WO2019033281A1

WO2019033281A1 - Methods and computing device for changing a user plane function

Info

Publication number: WO2019033281A1
Application number: PCT/CN2017/097550
Authority: WO
Inventors: Jinguo Zhu; Fei Lu
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2017-08-15
Filing date: 2017-08-15
Publication date: 2019-02-21
Anticipated expiration: 2020-02-15

Abstract

A method for changing a user plane function for a user equipment in a wireless network involves a computing device such as a session management function carrying out the following actions: when the user equipment is activating a protocol data unit session and has moved out of a service area of a first user plane function, establishing a tunnel for downlink data for the user equipment between the first user plane function and a second user plane function, but not between an anchor user plane function and the second user plane function; once the protocol data unit is deactivated, tearing down the tunnel between the first user plane function and the second user plane function and establishing a tunnel between the anchor user plane function and the second user plane function for downlink data.

Description

METHODS AND COMPUTING DEVICE FOR CHANGING A USER PLANE FUNCTION

TECHNICAL FIELD

The present disclosure is related generally to wireless networks and, more particularly, to methods and a computing device for changing a user plane function.

BACKGROUND

In modern cellular networks, each user plane function (UPF) has a service area. When a user equipment (UE) moves within the same UPF service area, there is no need to change the UPF. When the UE moves outside of the UPF service area, the UPF may need to be changed. The session management function (SMF) may provide the UPF service area to the access and mobility management function (AMF) , so when the AMF detect the UE move out or in the UPF service area, the AMF can send a notification the SMF so the SMF can decide to select a new UPF.

When a UE is in an IDLE mode, there is no radio resource control (RRC) connection and no N3 connection. When the UE needs to send uplink data or signalling, the UE initiates a Service Request procedure to establish the RRC connection and the N3 user plane. When the network needs to send downlink data or signalling to a UE in IDLE mode, the network needs to page the UE and the UE response with Service request procedure to establish the RRC connection and N3 user plane.

However, during the Service Request procedure, the UPF may be relocated. A tunnel is established between the old UPF and new UPF for downlink data forwarding. In the meantime, a tunnel is established between the new UPF and the anchor UPF so the anchor UPF can send downlink data directly to the new UPF. As a result, the new UPF may receive downlink data from the old UPF and the anchor UPF at the same time. This may cause downlink data to arrive out of order.

DRAWINGS

While the appended claims set forth the features of the present techniques with particularity, these techniques, together with their objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:

FIG. 1 is a diagram of a system in which various embodiments of the disclosure are implemented.

FIG. 2 shows an example hardware architecture, according to an embodiment.

FIG. 3 is a message flow diagram showing an example of currently existing method to recover the AMF when the UE initiates uplink signalling towards the network.

FIG. 4A and FIG. 4B are message flow diagrams of method for recovering an access management function for a user equipment according to different embodiments.

DESCRIPTION

In an embodiment, a method for changing a user plane function for a user equipment in a wireless network involves a computing device such as a session management function (e.g., computing device executing software that carries out a session management function) carrying out the following actions: when the user equipment is activating a protocol data unit session and has moved out of a service area of a first user plane function, establishing a tunnel for downlink data for the user equipment between the first user plane function and a second user plane function, but not between an anchor user plane function and the second user plane function； once the protocol data unit session is deactivated, tearing down the tunnel between the first user plane function and the second user plane function and establishing a tunnel between the anchor user plane function and the second user plane function for downlink data.

According to an embodiment, a method for changing a user plane function for a user equipment in a wireless network when the user equipment moves out of a service area of a first user plane function involves a computing device such as a session management function carrying out the following actions: receiving a protocol data unit session update message； in response to receiving the protocol data unit session update message, selecting the second user plane function； transmitting a session establishment request to the second user plane function； transmitting a session modification request to the first user plane function, wherein the session modification request indicates that the first user plane function is to establish a tunnel to the second user plane function for downlink data for the user equipment； and establishing a tunnel between an anchor user plane function and the second user plane function for downlink data only after the protocol data unit session is inactive.

Table 1 lists various abbreviations used in the present disclosure, along with their expanded forms.

