Method for solving timeout problem of PDU (Protocol Data Unit) session shunting

Abstract

The present disclosure relates generally to wireless communication networks, and in particular, to an example process of establishing robust protocol data unit (PDU) session offload for dual connectivity in order to avoid the occurrence of unnecessary timeout in a core network during establishment of an offload PDU session or during modification of an existing non-offload PDU session to an offload PDU session. For example, at a master node (MN), before a secondary node (SN) addition procedure or an MN-initiated SN modification procedure for offloading a PDU session is completed, and before a downlink communication address of a target SN becomes available, the MN may provide an alternative downlink communication address to a core network such that the core network does not need to wait for the SN addition procedure or the MN-initiated modification procedure to be completed. The alternative address may then be updated to the actual downlink communication address after obtaining the alternative address from the SN during an SN addition process or during an SN modification process initiated by the MN.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless communication networks, and more specifically to example procedures for establishing a robust split Protocol Data Unit (PDU) session for dual connectivity. BACKGROUND

[0002] In a wireless access network, a PDU session can be established between a terminal device and a network. A PDU session of a wireless terminal can be split between two wireless access network nodes. Existing procedures for establishing a split PDU session or converting a non-split PDU session to a split PDU session require several steps involving multiple network nodes and can take a long time to complete. SUMMARY

[0003] The present disclosure relates generally to wireless communication networks, and more specifically to example procedures for establishing a robust split PDU session for dual connectivity.

[0004] In one example implementation, a method performed by a Master wireless access network Node (MN) is disclosed. The method comprises: receiving, from a core network, a request message associated with a PDU session for splitting the PDU session, the request message comprising an uplink communication address associated with the PDU session; in response to the request message, and before a SN addition procedure or a MN initiated SN modification procedure for a target Secondary wireless access Node (SN) for splitting the PDU session is completed: generating a fallback downlink communication address of the target SN for the PDU session, the fallback downlink communication address corresponding to the uplink communication address; and transmitting, to the core network, a response message comprising the fallback downlink communication address of the target SN.

[0005] In the above example implementation, the method can further comprise: allocating a set of quality of service (QoS) flows to the fallback downlink communication address, and indicating the set of QoS flows to the core network in the response message.

[0006] In any of the example implementations above, the uplink communication address comprises at least one of: an uplink transport network layer (TNL) address, an uplink tunnel endpoint identifier (TEID) address, and user plane (UP) transport layer information.

[0007] In any of the example implementations above, the fallback downlink communication address comprises at least one of: a downlink TNL address, a downlink TEID address, and UP transport layer information.

[0008] In any of the example implementations above, the method can further comprise: performing the SN addition procedure or the MN-initiated SN modification procedure to offload the PDU session using the target SN.

[0009] In any of the example implementations above, the SN addition procedure or MN-initiated SN modification procedure can comprise: transmitting, by the MN, a SN addition request message or a SN modification request message to the target SN; and obtaining, from the target SN, a second downlink communication address associated with the target SN.

[0010] In any of the example implementations above, the method can further comprise: in response to the SN addition procedure or the MN-initiated SN modification procedure being completed, transmitting the second downlink communication address to the core network to replace the fallback downlink communication address.

[0011] In any of the example implementations above, the method can further comprise: determining a set of QoS flows for the fallback downlink communication address, and informing the core network of the set of QoS flows through the response message; and informing the target SN of the same set of QoS flows through the SN addition request message or the SN modification request message.

[0012] In any of the example implementations above, the request message is a PDU session resource setup request message for establishing the PDU session; and the request message comprises a second uplink communication address assigned to the PDU session.

[0013] In any of the example implementations above, the method can further comprise: generating a second downlink communication address that points to the MN and corresponds to the second uplink communication address, wherein the fallback downlink communication address is generated as a copy of the second downlink communication address.

[0014] In any of the example implementations described above, the method can further include performing the SN addition procedure or the MN-initiated SN modification procedure to the target SN. The SN addition procedure or the MN-initiated SN modification procedure can include transmitting, by the MN, an SN addition request message or an SN modification request message to the target SN; obtaining, from the SN, a third downlink communication address associated with the target SN; and in response to completion of the SN addition procedure or the MN-initiated SN modification procedure, transmitting the third downlink communication address to the core network to replace the surrogate downlink communication address.

[0015] In any of the example implementations described above, the request message is a PDU session resource modification request message; and the surrogate downlink communication address is generated as a copy of an existing downlink communication address of the PDU session associated with the MN.

[0016] In any of the example implementations described above, the method can include performing the SN addition procedure or the MN-initiated SN modification procedure to the target SN. The SN addition procedure or the MN-initiated SN modification procedure can include transmitting, by the MN, an SN addition request message or an SN modification request message to the target SN; obtaining, from the SN, a second downlink communication address associated with the target SN; and in response to completion of the SN addition procedure or the MN-initiated SN modification procedure, transmitting the second downlink communication address to the core network to replace the surrogate downlink communication address.

[0017] In another example implementation, a method performed by a core network node of a wireless communication network is disclosed. The method can include transmitting, to a MN, a request message associated with a PDU session for offloading the PDU session, the request message including an uplink communication address associated with the PDU session; and receiving a response message from the MN, the response message including a surrogate downlink communication address for the PDU session of a target SN, wherein the response message is transmitted by the MN in response to the request message and prior to completion of an SN addition procedure or a MN-initiated SN modification procedure to a target SN for offloading the PDU session.

[0018] In the example implementation described above, the uplink communication address includes at least one of: an uplink TNL address, an uplink TEID address, and UP transport layer information.

[0019] In any of the example implementations described above, the surrogate downlink communication address includes at least one of: a downlink TNL address, a downlink TEID address, and UP transport layer information.

[0020] In any of the example implementations described above, the method can further include receiving a second downlink communication address from the MN after the MN completes the SN addition procedure or the MN-initiated SN modification procedure; and replacing the surrogate downlink communication address with the second downlink communication address.

