in FIG. 21 may perform the method 500 as described previously with reference to FIG. 5. Accordingly, some detailed description on the second control plane entity 2200 may refer to the corresponding description of the method 500 in FIG. 5 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As previously described, the second control plane entity supports selection of a first user plane entity and a ULCL function entity.

As shown in FIG. 21, the second control plane entity 2100 may include an insertion unit 2101, which may be configured to perform a process of inserting a ULCL function entity during a connection establishment.

In an exemplary embodiment, the insertion unit 2101 may include: a determination unit (not shown) and a session establishment unit (not shown) .

The determination unit may be configured to determine to insert a ULCL function entity.

The session establishment unit may be configured to perform session establishment with the ULCL function entity.

In an exemplary embodiment, the ULCL function entity is determined to be inserted based on at least one of: a location of a UE or service information related to the ULCL function entity.

In an exemplary embodiment, the service information includes at least one of: a DNAI, or a traffic forwarding rule for the ULCL function entity.

In an exemplary embodiment, the insertion unit 2101 may further include a receiving unit (not shown) , which may be configured to receive, from a first control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.

In an exemplary embodiment, the insertion unit may further include a trigger unit (not shown) , which may be configured to trigger session establishment to a second user plane entity. And the receiving unit may be further configured to receive, from the second user plane entity, a third address, that is allocated to the second user plane entity.

In an exemplary embodiment, the inserting unit 2101 may further include a transmitting unit (not shown) , which may be configured to transmit, to the ULCL function entity, a session establishment request message, and receive, from the ULCL function entity, a session establishment response message,

The session establishment request message may include: the first address, that is received from the first control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity; the third address, that is received from the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity; and the traffic forwarding rule for the ULCL function entity,

The session establishment response message may include: a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity; and a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the session establishment unit may be further configured to transmit, to the second user plane entity, the received fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the session establishment unit may be further configured to transmit, to the first control plane entity, the received second address that is allocated to the ULCL function entity.

In an exemplary embodiment, the first control plane entity includes an SGW-C entity, the second control plane entity includes a combined PGW-C and SMF entity, the first user plane entity includes an SGW-U entity, the ULCL function entity includes a ULCL PSA entity, and the second user plane entity includes a PSA entity.

In an exemplary embodiment, the receiving unit may be further configured to receive, from another first control plane entity, as a target first control plane entity, a fifth address that is allocated to another first user plane entity, as a target first user plane entity, and transmitted by the target first user plane entity to the target first control plane entity; and transmitting the fifth address to the ULCL function entity for the ULCL function entity to establish a session with the target first user plane entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity.

In an exemplary embodiment, the transmitting unit may be further configured to transmit, to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity.

In an exemplary embodiment, the insertion unit 2101 may be further configured to re-perform the process of inserting a ULCL function entity for a new connection establishment to establish another ULCL function entity.

In an exemplary embodiment, the transmitting unit may be further configured to: transmit, to the ULCL function entity, a session modification request message. And the receiving unit may be further configured to receive, from the ULCL function entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the receiving unit may be further configured to receive, from a second mobility management entity, a seventh address that is allocated to the access node. And the transmitting unit may be further configured to transmit the received seventh address to the ULCL function entity for the ULCL function entity to transmit DL traffic to the access node.

In an exemplary embodiment, the receiving unit may be further configured to receive a handover complete indication from the second mobility management entity. And the trigger unit may be further configured to trigger session modification to the ULCL function entity for the ULCL function entity to switch the DL traffic to the access node based on the received seventh address.

In an exemplary embodiment, the seventh address is an N3 NG-RAN F-TEID that is received in an Nsmf_PDU Session_Update_SM Context Request message, and is transmitted in a PFCP Session Modification Request message.

Hereinafter, a structure of a second control plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 22. FIG. 22 schematically shows a block diagram of the second control plane entity 2200 according to the first exemplary embodiment of the present disclosure. The second control plane entity 2200 in FIG. 22 may perform the method 500 as described previously with reference to FIG. 5. Accordingly, some detailed description on the second control plane entity 2200 may refer to the corresponding description of the method 500 in FIG. 5 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 22, the second control plane entity 2200 includes at least one processor 2201 and at least one memory 2203. The at least one processor 2201 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 2203 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 2203 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 2203 stores instructions executable by the at least one processor 2201. The instructions, when loaded from the at least one memory 2203 and executed on the at least one processor 2201, may cause the first control plane entity 2200 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 5 with reference to the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a ULCL function entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 23. FIG. 23 schematically shows a block diagram of the ULCL function entity 2300 according to the first exemplary embodiment of the present disclosure. The ULCL function entity 2300 in FIG. 23 may perform the method 500 as described previously with reference to FIG. 6. Accordingly, some detailed description on the ULCL function entity 2300 may refer to the corresponding description of the method 600 in FIG. 6 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 23, the ULCL function entity 2300 may include a receiving unit 2301 and a transmitting unit 2303.

The receiving unit 2301 may be configured to receive a session establishment request message from a second control plane entity that supports selection of a first user plane entity and a ULCL function entity.

The transmitting unit 2303 may be configured to transmit, to the second control plane entity, a session establishment response message.

In an exemplary embodiment, the receiving unit 2301 may be further configured to receive, from the second control plane entity, a fifth address, that is allocated to another first user plane entity, as a target first user plane entity, for the ULCL function entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity, wherein the fifth address was received by the target first control plane entity from the target first user plane entity and transmitted to the second control plane entity.