Abbreviation	Expansion
AN	Access Network
AMF	Access and Mobility Management Function
CN	Core Network
DNS	Domain Name System
DNN	Data Network Name
GUAMI	Globally Unique AMF Identifier
GUTI	Globally Unique Temporary Identifier
IMSI	International Mobile Subscriber Identity
IP	Internet Protocol
MM	Mobility Management
NAS	Non-Access Stratum
PDN	Packet Data Network
PDU	Protocol Data Unit
PLMN	Public Land Mobile Network
QoS	Quality of Service
RAN	Radio Access Network
RAT	Radio Access Technology


SGW	Serving Gateway
SM	Session Management
SMF	Session Management Function
TAI	Tracking Area Identity
TEID	Tunnel Endpoint Identifier
TFT	Traffic Flow Template
UE	User Equipment
UL	Uplink
UPF	User Plane Function
5G-RAN	5G Radio Access Network
N2AP	N2 application protocol
CDB	Context database
5G-GUTI	Globally Unique Temporary Identity
5G-S-TMSI	5G S-Temporary Mobile Subscriber Identity
GUAMI	Globally Unique AMF ID

Table 1

Turning to FIG. 1, a wireless communication system in which the various embodiments may be deployed is shown. In FIG. 1, there is depicted a UE 102, a RAN 104, an an AMF 106, an SMF 110, a first UPF (also referred to as an “old UPF” ) 112, a second UPF (also referred to as a “new UPF” ) 114, and an anchor UPF 116. Each of these components is implemented on computer hardware, although the components are often referred to by their respective functions. For example, the AMF 106 is, in an embodiment, a computing device that executes software implementing an access management function. This is also true of, for example, the SMF 110 (an embodiment of which is a computing device executing software implementing a session management function) and each UPF (an embodiment of which is a computing device executing software implementing a user plane function) and each component may be a separate, independent piece of hardware from the other components. These various components communicate with one another via interfaces denoted by the lines between them, including the N2, N3, N9, and N11 reference points.

Though not shown in FIG. 1, the RAN 104 includes many communication nodes such as one or more enhanced or next generation Node Bs, each of which may include one or more base stations, and each of which may define one or more wireless cells. The RAN, a base station 104.

Possible implementations of the UE 102 include any device capable of wireless communication, such as a smartphone, tablet, laptop computer, and non-traditional devices (e.g., household appliances or other parts of the “Internet of Things” ) .

According to an embodiment, the AMF 106 (i.e., a computing device executing software that carries out the AMF) carries out one or more of the following procedures in support of the RAN 104: registration management, connection management, reachability management and mobility management. The AMF 106 also carries out access authentication and access authorization, acts as the NAS security termination, and relays the SM NAS between the UE 102 and the SMF, etc. NAS is a layer over which signal communication between the UE and the core network takes place.

In an embodiment, the SMF 110 carries out session management (e.g., for PDU sessions) , allocates IP addresses to UEs (including optional authorization functions) , and selects and controls the UPF 112 for data transfer. If a UE 102 has multiple PDU sessions, different SMFs may be allocated to each session to manage.

Each UPF (i.e., a computing device executing software that carries out the UPF) carries out procedures in support of RANs such as: acting as an anchor point for mobility between and within RATs, packet routing and forwarding, traffic usage reporting, quality-of-service handling for the user plane, downlink packet buffering, downlink data notification triggering, etc.

FIG. 2 illustrates a basic (computing device) hardware architecture implemented by the elements of FIG. 1, including the according to an embodiment. The elements of FIG. 1 have other components as well. The hardware architecture depicted in FIG. 2 includes logic circuitry 202, memory 204, transceiver 206, and one more antennas represented by antenna 208. The memory 204 may be or include a buffer that, for example, holds incoming transmissions until the logic circuitry is able to process the transmission. Each of these elements is communicatively linked to one another via one or more data pathways 210. Examples of data pathways include wires, conductive pathways on a microchip, and wireless connections.

The term “logic circuitry” as used herein means a circuit (atype of electronic hardware) designed to perform complex functions defined in terms of mathematical logic. Examples of logic circuitry include a microprocessor, a controller, or an application-specific integrated circuit. When the present disclosure refers to a device carrying out an action, it is to be understood that this can also mean that logic circuitry integrated with the device is, in fact, carrying out the action.

