WO2018223311A1

WO2018223311A1 - Methods and computing device for facilitating handover from a first network to a second network

Info

Publication number: WO2018223311A1
Application number: PCT/CN2017/087430
Authority: WO
Inventors: Fei Lu; Zhendong Li; Jinguo Zhu
Original assignee: Zte Corporation
Priority date: 2017-06-07
Filing date: 2017-06-07
Publication date: 2018-12-13

Abstract

A method for facilitating handover in a wireless network involves (e.g., a user equipment) receiving a globally unique temporary identifier from an access and mobility management function that serves the second radio access network, registering with the access and mobility management function via a third radio access network (which may be an untrusted network) that has a radio access technology that is different from that of the first radio access network and the second radio access network, and transmitting an attach request message or a tracking area update containing the globally unique temporary identifier to a mobility management entity that serves the first radio access network.

Description

METHODS AND COMPUTING DEVICE FOR FACILITATING HANDOVER FROM A FIRST NETWORK TO A SECOND NETWORK

TECHNICAL FIELD

The present disclosure is related generally to wireless networks and, more particularly, to methods and a computing device for facilitating handover from a first network to a second network.

BACKGROUND

In currently proposed systems, when a device has to go through a handover procedure from one network (e.g., a fourth generation network) to another network (e.g., a fifth generation network) , but the device has registered with the access and mobility management function via a third network that is not part of the traditional cellular networks (e.g., a public wireless hotspot) , then there is no reliable mechanism for keeping the same access and mobility management function during the handover. As a result, the user may experience an interruption in certain services (e.g., such as packet data unit services) .

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 and FIG. 4 are message flow diagrams showing how a user equipment obtains a temporary identifier and provides the identifier to a network to facilitate handover, according to different embodiments.

FIG. 5 is a message flow diagram depicted how a mobility management entity keeps the same access and mobility management function during a handover, according to an embodiment.

DESCRIPTION

The present disclosure is generally directed to a method for facilitating handover in a wireless network. According to various embodiments, a method for carrying out a handover from a first radio access network to a second radio access network involves (e.g., a user equipment) receiving a globally unique temporary identifier from an access and mobility management function that serves the second radio access network, registering with the access and mobility management function via a third radio access network (which may be an untrusted network) that has a radio access technology that is different from that of the first radio access network and the second radio access network, and transmitting an attach request message (containing the globally unique temporary identifier) to a mobility management entity that serves the first radio access network.

In an embodiment, the method involves receiving a registration accept message from the access and mobility management function in response to registering with the access and mobility management function, in which the globally unique temporary identifier is included with the registration accept message.

In various embodiments, the globally unique temporary identifier received from the access and mobility management function corresponds to the radio access technology of the second radio access network, and the attach request message further includes a globally unique temporary identifier that corresponds to the radio access technology of the first radio access network, which was previously received from the mobility management entity.

According to an embodiment, a device that carries out the method (e.g., a user equipment) ceases communicating via the first radio access network (e.g., a fourth generation network) and begins communicating with the second radio access network (afifth generation network) .

In various embodiments, a method for carrying out a handover from a first radio access network to a second radio access network involves a device (e.g., a user equipment) receiving a globally unique temporary identifier from an access and mobility management function that serves the second radio access network, registering with the access and mobility management function via a third radio access network (which may be untrusted) that has a radio access technology that is different from that of the first radio access network and the second radio access network, and transmitting a tracking area update message, which includes the globally unique temporary identifier, to a mobility management entity that serves the first radio access network.

In some embodiments, a device registers with the access and mobility management function only after registering with the first radio access network.

According to various embodiments, a mobility management entity carries out the following actions in order to facilitate a handover from a first radio access network to a second radio access network: receiving a globally unique temporary identifier from a user equipment that is operating on the first radio access network, in which the globally unique temporary identifier that was obtained by the user equipment while it was operating on a third radio access network whose radio access technology is different from that of both the first and second radio access networks (and which may be an untrusted network) ； using the received globally unique temporary identifier to determine a globally unique mobility management entity identifier； and using the globally unique mobility management entity identifier to select an access and mobility management function for the user equipment on the second radio access network (which, by design, ends up being the original access and mobility management function) .