[0021] In any of the example implementations described above, the method can further include receiving, by the response message, an indication from the MN of a set of QoS flows for the surrogate downlink communication address.

[0022] In any of the example implementations described above, the request message is a PDU session resource setup request message for establishing the PDU session; and the request message includes a second uplink communication address assigned to the PDU session.

[0023] In any of the example implementations described above, the method can further include receiving a second downlink communication address from the MN that is directed to the MN and corresponds to the second uplink communication address, wherein the surrogate downlink communication address is generated by the MN as a duplicate of the second downlink communication address.

[0024] In any of the example implementations described above, the method can further include receiving a third downlink communication address transmitted by the MN after the MN completes the SN addition procedure or the MN-initiated SN modification procedure; and replacing the surrogate downlink communication address with the third downlink communication address.

[0025] In any of the example implementations described above, the request message is a PDU session resource modification request message; and the surrogate downlink communication address is generated as a duplicate of an existing downlink communication address of the PDU session associated with the MN.

[0026] In any of the example implementations described above, the method can further include receiving a second downlink communication address from the MN, the second downlink communication address being generated after the SN addition procedure or the MN-initiated SN modification procedure is completed; and replacing the surrogate downlink communication address with the second downlink communication address.

[0027] Also disclosed is a wireless access network node or a core network node that performs any of the methods described above. A wireless terminal device can include a processor and a memory, wherein the processor is configured to read computer code from the memory to cause the wireless access network node or the core network node to perform any of the methods described above.

[0028] Also disclosed is a non-transitory computer readable program medium having computer code stored thereon. The computer code, when executed by a processor of a wireless access network node or a core network node in any of the above methods, is configured to cause the processor to implement any of the above methods.

[0029] The above embodiments and other aspects and alternatives thereof are more fully described below in the detailed description, drawings, and in the claims. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 An example wireless communication network is shown that includes a wireless access network, a core network, and a data network.

[0031] Figure 2 An example wireless access network is shown that includes a plurality of mobile stations / terminals or user equipment (UEs) and wireless access network nodes that communicate with each other over an air wireless communication interface.

[0032] Figure 3 An example radio access network (RAN) architecture is shown.

[0033] Figure 4 An example communication protocol stack in a wireless access network node or wireless terminal device is shown that includes various network layers.

[0034] Figure 5 An example core network is shown.

[0035] Figure 6 An example procedure for PDU session offloading during PDU session resource setup is shown.

[0036] Figure 7 An example procedure for PDU session offloading during PDU session resource modification is shown.

[0037] Figure 8 An example implementation of two-stage PDU session offloading is shown.

[0038] Figure 9 An example procedure for two-stage PDU session offloading during PDU session resource setup is shown.

[0039] Figure 10 An example failure handling procedure for two-stage PDU session offloading during PDU session resource setup is shown.

[0040] Figure 11 Another example failure handling procedure for two-stage PDU session offloading during PDU session resource setup is shown.

[0041] Figure 12 An example procedure for two-stage PDU session offloading during PDU session resource modification is shown.

[0042] Figure 13 An example failure handling procedure for two-stage PDU session offloading during PDU session resource modification is shown.

[0043] Figure 14 Another example failure handling procedure for two-stage PDU session offloading during PDU session resource modification is shown. DETAILED DESCRIPTION

[0044] The techniques described in this disclosure can be used to more robustly establish offloaded PDU sessions. The term "air interface" can be used interchangeably with "air interface" or "wireless interface" in this disclosure. The term "exemplary" is used as "an example of" and does not imply a preference or a requirement for a particular example, implementation, or embodiment unless otherwise indicated. Section headings are used in this disclosure as a matter of convenience to help with understanding of the disclosed implementations, and are not intended to limit the scope of the technology disclosed in each section to only the technology of that section. The disclosed implementations can be further implemented in various different forms and thus the scope of the disclosure or claimed subject matter is not intended to be limited to only the examples described below. Various implementations can be implemented as methods, devices, components, systems, or non-transitory computer-readable media. As such, embodiments of the present disclosure can take the form of an apparatus, a method, or an article of manufacture.

[0045] In summary, the present disclosure and the various example embodiments described below generally relate to wireless communication networks and, in particular, to communication between a UE and a base station with assistance from other UEs. For example, a special wireless carrier can be configured for communication between UEs. One UE can be configured to communicate with a proximate other UE over the special wireless carrier in a manner similar to communication with the base station. As such, one or more UEs can be configured to assist other UEs in transmitting to and / or receiving from the base station downlink or uplink transmissions over the special wireless carrier. Each of these UEs can be configured as an assisting UE or an assisted UE with respect to the uplink or downlink direction. The special wireless carrier can be independent of, but configured in a related manner to, the wireless carrier used for direct communication between the UEs and the base station.

[0046] Wireless communication network As Figure 1As shown in FIG. 100, an example wireless communication network can include wireless terminal devices or user equipment (UEs) 110, 111, and 112, a carrier network 102, various service applications 140, and other data networks 150. Wireless terminal devices or UEs can alternatively be referred to as wireless terminals. For example, the carrier network 102 can include access network nodes 120 and 121, and a core network 130. The carrier network 110 can be configured to transport voice, data, and other information (collectively referred to as data traffic) among the UEs 110, 111, and 112, between the UEs and the service applications 140, or between the UEs and the other data networks 150. The access network nodes 120 and 121 can be configured as various wireless access network nodes (WANNs, alternatively referred to as wireless base stations) to interact with UEs at one end of a communication session and to interact with the core network 130 at the other end. The term "access network" can be used more broadly to refer to the combination of the wireless terminal devices 110, 111, and 112 and the access network nodes 120 and 121. The wireless access network can alternatively be referred to as a Radio Access Network (RAN). The core network 130 can include various network nodes configured to control communication sessions and to perform network access management and traffic routing. The service applications 140 can be hosted by various application servers that are deployed external to the core network 130 but connected to the core network 130. Likewise, the other data networks 150 can also be connected to the core network 130.