In an exemplary embodiment, the receiving unit 2301 may be further configured to receive, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity.

The ULCL function entity may further include a releasing unit (not shown) , which may be configured to release the session between the ULCL function entity and the target first user plane entity.

In an exemplary embodiment, the receiving unit 2301 may be further configured to receive a session modification request message from the second control plane entity. And the transmitting unit 2303 may be further configured to transmit, to the second control plane entity, a session modification response message, which includes a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.

In an exemplary embodiment, the receiving unit 2301 may be further configured to receive, from the second control plane entity, a seventh address, that is allocated to the access node and transmitted to the second control plane entity from a second mobility management entity, for the ULCL function entity to transmit DL traffic to the access node.

In an exemplary embodiment, the transmitting unit 2303 may be further configured to: switching the DL traffic to the access node based on the received seventh address, in a case where a handover complete indication is received by the second control plane entity from the second mobility management entity.

Hereinafter, a structure of a ULCL function entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 24. FIG. 24 schematically shows a block diagram of the ULCL function entity 2400 according to the first exemplary embodiment of the present disclosure. The ULCL function entity 2400 in FIG. 24 may perform the method 600 as described previously with reference to FIG. 6. Accordingly, some detailed description on the ULCL function entity 2400 may refer to the corresponding description of the method 600 in FIG. 6 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 24, the ULCL function entity 2400 includes at least one processor 2401 and at least one memory 2403. The at least one processor 2401 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 2403 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 2403 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 2403 stores instructions executable by the at least one processor 2401. The instructions, when loaded from the at least one memory 2403 and executed on the at least one processor 2401, may cause the first control plane entity 2400 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 6 with reference to the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a first user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 25. FIG. 25 schematically shows a block diagram of the first user plane entity 2500 according to the first exemplary embodiment of the present disclosure. The first user plane entity 2500 in FIG. 25 may perform the method 700 as described previously with reference to FIG. 7. Accordingly, some detailed description on the first user plane entity 2500 may refer to the corresponding description of the method 700 in FIG. 7 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 25, the first user plane entity 2500 may include a receiving unit 2501, which may be configured to receive, from a first control plane entity, a second address, that is allocated to a ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, wherein the second address was received by the first control plane entity from the ULCL function entity via the second control plane entity.

Hereinafter, a structure of a first user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 26. FIG. 26 schematically shows a block diagram of the first user plane entity 2600 according to the first exemplary embodiment of the present disclosure. The first user plane entity 2600 in FIG. 26 may perform the method 700 as described previously with reference to FIG. 7. Accordingly, some detailed description on the first user plane entity 2600 may refer to the corresponding description of the method 700 in FIG. 7 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 26, the first user plane entity 2600 includes at least one processor 2601 and at least one memory 2603. The at least one processor 2601 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 2603 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 2603 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 2603 stores instructions executable by the at least one processor 2601. The instructions, when loaded from the at least one memory 2603 and executed on the at least one processor 2601, may cause the first control plane entity 2600 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 7 with reference to the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a second user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 27. FIG. 27 schematically shows a block diagram of the second user plane entity 2700 according to the first exemplary embodiment of the present disclosure. The second user plane entity 2700 in FIG. 27 may perform the method 800 as described previously with reference to FIG. 8. Accordingly, some detailed description on the second user plane entity 2700 may refer to the corresponding description of the method 800 in FIG. 8 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 27, the second user plane entity 2700 may include a transmitting unit 2701 and a receiving unit 2703.

The transmitting unit 2701 may be configured to transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity.

The receiving unit 2703 may be configured to receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

Hereinafter, a structure of a second user plane entity according to the first exemplary embodiment of the present disclosure will be described with reference to FIG. 28. FIG. 28 schematically shows a block diagram of the second user plane entity 2800 according to the first exemplary embodiment of the present disclosure. The second user plane entity 2800 in FIG. 28 may perform the method 800 as described previously with reference to FIG. 8. Accordingly, some detailed description on the second user plane entity 2800 may refer to the corresponding description of the method 800 in FIG. 8 and the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 28, the second user plane entity 2800 includes at least one processor 2801 and at least one memory 2803. The at least one processor 2801 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 2803 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 2803 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 2803 stores instructions executable by the at least one processor 2801. The instructions, when loaded from the at least one memory 2803 and executed on the at least one processor 2801, may cause the first control plane entity 2800 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 8 with reference to the signaling sequence diagrams of FIGS. 9, 11A～11B, and 13 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a second control plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 29. FIG. 29 schematically shows a block diagram of the second control plane entity 2900 according to the second exemplary embodiment of the present disclosure. The second control plane entity 2900 in FIG. 29 may perform the method 1400 as described previously with reference to FIG. 14. Accordingly, some detailed description on the second control plane entity 2900 may refer to the corresponding description of the method 1400 in FIG. 14 and the signaling sequence diagram of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 29, the second control plane entity 2900 may include a triggering unit 2901 and a receiving unit 2903.

The triggering unit 2901 may be configured to trigger first session modification to a ULCL function entity.

The receiving unit 2903 may be configured to receive, from the ULCL function entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the triggering unit 2901 may be further configured to trigger second session modification to the second user plane entity. And the receiving unit 2903 may be further configured to receive, from the second user plane entity, a third address, that is allocated to the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity.