In an embodiment, the mobility management entity uses the globally unique mobility management entity identifier as follows: it determines whether the second network can serve the user equipment based on the globally unique mobility management entity identifier. To make this determination according to an embodiment, the mobility management entity: obtains the identity of the second network from the globally unique mobility management entity identifier, carries out a domain name service lookup based on the identity of the second network, receives, (in response to the lookup) a list of valid access and mobility management functions for the second radio access network, and selects an access and mobility management function from the list, which, by design, should be the same access and mobility management function.

The mobility management entity may receive the globally unique mobility management entity identifier from the user equipment in, for example, an attach request message or a tracking area update message.

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

Table 1

In currently proposed systems, when a UE registers to access (via a 3GPP or non-3GPP RAT) a first network and also registers to access a second network, if the second access is part of the same PLMN (e.g. the UE is registered via a 3GPP access and selects a N3IWF located in the same PLMN) , the UE uses the temporary UE identifier that the UE received from when it registered with the first network for registering with the second network.

For example, consider the following scenario (1) UE first registers to an AMF via N3IWK and the AMF allocates a GUTI to the UE. (2) The UE then needs to connect to an NG RAN (e.g., a 5G network) , and the NG RAN is part of the same PLMN, so the UE sends the temporary UE id to the NG RAN, and the NG RAN will select the same AMF based on the temporary UE id.

However, if one changes the above scenario to where the UE first connects to an eNB (e.g., on a 4G network) and then needs to handover to a NG RAN, there is currently not a way for the eNB/MME to “know” how to select the same AMF. If the same AMF is not selected at the PLMN, then the non-3GPP service will be disconnected. This will impact the user experience.

In order to account for this scenario according to an embodiment, the following techniques are disclosed: The UE sends the GUTI_5G to the MME in an Attach Request or a TAU Request message, wherein the GUTI_5G was previously allocated by the AMF when the UE connected to the AMF via non-3GPP access. The MME (1) receives the GUTI_5G in the Attach Request or TAU Request message from the UE, and (2) selects the GUAMI (based on the GUTI_5G) to serve the UE in the target NG RAN during the handover from the E-UTRAN (e.g., the 4G network) to the NG RAN (e.g., the 5G network) (connecting to the AMF via 3GPP access) .

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, an eNB 104, an NG RAN 105, an N3IWK 106, an HSS 107, an MME 108, an SGW 109, an AMF 110, an SMF/PGW-C 112, and a UPF 114. These various components (each of which operates on at least one computing device) communicate with one another via interfaces denoted by the lines between them, including the N2, N4, N8, and N11 reference points, the 4G NAS, and the LTE-Uu, S1-U, S1-C, S5/S8, S6a, and S11 interfaces.

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” ) . Possible implementations of the eNB 104 include a 4G base station within an LTE network. Possible implementations of the NG RAN 105 include a 5G wireless network. Possible implementations of the N3IWK 106 include a public wireless network (e.g., a WiFi hotspot) .

According to an embodiment, the HSS 107 handles user identification and addressing (e.g., through the use of subscriber identity numbers) and generates security information from user identity keys.

In an embodiment, the MME 108 carries out the following functions for the LTE network that it serves: tracking and paging, bearer activation and deactivation, selecting the SGW for a UE during initial attachment, authenticating a user (using the HSS 107) during handover, serving as the termination point for all NAS signaling, and generating the GUTI.

According to an embodiment, the SGW 109 acts as an interface for signalling between the PGW (part of block 112) and the MME 108. Each UE is served by a single SGW at a time. The SGW also handles IP packets between the PGW and the eNB 104.

According to an embodiment, the AMF 110 (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 NG RAN 105: registration management, connection management, reachability management and mobility management. The AMF 110 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 communication between the UE and the core network (e.g., 4G core or 5G core) takes place.

In an embodiment, the SMF (part of the PGW-C/SMF block 112) carries out session management (e.g., for PDU sessions) , allocates IP addresses to UEs, and selects and controls the UPF 114 for data transfer. If a UE 102 has multiple PDU sessions, different SMFs may be allocated to each session to manage. The PGW-C (also part of block 112) is the control plane that serves as the termination point of the packet data interface with respect to the PDN. It also serves as an anchor point for sessions with external PDNs.

The UPF 114 (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.

Though not shown in FIG. 1, the eNB 104 may be one of many communication nodes in an LTE network. Similarly, the NG RAN 105 includes many communication nodes such as one or more gNBs.

FIG. 2 illustrates a basic (computing device) hardware architecture implemented by the elements of FIG. 1, including the UE 102 and the MME 108, 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.