[0047] In Figure 1 In the example wireless communication network 100, UEs can communicate with each other through the wireless access network. For example, UEs 110 and 112 can be connected to and communicate through the same access network node 120. UEs can also communicate with each other through both the access network and the core network. For example, UE 110 can be connected to access network node 120, while UE 111 can be connected to access network node 121, and as such, UEs 110 and 111 can communicate with each other through access network nodes 120 and 121 and the core network 130. UEs can also communicate with service applications 140 and data networks 150 through the core network 130. In addition, UEs can communicate directly with each other through sidelink communications (shown as 113).

[0048] Figure 2An example system diagram of the wireless access network 120, which includes the WANN 202 serving the UE 110 and the UE 112 over an air interface 204, is also shown. The wireless transmission resources of the air interface 204 include a combination of frequency resources, time resources, and / or spatial resources. Each of the UE 110 and the UE 112 can be a mobile or fixed terminal device installed with a mobile access unit such as a SIM / USIM (Subscriber Identity Module / Universal Subscriber Identity Module) module to access the wireless communication network 100. The UE 110 and the UE 112 can both be implemented as terminal devices including, but not limited to, a mobile phone, a smart phone, a tablet computer, a notebook computer, a vehicle-mounted communication device, a roadside communication device, a sensor device, a smart home appliance such as a television, a refrigerator, and an oven, or other devices capable of wireless communication over a network. As Figure 2 As shown, each of these UEs, such as the UE 112, can include a transceiver circuit 206 coupled to one or more antennas 208 for enabling wireless communication with the WANN 120 or another UE, such as the UE 110. The transceiver circuit 206 can also be coupled to a processor 210, which can also be coupled to a memory 212 or other storage device. The memory 212 can be transitory or non-transitory, and can have stored therein computer instructions or code that, when read and run by the processor 210, cause the processor 210 to implement the methods described herein.

[0049] Similarly, WANN 120 can comprise a wireless base station or other wireless network access point capable of wireless communication with one or more UEs over air interface 204, and communication with core network 130. For example, WANN 120 can be implemented without limitation as a 2G base station, a 3G nodeB, an LTE eNB, a 4G LTE base station, a 5G NR base station of a 5G gNB, a 5G centralized unit base station, or a 5G distributed unit base station. Each type of these WANNs can be configured to perform a corresponding set of wireless network functions. WANN 202 can comprise transceiver circuitry 214 coupled with one or more antennas 216, which can comprise various forms of antenna towers 218 to enable wireless communication with UEs 110 and 112. Transceiver circuitry 214 can be coupled to one or more processors 220, which can be further coupled to memory 222 or other storage devices. Memory 222 can be transitory or non-transitory, and can have stored therein instructions or code that, when read and run by one or more processors 220, cause one or more processors 220 to implement various functions of WANN 120 described herein.

[0050] As Figure 2 shown in the example of FIG. 1, data packets in a wireless access network can be transmitted as protocol data units (PDUs). Data included therein can be encapsulated as PDUs at various network layers, with nested and / or layered protocol headers. PDUs can be communicated between a transmitting device or transmitting end (which can be used interchangeably) and a receiving device or receiving end (which can be used interchangeably) when a connection (e.g., a radio link control (RRC) connection) is established between the transmitting and receiving ends. Either of the transmitting or receiving devices can be a wireless terminal device (such as devices 110 and 120 of FIG. 1) or a wireless access network node (such as node 202 of FIG. 2). Each device can be both a transmitting device and a receiving device for bidirectional communication. Figure 2 As Figure 2 shown in the example of FIG. 1, data packets in a wireless access network can be transmitted as protocol data units (PDUs). Data included therein can be encapsulated as PDUs at various network layers, with nested and / or layered protocol headers. PDUs can be communicated between a transmitting device or transmitting end (which can be used interchangeably) and a receiving device or receiving end (which can be used interchangeably) when a connection (e.g., a radio link control (RRC) connection) is established between the transmitting and receiving ends. Either of the transmitting or receiving devices can be a wireless terminal device (such as devices 110 and 120 of FIG. 1) or a wireless access network node (such as node 202 of FIG. 2). Each device can be both a transmitting device and a receiving device for bidirectional communication.

[0051] Figure 1 Core network 130 of FIG. 1 can comprise various network nodes that are geographically distributed and interconnected to provide network coverage for a service area of carrier network 102. These network nodes can be implemented as dedicated hardware network nodes. Alternatively, these network nodes can be virtualized and implemented as virtual machines or software entities. These network nodes can each be configured with one or more types of network functions that collectively provide resource provisioning and routing functions for core network 130.

[0052] Returning to the wireless wireless access network (RAN),Figure 3 An example RAN 340 is shown in communication with a core network 310 and wireless terminals UE1 through UE7. The RAN 340 can include one or more types of wireless base stations or WANNs 320 and 321, which can include, but are not limited to, gNBs, eNodeBs, NodeBs, or other types of base stations (for simplicity, only gNBs are shown, Figure 3 The RAN 340 can be backhauled to the core network 310 through, for example, an NG interface.