Possible implementations of the memory 204 include: volatile data storage； nonvolatile data storage, electrical memory, magnetic memory, optical memory, random access memory ( “RAM” ) , cache memory, and hard drives.

In FIG. 3 through FIG. 5, various components are shown engaging wireless and wired communication. These components have the same structure and basic functionality as described above in conjunction with FIG. 1 and FIG. 2. FIG. 4 and FIG. 5 depict additional and novel functionality, which is described in more detail in the accompanying description.

Turning to FIG. 3, an example of a currently existing network initiated Service request procedure. In this procedure, the AMF may detect that the UE moves outside of a UPF service area and a new UPF may need to be selected.

At 351, the anchor UPF 316 sends downlink data to the old UPF 312.

At 352, the old UPF 312 buffers the downlink data and sends a downlink data notification to the SMF 310.

At 353, the SMF 310 sends a downlink data notification to the AMF 306. This message includes the SUPI (5G Subscription Permanent Identifier) to identify the UE 302 and a protocol data unit (PDU) session ID to identify the PDU session over which the downlink data are received. This message also includes the Session related information such as Quality of Service (QoS) flow information and the old UPF N3 tunnel information..

At 354, the AMF 306 finds the UE context based on the SUPI and sends a paging request (5G-S-TMSI, paging priority) to all RAN within the Registration area. The 5G-S-TMSI is the short temporary identifier of the UE. The PDU session ID may be used to decide the paging priority.

At 355, the RAN 304 sends Paging request (5G-S-TMSI) over the air.

At 356, when the UE 302 receives the Paging request from the RAN 304, it sends RRC connection request to the RAN 304 to establish the RRC connection. This RRC connection request message includes the 5G-S-TMSI..

At 357, the UE 302 sends a NAS Service Request over the RRC connection to the RAN 304. The RAN 304 selects the AMF according the 5G-S-TMSI received at 356. The RAN 304 forwards the NAS service request message to the AMF 306, together with the current UE location information.

At 358, based on the current UE location the AMF may detects the UE moves outside of the service area of the UPF, it hold the procedure and sends PDU session update to SMF, together with the current UE location information. If the AMF 306 determines that the UE 304 is within the UPF service area, steps 359-362 are skipped.

At 359, the SMF 310 may select a new UPF 314 and send an N4 Session establishment request to the new UPF 314. The new UPF 314 may allocate three tunnels: one towards the anchor UPF 316 for normal N9 downlink data, one towards the RAN 304 for normal N3 uplink data, and one towards the old UPF 312 for data forwarding. The SMF 310 also provides the new UPF 314 about the anchor UPF N9 tunnel information to send uplink data. The new UPF responds by transmitting an N4 Session establishment response to the SMF 310.

At 360, the SMF 310 sends an N4 Session modification request to the anchor UPF 316 to update the new UPF N9 tunnel information. From this step, the anchor UPF 316 can start to send downlink data towards the new UPF 314.

At 361, the SMF 310 sends an N4 Session modification request to the old UPF 312 to establish the data forwarding tunnel. The SMF 310 start a timer to monitor the data forwarding. From this step, the new UPF 314 may receive forwarded data from the old UPF 312.

At 362, the SMF 310 sends PDU session Response to the AMF 306. This message includes the new UPF N3 tunnel information, Session related information such as QoS flow information.

At 363, the AMF 306 sends an N2 message to the RAN 304. This message includes the UPF N3 tunnel information (new UPF in case of UPF change) , Session related information such as QoS flow information received from the SMF.

At 364, the RAN 304 performs an RRC reconfiguration to establish the dedicated radio bearer for the PDU session based on the information received from AMF 306.

At 365, the RAN 304 allocates N3 tunnel information and sends an N2 UE context setup response message to the AMF 306, including the RAN N3 tunnel information.

At 366, the AMF 306 sends a PDU session update to the SMF 310, including the RAN N3 tunnel information.

At 367, the SMF 310 sends an N4 Session modification request to the new UPF 314, to update the RAN 3 tunnel information. From this step, the downlink data can be sent to the RAN 304.

At 368, the SMF 310 sends an N4 Session modification response to the AMF 306.