In an exemplary embodiment, the second control plane entity 2900 may further include a transmitting unit (not shown) , which may be configured to transmit the second address to a mobility management entity.

In an exemplary embodiment, the receiving unit 2903 may be further configured to receive, from a first control plane entity, an eighth address that is allocated to the first user plane entity.

The transmitting unit may be further configured to transmit, to the ULCL function entity, the eighth address for the ULCL function entity to transmit DL traffic to the first user plane entity and the third address for the ULCL function entity to transmit UL traffic to the second user plane entity.

In an exemplary embodiment, the transmitting unit may be further configured to transmit, to the second user plane entity, the fourth address for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the transmitting unit may be further configured to transmit to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the first user plane entity.

In an exemplary embodiment, the second control plane entity 2900 may further include an insertion unit (not shown) , which may be configured to insert a ULCL function entity as previously described with reference to FIG. 9.

Hereinafter, a structure of a second control plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 30. FIG. 30 schematically shows a block diagram of the second control plane entity 3000 according to the second exemplary embodiment of the present disclosure. The second control plane entity 3000 in FIG. 30 may perform the method 1400 as described previously with reference to FIG. 14. Accordingly, some detailed description on the second control plane entity 3000 may refer to the corresponding description of the method 1400 in FIG. 14 and the signaling sequence diagram of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 30, the second control plane entity 3000 includes at least one processor 3001 and at least one memory 3003. The at least one processor 3001 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 3003 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 3003 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 3003 stores instructions executable by the at least one processor 3001. The instructions, when loaded from the at least one memory 3003 and executed on the at least one processor 3001, may cause the first control plane entity 3000 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 14 with reference to the signaling sequence diagram of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a ULCL function entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 31. FIG. 31 schematically shows a block diagram of the ULCL function entity 3100 according to the second exemplary embodiment of the present disclosure. The ULCL function entity 3100 in FIG. 31 may perform the method 1500 as described previously with reference to FIG. 15. Accordingly, some detailed description on the ULCL function entity 3100 may refer to the corresponding description of the method 1500 in FIG. 15 and the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 31, the ULCL function entity 3100 may include a receiving unit 3101 and a transmitting unit 3103.

The receiving unit 3101 may be configured to receive, from a second control plane entity, a trigger of first session modification for the ULCL function entity.

The transmitting unit 3103 may be configured to transmit, to the second control plane entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.

In an exemplary embodiment, the receiving unit 3101 may be further configured to receive a third address and an eighth address from the second control plane entity, wherein the third address is allocated to the second user plane entity, and forwarded from the second user plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the second user plane entity, and the eighth address is allocated to the first user plane entity, and forwarded from the first control plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the first user plane entity.

In an exemplary embodiment, the receiving unit 3101 may be further configured to receive, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the first user plane entity; and releasing the session between the ULCL function entity and the first user plane entity.

Hereinafter, a structure of a ULCL function entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 32. FIG. 32 schematically shows a block diagram of the ULCL function entity 3200 according to the second exemplary embodiment of the present disclosure. The ULCL function entity 3200 in FIG. 32 may perform the method 1500 as described previously with reference to FIG. 15. Accordingly, some detailed description on the ULCL function entity 3200 may refer to the corresponding description of the method 1500 in FIG. 15 and the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 32, the ULCL function entity 3200 includes at least one processor 3201 and at least one memory 3203. The at least one processor 3201 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 3203 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 3203 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 3203 stores instructions executable by the at least one processor 3201. The instructions, when loaded from the at least one memory 3203 and executed on the at least one processor 3201, may cause the first control plane entity 3200 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 15 with reference to the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

Hereinafter, a structure of a second user plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 33. FIG. 33 schematically shows a block diagram of the second user plane entity 3300 according to the second exemplary embodiment of the present disclosure. The second user plane entity 3300 in FIG. 33 may perform the method 1600 as described previously with reference to FIG. 16. Accordingly, some detailed description on the ULCL function entity 3300 may refer to the corresponding description of the method 1600 in FIG. 16 and the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 33, the second user plane entity 3300 may include a transmitting unit 3301 and a receiving unit 3303.

The transmitting unit 3301 may be configured to transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a ULCL function entity to transmit UL traffic to the second user plane entity

The receiving unit 3303 may be configured to receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity and forwarded from the ULCL function entity by the second control plane entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.

Hereinafter, a structure of a second user plane entity according to the second exemplary embodiment of the present disclosure will be described with reference to FIG. 34. FIG. 34 schematically shows a block diagram of the second user plane entity 3400 according to the second exemplary embodiment of the present disclosure. The second user plane entity 3400 in FIG. 34 may perform the method 1600 as described previously with reference to FIG. 16. Accordingly, some detailed description on the ULCL function entity 3400 may refer to the corresponding description of the method 1600 in FIG. 16 and the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

As shown in FIG. 34, the second user plane entity 3400 includes at least one processor 3401 and at least one memory 3403. The at least one processor 3401 includes e.g., any suitable CPU (Central Processing Unit) , microcontroller, DSP (Digital Signal Processor) , etc., capable of executing computer program instructions. The at least one memory 3403 may be any combination of a RAM (Random Access Memory) and a ROM (Read Only Memory) . The at least one processor memory 3403 may also include persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, or solid state memory or even remotely mounted memory.