[0053] Figure 3 Each WANN can be configured to communicate with each other through an inter-node interface. For example, each gNB can communicate with each other through an Xn interface. As another example, a 5G base station gNB can communicate with an LTE base station, such as a NodeB or eNodeB, through an X2 interface. In some example implementations, the WANN 320 can further include multiple independent access network nodes, for example, in the form of a Central Unit (CU) 322 and one or more Distributed Units (DUs) 324 and 326. In some embodiments, the CU can be a gNB Central Unit (gNB-CU) and the DUs can be gNB Distributed Units (gNB-DUs). The CU 322 can be connected with the DU1 324 and the DU2 326 through various inter-node interfaces, for example, an Fl interface. Each of the various inter-node interfaces can be further divided into a control plane interface and a user plane interface. As a specific example, the Fl interface between the CU and the DUs can further include an Fl-C interface and an Fl-U interface, which can be used to carry control plane information and user plane data, respectively. Likewise, the Xn interface, or the X2 interface, can include an Xn-C interface and an Xn-U interface, or an X2-C interface and an X2-U interface. For the purposes of the present disclosure and its claims, each CU and DU is considered an independent access network node. Thus, the Fl interface is within the definition of an inter-node communication interface. Moreover, although various implementations described below are provided in the context of a 5G cellular wireless network, the underlying principles described herein are applicable to other types of wireless access networks, including but not limited to other generations of cellular networks, as well as Wi-Fi, Bluetooth, ZigBee, and WiMax networks.

[0054] Each UE can be connected to the network via the air interface through the WANN 320. Each UE can be served by at least one cell. Each cell is associated with a coverage area. These cells are alternatively referred to as serving cells. The coverage areas between cells may partially overlap. Each UE may actively communicate with at least one cell when it is potentially connectable to or able to connect to more than one cell. Figure 1 In the example, UE1, UE2, and UE3 can be served by cell 1 330 of DU1, while UE4 and UE5 can be served by cell 2 332 of DU1, and UE6 and UE7 can be served by cell 3 associated with DU2. In some implementations, a UE can be served by two or more cells simultaneously. Each UE can be mobile, and the signal strength and quality from the various cells at the UE can depend on the UE's location and mobility.

[0055] In some example implementations, Figure 3 The cells shown can be alternatively referred to as serving cells. Serving cells can be grouped into serving cell groups (CGs). A serving cell group can be a master CG (MCG) or a secondary CG (SCG). Each type of cell group may contain one master cell and one or more secondary cells. For example, a master cell in an MSG may be referred to as a PCell, while a master cell in an SCG may be referred to as a PScell. Secondary cells in either an MCG or an SCG may be referred to as SCells. Master cells including both PCells and PScells may be collectively referred to as spCells (special cells). All of these cells may be referred to as serving cells or cells. Unless otherwise specified, the terms "cell" and "serving cell" are generally used interchangeably. The term "serving cell" may refer to a cell that is currently serving, will be serving, or may be serving a UE. In other words, a "serving cell" may not currently be serving a UE. Although the various embodiments described below may sometimes refer to one of the types of serving cells described above, the basic principles apply to all types of serving cells in both types of serving cell groups.

[0056] Figure 4 Further demonstrated in Figures 1 to 3 A simplified diagram of the various network layers involved in transmitting a user plane PDU from transmitting device 402 to receiving device 404 in an example wireless access network. Figure 4 It is not intended to include all the necessary equipment components or network layers for handling the transmission of PDUs. Figure 4Data encapsulated by upper network layers 420 of transmitting device 402 is shown to be passed through packet data convergence protocol (PDCP) layer of transmitting device (not shown in Figure 4

[0057] In Figure 4 upper layers 420 can be referred to as layer-3 or L3, while the various intermediate layers (such as RLC layer and / or MAC layer and / or PDCP layer (not shown in Figure 4

[0058] Figure 5 An example breakdown of network node functions in core network 130 is shown. While Figure 5 each of these network nodes can be instantiated as multiple instances distributed throughout core network 130, as Figure 5 ​​As shown, the core network 130 can include, but is not limited to, access management network function (AMF) node 530, session management function (SMF) node 540, user plane function (UPF) node 550, policy control function (PCF) node 520, and application data management function (AF) node 510.

[0059] The AMF node 530 can communicate with the access network 120, the SMF node 540, and the PCF node 520 through the communication interfaces 522, 532, and 524, respectively, and can be responsible for resource allocation registration, authentication, and access of UEs to the core network 130, as well as allocating respective SMF nodes 540 to support specific UE communication sessions. The respective SMF nodes 540 allocated by the AMF node 530 can in turn be responsible for allocating respective UPF nodes 550 to support specific UE communication sessions and controlling these allocated UPF nodes 550 through the communication interfaces 546. Alternatively or additionally, in some implementations, the respective UPF nodes 550 can be allocated directly by the AMF node 530 through the interface 534 and controlled by the SMF node 540 through the communication interfaces 546. Access policies and session routing policies applicable to UEs can be managed by the PCF node 520, which communicates the policies to the AMF node 530 and the SMF node 540 through the communication interfaces 524 and 523, respectively. The PCF node 520 can also be responsible for managing user subscriptions 512 to service applications 140 through the AF node 510. The signaling and data exchange between various types of network nodes through various communication interfaces indicated by various connection lines in the middle can be carried through signaling / data messages that follow a predetermined type of format or protocol. Figure 5

[0060] To support a specific end-to-end communication task requested by a UE, a communication session can be established to support a data traffic pipe for transmitting specific end-to-end data communication traffic. The carrier network portion of the data traffic pipe, such as the access network 120 and the core network 130, can be established by the network 100 in response to the UE’s request for the specific end-to-end communication task. Figure 5 ​(As shown in 570) This may involve one or more network nodes in access network 120 and a set of UPF nodes 552, 554, and 556 in core network 130. These nodes are selected and controlled by, for example, a set of SMF nodes 542 and 544, which may be selected and controlled by AMF node 530 responsible for establishing and managing communication sessions. Data traffic is routed between the following through communication interfaces such as 524, 558, and 559: a UE at one end of the data traffic pipeline, the carrier network portion of the data traffic pipeline (including a set of network nodes in access network 120 and the selected UPF nodes 552, 554, and 556 in core network 130), and the other end of the data traffic pipeline (including, for example, another UE, a serving application or application server 140, and data network 150).