At 369, after the timer in step 361 expires, the SMF 310 send an N4 Session Release procedure to the old UPF 312 to release the resources of the data forwarding tunnel.

At 370, after the timer in step 361 expires, the SMF 310 sends and N4 Session Modification procedure to the new UPF 314 to release the resources of the data forwarding tunnel.

As can be seen from the preceding description of FIG. 3, in step 360 and 361, the new UPF may receive downlink data from the old UPF and from the anchor UPF at the same time. This may cause the downlink data to arrive out of order which, for some applications, may be disruptive.

According to an embodiment, in order to make sure that the UPF does not receive downlink data from both the anchor UPF and the new UPF at the same time, the establishment of an N9 tunnel between the new UPF and the anchor UPF is delayed until the PDU session becomes inactive. Thus, while the PDU session is active, the downlink data is only sent via the old UPF to new UPF. One implementation of this embodiment is illustrated in FIG. 4A, which will now be described.

At 451, the anchor UPF 416 sends downlink data to the old UPF 412.

At 452, the old UPF 412 buffers the downlink data and sends downlink data notification to SMF 410.

At 453, the SMF 410 sends a downlink data notification to the AMF 406. This message includes the SUPI (5G Subscription Permanent Identifier) to identify the UE 402 and a PDU session ID to identify the PDU session over which the downlink data is received. This message also includes the Session related information such as QoS flow information and the old UPF N3 tunnel information.

At 454, the AMF 406 finds the UE context based on the SUPI and sends a paging request (5G-S-TMSI, paging priority) to all RANs within the Registration area. The 5G-S-TMSI is the short temporary identifier of the UE. The PDU session ID may be used to decide the paging priority.

At 455, the RAN 404 sends a Paging request (5G-S-TMSI) over the air.

At 456, when the UE 402 receives the Paging request from the RAN 404, it responds by sending an RRC connection request message to the RAN 404 to establish the RRC connection. This RRC connection request message includes the 5G-S-TMSI.

At 457, the UE 402 sends a NAS Service Request over the RRC connection to the RAN 404. The RAN 404 selects the AMF according the 5G-S-TMSI received in step 456. The RAN 404 forwards the NAS service request message to the AMF 406, together with the current location information for the UE 402.

At 458, based on the current UE location, if the AMF 406 determines that the UE 402 has move outside of the service area of the old UPF 412 then, based on this determination, the AMF 406 holds the procedure (e.g., refrains from establishing the tunnel from the anchor UPF 416) and sends a PDU session update to the SMF 410, together with the current location information. If the AMF 406 determines that the UE 402 is still within the UPF service area, steps 459-461 are skipped.

At 459, the SMF 410 selects a new UPF (UPF 414 in this example) and sends the N4 Session establishment request to the new UPF 414. The new UPF 414 may allocate two tunnels: one towards the RAN 404 for normal N3 uplink data and one N9 towards the old UPF 412 for N9 downlink data. The SMF 410 also provides the anchor UPF 416’s N9 tunnel information to the new UPF 414 so that the new UPF 414 can send uplink data to the anchor UPF 416. The new UPF 414 responds by transmitting an N4 Session establishment response to the SMF 410. In summary, the new UPF 414 will send uplink data to the anchor UPF 416 and receive downlink data from the old UPF 412.

At 460, the SMF 410 sends an N4 Session modification request to the old UPF 412 to establish the N9 tunnel between the new UPF 414 and the old UPF 412. From this step, the new UPF 414 receives forwarded data from the old UPF 412.

At 461, the SMF 410 sends a PDU session Response to the AMF 406. This message includes the new UPF N3 tunnel information and Session related information such as QoS flow information.

At 462, the AMF 406 sends an N2 UE context setup message to the RAN 404. This message includes the UPF N3 tunnel information (new UPF in case of UPF change) and Session related information such as QoS flow information received from the SMF 410.

At 463, the RAN 404 performs RRC reconfiguration to establish the dedicated radio bearer for the PDU session based on the information received from the AMF 406.

At 464, the RAN 404 allocates N3 tunnel information and sends an N2 UE context setup response message to the AMF 406, including the RAN N3 tunnel information.

At 465, the AMF 406 sends a PDU session update to the SMF 410, including the RAN N3 tunnel information.