The at least one memory 3403 stores instructions executable by the at least one processor 3401. The instructions, when loaded from the at least one memory 3403 and executed on the at least one processor 3401, may cause the first control plane entity 3400 to perform the actions, e.g., of the procedures as described earlier respectively in conjunction with FIG. 16 with reference to the signaling sequence diagrams of FIG. 17 as previously discussed, and thus will be omitted here for simplicity.

The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, e.g., a non-transitory computer readable storage medium, an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and a hard drive. The computer program product includes a computer program.

The computer program includes: code/computer readable instructions, which when executed by the at least one processor 2001 causes the first control plane entity 2000 to perform the actions, e.g., of the procedure described earlier in conjunction with FIG. 4; or code/computer readable instructions, which when executed by the at least one processor 2201 causes the second control plane entity 2200 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 5; or code/computer readable instructions, which when executed by the at least one processor 2401 causes the ULCL function entity 2400 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 6; code/computer readable instructions, which when executed by the at least one processor 2601 causes the first user plane entity 2600 to perform the actions, e.g., of the procedure described earlier in conjunction with FIG. 7; or code/computer readable instructions, which when executed by the at least one processor 2801 causes the second user plane entity 2800 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 8; or code/computer readable instructions, which when executed by the at least one processor 3001 causes the second control plane entity 3000 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 14; or code/computer readable instructions, which when executed by the at least one processor 3201 causes the ULCL function entity 3200 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 15; or code/computer readable instructions, which when executed by the at least one processor 3401 causes the second user plane entity 3400 to perform the actions, e.g., of the procedures described earlier respectively in conjunction with FIG. 16.

The computer program product may be configured as a computer program code structured in computer program modules. The computer program modules could essentially perform the actions of the flow illustrated in any of FIGS. 4 to 8 and 14 to 16.

The processor may be a single CPU (Central processing unit) , but could also include two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also include board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may include a non-transitory computer readable storage medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories.

The present disclosure has been described above with reference to embodiments thereof. It should be understood that various modifications, alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the present disclosure. Therefore, the scope of the present disclosure is not limited to the above particular embodiments but only defined by the claims as attached.

Claims

A method (400) at a first control plane entity, comprising:

determining (S401) that a second control plane entity selected by the first control plane entity supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity; and

transmitting (S403) , to the second control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.
The method (400) of claim 1, wherein the indication comprises a first address, that is to be allocated to a first user plane entity, for a ULCL function entity to transmit Downlink ‘DL’ traffic to the first user plane entity.
The method (400) of claim 1 or 2, further comprising:

receiving, from the second control plane entity, a second address, that is allocated to a ULCL function entity and transmitted by the ULCL function entity to the second control plane entity, for a first user plane entity to transmit UL traffic to the ULCL function entity.
The method (400) of claim 3, further comprising:

selecting, based on the received second address, the first user plane entity; and

transmitting the second address to the first user plane entity for the first user plane entity to transmit the UL traffic to the ULCL function entity.
The method (400) of claim 4, further comprising:

transmitting the second address to a first mobility management entity.
The method (400) of any of claims 1 to 5, wherein the first user plane entity and the ULCL function entity are collocated.
The method (400) of any of claims 2 to 6, wherein

the indication is transmitted in a Create Session Request message, and

the first address is an Internal Full Qualified-Tunnel Endpoint Identifier ‘F-TEID’ that is transmitted in an S5/S8-U SGW F-TEID Information Element ‘IE’ in the Create Session Request message.
The method (400) of any of claims 3 to 7, wherein

the second address is an S5-U ULCL F-TEID that is received in an S5/S8-U PGW F-TEID IE in a Create Session Response message from the second control plane entity, transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message to the mobility management entity, and transmitted in a UL remote Forwarding Action Rule ‘FAR’ in a Packet Forwarding Control Protocol ‘PFCP’ Session Establishment Request message to the first user plane entity.
The method (400) of any of claims 5 to 8, wherein

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity,

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity, and

the first mobility management entity comprises a Mobility Management Entity ‘MME’ .
A method (500) , at a second control plane entity that supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity, comprising:

performing (S501) a process of inserting a ULCL function entity during a connection establishment.
The method (500) of claim 10, wherein said performing the process of inserting the ULCL function entity comprises:

determining to insert a ULCL function entity; and

performing session establishment with the ULCL function entity.
The method (500) of claim 10 or 11, wherein the ULCL function entity is determined to be inserted based on at least one of:

a location of a User Equipment ‘UE’ , or

service information related to the ULCL function entity.
The method (500) of claim 12, wherein the service information comprises at least one of:

a Data Network Access Identifier ‘DNAI’ , or

a traffic forwarding rule for the ULCL function entity.
The method (600) of claim 13, wherein the traffic forwarding rule for the ULCL function entity comprises routing contexts to local Data Network ‘DN’ for edge breakout by the ULCL function entity.
The method (500) of any of claims 10 to 14, wherein said performing the process of inserting the ULCL function entity further comprises:

receiving, from a first control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.
The method (500) of claim 15, wherein the indication comprises a first address, that is to be allocated to the first user plane entity, for the ULCL function entity to transmit Downlink ‘DL’ traffic to the first user plane entity.
The method (500) of any of claims 10 to 16, wherein said performing the session establishment with the ULCL function entity further comprises:

triggering session establishment to a second user plane entity; and

receiving, from the second user plane entity, a third address, that is allocated to the second user plane entity.
The method (500) of claim 17, wherein said performing the session establishment with the ULCL function entity further comprises:

transmitting, to the ULCL function entity, a session establishment request message; and

receiving, from the ULCL function entity, a session establishment response message,

wherein the session establishment request message comprises:

the first address, that is received from the first control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity,

the third address, that is received from the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity, and

the traffic forwarding rule for the ULCL function entity; and

wherein the session establishment response message comprises:

a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, and

a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (500) of claim 18, wherein said performing the session establishment with the ULCL function entity further comprises:

transmitting, to the second user plane entity, the received fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (500) of claim 18 or 19, wherein said performing the session establishment with the ULCL function entity further comprises:

transmitting, to the first control plane entity, the received second address that is allocated to the ULCL function entity.
The method (500) of any of claims 10 to 20, wherein the first user plane entity and the ULCL function entity are collocated.
The method (500) of any of claims 15 to 21, wherein

the indication is received in a Create Session Request message, and

the first address is an Internal Full Qualified-Tunnel Endpoint Identifier ‘F-TEID’ that is received in an S5/S8-U SGW F-TEID Information Element ‘IE’ of the Create Session Request message.
The method (500) of any of claims 18 to 22, wherein

the transmitted session establishment request message comprises a Packet Forwarding Control Protocol ‘PFCP’ Session Establishment Request message, which comprises:

a UL remote Forwarding Action Rule ‘FAR’ that is set to an N9 PSA F-TEID as the third address,

a DL remote FAR that is set to the Internal F-TEID as the first address, and

the traffic forwarding rule for the ULCL function entity.
The method (500) of any of claims 18 to 23, wherein the received session establishment response message comprises a PFCP Session Establishment Response message, which comprises: an S5-U ULCL F-TEID as the second address, and an N9 ULCL F-TEID as the fourth address.
The method (500) of any of claims 19 to 24, wherein

the fourth address is an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.
The method (500) of any of claims 20 to 25, wherein

the second address is an S5-U ULCL F-TEID that is transmitted in an S5/S8-U PGW F-TEID IE in a Create Session Response message.
The method (500) of any of claims 18 to 26, further comprising:

receiving, from another first control plane entity, as a target first control plane entity, a fifth address that is allocated to another first user plane entity, as a target first user plane entity, and transmitted by the target first user plane entity to the target first control plane entity; and

transmitting the fifth address to the ULCL function entity for the ULCL function entity to establish a session with the target first user plane entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity.
The method (500) of claim 27, wherein the fifth address is received in a case where the target first control plane entity receives the second address from a first mobility management entity, and transmits the second address to the target first user plane entity, wherein the second address was received by the first mobility management entity from the second control plane entity via the source first control plane entity.
The method (500) of claim 27 or 28, further comprising:

transmitting, to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity.
The method (500) of claim 29, further comprising:

re-performing the process of inserting a ULCL function entity for a new connection establishment to establish another ULCL function entity.
The method (500) of claim 27, wherein

the fifth address is a Target S5/S8-U SGW F-TEID that is received in a Modify Bearer Request message, and is transmitted in a DL remote FAR of a PFCP Session Modification Request message.
The method (500) of any of claims 10 to 31, further comprising:

transmitting, to the ULCL function entity, a session modification request message; and

receiving, from the ULCL function entity, a session modification response message, which comprises a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.
The method (500) of claim 32, wherein the session modification request message is transmitted in a case where handover from an Evolved Packet System ‘EPS’ to a 5G System ‘5GS’ is required.
The method (500) of claim 32 or 33, further comprising:

receiving, from a second mobility management entity, a seventh address that is allocated to the access node; and

transmitting the received seventh address to the ULCL function entity for the ULCL function entity to transmit DL traffic to the access node.
The method (500) of claim 34, further comprising:

receiving a handover complete indication from the second mobility management entity; and

triggering session modification to the ULCL function entity for the ULCL function entity to switch the DL traffic to the access node based on the received seventh address.
The method (500) of claim 35, further comprising:

re-performing the process of inserting a ULCL function entity for a new connection establishment to establish another ULCL function entity.
The method (500) of any of claims 32 to 36, wherein

the transmitted session modification request message comprises a PFCP Session Modification Request message, and

the received session modification response message comprises a PFCP Session Modification Response message, which comprises an N3 ULCL F-TEID as the sixth address.
The method (500) of any of claims 34 to 37, wherein

the seventh address is an N3 Next Generation-Radio Access Network ‘NG-RAN’ F-TEID that is received in an Nsmf_Protocol Data Unit ‘PDU’ Session_Update_Session Management ‘SM’ Context Request message, and is transmitted in a PFCP Session Modification Request message.
The method (500) of any of claims 35 to 38, wherein