[0061] PDU session offloading at the UPF In some example implementations, the aforementioned RAN can support dual connectivity, where a radio terminal can be simultaneously connected to a primary base station (referred to as the primary node MN) and a secondary base station (referred to as the secondary node SN) to improve the downlink-to-uplink transmission throughput of the UE. As a specific example, the NG-RAN can be configured to support NR-NR Dual Connectivity (NR-DC), in which the UE is connected to two gNBs: one gNB acting as the MN associated with the MCG, and the other gNB acting as the SN associated with the SCG. Alternatively, DR-DC can be used when the UE is connected to a single gNB, which can act as both the MN and SN and be configured as both the MCG and SCG. The MN and SN can communicate via an inter-node interface (such as the Xn interface).

[0062] Figure 6 An example procedure 600 for establishing a split PDU session between the UE and the network side is shown. Figure 7 An example procedure 700 is shown to offload a non-offloaded PDU session established between the UE and the network side into an offloaded PDU session. For example... Figure 6 As shown, the process of establishing a new offloaded PDU session 600 typically provides two uplink (UL) tunnel endpoint ID (TEID) addresses during PDU session resource establishment to allow PDU session offloading when a new PDU session needs to be established. Figure 7As shown, in the procedure 700 of modifying a non-split PDU session to a split PDU session, the core network can provide additional UL TEID addresses during PDU session resource modification in order to allow, for example, the MN to split the PDU session. In both cases, the MN can perform a SN addition procedure or a MN initiated SN modification procedure first and if the MN decides to split the PDU session, the MN provides the downlink (DL) TEID addresses to be applied as additional DL tunnel addresses to the core network through the PDU session resource setup response message or the PDU session resource modification response message.

[0063] In more detail, as shown in Figure 6 When a new PDU session needs to be established, the core network can provide two UL TEID addresses during PDU session resource setup in order to allow PDU session splitting. The MN can perform, for example, a SN addition or a MN initiated SN modification procedure. If the MN decides to split the PDU session, the MN can provide two DL TEID addresses and the QoS flows associated with each tunnel.

[0064] In particular, in step 610 of Figure 6 the core network (e.g., the AMF node 609 of the example 5G network) provides two UL TEID addresses during PDU session resource setup to be applied as a first UL tunnel (e.g., NG-U interface) and an additional NG-U tunnel (in case the MN 604 decides to split the PDU session).

[0065] In step 620 of Figure 6 the MN 604 can decide to establish two tunnels. The MN 604 can use a SN addition procedure or a MN initiated SN modification procedure to establish and configure dual connectivity for the UE 602.

[0066] In step 630 of Figure 6 the MN 604 provides two DL TEID addresses to be applied as a first tunnel address and an additional DL tunnel address with respect to, for example, a NG-U interface. The MN also provides which QoS flows are associated or mapped to which one of the first tunnel and the additional tunnel.

[0067] As shown in Figure 7Further shown, the previous non-split PDU session can be modified to be split into a split PDU session. The network side (e.g., 5G network) can provide additional UL TEID addresses during the PDU session resource modification procedure in order to allow the MN 704 to split the PDU session. The MN 704 can perform a SN addition or MN initiated SN modification procedure. If the MN 704 decides to split the PDU session, the MN 704 provides the DL TEID addresses (which are to be applied as additional DL tunnel addresses) and the QoS flows associated with the tunnel.

[0068] In particular, in step 710, the core network (e.g., 5G core network, 5GC) can provide additional UL TEID addresses during the PDU session resource modification, which are to be applied as additional tunnels (e.g., NG-U tunnels) in case the MN 604 decides to split the PDU session.

[0069] In step 720, the MN 704 can decide to establish two tunnels. If a new tunnel is to be established at the SN 706, the MN 704 can use a SN addition procedure or a MN initiated SN modification procedure if the QoS flow moves to the SN 706 and data forwarding is applicable.

[0070] In step 730, the MN 704 can provide the DL TEID addresses, which are to be applied as additional DL tunnel addresses on the NG-U interface, for example, and the MN 704 can further provide the QoS flows associated with the tunnel.

[0071] In the above example method, as Figure 6 and Figure 7 Further shown, after the core network sends out the PDU session resource setup request or PDU session resource modification request, a corresponding response is expected to be received (e.g., steps 630 and 730). To avoid indefinite waiting, a pre-defined default timer value (e.g., 6 seconds) can be set. If no response is received after sending the PDU session resource setup or modification request according to the pre-defined timer value, the core network (e.g., AMF 609 and 709) can consider the procedure to be failed due to timeout.

[0072] However, this mechanism can cause unnecessary timeout of the PDU session setup or modification procedure, because: (1) the default timer value should not be set too long for efficiency reasons, and (2) even if the required steps 620 and 720 are performed normally, the MN can need more time than the default timer value set reasonably at the AMF in order to get all the information included in the response in step 630 or 730. For example, after receiving the PDU session resource setup or modification request, the MN needs to trigger measurements (e.g.,Figure 6 and Figure 7 Uu interface measurements with the UE (where the longest timer can be set to e.g. 8 seconds) not shown in Figure 6 and Figure 7 Uu interface (where the longest timer can be set to e.g. 8 seconds). This whole set of procedures can need to be performed by the MN 604 or 704 before it transmits a response to the core network in step 630 or 730, and can take a long time because it involves interactions between the base stations over e.g. the Xn interface, and interactions with the UE over the air interface (e.g. the Uu interface). Thus, the core network (e.g. the 5GC) can not receive the response message from the MN 604 or 704 within the time set by the pre-defined timer value in at least some occasions, and will consider the PDU session split procedure to have failed, when the MN 604 or 704 is simply in the normal operational step of generating the response, thus impairing system performance.

[0073] In the example implementations below, various methods are employed to reduce the probability of unnecessary timeouts of the MN due to PDU session split in PDU session resource setup or modification procedures.