Turning to FIG. 3 a process by which the UE 102 obtains a 5G GUTI and provides it to the MME according to an embodiment, will now be described. The 5G_GUIT is initially allocated by the AMF 110 when the UE 102 connects to the AMF 110 via the N3IWK 106. In this procedure, the UE firsts connects to N3IWK 106 and then connects to the E-UTRAN (i.e., the 4G RAN of which the eNB 104 is part) .

At 302, the UE 102 registers to the AMF 110 via an untrusted non-3GPP access network. During this procedure, the AMF 110 will allocate a 5G GUTI to the UE 102 in the Registration Accept message (details for an example of this allocation process are documented in 3GPP TS 23.502 v0.3.0, subclause 4.12.2) . In summary, the UE 102 is registered to the AMF 110 via an untrusted non-3GPP access network. After that, the UE requests that the SMF establish a PDU session, which the SMF does.

At 304, The UE 102 sends an Attach Request to the MME 108. The Attach Request includes the UE identity and the ESM message container. The UE identity is the GUTI_4G, which is allocated by the MME 108, or the UE IMSI if the UE does not have the 4G GUTI. The ESM message container includes a PDN connectivity request message. The PDN connectivity request message contains the PDN type and the APN. The UE 102 includes the GUTI_5G (which was allocated by the AMF 110) in the Attach Request message.

At 306, the MME 108 selects the PGW-C based on the APN information and sends a Create Session Request (with the IMSI, APN, MME IP address and TEID information, UE location information, APN, PDN type, Bearer ID, Bearer QoS, APN-AMBR) message to the selected PGW-C.

At 308, the PGW-C 112 selects the UPF based on the location information and/or the APN information and sends the Sx Session Establishment request message (PGW-C address, IMSI, Bearer QoS, Bearer ID, APN-AMBR) to the UPF 114.

At 310, if the UPF 114 allocates the UPF TEID and address, the UPF responds with a Sx Session Establishment Response message to the PGW-C 112. It includes the UPF TEID and the IP address.

At 312, the PGW-C 112 sends a Create Session Response message (UPF TEID and IP address, PGW-C TEID and IP address, Bearer QoS, Bearer ID, Bearer TFT) to the MME 108.

At 314, the PGW-C 112 sends a Create Session Response message (Bearer TFT, UPF TEID and IP address, PGW-C TEID and IP address) to the MME 108.

At 316, the MME 108 sends an S1 UE context request to the eNB 104. This message will contain the Attach Accept message, uplink UPF TEID and IP address for user plane, E-RAB ID and E-RAB QoS and UE-AMBR. The Attach Accept message contains the ESM message container, GUTI_4G, TAI list. The ESM message container includes the Activate default Bearer Request (APN, PDN type, Bearer ID, Bearer QoS, Bearer TFT) to establish the default bearer.

At 318, the eNB 104 sends the RRC connection configuration to the UE 102 to establish the data radio bearer for the UE 102. The Attach accept message will be included as a container and sent to the UE 102.

At 320, the UE 102 responds with an Attach Complete message (to confirm that the GUTI_4G is valid) and the Activate default bearer response. The message will be included in the RRC connection configuration ACK message to the eNB 104.

At 322, the eNB 104 sends an S1 UE context response (including the eNodeB TEID and IP address for downlink packets, Bearer Id, Attach Complete) to the MME 108. The MME 108 will also receive the Attach complete message and Activate default bearer response.

At 324, the MME 108 sends the Modify bearer Request (including the eNodeB address and TEID, Bearer ID) message to the PGW-C 112.

At 326, the PGW-C 112 sends the Sx Session Modification Request (eNodeB address and TEID, Bearer ID) to the UPF 114.

At 328, the UPF 114 responds with a Sx Session Modification Response message.

At 330, The PGW-C 112 responds with the Modify Bearer Response message to the MME 108.

Turning to FIG. 4 a process by which the UE 102 obtains a 5G GUTI via an untrusted non-3GPP network after having registered with an E-UTRAN according to an embodiment will now be described. In this example, the UE 102 first connects to an E-UTRAN system (i.e., a 4G network of which eNB 104 is a part) . Then, the UE 102 registers to the AMF 110 via an untrusted non-3GPP access network and the AMF 110 allocates the GUTI_5G to the UE 102. Furthermore, in this procedure, the UE 102 updates the GUTI_5G to the MME 108 after the UE 102 gets the GUTI_5G from the AMF 110.