At 466, the SMF 410 sends an N4 Session modification request to the new UPF 414 in order to update the RAN 3 tunnel information. From this step, the downlink data can be sent from new UPF 414 to the RAN 404.

At 467, the SMF 410 sends an N4 Session modification response to the AMF 406.

According to an embodiment, once the UE deactivates the PDU session, the SMF re-establishes the N9 tunnel between the new UPF and the anchor UPF. Accordingly, FIG. 4B shows a continuation of the procedure of FIG. 4A, with the assumption that the UE 402 deactivates the PDU session.

At 468, the AMF 406 determines to deactivate the PDU session. The RAN context therefore needs to be released, which the AMF 406 begins doing.

At 469, the AMF 406 sends a PDU session Deactivation request to the SMF 410.

At 470, the SMF 410 sends an N4 Session modification request to the anchor UPF 416 to update the N9 tunnel information of the new UPF 414. From this step, the N9 tunnel between the new UPF 414 and the anchor UPF 416 is established to send both uplink and downlink data.

At 471, the SMF 410 sends a PDU session deactivation ACK to the AMF 406.

At 472, if RAN context has not been released yet, then the AMF 406 sends a UE context release command to the RAN 404.

At 473, the RAN 404 releases the RRC connection.

At 474, after all radio resources have been released, the RAN 404 sends a UE context release complete message to the AMF 406.

At 475, the SMF 410 also releases the resources of the old UPF 412.

Any and all of the methods described herein are carried out by or on one or more computing devices. Furthermore, instructions for carrying out any or all of the methods described herein may be stored on a non-transitory, computer-readable medium, such as any of the various types of memory described herein.

It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from their spirit and scope of as defined by the following claims. For example, the steps of the various methods can be reordered in ways that will be apparent to those of skill in the art.

Claims

A method for changing a user plane function for a user equipment in a wireless network, the method comprising:

when the user equipment activating a protocol data unit session and has moved out of a service area of a first user plane function, establishing a tunnel for downlink data for the user equipment between the first user plane function and a second user plane function, but not between an anchor user plane function and the second user plane function；

once the protocol data unit session is deactivated, tearing down the tunnel between the first user plane function and the second user plane function and establishing a tunnel between the anchor user plane function and the second user plane function for downlink data.
The method of claim 1, wherein establishing a tunnel for downlink data for the user equipment between the first user plane function and a second user plane function comprises transmitting a session modification request to the first user plane function.
The method of claim 1, further comprising:

establishing a tunnel for uplink data between the second user plane function and the anchor user plane function to facilitate the second user plane function sending uplink data to the anchor user plane function.
The method of claim 1, wherein establishing a tunnel for downlink data for the user equipment between the first user plane function and a second user plane function comprises transmitting a session modification request to a radio access network to which the user equipment is operating, wherein the session modification request includes data to allow the second user plane function to transmit downlink data to the radio access network.
The method of claim 1, further comprising:

receiving a protocol data unit session deactivation message from an access and mobility management function that serves the user equipment； and

carrying out the tearing down step in response to receiving the protocol data unit deactivation message.
The method of claim 1, wherein establishing a tunnel between the anchor user plane function and the second user plane function for downlink data comprises transmitting a session modification request to the anchor user plane function.
The method of claim 1, further comprising selecting the second user plane function.
A method for changing a user plane function for a user equipment in a wireless network when the user equipment moves out of a service area of a first user plane function, the method comprising:

receiving an update message for a protocol data unit session；

in response to receiving the protocol data unit session update message, selecting the second user plane function；

transmitting a session establishment request to the second user plane function； and

transmitting a session modification request to the first user plane function, wherein the session modification request indicates that the first user plane function is to establish a tunnel to the second user plane function for downlink data for the user equipment； and

establishing a tunnel between an anchor user plane function and the second user plane function for downlink data when the protocol data unit session is deactivated.
The method of claim 8, further comprising:

establishing a tunnel for uplink data between the second user plane function and the anchor user plane function to facilitate the second user plane function sending uplink data to the anchor user plane function.
A computing device configured to carry out the method of any one of claims 1 through 9.
A non-transitory computer-readable medium having stored thereon computer-executable instructions for carrying out any one of claims 1 through 8.