[0074] PDU session offloading through a fallback downlink tunnel during PDU session resource setup In some example implementations to avoid the unnecessary timeout problem described above during the PDU session resource setup procedure of Figure 6 , the core network and the base station (MN) can be configured to consider the PDU session to be split even if the MN is still in the process of setting up downlink tunnels with the SN and the UE to split the PDU session.

[0075] Figure 8 An overall example implementation is shown in

[0076] As shown in 804, after the SN addition procedure or MN initiated SN modification procedure is completed, the MN obtains additional DL TNL addresses from the SN and sends them to the core network (e.g., 5GC) to update the previous additional DL TNL address (or the alternative downlink communication address). After the update, the UL TNL address is associated with the DL TNL address and the additional UL TNL address becomes associated with the additional DL TNL address.

[0077] Figure 9 A particular example implementation 900 of the overall implementation following Figure 8 is shown, where the core network does not experience unnecessary timeouts while waiting for a response from the MN. The implementation 900 is shown in the context of a 5G network, involving a UE 902, a MN 904, a SN 906, a UPF 908, and an AMF 909, as an example. The example implementation 900 includes the following steps.

[0078] In step 910, the core network (e.g., AMF 909 in 5GC) provides two UL addresses during PDU session resource setup via a PDU session resource setup request message or other interface message (e.g., NG interface message). The two UL addresses are to be applied as a first UL tunnel on the user plane (UP) interface (such as NG-U interface), and an additional NG-U tunnel in case the MN 904 decides to split traffic for the PDU session.

[0079] The UL addresses may, for example, include but are not limited to UL TNL addresses, UL TEID addresses, or UP transport layer information. As an example, the UL addresses can include UP transport layer information as an information element (IE) in the PDU session resource setup request message. In NR, for example, this IE can be used to provide NG user plane transport layer information associated with a PDU session for a pair of NG-RAN nodes and the UPF 908. For example, it can correspond to an IP address and a GPRS Tunneling Protocol Tunnel Endpoint Identifier (GTP-TEID), as shown in Table I below.

[0080] Table I

[0081] In step 920, the MN 904 decides to establish two tunnels.

[0082] In step 930, the MN 904 can provide two DL (downlink) addresses in the PDU session resource setup response message, which are to be applied as the first DL tunnel address and the additional DL tunnel address. The MN 904 can also provide the QoS (quality of service) flow associated with each tunnel in the PDU session resource setup response message.

[0083] Each of these DL addresses can include, but is not limited to, a DL TNL address, a DL TEID address, or UP transport layer information. An example information element representing UP transport layer information in an example PDU session resource setup response message is shown in Table I above.

[0084] In this example implementation, the two DL addresses included in the PDU session resource setup response message are the same, since the SN 906 has not yet been added for dual connectivity at this stage, and the MN 904 has not yet received an additional DL address from the SN 906. In contrast to the implementation of steps 630 or 730 in Figure 6 and Figure 7 In the process of steps 630 or 730 in the implementation of Figure 6 and Figure 7 In the process of steps 630 or 730 in the implementation of

[0085] Once the AMF 909 receives the two identical addresses in the PDU session resource setup response message from the MN 904, it can understand that the MN has decided to do PDU session splitting and instructs the core network to handle the PDU session as split. For example, the UPF 908 can start receiving data packets associated with the PDU session through two tunnels and sending downlink data packets through two downlink tunnels. However, these two tunnels have the same DL endpoint, which is identified by the DL tunnel address specified in the PDU session resource setup response message of step 930.

[0086] In step 940, the MN 904 subsequently uses the SN addition procedure initiated by the SN addition request message to add a candidate SN to the PDU session for PDU splitting, or uses the MN initiated SN modification procedure by the SN modification request message to modify a SN (such as the SN 906) to the PDU session for PDU splitting.

[0087] In some implementations, the MN 904 can provide the QoS flows associated with the additional DL address to the SN 906 through the SN addition request message or the SN modification request message, and obtain the additional DL address from the SN 906 through the SN addition procedure or the MN-initiated SN modification procedure.

[0088] The QoS flows provided by the MN 904 to the SN 906 through the SN addition request message or the SN modification request message can be the same or different from the QoS flows associated with the additional DL address in step 930. For example, in step 930, the MN decides how to allocate the QoS flows to the two tunnels, and the corresponding QoS flow to DRB mapping can be determined based on the decision and notified to the UE 902. If the MN provides the same associated QoS flows to the SN in step 940 for the SN addition or the MN-initiated SN modification, the QoS flow to DRB mapping on the SN side can be the same as the mapping determined by the MN’s decision in step 930. Therefore, the MN 904 and the UE 902 do not need to employ a new QoS flow to DRB mapping and update the corresponding configuration. Therefore, it can be beneficial for the associated QoS flows to be the same in step 930 and step 940 in terms of the configuration efficiency of the QoS flow to DRB mapping and / or data forwarding.

[0089] In step 950, the MN 904 can provide the updated additional DL address (to be applied as the additional DL tunnel address) on the NG-U interface, for example, through the PDU session resource modification indication message or other NG interface messages. The MN 904 can also provide which QoS flows are associated with the tunnel.

[0090] In step 960, the core network (e.g., the AMF 909 of the 5GC) confirms to the MN 904 through the PDU session resource modification confirm message or other NG interface messages.