At 402, the UE registers to AMF via untrusted non-3GPP access network. During this procedure, the AMF will allocate a 5G GUTI to the UE 102 in the Registration Accept message. (Details for an example of this allocation procedure are documented in the 3GPP TS 23.502 v0.3.0 subclause 4.12.2)

At 404, since the UE 102 has registered to E-UTRAN system, the UE 102 will trigger the TAU procedure to update the GUTI_5G to the MME 108. Therefore, the UE 102 sends the TAU Request to the MME 108. The TAU Request includes the UE identity. The UE identity is in the form of a GUTI_4G, which is allocated by the MME 108. Since the UE 102 has registered to the AMF 110 via an untrusted non-3GPP access network, the UE 102 also includes the GUTI_5G, which was allocated by the AMF 110, in the TAU request message.

At 406, the MME 108 sends the Modify bearer Request message to the PGW-C 112.

At 408, the PGW-C 112 sends the Sx Session Modification Request to the UPF 114.

At 410, the UPF 114 responds with an Sx Session Modification Response message.

At 412, the PGW-C 112 responds with the Modify Bearer Response message to the MME 108.

At 414, The MME 108 sends the TAU Accept message to the UE 102.

Referring now to FIG. 5, an example of how the MME 108 identifies and selects the same AMF during handover (e.g., 4G to 5G handover) , given that the UE 102 had registered with the AMF via an untrusted non-3GPP network, will now be described according to an embodiment.

At 502, the source eNB 104 decides to perform a handover procedure, and therefore sends a Handover Required message (including a Source to Target transparent container, target ID) to the source MME 108. The Source to Target transparent container includes all active E-RABs.

At 504, the MME 108 checks the GUAMI (which it has derived from the GUTI_5G it received from the UE 102 via one of the procedures set forth in FIG. 3 and FIG. 4 and the accompanying descriptions thereof) . For example, the MME 108 performs a DNS lookup based on the target ID, and the DNS will respond with valid AMF lists. The MME 108 will look up the GUAMI in the AMF list and, since the AMF 110 had generated the GUAMI (and incorporated it into the GUTI_5G that it provided to the UE 102) , the result of the lookup with be the identity of the AMF 110. The MME 108 sends the Forward Relocation Request (Source to Target transparent container, target ID, MME address and TEID, Bearer context and MM context) to the selected AMF (i.e., the same AMF—AMF 110) .

At 506, the AMF 110 selects the SMF/PGW-C based on the Bearer Context, sends the N11 Session Modification Request (including the IMSI, AMF IP address and TEID, PDU session information) message to the selected SMF/PGW-C.

At 508, the SMF 112 responds with the N11 Session Modification Response message to the AMF 108.

At 510, the AMF 110 sends the Handover Request (which includes the Source to Target transparent container and the MM N2 information) to the target RAN (NG RAN 105 in this example) . The AMF 110 determines the Target RAN based on the Target ID. The Source to Target transparent container is forwarded as received from the source eNB (eNB 104) . The MM N2 information includes, e.g., security information and a Handover Restriction List.

At 512, the target RAN (NG RAN 105) sends a Handover Request Acknowledge (including a Target to Source transparent container, PDU sessions failed to be setup list, N2 SM information) to AMF. The Target to Source transparent container includes a UE container with an access stratum part. The UE container is sent transparently via the AMF 110 to the UE 102. The information provided to the source eNB (eNB 104) also contains a list of Bearers (mapped from PDU sessions) indicating PDU sessions that were failed to be setup and the reason (s) for failure. The AMF 110 sends separate request (s) to the relevant SMF (s) to release the failed PDU session (s) . The N2 SM information contains the NG RAN address and TEID for downlink User Plane for all accepted PDU sessions.

At 514, the AMF 110 sends the Forward Relocation Response message (AMF address and TEID, Target to Source transparent container ) to the MME 108.

At 516, the source MME 108 sends the Handover Command message to the eNB 104.

At 518, the Source eNB (eNB 104) sends the Handover Command message to the UE 102.

At 520, the UE 102 is synchronized to the target cell (e.g., a gNB in the NG RAN 105) and the UE 102 sends the Handover Confirm message to the target NG RAN (NG RAN 105) .

At 522, NG RAN 105 sends the Handover Notify message (includes location information such as TAI) to the AMF 110.