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity,

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity,

the second user plane entity comprises a PSA entity,

the first mobility management entity comprises a Mobility Management Entity ‘MME’ , and

the second mobility management entity comprises an Access and Mobility Management Function ‘AMF’ entity.
A method (600) , at a Uplink Classifier ‘ULCL’ function entity, comprising:

receiving (S601) a session establishment request message from a second control plane entity that supports selection of a first user plane entity and a ULCL function entity; and

transmitting (S603) , to the second control plane entity, a session establishment response message.
The method (600) of claim 40, wherein

the session establishment request message comprises:

a first address, that is to be allocated by a first control plane entity to the first user plane entity, and is received from the first control plane entity via the second control plane entity, for the ULCL function entity to transmit DL traffic to the first user plane entity,

a third address, that is allocated to the second user plane entity, and is received from the second user plane entity via the second control plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity, and

a traffic forwarding rule for the ULCL function entity; and

the session establishment response message comprises:

a second address, that is allocated to the ULCL function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, and

a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (600) of claim 41, wherein the traffic forwarding rule for the ULCL function entity comprises routing contexts to local Data Network ‘DN’ for edge breakout by the ULCL function entity.
The method (600) of any of claims 40 to 42, wherein the ULCL function entity is collocated with the first user plane entity.
The method (600) of any of claims 41 to 43, wherein

the received session establishment request message comprises a Packet Forwarding Control Protocol ‘PFCP’ Session Establishment Request message, which comprises:

a UL remote Forwarding Action Rule ‘FAR’ that is set to an N9 PSA F-TEID as the third address,

a DL remote FAR IE that is set to the Internal F-TEID as the first address, and

the traffic forwarding rule for the ULCL function entity.
The method (600) of any of claims 41 to 44, wherein the transmitted session establishment response message comprises a PFCP Session Establishment Response message, which comprises: an S5-U ULCL F-TEID as the second address, and a N9 ULCL F-TEID as the fourth address.
The method (600) of any of claims 40 to 45, further comprising:

receiving, from the second control plane entity, a fifth address, that is allocated to another first user plane entity, as a target first user plane entity, for the ULCL function entity to switch the DL traffic to the target first user plane entity from the first user plane entity as a source first user plane entity, wherein the fifth address was received by the target first control plane entity from the target first user plane entity and transmitted to the second control plane entity.
The method (600) of claim 46, wherein the fifth address is received in a case where the target first control plane entity receives the second address from a first mobility management entity, and transmits the second address to the target first user plane entity, wherein the second address was received by the first mobility management entity from the second control plane entity via the source first control plane entity.
The method (600) of claim 46 or 47, further comprising:

receiving, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the target first user plane entity; and

releasing the session between the ULCL function entity and the target first user plane entity.
The method (600) of any of claims 46 to 48, wherein

the fifth address is a Target S5/S8-U SGW F-TEID that is received in a DL remote FAR of a PFCP Session Modification Request message.
The method (600) of any of claims 40 to 49, further comprising:

receiving a session modification request message from the second control plane entity; and

transmitting, to the second control plane entity, a session modification response message, which comprises a sixth address that is allocated to the ULCL function entity for an access node to transmit UL traffic to the ULCL function entity.
The method (600) of claim 50, wherein the session modification request message is received in a case where handover from an Evolved Packet System ‘EPS’ to a 5G System ‘5GS’ is required.
The method (600) of claim 50 or 51, further comprising:

receiving, from the second control plane entity, a seventh address, that is allocated to the access node and transmitted to the second control plane entity from a second mobility management entity, for the ULCL function entity to transmit DL traffic to the access node.
The method (600) of claim 52, further comprising:

switching the DL traffic to the access node based on the received seventh address, in a case where a handover complete indication is received by the second control plane entity from the second mobility management entity.
The method (600) of any of claims 50 to 53, wherein

the received session modification request message comprises a PFCP Session Modification Request message, and

the transmitted session modification response message comprises a PFCP Session Modification Response message, which comprises an N3 ULCL F-TEID as the sixth address.
The method (600) of any of claims 52 to 54, wherein

the seventh address is an N3 Next Generation-Radio Access Network ‘NG-RAN’ F-TEID that is received in a PFCP Session Modification Request message.
The method (600) of any of claims 52 to 55, wherein

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity,

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity,

the second user plane entity comprises a PSA entity,

the first mobility management entity is a Mobility Management Entity ‘MME’ , and

the second mobility management entity comprises an Access and Mobility Management Function ‘AMF’ entity.
A method (700) at a first user plane entity, comprising:

receiving (S701) , from a first control plane entity, a second address, that is allocated to a Uplink Classifier ‘ULCL’ function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, wherein the second address was received by the first control plane entity from the ULCL function entity via a second control plane entity.
The method (700) of claim 57, wherein

the second address is an S5-U ULCL F-TEID that is received in a UL remote FAR in a PFCP Session Modification Request message from the first control plane entity.
The method (700) of claim 57 or 58, wherein

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity, and

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity.
A method (800) at a second user plane entity, comprising:

transmitting (S801) , to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a Uplink Classifier ‘ULCL’ function entity to transmit UL traffic to the second user plane entity; and

receiving (S803) , from the second control plane entity, a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (800) of claim 60, wherein

the second control plane entity supports selection of a first user plane entity and a ULCL function entity.
The method (800) of claim 60 or 61, wherein

the first user plane entity and the ULCL function entity are collocated.
The method (800) of any of claims 60 to 62, wherein

the third address is an N9 PSA Full Qualified-Tunnel Endpoint Identifier ‘F-TEID’ that is transmitted in a Packet Forwarding Control Protocol ‘PFCP’ Session Establishment Response message, and

the fourth address is an N9 ULCL F-TEID that is transmitted in a DL remote FAR in a PFCP Session Modification Request message.
The method (800) of any of claims 60 to 63, wherein

the second user plane entity comprises a Protocol Data Unit Session Anchor ‘PSA’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity, and

the ULCL function entity comprises a ULCL PSA entity.
A method (1400) at a second control plane entity that supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity, comprising:

triggering (S1401) first session modification to a ULCL function entity; and

receiving (S1403) , from the ULCL function entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (1400) of claim 65, wherein the method is performed in a case where handover from a 5G System ‘5GS’ to an Evolved Packet System ‘EPS’ is required.
The method (1400) of claim 65 or 66, further comprising:

triggering second session modification to the second user plane entity; and

receiving, from the second user plane entity, a third address, that is allocated to the second user plane entity, for the ULCL function entity to transmit UL traffic to the second user plane entity.
The method (1400) of claim 67, further comprising:

transmitting the second address to a mobility management entity.
The method (1400) of claim 68, further comprising:

receiving, from a first control plane entity, an eighth address that is allocated to the first user plane entity; and

transmitting, to the ULCL function entity, the eighth address for the ULCL function entity to transmit DL traffic to the first user plane entity and the third address for the ULCL function entity to transmit UL traffic to the second user plane entity.
The method (1400) of claim 69, further comprising:

transmitting, to the second user plane entity, the fourth address for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (1400) of any of claims 65 to 70, wherein

the second address is an S5-U ULCL F-TEID that is received in a Packet Forwarding Control Protocol ‘PFCP’ Session Modification Response message from the ULCL function entity, and

the fourth address is a N9 ULCL F-TEID that is received in the PFCP Session Modification Response message from the ULCL function entity.
The method (1400) of any of claims 67 to 71, wherein

the third address is an N9 PSA F-TEID that is received in a PFCP Session Modification Response message from the second user plane entity.
The method (1400) of any of claims 69 to 72, wherein

the third address is an N9 PSA F-TEID that is transmitted in a PFCP Session Modification Request message to the ULCL function entity, and

the eighth address is an S5/S8-U SGW F-TEID that is transmitted in the PFCP Session Modification Request message to the ULCL function entity.
The method (1400) of any of claims 70 to 73, wherein

the fourth address is the N9 ULCL F-TEID that is transmitted in a PFCP Session Modification Request message to the second user plane entity.
The method (1400) of any of claims 70 to 74, further comprising:

transmitting, to the ULCL function entity, an indication of releasing a session between the ULCL function entity and the first user plane entity.
The method (1400) of any of claims 68 to 75, wherein

the mobility management entity comprises an Access and Mobility Management Function ‘AMF’ entity,

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity,

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity, and

the second user plane entity comprises a PSA entity.
The method (1400) of claim 76, further comprising:

performing the process of inserting a ULCL function entity according to any of claims 10-38.
A method (1500) at a Uplink Classifier ‘ULCL’ function entity, comprising:

receiving (S1501) , from a second control plane entity, a trigger of first session modification for the ULCL function entity; and

transmitting (S1503) , to the second control plane entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (1600) of claim 78, wherein the method is performed in a case where handover from a 5G System ‘5GS’ to an Evolved Packet System ‘EPS’ is required.
The method (1500) of claim 78 or 79, further comprising:

receiving a third address and an eighth address from the second control plane entity, wherein the third address is allocated to the second user plane entity, and forwarded from the second user plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the second user plane entity, and the eighth address is allocated to the first user plane entity, and forwarded from the first control plane entity by the second control plane entity for the ULCL function entity to transmit UL traffic to the first user plane entity.
The method (1500) of any of claims 78 to 80, wherein

the second address is an S5-U ULCL F-TEID that is transmitted in a Packet Forwarding Control Protocol ‘PFCP’ Session Modification Response message to the second control plane entity, and

the fourth address is an N9 ULCL F-TEID that is transmitted in the PFCP Session Modification Response message to the second control plane entity.
The method (1500) of any of claims 80 to 81, wherein

the third address is an N9 PSA F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity, and.

the eighth address is an S5/S8-U SGW F-TEID that is received in the PFCP Session Modification Request message from the second control plane entity.
The method (1500) of any of claims 80 to 82, further comprising:

receiving, from the second control plane entity, an indication of releasing a session between the ULCL function entity and the first user plane entity; and

releasing the session between the ULCL function entity and the first user plane entity.
The method (1500) of any of claims 80 to 83, wherein

the first control plane entity comprises a Serving Gateway Control plane ‘SGW-C’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity,

the first user plane entity comprises a Serving Gateway User plane ‘SGW-U’ entity,

the ULCL function entity comprises a ULCL Protocol Data Unit Session Anchor ‘PSA’ entity, and

the second user plane entity comprises a PSA entity.
A method (1600) at a second user plane entity, comprising:

transmitting (S1601) , to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a Uplink Classifier ‘ULCL’ function entity to transmit UL traffic to the second user plane entity; and

receiving (S1603) , from the second control plane entity, a fourth address, that is allocated to the ULCL function entity and forwarded from the ULCL function entity by the second control plane entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The method (1600) of claim 85, wherein

the third address is an N9 PSA Full Qualified-Tunnel Endpoint Identifier ‘F-TEID’ that is transmitted in a Packet Forwarding Control Protocol ‘PFCP’ Session Modification Response message to the second control plane entity, and

the fourth address is an N9 ULCL F-TEID that is received in a PFCP Session Modification Request message from the second control plane entity.
The method (1600) of claim 85 or 86, wherein

the second user plane entity comprises a Protocol Data Unit Session Anchor ‘PSA’ entity,