[0091] Figure 10 An example procedure is shown in accordance with Figure 9 but Figure 9 the SN addition procedure or the MN-initiated SN modification procedure at step 940 fails. Steps 1010 to 1030 are consistent with Figure 9 In step 1040, the MN 1004 can trigger the SN addition procedure with the UE 1002 and the SN 1006, and provide the associated QoS flows to the SN 1006 through the SN addition request message, for example. However, this SN addition procedure can fail. As a result of the failure, the SN 1006 can not be added, and therefore the MN 1004 will not be able to obtain the additional DL address associated with Figure 9corresponding to the additional DL tunnel address of step 940. Likewise, the MN 1004 can initiate a SN modification procedure by sending a SN modification request message with associated QoS flows to the SN 1006. However, this MN initiated modification can fail. Thus, the SN 1006 can not be modified to support the PDU session split, and thus the MN 1004 will not obtain the additional DL tunnel address corresponding to step 940. Figure 9 corresponding to the additional DL tunnel address of step 940.

[0092] In step 1050, the MN 1004 can send a PDU session resource modification indication message to the core network (e.g., AMF 1009 in 5GC) to indicate that the PDU session was not successfully split. The additional DL address and QoS flows associated with this tunnel can not be included in this message accordingly.

[0093] In step 1060, the AMF 1009 of the 5GC acknowledges to the MN 1004 by a PDU session resource modification confirmation message to indicate that it has learned of the PDU split failure.

[0094] In Figure 10 In implementations of the PDU session resource modification procedure of

[0095] Figure 11 An example procedure is shown in FIG. 11 when Figure 10 the SN addition or MN initiated SN modification fails. Figure 11 Steps 1110-1140 in FIG. 11 are consistent with steps 1010-1040 in FIG. 10. In step 1150, the MN 1104 sends a PDU session resource notification message to the AMF 1109 of the 5GC to release the PDU session and / or indicate that the PDU session split was not successful in case some anomalies can occur at the UE side (thus the PDU session cannot continue) due to the PDU session split failure. Figure 10

[0096] PDU session offloading through a fallback downlink tunnel during PDU session resource modification In some example implementations to avoid the above unnecessary timeout issue during the PDU session resource modification procedure of Figure 7 the core network and base station (MN) can be configured to consider the SN addition to have been implemented immediately after the request, even if the MN is still in the process of establishing the additional downlink tunnel endpoint of the split PDU session in cooperation with the SN and the UE.

[0097] Various example implementations of these PDU session modifications are described in Figures 12 to 14as described above in relation to Figures 9 to 11 the above implementation of PDU session resource setup.

[0098] Firstly, the messages in steps 1210, 1310 and 1410 are different from those in steps 910, 1010 and 1110 in that the request message from the AMF to the MN should be a PDU session resource modification request message instead of a PDU session resource setup request message, and only the additional UL TNL needs to be included in the PDU session resource modification request message instead of two UL TNLS. The existing UL TNL can be optional but not necessary to be included.

[0099] Also, in steps 1230, 1330 and 1430, the response message from the MN to the AMF should be a PDU session resource modification response message instead of a PDU session resource setup response message, and only the additional DL TNL and associated QoS flow need to be included in the PDU session resource modification response message instead of two DL TNLS and associated QoS flows, compared to steps 930, 1030 and 1130. The existing DL TNL and associated QoS flow can be optional but not necessary to be included in the response message.

[0100] Finally, in steps 1240, 1340 and 1440, the additional DL TNL address can be obtained from the SN using SN addition or MN initiated SN modification procedure, similar to steps 940, 1040 and 1140. The meaning of split PDU session (or PDU session splitting) is a PDU session whose QoS flows are served by more than one SDAP entity in the NG-RAN. This indicates that some QoS flows of the split PDU session are served by the SDAP of the MN, while the rest of the QoS flows are served by the SDAP of the SN. For non-split PDU session, its QoS flows can only be served by the SDAP of the MN or the SDAP of the SN. Therefore, the AMF can trigger PDU session splitting after SN addition. In this case, since the SN has been added before steps 910, 1010 and 1110, step 4 should be MN initiated SN modification.

[0101] The above description and drawings provide specific examples and implementations of the subject matter. However, the subject matter can be practiced in various ways, and therefore should not be construed as being limited to any example embodiments described herein. The subject matter recited in the following claims intends to have the broadest scope possible. In particular, the subject matter can be practiced in the form of a method, device, component, system, or non-transitory computer readable medium storing computer code. Embodiments can therefore, for example, take the form of hardware, software, firmware, storage media or any combination thereof. For example, the above method embodiments can be implemented by a component, device or system that includes a memory and a processor that executes computer code stored in the memory.

[0102] Throughout the specification and claims, the term can have a meaning that is suggested or implied by the context of use beyond the explicitly stated meaning. Also, the phrase "in one embodiment / implementation" as used herein does not necessarily refer to the same embodiment, and the phrase "in another embodiment / implementation" as used herein does not necessarily refer to a different embodiment. For example, the claimed subject matter can include a combination of example embodiments in whole or in part.

[0103] In general, the terminology can be understood at least in part from usage in context. For example, terms such as "and", "or", or "and / or" as used herein can include a variety of meanings that can depend at least in part upon the context in which such terms are used. Typically, "or" if used to associate a list, such as A, B or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B or C, here used in the exclusive sense. In addition, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular or can be used to describe combinations of features, structures or characteristics. Similarly, terms such as "a", "an", or "the" as used herein can be understood to convey a singular usage or a plural usage, depending at least in part on the context in which such terms are used. Also, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can allow for existence of additional factors not necessarily expressly described herein.

[0104] Reference throughout this specification to features, advantages, or similar language does not mean that all of these features and advantages in combination, or that they should be realized with any single aspect or combination of aspects of the solution. Rather, language referring to these features and advantages are understood to mean that a particular feature, advantage, or characteristic is included in at least one embodiment of the solution. Accordingly, descriptions of features and advantages, and similar language, throughout this specification may refer to the same embodiment or to different embodiments.

[0105] Furthermore, the described features, advantages, and characteristics of the solution can be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages can be recognized in light of the solutions that can not be present in all embodiments of the solution.