At 524, the AMF 110 sends the N11 Session Modification Request message (includes NG RAN address and TEIDs for downlink User Plane) to the SMF 112.

At 526, the SMF 112 sends an N4 Session Modification Request (NG RAN address and TEIDs for downlink User Plane) message to the UPF 114.

At 528, The UPF 114 sends an N4 Session Modification Response message to the SMF 112.

At 530, The SMF 112 responds with an N4 Session Modification Response message to the AMF 110.

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 carrying out a handover from a first radio access network to a second radio access network, the method comprising:

registering with an access and mobility management function via a third radio access network having a radio access technology that is different from that of the first radio access network and the second radio access network；

receiving a globally unique temporary identifier from the access and mobility management function； and

transmitting an attach request message to a mobility management entity that serves the first radio access network,

wherein the attach request message includes the globally unique temporary identifier.
The method of claim 1, further comprising:

in response to registering, receiving a registration accept message from the access and mobility management function,

wherein the globally unique temporary identifier is included with the registration accept message.
The method of claim 1, wherein the third radio access network is an untrusted network.
The method of claim 1, wherein

the globally unique temporary identifier received from the access and mobility management function corresponds to the radio access technology of the second radio access network,

the attach request message further includes a globally unique temporary identifier that corresponds to the radio access technology of the first radio access network, which was previously received from the mobility management entity.
The method of claim 1, further comprising:

ceasing communication with the first network； and

beginning communicating with the second radio access network.
A method for carrying out a handover from a first radio access network to a second radio access network, the method comprising:

registering with the access and mobility management function via a third radio access network having a radio access technology that is different from that of the first radio access network and the second radio access network；

receiving a globally unique temporary identifier from an access and mobility management function that serves the second radio access network； and

transmitting a tracking area update message to a mobility management entity that serves the first radio access network,

wherein the tracking area update message includes the globally unique temporary identifier.
The method of claim 6, further comprising:

in response to registering, receiving a registration accept message from the access and mobility management function,

wherein the globally unique temporary identifier is included with the registration accept message.
The method of claim 6, wherein the third network is an untrusted network.
The method of claim 6, wherein

the globally unique temporary identifier is specific to a radio access technology of the second radio access network, and

the tracking area update also includes a globally unique temporary identifier that is specific to the radio access technology of the first radio access network.
The method of claim 6, further comprising:

registering with the first radio access network； and

registering with the access and mobility management function only after registering with the first radio access network.
A method for carrying out a handover from a first radio access network to a second radio access network, the method comprising:

a mobility management entity receiving a globally unique temporary identifier from a user equipment that is operating on the first radio access network,

wherein the globally unique temporary identifier was allocated by an access and mobility management function when the user equipment was operating in a third radio access network, which has a radio access technology that is different from that of the first radio access network and the second radio access network；

the mobility management entity using the received globally unique temporary identifier to determine a globally unique mobility management entity identifier； and

the mobility management entity using the globally unique mobility management entity identifier to select the access and mobility management function for the user equipment on the second radio access network.
The method of 11, wherein using the globally unique mobility management entity identifier to select an access and mobility management function comprises determining whether the second network can serve the user equipment based on the globally unique mobility management entity identifier.
The method of claim 12, wherein determining whether the second network can serve the user equipment based on the globally unique mobility management entity comprises:

obtaining the identity of the second network from the globally unique mobility management entity identifier；

carrying out a domain name system lookup based on the identity of the second network；

receiving, in response to the lookup, a list of valid access and mobility management functions for the second radio access network； and

selecting the access and mobility management function from the list.
The method of claim 11, wherein receiving a globally unique temporary identifier from a user equipment comprises receiving, from the user equipment, an attach request message that includes the globally unique temporary identifier.
The method of claim 11 wherein receiving a globally unique temporary identifier from a user equipment comprises receiving, from the user equipment, a tracking area update message that includes the globally unique temporary identifier.
The method of claim 11, wherein the first radio access network is of a first radio access technology and the second radio access network is of a second radio access technology.
The method of claim 11, wherein the third radio access network is an untrusted network.
The method of claim 11, wherein the third radio access network is not part of the same public land mobile network as the first radio access network or the second radio access network.
A computing device configured to carry out the method of any one of claims 1 through 18.
A non-transitory, computer-readable medium having stored thereon computer executable instructions for carrying out an one of the methods of claims 1 through 18.