the second control plane entity comprises a combined Packet Data Network Gateway Control plane ‘PGW-C’ and Session Management Function ‘SMF’ entity, and

the ULCL function entity comprises a ULCL PSA entity.
A first control plane entity (2000) , comprising:

at least one processor (2001) , and

at least one memory (2003) , storing instructions which, when executed on the at least one processor (2001) , cause the first control plane entity (2000) to:

determine that a second control plane entity selected by the first control plane entity supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity; and

transmit, to the second control plane entity, an indication of selecting a first user plane entity and a ULCL function entity.
The first control plane entity (2000) of claim 88, wherein the instructions, when executed on the at least one processor (2001) , further cause the first control plane entity (2000) to perform the method according to any of claims 2 to 9.
A second control plane entity (2200) that supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity, comprising:

at least one processor (2201) , and

at least one memory (2203) , storing instructions which, when executed on the at least one processor (2201) , cause the second control plane entity (2200) to:

perform a process of inserting a ULCL function entity during a connection establishment.
The second control plane entity (2200) of claim 90, wherein the instructions, when executed on the at least one processor (2201) , further cause the second control plane entity (2200) to perform the method according to any of claims 11 to 39.
A Uplink Classifier ‘ULCL’ function entity (2400) , comprising:

at least one processor (2401) , and

at least one memory (2403) , storing instructions which, when executed on the at least one processor (2401) , cause the ULCL function entity (2400) to:

receive, from a second control plane entity that supports selection of a first user plane entity and a ULCL function entity, a session establishment request message; and

transmit, to the second control plane entity, a session establishment response message.
The ULCL function entity (2400) of claim 92, wherein the instructions, when executed on the at least one processor (2401) , further cause the ULCL function entity (2400) to perform the method according to any of claims 41 to 56.
A first user plane entity (2600) , comprising:

at least one processor (2601) , and

at least one memory (2603) , storing instructions which, when executed on the at least one processor (2601) , cause the first user plane entity (2600) to:

receive, from a first control plane entity, a second address, that is allocated to a Uplink Classifier ‘ULCL’ function entity, for the first user plane entity to transmit UL traffic to the ULCL function entity, wherein the second address was received by the first control plane entity from the ULCL function entity via the second control plane entity.
The first user plane entity (2600) of claim 94, wherein the instructions, when executed on the at least one processor (2601) , further cause the second user plane entity (2600) to perform the method according to any of claims 58 to 59.
A second user plane entity (2800) that supports selection of a first user plane entity and a Uplink Classifier ‘ULCL’ function entity, comprising:

at least one processor (2801) , and

at least one memory (2803) , storing instructions which, when executed on the at least one processor (2801) , cause the second user plane entity (2800) to:

transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a Uplink Classifier ‘ULCL’ function entity to transmit UL traffic to the second user plane entity; and

receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The second user plane entity (2800) of claim 96, wherein the instructions, when executed on the at least one processor (2801) , further cause the second user plane entity (2800) to perform the method according to any of claims 61 to 63.
A second control plane entity (3000) , comprising:

at least one processor (3001) , and

at least one memory (3003) , storing instructions which, when executed on the at least one processor (3001) , cause the second control plane entity (3000) to:

trigger first session modification to a ULCL function entity; and

receive, from the ULCL function entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.
The second control plane entity (3000) of claim 98, wherein the instructions, when executed on the at least one processor (3001) , further cause the second control plane entity (3000) to perform the method according to any of claims 66 to 77.
A Uplink Classifier ‘ULCL’ function entity (3200) , comprising:

at least one processor (3201) , and

at least one memory (3203) , storing instructions which, when executed on the at least one processor (3201) , cause the ULCL function entity to:

receive, from a second control plane entity, a trigger of first session modification for the ULCL function entity; and

transmit, to the second control plane entity, a second address and a fourth address allocated to the ULCL function entity, wherein the second address is used for the first user plane entity to transmit UL traffic to the ULCL function entity, and the fourth address is used for the second user plane entity to transmit DL traffic to the ULCL function entity.
The ULCL function entity (3200) of claim 100, wherein the instructions, when executed on the at least one processor (3201) , further cause the ULCL function entity (3200) to perform the method according to any of claims 79 to 84.
A second user plane entity (3400) , comprising:

at least one processor (3401) , and

at least one memory (3403) , storing instructions which, when executed on the at least one processor (3401) , cause the second user plane entity (3400) to:

transmit, to a second control plane entity, a third address allocated to the second user plane entity, which is to be used for a Uplink Classifier ‘ULCL’ function entity to transmit UL traffic to the second user plane entity; and

receive, from the second control plane entity, a fourth address, that is allocated to the ULCL function entity and forwarded from the ULCL function entity by the second control plane entity, for the second user plane entity to transmit DL traffic to the ULCL function entity.
The second user plane entity (3400) of claim 102, wherein the instructions, when executed on the at least one processor (3401) , further cause the second user plane entity (3400) to perform the method according to any of claims 86 to 87.
A computer readable storage medium having computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of claims 1 to 9.
A computer readable storage medium having computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of claims 10 to 39 and 65 to 77.
A computer readable storage medium having computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of claims 40 to 56 and 78 to 84.
A computer readable storage medium having computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of claims 57 to 59 and 85 to 87.
A computer readable storage medium having computer program instructions stored thereon, the computer program instructions, when executed by at least one processor, causing the at least one processor to perform the method according to any of claims 85 to 87.