Claims

1. A method performed by a primary radio access network node (MN), comprising: Receive a request message from the core network associated with a PDU session for offloading the PDU session, the request message including the uplink communication address associated with the PDU session; as well as In response to the request message, and before the SN addition process of the target secondary radio access node (SN) for offloading the PDU session or the SN modification process initiated by the MN is completed: Generate a substitute downlink communication address for the target SN for the PDU session, wherein the substitute downlink communication address corresponds to the uplink communication address; as well as A response message is transmitted to the core network, the response message including the substitute downlink communication address of the target SN.

2. The method according to claim 1, further comprising: A set of Quality of Service (QoS) flows is assigned to the alternative downlink communication address, and the set of QoS flows is indicated to the core network in the response message.

3. The method according to claim 1, wherein, The uplink communication address includes at least one of the following: uplink transport network layer (TNL) address, uplink tunnel endpoint identifier (TEID) address, and user plane (UP) transport layer information.

4. The method according to claim 1, wherein, The alternative downlink communication address includes at least one of the following: downlink TNL address, downlink TEID address, and UP transport layer information.

5. The method according to claim 1, further comprising: The SN addition process or the SN modification process initiated by the MN is executed to use the target SN to offload the PDU session.

6. The method according to claim 5, wherein, The SN addition process or the SN modification process initiated by the MN includes: The MN transmits an SN add request message or an SN modify request message to the target SN; and Obtain the second downlink communication address associated with the target SN from the target SN.

7. The method according to claim 6, further comprising: In response to the completion of the SN addition process or the SN modification process initiated by the MN, the second downlink communication address is transmitted to the core network to replace the substitute downlink communication address.

8. The method of claim 7, further comprising: A set of QoS flows for the substitute downlink communication address is determined, and the core network is notified of the set of QoS flows through the response message; as well as The group of QoS flows that are the same as the target SN are notified by the SN add request message or the SN modify request message.

9. The method according to claim 1, wherein: The request message is a PDU session resource establishment request message used to establish the PDU session; and The request message includes a second uplink communication address assigned to the PDU session.

10. The method of claim 9, further comprising: A second downlink communication address is generated that points to the MN and corresponds to the second uplink communication address, wherein the substitute downlink communication address is generated as a copy of the second downlink communication address.

11. The method of claim 10, further comprising: Execute the SN addition process for the target SN or the SN modification process initiated by the MN, wherein the SN addition process or the SN modification process initiated by the MN includes: The MN transmits an SN add request message or an SN modify request message to the target SN; and Obtain the third downlink communication address associated with the target SN from the SN; and In response to the completion of the SN addition process or the SN modification process initiated by the MN, the third downlink communication address is transmitted to the core network to replace the substitute downlink communication address.

12. The method according to claim 1, wherein: The request message is a PDU session resource modification request message; and The substitute downlink communication address is generated as a copy of the existing downlink communication address of the PDU session associated with the MN.

13. The method of claim 12, further comprising: Execute the SN addition process for the target SN or the SN modification process initiated by the MN, wherein the SN addition process or the SN modification process initiated by the MN includes: The MN transmits an SN add request message or an SN modify request message to the target SN; and Obtain the second downlink communication address associated with the target SN from the SN; and In response to the completion of the SN addition process or the SN modification process initiated by the MN, the second downlink communication address is transmitted to the core network to replace the substitute downlink communication address.

14. A method performed by a core network node of a wireless communication network, comprising: Transmit a request message associated with the PDU session to the MN for offloading the PDU session, the request message including the uplink communication address associated with the PDU session; as well as A response message is received from the MN, the response message including a substitute downlink communication address of the target SN for the PDU session, wherein the response message is transmitted by the MN in response to the request message and before the completion of the SN addition process of the target SN for offloading the PDU session or the SN modification process initiated by the MN.

15. The method according to claim 14, wherein, The uplink communication address includes at least one of the following: uplink transport network layer (TNL) address, uplink tunnel endpoint identifier (TEID) address, and user plane (UP) transport layer information.

16. The method of claim 14, wherein, The alternative downlink communication address includes at least one of the following: downlink TNL address, downlink TEID address, and UP transport layer information.

17. The method of claim 14, further comprising: After the MN completes the SN addition process or the SN modification process initiated by the MN, the second downlink communication address is received from the MN; as well as Replace the substitute downlink communication address with the second downlink communication address.

18. The method of claim 17, further comprising: The response message receives an indication from the MN of a set of QoS flows for the alternative downlink communication address.

19. The method of claim 14, wherein: The request message is a PDU session resource establishment request message used to establish the PDU session; and The request message includes a second uplink communication address assigned to the PDU session.

20. The method of claim 19, further comprising: Receive a second downlink communication address from the MN that points to the MN and corresponds to the second uplink communication address, wherein the substitute downlink communication address is generated by the MN as a copy of the second downlink communication address.

21. The method of claim 20, further comprising: After the MN completes the SN addition process or the SN modification process initiated by the MN, the third downlink communication address transmitted by the MN is received. as well as Replace the substitute downlink communication address with the third downlink communication address.

22. The method of claim 14, wherein: The request message is a PDU session resource modification request message; and The substitute downlink communication address is generated as a copy of the existing downlink communication address of the PDU session associated with the MN.

23. The method of claim 22, further comprising: Receive a second downlink communication address from the MN, the second downlink communication address being generated after the SN addition process or the SN modification process initiated by the MN is completed; as well as Replace the substitute downlink communication address with the second downlink communication address.

24. An MN or core network node according to any one of claims 1 to 23, wherein the MN or core network node comprises a processor and a memory, wherein, The processor is configured to read computer code from the memory to cause the MN or the core network node to execute the method according to any one of claims 1 to 23.

25. A computer program product comprising a non-transitory computer-readable program medium, wherein computer code is stored in the non-transitory computer-readable program medium, the computer code, when executed by a processor of an MN or core network node according to any one of claims 1 to 23, causes the processor to implement the method according to any one of claims 1 to 23.

Images